Editor: Alex van Belkum
Invasive meningococcal disease associated with a very high case fatality rate in the North-West of Poland
Article first published online: 11 NOV 2005
FEMS Immunology & Medical Microbiology
Volume 46, Issue 2, pages 230–235, March 2006
How to Cite
Skoczyńska, A., Kadłubowski, M., Knap, J., Szulc, M., Janusz-Jurczyk, M. and Hryniewicz, W. (2006), Invasive meningococcal disease associated with a very high case fatality rate in the North-West of Poland. FEMS Immunology & Medical Microbiology, 46: 230–235. doi: 10.1111/j.1574-695X.2005.00027.x
- Issue published online: 11 NOV 2005
- Article first published online: 11 NOV 2005
- Received 18 August 2005; accepted 13 September 2005.
- Neisseria meningitidis;
- fulminant meningococcal sepsis;
- meningococcal meningitis
The aim of the study was to investigate invasive meningococcal disease in the North-West of Poland, associated with a case fatality rate of 42.9%, where among the first 11 cases, eight had fatal outcome. All fatal cases were diagnosed as fulminant meningococcal severe sepsis with Waterhouse–Friderichsen syndrome and disseminated intravascular coagulation. Serotyping and pulsed-field gel electrophoresis analysis revealed that the high case fatality rate was not associated with the dissemination of one epidemic clone. However, six cases, all with good outcomes, were caused by C:2b:(P1.2,P1.5) isolates of the same pulsed-field gel electrophoresis type belonging to ST8 complex/Cluster A4.
Neisseria meningitidis is usually carried asymptomatically in the human nasopharynx but is also responsible for severe invasive meningococcal disease (IMD). Although most cases of IMD appear only sporadically, it may also emerge as outbreaks, large epidemics and pandemics (Cartwright, 1995a; van Deuren et al., 2000; Rosenstein et al., 2001). There are 13 known serogroups, but five of them (A, B, C, Y and W135) are most frequently isolated from invasive infections (van Deuren et al., 2000; Rosenstein et al., 2001). The rate of disease is highest in infancy and declines during childhood. A secondary rise is observed in teenagers and young adults (Roos et al., 1997; Rosenstein et al., 2001). The IMD may be presented clinically as meningitis and/or as a state ranging from mild transitory meningococcemia to a rapidly evolving septic shock with multiple organ dysfunctions. This latter state, known as fulminant meningococcal severe sepsis, is particularly connected with a very high mortality rate (Cartwright, 1995a; Brandtzaeg, 1996; van Deuren et al., 2000; Rosenstein et al., 2001). Thus, despite the significant progress in medicine, IMD is still a serious diagnostic, therapeutic and epidemiological problem worldwide. From April 2003 to March 2004, 21 cases of IMD, including nine fatal cases of fulminant meningococcal septicemia in children, were diagnosed in the West-Pomeranian area of Poland. Thus the aim of the study was to establish epidemiological links and/or the genetic relatedness between the meningococcal isolates responsible for the very high case fatality rate (CFR) in this part of Poland.
Materials and methods
All patients from the West-Pomeranian area with suspected or confirmed IMD (septicemia and/or meningitis) from April 2003 to March 2004 were included in the study. This period was selected because the first fatal case appeared in April 2003 and because a 1-year period is usually used for statistical comparison. It should be noted that, after the selected period and until the end of 2004, only four cases (including one fatal) of IMD were reported in this area. The West-Pomeranian area (22 896 km2), with Szczecin as its capital, is located on the north-west coast of Poland, bordering Germany. The total population of the region is 1 696 073, including 45 862 children less than 4 years of age. The study was performed on all collected N. meningitidis patients' isolates (n=12). Meningococcal serotyping was performed twice by the whole-cell enzyme-linked immunosorbent assay (ELISA) method, as previously described (Abdillahi & Poolman, 1987). Minimal inhibitory concentrations (MICs) of penicillin G (Sigma-Aldrich Chemie, Steinheim, Germany) were assessed by the agar dilution method on Mueller–Hinton blood agar (Beckton Dickinson, Le Pont de Claix, France) according to National Committee for Clinical Laboratory Standards (NCCLS) guidelines (National Committee for Clinical Laboratory Standards, 2004). The isolates with MIC ≤0.06 μg mL−1 were regarded as susceptible to penicillin. The relatedness among isolates was evaluated by restriction fragment length polymorphism of SpeI-digested (MBI Fermentas, Vilnius, Lithuania) total DNA analysis, using pulsed-field gel electrophoresis (PFGE)(Verdu et al., 1996). The isolates were classified into PFGE types according to the interpretive criteria proposed by Tenover et al. (1995). PFGE types representing identical PFGE patterns were designated by the same letter and Arabic number (indistinguishable isolates). Patterns with differences of no more than three bands (closely related) were designated by the same letter and different Arabic number (the same PFGE type, different subtype). PFGE patterns showing differences of four to six bands were named as different PFGE types (different letters), but were reported as possibly related. PFGE patterns with differences of more than six bands were labeled by different letters. Multilocus sequence typing (MLST) technique for N. meningitidis typing was carried out as described previously (Maiden, 1998; Feavers et al., 1999). Alleles and sequence types (STs) were assigned using the MLST database (http://pubmlst.org/neisseria). If the culture was negative, available clinical materials (blood, cerebrospinal fluid and/or tissue samples) were collected in vivo or post mortem from patients with suspected IMD. The DNA isolated from these samples was used for polymerase chain reactions to identify N. meningitidis species and serogroup (Taha, 2000).
