A bacteriologic basis for the clinical presentations of necrotizing enterocolitis

Prevalence of pathogens associated with neonatal gastrointestinal infections: a systematic review and meta-analysis

Gastrointestinal infections represent a significant global health burden, ranking as the second leading cause of mortality among infants and children. Identifying of pathogens causing neonatal gastrointestinal infections has presented tough challenges. This study aimed to summarize the prevalence of common pathogens associated with neonatal gastrointestinal infections through a comprehensive systematic review and meta-analysis of published literature. The last search was performed on January 08, 2025, from databases including EMBASE, PubMed, Cochrane Libary, and Web of Science. The outcome variable was infection rate, and the detection methods used were blood culture, tissue culture, or molecular biology methods. Two researchers independently extracted the research data and evaluated its quality using the JBI Critical Appraisal Tools. Twenty-three studies met the inclusion criteria. The pooled prevalence rates of common pathogens were as follows: Bacteria, including Escherichia (22.2%; 95% CI 8.3-40.4%, I2 = 98%), Clostridium (21.8%; 95% CI 2.2-53.8%, I2 = 96%), Klebsiella (19.2%; 95% CI 8.3-33.4%, I2 = 97%), Staphylococcus (13.6%; 95% CI 6.0-23.7%, I2 = 91%), Enterococcus (12.4%; 95% CI 1.8-30.3%, I2 = 96%), and Streptococcus (6.8%; 95% CI 2.5-12.9%, I2 = 43%). Fungi, including Candida (3.8%; 95% CI 0.6-9.6%, I2 = 84%). Viruses, including Rotavirus (11.6%; 95% CI 1.0-31.5%, I2 = 94%) and Adenovirus (4.1%; 95% CI 0.5-11.0%, I2 = 58%). Peritoneal culture methods demonstrated significantly higher positivity rates compared to other detection methods. Escherichia coli exhibited consistently high positivity rates across the three main detection methods. Klebsiella showed the highest positivity rates among bacterial isolates in both blood and peritoneal cultures. Pathogen detection and prevalence in necrotizing enterocolitis (NEC) cases were markedly higher compared to other conditions. This meta-analysis identifies key pathogens in gastrointestinal infections, including Klebsiella pneumoniae, Escherichia coli, Candida, Rotavirus, Adenovirus, and others that are suspected before clinical sample results are available. It also highlights that intestinal pathogen infections are linked to an increased risk of neonatal necrotizing enterocolitis (NEC) and emphasizes the advantages of peritoneal culture in detecting these infections.

Intrauterine Shaping of Fetal Microbiota

Mechanisms resulting from the physiological immaturity of the digestive system in children delivered before 32 weeks of gestation and, in particular, different interactions between the microbiome and the body have not been fully elucidated yet. Next-generation sequencing methods demonstrated the presence of bacterial DNA in the placenta and amniotic fluid, which may reflect bacterial populations that initiate intestinal colonization in utero. Numerous studies confirmed the hypothesis stating that intestinal bacteria played an important role in the pathogenesis of necrotizing enterocolitis (NEC) early- and late-onset neonatal sepsis (EONS and LONS). The model and scale of disorders within the intestinal microbiome are the subject of active research in premature infants. Neonatal meconium was primarily used as an indicator defining the environment in utero, as it is formed before birth. Metagenomic results and previous data from microbiological bacterial cultures showed a correlation between the time from birth to sample collection and the detection of bacteria in the neonatal meconium. Therefore, it may be determined that the colonization of the newborn's intestines is influenced by numerous factors, which may be divided into prenatal, perinatal, and postnatal, with particular emphasis put on the mode of delivery and contact with the parent immediately after birth. Background: The aim of this review was to collect available data on the intrauterine shaping of the fetal microbiota. Methods: On 13 March 2024, the available literature in the PubMed National Library of Medicine search engine was reviewed using the following selected keywords: "placental microbiome", "intestinal bacteria in newborns and premature infants", and "intrauterine microbiota". Results: After reviewing the available articles and abstracts and an in-depth analysis of their content, over 100 articles were selected for detailed elaboration. We focused on the origin of microorganisms shaping the microbiota of newborns. We also described the types of bacteria that made up the intrauterine microbiota and the intestinal microbiota of newborns. Conclusions: The data presented in the review on the microbiome of both term newborns and those with a body weight below 1200 g indicate a possible intrauterine colonization of the fetus depending on the duration of pregnancy. The colonization occurs both via the vaginal and intestinal route (hematogenous route). However, there are differences in the demonstrated representatives of various types of bacteria, phyla Firmicutes and Actinobacteria in particular, taking account of the distribution in their abundance in the individual groups of pregnancy duration. Simultaneously, the distribution of the phyla Actinobacteria and Proteobacteria is consistent. Considering the duration of pregnancy, it may also be concluded that the bacterial flora of vaginal origin dominates in preterm newborns, while the flora of intestinal origin dominates in term newborns. This might explain the role of bacterial and infectious factors in inducing premature birth with the rupture of fetal membranes.

