Epidemiologic and bacteriologic evaluation of neonatal necrotizing enterocolitis

Temporal and seasonal variations in incidence of stage II and III NEC-a 28-year epidemiologic study from tertiary NICUs in Connecticut, USA

OBJECTIVE

To investigate seasonality and temporal trends in the incidence of NEC.

STUDY DESIGN

A retrospective cohort study from two tertiary NICUs in northern and central Connecticut involving 16,761 infants admitted over a 28-year period. Various perinatal and neonatal risk factors were evaluated by univariate, multivariate, and spectral density analyses.

RESULTS

Incidence of NEC was unchanged over the 28 years of study. Gestational age, birth weight, and birth-months (birth in April/May) were independently associated with stage II or III NEC even after adjusting for confounding factors (p < 0.05). Yearly NEC incidence showed a multi-modal distribution with spectral density spikes approximately every 10 years.

CONCLUSION(S)

Temporal and seasonal factors may play a role in NEC with a peak incidence in infants born in April/May and periodicity spikes approximately every 10 years. These trends suggest non-random and possibly environmental factors influencing NEC.

Prediction of short-term neonatal complications in preterm infants using exome-wide genetic variation and gestational age: a pilot study

BACKGROUND

Preterm birth is the leading cause of mortality and morbidity in young children, with over a million deaths per year worldwide arising from neonatal complications (NCs). NCs are moderately heritable although the genetic causes are largely unknown. Therefore, we investigated the impact of accumulated genetic variation (burden) on NCs in non-Hispanic White (NHW) and non-Hispanic Black (NHB) preterm infants.

METHODS

We sequenced 182 exomes from infants with gestational ages from 26 to 31 weeks. These infants were cared for in the same time period and hospital environment. Eighty-one preterm infants did not develop NCs, whereas 101 developed at least one severe complication. We measured the effect of burden at the single-gene and exome-wide levels and derived a polygenic risk score (PRS) from the top 10 genes to predict NCs.

RESULTS

Burden across the exome was associated with NCs in NHW (p = 0.05) preterm infants suggesting that multiple genes influence susceptibility. In a post hoc analysis, we find that PRS alone predicts NCs (AUC = 0.67) and that PRS is uncorrelated with GA ([Formula: see text] = 0.05; p = 0.53). When PRS and GA at birth are combined, the AUC is 0.87.

CONCLUSIONS

Our results support the hypothesis that genetic burden influences NCs in NHW preterm infants.

Determinants of the Very Low-Birth-Weight Infant's Intestinal Microbiome: A Systematic Review

The intestinal microbiome is the genetic material from microorganisms residing in the intestinal tract. Very low-birth-weight infants (VLBW; birth weight ≤1500 g) are a physiologically compromised population undergoing a unique period of initial intestinal microbiome establishment. Evidence supports a connection between the intestinal microbiome and gastrointestinal illness that disproportionately affects VLBW infants. Necrotizing enterocolitis, an inflammatory and often necrotic condition of the intestine, and late-onset sepsis, a bloodstream infection occurring after 3 days of life, are thought to be associated with delayed or abnormal intestinal microbiome development. Here, we review the determinants, or factors, that influence the VLBW infant's intestinal microbiome and discuss clinical implications. PubMed, Web of Science, EMBASE, and CINAHL were systematically searched for publications addressing factors with the potential to affect the intestinal microbiome of VLBW infants. Results indicate that infant's age and weight, mode of delivery, antibiotic exposure, medication use, feeding regime, environment, and perinatal-/infant-associated factors may be important determinants of the microbiome in this vulnerable population. Clinicians have opportunities to support positive development of the VLBW infant's intestinal microbiome through antibiotic stewardship, support of human milk feeding, and hygienic care practices.

Pathophysiology of Necrotizing Enterocolitis: An Update

NEC is a devastating disease that, once present, is very difficult to treat. In the absence of an etiologic treatment, preventive measures are required. Advances in decoding the pathophysiology of NEC are being made but a more comprehensive understanding is needed for the targeting of preventative strategies. A better definition of the disease as well as diagnostic criteria are needed to be able to specifically label a disease as NEC. Multiple environmental factors combined with host susceptibility appear to contribute to enhanced risks for developing this disease. Several different proximal pathways are involved, all leading to a common undesired outcome: Intestinal necrosis. The most common form of this disease appears to involve inflammatory pathways that are closely meshed with the intestinal microbiota, where a dysbiosis may result in dysregulated inflammation. The organisms present in the intestinal tract prior to the onset of NEC along with their diversity and functional capabilities are just beginning to be understood. Fulfillment of postulates that support causality for particular microorganisms is needed if bacteriotherapies are to be intelligently applied for the prevention of NEC. Identification of molecular effector pathways that propagate inflammation, understanding of, even incipient role of genetic predisposition and of miRNAs may help solve the puzzle of this disease and may bring the researchers closer to finding a treatment. Despite recent progress, multiple limitations of the current animal models, difficulties related to studies in humans, along with the lack of a "clear" definition will continue to make it a very challenging disease to decipher.