During the period studied, there were 21 cases of confirmed or suspected IMD in the West-Pomeranian area. One case was excluded, because it concerned a foreigner with the IMD onset one day after arrival in Poland. The epidemiological links between cases were not established. The distribution of IMD cases in the West-Pomeranian area according to their sequence of occurrence is presented in Fig. 1. Although the total morbidity was 1.24 per 100 000, in the population of children under 4 years of age it was 22 times higher, with the value 28.35 per 100 000. A total CFR was 42.86%, but among the first 11 cases, eight were fatal. All the fatal cases (n=9) were diagnosed as meningococcal septicemia and, except cases 11 and 18, developed very rapidly, progressing to death in 3–9 h after admission to the hospital. The autopsy results of all fatal cases indicated Waterhouse–Friderichsen syndrome and disseminated intravascular coagulation. The CFR connected with septicemia was 69.23%. With the exception of two fatal cases of 16-year-old boys, septicemia developed only in children less than 4 years old. Seven of the fatal cases affected male patients. The clinical diagnosis was particularly difficult in two patients. One of them (case 2) was first seen at home by an emergency doctor because of abdominal pain. After 5 h, it was necessary to call the emergency service again; the patient was then transported by helicopter to a regional hospital, where he died 50 min after admission. The other patient with meningitis (case 5) was sent home after visiting a doctor, because his high temperature and vomiting were taken as side effects of a vaccination against diphtheria, tetanus and pertussis, which he had received one day earlier. On the following day, this patient came back to the hospital with fully symptomatic meningitis.
In three of the 21 cases only a clinical diagnosis was made, and in one case Gram-negative diplococci were observed in a Gram smear from blood. Meningococcal serogroups responsible for the remaining cases of IMD were confirmed either by culture or PCR (n=4): W135 (n=1), C (n=8) and B (n=8). All the patients' isolates were susceptible to penicillin G, with MIC values ranging from ≤0.0075 to 0.06 μg mL−1. Serotyping, PFGE and MLST analyses revealed that the high CFR in this region was not associated with the emergence of only one epidemic strain of N. meningitidis. However, six cases (four of meningitis and two of septicemia) with good outcomes were caused by isolates of the same PFGE type A, with two subtypes (A1 and A2, differing from A1 by one band) and phenotype C:2b:P1.2,P1.5 (one isolate of PFGE type A1 had phenotype C:2b:P1.16). All of these six isolates belonged to sequence type ST8. Among the remaining six isolates, two belonged to ST3698 and one to ST2177, which is a single variant locus of ST3698 in the pdh locus. Two isolates of ST 3698 responsible for fatal outcome could represent capsule switching, in view of the fact that they belonged to different serogroups, B and C. Three other isolates belonged to three different STs, of which two, ST4967 and ST4969, are new STs found during this study. Patients' data and the typing results of the isolates are presented in Table 1.
