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Keywords:

  • Enterobacteriacea;
  • serotype;
  • O-antigen;
  • structure;
  • NMR;
  • database

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

Escherichia coli is usually a non-pathogenic member of the human colonic flora. However, certain strains have acquired virulence factors and may cause a variety of infections in humans and in animals. There are three clinical syndromes caused by E. coli: (i) sepsis/meningitis; (ii) urinary tract infection and (iii) diarrhoea. Furthermore the E. coli causing diarrhoea is divided into different ‘pathotypes’ depending on the type of disease, i.e. (i) enterotoxigenic; (ii) enteropathogenic; (iii) enteroinvasive; (iv) enterohaemorrhagic; (v) enteroaggregative and (vi) diffusely adherent. The serotyping of E. coli based on the somatic (O), flagellar (H) and capsular polysaccharide antigens (K) is used in epidemiology. The different antigens may be unique for a particular serogroup or antigenic determinants may be shared, resulting in cross-reactions with other serogroups of E. coli or even with other members of the family Enterobacteriacea. To establish the uniqueness of a particular serogroup or to identify the presence of common epitopes, a database of the structures of O-antigenic polysaccharides has been created. The E. coli database (ECODAB) contains structures, nuclear magnetic resonance chemical shifts and to some extent cross-reactivity relationships. All fields are searchable. A ranking is produced based on similarity, which facilitates rapid identification of strains that are difficult to serotype (if known) based on classical agglutinating methods. In addition, results pertinent to the biosynthesis of the repeating units of O-antigens are discussed. The ECODAB is accessible to the scientific community at http://www.casper.organ.su.se/ECODAB/.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

Escherichia coli is the type species of the genus Escherichia that contains mostly motile Gram-negative bacilli that fall within the family Enterobacteriaceae. It is the predominant facultative anaerobe of the human colonic flora. The organism typically colonizes the infant gastro-intestinal tract within hours after birth, and E. coli and the host derive mutual benefit for the rest of the host's life (Kaper et al., 2004). However, several E. coli clones have acquired specific virulence factors which increase their ability to adapt to new niches and allow them to cause a broad spectrum of diseases. Three general clinical syndromes can result from infection with pathogenic E. coli strains: enteric/diarrhoeal disease; urinary tract infection; and sepsis/meningitis (Nataro & Kaper, 1998). As long as these bacteria do not acquire genetic elements encoding for virulence factors, they remain benign commensals. Strains that acquire bacteriophage or plasmid DNA encoding enterotoxins or invasion factors become virulent. Among the E. coli causing intestinal diseases, there are six well-described pathotypes: enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enterohaemorrhagic E. coli (EHEC), enteroaggregative E. coli (EAEC) and diffusely adherent E. coli (DAEC) (Nataro & Kaper, 1998). These pathotypes have virulence attributes that help bacteria to cause diseases by different mechanisms.

Enteric/diarrhoeal Escherichia coli

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

Enteropathogenic Escherichia coli (EPEC)

Enteropathogenic Escherichia coli was the first pathotype of Escherichia coli to be described. Large outbreaks of infant diarrhoea in UK led Bray, in 1945, to describe a group of serologically distinct E. coli strains that were isolated from children with diarrhoea but not from healthy children (Kaper et al., 2004). The hallmark of infections due to EPEC is the attaching-and-effacing histopathology, which can be observed in intestinal biopsy specimens from patients or infected animals (Nataro & Kaper, 1998). The most prevalent serogroups within this group of E. coli are: O18ac, O20, O25, O26, O44, O55, O86, O91, O111, O114, O119, O125ac, O126, O127, O128, O142 and O158 (Nataro & Kaper, 1998).

Enteropathogenic Escherichia coli infection is primarily a disease of infants younger than 2 years (Nataro & Kaper, 1998). EPEC primarily causes acute diarrhoea, although many cases of persistent EPEC diarrhoea have been reported (Nataro & Kaper, 1998; Scaletsky et al., 1996). In addition to watery diarrhoea, vomiting and low-grade fever are common symptoms of EPEC infection. EPEC plays a more important role in developing countries where it is the foremost cause of diarrhoea. Many case-control studies have found EPEC to be more frequently isolated from children with diarrhoea than from the controls. Studies in Brazil, Mexico, and South Africa have shown that 30–40% of infant diarrhoea can be attributed to EPEC (Robins-Browne et al., 1980; Cravioto et al., 1988, 1990; Gomes et al., 1989, 1991). Recently, the pathogenesis of EPEC has been reviewed from the historical point of view and although the pathotype has been described in the 1940s, the exact mechanism of the disease is not completely understood (Chen & Frankel, 2005).

Enterotoxigenic Escherichia coli (ETEC)

Enterotoxigenic Escherichia coli is a common cause of infectious diarrhoea (Black, 1993), especially in tropical climates, where uncontaminated water is not readily available. Most of the illnesses, in terms of both numbers of cases and severity of symptoms, occur in infants and young children after weaning. This pathogen may express heat-labile and/or heat-stable toxins. Heat-labiles are a class of enterotoxins that are closely related in structure and function to cholera enterotoxin, which is expressed by Vibrio cholerae O1 and O139 (Sixma et al., 1993). The genes encoding heat-labile and heat-stable toxins are carried on plasmids. ETEC colonizes the surface of the small bowel mucosa and elaborates enterotoxins, which give rise to intestinal secretion. Colonization is mediated by one or more proteinaceous fimbrial or fimbrillar adhesins termed colonization factor antigens (CFA) (Kaper et al., 2004). A single plasmid often carries a toxin and CFA, for example, heat-stable toxin and CFA/I (Reis et al., 1980; McConnell et al., 1981; Murray et al., 1983), heat-labile and heat-stable toxins and CFA/II (Penaranda et al., 1983; Smith et al., 1983), and heat-stable toxin and CFA/IV (Thomas et al., 1987). The clinical features of ETEC diarrhoea are consistent with the pathogenic mechanism of ETEC enterotoxins. ETEC diarrhoea may be mild, brief, and self-limiting or may be as severe as that seen in V. cholerae infection (Levine et al., 1977; Wolf, 1997). The percentage of ETEC in children with diarrhoea varies from 10% to 30% (Albert et al., 1992; Mangia et al., 1993; Hoque et al., 1994; Flores Abuxapqui et al., 1999). Several studies suggest that 20–60% of travellers from developed countries experience diarrhoea when visiting the areas where ETEC infection is endemic; 20–40% of the cases are due to ETEC (Black, 1990; Arduino & DuPont, 1993; DuPont & Ericsson, 1993). The most common ETEC serogroups are: O6, O8, O11, O15, O20, O25, O27, O78, O128, O148, O149, O159 and O173.

Enteroinvasive Escherichia coli (EIEC)

Enteroinvasive Escherichia coli is a pathogenic form of E. coli that can cause dysentery (Nataro & Kaper, 1998). EIEC strains are biochemically, genetically and pathogenically closely related to Shigella spp. The precise pathogenic scheme of EIEC has yet to be elucidated. However, pathogenesis studies of EIEC suggest that its pathogenic features are virtually identical to those of Shigella spp. (Goldberg & Sansonetti, 1993; Parsot & Sansonetti, 1996). Genes necessary for invasiveness are carried on a 120-MDa plasmid in Shigella sonnei and a 140-MDa plasmid in other Shigella species and in EIEC (Baudry et al., 1987; Small & Falkow, 1988; Sasakawa et al., 1992). EIEC penetrates the intestinal mucosa, predominantly that lining the large intestine, to cause inflammation and mucosal ulceration that are characteristic of bacillary dysentery.

The most severe manifestation of infection with Shigella spp. and EIEC is bacillary dysentery, a syndrome characterized by frequent small-volume stools with blood and mucus. The disease is responsible for a substantial proportion of acute diarrhoeal diseases worldwide. However, most persons infected with Shigella spp. or EIEC experience watery diarrhoea that may or may not be followed by dysentery (Snyder et al., 1984; Nataro et al., 1998; Taylor et al., 1988). In most cases, EIEC elicits watery diarrhoea that is indistinguishable from that caused by other E. coli pathotypes (Nataro et al., 1998). EIEC can cause outbreaks of gastroenteritis. In sporadic cases, EIEC may be misidentified as Shigella spp. or non-pathogenic E. coli strains. EIEC outbreaks are usually food-borne or waterborne (Nataro et al., 1998). The most common EIEC serogroups are: O28ac, O29, O112ac, O124, O136, O143, O144, O152, O159, O164 and O167.

Enterohaemorrhagic Escherichia coli (EHEC)

Enterohaemorrhagic Escherichia coli is an etiological agent of diarrhoea with life-threatening complications. EHEC belongs to a group of E. coli called VTEC (‘verotoxigenic E. coli’ or ‘Vero cytotoxin-producing E. coli’) or STEC (‘Shiga toxin-producing E. coli’), formerly SLTEC (‘Shiga-like toxin producing E. coli’). It is believed that this pathotype adheres to the colon and distal small intestine; however, typical lesions have not been demonstrated (Kehl, 2002). The best-characterized adherence phenotype is the intimate or attaching and effacing adherence mediated by the eaeA gene. STEC isolates that possess the eaeA gene are capable of producing diarrhoea. However, the pathological lesions associated with haemorrhagic colitis and haemorrhagic uremic syndrome are due to the action of Shiga toxin (Stx) with endothelial cells. The term ‘enterohaemorrhagic E. coli’ (EHEC) was originally coined to denote strains that cause haemorrhagic colitis and haemorrhagic uremic syndrome, express Stx, cause attaching-and-effacing lesions on epithelial cells, and possess a c. 60-MDa plasmid (Levine & Edelman, 1984; Levine, 1987). Thus, EHEC denotes a subset of STEC. Whereas not all STEC strains are believed to be pathogens, all EHEC strains by the above definition are considered to be pathogens. EHEC can cause nonbloody diarrhoea, bloody diarrhoea, and haemorrhagic uremic syndrome in all age groups, but the young and the elderly are the most susceptible. The most notorious E. coli serotype associated with EHEC is O157:H7, which has been the cause of several large outbreaks of disease in North America, Europe and Japan (Boyce et al., 1995; Grimm et al., 1995; Kaper, 1998; Ozeki et al., 2003; Ezawa et al., 2004). The most common EHEC serogroups are: O4, O5, O16, O26, O46, O48, O55, O91, O98, O111ab, O113, O117, O118, O119, O125, O126, O128, O145, O157 and O172. Recently, several new EHEC serogroups have been described: O176, O177, O178, O179, O180 and O181 (Scheutz et al., 2004). In addition, many of the EHEC serogroups are also identified as EPEC.

Enteroaggregative Escherichia coli (EAEC)

Enteroaggregative Escherichia coli is defined as E. coli that do not secrete heat-labile or heat-stable enterotoxins and adhere to HEp-2 cells in an aggregative pattern (Nataro & Kaper, 1998; Nataro et al., 1998). The basic strategy of EAEC seems to comprise colonization of the intestinal mucosa, probably predominantly that of the colon, followed by secretion of enterotoxins and cytotoxins (Nataro et al., 1998). Studies on human intestinal specimens indicate that EAEC induces mild, but significant, mucosal damage (Hicks et al., 1996). The clinical features of EAEC diarrhoea are increasingly well defined in outbreaks, sporadic cases and the volunteer model. A growing number of studies have supported the association of EAEC with diarrhoea in developing countries, most prominently in association with persistent diarrhoea (Bhan et al., 1989a–c; Fang et al., 1995; Lima et al., 1992). Previous studies in children less than 5 years of age, all with diarrhoea or acute diarrhoea, have shown a significant difference in the EAEC prevalence compared to the controls (Nataro et al., 1987; Cravioto et al., 1991; Bhatnagar et al., 1993; Bouzari et al., 1994; Gonzalez et al., 1997). The increasing number of such reports and the rising proportion of diarrhoeal cases in which EAEC is implicated suggest that this pathotype is an important emerging agent of paediatric diarrhoea. The serogroups that have been identified within the EAEC group are O3, O7, O15, O44, O77, O86, O111, O126 and O127.

Diffusely adherent Escherichia coli (DAEC)

Diffusely adherent Escherichia coli is a category of E. coli that produces a diffuse adherence in the HEp-2 cell assay (Nataro et al., 1998). Little is known about the pathogenesis of DAEC. A surface of fimbria that mediates diffuse adherence phenotype has been cloned and characterized (Bilge et al., 1993a, b, 1989; Kerneis et al., 1991). The gene encoding the fimbria can be found on either the bacterial chromosome or a plasmid. Few epidemiological and clinical studies have been carried out to be able to describe adequately the epidemiology and clinical aspect of diarrhoea caused by DAEC. In one study, the patients with DAEC had watery diarrhoea without blood and faecal leukocytes (Poitrineau et al., 1995). The association of DAEC with diarrhoea has been shown in some studies (Giron et al., 1991; Jallat et al., 1993; Levine et al., 1993) but not in others (Gunzburg et al., 1993; Germani et al., 1996; Scaletsky et al., 2002).