Necrotizing Enterocolitis: Long Term Complications

Necrotizing enterocolitis (NEC) remains the most threatening gastrointestinal complication of prematurity leading to high mortality, morbidity and cost. Common complications of NEC include neurodevelopmental delay, failure to thrive, gastrointestinal problems including strictures and adhesions, cholestasis, short bowel syndrome with or without intestinal failure that can be difficult to manage. Infants who develop NEC benefit from close follow-up for early diagnosis and treatment of complications. Those who present with severe complications such as intestinal failure benefit from a multidisciplinary approach involving careful assessment and treatment. Studies done so far are limited in providing a long-term prognosis. Here we review some of these complications. More studies with a longer follow-up period are needed to better understand the later comorbidities that develop in babies with NEC.

Necrotizing enterocolitis in term infants

This article is an overview of NEC in term neonates and also summarizes data from 52 cases within Intermountain Healthcare during the last 11 years. In all 52, NEC occurred among neonates already admitted to a neonatal intensive care unit for some other reason; thus, NEC invariably developed as a complication of treatment, not as a primary diagnosis. The authors speculate that the incidence of term NEC can be reduced by identifying neonatal intensive care unit patients at risk for NEC and applying appropriate-volume human milk feeding programs for these patients.

Treatment of necrotizing enterocolitis with probiotics

Necrotizing enterocolitis (NEC) is a devastating condition characterized by diffuse intestinal inflammation and necrosis in preterm infants. It is the most common gastrointestinal emergency in the neonatal intensive care unit and is associated with significant morbidity and mortality. Primary risk factors include prematurity and low birth weight. Although the pathogenesis of NEC is complex and not entirely understood, it is known that an interplay between immature intestinal immune responses and the process of bacterial colonization is required for the development of this disease.

Neonates presenting with bloody stools and eosinophilia can progress to two different types of necrotizing enterocolitis

OBJECTIVE

We hypothesized that neonates with bloody stools and concomitant eosinophilia are likely to have atopic enteropathy rather than necrotizing enterocolitis (NEC).

STUDY DESIGN

This was a retrospective cross-sectional study using electronic medical records and paper charts. Records of neonates admitted to any Intermountain Healthcare NICU between 1 January 2005 and 30 June 2010 were eligible if 'bloody stools' were listed in any archive. Qualifying records were divided into two groups depending on whether or not within 72 h of passing bloody stool eosinophil counts were above the 95th percentile reference range limit for age.

RESULT

Bloody stools were identified in 275 predominantly Caucasian neonates. Fifty-four of these had eosinophilia and 221 had normal eosinophil counts. Those with eosinophilia were born at a slightly younger gestational age (31.3 ± 4.6 vs 32.6 ± 4.0 weeks, mean ± s.d., P=0.032). Contrary to our hypothesis, those with eosinophilia did not have a lower rate of pneumatosis or bowel resection, or death ascribed to NEC. Eosinophilia was more common among those who had a red blood cell (RBC) transfusion within 48 h before passing bloody stools (P<0.001). Those with a recent RBC transfusion were the only neonates to have NEC surgery or to die from NEC. Preceding the bloody stools, those with no antecedent transfusion had been fed a larger volume (P=0.014), and had trends toward receiving calorically enriched feedings (P=0.055) and recent addition of human milk fortifier (P=0.060). Eosinophil counts following RBC transfusion tended to increase for 3-6 days, but when bloody stools were not preceded by transfusion the eosinophil counts were more static over that period.

CONCLUSION

In this predominantly Caucasian group of neonates with bloody stools, the presence of eosinophilia did not identify a benign condition distinct from NEC. A total of 44% of these neonates had transfusion-associated NEC. Eosinophils could have a previously unrecognized role in the pathogenesis of this NEC subtype.

Fulminant necrotizing enterocolitis in a multihospital healthcare system

OBJECTIVE

A subset of necrotizing enterocolitis (NEC) cases is fulminant, characterized by rapid progression to death with massive bowel necrosis found at laparotomy or autopsy. We sought to identify and report all such cases in a multihospital healthcare system during the past 9 years and to characterize this entity using case-control methodologies.

STUDY DESIGN

This was a multicentered, cross-sectional, historic cohort study conducted using Intermountain Healthcare hospital patient data. All neonates who died of NEC within 48 h of onset, during 2001 to 2009, were compared with two matched control groups: (1) demographically matched controls who developed non-fulminant NEC, (2) demographically matched controls that did not develop NEC.

