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Keywords:

  • Enterocolitis, Necrotizing [*prevention & control];
  • Infant, Newborn;
  • Infant, Premature;
  • Probiotics [*therapeutic use];
  • Randomized Controlled Trials as Topic;
  • Humans

Abstract

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Background

Necrotizing enterocolitis (NEC) and nosocomial sepsis are associated with increased morbidity and mortality in preterm infants. Through prevention of bacterial migration across the mucosa, competitive exclusion of pathogenic bacteria, and enhancing the immune responses of the host, prophylactic enteral probiotics (live microbial supplements) may play a role in reducing NEC and associated morbidity.

Objectives

To compare the efficacy and safety of prophylactic enteral probiotics administration versus placebo or no treatment in the prevention of severe NEC and/or sepsis in preterm infants.

Search strategy

The standard search strategy for the Cochrane Neonatal Review Group was performed by two review authors. Searches were made of MEDLINE (1966 to December 2006), EMBASE (1980 to December 2006), Cochrane Library Controlled Trials Register (CENTRAL, The Cochrane Library Issue 3, 2006), and abstracts of annual meetings of the Society for Pediatric Research (1995 - 2006). The authors of published articles were contacted.

Selection criteria

Only randomized or quasi-randomized controlled trials that enrolled preterm infants < 37 weeks gestational age and/or < 2500 g birth weight were considered. Trials were included if they involved enteral administration of any live microbial supplement (probiotics) and measured at least one prespecified clinical outcome.

Data collection and analysis

Standard methods of the Cochrane Collaboration and its Neonatal Group were used to assess the methodologic quality of the trials. Retrieved articles were assessed for eligibility and data abstracted independently by two review authors. Where data were incomplete, the primary investigator were contacted for further information and clarification. Where appropriate, data of individual trials were combined using meta-analytic techniques to provide a pooled estimate of effect assuming a fixed effect model.

Main results

Nine eligible trials randomizing 1425 infants were included. Included trials were highly variable with regard to enrollment criteria (i.e. birth weight and gestational age), baseline risk of NEC in the control groups, timing, dose, formulation of the probiotics, and feeding regimens. Data regarding extremely low birth weight infants (ELBW) could not be extrapolated. In a meta-analysis of trial data, enteral probiotics supplementation significantly reduced the incidence of severe NEC (stage II or more) [typical RR 0.32 (95% CI 0.17, 0.60)] and mortality [typical RR 0.43 (95% CI 0.25, 0.75]. There was no evidence of significant reduction of nosocomial sepsis [typical RR 0.93 (95% CI 0.73, 1.19)] or days on total parenteral nutrition (TPN) [WMD -1.9 (95% CI -4.6, 0.77)]. The included trials reported no systemic infection with the probiotics supplemental organism. The statistical test of heterogeneity for NEC, mortality and sepsis was insignificant.

Authors' conclusions

Enteral supplementation of probiotics reduced the risk of severe NEC and mortality in preterm infants. This analysis supports a change in practice in premature infants > 1000 g at birth. Data regarding outcome of ELBW infants could not be extracted from the available studies; therefore, a reliable estimate of the safety and efficacy of administration of probiotic supplements cannot be made in this high risk group. A large randomized controlled trial is required to investigate the potential benefits and safety profile of probiotics supplementation in ELBW infants.

Plain Language Summary

Probiotics for prevention of necrotizing enterocolitis in preterm infants

Necrotizing Enterocolitis (NEC) is a serious disease that affects the bowel of premature infants in the first few weeks of life. Although the cause of NEC is not entirely known, milk feeding and bacterial growth play a role. Probiotics (dietary supplements containing potentially beneficial bacteria or yeast) have been used to prevent NEC. Our review of studies found that the use of probiotics reduces the occurrence of NEC and death in premature infants born less than 1500 grams. There is insufficient data with regard to the benefits and potential adverse effects in the most at risk infants less than 1000 grams at birth.


Background

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Necrotizing enterocolitis (NEC) is the most common serious acquired disease of the gastrointestinal tract in preterm infants (Lee 2003). It is characterized by bowel wall necrosis of various length and depth. Bowel perforation occurs in one third of the affected infants (Kafetzis 2003). Although 5 - 25% of cases occur in term infants, it is primarily a disease of preterm infants, with the majority of cases occurring in very low birth weight infants (infants with birth weight < 1500 g) (Kosloske 1994). NEC is categorized into three different stages, with clinical symptoms varying from feeding intolerance to severe cardiovascular compromise, coagulopathy, and peritonitis with or without pneumoperitoneum (Bell 1978).

The incidence of NEC varies among countries and neonatal centers. It has been reported to affect up to 10% of very low birth weight infants (VLBW) (Kosloske 1994). VLBW infants with NEC have a mortality rate up to 20% (Caplan 2001; Holman 1997). Approximately 27 - 63% of affected infants require surgical intervention (Lee 2003). Strictures, primarily in the colon, occur in more than one third of affected infants (Ricketts 1994). Increased rate of total parenteral nutrition (TPN) related complications and extended hospitalization have been reported (Bisquera 2002). Recent data from the National Institute of Child Health and Human Development Network (NICHD) suggest an increase in neurodevelopmental impairment rates among infants with NEC and sepsis (Stoll 2004).

The pathogenesis of NEC remains incompletely understood. NEC most likely represents a complex interaction of factors causing mucosal injury (Neu 1996). It is speculated that NEC occurs with the coincidence of two of the following three pathologic events; intestinal ischemia, colonization of the intestine by pathologic bacteria, and excess protein substrate in the intestinal lumen (Kosloske 1984; La Gamma 1994). Bacterial colonization is necessary for the development of NEC (Kosloske 1990; Musemeche 1986). When compared to term infants, VLBW infants at risk of NEC have abnormal fecal colonization, demonstrate a paucity of normal enteric bacterial species, and have delayed onset of bacterial colonization (Goldmann 1978; Gewolb 1999).

Nosocomial infection is also a frequent complication in VLBW infants. Data from the NICHD Network demonstrated that as many as 25% of these infants have at least one or more positive blood cultures, and 5% have positive cerebrospinal fluid cultures over the course of their hospitalization (Stoll 1996). Late onset sepsis is associated with an increased risk of death, neonatal morbidity and prolonged hospitalization (Stoll 2002a; Stoll 2002b).