Exploring the Role of Gut Bacteria in Health and Disease in Preterm Neonates

The mortality rate of very preterm infants with birth weight <1500 g is as high as 15%. The survivors till discharge have a high incidence of significant morbidity, which includes necrotising enterocolitis (NEC), early-onset neonatal sepsis (EONS) and late-onset neonatal sepsis (LONS). More than 25% of preterm births are associated with microbial invasion of amniotic cavity. The preterm gut microbiome subsequently undergoes an early disruption before achieving bacterial maturation. It is postulated that bacterial gut colonisation at birth and postnatal intestinal dysbacteriosis precede the development of NEC and LONS in very preterm infants. In fact, bacterial colonization patterns in preterm infants greatly differ from term infants due to maternal chorioamnionitis, gestational age, delivery method, feeding type, antibiotic exposure and the environment factor in neonatal intensive care unit (NICU). In this regard, this review provides an overview on the gut bacteria in preterm neonates' meconium and stool. More than 50% of preterm meconium contains bacteria and the proportion increases with lower gestational age. Researchers revealed that the gut bacterial diversity is reduced in preterm infants at risk for LONS and NEC. Nevertheless, the association between gut dysbacteriosis and NEC is inconclusive with regards to relative bacteria abundance and between-sample beta diversity indices. With most studies show a disruption of the Proteobacteria and Firmicutes preceding the NEC. Hence, this review sheds light on whether gut bacteria at birth either alone or in combination with postnatal gut dysbacteriosis are associated with mortality and the morbidity of LONS and NEC in very preterm infants.

Gut and Lung Microbiota in Preterm Infants: Immunological Modulation and Implication in Neonatal Outcomes

In recent years, an aberrant gastrointestinal colonization has been found to be associated with an higher risk for postnatal sepsis, necrotizing enterocolitis (NEC) and growth impairment in preterm infants. As a consequence, the reasons of intestinal dysbiosis in this population of newborns have increasingly become an object of interest. The presence of a link between the gut and lung microbiome's development (gut-lung axis) is emerging, and more data show as a gut-brain cross talking mediated by an inflammatory milieu, may affect the immunity system and influence neonatal outcomes. A revision of the studies which examined gut and lung microbiota in preterm infants and a qualitative analysis of data about characteristic patterns and related outcomes in terms of risk of growing impairment, Necrotizing Enterocolitis (NEC), Bronchopulmonary Dysplasia (BPD), and sepsis have been performed. Microbiota take part in the establishment of the gut barrier and many data suggest its immune-modulator role. Furthermore, the development of the gut and lung microbiome (gut-lung axis) appear to be connected and able to lead to abnormal inflammatory responses which have a key role in the pathogenesis of BPD. Dysbiosis and the gut predominance of facultative anaerobes appear to be crucial to the pathogenesis and subsequently to the prevention of such diseases.

Necrotizing Enterocolitis and the Preterm Infant Microbiome

Bacterial colonization patterns in preterm infants differ from those of their term counterparts due to maternal microbial diversity, delivery mode, feeding methods, antibiotic use, and exposure to commensal microbiota and pathogens in the neonatal intensive care unit (NICU). Early gut microbiome dysbiosis predisposes neonates to necrotizing enterocolitis (NEC), a devastating intestinal disease with high morbidity and mortality. Though mechanisms of NEC pathogenesis are not fully understood, the microbiome is a promising therapy target for prevention and treatment. Direct administration of probiotics to preterm infants has been shown to reduce the incidence of NEC, but is not without risk. The immature immune systems of preterm infants leave them vulnerable to even beneficial bacteria. Further research is required to investigate both short-term and long-term effects of probiotic administration to preterm infants. Other methods of altering the preterm infant microbiome must also be considered, including breastfeeding, prebiotics, and targeting the maternal microbiome.

Enteral administration of bacteria fermented formula in newborn piglets: A high fidelity model for necrotizing enterocolitis (NEC)

Objective

To develop an animal model which replicates neonatal NEC and characterizes the importance of bacterial fermentation of formula and short chain fatty acids (SCFAs) in its pathogenesis.

Background

NEC is a severe form of intestinal inflammation in preterm neonates and current models do not reproduce the human condition.

Methods

Three groups of newborn piglets: Formula alone (FO), Bacteria alone (E.coli: BO) and E.coli-fermented formula (FF) were anesthetized, instrumented and underwent post-pyloric injection of formula, bacteria or fermented-formula. SCFA levels were measured by gas chromatography-mass spectrometry. At 6 h bowel appearance was assessed, histologic and molecular analysis of intestine were performed. Gut inflammation (p65 NF-κB, TLR4, TNF-α, IL-1β), apoptosis (cleaved caspase-3, BAX, apoptosis) and tight junction proteins (claudin-2, occludin) were measured.

Results

SCFAs were increased in FF. Small bowel from FF piglet’s demonstrated inflammation, coagulative necrosis and pneumatosis resembling human NEC. Histologic gut injury (injury score, mast cell activation) were increased by Bacteria, but more severe in FF piglets. Intestinal expression of p65 NF-κB, NF-κB activation, TNF-α and IL-1β were increased in BO and markedly increased in the FF group (P<0.05 vs. FO). Intestine from Bacteria piglets demonstrated increased apoptotic index, pro-apoptotic protein expression and decreased tight junction proteins. These changes were more severe in FF piglets.