RESULT

During this period, 2 71 327 live births occurred in the Intermountain Healthcare hospitals. Of these, 318 had a diagnosis of NEC (Bell stage ≥II). Also during this period, 205 other neonates were transferred into an Intermountain hospital for treatment of NEC. Of these 523 NEC cases, 35 (6.7%) had a fulminant course. Compared with the non-fulminant cases, the fulminant group were born at lower weight (1088±545 vs 1652±817 g, P=0.000) and earlier gestational age (27.5±3.3 vs 31.1±4.4 weeks, P=0.000), and were more likely to have: (1) radiographic evidence of portal venous air (P=0.000), (2) hematocrit <22% (P=0.000), (3) increase in feeding volume >20 ml/kg/day (P=0.003), (4) immature to total (I/T) neutrophil ratio >0.5 (P=0.005), (5) blood lymphocyte count <4000/μl (P=0.018), (6) an increase in concentration of human milk fortifier within 48 h before developing NEC (P=0.020).

CONCLUSION

Portal venous air, anemia, rapid feeding escalation, a high I/T neutrophil ratio, a low lymphocyte count and recent increases in fortifier may all be associated with fulminant NEC.

Community analysis of bacteria colonizing intestinal tissue of neonates with necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in newborn neonates. Bacteria are believed to be important in the pathogenesis of NEC but bacterial characterization has only been done on human faecal samples and experimental animal studies. The aim of this study was to investigate the microbial composition and the relative number of bacteria in inflamed intestinal tissue surgically removed from neonates diagnosed with NEC (n=24). The bacterial populations in the specimens were characterized by laser capture microdissection and subsequent sequencing combined with fluorescent in situ hybridization (FISH), using bacterial rRNA-targeting oligonucleotide probes.

RESULTS

Bacteria were detected in 22 of the 24 specimens, 71% had moderate to high densities of bacteria. The phyla detected by 16S rRNA gene sequencing were: Proteobacteria (49.0%), Firmicutes (30.4%), Actinobacteria (17.1%) and Bacteroidetes (3.6%). A major detected class of the phylum Proteobacteria belonged to δ-proteobacteria. Surprisingly, Clostridium species were only detected in 4 of the specimens by FISH, but two of these specimens exhibited histological pneumatosis intestinalis and both specimens had a moderate to a high density of C. butyricum and C. parputrificum detected by using species specific FISH probes. A 16S rRNA gene sequence tag similar to Ralstonia species was detected in most of the neonatal tissues and members of this genus have been reported to be opportunistic pathogens but their role in NEC has still to be clarified.

CONCLUSION

In this study, in situ identification and community analysis of bacteria found in tissue specimens from neonates with NEC, were analysed for the first time. Although a large variability of bacteria was found in most of the analyzed specimens, no single or combination of known potential pathogenic bacteria species was dominating the samples suggestive NEC as non-infectious syndrome. However there was a significant correlation between the presence of C. butyricum & C. parputrificum and histological pneumatosis intestinalis. Finally this study emphasizes the possibility to examine the microbial composition directly on excised human tissues to avoid biases from faecal samples or culturing.

Seasonal variation in the incidence of necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) has been reported to occur in a sporadic manner and in clusters of cases. We hypothesized that variations in the incidence of NEC were random, without clustering. In order to define the pattern of NEC in the United States, we analyzed the Pediatric Health Information System (PHIS) database to evaluate whether NEC cases are distributed randomly or exhibit temporal clustering or periodicity.

METHODS

After obtaining IRB approval, we queried the PHIS database for all patients with NEC (ICD-9 code of 777.5) over a 13-year period. Sixteen children's hospitals were studied, and individual institutional and aggregate data were reviewed. Fisher's Kappa and Bartlett's Kolmogorov-Smirnov tests were used to identify periodicity.

RESULTS

During the study interval, there were 2,93,076 neonatal admissions, and 4,559 (1.6%) infants were diagnosed with NEC. Statistical analysis demonstrates a periodicity of 6 months in the occurrence of NEC. Fisher's Kappa was 16.924 and Bartlett's Kolmogorov-Smirnov was 0.281, which translates to a P value of <0.0001.

CONCLUSIONS

On the basis of a national database analysis it appears a temporally non-random distribution of NEC cases does exist.