Urinary tract infections

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

Uropathogenic Escherichia coli (UPEC)

The urinary tract is among the most common sites of bacterial infection and Escherichia coli is by far the most common infecting agent at this site. The subset of E. coli that causes uncomplicated cystitis and acute pyelonephritis is distinct from the commensal E. coli strains that make up most of the E. coli populating the lower colon of humans. E. coli from a small number of O serogroups – O4, O6, O14, O22, O75 and O83 – cause 75% of these urinary tract infections. Furthermore, they have phenotypes that are epidemiologically associated with cystitis and acute pyelonephritis in the normal urinary tract. Clonal groups and epidemic strains that are associated with urinary tract infections have been identified (Phillips et al., 1988; Manges et al., 2001). Although many urinary tract infection isolates seem to be clonal, there is no single phenotypic profile that causes urinary tract infections. Specific adhesins, including P (Pap), type 1 and other fimbriae, seem to aid in colonization (Phillips et al., 1988; Nowicki et al., 1989; Johnson, 1991; Manges et al., 2001).

Sepsis/meningitis

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

Meningitis/sepsis associated Escherichia coli (MNEC)

This Echerichia coli pathotype is the most common cause of Gram-negative neonatal meningitis, with a case fatality rate of 15–40% and severe neurological defects in many of the survivors (Unhanand et al., 1993; Dawson et al., 1999). A majority (80%) of the E. coli strains that cause meningitis possess the K1 capsular polysaccharide.

Other potential Escherichia coli pathotypes

Several other potential E. coli pathotypes have been described, but none of these is as well established as the pathotypes described above. Among the most intriguing of these potential pathogens are strains of E. coli that are associated with Crohn's disease and are known as adherent-invasive E. coli (Darfeuille-Michaud, 2002). An inflammatory process and necrosis of the intestinal epithelium are characteristics of necrotizing enterocolitis (NEC), an important cause of mortality and long-term morbidity in pre-term infants. Necrotoxic E. coli (NTEC) have been associated with disease in both humans and animals (De Rycke et al., 1999). The relationships among the NEC-associated strains, NTEC and strains associated with Crohn's disease have not yet been clearly established. A poorly characterized subset of E. coli infections outside the gastrointestinal or urinary tract is a group implicated in intra-abdominal infections, including abscesses, wounds, appendicitis and peritonitis.

Typing of Escherichia coli

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

There have been several available assays to identify different categories of diarrhoeagenic Escherichia coli. Isolation and identification of E. coli based on the biochemical properties are widely used in most microbiological laboratories as they do not require sophisticated equipment or complicated protocols. E. coli can be easily recovered from clinical samples on general or selective media at 37°C under aerobic conditions. E. coli are usually identified by biochemical reactions. In general, the different pathotypes cannot be identified based on biochemical criteria alone, as in most cases they are indistinguishable from non-pathogenic E. coli.

In addition to the biochemical tests, serology is commonly used. It is based on Kauffmann's scheme for the serologic classification of E. coli, which is extensively reviewed in (Orskov & Orskov, 1984; Ewing, 1986). Serotyping E. coli is performed on the basis of their O (somatic), H (flagellar), and K (capsular) surface antigen profile. More than 180 O, 60 H, and 80 K antigens have been proposed (Whitfield & Roberts, 1999; Robins-Browne & Hartland, 2002). Each O antigen defines a serogroup. E. coli of specific serogroups can be associated with certain clinical syndromes (Nataro & Kaper, 1998; Campos et al., 2004). A specific combination of O and H antigens defines the ‘serotype’ of an isolate. One pathotype can comprise several serogroups and one serogroup may belong to several pathotypes and even to non-pathogenic E. coli (Nataro & Kaper, 1998; Campos et al., 2004). Due to the limited sensitivity and specificity, and the various combinations of antigens, serotyping is tedious and expensive and is performed reliably only by a small number of reference laboratories.

Among the most useful methods to diagnose different pathotypes of E. coli are phenotypic assays, which are based on the virulence characteristics. Of them, the HEp-2 adherence assay is useful to identify the adherence patterns of diarrhoeagenic E. coli. It remains the ‘gold standard’ for the diagnosis of EAEC and DAEC (Vial et al., 1990; Nataro et al., 1998; Donnenberg & Nataro, 1995). Identification of ETEC has relied on the detection of heat-labile and/or heat-stable enterotoxins. The classical phenotypic assay for EIEC identification is the Sereny (guinea pig keratoconjunctivitis) test, which correlates with the ability of the strain to invade epithelial cells and spread from cell to cell (Kopecko, 1994).

Molecular genetic methods remain the most popular and most reliable techniques for differentiating pathogenic strains from non-pathogenic members. The assays are based on nucleic acid probes and PCR and have been extensively used. The advantages of PCR include its high sensitivity in detection of target templates and both rapid and reliable results due to its high specificity (Schultsz et al., 1994; Ramotar et al., 1995; Stacy-Phipps et al., 1995; Kai et al., 2000; Dutta et al., 2001; Pulz et al., 2003; Gioffre et al., 2004).

Shigellae

Shigellae are Gram-negative, non-motile, facultative anaerobic rods. Shigella are differentiated from the closely related E. coli on the basis of pathogenicity, physiology (failure to ferment lactose or decarboxylate lysine) and serology (Samuel, 1996). The genus is divided into four species with multiple serotypes: Shigella dysenteriae (12 serotypes), Shigella flexneri (6 serotypes), Shigella boydii (18 serotypes) and S. sonnei (1 serotype) (Samuel, 1996). Shigella enterotoxin 1 (ShET1) is found in S. flexneri 2a, but it is only occasionally found in other serotypes. In contrast, ShET2 is more widespread and detectable in 80% of Shigella representing all four species. Shigella dysenteriae serotype 1 expresses Shiga toxin, an extremely potent, ricin-like cytotoxin that inhibits protein synthesis in susceptible mammalian cells. This toxin also has enterotoxic activity in rabbit ileal loops, but its role in human diarrhoea is unclear. Shiga toxin is associated with haemorrhagic uremic syndrome, a complication of infections with S. dysenteriae serotype 1. Closely related toxins are expressed by EHEC strains including the potentially lethal, food-borne O157:H7 serotype (Samuel, 1996).

The four Shigella species cause varying degrees of dysentery, characterized by fever, abdominal cramps and diarrhoea containing blood and mucous. Shigellosis is endemic in developing countries where sanitation is poor. In developed countries, single-source, food or water-borne outbreaks occur sporadically, and pockets of endemic shigellosis can be found in institutions and in remote areas with substandard sanitary facilities. Isolation and identification of Shigella spp. is usually based on culture, biochemical tests, and serotyping. Molecular methods can be used to determine some target genes.

Lipopolysaccharide

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

Lipopolysaccharide (LPS), also known as endotoxin, is anchored in the outer membrane of the Gram-negative bacterium. It consists of three parts: lipid A, which is the toxic component; the core region, which can be divided into an inner and an outer part; and finally the O-antigen polysaccharide, which is specific for each serogroup (Fig. 1) (Brade et al., 1999). The sugar residues in lipid A and the core region are decorated to a varying extent with phosphate groups or phosphodiester-linked derivatives, which ensures microheterogeneity in each strain. The lipid A part is highly conserved in Escherichia coli. The core, however, contains five different basic structures, denoted R1 to R4 and K12. The O-polysaccharide is linked to a sugar in the outer core. The O-antigen usually consists of 10–25 repeating units containing two to seven sugar residues. Thus, the molecular mass of the LPS present in smooth strains will be up to ∼25 kDa.

image

Figure 1.  Schematic structure of an enterobacterial lipopolysaccharide molecule. The lipids are depicted by curved lines and the sugar residues are as follows: GlcN (▪), Kdo (▾), heptose (▴), hexose (◆), and O-antigen components (•), most commonly hexose.

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The present scheme of E. coli O-antigens comprises O1 to O181. The following O groups have been removed: O31, O47, O67, O72, O93, O94 and O122. The O93 strain, however, will probably be re-introduced (Scheutz et al., 2004). Escherichia coli strain 73-1 has been typed as E. coli O73:K−:H33 and strain 62D1 was suggested to belong to the genus Erwinia herbicola (Scheutz, 2004). In several cases the O-antigens of E. coli are identical or nearly identical to those of other bacteria (Table 1).

Table 1. Escherichia coli O-antigens identical or nearly identical to other bacterial polysaccharides
SerogroupIdentical toRef.
O8Klebsiella pneumoniae O5Jansson et al. (1985)
 Serratia marcescens S3255Aucken & Pitt (1991)
O9Hafnia alvei PCM 1223Katzenellenbogen et al. (2001)
 Klebsiella pneumoniae O3Prehm et al. (1976)
O18Serratia marcescens O8Oxley & Wilkinson (1986)
O21Hafnia alvei O39Staaf et al. (1999a)
O35Salmonella enterica O62Rundlöf et al. (1998)
O55Salmonella enterica O50Kenne et al. (1983b)
O58Shigella dysenteriae type 5Dmitriev et al. (1977)
O97Yersinia enterocolitica O5,27Perry & MacLean (1987)
O98Yersinia enterocolitica O11,24Marsden et al. (1994)
O104Escherichia coli K9Gamian et al. (1992)
O105Shigella boydii type 11L'vov et al. (1991)
O111Salmonella enterica O:35Kenne et al. (1983b)
O121Shigella dysenteriae type 7Parolis et al. (1997)
O124Shigella dysenteriae type 3Dmitriev et al. (1976)
O143Shigella boydii type 8Landersjöet al. (1996)
O147Shigella flexneri type 6Hygge Blackeman et al. (1998)
O157Citrobacter sedlakii NRCC 46070Vinogradov et al. (2000)
 Citrobacter freundii F90Bettelheim et al. (1993)
 Citrobacter freundii OCU158Nishiuchi et al. (2000, 2002)
 Salmonella enterica O30Bundle et al. (1986)

Structural determination of O-antigens from strains that are difficult to type or of nontyped strains

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

The serotyping of clinical isolates of Escherichia coli is under constant development and usually it is possible to identify the isolated strains. In some cases, however, it is not possible properly to characterize the strain with available monospecific polyclonal antisera, either due to auto agglutination or because the isolated E. coli strain is novel and appropriate antisera have not been raised. Under such circumstances it is of great interest to have a procedure that rapidly could indicate, independently of immunological tests, the serotype of the isolated strain.

Since immunochemical tests require cultivation of the strain, we obtain sufficient material for analysis by other methods.

Nuclear magnetic resonance spectroscopy is a powerful tool that is used for studying biomolecules, including bacterial polysaccharides. In structural studies of these polysaccharides, NMR signals from the polymers may be observed from live bacteria preparations or of the extracted LPS. In the structural determination of the O-antigen polysaccharide part of an LPS, the O-polysaccharide is often released from the lipid A part by treatment with dilute acid and purified by gel permeation chromatography. These steps are laborious and should be omitted, in particular, if only typing of the strain is required.

As it is easy to perform the phenol-water extraction from the cultivated bacterial isolates to obtain LPS, we focus on a procedure that rapidly can identify the most probable O-antigenic formula from a crude LPS preparation. A 1H NMR spectrum of the LPS in D2O can be obtained in a few minutes. Such a spectrum contains a number of characteristic signals, even though most of them are not resolved (Fig. 2). To utilize the information contained in a 1H NMR spectrum, a database with the structures of the E. coli O-antigen polysaccharides was implemented. Each structure has published NMR data associated with it as well as described cross-reactivity when present. Links to the original publications are also provided in the web-based implementation. In the following approach we often enter sugar components of the O-polysaccharide as some or all can be determined in a few hours by chemical derivatization and analysis with gas-liquid chromatography/mass spectrometry (GLC-MS), high performance liquid chromatography (HPLC) or electrophoresis techniques from a hydrolysate of the polymer, where the choice of technique for practical reasons is the one used in each investigator's laboratory.

image

Figure 2. 1H nuclear magnetic resonance spectrum of the lipopolysaccharide from Escherichia coli strain 97RN in D2O solution.

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We will now exemplify the approach by analysis of E. coli isolates that were not possible to serotype. Two clinical isolates of E. coli from children with diarrhoea in León, Nicaragua, termed strains 97RN and 121RN, showed identical 1H NMR spectra (cf. Fig. 2) and contained glucose, galactose and glucosamine according to GLC analysis. These sugar components together with selected 1H NMR data were entered to the web-based search interface, which then selects a best fit to the records in the database. The results of this search gave a close match to the O-antigen structure of E. coli O21 (and E. coli strain 105). Further inspection and comparison of NMR data confirmed the identity between the strains. Thus, the procedure rapidly revealed the serogroup of these two strains and no further structural investigation was necessary.