Conclusions

Our piglet model demonstrates the findings of NEC in human neonates: systemic acidosis, intestinal inflammation, pneumatosis and portal venous gas. Bacteria alone can initiate intestinal inflammation, injury and apoptosis, but bacterial fermentation of formula generates SCFAs which contribute to the pathogenesis of NEC.

The human milk oligosaccharide 2'-fucosyllactose attenuates the severity of experimental necrotising enterocolitis by enhancing mesenteric perfusion in the neonatal intestine

Necrotising enterocolitis (NEC) is a common disease in premature infants characterised by intestinal ischaemia and necrosis. The only effective preventative strategy against NEC is the administration of breast milk, although the protective mechanisms remain unknown. We hypothesise that an abundant human milk oligosaccharide (HMO) in breast milk, 2'-fucosyllactose (2'FL), protects against NEC by enhancing intestinal mucosal blood flow, and we sought to determine the mechanisms underlying this protection. Administration of HMO-2'FL protected against NEC in neonatal wild-type mice, resulted in a decrease in pro-inflammatory markers and preserved the small intestinal mucosal architecture. These protective effects occurred via restoration of intestinal perfusion through up-regulation of the vasodilatory molecule endothelial nitric oxide synthase (eNOS), as administration of HMO-2'FL to eNOS-deficient mice or to mice that received eNOS inhibitors did not protect against NEC, and by 16S analysis HMO-2'FL affected the microbiota of the neonatal mouse gut, although these changes do not seem to be the primary mechanism of protection. Induction of eNOS by HMO-2'FL was also observed in cultured endothelial cells, providing a link between eNOS and HMO in the endothelium. These data demonstrate that HMO-2'FL protects against NEC in part through maintaining mesenteric perfusion via increased eNOS expression, and suggest that the 2'FL found in human milk may be mediating some of the protective benefits of breast milk in the clinical setting against NEC.

The viral dsRNA analogue poly (I:C) induces necrotizing enterocolitis in neonatal mice

BACKGROUND

Necrotizing enterocolitis (NEC) is a life-threatening gastrointestinal disease in premature infants with high mortality and morbidity with uncertain pathogenesis. Recent research focused on the role of intraluminal bacteria and lipopolysaccharide (LPS). However, an additional role of viral agents in the pathogenesis of NEC has recently been postulated. We assessed the role of polyinosinic:polycytidylic acid (pIC) mimicking viral dsRNA in contributing to the development of NEC in neonatal mice.

METHODS

Four-d-old C57BL/6J pups were stressed by asphyxia and hypothermia twice daily. Animals were either fed by formula only (FO), formula containing LPS or pIC. After 72 h, mice were euthanized, intestines harvested, and the severity of NEC was assessed.

RESULTS

Breastfed mice showed no evidence of NEC. Very mild NEC-like lesions were observed in mice fed by FO. Supplementation of LPS or pIC to the formula led to increased intestinal tissue damage and inflammation compared with FO in a similar manner.

CONCLUSION

Our study demonstrates the ability of viral factors to induce NEC in neonatal mice even in the absence of LPS. Furthermore, we present a new mouse model of pIC-induced NEC which may be used to obtain further mechanistic insights in the pathogenesis of this disease.

Infectious causes of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency among premature infants. Although a large body of research has focused on understanding its pathogenesis, the exact mechanism has not been elucidated. Of particular interest is the potential causative role of infectious culprits in the development of NEC. A variety of reports describe bacterial, viral, and fungal infections occurring in association with NEC; however, no single organism has emerged as being definitively involved in NEC pathogenesis. In this review, the authors summarize the literature on infectious causes of NEC.

Anaerobic antimicrobial therapy after necrotizing enterocolitis in VLBW infants

OBJECTIVE

To evaluate the effect of anaerobic antimicrobial therapy for necrotizing enterocolitis (NEC) on clinical outcomes in very low birth weight (≤1500 g) infants.

METHODS

We identified very low birth weight infants with NEC from 348 US NICUs from 1997 to 2012. Anaerobic antimicrobial therapy was defined by antibiotic exposure on the first day of NEC. We matched (1:1) infants exposed to anaerobic antimicrobial therapy with infants who were not exposed by using a propensity score stratified by NEC severity (medical and surgical). The primary composite outcome was in-hospital death or intestinal stricture. We assessed the relationship between anaerobic antimicrobial therapy and outcome by using a conditional logistic regression on the matched cohort.

RESULTS

A total of 1390 infants exposed to anaerobic antimicrobial therapy were matched with 1390 infants not exposed. Mean gestational age and birth weight were 27 weeks and 946 g, respectively, and were similar in both groups. We found no significant difference in the combined outcome of death or strictures, but strictures as a single outcome were more common in the anaerobic antimicrobial therapy group (odds ratio 1.73; 95% confidence interval, 1.11-2.72). Among infants with surgical NEC, mortality was less common with anaerobic antimicrobial therapy (odds ratio 0.71; 95% confidence interval, 0.52-0.95).

CONCLUSIONS

Anaerobic antimicrobial therapy was not associated with the composite outcome of death or strictures but was associated with an increase in intestinal strictures. This higher incidence of intestinal strictures may be explained by the fact that death is a competing outcome for intestinal strictures, and mortality was slightly lower in the anaerobic cohort. Infants with surgical NEC who received anaerobic antimicrobial therapy had lower mortality.