16S rRNA gene-based analysis of fecal microbiota from preterm infants with and without necrotizing enterocolitis

Neonatal necrotizing enterocolitis (NEC) is an inflammatory intestinal disorder affecting preterm infants. Intestinal bacteria play a key role; however no causative pathogen has been identified. The purpose of this study was to determine if there are differences in microbial patterns which may be critical to the development of this disease. Fecal samples from twenty preterm infants, ten with NEC and ten matched controls (including four twin pairs) were obtained from patients in a single site Level III neonatal intensive care unit. Bacterial DNA from individual fecal samples were PCR amplified and subjected to terminal restriction fragment length polymorphism analysis and library sequencing of the 16S rRNA gene to characterize diversity and structure of the enteric microbiota. The distribution of samples from NEC patients distinctly clustered separately from controls. Intestinal bacterial colonization in all preterm infants was notable for low diversity. Patients with NEC had even less diversity, an increase in abundance of Gammaproteobacteria, a decrease in other bacteria species, and had received a higher mean number of previous days of antibiotics. Our results suggest that NEC is associated with severe lack of microbiota diversity which may accentuate the impact of single dominant microorganisms favored by empiric and wide-spread use of antibiotics.

Necrotizing enterocolitis during the first week of life: a multicentered case-control and cohort comparison study

OBJECTIVE

Necrotizing enterocolitis (NEC) is rare during the first week of life; most cases occur after 2 to 4 weeks. We hypothesized that when NEC develops in the first week, certain predisposing factors and feeding practices are identifiable. To test this, we sought to identify every case of NEC diagnosed during the first week within the Intermountain Healthcare system during the most recent 6-year period.

STUDY DESIGN

Data were collected from neonates admitted to any Intermountain Healthcare neonatal intensive care unit (NICU) with a date of birth from 1 January 2001 through 31 December 2006. Electronic and paper records were obtained for all with a diagnosis of NEC (Bell stage >or=II) within the first 168 h. X-rays, physician notes, nursing records, laboratory reports and operative reports were subjected to critical review to reexamine the diagnosis of NEC. Among those with confirmed NEC, we recorded underlying conditions and every feeding given prior to the diagnosis of NEC. Comparisons were made with patients that did not develop NEC, yet were cared for in the same NICUs, during the same period of time, and of the same gestational ages.

RESULT

A total of 28 neonates were identified electronically as having NEC during the first week. Critical review confirmed this in 21, but 5 were determined at laparotomy to have had spontaneous intestinal perforation, and 2 others were found on surgical reports to have had a congenital infarction of the colon. Total 20 of the 21 confirmed cases developed NEC while in a NICU being treated for another condition. The exception was a small-for-gestational-age neonate in a well baby nursery. Compared to 6100 controls, the 21 with early NEC were more likely to have had a meconium-positive test for illicit drug exposure (P<0.005), early onset sepsis (P<0.034) and respiratory distress (P<0.039). They were less likely than case-controls to have been fed human milk (P=0.003) and were more likely to have been fed formula exclusively (P=0.019). None who were fed human milk exclusively developed early NEC. Twelve of the twenty-one were fed (by gavage or bottle) amounts exceeding the upper limit of volumes taken by breastfed neonates.

CONCLUSION

We speculate that the prevalence of NEC during the first week could be reduced by identifying at-risk patients, feeding them human milk exclusively for the first week and using feeding volumes that do not exceed that taken by healthy breastfed neonates.

Comparaison entre le nombre et la nature des clostridium fécaux et d'autres facteurs de risque impliqués dans la pathologie intestinale des nouveau-nés

Cent quinze nouveau-nés, âgés de 31 jours au plus et hospitalisés dans deux unités de soins intensifs, ont été groupés en 6 classes d'après le diagnostic clinique (entérocolite avec ou sans examen anatomopathologique et avec ou sans pneumatose radiologique, ≪ colites hémorragiques ≫, diarrhée aiguë, absence de troubles digestifs). Le nombre total de bactéries cultivables et le nombre de Clostridium ont été déterminés dans leurs selles. Dans certaines selles, on a également recherché la présence de rota- et/ou de coronavirus. Les effectifs de nouveau-nés souffrant d'entérocolites, avec ou sans pneumatose, ou de colites hémorragiques dont les selles contiennent des Clostridium ne sont pas significativement différents de ceux des nouveau-nés sans trouble digestif, alors que les selles de nouveau-nés atteints de diarrhée aiguë contiennent moins fréquemment des Clostridium que celles des autres nouveaunés. Les Clostridium identifiés appartiennent aux espèces C. butyricum, C. perfringens, C. difficile, C. tertium et C. sordellii. L'analyse des correspondances comparant la variable classe de diagnostic à 23 autres variables suggère que les variables suivantes: gémellité, poids de naissance < 1900 g, âge gestationnel < 35 semaines, détresse respiratoire, pose d'un cathéter ombilical et nombre de Clostridium > 10⁷/g de selle à l'apparition des signes cliniques, soit entre le 8^e et le 12^e jour de vie, sont liées au diagnostic d'entérocolite avec pneumatose. A l'opposé, l'absence de gémellité, un poids de naissance et un âge gestationnel élevés, l'absence de troubles respiratoires, de cathétérisme ombilical et de Clostridium fécaux, l'apparition des premiers signes cliniques à un âge inférieur à 8 jours, mais la présence de rota- et/ou de coronavirus dans les selles, sont liés au diagnostic de diarrhée aiguë.