Biosynthesis considerations

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

The biosynthesis of an LPS molecule and its transport to the outer membrane of Gram-negative bacteria depend on several complex events taking place at different locations in the bacterium (Raetz & Whitfield, 2002; Samuel & Reeves, 2003). For the synthesis of the O-chain part, two of the three reported pathways are present in Escherichia coli, namely, the Wzy-polymerase-dependent pathway present in most cases and typical for heteropolysaccharides and the ABC-transporter-dependent pathway, typical for homopolymers. Once the nucleotide sugars have been synthesized they can be incorporated into the growing O-chain. In the Wzy-dependent pathway a glycosyl-1-phosphoryl residue is transferred to an undecaprenyl phosphate acceptor to form an undecaprenyl-PP-sugar intermediate. Subsequent transfer of additional sugars to this acceptor results in an undecaprenyl-PP-oligosaccharide intermediate in which the sequence of sugars is related to the biological repeating unit to be formed in the O-chain. Translocation of this intermediate occurs from the cytoplasmic side of the membrane to the periplasmic side in a Wzx-dependent process. The Wzy-dependent polymerization of the O-antigen occurs at the reducing end of the nascent chain being formed, meaning that the O-chain on the undecaprenol-PP carrier is transferred to the most recently synthesized undecaprenol-PP-oligosaccharide. The extent of polymerization, i.e. the chain-length modality, is determined by the Wzz product. The action of the Wzy-polymerase from a linear undecaprenol-PP-oligosaccharide to produce a branched structure with a side-chain offers several possibilities just at this step to produce different structures with regard to anomeric configuration, linkage position and sugar residue.

The ABC-transporter pathway utilizes the β-d-GlcNAc-PP-undecaprenol entity as a primer for the chain elongation taking place on the cytoplasmic side of the membrane. In E. coli O9, a homopolymer of mannose, an adaptor (α-d-Man) is (1[RIGHTWARDS ARROW]3)-linked to the N-acetylglucosamine residue. Subsequent chain growth occurs by processive glycosyl transfer to the non-reducing terminus. In E. coli O8, also a homopolymer of mannose, the O-chain is terminated by a 3-O-methyl-d-Man residue. Although the sugars are added one by one, sodium dodecyl sulphate-polyacrylamide electrophoresis (SDS-PAGE) analysis of these LPS molecules reveal distributions of distinct bands. It is therefore reasonable to describe, also in this case, the repeating units of the O-chain in the context of biological repeating units. The undecaprenyl-linked polymer depends on Wzm and Wzt for transfer to the periplasmic face of the membrane. For both these pathways the O-chain-PP-undecaprenyl entity is ligated to the Lipid A-core acceptor and subsequently translated to the outer membrane.

In Shigella flexneri the O-antigens have different structures as a result of acquisition of genetic material from bacteriophages via transduction (Lerouge & Vanderleyden, 2001). The glucosyl residues, present as side-chains in the repeating unit, are proposed to be transferred to the growing O-antigen chain on the periplasmic side of the membrane. A similar pathway could be possible for some of the E. coli O-antigens, as indicated by their substituent sugars and their location within the repeating unit of the polymer (vide infra).

We also note that a gene has been identified for a glucosylphosphate transferase, which then is responsible for the formation of the phosphodiester-linked glycosyl residue within the repeating unit of the O-antigen of E. coli O172 (Guo et al., 2004). Thus, this finding indicates that the ‘phospho-sugar’ is transferred en bloc in the biosynthesis.

O-antigen repeating units: characteristics and statistics of the structures

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

In humans, only a handful of different sugar residues are utilized in most glycoconjugates such as glycolipids and glycoproteins (Varki et al., 1999). In bacteria, however, a large number of different sugars are found and the O-antigens of Escherichia coli contain a great variety of them (Table 2). In addition, a number of unusual sugars are found in these polymers (Scheme 1), including pentoses, deoxyhexoses, lactyl substituted hexoses, heptoses and nonuloses. The number of sugar residues in the O-antigen repeating unit ranges from two to seven and the topology of the repeats may be described as linear, branched or double branched. We have analysed the topology based on the number of sugar residues in the backbone (Table 3). By far, the most common topology contains four sugars in the backbone being linear or containing a single terminal residue in the side-chain. The 3- and 5-residue backbones are also common, whereas the 2- and 6-residue backbones are only present in a few cases.

Table 2.   Abundance of glycosyl residues in Escherichia coli O-antigens
SugarAnomers*Sidechains
α+βαβAnyTerminalInternal§
  • *

    In percent of 361 residues.

  • Abundance in any sidechain. Percent of 50 residues.

  • Abundance in sidechains in which the glycosyl group is directly linked to a branch-point residue, which itself is adjacent to and substituted by a 2-acetamido-d-hexose. Percent of 24 residues.

  • §

    Abundance in side chains not included in footnote ‡. Percent of 26 residues.

  • 0, not found; < 1, less than 1%.

  • All remaining residues that occur fewer than three times.

Colp1106130
l-Fucp33<110138
l-FucpNAc220   
d-Glcp1173322538
d-GlcpA2<12240
d-GlcpNAc197138015
d-Galf2<12240
d-Galp1267181323
d-GalpA211   
d-GalpNAc1385   
d-GalpNAcA110   
d-Manp1064402
Neu5Ac110   
d-Quip3NAc1<11   
d-Quip4NAc101   
l-Rhap1210212214
d-Ribf101240
l-6dTalp110240
Other532484
image

Figure Scheme 1..  Unusual glycosyl residues in Escherichia coli O-antigens.

Download figure to PowerPoint

Table 3.   Topology of the O-antigen repeating units
TopologyAbundance (%)
2-residue backbone5
inline image3
inline image1
inline image1
3-residue backbone27
inline image6
inline image8
inline image3
inline image7
inline image3
4-residue backbone52
inline image22
inline image27
inline image2
inline image1
5-residue backbone15
inline image11
inline image4
6-residue backbone1
inline image1

Each sugar residue is found in either the α- or the β-configuration at the anomeric centre. The common sugars (including ring form) of E. coli O-antigens, viz., d-Glcp, d-GlcpNAc, d-Galp, d-GalpNAc, d-Manp, and l-Rhap are all found with both anomeric configurations. Other sugars, e.g. l-FucpNAc or d-Quip4NAc, have hitherto only been found in one of the anomeric configurations, namely the α- or the β-configuration, respectively. Some of the sugars in the side-chains are present only as nonterminal residues, e.g. d-GlcpNAc, whereas others are only found at a terminal position in the biological repeating unit, e.g. Colp. The unusual groups are then highly accessible and consequently specific for that particular E. coli serogroup.

The O-antigens synthesized by the ABC-transporter-dependent pathway (see above) or herein tentatively assigned to that pathway are homopolymers or have only two sugar residues in the backbone of the repeating unit (Table 4). In 1994 it was shown that in E. coli O7 (Table 5), having a Wzy-dependent pathway, the repeating unit of the O-antigen had an N-acetylglucosamine residue at its reducing end (Alexander & Valvano, 1994) and the authors proposed that this pattern should also be found in other O-antigen structures. By arranging the E. coli O-antigen structures hitherto determined (Tables 5 and 6) with the d-GlcNAc residue at the reducing end one readily observes that this pattern is quite reasonable. In cases when d-GlcNAc is not present in the polymer, d-GalNAc takes its place, in agreement with the observation that WecA can transfer either of the N-acetylhexosamine sugars (Marolda et al., 2004). In several of the O-antigens both amino sugars are components of the repeating unit. In just two strains, d-FucNAc has been found and is expected to be the sugar at the reducing end of the repeating unit. As noted above, one of these, strain 62D1, was recently identified as a non-E. coli species. In all but a few cases it is possible to identify that the amino sugar at the reducing end is 3-substituted. The other cases being the O1A, O2 and possibly O149 antigens, where d-GlcNAc is 4-substituted by a β-l-Rhap residue, or in O83 and O136, where it is substituted by a β-d-Galp residue, i.e. the structural element is N-acetyl-lactosamine. These results are in good agreement with the few examples when the biological repeating unit has been determined by NMR spectroscopy, e.g. in semi-rough type of LPS containing only one repeating unit as for E. coli O6 (Grozdanov et al., 2002). The biological repeating unit has also been determined on medium-sized O-antigens with a degree of polymerization of ∼13 for E. coli O126 and ∼10 for E. coli O91 (Larsson et al., 2004; Lycknert & Widmalm, 2004). The three-substituted d-GlcNAc residue was present in these three O-polysaccharides at the reducing end of the repeating unit.

Table 4.   O-antigens synthesised by the ABC-transporter-dependent pathway
SerogroupStructureRef.
  • *

    Biosynthetic pathway proven experimentally.

  • β-d-6dmanHep2Ac is 2-O-acetyl-6-deoxy-β-d-manno-heptopyranosyl.

  • β-d-Xulf is β-d-threo-pentofuranosyl.