Investigation of the early intestinal microflora in premature infants with/without necrotizing enterocolitis using two different methods

INTRODUCTION

The pathophysiology of necrotizing enterocolitis (NEC) is multifactorial, and gastrointestinal bacteria are thought to play an important role. In this study, the role of microflora in the gastrointestinal tract of neonates with NEC was assessed by comparing cases with controls.

RESULTS

Of the 163 neonates, 21 developed NEC. The risk of NEC decreased by 8% with each additional day of gestational age.

DISCUSSION

Typically, very few bacterial species could be cultured from the fecal specimens obtained. Gram-positive (G(+)) bacteria dominated the samples in the NEC group, whereas in the control group mixed flora of G(+) and Gram-negative (G(-)) bacteria were isolated. Surprisingly, molecular analysis using PCR-DGGE profiles did not confirm these differences. Our data suggest that G(+) bacteria in the intestine may play a role in the development of NEC in premature infants.

METHODS

One hundred and sixty three neonates born at <30 weeks of gestation were enrolled. Fecal samples taken during the first month of life were subjected to culture and PCR-denaturing gradient gel electrophoresis (PCR-DGGE). A total of 482 fecal samples were examined.

Redefining the role of intestinal microbes in the pathogenesis of necrotizing enterocolitis

Neonatal necrotizing enterocolitis (NEC) remains an important cause of morbidity and mortality among very low birth weight infants. It has long been suspected that intestinal microbes contribute to the pathogenesis of NEC, but the details of this relationship remain poorly understood. Recent advances in molecular biology and enteric microbiology have improved our ability to characterize intestinal microbes from infants with NEC and from healthy unaffected newborns. The lack of diversity within the neonatal intestine makes it possible to study gut microbial communities at a high level of resolution not currently possible in corresponding studies of the adult intestinal tract. Here, we summarize clinical and laboratory evidence that supports the hypothesis that NEC is a microbe-mediated disorder. In addition, we detail recent technologic advances that may be harnessed to perform high-throughput, comprehensive studies of the gut microbes of very low birth weight infants. Methods for characterizing microbial genotype are discussed, as are methods of identifying patterns of gene expression, protein expression, and metabolite production. Application of these technologies to biological samples from affected and unaffected newborns may lead to advances in the care of infants who are at risk for the unabated problem of NEC.

The role of anaerobic bacteria in bacteremia

Anaerobic bacteria remain an important cause of bloodstream infections and account for 1-17% of positive blood cultures. This review summarizes the epidemiology, microbiology, predisposing conditions, and treatment of anaerobic bacteremia (AB) in newborns, children, adults and in patients undergoing dental procedures. The majority of AB are due to Gram-negative bacilli, mostly Bacteroides fragilis group. The other species causing AB include Peptostreptococcus, Clostridium spp., and Fusobacterium spp. Many of these infections are polymicrobial. AB in newborns is associated with prolonged labor, premature rupture of membranes, maternal amnionitis, prematurity, fetal distress, and respiratory difficulty. The predisposing conditions in children include: chronic debilitating disorders such as malignant neoplasm, hematologic abnormalities, immunodeficiencies, chronic renal insufficiency, or decubitus ulcers and carried a poor prognosis. Predisposing factors to AB in adults include malignant neoplasms, hematologic disorders, transplantation of organs, recent gastrointestinal or obstetric gynecologic surgery, intestinal obstruction, diabetes mellitus, post-splenectomy, use of cytotoxic agents or corticosteroids, and an undrained abscess. Early recognition and appropriate treatment of these infections are of great clinical importance.

Low mortality in necrotizing enterocolitis associated with coagulase-negative Staphylococcus infection

The aim of this study was to correlate the clinical course of necrotizing enterocolitis (NEC) with infection by coagulase-negative Staphylococcus at the onset of the illness. Records of all newborn infants developing NEC between January 1998 and December 2001 were reviewed. NEC was classified according to the criteria of Bell et al. Numeric variables were described by standard statistical methods. Comparisons between subgroups were performed by parametric statistical tests. Forty-four patients developed NEC stage II (n = 25) or III (n = 19). The incidence was 0.024% of live births in the hospital, and the mortality rate was 9%. The main risk factor was prematurity (84%). Only one-fourth of the patients had gastric residuals. A platelet count of <100,000 cells/mm3 occurred only in grade III NEC. Blood cultures were positive in 34% of the patients. The predominant organism (73%) was coagulase-negative Staphylococcus (CoNS). Neither Clostridium nor Bacteroides species were isolated. Stage II patients were maintained nothing per os (NPO) for 9 +/- 3 days and received antibiotics for 10 +/- 3 days. All of the stage III patients required an operation. In one-third of them, primary peritoneal drainage was initially performed but all required further operative procedures. We report a low incidence and mortality rate of necrotizing enterocolitis. Thrombocytopenia is confirmed as a marker of severity. Positive blood cultures for CoNS may explain, at least in part, the low mortality reported.