Probiotic bacteria are live microbial supplements that colonize the gastrointestinal tract and potentially provide benefit to the host (Millar 2003). The most frequently used probiotics are lactobacillus and Bifidobacterium. There is increasing interest in the potential health benefits of proactive colonization of the gastrointestinal tract of preterm infants (Millar 2003). Potential mechanisms by which probiotics may protect high risk infants from developing NEC and/or sepsis include increased barrier to migration bacteria and their products across the mucosa (Orrhage 1999; Mattar 2001), competitive exclusion of potential pathogens (Reid 2001), modification of host response to microbial products (Duffy 2000), augmentation of IGA mucosal responses, enhancement of enteral nutrition that inhibit the growth of pathogens, and up-regulation of immune responses (Link-Amster 1994). There is a theoretical risk of bacteremia secondary to enterally administered probiotics strains, though few data support this concern. Bacillus species administered as probiotics were reported to be associated with invasive disease in target populations (Richard 1988).

Objectives

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

The primary objective was to compare the effectiveness and safety of prophylactic enteral probiotics administration versus placebo or no treatment in the prevention of severe (stage II or more) NEC and/or sepsis in preterm infants. The secondary objective was to conduct a subgroup analysis to investigate the effect of probiotics in extreme low birth weight infants (infants with birth weight < 1000 g).

Methods

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Criteria for considering studies for this review

Types of studies

Only randomized and quasi-randomized controlled trials were included.

Types of participants

Preterm infants < 37 weeks and/or birth weight < 2500 g.

Types of interventions

Enteral administration of any live microbial supplement (probiotics) at any dose for more than seven days compared to placebo or no treatment.

Types of outcome measures

Primary outcomes

  • Severe NEC (stage II or more) as per Bell's criteria (Bell 1978; Walsh 1986), diagnosed prior to discharge.

  • Nosocomial sepsis, defined as positive blood or cerebrospinal fluid cultures taken beyond 5 days of age.

Secondary outcomes

  • All cause neonatal mortality

  • Any NEC (according Bell's criteria)

  • The composite of nosocomial sepsis or NEC or death

  • Systemic infection with the supplemented organism

  • Duration of total parenteral nutrition (days)

  • Time to establish full enteral feeds (days)

  • Duration of hospitalization (days)

  • Neurodevelopmental impairment i.e. rates of cerebral palsy, cognitive delay, deafness, blindness or their composite reported at 18 months corrected age or later.

Search methods for identification of studies

The standard search strategy for the Cochrane Neonatal Review Group was used. Randomized and quasi-randomized controlled trials that compared enteral probiotics to placebo or no treatment in premature infants were identified from OVID MEDLINE-National Library of Medicine (1966 to December 2006) using the following subject headings (MeSH) and text word terms: "neonate(s), newborn(s), infant(s), probiotics, lactobacillus, bifidobactrium, saccharomyces and publication type 'controlled trial'. No language restrictions were applied.

Other databases were searched including: EMBASE (1980 to December 2006), Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2006). Two review authors performed the electronic database search independently. A manual search of the abstract books published from the Society of Pediatric Research (SPR) and the European Society of Pediatric Research (ESPR) for the period of 1998 - 2006 were performed. Additional citations were sought using references in articles retrieved from searches. Subject experts were contacted to identify the unpublished and ongoing studies. Authors of the published trials were contacted to clarify or provide additional information. Two review authors independently screened candidate articles to check the eligibility for inclusion in the review.

Data collection and analysis

Study Quality and Data extraction

Standard methods of the Cochrane Collaboration and the Neonatal Review Group were used to assess the methodological quality (validity criteria) of the trials. For each trial, information was sought regarding the method of randomization, blinding and reporting of all outcomes of all the infants enrolled in the trial. Each criteria was assessed as yes, no, can't tell. Retrieved articles were assessed for eligibility and data abstracted independently by two review authors. Discrepancies were resolved by discussion and consensus. Where data were incomplete, the primary investigator was contacted for further information and clarification.

Data Analysis

For dichotomous outcomes, relative risk (RR) and its associated confidence interval were calculated. For continuous outcomes, treatment effect was expressed as mean difference and its calculated standard deviation. If appropriate, meta-analysis of pooled data was performed assuming a fixed effect model. Review Manager 4.2.7 software was used for statistical analysis. A subgroup analysis to investigate the effect of probiotics in extreme low birth weight (ELBW) infants was planned. A sensitivity analysis was carried out to assess the effect of trials methodological quality on results of the meta-analysis.

Heterogeneity was defined as a significant test of heterogeneity (p < 0.1) and differences in the treatment effects across studies. Tests for between-study heterogeneity (including the I2 test) were applied. If noticed, possible sources of heterogeneity were examined, including differences in the type or dose of probiotics used, the population under study (VLBW vs. ELBW infants), and the quality of the study.

Results

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Description of studies

See: Characteristics of included studies; Characteristics of excluded studies.

Initial electronic search yielded 98 MEDLINE and 93 EMBASE potentially relevant citations. After reading abstracts, 12 articles were identified as potentially relevant. Review of full text articles identified ten studies comparing probiotic administration to control treatment. Two studies (Stansbridge 1993; Agarwal 2003) were excluded since no clinical outcomes were reported. A decision regarding the inclusion of one study published in German (Uhlemann 1999) was deferred till further assessment. This study included infants between 25 - 42 weeks gestation. Attempts were made to contact the author in order to extract data relevant to preterm infants alone. Two review authors, independently checked eligibility of included studies. The inter-observer agreement was excellent (kappa = 1.0). Two studies (Stansbridge 1993; Agarwal 2003) were excluded for reasons outlined in the table below. Details of the included studies are shown in the table "Characteristics of Included Studies".

Participants

Full details of included studies are given in the table "Characteristics of Included Studies". The nine included studies reported outcomes on 717 infants treated with probiotics and 708 control infants. While all studies enrolled infants < 37 weeks and/or birth weight < 2500 g, entry criteria varied between studies. Reuman 1986, Kitajima 1997, Lin 2005, Bin-Nun 2005 and Manzoni 2006 enrolled infants based on birth weight criteria. On the other hand, Millar 1993 and Costalos 2003 enrolled infants based on their gestational age. Dani 2002 utilized both criteria to enroll infants. None of the included studies limited their enrollment to ELBW infants.