O8*[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]3)-β-d-Man-(1[RIGHTWARDS ARROW]Jansson et al. (1985)
O9a*[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-Man-(1[RIGHTWARDS ARROW]Parolis et al. (1986)
O9*[RIGHTWARDS ARROW]2)-[α-d-Man-(1[RIGHTWARDS ARROW]2)]2-α-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-Man-(1[RIGHTWARDS ARROW]Prehm et al. (1976)
O20ab[RIGHTWARDS ARROW]2)-β-d-Ribf-(1[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]Vasil'ev & Zakharova (1976)
O20acα-d-Gal-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]2)-β-d-Ribf-(1[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]Vasil'ev & Zakharova (1982)
O52*[RIGHTWARDS ARROW]3)-β-d-Fucf-(1[RIGHTWARDS ARROW]3)-β-d-6dmanHep2Ac-(1[RIGHTWARDS ARROW]Feng et al. (2004a)
O97[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-β-l-Rha-(1[RIGHTWARDS ARROW] || β-d-Xulf-(2[RIGHTWARDS ARROW]2)β-d-Xulf-(2[RIGHTWARDS ARROW]2)Perry & MacLean (1987)
O101[RIGHTWARDS ARROW]6)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]4)-α-d-GalNAc-(1[RIGHTWARDS ARROW]Staaf et al. (1997)
Table 5.   O-antigens synthesised by the polymerase-dependent pathway with four or less residues in the backbone
SerogroupStructureRef.
O1A, O1A1[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-β-l-Rha-(1[RIGHTWARDS ARROW]4)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-ManNAc-(1[RIGHTWARDS ARROW]2)Baumann et al. (1991) Jann et al. (1992b)
O1B[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]|β-d-ManNAc-(1[RIGHTWARDS ARROW]2)Gupta et al. (1992)
O1C[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]|β-d-ManNAc-(1[RIGHTWARDS ARROW]2)Gupta et al. (1992)
O2[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-β-l-Rha-(1[RIGHTWARDS ARROW]4)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | α-d-Fuc3NAc-(1[RIGHTWARDS ARROW]2)Jansson et al. (1987a)
O3β-l-RhaNAc(1[RIGHTWARDS ARROW]4)α-d-Glc-(1[RIGHTWARDS ARROW]4)| | [RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Medina et al. (1994)
O4:K52[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-FucNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc(1[RIGHTWARDS ARROW]Jann et al. (1993)
O4:K6α-d-Glc-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-FucNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc(1[RIGHTWARDS ARROW]Jann et al. (1993)
O5ab[RIGHTWARDS ARROW]4)-β-d-Qui3NAc-(1[RIGHTWARDS ARROW]3)-β-d-Ribf-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc(1[RIGHTWARDS ARROW]MacLean & Perry (1997)
O5ac (strain 180/C3)[RIGHTWARDS ARROW]2)-β-d-Qui3NAc-(1[RIGHTWARDS ARROW]3)-β-d-Ribf-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc(1[RIGHTWARDS ARROW]Urbina et al. (2005)
O6:K2; K13; K15[RIGHTWARDS ARROW]4)-α-d-GalNAc-(1[RIGHTWARDS ARROW]3)-β-d-Man-(1[RIGHTWARDS ARROW]4)-β-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-Glc-(1[RIGHTWARDS ARROW]2)Jansson et al. (1984)
O6:K54[RIGHTWARDS ARROW]4)-α-d-GalNAc-(1[RIGHTWARDS ARROW]3)-β-d-Man-(1[RIGHTWARDS ARROW]4)-β-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]|β-d-GlcNAc-(1[RIGHTWARDS ARROW]2)Jann et al. (1994c)
O7α-l-Rha-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]3)-β-d-Qui4NAc-(1[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]L'vov et al. (1984)
O10[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | α-d-Fuc4NAcyl-(1[RIGHTWARDS ARROW]2) Acyl=acetyl (60%) or (R)-3-hydroxybutyryl (40%)Kenne et al. (1986)
O16[RIGHTWARDS ARROW]2)-β-d-Galf-(1[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-Rha2Ac-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]Jann et al. (1994b)
O17α-d-Glc-(1[RIGHTWARDS ARROW]6) | [RIGHTWARDS ARROW]6)-α-d-Man-(1[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]2)-β-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc(1[RIGHTWARDS ARROW]Masoud & Perry (1996)
O18A, O18ac[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-GlcNAc-(1[RIGHTWARDS ARROW]3)Jansson et al. (1989)
O18A1α-d-Glc-(1[RIGHTWARDS ARROW]6) | [RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-GlcNAc-(1[RIGHTWARDS ARROW]3)Jann et al. (1992a)
O18B[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-Glc-(1[RIGHTWARDS ARROW]3)Jann et al. (1992a)
O18B1α-d-Glc-(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-Glc-(1[RIGHTWARDS ARROW]3)Jann et al. (1992a)
O21β-d-Gal-(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]3)-β-d-Gal-(1[RIGHTWARDS ARROW]4)-β-d-Glc-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW] | β-d-GlcNAc-(1[RIGHTWARDS ARROW]2)Staaf et al. (1999a)
O23Aα-d-Glc-(1[RIGHTWARDS ARROW]6) | [RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-GlcNAc(1[RIGHTWARDS ARROW]3)Bartelt et al. (1993)
O24[RIGHTWARDS ARROW]7)-α-Neu5Ac-(2[RIGHTWARDS ARROW]3)-β-d-Glc-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW] | α-d-Glc-(1[RIGHTWARDS ARROW]2)Torgov et al. (1995)
O25β-d-Glc-(1[RIGHTWARDS ARROW]6) | [RIGHTWARDS ARROW]4)-α-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-FucNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | α-l-Rha-(1[RIGHTWARDS ARROW]3)Kenne et al. (1983a)
O26[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]4)-α-l-FucNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Manca et al. (1996)
O28[RIGHTWARDS ARROW]2)-(R)-Gro-1-P[RIGHTWARDS ARROW]4)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]3)-β-d-Galf2Ac-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]Rundlöf et al. (1996)
O44α-d-Glc-(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]6)-α-d-Man-(1[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]2)-β-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc(1[RIGHTWARDS ARROW]Staaf et al. (1995)
O45[RIGHTWARDS ARROW]2)-β-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-6dTal2Ac-(1[RIGHTWARDS ARROW]3)-α-d-FucNAc-(1[RIGHTWARDS ARROW]Jann et al. (1995)
O45rel[RIGHTWARDS ARROW]2)-β-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-6dTal2Ac-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Jann et al. (1995)
O55[RIGHTWARDS ARROW]6)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW] | α-Col-(1[RIGHTWARDS ARROW]2)-β-d-Gal-(1[RIGHTWARDS ARROW]3)Lindberg et al. (1981)
O56[RIGHTWARDS ARROW]7)-α-Neu5Ac-(2[RIGHTWARDS ARROW]3)-β-d-Glc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | α-d-Gal-(1[RIGHTWARDS ARROW]2)Gamian et al. (1994)
O583-O-[(R)-1-carboxyethyl]-α-l-Rha -(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]4)-α-d-Man-(1[RIGHTWARDS ARROW]4)-α-d-Man2Ac-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Dmitriev et al. (1977)
O64β-d-Gal-(1[RIGHTWARDS ARROW]6) | [RIGHTWARDS ARROW]3)-α-d-ManNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcA-(1[RIGHTWARDS ARROW]3)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc(1[RIGHTWARDS ARROW]Perry et al. (1993)
O69[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Erbing et al. (1977)
O73 (Strain 73-1)α-d-Glc-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]4)-α-d-Man-(1[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]2)-β-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc(1[RIGHTWARDS ARROW]Weintraub et al. (1993)
O75β-d-Man-(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]4)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Erbing et al. (1978)
O77[RIGHTWARDS ARROW]6)-α-d-Man-(1[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]2)-β-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc(1[RIGHTWARDS ARROW]Yildirim et al. (2001)
O78[RIGHTWARDS ARROW]4)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]4)-β-d-Man-(1[RIGHTWARDS ARROW]4)-α-d-Man-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Jansson et al. (1987b)
O86α-d-Gal-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]4)-α-l-Fuc-(1[RIGHTWARDS ARROW]2)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]Andersson et al. (1989)
O88α-l-6dTal-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]4)-α-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-Man-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Torgov et al. (1996)
O90[RIGHTWARDS ARROW]4)-α-l-Fuc2/3Ac-(1[RIGHTWARDS ARROW]2)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]Ratnayake et al. (1994b)
O98[RIGHTWARDS ARROW]3)-α-l-QuiNAc-(1[RIGHTWARDS ARROW]4)-α-d-GalNAcA-(1[RIGHTWARDS ARROW]3)-α-l-QuiNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Marsden et al. (1994)
O104[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]4)-α-Neu5,7,9Ac3-(2[RIGHTWARDS ARROW]3)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]Gamian et al. (1992)
O111α-Col-(1[RIGHTWARDS ARROW]6) | [RIGHTWARDS ARROW]4)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | α-Col-(1[RIGHTWARDS ARROW]3)Eklund et al. (1978)
O113[RIGHTWARDS ARROW]4)-α-d-GalNAc-(1[RIGHTWARDS ARROW]4)-α-d-GalA-(1[RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-Gal-(1[RIGHTWARDS ARROW]3)Parolis & Parolis (1995)
O114[RIGHTWARDS ARROW]4)-β-d-Qui3N(N-acetyl-l-seryl)-(1[RIGHTWARDS ARROW]3)-β-d-Ribf-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc(1[RIGHTWARDS ARROW]Dmitriev et al. (1983)
O119β-d-RhaNAc3NFo-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]2)-β-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]4)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]Anderson et al. (1992)
O121[RIGHTWARDS ARROW]3)-β-d-Qui4N(N-acetyl-glycyl)-(1[RIGHTWARDS ARROW]4)-α-d-GalNAc3AcA6N-(1[RIGHTWARDS ARROW]4)-α-d-GalNAcA-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]Parolis et al. (1997)
O1244-O-[(R)-1-carboxyethyl]-β-d-Glc-(1[RIGHTWARDS ARROW]6)-α-d-Glc(1[RIGHTWARDS ARROW]4) |[RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]6)-β-d-Galf-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]Dmitriev et al. (1976)
O125α-d-Glc-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]4)-β-d-GalNAc-(1[RIGHTWARDS ARROW]2)-α-d-Man-(1[RIGHTWARDS ARROW]3)-α-l-Fuc-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW] | β-d-Gal-(1[RIGHTWARDS ARROW]3)Kjellberg et al. (1996)
O126[RIGHTWARDS ARROW]2)-β-d-Man-(1[RIGHTWARDS ARROW]3)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | α-l-Fuc-(1[RIGHTWARDS ARROW]2)Larsson et al. (2004)
O127[RIGHTWARDS ARROW]2)-α-l-Fuc-(1[RIGHTWARDS ARROW]2)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]Widmalm & Leontein, (1993)
O128α-l-Fuc-(1[RIGHTWARDS ARROW]2) | [RIGHTWARDS ARROW]6)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]4)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]Sengupta et al. (1995)
O136[RIGHTWARDS ARROW]4)-β-Pse5Ac7Ac-(2[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]4)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]β-Pse5Ac7Ac=5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-β-l-manno-nonulosonic acidStaaf et al. (1999c)
O138[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]4)-α-d-GalNAcA-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Linnerborg et al. (1997a)
O141α-l-Rha-(1[RIGHTWARDS ARROW]3) |[RIGHTWARDS ARROW]4)-α-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-Man6Ac-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | β-d-GlcA-(1[RIGHTWARDS ARROW]2)Färnbäck et al. (1998)
O142[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]6)-α-d-GalNAc-(1[RIGHTWARDS ARROW]4)-α-d-GalNAc-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW] | β-d-GlcNAc-(1[RIGHTWARDS ARROW]3)Landersjöet al. (1997)
O143[RIGHTWARDS ARROW]2)-β-d-GalA6R3,4Ac-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]4)-β-d-GlcA-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] R=1,3-dihydroxy-2-propylaminoLandersjöet al. (1996)
O147[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]4)-β-d-GalA-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]Hygge Blackeman et al. (1998)
O149[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(S)-4,6Py-(1[RIGHTWARDS ARROW]3)-β-l-Rha-(1[RIGHTWARDS ARROW]4)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] (S)-4,6Py=4,6-O-[(S)-1-carboxyethylidene]-Adeyeye et al. (1988)
O152β-l-Rha-(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1-P[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]2)-β-d-Glc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Olsson et al. (2005)
O157[RIGHTWARDS ARROW]2)-α-d-Rha4NAc-(1[RIGHTWARDS ARROW]3)-α-l-Fuc-(1[RIGHTWARDS ARROW]4)-β-d-Glc-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]Perry et al. (1986)Nishiuchi et al. (2002) Datta et al. (1999)
O158α-d-Glc-(1[RIGHTWARDS ARROW]6) | [RIGHTWARDS ARROW]4)-α-d-Glc-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW] | α-l-Rha-(1[RIGHTWARDS ARROW]3)Nishiuchi et al. (2000)
O159α-l-Fuc-(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]4)-α-d-GalA-(1[RIGHTWARDS ARROW]3)-α-l-Fuc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Linnerborg et al. (1999c)
O164β-d-Glc-(1[RIGHTWARDS ARROW]6)-α-d-Glc(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]3)-β-d-Gal-(1[RIGHTWARDS ARROW]6)-β-d-Galf-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]Linnerborg et al. (1999a)
O173α-l-Fuc-(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]3)-α-d-Glc-(1-P[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]2)-β-d-Glc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Linnerborg et al. (1999b)
62D1α-d-Gal(1[RIGHTWARDS ARROW]6) | [RIGHTWARDS ARROW]2)-β-d-Qui3NAc-(1[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-FucNAc-(1[RIGHTWARDS ARROW] Suggested as Erwinia herbicolaStaaf et al. (1999b)
Table 6.   O-antigens synthesized by the polymerase-dependent pathway with five or six residues in the backbone
SerogroupStructureRef.
O22[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-β-d-GlcA-(1[RIGHTWARDS ARROW]4)-β-d-GalNAc3Ac-(1[RIGHTWARDS ARROW]3)-α-d-Gal-(1[RIGHTWARDS ARROW]3)-β-d-GalNAc-(1[RIGHTWARDS ARROW]Bartelt et al. (1994)
O35[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] | α-d-GalNAcA6N-(1[RIGHTWARDS ARROW]2)Rundlöf et al. (1998)
O65[RIGHTWARDS ARROW]2)-β-d-Qui3NAc-(1[RIGHTWARDS ARROW]4)-α-d-GalA6N-(1[RIGHTWARDS ARROW]4)-α-d-GalNAc-(1[RIGHTWARDS ARROW]4)-β-d-GalA-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]Perry & MacLean (1999)
O66[RIGHTWARDS ARROW]2)-β-d-Man-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]2)-β-d-Glc3Ac-(1[RIGHTWARDS ARROW]3)-α-l-6dTal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc(1[RIGHTWARDS ARROW]Jann et al. (1995)
O83[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-β-d-GlcA-(1[RIGHTWARDS ARROW]6)-β-d-Gal-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]4)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Jann et al. (1994a)
O91[RIGHTWARDS ARROW]4)-α-d-Qui3NAcyl-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]4)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]4)-β-d-GlcA6NGly-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW] Acyl=(R)-3-hydroxybutyrylKjellberg et al. (1999)
O105β-d-Ribf-(1[RIGHTWARDS ARROW]3) |[RIGHTWARDS ARROW]4)-α-d-GlcA2Ac3Ac-(1[RIGHTWARDS ARROW]2)-α-l-Rha4Ac-(1[RIGHTWARDS ARROW]3)-β-l-Rha-(1[RIGHTWARDS ARROW]4)-β-l-Rha-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc6Ac-(1[RIGHTWARDS ARROW]Tao et al. (2004)
O116[RIGHTWARDS ARROW]2)-β-d-Qui4NAc-(1[RIGHTWARDS ARROW]6)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]4)-α-d-GalNAc-(1[RIGHTWARDS ARROW]4)-α-d-GalA-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Leslie et al. (1999)
O117[RIGHTWARDS ARROW]4)-β-d-GalNAc-(1[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]4)-α-d-Glc-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GalNAc-(1[RIGHTWARDS ARROW]Leslie et al. (2000)
O139β-d-Glc-(1[RIGHTWARDS ARROW]3) | [RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]4)-α-d-GalA-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-l-Rha-(1[RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]Marie et al. (1998)
O153[RIGHTWARDS ARROW]2)-β-d-Ribf-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]4)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]4)-β-d-Gal-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]Ratnayake et al. (1994a)
O167α-d-Galf-(1[RIGHTWARDS ARROW]4) | [RIGHTWARDS ARROW]2)-β-d-GalA6N(l)Ala-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]2)-β-d-Galf-(1[RIGHTWARDS ARROW]5)-β-d-Galf-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc-(1[RIGHTWARDS ARROW]Linnerborg et al. (1997b)
O172[RIGHTWARDS ARROW]3)-α-l-FucNAc-(1[RIGHTWARDS ARROW]4)-α-d-Glc6Ac-(1-P[RIGHTWARDS ARROW]4)-α-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-FucNAc-(1[RIGHTWARDS ARROW]3)-α-d-GlcNAc-(1[RIGHTWARDS ARROW]Landersjöet al. (2001)