Current issues in the management of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common surgical emergency in the neonatal intensive care unit and remains a major cause of death in neonates. Although the pathophysiology of NEC has not been completely elucidated, progress has been made in the characterization of the molecular events which may take place during an episode of ischemia. This possible initiating event is followed by a complex cascade of inflammatory mediators active in NEC: epidermal growth factor, platelet-activating factor, and, nitric oxide. Additionally, unique characteristics of the premature gut are thought to be crucial to the development of NEC. The diagnosis of NEC continues to be based on clinical and radiographic features. Several new laboratory tests are under investigation for the purposes of earlier diagnosis, but none have prevailed at this time. Both exploratory laparotomy, with intestinal resection and peritoneal drainage are widely practiced. Mortality rates remain high and have improved little over the last couple of decades. Therefore, prevention remains crucial in order to decrease the incidence of NEC. Cautious feeding regimens, the use of maternal breast milk, passive immunization, and the use of probiotics have all been suggested but not proven as possible preventive methods. Although many advances have been made, significant opportunity remains to improve our understanding of the disease process and to develop better strategies for prevention and treatment.

Necrotizing enterocolitis in full-term infants

OBJECTIVES

Although necrotizing enterocolitis (NEC) is primarily a disease of prematurity, full-term infants account for approximately 10% of cases. Previous studies have reported conflicting results regarding NEC in full-term (FT) versus preterm (PT) infants. A review of all infants diagnosed with NEC at our institution over the past 3 decades was performed to identify factors associated with this disease in full-term neonates.

METHODS

The charts of all infants with definitive NEC from January 1, 1972 through January 1, 2001 were reviewed. Two hundred seventy-seven patients made up the study group: 251 PT and 26 FT infants. Data regarding demographics, clinical presentation, management, outcome, and other variables were collected. FT and PT infants were compared.

RESULTS

Mean gestational age and birth weight in the FT group were 39.3 weeks and 3,132 g versus 30.2 weeks and 1,396 g for PT infants. Apgar scores were similar. Mean age at diagnosis was 5 days in FT versus 13 days in PT neonates (P <.001). Enteral nutrition was initiated earlier in FT infants (1.6 days v 3.1 days; P <.001), and FT infants were discharged an average of 14 days earlier than PT infants (P value not significant). Factors predisposing to NEC were found in 62% (16 of 26) of patients-heart disease in 6 infants and other conditions in 10 patients. Cardiac disease was found significantly more often (23% v 10%; P =.027) in FT infants. Survival rate was 65% (17 of 26) in the FT group versus 69% (173 of 251) in the PT infants (P value not significant).

CONCLUSIONS

FT infants with NEC differ from their PT counterparts in several distinct ways. FT neonates had NEC at a significantly earlier age, perhaps owing to earlier initiation of feeding. There was a correlation between age at which feeding was begun and age of onset of NEC. Additionally, an association between cardiac disease and development of NEC in term infants was shown. Predisposing factors were present in a majority of FT infants. In contrast to other reports, the outcome of NEC in full-term infants was no better than for PT infants.

An outbreak of necrotizing enterocolitis associated with a novel clostridium species in a neonatal intensive care unit

An outbreak of necrotizing enterocolitis (NEC) occurred in 6 neonates within a 2-month period. Blood cultures from 3 of these neonates grew the same strain of what appears to be a novel clostridial species for which the name "Clostridium neonatale" has been proposed. A point-prevalence survey that used rectal swabs was performed in our intensive-care and intermediate-care nurseries, and it indicated that 20.8% of neonates carried this same "C. neonatale" strain despite having no evidence of NEC. In conclusion, we describe an outbreak of NEC associated with the novel species, and we suggest that, in larger neonates, carriage of this type of Clostridium species may be a necessary step in the multistage pathogenesis of NEC.

Complications after surgical intervention for necrotizing enterocolitis: a multicenter review

Necrotizing enterocolitis (NEC) is a serious condition affecting predominantly the premature infant. The purpose of this study is to report a multicenter experience of complications in 252 infants requiring surgical therapy for NEC. Data from eight institutions for the years 1980 through 1990 were collected and analyzed for infants undergoing surgical therapy for NEC. Records were reviewed for gestational age, birth weight, age at operation, indications for operation, degree of intestinal involvement, operation(s) performed, complications, and 30-day mortality rates. A total of 264 infants underwent surgical intervention for NEC during the study period. Complete information was available for 252 patients. The mean gestational age was 31 +/- 5 weeks and the mean birth weight was 1,552 +/- 823 g. The mean age at operation was 18 +/- 35 days. Pneumoperitoneum was the most common indication for operation (42%). The 30-day survival rate was 72%. Eighty-one percent of patients underwent primary laparotomy, whereas peritoneal drainage was performed in 48 (19%) patients. Postoperative complications were identified in 119 (47%) patients. The most common postoperative complications were sepsis (9%), intestinal strictures (9%), and short gut (9%). Wound infections occurred in 6%, and the incidence of intraabdominal abscess formation was only 2.3%. Gestational age < 27 weeks (P < .005) and birth weight < 1,000 g (P < .005) were associated with significantly increased mortality but no increase in postoperative morbidity. The incidence of complications was similar in the very low birth weight (< 1,000 g) infants (51%) compared with infants > or = 1,000 g (46%).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute tubular necrosis in a newborn suffering from neonatal necrotizing enterocolitis

The case history of a newborn who at birth had a necrotizing enterocolitis, worsened by an acute tubular necrosis and anuresis, is presented. A continuous arteriovenous hemofiltration was instituted for the baby, who had previously undergone abdominal surgery with resection of the necrotic bowel. The hypothesis that necrotizing enterocolitis could be the cause of acute tubular necrosis in infancy is discussed.