Intervention

Included studies randomized infants to different preparations and dosages of probiotics. While Reuman 1986, Millar 1993, Dani 2002 and Manzoni 2006 administered Lactobacillus species to the intervention groups; Kitajima 1997 and Li 2004 utilized the Bifidobacterium species and Costalos 2003 utilized Saccharomyces boulardii. Lin 2005 and Bin-Nun 2005 used a mixture of two to three species of probiotics (L acidophilus - B infantis, and Lactobacillus bifidus-streptococcus thermophillus-bifidobactrium infantis, respectively).

The time of initiation and duration of therapy was different among included studies. Probiotics were administered either during the first 24 h of life (Reuman 1986; Kitajima 1997; Li 2004), at the time of the first feed (Millar 1993; Dani 2002; Lin 2005), or during the first week when enteral feeds were tolerated (Costalos 2003, Manzoni 2006). The duration of probiotics administration varied from two weeks (Reuman 1986), 28 and 30 days (Kitajima 1997; Costalos 2003 respectively), or until discharge (Dani 2002; Li 2004; Lin 2005; Manzoni 2006).

Outcomes

The major outcomes reported in included studies were severe stage II-III NEC (Dani 2002; Costalos 2003; Lin 2005; Bin-Nun 2005; Manzoni 2006), all causes mortality (Reuman 1986; Dani 2002; Lin 2005; Bin-Nun 2005; Manzoni 2006) and sepsis (Millar 1993; Costalos 2003; Dani 2002; Lin 2005; Bin-Nun 2005; Manzoni 2006). Weight gain was reported in three studies (Reuman 1986; Millar 1993; Costalos 2003) using different measurement scales. Only one study reported data on apnea (Kitajima 1997). None of the studies reported data on the long-term neurosensory outcomes of enrolled infants.

Risk of bias in included studies

Details of included studies are presented in the table "Characteristics of Included Studies". The methodologic details of the studies were extracted from the published data and by contacting the primary author. However, a response was only received from one primary author (Dani 2002).

  • Bin-Nun 2005: This was a single centre study. Infants less than 1500 g were randomized to receive either probiotics mixture (Lactobacillus bifidus, streptococcus thermophillus, and bifidobactrium infantis) or placebo. Information regarding allocation concealment was not specified, intervention was masked, and blinding of outcome assessment was not specified. Of note, this trial was published in an abstract form on two previous occasions at the Society of Pediatrics Research (SPR 2003, 2005) with different inclusion criteria and clinical outcomes, which suggests a change in the a priori specified criteria and multiple looks at the trials results.

  • Costalos 2003: This was a single center study. Infants were randomized to receive either enteral probiotics (Saccharomyces boulardii) added to preterm formula or the same formula with maltodextrins. Allocation concealment was apparently adequate. Intervention and outcome assessment were masked. All infants were accounted for in the final results. There was a discrepancy with regard to the infants enrolled in both groups (51 in the treatment group and 36 in the control). The author presented no explanation of whether this discrepancy was a result of imbalance in the randomization process or a loss to follow-up.

  • Dani 2002: This was a multicenter study. Infants were randomized to receive either enteral probiotics (Lactobacillus GG) or placebo. Allocation was adequately concealed. The intervention was masked. All enrolled infants were accounted for and outcome measurement was blinded.

  • Kitajima 1997: This was a single center study. 91 infants were randomized to receive enteral probiotics (Bifidobacterium breve) or control. It was unclear whether allocation was concealed, intervention blinded, or the outcome assessment was blinded. Not all enrolled infants accounted for the final results (six infants excluded for various reasons).

  • Li 2004: This was a single center study. Infants were randomized in three groups to receive either enteral probiotics (Bifidobacterium breve) (group A, B) or control (group C). Allocation concealment was not described. It was unclear whether the intervention or outcome assessment were blinded and whether all infants were included its final results.

  • Lin 2005: This was a single centre study, infants less than 1500 g were randomized to either probiotics (Infloran® - L acidophilus and B infantis) or to a control group (breast milk only). Allocation was adequately concealed. Intervention was masked (except for investigators and breast milk team). All enrolled infants were accounted for. Outcomes measurement was blinded.

  • Manzoni 2006: This was a single centre study, infants less than 1500 g were randomized to either probiotics (Dicoflor Lactobacillus casei) or to a control group (breast or donor milk only). Although authors utilized computer generated randomization, allocation concealment was not described. Intervention was masked from human bank and microbiology workers however unclear whether care givers are masked or not. All enrolled infants were accounted for. Blinding of outcomes measurement was reported.

  • Millar 1993: This was a single center study. Twenty infants were randomized to receive either enteral probiotics (Lactobacillus GG) or control. The intervention was masked. All infants enrolled were accounted for. It was unclear whether the outcome assessment was blinded or not.

  • Reuman 1986: This was a single center study. Three groups of infants were randomized to receive either enteral probiotics (Lactobacillus) or control. Randomization and allocation concealment were clearly inadequate. The intervention was double masked. All infants enrolled were accounted for and outcome assessment was blinded.

Effects of interventions

PROBIOTICS VS. CONTROL (COMPARISON 01):

Severe stage II-III necrotizing enterocolitis (Outcome 01.01):

Five studies reported on severe stage II-III NEC (Dani 2002; Costalos 2003; Lin 2005; Bin-Nun 2005; Manzoni 2006). The administration of prophylactic probiotics significantly reduced the incidence of severe stage II -III NEC [typical RR 0.32 (95% CI 0.17, 0.60); typical RD -0.04 (95% CI -0.06,-0.02), NNT 25]. Data pertaining to the most vulnerable infants (ELBW) could not be abstracted from the included studies.

Mortality (Outcome 01.02):

Five studies reported on mortality (Reuman 1986; Dani 2002; Lin 2005; Bin-Nun 2005; Manzoni 2006). The number of deaths was significantly lower in the probiotics group [typical RR 0.43 (95% CI 0.25, 0.75); typical RD -0.04 95% CI (-0.06,-0.01), NNT 25]. Two studies (Bin-Nun 2005; Dani 2002) reported NEC- related mortality (a post hoc analysis). A total of five deaths were attributed to NEC in the control group, while no NEC-related deaths occurred in the probiotics arm of both studies [typical RR 0.17 (95% CI 0.02, 1.37). Although the trend favors the probiotics group with regard to NEC-related mortality, one can not make a strong conclusion due to the small number of events reported in the trials.