Genetic analysis of E. coli O26 and O172 has revealed that the second sugar is added to the d-GlcNAc-PP-undecaprenol carrier by a UDP-l-FucNAc transferase to form an α-(1[RIGHTWARDS ARROW]3)-linkage (Guo et al., 2004; D'Souza et al., 2002). Analysis of the O-antigen structures hitherto determined indicates that in the serogroups O4, O25 and O172 the third sugar to be added is an α-(1[RIGHTWARDS ARROW]3)-linked glucosyl residue, i.e. the backbone, or part of it, has the following structure: [RIGHTWARDS ARROW]X)-α-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-FucNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc(1[RIGHTWARDS ARROW], where X represents different linkage positions. Further genetic similarities may be present, e.g. in O4:K52, [RIGHTWARDS ARROW]2)-α-l-Rha-(1[RIGHTWARDS ARROW]6)-α-d-Glc-(1[RIGHTWARDS ARROW]3)-α-l-FucNAc-(1[RIGHTWARDS ARROW]3)-β-d-GlcNAc(1[RIGHTWARDS ARROW], and O26 (e.g. without the glucosyl residue), where the last sugar is an α-linked rhamnosyl residue, which is possibly also the case for O25. The latter strain carries an additional d-Glc residue that forms a substituted branch-point residue. In analogy to the hypothesis described above, close structural relationships are observed between, for example, O6, O17, O44, O58, O77, O78 and O88, having a Man-Man-GlcNAc sequence at the reducing end. Although in E. coli the numbering of serogroups is chronological, at least with newly described strains, with the most recent ones covering O174-O181 (Scheutz et al., 2004), subgroups are present in some cases based on cross-reactivity, e.g. in O1, O18 and most recently in O5, (Urbina et al., 2005) similar to the Danish serotyping scheme for Streptococcus pneumoniae capsular polysaccharides, which is based on cross-reactivity, in contrast to the American system for which up to almost 100 different CPS serotypes have been described (Tomasz, 2000). In the future one may also type E. coli based on genetic resemblance between the strains which then should explain both structural and cross-reactivity relationships. Furthermore, other structural similarities such as those of blood-group determinants are present for the O86, O90, O127 and O128 O-antigens, and these strains presumably utilize the concept of molecular mimicry, thereby evading the immune system of the human host (Moran et al., 1996).

In some of the E. coli strains the O-antigen structures contain terminal glucosyl or N-acetylglycosamine residues, e.g. in O23A, O139 and O142, as side-chains. Whether these residues are added by a phage-induced glycosyl transferase machinery or by another mechanism is of great interest for future genetic studies as the positioning of the side-chain onto the structure differs and sometimes leads to a doubly branched residue, e.g. in O141. In many cases the repeating unit is formed and structurally determined by the polymerization process, e.g. in O55 and O164, often occurring at the penultimate sugar residue of the linear undecaprenol-PP-oligosaccharide leading to a single sugar residue in the side-chain, e.g. in O35, O113, O152, O159 and O167.

The O-antigen of Shigella boydii type 13 was recently both structurally and genetically characterized (Feng et al., 2004b). Although this strain is more distantly related to E. coli and other Shigella species, its O-antigen shows a quite close structural resemblance to that of E. coli O172. The linear pentasaccharide of S. boydii type 13 has the following chemical structure: [RIGHTWARDS ARROW]3)-α-l-QuipNAc-(1[RIGHTWARDS ARROW]4)-α-d-Glcp-(1[RIGHTWARDS ARROW]P-4)-α-d-GlcpNAc-(1[RIGHTWARDS ARROW]3)-α-l-QuipNAc-(1[RIGHTWARDS ARROW]3)-α-d-GlcpNAc-(1[RIGHTWARDS ARROW], in which the 4-linked GlcNAc residue is 6-O-acetylated to ∼ 15%. Based on biosynthetic considerations where an N-acetylglycosamine residue should be present at the reducing end, two possibilities were suggested for the biological repeating unit, i.e. the one above or the frame-shifted one with the 4-linked GlcNAc residue at the reducing end. From the structural results presented in this article we propose that the biological repeating unit of the O-antigen from S. boydii type 13 has a 3-linked GlcNAc residue at the reducing end as presented in the above structure. In both the E. coli O172 and the S. boydii type 13 O-antigens the glucosyl-1-phosphoryl residue is the penultimate one (as presented) in the assembled linear undecaprenol-PP-oligosaccharide. The O-antigens of E. coli O152 and O173 have branched structures with one sugar residue as the side-chain and, most notably, the branching sugar is a glycosyl-1-phosphoryl residue being the penultimate one, suggesting similar biosynthetic pathways. Future detailed investigations will clarify the whole assembly of these E. coli O-antigen units and that of S. boydii type 13.

Concluding remarks

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

Members of the species Escherichia coli range from completely harmless to life-threatening microorganisms. The differences are based on particular virulence factors that certain strains may have acquired. These factors may be toxins or surface structures that enable the bacterium to adhere to mammalian cells or to evade the immune system. The typing of E. coli is often based on detection of different surface molecules using specific antibodies. The O-antigen present in the lipopolysaccharide is one of the molecules used in serotyping. As of today, more than 180 different O-serotypes have been described but not even half of them have been structurally elucidated.

The E. coli database implemented facilitates a more rapid identification of strains that are difficult to type or suggests similarities to previously determined O-antigens in the case of novel isolates. Analysis of the O-antigen structures revealed that 3-linked N-acetylglucosamine or N-acetylgalactosamine residues should be present at the reducing end of the biological repeating unit, in accordance with NMR spectroscopy and genetic data. In a limited number of cases, a 4-linked N-acetylglucosamine residue is instead observed. The topology with four sugar residues in the backbone of the O-antigen is present in half of the hitherto determined structures. Future structural studies should be combined with genetic analysis of the O-antigen cluster to facilitate insight into structural patterns and biosynthetic pathways. As part of this effort, amino acid sequences of flippases and polymerases are being added as elements of the entries in the database.

Note

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References

This review covers structures reported up to early 2005. In addition, recently reported E. coli O-antigen structures are those of serogroups O178 (Ali et al., 2005) and O145 (Feng et al., 2005). Noteworthy is also the fact that phenotypically rough E. coli K12 have been genetically complemented to produce its O-antigen, an O16 variant with cross-reactivity to O17 (Liu & Reeves, 1994; Stevenson et al., 1994).