|Case||Onset||Age||Sex||Diagnosisa||Outcome||Microbiological identification||Phenotype||PFGE type||Allelic profile||MLST type|
|1||23 April 2003||3||f||Septicemia||Dead||Not established||—||—||—||—|
|2||2 June 2003||16||m||Septicemia||Dead||Diplococci||—||—||—||—|
|3||25 June 2003||16||m||Septicemia||Dead||Nmb W135 (pm)c||—||—||—||—|
|4||6 September 2003||2||m||Septicemia||Dead||Nm C||C:NT:NST||B1||7-106-10-17-10-13-9||3698|
|5||9 October 2003||4/12||m||Meningitis||Alive||Nm B||B:NT:P1.6||C||7-106-10-17-10-6-9||2177|
|6||11 October 2003||6/12||m||Septicemia||Dead||Not established||—||—||—||—|
|7||21 October 2003||3 weeks||m||Septicemia||Dead||Nm B (pm)||—||—||—||—|
|8||26 October 2003||52||m||Meningitis||Alive||Nm B||B:22:P1.14||D||7-8-10-26-10-11-16||4803|
|9||31 October 2003||42||m||Meningitis||Alive||Nm B||B:4:NST||E||9-16-6-17-9-11-44||4969d|
|10||10 November 2003||7/12||f||Septicemia||Dead||Nm B||B:NT:P1.10||F||7-17-378d-19-10-1-2||4967d|
|11||30 November 2003||18/12||m||Septicemia||Dead||Nm B||B:NTP1.6||B2||7-106-10-17-10-13-9||3698|
|12||25 December 2003||3||f||Meningitis||Alive||Nm C||C:2b:P1.2,1.5||A1||2-3-7-2-8-5-2||8|
|13||1 January 2004||43||f||Meningitis||Alive||Nm C||C:2b:P1.2,1.5||A2||2-3-7-2-8-5-2||8|
|14||2 January 2004||69||m||Meningitis||Alive||Nm Be||—||—||—||—|
|15||5 January 2004||16||f||Meningitis||Alive||Nm C||C:2b:P1.2,1.5||A1||2-3-7-2-8-5-2||8|
|16||1 February 2004||16||m||Meningitis||Alive||Nm C||C:2b:P1.2,1.5||A1||2-3-7-2-8-5-2||8|
|17||10 February 2004||2||m||Septicemia||Alive||Nm C (PCR)f||—||—||—||—|
|18||20 February 2004||3/12||m||Septicemia||Dead||Nm B (PCR)||—||—||—||—|
|19||26 February 2004||1||f||Septicemia||Alive||Not established||—||—||—||—|
|20||1 March 2004||3||m||Septicemia||Alive||Nm C||C:2b:P1.2,1.5||A1||2-3-7-2-8-5-2||8|
|21||9 March 2004||18/12||m||Septicemia||Alive||Nm C||C:2b:P1.16||A1||2-3-7-2-8-5-2||8|
A sudden increase in morbidity and mortality due to IMD in a specific area has often been connected with the spread of a particular meningococcal clone (Jelfs et al., 2000; Tyrrell et al., 2002). Analysis of the isolates collected in the West-Pomeranian area shows that the high CFR was not related to the spread of one epidemic N. meningitidis strain. Additionally, the epidemiological links between cases were not established. This situation is not surprising for the IMD, because transmission of meningococcal isolates is conducted mostly by asymptomatic carriers (Broome, 1986). However, six cases in the studied area, all with good outcomes, out of total of eight serogroup C meningococci, were caused by isolates of the same PFGE type and phenotype C:2b:P1.2,P1.5. All of these belonged to ST8 complex/Cluster A4, which is one of the two hypervirulent lineages responsible for most serogroup C IMD cases worldwide (Stefanelli et al., 2004) (http://pubmlst.org/neisseria). Meningococci of the C:2b:P1.2,P1.5 phenotype, although described in many countries as the cause of only sporadic cases, occurred as the epidemic ones in others (Wang et al., 1993; Alcala et al., 2002; Canica et al., 2004; Stefanelli et al., 2004). For example, the frequency of C:2b:P1.2,P1.5 among group C meningococci in Spain increased from 4.6% in 1993 to 65% in 1996, and resulted in a mass immunization campaign against serogroup C meningococci in this country (Alcala et al., 2002). An apparent rise in the prevalence of C:2b:P1.2,P1.5 and C:2b:P1.5 meningococci was also observed in Portugal and Italy, where additionally almost 28% and 78.4% of them, respectively, showed an intermediate resistance to penicillin (Canica et al., 2004; Stefanelli et al., 2004). This is in contrast to the results of this study, where all meningococcal isolates, including these of the C:2b:P1.2,P1.5 phenotype, were fully susceptible to penicillin. However, knowing the other countries' experience and observing the continuing dominance of C:2b:P1.2,P1.5 meningococci in the West-Pomeranian area, there is a need for cautious surveillance of meningococci of such phenotype in this particular area and in Poland.
Excepting the group of isolates of ST8 complex/Cluster A4, only one isolate with ST4803 belonged to already known clonal complex ST18 which was found in Poland previously, in 1997 (http://pubmlst.org/neisseria). This clonal complex, which includes isolates, mostly of serogroup B, responsible for invasive disease as well as for carriage state, has already been described in many countries, including European, American and African ones (http://pubmlst.org/neisseria).