Epidemiology of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a worldwide problem that has emerged in the past 25 years as the most common gastrointestinal emergency in neonatal intensive care units (NICU). In the United States the incidence ranges from 1 to 7.7% of NICU admissions. Ninety percent of the patients are premature infants. Mucosal injury, bacterial colonization and formula feeding are the three major pathogenetic factors that have been documented in most infants who have developed NEC. However, NEC may develop only if a threshold of injury, imposed by the coincidence of at least two of three events (intestinal ischemia, pathogenic bacteria, and excess of protein substrate) is exceeded. Immunological immaturity of the gut in premature babies may represent the crucial risk factor.

Pancreatic exocrine function and necrotising enterocolitis

Pancreatic protease deficiency may be an aetiological factor in enteritis necroticans, a disease sharing some features of necrotising enterocolitis (NEC). Using faecal chymotrypsin measurement we have prospectively studied pancreatic exocrine function in infants at risk of NEC. No significant difference was found comparing those infants who subsequently developed NEC and those who did not.

Necrotizing enterocolitis: a review of pathogenetic mechanisms and implications for prevention

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease of premature neonates that accounts for 3000 to 4000 deaths each year in the United States. The pathogenesis is not well understood, however theories suggest that prematurity, enteral feeding, bacterial colonization, and intestinal ischemia contribute to the intestinal injury. Furthermore, recent studies have shown that platelet activating factor and perhaps other inflammatory mediators mediate bowel necrosis in animals and possibly in humans. Although no specific intervention for NEC treatment exists, preventive therapy using either enteral IgA supplementation, breast milk feeding, antibiotic prophylaxis, or exogenous steroid administration have reduced the incidence of this overwhelming disease in small randomized trials. These modalities and perhaps PAF antagonists or other inflammatory mediator inhibitors may reduce the incidence or severity of NEC in the next several years.

Necrotizing enterocolitis: a continuing problem in the neonate

Necrotizing enterocolitis (NEC) is a syndrome of diverse etiologies with a significant mortality rate affecting mostly prematurely born stressed infants. Now recognized as a discrete entity, it had been poorly defined because other conditions seem to represent the same entity. A number of risk factors have been identified that appear to "trigger" NEC, though these have been questioned because they have been present just as frequently in premature and older infants who did not develop NEC as in those that did. Recently, maternal cocaine use has been added to the suspected risk factors. A steady improvement in the survival of babies with NEC has been due largely to a high index of suspicion of the disease and early, aggressive medical management.

Hypoxia-induced bacterial translocation in the puppy

Because hypoxia is one of the most common major stresses to which a neonate is exposed, we postulated that it alone might be the cause of intestinal bacterial translocation, which could be the underlying etiology of neonatal sepsis. An animal model, in which hypoxia is the sole stress, was developed in our laboratory and tested in 18 puppies to determine the effect of hypoxia and reoxygenation on intestinal bacterial translocation. In group I (n = 8), following laparotomy and cannulation of the superior mesenteric vein (SMV), the FIO2 was decreased from 21% to 9% for 90 minutes followed by reoxygenation at 21% for 120 minutes. The abdomen was closed and the animals were allowed to recover. After 24 hours the mesenteric lymph nodes (MLNs), spleen, and liver were harvested for bacterial determination and the ileum and jejunum for histological evaluation. Group II (n = 7) was treated the same as group I with the FIO2 maintained at 21%. Group III (n = 3) animals were killed, without intervention, for bacterial analysis. In group I, the systemic PO2 decreased by 75%, SMV PO2 decreased by 64%, and oxygen delivery to the small bowel decreased by 80% in comparison with group II. The mean arterial pressure and cardiac output were not significantly different between group I and group II; however, the mucosal blood flow was decreased by 60% (P less than .001) in group I. Arterial and SMV blood lactic acid levels were unchanged in group I in comparison with group II, suggesting that anaerobic metabolism was not initiated in the splanchnic circulation during hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Necrotizing enterocolitis of the neonate

Necrotizing enterocolitis is the most common gastrointestinal emergency in the newborn. The syndrome strikes premature infants during the first 2 weeks of life. Abdominal distention, lethargy, and feeding intolerance are early signs of NEC that may progress to gastrointestinal bleeding and hemodynamic instability. The radiographic hallmark of NEC is pneumatosis intestinalis (air in the bowel wall). The ileum and colon are the usual sites of crepitant intestinal necrosis, leading frequently to perforation. In spite of appropriate medical therapy, about half of the infants with NEC develop intestinal gangrene or perforation and require surgery, consisting of bowel resection and enterostomy formation. The most common late complication, intestinal stricture, occurs in 15 to 35 per cent of recovered infants. Overall mortality from NEC ranges from 20 to 40 per cent. The etiology of NEC is poorly understood and is considered to be multifactorial, related to ischemia, bacterial colonization, and formula feedings in a susceptible infant. Future progress in the treatment of NEC may be achieved by earlier detection of necrosis, modification of gastrointestinal flora, or by bolstering the deficient gastrointestinal immune mechanisms of the premature neonate.