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Enteric/diarrhoeal Escherichia coli
  5. Urinary tract infections
  6. Sepsis/meningitis
  7. Typing of Escherichia coli
  8. Lipopolysaccharide
  9. Structural determination of O-antigens from strains that are difficult to type or of nontyped strains
  10. Biosynthesis considerations
  11. O-antigen repeating units: characteristics and statistics of the structures
  12. Concluding remarks
  13. Note
  14. Acknowledgements
  15. References
  • Adeyeye A, Jansson PE, Lindberg B, Abaas S & Svenson SB (1988) Structural studies of the Escherichia coli O-149 O-antigen polysaccharide. Carbohydr Res 176: 231236.
  • Albert MJ, Faruque SM, Ansaruzzaman M, Islam MM, Haider K, Alam K, Kabir I & Robins-Browne R (1992) Sharing of virulence-associated properties at the phenotypic and genetic levels between enteropathogenic Escherichia coli and Hafnia alvei. J Med Microbiol 37: 310314.
  • Alexander DC & Valvano MA (1994) Role of the rfe gene in the biosynthesis of the Escherichia coli O7-specific lipopolysaccharide and other O-specific polysaccharides containing N-acetylglucosamine. J Bacteriol 176: 70797084.
  • Ali T, Urbina F, Weintraub A & Widmalm G (2005) Structural studies of the O-antigenic polysaccharides from the enteroaggregative Escherichia coli strain 522/C1 and the international type strain from Escherichia coli O178. Carbohydr Res 340: 20102014.
  • Andersson M, Carlin N, Leontein K, Lindquist U & Slettengren K (1989) Structural studies of the O-antigenic polysaccharide of Escherichia coli O86, which possesses blood-group B activity. Carbohydr Res 185: 211223.
  • Anderson AN, Richards JC & Perry MB (1992) Structure of the O-antigen of Escherichia coli O119 lipopolysaccharide. Carbohydr Res 237: 249262.
  • Arduino RC & DuPont HL (1993) Travellers' diarrhoea. Baillieres Clin Gastroenterol 7: 365385.
  • Aucken HM & Pitt TL (1991) Serological relationships of the O antigens of Klebsiella pneumoniae O5, Escherichia coli O8 and a new O serotype of Serratia marcescens. FEMS Microbiol Lett 64: 9397.
  • Bartelt M, Shashkov AS, Kochanowski H, Jann B & Jann K (1993) Structure of the O-specific polysaccharide of the O23 antigen (LPS) from Escherichia coli O23:K?H16. Carbohydr Res 248: 233240.
  • Bartelt M, Shashkov AS, Kochanowski H, Jann B & Jann K (1994) Structure of the O-specific polysaccharide of the O22-antigen (LPS) from Escherichia coli O22:K13. Carbohydr Res 254: 203212.
  • Baudry B, Maurelli AT, Clerc P, Sadoff JC & Sansonetti PJ (1987) Localization of plasmid loci necessary for the entry of Shigella flexneri into HeLa cells, and characterization of one locus encoding four immunogenic polypeptides. J Gen Microbiol 133: 34033413.
  • Baumann H, Jansson PE, Kenne L & Widmalm G (1991) Structural studies of the Escherichia coli O1A O-polysaccharide, using the computer program CASPER. Carbohydr Res 211: 183190.
  • Bettelheim KA, Evangelidis H, Pearce JL, Sowers E & Strockbine NA (1993) Isolation of a Citrobacter freundii strain which carries the Escherichia coli O157 antigen. J Clin Microbiol 31: 760761.
  • Bhan MK, Bhandari N, Sazawal S, Clemens J, Raj P, Levine MM & Kaper JB (1989a) Descriptive epidemiology of persistent diarrhoea among young children in rural northern India. Bull World Health Organ 67: 281288.
  • Bhan MK, Raj P, Levine MM, Kaper JB, Bhandari N, Srivastava R, Kumar R & Sazawal S (1989b) Enteroaggregative Escherichia coli associated with persistent diarrhea in a cohort of rural children in India. J Infect Dis 159: 10611064.
  • Bhan MK, Sazawal S, Raj P, Bhandari N, Kumar R, Bhardwaj Y, Shrivastava R & Bhatnagar S (1989c) Aggregative Escherichia coli, Salmonella, and Shigella are associated with increasing duration of diarrhea. Indian J Pediatr 56: 8186.
  • Bhatnagar S, Bhan MK, Sommerfelt H, Sazawal S, Kumar R & Saini S (1993) Enteroaggregative Escherichia coli may be a new pathogen causing acute and persistent diarrhea. Scand J Infect Dis 25: 579583.
  • Bilge SS, Clausen CR, Lau W & Moseley SL (1989) Molecular characterization of a fimbrial adhesin, F1845, mediating diffuse adherence of diarrhea-associated Escherichia coli to hep-2 cells. J Bacteriol 171: 42814289.
  • Bilge SS, Apostol JM Jr, Aldape MA & Moseley SL (1993a) mRNA processing independent of RNase III and RNase E in the expression of the F1845 fimbrial adhesin of Escherichia coli. Proc Natl Acad Sci USA 90: 14551459.
  • Bilge SS, Apostol JM Jr, Fullner KJ & Moseley SL (1993b) Transcriptional organization of the F1845 fimbrial adhesin determinant of Escherichia coli. Mol Microbiol 7: 9931006.
  • Black RE (1990) Epidemiology of travelers' diarrhea and relative importance of various pathogens. Rev Infect Dis 12 (Suppl. 1): S73S79.
  • Black RE (1993) Epidemiology of diarrhoeal disease: implications for control by vaccines. Vaccine 11: 100106.
  • Bouzari S, Jafari A, Farhoudi-Moghaddam AA, Shokouhi F & Parsi M (1994) Adherence of non-enteropathogenic Escherichia coli to HeLa cells. J Med Microbiol 40: 9597.
  • Boyce TG, Swerdlow DL & Griffin PM (1995) Escherichia coli O157:H7 and the hemolytic-uremic syndrome. N Engl J Med 333: 364368.
  • Brade H, Opal SM, Vogel SN & Morrison DC (eds) (1999) Endotoxin in Health and Disease. Marcel Dekker, Inc., New York.
  • Bundle DR, Gerken M & Perry MB (1986) Two-dimensional nuclear magnetic resonance at 500 MHz: the structural elucidation of a Salmonella serogroup N polysaccharide antigen. Can J Chem 64: 255264.
  • Campos LC, Franzolin MR & Trabulsi LR (2004) Diarrheagenic Escherichia coli categories among the traditional enteropathogenic E. coli O serogroups. Mem Inst Oswaldo Cruz 99: 545552.
  • Chen HD & Frankel G (2005) Enteropathogenic Escherichia coli: unravelling pathogenesis. FEMS Microbiol Rev 29: 8398.
  • Cravioto A, Reyes RE, Ortega R, Fernandez G, Hernandez R & Lopez D (1988) Prospective study of diarrhoeal disease in a cohort of rural Mexican children: incidence and isolated pathogens during the first two years of life. Epidemiol Infect 101: 123134.
  • Cravioto A, Reyes RE, Trujillo F, Uribe F, Navarro A, De La Roca JM, Hernandez JM, Perez G & Vazquez V (1990) Risk of diarrhea during the first year of life associated with initial and subsequent colonization by specific enteropathogens. Am J Epidemiol 131: 886904.
  • Cravioto A, Tello A, Navarro A, Ruiz J, Villafan H, Uribe F & Eslava C (1991) Association of Escherichia coli HEp-2 adherence patterns with type and duration of diarrhoea. Lancet 337: 262264.
  • Darfeuille-Michaud A (2002) Adherent-invasive Escherichia coli: a putative new E. coli pathotype associated with Crohn's disease. Int J Med Microbiol 292: 185193.
  • Datta AK, Basu S & Roy N (1999) Chemical and immunochemical studies of the O-antigen from enteropathogenic Escherichia coli O158 lipopolysaccharide. Carbohydr Res 322: 219227.
  • Dawson KG, Emerson JC & Burns JL (1999) Fifteen years of experience with bacterial meningitis. Pediatr Infect Dis J 18: 816822.
  • De Rycke J, Milon A & Oswald E (1999) Necrotoxic Escherichia coli (NTEC): two emerging categories of human and animal pathogens. Vet Res 30: 221233.
  • Dmitriev BA, Lvov VL, Kochetkov NK, Jann B & Jann K (1976) Cell-wall lipopolysaccharide of the ‘Shigella-like’Escherichia coli O124. Structure of the polysaccharide chain. Eur J Biochem 64: 491498.
  • Dmitriev BA, Knirel YA, Kochetkov NK, Jann B & Jann K (1977) Cell-wall lipopolysaccharide of the ‘Shigella-like’Escherichia coli O58. Structure of the polysaccharide chain. Eur J Biochem 79: 111115.
  • Dmitriev BA, Lvov V, Tochtamysheva NV, Shashkov AS, Kochetkov NK, Jann B & Jann K (1983) Cell-wall lipopolysaccharide of Escherichia coli O114:H2. Structure of the polysaccharide chain. Eur J Biochem 134: 517521.
  • Donnenberg MS & Nataro JP (1995) Methods for studying adhesion of diarrheagenic Escherichia coli. Methods Enzymol 253: 324336.
  • D'Souza JM, Wang L & Reeves P (2002) Sequence of the Escherichia coli O26 O antigen gene cluster and identification of O26 specific genes. Gene 297: 123127.
  • DuPont HL & Ericsson CD (1993) Prevention and treatment of traveler's diarrhea. N Engl J Med 328: 18211827.
  • Dutta S, Chatterjee A, Dutta P, Rajendran K, Roy S, Pramanik KC & Bhattacharya SK (2001) Sensitivity and performance characteristics of a direct PCR with stool samples in comparison to conventional techniques for diagnosis of Shigella and enteroinvasive Escherichia coli infection in children with acute diarrhoea in Calcutta, India. J Med Microbiol 50: 667674.
  • Eklund K, Garegg PJ, Kenne L, Lindberg AA & Lindberg B (1978) Structural studies on the Escherichia coli O111 lipopolysaccharide. Abstracts of the IXth International Symposium of Carbohydrate Chemistry, London.
  • Erbing C, Kenne L & Lindberg B (1977) Structural studies of the O-specific side-chains of the cell-wall lipopolysaccharide from Escherichia coli O69. Carbohydr Res 56: 371376.
  • Erbing C, Kenne L, Lindberg B & Hammarström S (1978) Structure of the O-specific side-chain of the Escherichia coli O75 lipopolysaccharide: a revision. Carbohydr Res 60: 400403.
  • Ewing WH (1986) The genus Escherichia. Edwards and Ewing's identification of Enterobacteriaceae, 4th edn (Edwards PR & Ewing WH, eds) pp. 93134. Elsevier Science Publishing Co., Inc., New York.
  • Ezawa A, Gocho F, Saitoh M, Tamura T, Kawata K, Takahashi T & Kikuchi N (2004) A three-year study of enterohemorrhagic Escherichia coli O157 on a farm in Japan. J Vet Med Sci 66: 779784.
  • Fang GD, Lima AA, Martins CV, Nataro JP & Guerrant RL (1995) Etiology and epidemiology of persistent diarrhea in northeastern Brazil: a hospital-based, prospective, case-control study. J Pediatr Gastroenterol Nutr 21: 137144.
  • Färnbäck M, Weintraub A & Widmalm G (1998) Structural determination of the O-antigenic polysaccharide from Escherichia coli O141. Eur J Biochem 254: 168171.
  • Feng L, Senchenkova SN, Yang J, et al. (2004a) Synthesis of the heteropolysaccharide O antigen of Escherichia coli O52 requires an ABC transporter: structural and genetic evidence. J Bacteriol 186: 45104519.
  • Feng L, Senchenkova SN, Yang J, Shashkov AS, Tao J, Guo H, Zhao G, Knirel YA, Reeves P & Wang L (2004b) Structural and genetic characterization of the Shigella boydii type 13 O antigen. J Bacteriol 186: 383392.
  • Feng L, Senchenkova SN, Tao J, Shashkov AS, Liu B, Shevelev SD, Reeves PR, Xu J, Knirel YA & Wang L (2005) Structural and genetic characterization of enterohemorrhagic Escherichia coli O145 O antigen and development of an O145 serogroup-specific PCR assay. J Bacteriol 187: 758764.
  • Flores Abuxapqui JJ, Suarez Hoil GJ, Heredia Navarrete MR, Puc Franco MA & Vivas Rosel ML (1999) Four biochemical tests for identification of probable enteroinvasive Escherichia coli strains. Rev Latinoam Microbiol 41: 259261.
  • Gamian A, Romanowska E, Ulrich J & Defaye J (1992) The structure of the sialic acid-containing Escherichia coli O104 O-specific polysaccharide and its linkage to the core region in lipopolysaccharide. Carbohydr Res 236: 195208.
  • Gamian A, Kenne L, Mieszala M, Ulrich J & Defaye J (1994) Structure of the Escherichia coli O24 and O56 O-specific sialic-acid-containing polysaccharides and linkage of these structures to the core region in lipopolysaccharides. Eur J Biochem 225: 12111220.
  • Germani Y, Begaud E, Duval P & Le Bouguenec C (1996) Prevalence of enteropathogenic, enteroaggregative, and diffusely adherent Escherichiacoli among isolates from children with diarrhea in new Caledonia. J Infect Dis 174: 11241126.
  • Gioffre A, Meichtri L, Zumarraga M, Rodriguez R & Cataldi A (2004) Evaluation of a QIAamp DNA stool purification kit for Shiga-toxigenic Escherichia coli detection in bovine fecal swabs by PCR. Rev Argent Microbiol 36: 15.
  • Giron JA, Jones T, Millan-Velasco F, et al. (1991) Diffuse-adhering Escherichia coli (DAEC) as a putative cause of diarrhea in Mayan children in Mexico. J Infect Dis 163: 507513.
  • Goldberg MB & Sansonetti PJ (1993) Shigella subversion of the cellular cytoskeleton: a strategy for epithelial colonization. Infect Immun 61: 49414946.
  • Gomes TA, Blake PA & Trabulsi LR (1989) Prevalence of Escherichia coli strains with localized, diffuse, and aggregative adherence to HeLa cells in infants with diarrhea and matched controls. J Clin Microbiol 27: 266269.
  • Gomes TA, Rassi V, Mac Donald KL, et al. (1991) Enteropathogens associated with acute diarrheal disease in urban infants in Sao Paulo, Brazil. J Infect Dis 164: 331337.
  • Gonzalez R, Diaz C, Marino M, Cloralt R, Pequeneze M & Perez-Schael I (1997) Age-specific prevalence of Escherichia coli with localized and aggregative adherence in Venezuelan infants with acute diarrhea. J Clin Microbiol 35: 11031107.
  • Grimm LM, Goldoft M, Kobayashi J, Lewis JH, Alfi D, Perdichizzi AM, Tarr PI, Ongerth JE, Moseley SL & Samadpour M (1995) Molecular epidemiology of a fast-food restaurant-associated outbreak of Escherichia coli O157:H7 in Washington State. J Clin Microbiol 33: 21552158.