Sepsis (Outcome 01.03):

Five studies reported on sepsis (Bin-Nun 2005; Dani 2002; Millar 1993; Costalos 2003; Lin 2005; Manzoni 2006). There was no significant difference among both groups in the rate of culture proven sepsis [typical RR 0.93 (95% CI 0.73, 1.19).

Days on total parenteral nutrition (Outcome 01.04):

Two studies reported this outcome. No statistical difference was found in either of the studies. Dani 2002 reported a mean of 12.8 (13.9) days in the probiotics group, and a mean of 14.7(18.7) days in the control group [WMD -1.9 (-4.6, 0.77)]. Lin 2005 reported a mean of 14.7(5.7) days in the probiotics group and 13.9 (5.0) days in the control group [WMD 0.80 (-0.3, 1.9)]. Due to the significant test of heterogeneity, these results were not pooled.

Hospitalization days (Outcome 01.05):

Three studies reported this outcome. Over all there were no statistical differences among groups with regard to length of hospital stay. Reuman 1986 reported a mean (SD) of 59.4 (56.4) days, 38.7 (30.6), Millar 1993 reported A median (range) of 50 (23 - 136), 42.8 (19 - 114), and Lin 2005 reported a mean (SD) of 46.7 (27.1), 46.5 (26.10) total hospitalization days for both probiotics and controls respectively. Due to the significant test of heterogeneity, these results were not pooled.

Weight gain (Outcome 01.06):

Three studies (Reuman 1986; Millar 1993; Costalos 2003) reported weight gain results. No significant statistical difference in weight gain among study groups was observed. Due to the use of different scales i.e. g/week, g/day and g/kg/day, these results were not pooled.

The composite of death or severe NEC or sepsis (Outcome 01.07):

Only one study reported this outcome (Lin 2005). Probiotics significantly reduced the incidence of this composite [typical RR 0.54 (95% CI 0.37, 0.79)].

Systemic infection with the supplemented organism

None of the included studies reported a systemic infection caused by the supplemented probiotics organisms.

Neurodevelopmental impairment

No data were reported.

A subgroup analysis to demonstrate the effect of probiotics administration in ELBW infants was not performed since data pertains to this high risk group could not be extracted from the included studies.

Discussion

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Our review examined the evidence of probiotics efficacy in premature infants in eight randomized controlled trials. Only two studies enrolled large number of infants and reported adequate allocation concealment and blinding of intervention (Dani 2002; Lin 2005). All included trials evaluated probiotics use in premature infants. However, included trials were highly variable with regard to enrollment criteria (i.e. birth weight and gestational age), baseline risk of NEC in the control groups, timing, dose, formulation of the probiotics used and feeding regimens.

Enteral administration of probiotics significantly decreased the incidence of severe stage II-III NEC. The direction of this effect is consistent and homogenous among included studies. The benefit of enteral probiotics use in reducing the incidence of NEC in the highest risk population (Extreme Low Birth Weight infants <1000 g at birth) could not be evaluated in a sub-group analysis.

One recent trial of sufficient power (Lin 2005) showed a benefit of probiotics on prevention of sepsis. However, this effect did not reach statistical significance in our pooled estimate of all trials reporting this outcome.

Although five studies reported death as an outcome, only two (Lin 2005, Dani 2002) were of high quality. This review demonstrated a significant reduction in mortality in the probiotics group. Only two studies addressed NEC-related deaths and these events were rare (Bin-Nun 2005; Dani 2002). Therefore, this outcome was not sufficiently evaluated. This review showed no significant effect of probiotics on the number of days on TPN, hospitalization days, weight gain or apnoea.

There are case reports of systemic infections caused by probiotics organisms in the biomedical literature. The included studies showed no evidence of such an adverse effect. The use of probiotics was described as safe and well tolerated in the trials included. Although the data thus far is reassuring, the number of infants included in this review could not reliably assess this outcome.

This review utilized a very thorough and comprehensive search strategy; all attempts were made to minimize the potential of a publication bias. Only randomized or quasi-randomized controlled trials were included. To minimize the reviewer bias, all steps of this review were conducted independently by two review authors. The validity of our review's results is potentially compromised by the following: most of the included trials (except two) were of small sample size and inadequate information was reported to assess quality; included trials utilized different preparations and dosing regimens of the intervention under study; data on the highest risk population (ELBW infants) could not be retrieved.

The principal investigators of included trials are being contacted to get additional unreported information and, if further data becomes available, it will be incorporated in to update of this review.

Authors' conclusions

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Implications for practice

Enteral supplementation of probiotics reduced the risk of severe NEC and mortality in preterm infants. This analysis supports a change in practice in premature infants > 1000 g at birth. Data regarding outcome of ELBW infants could not be extracted from the available studies; therefore, a reliable estimate of the safety and efficacy of administration of probiotic supplements cannot be made in this high risk group.

Implications for research

A large randomized controlled trial is required to investigate the potential benefits and safety profile of probiotics supplementation in the prevention of severe stage II-III NEC, mortality and sepsis in ELBW infants. More studies are also required to address the mechanism of action of probiotics supplementation in reduction of important intermediate neonatal outcomes.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

We would like to acknowledge Dr Gordon Guyatt (McMaster University, Hamilton Ontario) for his thoughtful comments on the methodology of this review.