The role of coagulase-negative Staphylococcus in neonatal necrotizing enterocolitis

Coagulase-negative Staphylococcus has emerged as a prominent pathogen in the neonatal intensive care unit and a recent report has implicated this organism in necrotizing enterocolitis (NEC). This same study suggests that Staphylococcus epidermidis is most commonly associated with a "mild form of enterocolitis." This prompted a review of the role of coagulase-negative Staphylococcus in the surgical complications of NEC. Between 1982 and 1986, 86 newborns underwent operation for perforation or intestinal necrosis secondary to NEC. Blood cultures, obtained within 72 hours of surgery, were positive in nine of 71 infants (13%). One third of these grew coagulase-negative Staphylococcus. Peritoneal cultures obtained at the time of operation were positive in 71 neonates. The incidence of Staphylococcus epidermidis was 30%. In a third of these cases, coagulase-negative Staphylococcus was the only organism covered. Overall mortality within the group was 33%. Coagulase-negative Staphylococcus was the single most frequent organism recovered from those infants who expired (35%). This data clearly indicates that Staphylococcus epidermidis must be considered as a significant pathogen in NEC. It is associated with both morbidity and mortality and, therefore, warrants appropriate aggressive therapy when recovered from the neonate with enterocolitis.

Surgery for necrotizing enterocolitis

Thirty-seven patients who had necrotizing enterocolitis and required emergency surgical intervention are reviewed. The indications for surgery were intestinal perforation (28), intestinal obstruction (7), clinical deterioration (1) and persistent rectal bleeding (1). The initial procedure was percutaneous peritoneal catheter drainage (13), intestinal diversion alone (8), intestinal resection (14), laparotomy and biopsy (1) and laparotomy alone (1). Twelve patients developed late intestinal strictures. The overall mortality rate was 35 per cent.

Comparative effects of ischemia, bacteria, and substrate on the pathogenesis of intestinal necrosis

This study was undertaken to evaluate the relative contribution of ischemia, bacteria, and luminal substrate, the pathogenetic components of necrotizing enterocolitis (NEC), to the development of intestinal necrosis. Sprague-Dawley rats, either germ-free (No. = 25) or conventionally colonized (No. = 20) underwent laparotomy. Isolated ileal segments were created, two per rat. Ischemia was produced in one segment by application of a microaneurysm clip; the other segment served as a control. Segments were injected with 1 mL of either normal saline, dilute Similac formula, or standard formula. Groups were as follows: Group I (germ-free), received saline; Group II (germ-free), dilute formula; Group III (germ-free), standard formula; Group IV (conventional), saline; Group V (conventional), dilute formula; Group VI (conventional), standard formula. At 48 hours, the rats were evaluated for survival, gross bowel integrity, histologic severity of necrosis (graded 0 to 4+), and bacteriology. Gross analysis of bowel integrity showed no lesions in the ischemic segments of the germ-free rats (Groups I, II, and III) and necrosis in 75% of conventionally colonized animals (Groups IV, V, and VI; P less than 0.001). Microscopic necrosis was more common (P less than 0.001) in ischemic segments of conventional rats than in ischemic segments of germ-free rats. There was no difference in necrosis attributable to ischemic time or to the presence of either standard or dilute formula. Of the three pathogenetic factors evaluated, the presence of bacteria was most crucial to the development of bowel necrosis in this model. Improved treatment and prevention of NEC may depend upon suppression and/or modification of the gut flora.

Long-term follow-up after surgical management of necrotizing enterocolitis: sixty-three cases

One hundred twenty-five infants underwent surgical intervention for necrotizing enterocolitis between 1972 and 1984. Sixty-three infants, who survived more than 30 days postoperatively, were evaluated for long-term complications. There were 28 girls and 35 boys (mean birth weight 1,725 +/- 890 g; gestational age 32 +/- 4 weeks). Associated problems included hyaline membrane disease (43), cardiac anomalies (25), and trisomy 21(2). Thirty-six survivors required long-term ventilatory support. Fifty-nine infants underwent bowel resection and enterostomy, 3 decompressing enterostomies without resection, and 1, exploratory laparotomy only. Enterostomies were closed at four months. Twenty four had short bowel syndrome. Fifteen infants subsequently died for a late mortality rate of 23%. Mortality was related to sepsis (3), respiratory failure (5), cardiac anomalies (3), cardio-respiratory arrest (2), and TPN related liver failure (2), and was common with gestational age less than 31 weeks and birth weight less than 1,000 g. Medical problems included cholestasis (17), TPN induced cirrhosis (3), meningitis (3), seizures (8), and nutritional rickets (6). Significant developmental and intellectual delays were observed.

Newborn surgical emergencies of the gastrointestinal tract

Intestinal obstruction and necrotizing enterocolitis are two of the most common surgical emergencies of the gastrointestinal tract. This article reviews the signs and symptoms of these conditions and presents guidelines for their management.