An interesting finding was noted regarding two isolates responsible for case 4 and 11. Both isolates were characterized by ST3698 but they belonged to two different serogroups, C and B. Although capsular switching as a result of the horizontal transfer of siaD genes has been already described in N. meningitidis isolates in vitro and in vivo, this is the first report of capsule replacement in Polish meningococci (Frosch & Meyer, 1992; Swartley et al., 1997; Kertesz et al., 1998; Alcala et al., 2002; Stefanelli et al., 2003). It was not possible to establish the direction of the capsular switching, because even in this study we found the isolate of ST2177, a single variant locus of ST3698, with the phenotype B:NT:P1.6. On the other hand, the isolate of ST 3698 with phenotype C:NT:NST was found in the neighboring Czech Republic (http://pubmlst.org/neisseria). Because there is no vaccine available against serogroup B meningococci, the C to B capsular switching may have a greater impact for public health, especially if it expresses the same epidemic potential as its serogroup C variant. The phenomenon of the capsule switching has been mostly reported after mass vaccination campaigns; however, it is also known that genetic variants of different serogroups may be produced randomly in a meningococcal population, independent of a vaccination pressure (Frosch & Meyer, 1992; Alcala et al., 2002). This may be the case in our study, because in Poland a mass vaccination against serogroup C meningococci was never implemented.
The direct comparison of morbidity and CFR obtained during this study, which involved cases of both meningitis and septicemia, with data from previous years from the West-Pomeranian area, is difficult because only meningitis cases were notifiable in Poland until the fall of 2003. However, fatal cases have been reported in the much stricter death notification system. The available data have shown that in years 2000, 2001 and 2002, there were five (0.29 per 100 000), one (0.06 per 100 000) and eight cases (0.47 per 100 000) of meningococcal meningitis notified in the West-Pomeranian area, respectively, and three, one and two deaths from IMD, respectively (National Institute of Hygiene and Chief Sanitary Inspectorate, 2001–2004). Although the general morbidity in the studied period was not high, and although it corresponded to mean rate for industrialized countries (1–3 per 100 000), the observed CFR was exceptionally high and remarkable (van Deuren et al., 2000). The high CFR in the West-Pomeranian region may be partially explained by an unusually high percentage, almost 62%, of cases diagnosed as septicemia. Generally, the most common clinical manifestation of IMD is meningitis, which is connected to a relatively low mortality rate, from 1% to 5% (Cartwright, 1995a; van Deuren et al., 2000). In contrast, septicemia, commonly accounting for 15–20% of all the IMD cases, is associated with a much higher mortality rate, from 20% to 80%. What is more worrying is that about 50% of patients are dying within 24 h after the first symptoms appear (Cartwright, 1995a; van Deuren et al., 2000; Rosenstein et al., 2001).
Excluding the hypothesis that the very high CFR in our study was associated with an unusually elevated rate of septicaemia cases connected with higher mortality, there are also other possible factors. Although there is still no explanation why acquisition of pathogenic meningococci induced invasive disease in some individuals but not in others harboring the same isolates, there are studies which show the very important role of host individual features in meningococcal infections (Caugant et al., 1994; Cartwright, 1995b; Hibberd et al., 1999; Emonts et al., 2003). In addition, the epidemiology of meningococcal disease is unpredictable, and the knowledge of variations in meningococcal virulence is still insufficient and requires further extensive studies (Cartwright, 1995b).
An additional explanation for such a high CFR may be the fact that early recognition of septicemia, in contrast to meningitis, is very difficult even for highly experienced physicians (Cartwright, 1995a; van Deuren et al., 2000; Rosenstein et al., 2001). The patients may be conscious until the late phase of the disease, and symptoms are very often absent or confusing, which could delay the administration of antibiotics crucial for a good outcome. Sometimes patients in the earliest stage of septicemia are sent home after their first visit to the emergency room because the initial signs are mild and noncharacteristic, but they often return a few hours later in a life-threatening condition (Brandtzaeg, 1996; van Deuren et al., 2000). That was the situation observed during our study.
The situation in the studied area alerted doctors, epidemiologists and the public, who for the first time witnessed the very devastating nature of IMD in Poland. At first, most cases in the studied area were caused by serogroup B meningococci, so a massive vaccination was not considered, although it was recommended for close contacts in cases of serogroup C infection. However, in the event of an increasing prevalence of serogroup C infections in this area, mass immunoprophylaxis should be considered and recommended, especially in the children at highest risk.
The high number of septicemia cases in the studied area also accelerated changes in the Polish notification system. Until recently, only cases of meningococcal meningitis were reported. Since the fall of 2003, notification of all IMD cases, both meningitis and septicemia, has been compulsory in Poland.
We thank all clinicians, microbiologists and epidemiologists from the West-Pomeranian area for cooperation and providing isolates with clinical data. We thank Anna Klarowicz for her excellent technical assistance.
We acknowledge the use of the meningococcal MLST database, which is located at University of Oxford and is funded by the Wellcome Trust and European Union.
This study was partially funded by a grant from the Polish Committee for Scientific Research (2P05D07728).
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