Characteristics of studies

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Characteristics of included studies [ordered by study ID]

Bin-Nun 2005
MethodsSingle centre randomized study Method of generating randomization sequence: not described Blinding of randomization: not described Blinding of intervention: yes Blinding of outcome measurement: yes Completeness of follow-up: not specified
Participants145 infants less than 1500 g at birth Demographic data: Probiotics Group N=72, Gestational age (weeks) 29.2(2.6), birth weight 1152 (262) Placebo Group N=73, Gestational age (weeks) 29.3 (4.3), birth weight 1111 (278)
InterventionsProbiotics group (N=72) received mixture of Lactobacillus bifidus, streptococcus thermophillus, and bifidobactrium infantis added to 3 ml of expressed breast milk or premature formula enteral feeds. Control group (N=73) received 3 ml of expressed milk or premature formula with no supplements added.
OutcomesStage 2 or 3 NEC. Mortality NEC or mortality Sepsis Days to full feeds Days till TPN stopped
NotesIsrael Period of study: Sept 2001-Sept 2004 Published: Journal of Pediatrics 2005 Source of Funding: ABC Dophilus
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?UnclearB - Unclear
Costalos 2003
MethodsSingle center randomized double blind study Method of generating randomization sequence: cards in sealed envelopes Allocation concealment: possibly adequate Blinding of intervention: Yes Blinding of outcome measurement: not described Complete Follow-up: Yes
Participants87 infants, gestational age 28-32 weeks Exclusion criteria: Major anomalies, receiving antibiotics or anti -fungals, receiving breast milk Demographic data: Probiotics Group N=51, Gestational age (weeks) 31.1(2.5), birth weight 1651 (470) Placebo Group N=36, Gestational age (weeks) 31.8 (2.7), birth weight 1644 (348)
InterventionsProbiotics group (N=51) received preterm formula containing approximately 15 nmol/dl polyamines with added Saccharomyces boulardii 50mg/kg every 12 hours during the first week of life when enteral feed are tolerated for 30 days. Placebo group (N=36) received same formula with maltodextrins
OutcomesNEC Weight gain Abdominal distension Vomiting Gastric retention Stool characteristics Sepsis
NotesGreece Period of study: not specified Published: 2003 Source of Funding: Unclear
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?UnclearB - Unclear
Dani 2002
MethodsMulticenter randomized double blind study (12 centers) Method of generating randomization sequence: not described Allocation concealment: clearly adequate Blinding of Intervention: Yes Blinding of outcome measurement: Yes Complete Follow-up: Yes
Participants585 infants, < 33 weeks gestation or <1500g birth weight enrolled. Exclusion criteria: congenital malformation and death within two weeks of birth Demographic data: Probiotics Group N=295, gestational age (weeks) 30.8(2.4), birth weight 1325 (361) Placebo Group N=290, gestational age (weeks) 30.7 (2.3), birth weight 1345 (384)
InterventionsProbiotics group (N=295) received standard milk with Lactobacillus GG (Dicoflor®, Dicofarm, Rome, Italy) with an added dose of 6×109 colony forming units (cfu) once a day until discharge, starting with first feed. Placebo group (N=290) received standard milk with placebo which was an indistinguishable dried powder of maltodextrins.
OutcomesSevere NEC Incidence of PDA Duration of parenteral nutrition Urinary tract infection Bacterial sepsis (culture proven) Stage 2 and 3 NEC single course of antibiotics treatment NEC related mortality
NotesItaly Period of study: not specified in paper Published: 2002 Source of Funding: not specified in paper
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?YesA - Adequate
Kitajima 1997
MethodsSingle center randomized study Method of generating randomization sequence: not described Allocation concealment: Not described Blinding of Intervention: Not described Blinding of outcome measurement: not described Complete Follow-up: No (6 patients dropped)
Participants91 infants, birth weight <1500 g enrolled. Exclusion criteria: major anomalies, severe asphyxia, severe IUGR Demographic data: Probiotics Group N=45, gestational age (weeks) 28.3(2.3), birth weight 1026 (24) Placebo Group N=46, gestational age (weeks) 28.2 (2.1), birth weight 1026 (205)
InterventionsProbiotics group (N=45) received 1 ml supplement of Bifidobacterium breve with distilled water 0.5×109 of live B. breve within the 1st 24 hrs of life once per day for 28 days Control group (N=46) received distilled water
OutcomesColonization rate Mean aspired air volume Vomiting times/week Apnoea times/week Weight gain
NotesJapan Period of study: May 1990-April 1991 Published: 1997 Source of Funding: Unclear
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?UnclearB - Unclear
Li 2004
MethodsSingle center randomized study Method of generating randomization sequence: unclear Allocation concealment: Not described Blinding of Intervention: not described Blinding of outcome measurement: not described Complete Follow-up: unclear
Participants30 infants, of low birth weight. Exclusion criteria: Major anomalies, chromosomal anomalies, intrauterine infection Demographic data: Probiotics Group A N=10, gestational age (weeks) 33.8(2.9), birth weight 1523 (490) Probiotics Group B N=10, gestational age (weeks) 33.8(3.2), birth weight 1354 (280) Control (C) Group N=10, gestational age (weeks) 32.4 (3.1), birth weight 1480 (237)
InterventionsProbiotics group (N=10) received through gastric tube Bifidobacterium breve twice a day with feeds till discharge. Group A within several hours of birth, while group B after the 1st 24 hrs. Control group (N=10) received no supplement
OutcomesColonization rate NEC Sepsis
NotesJapan Period of study: Jan 2000- Aug 2002 Published: 2004 Source of Funding: Morinaja Milk industry and Meiji Dairies
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?UnclearB - Unclear
Lin 2005
MethodsSingle centre randomized study Method of generating randomization sequence: random-number table sequence. Allocation concealment: clearly adequate Blinding of intervention: Yes, only investigators and breast milk team were unblinded. Blinding of Outcome measurement: Yes Completeness of follow up: Yes
Participants367 infants less than 1500 g at birth, survived beyond 7 days of life, and started on enteral feed were enrolled Demographic data: Probiotics Group N=180, gestational age (weeks) 28.5(2.5), birth weight 1104 (242) Placebo Group N=187, gestational age (weeks) 28.2 (2.5), birth weight 1071 (243)
InterventionsProbiotics group (N=180) received Infloran® (L acidophilus and B infantis) obtained from the American Type Culture Collection in 1973, 125 mg/kg/dose twice daily with breast milk until discharge. All enrolled infants received maternal or banked breast milk. Control group (N=187) received breast milk without any addition (no placebo).
OutcomesDeath Stage 2 or 3 NEC Sepsis (culture proven) Composite outcomes of death+ NEC, sepsis+ NEC, death+ NEC+ Sepsis Duration of parenteral nutrition Hospitalization days
NotesTaiwan Period of study: July 1999- December 2003 Published: 2005 Source of Funding: supported by research department of China medical university hospital.
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?YesA - Adequate
Manzoni 2006
MethodsSingle centre randomized study Method of generating randomization sequence: computer generated randomization Allocation concealment: Unclear Blinding of intervention: can't tell Blinding of Outcome measurement: can't tell Completeness of follow up: Yes
Participants80 infants less than 1500 g at birth, survived beyond 3 days of life, and started on human or donor milk enteral feed were enrolled Demographic data: Probiotics Group N=39, gestational age (weeks) 29.6 (5), birth weight 1212 (290) Placebo Group N=41, gestational age (weeks) 41(4), birth weight 1174 (340)
InterventionsProbiotics group (N=39) received LGG [Diclofor 60;Dicofarm spa]; single dose (1/2 packet of Diclofor 60) daily mixed with human or donor milk till end of the sixth week or discharge. Control group (N=41) received human or donor milk without any addition (no placebo).
OutcomesFungal colonization rates Stage 2 or 4 NEC Death Sepsis (culture proven) Time to full feeds
NotesItaly Period of study: 12 months Published: 2006 Sources of support: non reported
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?UnclearB - Unclear
Millar 1993
MethodsSingle center randomized blinded study Method of generating randomization sequence: not described Allocation concealment: Not described Blinding of Intervention: Yes Blinding of outcome measurement: Unclear Complete Follow-up: Yes
Participants20 infants, < 33 weeks gestation enrolled. Demographic data: Probiotics Group N=10, gestational age (weeks) 30.5(26-33), birth weight 1445 (800-2560) Placebo Group N=10, gestational age (weeks) 30.0 (24-33), birth weight 1500 (830-2150)
InterventionsProbiotics group (N=10) received milk feeds with Lactobacillus GG 108 (cfu) twice a day for 14 days, starting with first feed. Placebo group (N=10) received un-supplemented milk
OutcomesWeight gain Sepsis clinical or lab proven Antibiotics treatment Oxygen and ventilatory requirements Hospital stay Perineal candidal infection Duration of hospital stay
NotesUK Period of study: Sept 1991-Jan 1992 Published: 1993 Source of Funding: Wessex Medical Trust
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?UnclearB - Unclear
Reuman 1986
MethodsRandomized double blind study Method of generating randomization sequence: random number charts and the last digit of patient's chart number, the next matched infants is assigned to the opposite group Allocation concealment: clearly inadequate Blinding of Intervention: Yes Blinding of outcome measurement: Yes Complete Follow-up: Yes
Participants45 infants, <2000 gm at birth weight who survived beyond first 24 hrs and are younger than 72 hrs Demographic data: Probiotics Group n=15, gestational age (weeks) 30.6(2.7), birth weight 1366 (302) Placebo Group n=15, gestational age (weeks) 30.5 (2.8), birth weight 1377 (344) Untreated group n=15, gestational age(weeks) 30.7(2.9), birth weight 1329(337)
InterventionsProbiotics group received at least 1 ml of formula containing lactobacillus. 5×1010 organisms/ml preparation diluted 100 times in infants formula. Placebo group received 1 ml of formula with no added lactobacillus Both groups started within 72 hrs of birth The untreated group received nothing per mouth for 2 weeks
OutcomesDeath Colonization rates Hospitalization duration Daily weight gain Hospital acquired infection
NotesUS Period of study: not specified in paper Published: 1986 Source of Funding: not specified in paper
Risk of bias
ItemAuthors' judgementDescription
Allocation concealment?NoC - Inadequate