Significance of portal vein air in necrotizing entercolitis: analysis of 53 cases

Fifty-three of 177 infants with necrotizing enterocolitis (NEC) developed portal vein air (PVA). These infants were evaluated for prenatal, perinatal, therapeutic, clinical, laboratory, radiographic, and operative factors as they related to infants with and without PVA. A significantly higher incidence of PVA was seen in infants with NEC who weighed less than 2400 g (P less than 0.025). The use of Vitamin E (P less than 0.01), aminophylline, and high-density premature formula (P less than 0.001) was associated with an increased incidence of PVA. NEC totalis was seen in 55% of the infants with NEC and PVA (P less than 0.001). The presence of PVA was associated with a 58% mortality rate (P less than 0.05). Infants with NEC and PVA operated on prior to 1983 had a 71% mortality. Since 1983, seven of nine infants with NEC and PVA survived early operation using PVA as an indication for surgical intervention. In infants at risk for this highly lethal form of NEC, the avoidance of enteral feedings or altered dietary intake, cautious placement of arterial catheters and the judicious application of pharmacologic agents (eg, Vitamin E, aminophylline) is of importance in regard to prevention. These observations suggest that PVA is a sign of advanced disease and that these high-risk patients should be considered candidates for early surgical intervention.

Clostridial necrotizing enterocolitis

In a bacteriologic investigation of infants with necrotizing enterocolitis (NEC), 16 of 50 infants had clostridia in cultures of blood or of peritoneal fluid obtained by paracentesis. Twenty-eight of the 50 infants had enteric bacteria other than clostridia, and six infants had sterile cultures. Of the 16 infants with clostridia, nine had C. perfringens and seven had other species of clostridia. Compared to infants with nonclostridial NEC, those with clostridial NEC were larger and more mature, had more extensive pneumatosis intestinalis and gangrene and more rapid progression of NEC. The nine infants with C. perfringens had a fulminant form of NEC, analogous to gas-gangrene of the intestine. Mortality in this group was 78% (7/9). The seven infants with clostridial species other than C. perfringens had a mortality comparable to that of infants with nonclostridial NEC (32%). Improved survival from NEC associated with C. perfringens may be possible only by prevention, rather than earlier diagnosis and improved heroic treatment.

Laboratory basis for the medical management of necrotizing enterocolitis (NEC)

Necrotizing enterocolitis (NEC) is a serious condition affecting the neonate that may be responsive to medical management. This study evaluates the efficacy of supplemental oxygen (FiO2 40% and 50%), systemic antibiotics (ampicillin and gentamicin, cephamandole) and oral antibiotics (trimethoprim-sulfamethoxazole, neomycin and gentamicin) in a weanling rat bowel ischemia model induced by a transient (one minute) occlusion of the superior mesenteric artery. Animals were evaluated for overall survival, duration of survival, presence of bowel necrosis or perforation at seven days. Mortality in ischemic controls was 83.8%. This was reduced to 52% by FiO2 of 50%, and 40% with systemic ampicillin and gentamicin (with or without FiO2 50%) (P less than .001). Length of survival was 3.4 days in controls and increased from 5.4 to 5.9 days in rats given FiO2 50% and/or ampicillin and gentamicin (P less than .001). The incidence of bowel necrosis in controls was 60% and was reduced to 25% in rats given systemic ampicillin and gentamicin and 23.3% with 50% FiO2 and the same antibiotics (P less than .001). Systemic cephamandole and oral antibiotics had no beneficial effects.

Necrotising enterocolitis experience with 54 neonates

Fifty-four neonates transferred to the neonatal surgical unit because of acute necrotising enterocolitis (N.E.C.) are presented. Eleven died (20.4%), of whom seven were treated conservatively and four by operation. Ten patients required surgical exploration because of intestinal perforation, obstruction or suspected perforation. Another five neonates presented with intestinal perforation and were treated by percutaneous catheter drainage of the peritoneal cavity because of their extreme prematurity. Nine patients developed a colonic stricture diagnosed between six weeks and a year after the onset of the disease. Another six patients showed a segment of colonic narrowing detected on barium enema radiography without clinical evidence of bowel obstruction. They were treated conservatively and showed complete resolution at follow up studies.

A prospective evaluation of intestinal stenosis following necrotizing enterocolitis

In a retrospective study, we noted a 25% incidence of colonic stenosis following medical management of necrotizing enterocolitis (NEC). From March, 1980 to March, 1982, we performed routine contrast enemas to prospectively identify the incidence of colonic stenosis following medical management for NEC. Three to four weeks following recovery from the acute phase of NEC 28 infants were prospectively evaluated by contrast enema for post-NEC stenosis. Ten of the 28 infants had one or more sites of colonic stenosis (36%). Four infants were symptomatic when the contrast enema was performed and underwent colonic resection. Three of the six asymptomatic infants developed symptoms requiring surgery within 33 days following hospital discharge. Therefore, seven of the ten infants with post-NEC stenosis required segmental colectomy. Three patients with colonic stenosis have remained asymptomatic and are being followed on an outpatient basis. The weight gain in these three infants has been steady and has paralleled a normal growth curve. The data from this study demonstrate that: (1) the incidence of post-NEC colonic stenosis is 36%; (2) patients with colonic stenosis initially may not have symptoms but may become symptomatic after hospital discharge; (3) the sites of stenosis frequently are located in the left colon; and (4) normal weight gain can occur despite the presence of colonic stenosis. Because of the above findings, we recommend routine contrast enemas in all patients with NEC who have had successful medical management.