  • Grozdanov L, Zähringer U, Blum-Oehler G, et al. (2002) A single nucleotide exchange in the wzy gene is responsible for the semirough O6 lipopolysaccharide phenotype and serum sensitivity of Escherichia coli strain Nissle 1917. J Bacteriol 184: 59125925.
  • Gunzburg ST, Chang BJ, Elliott SJ, Burke V & Gracey M (1993) Diffuse and enteroaggregative patterns of adherence of enteric Escherichia coli isolated from aboriginal children from the Kimberley region of Western Australia. J Infect Dis 167: 755758.
  • Guo H, Feng L, Tao J, Zhang C & Wang L (2004) Identification of Escherichia coli O172 O-antigen gene cluster and development of a serogroup-specific PCR assay. J Appl Microbiol 97: 181190.
  • Gupta DS, Shashkov AS, Jann B & Jann K (1992) Structures of the O1B and O1C lipopolysaccharide antigens of Escherichia coli. J Bacteriol 174: 79637970.
  • Hicks S, Candy DC & Phillips AD (1996) Adhesion of enteroaggregative Escherichia coli to pediatric intestinal mucosa in vitro. Infect Immun 64: 47514760.
  • Hoque SS, Faruque AS, Mahalanabis D & Hasnat A (1994) Infectious agents causing acute watery diarrhoea in infants and young children in Bangladesh and their public health implications. J Trop Pediatr 40: 351354.
  • Hygge Blackeman K, Weintraub A & Widmalm G (1998) Structural determination of the O-antigenic polysaccharide from the enterotoxigenic Escherichia coli O147. Eur J Biochem 251: 534537.
    Direct Link:
  • Jallat C, Livrelli V, Darfeuille-Michaud A, Rich C & Joly B (1993) Escherichia coli strains involved in diarrhea in France: high prevalence and heterogeneity of diffusely adhering strains. J Clin Microbiol 31: 20312037.
  • Jann B, Shashkov AS, Gupta DS & Jann K (1992a) The O18 antigens (lipopolysaccharides) of Escherichia coli. Structural characterization of the O18A, O18A1, O18B, O18B1-specific polysaccharides. Eur J Biochem 210: 241248.
  • Jann B, Shashkov AS, Gupta DS, Panasenko SM & Jann K (1992b) The O1 antigen of Escherichia coli: structural characterization of the O1A1-specific pdysaccharide. Carbohydr Polymers 18: 5157.
  • Jann B, Shashkov AS, Kochanowski H & Jann K (1993) Structural comparison of the O4-specific polysaccharides from E. coli O4:K6 and E. coli O4:K52. Carbohydr Res 248: 241250.
  • Jann B, Shashkov AS, Hahne M, Kochanowski H & Jann K (1994a) Structure of the O83-specific polysaccharide of Escherichia coli O83:K24:H31. Carbohydr Res 261: 215222.
  • Jann B, Shashkov AS, Kochanowski H & Jann K (1994b) Structure of the O16 polysaccharide from Escherichia coli O16:K1: an NMR investigation. Carbohydr Res 264: 305311.
  • Jann B, Shashkov AS, Kochanowski H & Jann K (1994c) Structural comparison of the O6 specific polysaccharides from E. coli O6:K2:H1, E. coli O6:K13:H1, and E. coli O6:K54:H10. Carbohydr Res 263: 217225.
  • Jann B, Shashkov A, Torgov V, Kochanowski H, Seltmann G & Jann K (1995) NMR investigation of the 6-deoxy-L-talose-containing O45, O45-related (O45rel), and O66 polysaccharides of Escherichia coli. Carbohydr Res 278: 155165.
  • Jansson PE, Lindberg B, Lönngren J, Ortega C & Svenson SB (1984) Structural studies of the Escherichia coli O-antigen 6. Carbohydr Res 131: 277283.
  • Jansson PE, Lönngren J, Widmalm G, Leontein K, Slettengren K, Svenson SB, Wrangsell G, Dell A & Tiller PR (1985) Structural studies of the O-antigen polysaccharides of Klebsiella O5 and Escherichia coli O8. Carbohydr Res 145: 5966.
  • Jansson PE, Lennholm H, Lindberg B, Lindquist U & Svenson SB (1987a) Structural studies of the O-specific side-chains of the Escherichia coli O2 lipopolysaccharide. Carbohydr Res 161: 273279.
  • Jansson PE, Lindberg B, Widmalm G & Leontein K (1987b) Structural studies of the Escherichia coli O78 O-antigen polysaccharide. Carbohydr Res 165: 8792.
  • Jansson PE, Kenne L & Widmalm G (1989) Structure of the O-antigen polysaccharide from Escherichia coli O18ac: a revision using computer-assisted structural analysis with the program CASPER. Carbohydr Res 193: 322325.
  • Johnson JR (1991) Virulence factors in Escherichia coli urinary tract infection. Clin Microbiol Rev 4: 80128.
  • Kai E, Ikebukuro K, Hoshina S, Watanabe H & Karube I (2000) Detection of PCR products of Escherichia coli O157:H7 in human stool samples using surface plasmon resonance (SPR). FEMS Immunol Med Microbiol 29: 283288.
  • Kaper JB (1998) Enterohemorrhagic Escherichia coli. Curr Opin Microbiol 1: 103108.
  • Kaper JB, Nataro JP & Mobley HL (2004) Pathogenic Escherichia coli. Nat Rev Microbiol 2: 123140.
  • Katzenellenbogen E, Kocharova NA, Zatonsky GV, Kübler-Kielb J, Gamian A, Shashkov AS, Knirel YA & Romanowska E (2001) Structural and serological studies on Hafnia alvei O-specific polysaccharide of α-D-mannan type isolated from the lipopolysaccharide of strain PCM 1223. FEMS Immunol Med Microbiol 30: 223227.
  • Kehl SC (2002) Role of the laboratory in the diagnosis of enterohemorrhagic Escherichia coli infections. J Clin Microbiol 40: 27112715.
  • Kenne L, Lindberg B, Madden JK, Lindberg AA & Gemski P Jr (1983a) Structural studies of the Escherichia coli O-antigen 25. Carbohydr Res 122: 249256.
  • Kenne L, Lindberg B, Söderholm E, Bundle DR & Griffith DW (1983b) Structural studies of the O-antigens from Salmonella greenside and Salmonella adelaide. Carbohydr Res 111: 289296.
  • Kenne L, Lindberg B, Lugowski C & Svenson SB (1986) Structural studies of the O-specific side-chains of the Escherichia coli O10 lipopolysaccharide. Carbohydr Res 151: 349358.
  • Kerneis S, Bilge SS, Fourel V, Chauviere G, Coconnier MH & Servin AL (1991) Use of purified F1845 fimbrial adhesin to study localization and expression of receptors for diffusely adhering Escherichia coli during enterocytic differentiation of human colon carcinoma cell lines HT-29 and Caco-2 in culture. Infect Immun 59: 40134018.
  • Kjellberg A, Urbina F, Weintraub A & Widmalm G (1996) Structural analysis of the O-antigenic polysaccharide from the enteropathogenic Escherichia coli O125. Eur J Biochem 239: 532538.
  • Kjellberg A, Weintraub A & Widmalm G (1999) Structural determination and biosynthetic studies of the O-antigenic polysaccharide from the enterohemorrhagic Escherichia coli O91 using 13C-enrichment and NMR spectroscopy. Biochemistry 38: 1220512211.
  • Kopecko DJ (1994) Experimental keratoconjunctivitis (Sereny) assay. Methods Enzymol 235: 3947.
  • Landersjö C, Weintraub A & Widmalm G (1996) Structure determination of the O-antigen polysaccharide from the enteroinvasive Escherichia coli (EIEC) O143 by component analysis and NMR spectroscopy. Carbohydr Res 291: 209216.
  • Landersjö C, Weintraub A & Widmalm G (1997) Structural analysis of the O-antigenic polysaccharide from the enteropathogenic Escherichia coli O142. Eur J Biochem 244: 449453.
  • Landersjö C, Weintraub A & Widmalm G (2001) Structural analysis of the O-antigen polysaccharide from the Shiga toxin-producing Escherichia coli O172. Eur J Biochem 268: 22392245.
  • Larsson EA, Urbina F, Yang Z, Weintraub A & Widmalm G (2004) Structural and immunochemical relationship between the O-antigenic polysaccharides from the enteroaggregative Escherichia coli strain 396/C-1 and Escherichia coli O126. Carbohydr Res 339: 14911496.
  • Lerouge I & Vanderleyden J (2001) O-antigen structural variation: mechanisms and possible roles in animal/plant–microbe interactions. FEMS Microbiol Rev 26: 1747.
  • Leslie MR, Parolis H & Parolis LA (1999) The structure of the O-antigen of Escherichia coli O116:K+:H10. Carbohydr Res 321: 246256.
  • Leslie MR, Parolis H & Parolis LA (2000) The structure of the O-specific polysaccharide of Escherichia coli O117:K98:H4. Carbohydr Res 323: 103110.
  • Levine MM, Caplan ES, Waterman D, Cash RA, Hornick RB & Snyder MJ (1977) Diarrhea caused by Escherichia coli that produce only heat-stable enterotoxin. Infect Immun 17: 7882.
  • Levine MM & Edelman R (1984) Enteropathogenic Escherichia coli of classic serotypes associated with infant diarrhea: epidemiology and pathogenesis. Epidemiol Rev 6: 3151.
  • Levine MM (1987) Escherichia coli that cause diarrhea: enterotoxigenic, enteropathogenic, enteroinvasive, enterohemorrhagic, and enteroadherent. J Infect Dis 155: 377389.
  • Levine MM, Ferreccio C, Prado V, et al. (1993) Epidemiologic studies of Escherichia coli diarrheal infections in a low socioeconomic level peri-urban community in Santiago, Chile. Am J Epidemiol 138: 849869.
  • Lima AA, Fang G, Schorling JB, De Albuquerque L, Mc Auliffe JF, Mota S, Leite R & Guerrant RL (1992) Persistent diarrhea in northeast Brazil: etiologies and interactions with malnutrition. Acta Paediatr Suppl 381: 3944.
  • Lindberg B, Lindh F & Lönngren J (1981) Structural studies of the O-specific side-chain of the lipopolysaccharide from Escherichia coli O55. Carbohydr Res 97: 105112.
  • Linnerborg M, Weintraub A & Widmalm G (1997a) Structural studies of the O-antigen polysaccharide from Escherichia coli O138. Eur J Biochem 247: 567571.
  • Linnerborg M, Wollin R & Widmalm G (1997b) Structural studies of the O-antigenic polysaccharide from Escherichia coli O167. Eur J Biochem 246: 565573.
  • Linnerborg M, Weintraub A & Widmalm G (1999a) Structural studies of the O-antigen polysaccharide from the enteroinvasive Escherichia coli O164 cross-reacting with Shigella dysenteriae type 3. Eur J Biochem 266: 460466.
  • Linnerborg M, Weintraub A & Widmalm G (1999b) Structural studies of the O-antigen polysaccharide from the enteroinvasive Escherichia coli O173. Carbohydr Res 320: 200208.
  • Linnerborg M, Weintraub A & Widmalm G (1999c) Structural studies utilizing 13C-enrichment of the O-antigen polysaccharide from the enterotoxigenic Escherichia coli O159 cross-reacting with Shigella dysenteriae type 4. Eur J Biochem 266: 246251.
  • Liu D & Reeves PR (1994) Escherichia coli K12 regains its O antigen. Microbiology 140: 4957.
  • L'vov VL, Shashkov AS, Dmitriev BA, Kochetkov NK, Jann B & Jann K (1984) Structural studies of the O-specific side chain of the lipopolysaccharide from Escherichia coli O:7. Carbohydr Res 126: 249259.
  • L'vov VL, Iakovlev AP, Shashkov AS & Dmitriev BA (1991) Antigenic polysaccharides of Shigella bacteria. Structure of the polysaccharide chain of the lipopolysaccharide from Shigella boydii, type 11. Bioorg Khim 17: 111120.
  • Lycknert K & Widmalm G (2004) Dynamics of the Escherichia coli O91 O-antigen polysaccharide in solution as studied by carbon-13 NMR relaxation. Biomacromolecules 5: 10151020.
  • Mac Lean LL & Perry MB (1997) Structural characterization of the serotype O:5 O-polysaccharide antigen of the lipopolysaccharide of Escherichia coli O:5. Biochem Cell Biol 75: 199205.
  • Manca MC, Weintraub A & Widmalm G (1996) Structural studies of the Escherichia coli O26 O-antigen polysaccharide. Carbohydr Res 281: 155160.
  • Manges AR, Johnson JR, Foxman B, O'Bryan TT, Fullerton KE & Riley LW (2001) Widespread distribution of urinary tract infections caused by a multidrug-resistant Escherichia coli clonal group. N Engl J Med 345: 10071013.
  • Mangia AH, Duarte AN, Duarte R, Silva LA, Bravo VL & Leal MC (1993) Aetiology of acute diarrhoea in hospitalized children in Rio de Janeiro City, Brazil. J Trop Pediatr 39: 365367.
  • Marie C, Weintraub A & Widmalm G (1998) Structural studies of the O-antigenic polysaccharide from Escherichia coli O139. Eur J Biochem 254: 378381.
  • Marolda CL, Vicarioli J & Valvano MA (2004) Wzx proteins involved in biosynthesis of O antigen function in association with the first sugar of the O-specific lipopolysaccharide subunit. Microbiology 150: 40954105.
  • Marsden BJ, Bundle DR & Perry MB (1994) Serological and structural relationships between Escherichia coli O:98 and Yersinia enterocolitica O:11,23 and O:11,24 lipopolysaccharide O-antigens. Biochem Cell Biol 72: 163168.
  • Masoud H & Perry MB (1996) Structural characterization of the O-antigenic polysaccharide of Escherichia coli serotype O17 lipopolysaccharide. Biochem Cell Biol 74: 241248.
  • Mc Connell M.M., Smith H.R., Willshaw G.A., Field A.M. & Rowe B. (1981) Plasmids coding for colonization factor antigen I and heat-stable enterotoxin production isolated from enterotoxigenic Escherichia coli: comparison of their properties. Infect Immun 32: 927936.
  • Medina EC, Widmalm G, Weintraub A, Vial PA, Levine MM & Lindberg AA (1994) Structural studies of the O-antigenic polysaccharides of Escherichia coli O3 and the enteroaggregative Escherichia coli strain 17-2. Eur J Biochem 224: 191196.
  • Moran AP, Prendergast MM & Appelmelk BJ (1996) Molecular mimicry of host structures by bacterial lipopolysaccharides and its contribution to disease. FEMS Immunol Med Microbiol 16: 105115.
  • Murray BE, Evans DJ Jr, Penaranda ME & Evans DG (1983) CFA/I-heat-stable plasmids: comparison of enterotoxigenic Escherichia coli (ETEC) of serogroups O25, O63, O78, and O128 and mobilization from an R factor-containing epidemic ETEC isolate. J Bacteriol 153: 566570.