Characteristics of excluded studies [ordered by study ID]

Agarwal 2003No clinical outcomes were presented
Stansbridge 1993No clinical outcomes were presented, physiological outcomes were addressed

Data and analyses

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References
Table Comparison 1.. Probiotics vs. control
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Severe Necrotising Enterocolitis (stage II-III)51264Risk Ratio (M-H, Fixed, 95% CI)0.32 [0.17, 0.60]
2 Mortality5 Risk Ratio (M-H, Fixed, 95% CI)Subtotals only
2.1 All cause neonatal mortality51207Risk Ratio (M-H, Fixed, 95% CI)0.43 [0.25, 0.75]
2.2 NEC realted mortality2730Risk Ratio (M-H, Fixed, 95% CI)0.17 [0.02, 1.37]
3 Sepsis61284Risk Ratio (M-H, Fixed, 95% CI)0.93 [0.73, 1.19]
3.1 Culture proven sepsis61284Risk Ratio (M-H, Fixed, 95% CI)0.93 [0.73, 1.19]
4 Parenteral nutrition duration (days)2 Mean Difference (IV, Fixed, 95% CI)Subtotals only
4.1 Dani 20021585Mean Difference (IV, Fixed, 95% CI)-1.90 [-4.57, 0.77]
4.2 Lin 20051367Mean Difference (IV, Fixed, 95% CI)0.80 [-0.30, 1.90]
5 Hospitalization days2 Mean Difference (IV, Fixed, 95% CI)Subtotals only
5.1 Lin 20051367Mean Difference (IV, Fixed, 95% CI)0.20 [-5.25, 5.65]
5.2 Reuman 1986130Mean Difference (IV, Fixed, 95% CI)20.70 [-11.77, 53.17]
6 Weight gain3 Mean Difference (IV, Fixed, 95% CI)Subtotals only
6.1 g/week187Mean Difference (IV, Fixed, 95% CI)7.20 [-0.06, 14.46]
6.2 g/day130Mean Difference (IV, Fixed, 95% CI)1.0 [-3.35, 5.35]
6.3 g/kg/day120Mean Difference (IV, Fixed, 95% CI)-0.5 [-8.02, 7.02]
7 Death or severe NEC or sepsis1367Risk Ratio (M-H, Fixed, 95% CI)0.54 [0.37, 0.79]
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Figure Analysis 1.1. Comparison 1 Probiotics vs. control, Outcome 1 Severe Necrotising Enterocolitis (stage II-III).

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Figure Analysis 1.2. Comparison 1 Probiotics vs. control, Outcome 2 Mortality.

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Figure Analysis 1.3. Comparison 1 Probiotics vs. control, Outcome 3 Sepsis.

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Figure Analysis 1.4. Comparison 1 Probiotics vs. control, Outcome 4 Parenteral nutrition duration (days).

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Figure Analysis 1.5. Comparison 1 Probiotics vs. control, Outcome 5 Hospitalization days.