Necrotizing enterocolitis in term neonates: data from a multihospital health-care system

OBJECTIVE

In the past 5(1/2) years, 30 term or near-term neonates in the Intermountain Healthcare system developed necrotizing enterocolitis (NEC) Bell's stage > or =II. We sought to identify possible explanations for why these patients developed NEC, by comparing them with 5847 others that did not develop NEC, from the same hospitals and of the same gestational ages, cared for during the same 5 1/2-year period.

STUDY DESIGN

Data were collected from neonates admitted to any of the Intermountain Healthcare NICUs with a birth date from 1 January 2001 to 30 June 2006, and a gestational age >36 weeks. A variety of patient features and feeding practices were compared between those that did vs did not develop NEC.

RESULT

Forty-one neonates >36 weeks gestation were listed in the discharge records as having NEC of Bell's stage II or higher. However, on review of these 41 medical records, 11 were seen to have had NEC of Bell's stage I, whereas the remaining 30 had radiographs and clinical courses indicative of Bell's stage > or =II. Those 30 formed the basis of this study. Twenty-eight of the 30 developed NEC after having been admitted to an NICU for some other reason; the other two developed NEC at home, within 2 days of being discharged from an NICU. The 30 that developed NEC were more likely than the 5847 that did not develop NEC, to have congenital heart disease (P=0.000), polycythemia (P=0.002), early-onset bacterial sepsis (P=0.004) or hypotension (P=0.017). All 30 received enteral feedings before NEC developed; 29 were fed either artificial formula or a mixture of formula and breast milk. The one that was exclusively fed human milk was fed human milk with added fortifier (24 cal/oz). The 30 that developed NEC were more likely to be fed formula exclusively (P=0.000). Seven of the 30 had a laparotomy for NEC; two of the seven had total bowel necrosis and support was withdrawn. The other five had perforations and bowel resections. The mortality rate was 13% (4/30).

CONCLUSION

In our series, NEC among term or near-term neonates was exclusively a complication developing among patients already admitted to a NICU for some other reason. We speculate that the combination of reduced mesenteric perfusion and feeding with artificial formula were factors predisposing them to develop NEC.

Gastrointestinal development and meeting the nutritional needs of premature infants

The fear of necrotizing enterocolitis and feeding intolerance are major factors inhibiting the use of the enteral route as the primary means of nourishing premature infants. Parenteral nutrition may help to meet many of the nutritional needs of these infants, but has significant detrimental side effects that include intestinal atrophy, sepsis, and increased susceptibility to inflammatory stimuli and systemic inflammatory responses. Being able to minimize the use of the parenteral route and still maintain appropriate nutrition safely would be a major advance in neonatology. At the basis of our inability to use the enteral route is a poorly understood immature gastrointestinal tract. Approaches such as minimal enteral nutrition or trophic feedings may partially alleviate these problems. However, if we are to progress in greater utilization of the gastrointestinal tract, other factors need to be considered. These include the macronutrient composition of minimal enteral or trophic feedings and the microecology of the intestinal lumen. Some of the developmental aspects of the intestine, which include intestinal growth, motor activity, barrier and other innate immune functions, and the microecology of the developing intestine, are briefly reviewed here. The purpose of this review is to suggest important areas of future research in neonatal and developmental gastroenterology that could affect several conditions that are related to immaturity of the gastrointestinal tract.

The epidemiology and pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC), a syndrome characterized by crepitant necrosis of the bowel, has emerged as the most common neonatal gastrointestinal emergency in many countries of the world. In the United States, NEC strikes 1 to 8% of patients admitted to neonatal intensive care units, almost all of whom are premature infants. The incidence is low in certain countries wity a low premature birth rate, e.g., Japan. Two theories of pathogenesis are: the Santulli theory, which implicates three factors: ischaemia, bacteria and substrate; and the Lawrence theory, which stresses the injurious role of bacterial toxins on the immature gut of the preterm infant. Clinical and experimental evidence support each of the theories, but neither theory can explain certain clinical phenomena, particularly the resistance to NEC manifested by more than 90% of preterm infants, who never develop the syndrome. A unifying hypothesis of pathogenesis and a mathematical model of NEC are outlined. Because clustering of cases may occur, the design of clinical trials of preventive measures for NEC must include simultaneous control infants.