  • Nataro JP & Kaper JB (1998) Diarrheagenic Escherichia coli. Clin Microbiol Rev 11: 142201.
  • Nataro JP, Kaper JB, Robins-Browne R, Prado V, Vial P & Levine MM (1987) Patterns of adherence of diarrheagenic Escherichia coli to HEp-2 cells. Pediatr Infect Dis J 6: 829831.
  • Nataro JP, Steiner T & Guerrant RL (1998) Enteroaggregative Escherichia coli. Emerg Infect Dis 4: 251261.
  • Nishiuchi Y, Doe M, Hotta H & Kobayashi K (2000) Structure and serologic properties of O-specific polysaccharide from Citrobacter freundii possessing cross-reactivity with Escherichia coli O157:H7. FEMS Immunol Med Microbiol 28: 163171.
  • Nishiuchi Y, Doe M, Hotta H & Kobayashi K (2002) Addendum to: “Structure and serological properties of O-specific polysaccharide from Citrobacter freundii possessing cross-reactivity with Escherichia coli O157:H7” [FEMS Immunol. Med. Microbiol. 28 (2000) 163–171]. Med. Microbiol 28: 163171].
  • Nowicki B, Svanborg-Eden C, Hull R & Hull S (1989) Molecular analysis and epidemiology of the Dr hemagglutinin of uropathogenic Escherichia coli. Infect Immun 57: 446451.
  • Olsson U, Lycknert K, Stenutz R, Weintraub A & Widmalm G (2005) Structural analysis of the O-antigen polysaccharide from Escherichia coli O152. Carbohydr Res 340: 167171.
  • Orskov F & Orskov I (1984) Serotyping of Escherichia coli. Methods in Microbiology, Vol. 14 (BerganT, ed.), pp. 43112. Academic Press Inc., London.
  • Oxley D & Wilkinson SG (1986) Structure of the O-specific polysaccharide from the lipopolysaccharide of Serratia marcescens O8. Eur J Biochem 156: 597601.
  • Ozeki Y, Kurazono T, Saito A, Kishimoto T & Yamaguchi M (2003) A diffuse outbreak of enterohemorrhagic Escherichia coli O157:H7 related to the Japanese-style pickles in Saitama, Japan. Kansenshogaku Zasshi 77: 493498.
  • Parolis H & Parolis LA (1995) The structure of the O-specific polysaccharide from Escherichia coli O113 lipopolysaccharide. Carbohydr Res 267: 263269.
  • Parolis LA, Parolis H & Dutton GG (1986) Structural studies of the O-antigen polysaccharide of Escherichia coli O9a. Carbohydr Res 155: 272276.
  • Parolis H, Parolis LA & Olivieri G (1997) Structural studies on the Shigella-like Escherichia coli O121 O-specific polysaccharide. Carbohydr Res 303: 319325.
  • Parsot C & Sansonetti PJ (1996) Invasion and the pathogenesis of Shigella infections. Curr Top Microbiol Immunol 209: 2542.
  • Penaranda ME, Evans DG, Murray BE & Evans DJ, Jr. (1983) ST:LT:CFA/II plasmids in enterotoxigenic Escherichia coli belonging to serogroups O6, O8, O80, O85, and O139. J Bacteriol 154: 980983.
  • Perry MB & Mac Lean LL (1987) Structure of the lipopolysaccharide O-chain of Yersinia enterocolitica serotype O:5,27. Biochem Cell Biol 65: 17.
  • Perry MB & Mac Lean LL (1999) Structural characterization of the antigenic O-chain of the lipopolysaccharide of Escherichia coli serotype O65. Carbohydr Res 322: 5766.
  • Perry MB, Mac Lean LL & Brisson JR (1993) The characterization of the O-antigen of Escherichia coli O64:K99 lipopolysaccharide. Carbohydr Res 248: 277284.
  • Perry MB, Mac Lean L & Griffith DW (1986) Structure of the O-chain polysaccharide of the phenol-phase soluble lipopolysaccharide of Escherichia coli O:157:H7. Biochem Cell Biol 64: 2128.
  • Phillips I, Eykyn S, King A, Gransden WR, Rowe B, Frost JA & Gross RJ (1988) Epidemic multiresistant Escherichia coli infection in West Lambeth Health District. Lancet 1: 10381041.
  • Poitrineau P, Forestier C, Meyer M, Jallat C, Rich C, Malpuech G & De Champs C (1995) Retrospective case-control study of diffusely adhering Escherichia coli and clinical features in children with diarrhea. J Clin Microbiol 33: 19611962.
  • Prehm P, Jann B & Jann K (1976) The O9 antigen of Escherichia coli. Structure of the polysaccharide chain. Eur J Biochem 67: 5356.
  • Pulz M, Matussek A, Monazahian M, Tittel A, Nikolic E, Hartmann M, Bellin T, Buer J & Gunzer F (2003) Comparison of a shiga toxin enzyme-linked immunosorbent assay and two types of PCR for detection of shiga toxin-producing Escherichia coli in human stool specimens. J Clin Microbiol 41: 46714675.
  • Raetz CR & Whitfield C (2002) Lipopolysaccharide endotoxins. Annu Rev Biochem 71: 635700.
  • Ramotar K, Waldhart B, Church D, Szumski R & Louie TJ (1995) Direct detection of verotoxin-producing Escherichia coli in stool samples by PCR. J Clin Microbiol 33: 519524.
  • Ratnayake S, Weintraub A & Widmalm G (1994a) Structural studies of the enterotoxigenic Escherichia coli (ETEC) O153 O-antigenic polysaccharide. Carbohydr Res 265: 113120.
  • Ratnayake S, Widmalm G, Weintraub A & Medina EC (1994b) Structural studies of the Escherichia coli O90 O-antigen polysaccharide. Carbohydr Res 263: 209215.
  • Reis MH, Heloiza M, Affonso T, Trabulsi LR, Mazaitis AJ, Maas R & Maas WK (1980) Transfer of a CFA/I-heat-stable plasmid promoted by a conjugative plasmid in a strain of Escherichia coli of serotype O128ac:H12. Infect Immun 29: 140143.
  • Robins-Browne RM & Hartland EL (2002) Escherichia coli as a cause of diarrhea. J Gastroenterol Hepatol 17: 467475.
  • Robins-Browne RM, Still CS, Miliotis MD, Richardson NJ, Koornhof HJ, Freiman I, Schoub BD, Lecatsas G & Hartman E (1980) Summer diarrhoea in African infants and children. Arch Dis Child 55: 923928.
  • Rundlöf T, Weintraub A & Widmalm G (1996) Structural studies of the enteroinvasive Escherichia coli (EIEC) O28 O-antigenic polysaccharide. Carbohydr Res 291: 127139.
  • Rundlöf T, Weintraub A & Widmalm G (1998) Structural determination of the O-antigenic polysaccharide from Escherichia coli O35 and cross-reactivity to Salmonella arizonae O62. Eur J Biochem 258: 139143.
  • Samuel B (1996) Medical Microbiology, pp. 303–310). The University of Texas Medical Branch at Galveston, Texas.
  • Samuel G & Reeves P (2003) Biosynthesis of O-antigens: genes and pathways involved in nucleotide sugar precursor synthesis and O-antigen assembly. Carbohydr Res 338: 25032519.
  • Sasakawa C, Buysse JM & Watanabe H (1992) The large virulence plasmid of Shigella. Curr Top Microbiol Immunol 180: 2144.
  • Scaletsky IC, Pedroso MZ & Fagundes-Neto U (1996) Attaching and effacing enteropathogenic Escherichia coli o18ab invades epithelial cells and causes persistent diarrhea. Infect Immun 64: 48764881.
  • Scaletsky IC, Fabbricotti SH, Carvalho RL, Nunes CR, Maranhao HS, Morais MB & Fagundes-Neto U (2002) Diffusely adherent Escherichia coli as a cause of acute diarrhea in young children in Northeast Brazil: a case–control study. J Clin Microbiol 40: 645648.
  • Scheutz F (2004) Personal communication.
  • Scheutz F, Cheasty T, Woodward D & Smith HR (2004) Designation of O174 and O175 to temporary O groups OX3 and OX7, and six new E. coli O groups that include Verocytotoxin-producing E. coli (VTEC): O176, O177, O178, O179, O180 and O181. Apmis 112: 569584.
  • Schultsz C, Pool GJ, Van Ketel R, De Wever B, Speelman P & Dankert J (1994) Detection of enterotoxigenic Escherichia coli in stool samples by using nonradioactively labeled oligonucleotide DNA probes and PCR. J Clin Microbiol 32: 23932397.
  • Sengupta P, Bhattacharyya T, Shashkov AS, Kochanowski H & Basu S (1995) Structure of the O-specific side chain of the Escherichia coli O128 lipopolysaccharide. Carbohydr Res 277: 283290.
  • Sixma TK, Kalk KH, Van Zanten BA, Dauter Z, Kingma J, Witholt B & Hol WG (1993) Refined structure of Escherichia coli heat-labile enterotoxin, a close relative of cholera toxin. J Mol Biol 230: 890918.
  • Small PL & Falkow S (1988) Identification of regions on a 230-kilobase plasmid from enteroinvasive Escherichia coli that are required for entry into HEp-2 cells. Infect Immun 56: 225229.
  • Smith HR, Scotland SM & Rowe B (1983) Plasmids that code for production of colonization factor antigen II and enterotoxin production in strains of Escherichia coli. Infect Immun 40: 12361239.
  • Snyder JD, Wells JG, Yashuk J, Puhr N & Blake PA (1984) Outbreak of invasive Escherichia coli gastroenteritis on a cruise ship. Am J Trop Med Hyg 33: 281284.
  • Staaf M, Urbina F, Weintraub A & Widmalm G (1997) Structure determination of the O-antigenic polysaccharide from the enterotoxigenic Escherichia coli (ETEC) O101. Carbohydr Res 297: 297299.
  • Staaf M, Widmalm G, Weintraub A & Nataro JP (1995) Structural elucidation of the O-antigenic polysaccharide from Escherichia coli O44:H18. Eur J Biochem 233: 473477.
  • Staaf M, Urbina F, Weintraub A & Widmalm G (1999a) Structural elucidation of the O-antigenic polysaccharides from Escherichia coli O21 and the enteroaggregative Escherichia coli strain 105. Eur J Biochem 266: 241245.
  • Staaf M, Urbina F, Weintraub A & Widmalm G (1999b) Structure elucidation of the O-antigenic polysaccharide from the enteroaggregative Escherichia coli strain 62D1. Eur J Biochem 262: 5662.
  • Staaf M, Weintraub A & Widmalm G (1999c) Structure determination of the O-antigenic polysaccharide from the enteroinvasive Escherichia coli O136. Eur J Biochem 263: 656661.
  • Stacy-Phipps S, Mecca JJ & Weiss JB (1995) Multiplex PCR assay and simple preparation method for stool specimens detect enterotoxigenic Escherichia coli DNA during course of infection. J Clin Microbiol 33: 10541059.
  • Stevenson G, Neal B, Liu D, Hobbs M, Packer NH, Batley M, Redmond JW, Lindquist L & Reeves P (1994) Structure of the O antigen of Escherichia coli K-12 and the sequence of its rfb gene cluster. J Bacteriol 176: 41444156.
  • Tao J, Feng L, Guo H, Li Y & Wang L (2004) The O-antigen gene cluster of Shigella boydii O11 and functional identification of its wzy gene. FEMS Microbiol Lett 234: 125132.
  • Taylor DN, Echeverria P, Sethabutr O, Pitarangsi C, Leksomboon U, Blacklow NR, Rowe B, Gross R & Cross J (1988) Clinical and microbiologic features of Shigella and enteroinvasive Escherichia coli infections detected by DNA hybridization. J Clin Microbiol 26: 13621366.
  • Thomas LV, Rowe B & Mc Connell MM (1987) In strains of Escherichia coli O167 a single plasmid encodes for the coli surface antigens CS5 and CS6 of putative colonization factor PCF8775, heat-stable enterotoxin, and colicin Ia. Infect Immun 55: 19291931.
  • Tomasz A (ed) (2000) Streptococcus pneumoniae: Molecular Biology and Mechanisms of Disease. Mary Ann Liebert, New York.
  • Torgov VI, Shashkov AS, Jann B & Jann K (1995) NMR reinvestigation of two N-acetylneuraminic acid-containing O-specific polysaccharides (O56 and O24) of Escherichia coli. Carbohydr Res 272: 7390.
  • Torgov VI, Shashkov AS, Kochanowski H, Jann B & Jann K (1996) NMR analysis of the structure of the O88 polysaccharide (O88 antigen) of Escherichia coli O88:K:H25. Carbohydr Res 283: 223227.
  • Unhanand M, Mustafa MM, Mc Cracken GHJr & Nelson JD (1993) Gram-negative enteric bacillary meningitis: a twenty-one-year experience. J Pediatr 122: 1521.
  • Urbina F, Nordmark E-L, Yang Z, Weintraub A, Scheutz F & Widmalm G (2005) Structural elucidation of the O-antigen polysaccharide from the enteroaggregative Escherichia coli strain 180/C3 and its immunochemical relationship with E. coli O5 and O65. Carbohydr Res 340: 645650.
  • Varki A, Cummings R, Esko J, Freeze H, Hart G & Marth J (1999) Essentials of Glycobiology. Cold Spring Harbor Laboratory Press, New York.
  • Vasil'ev VN & Zakharova IY (1976) Structure of the determinant group of the O-specific polysaccharide of E. coli O20:K84:H34 (145). Bioorg Khim 2: 199206.
  • Vasil'ev VN & Zakharova IY (1982) Structure of the O-specific polysaccharides of Escherichia coli Str. O20ab:K84:H34 (145) and O20ac:K61:H according to 13C NMR spectroscopy. Bioorg Khim 8: 120125.
  • Vial PA, Mathewson JJ, DuPont HL, Guers L & Levine MM (1990) Comparison of two assay methods for patterns of adherence to HEp-2 cells of Escherichia coli from patients with diarrhea. J Clin Microbiol 28: 882885.
  • Vinogradov E, Conlan JW & Perry MB (2000) Serological cross-reaction between the lipopolysaccharide O-polysaccharaide antigens of Escherichia coli O157:H7 and strains of Citrobacter freundii and Citrobacter sedlakii. FEMS Microbiol Lett 190: 157161.
  • Weintraub A, Leontein K, Widmalm G, Vial PA, Levine MM & Lindberg AA (1993) Structural studies of the O-antigenic polysaccharide of an enteroaggregative Escherichia coli strain. Eur J Biochem 213: 859864.
  • Whitfield C & Roberts IS (1999) Structure, assembly and regulation of expression of capsules in Escherichia coli. Mol Microbiol 31: 13071319.
  • Widmalm G & Leontein K (1993) Structural studies of the Escherichia coli O127 O-antigen polysaccharide. Carbohydr Res 247: 255262.
  • Wolf MK (1997) Occurrence, distribution, and associations of O and H serogroups, colonization factor antigens, and toxins of enterotoxigenic Escherichia coli. Clin Microbiol Rev 10: 569584.
  • Yildirim H, Weintraub A & Widmalm G (2001) Structural studies of the O-polysaccharide from the Escherichia coli O77 lipopolysaccharide. Carbohydr Res 333: 179183.