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Figure Analysis 1.6. Comparison 1 Probiotics vs. control, Outcome 6 Weight gain.

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Figure Analysis 1.7. Comparison 1 Probiotics vs. control, Outcome 7 Death or severe NEC or sepsis.

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Feedback

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Davies, 9 May 2008

Summary

I read with interest the review by AlFaleh and Bassler. It was a well conducted systematic review that revealed that the use of probiotics in preterm infants significantly reduces the incidence of NEC and death in preterm infants. I am not sure why the authors have concluded that probiotics should only be used for preterm infants with a birthweight greater than 1000 grams. If we assume that the data on birthweight from individual studies are normally distributed, we can surmise from the mean birthweight and standard deviations that approximately 25% of babies included in the studies that contribute to the two main meta-analyses (for the outcomes of severe NEC and mortality) had a birthweight of less than 1000 grams. Only about 3% or less had a birthweight of greater than 1500 grams. The authors conclusions imply that the use of probiotics is supported for infants who are preterm (born at <37 weeks gestational age) and who had a birthweight of >1500 grams (less than ˜3% of the study population), but is not supported for infants who had a birthweight of <1000 grams (˜25% of the study population). The results of the review and its meta-analysis are highly significant, both statistically and clinically. They should be applicable to the population of infants that contributed to the pooled data, i.e., preterm babies who were (almost all) <1500 grams at birth.

The authors should provide justification for their recommendation that extremely low birth weight infants should not be given this intervention that provides a 57% reduction in the risk of death. Also, if further large randomized controlled trial[s] are done they must include assessment of long-term neurodevelopmental outcomes, not just important intermediate neonatal outcomes.

Reply

We first would like to thank you for your thoughtful comments on our recently published systematic review. Your question/comment was a one that we have thought of and discussed quite extensively prior to the publication of the review.

Although we agree that the efficacy of the probiotics in prevention of NEC or mortality holds true for the ELBW infant, we could not ensure the safety of this new intervention in a highly vulnerable group with the number of infants enrolled; especially with few cases of probiotics species sepsis reported in the literature.

Contributors

Khalid M. Al-Faleh, July 2008

What's new

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

Last assessed as up-to-date: 30 August 2007.

12 November 2008Feedback has been incorporatedFeedback incorporated
22 July 2008AmendedConverted to new review format.

Contributions of authors

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References

KA developed the protocol.

Both review authors assessed trials for eligibility, quality and extracted the data independently.

KA wrote the manuscript with revisions made by DB.