Neonatal necrotizing enterocolitis: an update

Necrotizing enterocolitis (NEC) is a leading cause of mortality and morbidity in neonatal intensive care units. Here we review selected manifestations of NEC, risk factors involved in its pathophysiology as well as putative mechanisms associated with how an immature gut might be more susceptible to NEC. Treatment and potential preventive strategies are discussed.

Effects of mode of delivery and necrotising enterocolitis on the intestinal microflora in preterm infants

To investigate the effects of mode of delivery and of necrotising enterocolitis on the faecal microflora, 140 infants born before 33 weeks of gestation were followed up for symptoms of necrotising enterocolitis. Stool samples for gas-liquid chromatography and culture were collected twice weekly, and, when necrotising enterocolitis was suspected, for 2 months. For each infant with necrotising enterocolitis (n=21), two control infants matched for birth weight and gestational age were selected from the remaining study population. In gas-liquid chromatography analysis, the faecal bacterial microflora of infants born via caesarean section differed significantly from the gut microflora of those born via the vaginal route. The intestinal microflora showed a significant alteration in the necrotising enterocolitis group at time of diagnosis. At the onset of necrotising enterocolitis, faecal colonisation with Enterococcus species and Candida albicans was significantly more frequent in symptomatic infants than in controls. In infants with positive blood cultures and positive intestinal biopsy cultures, concomitant stool samples revealed the same microbial pathogens. In conclusion, the intestinal microbial colonisation in preterm infants born by caesarean section differs from that in preterm infants born via the vaginal route. A significant change in faecal microbial colonisation seems to occur at the onset of necrotising enterocolitis. Pathogens detected in the stools at that time might have a causative role in the development of the disease.

Nutritional impact of pre- and probiotics as protective gastrointestinal organisms

The health benefits of pre- and probiotics have been the subject of increased research interests. These food supplements have been demonstrated to alter the pre-existing intestinal flora so as to provide an advantage to the host. This review focuses on the scientific evidence both for and against their role in promoting health and treating disease. Specific attention is turned to their effects on immunomodulation, lipid metabolism, cancer prevention, diarrhea, Helicobacter pylori, necrotizing enterocolitis, allergy, and inflammatory bowel disease.

Necrotizing enterocolitis: pathophysiology and prevention

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in the neonatal intensive care unit. It is a disease of medical progress in that more very low-birth-weight neonates are surviving than ever before and are thus susceptible to this potentially devastating disease. NEC received very little attention in the literature before the 1970s but now is well known to all neonatologists and pediatric surgeons. The 1500 to 2000 infants that die every year from this disease in the United States and the large number of infants who develop short gut syndrome from this disease only represent the tip of the iceberg of the problems NEC causes. The widespread fear of NEC among neonatologists and pediatric surgeons has contributed in large part to the use of the IV route rather than the gastrointestinal tract for nourishing these infants for relatively long periods. The consequences of this include a high incidence of sepsis, high hospital costs, and potential long-term neurodevelopmental disability because of poor nutrition during a very vulnerable period of growth and development. The purpose of this review is to provide a brief overview of the clinical presentation and current treatment for NEC, then provide a discussion of the pathophysiology on which strategies for prevention can be formulated.

Early administration of Bifidobacterium breve to preterm infants: randomised controlled trial

AIM

To investigate the colonisation with Bifidobacterium breve of the bowels of very low birthweight (VLBW) infants.

METHODS

The adverse effects of B breve were examined in 66 VLBW infants (preliminary study). A prospective randomised clinical study of 91 VLBW infants was also completed and these infants were followed up for three years. Precise viable bacterial counts of serial stool specimens were examined for the first eight weeks after birth in 10 infants. The colonisation rates of administered bacteria were examined using immunohistochemical staining of stool specimens with a B breve specific monoclonal antibody.

RESULTS

In the preliminary study there were no side effects attributable to the bacteria. Immunohistochemical staining of stool specimens showed that the colonisation rates of the administered bacteria were 73% at 2 weeks of age, but only 12% in the control group. Early administration of B breve significantly decreased aspirated air volume from the stomach and improved weight gain.

CONCLUSIONS

B breve can colonise the immature bowel very effectively and is associated with fewer abnormal abdominal signs and better weight gain in VLBW infants, probably as a result of stabilisation of their intestinal flora and accelerated feeding schedules.

Necrotizing enterocolitis: the search for a unifying pathogenic theory leading to prevention

During the past two decades, necrotizing enterocolitis has emerged as a major cause of mortality and morbidity in premature infants. The specific cause of the disease remains enigmatic, but several putative risk factors provide clues to a pathophysiology that seems to be multifactorial. With the use of newly developed scientific tools, an understanding of the basic pathophysiologic cascade that causes necrotizing enterocolitis is emerging, providing hope for improved treatment and prevention.

Epidemiology of necrotizing enterocolitis

The descriptive epidemiology of necrotizing enterocolitis (NEC) is presented. Areas addressed include incidence, race, sex, age of onset, mortality rates, and endemic versus epidemic disease. Both descriptive and case control studies are reviewed to uncover clues relevant to the causes, pathogenesis, and prevention of NEC.

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.

Necrotizing enterocolitis prophylaxis: oral antibiotics and lyophilized enterobacteria vs oral immunoglobulins

We conducted a prospective randomized trial to compare the efficacy of oral gentamicin versus oral IgA-IgG for the prophylaxis of necrotizing enterocolitis (NEC); 200 newborns considered at high risk for NEC were assigned to group A (oral IgA-IgG, n = 100) or group B (oral Gentamicin, n = 100). NEC was diagnosed in 13 cases in group A and in 1 case in group B between the 3rd and 16th days of life. Surgical treatment was necessary in 3 cases (2 in group A). All infants survived. We conclude that oral gentamicin is more effective than oral IgA-IgG in the prevention of NEC in infants at high risk.

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.

Quantitative changes in faecal microflora preceding necrotising enterocolitis in premature neonates

Quantitative studies of faecal bacterial flora were carried out during the week preceding the clinical onset of 12 episodes of neonatal necrotising enterocolitis. There were considerable quantitative changes in the faecal flora preceding the clinical onset of both definite and possible episodes of necrotising enterocolitis. There was a decline in the numbers of some species from up to 72 hours before the clinical onset of the disease. Enterobacteriaceae were isolated from samples collected during the 48 hours preceding the clinical onset of all four definite episodes of necrotising enterocolitis. These were 'new' isolates in two episodes, and considerably increased numbers in another. The changes that we found are probably the result of changes in intraluminal conditions that precede the clinical onset of necrotising enterocolitis.

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.

Cocaine exposure in a term neonate. Necrotizing enterocolitis as a complication

Cocaine use has increased dramatically in the past several years, and multiple medical complications associated with its use have been reported in adults, including bowel infarction and colitis. Maternal use of cocaine during pregnancy has been associated with complications in the fetus and newborn infant, including spontaneous abortions, preterm labor, cerebral infarctions, seizures, renal anomalies, and neurobehavioral and neurophysiologic abnormalities. This paper presents a case of necrotizing enterocolitis at birth in a term newborn exposed to cocaine antenatally. Cultures of the bowel grew two types of Clostridia organisms, Escherichia coli and group B streptococcus. It is suggested that bowel ischemia was secondary to the vasoconstrictive properties of the maternally abused cocaine and that secondary invasion of the bowel by multiple bacteria ensued. This case presents another possible complication to the newborn of maternal cocaine exposure in utero, namely ischemic infarction of the bowel.

A randomized, controlled trial of parenteral clindamycin in neonatal necrotizing enterocolitis

For an assessment of the efficacy of clindamycin in preventing bowel necrosis (intestinal gangrene or perforation), 42 premature infants with radiographically confirmed necrotizing enterocolitis (NEC) (pneumatosis, intraportal gas, or both) were randomly assigned to receive parenterally either ampicillin and gentamicin (control group, n = 22) or ampicillin, gentamicin, and clindamycin (n = 20), 20 mg/kg/d at 8-hour intervals for 10 to 14 days. Infants who had received antibiotics for greater than 24 hours before randomization and those developing intestinal gangrene or perforation less than 12 hours after randomization were excluded. Intestinal gangrene or perforation developed in four infants in the control group and six in the clindamycin group. Four in each group died of NEC. In the control group, one of 18 survivors developed a late stricture requiring surgical resection, whereas six of 15 survivors in the clindamycin group developed such strictures (P = 0.022). Routine inclusion of clindamycin in medical treatment of NEC does not reduce the frequency of intestinal gangrene or perforation and may be associated with an increase in late stricture formation.

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.