References

  1. Top of page
  2. Abstract
  3. Background
  4. Objectives
  5. Methods
  6. Results
  7. Discussion
  8. Authors' conclusions
  9. Acknowledgements
  10. Characteristics of studies
  11. Data and analyses
  12. Feedback
  13. What's new
  14. History
  15. Contributions of authors
  16. Declarations of interest
  17. Sources of support
  18. References
  • References to studies included in this review
  • Bin-Nun 2005 {published data only}
  • Bin-Nun A, Bromiker R, Wilschanski M, Kaplan M, Rudensky B, Caplan M, Hammerman C. Oral probiotics prevent necrotizing enterocolitis in very low birth weight neonates. Journal of Pediatrics 2005;147:192-6.
  • Costalos 2003 {published data only}
  • Costalos C, Skouteri V, Gounaris A, Sevastiadou S, Triandafilidou A, Ekonomidou C, et al.Enteral feeding of premature infants with Saccharomyces boulardii. Early Human Development 2003;74:89-96.
  • Dani 2002 {published data only}
  • Dani C, Biadaioli R, Bertini G, Martelli E, Rubaltelli F. Probiotics feeding in prevention of urinary tract infection, bacterial sepsis and necrotizing enterocolitis in preterm infants. A prospective double-blind study. Biology of the Neonate 2002;82:103-8.
  • Kitajima 1997 {published data only}
  • Kitajima H, Sumida Y, Tanaka R, Yuki, Takayama H, Fujimura M. Early administration of Bifidobacterium breve to preterm infants: randomised controlled trial. Archives of Disease in Childhood Fetal Neonatal Ed 1997;76:F101-7.
  • Li 2004 {published data only}
  • Li Y, Shimizu T, Hosaka A, Kaneko N, Ohtsuka Y, Yamashiro Y. Effects of bifidobacterium breve supplementation on intestinal flora of low birth weight infants. Pediatrics International 2004;46:509-5.
  • Lin 2005 {published data only}
  • Lin HC, Su BH, Chen AC, Lin TW, Tsai CH, Yeh TF, Oh W. Oral probiotics reduce the incidence and severity of necrotizing enterocolitis in very low birth weight infants. Pediatrics 2005;115:1-4.
  • Manzoni 2006 {published data only}
  • Manzoni P, Mostert M, Leonessa ML, Priolo C, Farina D, Monetti C, Latino MA, Gomirato G. Oral supplemantation with lactobacillus casei subspecies rhamnosus prevents enteric colonization by Candida species in preterm neonates: a randomized study. Clinical infectious disease 2006;15:1735-42.
  • Millar 1993 {published data only}
  • Millar MR, Bacon C, Smith SL, Walker V, Hall MA. Enteral feeding of premature infants with Lactobacillus GG. Archives of Disease in Childhood 1993;69:483-7.
  • Reuman 1986 {published data only}
  • Reuman PD, Duckworth DH, Smith KL, Kagan R, Bucciarelli RL, Ayoub EM. Lack of effect of Lactobacillus on gastrointestinal bacterial colonization in premature infants. Pediatric Infectious Disease 1986;5:663-8.
  • References to studies excluded from this review
  • Agarwal 2003 {published data only}
  • Agarwal R, Sharma N, Chaudhry R, Deorari A, Paul VK, Gewolb IH, Panigrahi P. Effects of oral Lactobacillus GG on enteric microflora in low-birth-weight neonates. Journal of Pediatric Gastroenterology and Nutrition 2003;36:397-402.
  • Stansbridge 1993 {published data only}
  • Stansbridge EM, Walker V, Hall MA, Smith SL, Millar MR, Bacon C, Chen S. Effects of feeding premature infants with Lactobacillus GG on gut fermentation. Archives of Disease in Childhood 1993;69:488-92.
  • References to studies awaiting assessment
  • Uhlemann 1999 {published data only}
  • Uhlemann M, Heine W, Mohr C, Plath C, Pap S. Effects of oral administration of bifidobacteria on intestinal microflora in premature and newborn infants newborn infants. Zeitschrift fur Geburtshilfe und Neonatologie 1999;203:213-17.
  • Additional references
  • Bell 1978
  • Bell MJ, Ternberg JL, Feigin RD, Keating JP, Marshall R, Barton L, Brotherton T. Neonatal necrotizing enterocolitis. Therapeutic decisions based upon clinical staging. Annals of Surgery 1978;187:1-7. [MEDLINE: 44]
  • Bisquera 2002
  • Bisquera JA, Cooper TR, Berseth CL. Impact of necrotizing enterocolitis on length of stay and hospital charges in very low birth weight infants. Pediatrics 2002;109:423-8. [MEDLINE: 24]
  • Butel 1998
  • Butel MJ, Roland N, Hibert A, Popot F, Favre A, Tessedre AC, et al.Clostridial pathogenicity in experimental necrotising enterocolitis in gnotobiotic quails and protective role of bifidobacteria. Journal of Medical Microbiology 1998;47:391-9. [MEDLINE: 42]
  • Caplan 1999
  • Caplan MS, Miller-Catchpole R, Kaup S, Russell T, Lickerman M, Amer M, et al.Bifidobacterial supplementation reduces the incidence of necrotizing enterocolitis in a neonatal rat model. Gastroenterology 1999;117:577-83. [MEDLINE: 41]
  • Caplan 2001
  • Caplan MS, Jilling T. New concepts in necrotizing enterocolitis. Current Opinion in Pediatrics 2001;13:111-5. [MEDLINE: 20]
  • Duffy 2000
  • Duffy LC. Interactions mediating bacterial translocation in the immature intestine. Journal of Nutrition 2000;130:432S-36S. [MEDLINE: 39]
  • Gewolb 1999
  • Gewolb IH, Schwalbe RS, Taciak VL, Harrison TS, Panigrahi P. Stool microflora in extremely low birthweight infants. Archives of Disease in Childhood Fetal and Neonatal Edition 1999;80:F167-73. [MEDLINE: 34]
  • Goldmann 1978
  • Goldmann DA, Leclair J, Macone A. Bacterial colonization of neonates admitted to an intensive care environment. Journal of Pediatrics 1978;93:288-93. [MEDLINE: 33]
  • Harmsen 2000
  • Harmsen HJ, Wildeboer-Veloo AC, Raangs GC, Wagendorp AA, Klijn N, Bindels JG, Welling GW. Analysis of intestinal flora development in breast-fed and formula-fed infants by using molecular identification and detection methods. Journal of Pediatric Gastroenterology and Nutrition 2000;30:61-7. [MEDLINE: 32]
  • Holman 1997
  • Holman RC, Stoll BJ, Clarke MJ, Glass RI. The epidemiology of necrotizing enterocolitis infant mortality in the United States. American Journal of Public Health 1997;87:2026-31. [MEDLINE: 21]
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  • Kosloske 1994
  • Kosloske AM. Epidemiology of necrotizing enterocolitis. Acta Paediatrica Suppl 1994;396:2-7.
  • La Gamma 1994
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  • Link-Amster 1994
  • Link-Amster H, Rochat F, Saudan KY, Mignot O, Aeschlimann JM. Modulation of a specific humoral immune response and changes in intestinal flora mediated through fermented milk intake. FEMS Immunology and Medical Microbiology 1994;10:55-63. [MEDLINE: 40]
  • Mattar 2001
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  • Millar 2003
  • Millar M, Wilks M, Costeloe K. Probiotics for preterm infants?. Archives of Disease in Childhood Fetal and Neonatal Edition 2003;88:F354-8. [MEDLINE: 35]
  • Musemeche 1986
  • Musemeche CA, Kosloske AM, Bartow SA, Umland ET. Comparative effects of ischemia, bacteria, and substrate on the pathogenesis of intestinal necrosis. Journal of Pediatric Surgery 1986;21:536-8. [MEDLINE: 31]
  • Neu 1996
  • Neu J. Necrotizing enterocolitis: the search for a unifying pathogenic theory leading to prevention. Pediatric Clinics of North America 1996;43:409-32. [MEDLINE: 26]
  • Orrhage 1999
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  • Reid 2001
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  • Richard 1988
  • Richard V, Van der Auwera AP, Snoeck R, Daneau D, Meunier F. Nosocomial bacteremia caused by Bacillus species. European Journal of Clinical Microbiology and Infectious Diseases 1988;7:783-5. [MEDLINE: 43]
  • Ricketts 1994
  • Ricketts RR. Surgical treatment of necrotizing enterocolitis and the short bowel syndrome. Clinics in Perinatology 1994;21:365-87. [MEDLINE: 23]
  • Stoll 1996
  • Stoll BJ, Gordon T, Korones SB, Shankaran S, Tyson JE, Bauer CR, et al.Late-onset sepsis in very low birth weight neonates: a report from the National Institute of Child Health and Human Development Neonatal Research Network. Journal of Pediatrics 1996;129:63-71. [MEDLINE: 28]
  • Stoll 2002a
  • Stoll BJ, Hansen N, Fanaroff AA, Wright LL, Carlo WA, Ehrenkranz RA, et al.Late-onset sepsis in very low birth weight neonates: the experience of the NICHD Neonatal Research Network. Pediatrics 2002;110(2 Pt 1):285-91.
  • Stoll 2002b
  • Stoll BJ, Hansen N, Fanaroff AA, Wright LL, Carlo WA, Ehrenkranz RA, et al.Changes in pathogens causing early-onset sepsis in very-low-birth-weight infants. New England Journal of Medicine 2002;347:240-7.
  • Stoll 2004
  • Stoll BJ, Hansen NI, ms-Chapman I, Fanaroff AA, Hintz SR, Vohr B, Higgins RD. Neurodevelopmental and growth impairment among extremely low-birth-weight infants with neonatal infection. JAMA 2004;292:2357-65. [MEDLINE: 25]
  • Walsh 1986
  • Walsh MC, Kliegman RM. Necrotizing enterocolitis: treatment based on staging criteria. Pediatric Clinics of North America 1986;33:179-201. [MEDLINE: 45]