Intestinal flora in the second week of life in hospitalized preterm infants fed stored frozen breast milk or a proprietary formula

Twenty infants fed stored frozen breast milk or a proprietary formula only had both aerobic and anaerobic cultures performed at a chronologic age of 8 to 14 days. Nine out of 10 stools from the infants fed stored frozen breast milk contained Enterobacteriaceae and one stool was sterile. One contained a Pseudomonas species; one contained anaerobic gram-positive rods; one contained anaerobic gram-negative rods; and four contained anaerobic gram-positive cocci. No anaerobes were found in six stools. Six stools had aerobic gram-positive cocci, none of which was hemolytic. Nine out of 10 stools from infants fed a proprietary formula had Enterobacteriaceae. Six stools had anaerobic gram-positive rods, three had anaerobic gram-negative rods, and four had gram-positive cocci. Four stools had no anaerobic bacteria. All 10 stools had nonhemolytic aerobic gram-positive cocci. Enterobacteriaceae were predominant in the stools of the infants fed either stored frozen breast milk or a proprietary formula, and the colony counts of aerobic bacteria were similar in both groups. This pattern of intestinal flora in hospitalized preterm infants in the second week of life is very different from that of normal term infants and may contribute to their increased incidence of systemic and localized infections. The use of stored frozen breast milk for the purpose of suppressing coliform and other potentially pathogenic organisms may not be effective in hospitalized preterm infants who have been treated previously with broad-spectrum, parenteral antibiotics.

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.

Quantitative study of the aerobic and anaerobic faecal flora in neonatal necrotising enterocolitis

Faeces from 24 neonates with proved necrotising enterocolitis (NEC), from 12 with clinically suspected NEC, and from 41 control infants were quantitatively cultured under aerobic and anaerobic conditions. An important difference in colonisation with Klebsiella was found between the NEC groups and the control group. Although the cause of NEC is unknown, colonisation with Klebsiella seems to increase the risk.

Anaesthetic implications of neonatal necrotizing enterocolitis

A retrospective analysis of infants with necrotizing enterocolitis was done to evaluate the effects of preoperative abnormalities upon anaesthesia and mortality. Mortality was significantly increased in infants weighing less than 1500 grams (p less than .001). Sixty-nine per cent of the infants had hyaline membrane disease and 35 per cent had platelet counts less than 50 X 10(9) cells/litre (50,000/mm3). Perioperative problems include peritonitis, sepsis, hypovolaemia, acidosis, and prematurity. Other ramifications of prematurity and anaesthesia are discussed.

A bacteriologic basis for the clinical presentations of necrotizing enterocolitis

A study to identify putative bacterial pathogens in infants with necrotizing enterocolitis (NEC) was begun in 1976. Cultures of blood and of peritoneal fluid obtained by paracentesis were carried out in 25 infants with NEC. Segments of intestine excised at operation were Gram stained. Of the 25 infants, 8 recovered with medical management and 17 required operations. The 8 medically treated infants had sterile peritoneal fluid and, with 2 exceptions, sterile blood cultures. Of the 17 operated infants, 16 had bacteria in their blood and/or peritoneal fluid. The majority of resected bowel specimens from these infants contained a confirmatory morphologic type of bacterium within the wall. The clinical course of 8 infants with clostridia was compared to that of 8 infants with gram-negative enteric bacteria (Klebsiella, E. coli, or Bacteroides fragilis). The infants with clostridia were sicker. They had more extensive pneumatosis intestinalis, a higher incidence of portal venous gas, more rapid progression to gangrene, and more extensive gangrene. Infants with gram-negative rods had lower birth weights and lower platelet counts than the clostridial group. The difference in mortality between the two groups was not significant. The inherent pathogenicity of the gut flora may influence the clinical course of NEC. Among infants who develop intestinal gangrene, the clostridia appear to be more virulent than gram-negative enteric bacteria.

Necrotizing enterocolitis following operation in the neonatal period

Necrotizing enterocolitis (NEC) usually occurs in low birth weight infants who have had perinatal stress, and the mortality remains significant. There are a few reports of NEC in the postoperative period, especially in young infants. Nine neonates developed NEC following operations and form the basis of this report. The interval between operation and the diagnosis of NEC varied from 3 days to 4 mo. The surgical lesions included one case each of esophageal atresia, tetralogy of Fallot, supralevator rectal atresia with rectourethral fistula, and multiple intestinal atresias. Three babies had gastroschisis and two had "apple peel" intestinal atresia. Only 3 of the 9 survived. The usual clinical findings of NEC, abdominal distention, bile stained gastric residuals and diarrhea (with or without blood), can occur in the postoperative period without NEC and are, therefore, not reliable diagnostic signs. Significant changes in the clinical course of these babies occurred from 7 hr to 5 days before the diagnosis was established. In these patients the roentgen findings that established the diagnosis of NEC included intestinal ileus, pneumatosis intestinalis, and portal vein gas. Pneumatosis intestinalis and portal vein gas were the most reliable diagnostic signs, but appeared relatively late in the course of the disease. In one case pneumatosis was seen only in retrospect. None of the patients had definite pneumoperitoneum. Awareness of NEC as a potential postoperative complication may result in early recognition, treatment and survival.