Necrotising enterocolitis of the newborn--is it gas-gangrene of the bowel?

An update on the human and animal enteric pathogen Clostridium perfringens

Clostridium perfringens, a rapid-growing pathogen known to secrete an arsenal of >20 virulent toxins, has been associated with intestinal diseases in both animals and humans throughout the past century. Recent advances in genomic analysis and experimental systems make it timely to re-visit this clinically and veterinary important pathogen. This Review will summarise our understanding of the genomics and virulence-linked factors, including antimicrobial potentials and secreted toxins of this gut pathogen, and then its up-to-date clinical epidemiology and biological role in the pathogenesis of several important human and animal-associated intestinal diseases, including pre-term necrotising enterocolitis. Finally, we highlight some of the important unresolved questions in relation to C. perfringens-mediated infections, and implications for future research directions.

Clostridial Infections in Children: Spectrum and Management

Clostridia can cause unique histotoxic syndromes produced by specific toxins (e.g., gas gangrene and food poisoning) as well as non-syndromic infections (e.g., abscess, local infections, and blood born infection). Clostridia can also be recovered from various body sites as part of polymicrobial aerobic-anaerobic infection. These include intra-abdominal (peritonitis and abscess), biliary tract, female genital tract, abscess (rectal area and oropharyngeal), pleuropulmonary, central nervous system, and skin and soft-tissue infections. Clostridia were recovered from children with bacteremia of gastrointestinal origin, necrotizing enterocolitis, and sickle cell disease. They have also been isolated in acute and chronic otitis media, chronic sinusitis and mastoiditis, peritonsillar abscesses, and neonatal conjunctivitis. Early and aggressive surgical debridement, decompression, and drainage of affected tissues are critical to successful outcome of histotoxic infections. Effective antimicrobials include penicillin, clindamycin, chloramphenicol, third-generation cephalosporins, carbapenems, and vancomycin.

Pneumatosis intestinalis as the initial presentation of systemic sclerosis: a case report and review of the literature

Introduction. Pneumatosis intestinalis (PI) is an uncommon pathology characterised by the presence of gas within the intestinal wall. It has been associated with various conditions, including connective tissue diseases. This is the first report of PI being the initial presentation of systemic sclerosis. Case Presentation. The patient, a 75-year-old female, presented with an 8-month history of worsening dysphagia and epigastric pain, as well as other nonspecific symptoms. Initial investigations with an oesophagogastroduodenoscopy diagnosed Candida oesophagitis and also identified an extrinsic compression of the gastric antrum. Subsequently a CT scan of the abdomen and pelvis showed moderately dilated small bowel loops and PI. Due to the patient's stability, non-critical clinical condition, conservative management was instituted. More detailed investigations confirmed the diagnosis of systemic sclerosis with positive anticentromeric and antinuclear antibodies. The patient improved on methotrexate and was discharged with appropriate outpatient follow-up. Discussion. PI is a rare but well-documented pathology associated with connective tissue diseases, such as systemic sclerosis. In most cases, conservative management is preferable to surgical intervention, depending on the patient's clinical presentation and progress. This is the first report of PI being the initial presentation of a patient with systemic sclerosis responsive to conservative management.

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.

Necrotizing enterocolitis of the neonate with Clostridium perfringens: diagnosis, clinical course, and role of alpha toxin

The severity of the clinical course in necrotizing enterocolitis (NEC) associated with Clostridium perfringens (Cp) may support the hypothesis of a specific disease. We conducted a case control study of infants diagnosed with NEC, who underwent surgical treatment over a 7-year period. Patient histories examined characteristics of the infants, bacterial infection as well as NEC's severity, antibiotic treatment, and clinical course. Infants infected with NEC associated with Cp were compared with NEC patients without Cp. The alpha toxin from Cp type A was detected in most of the isolated strains. Cp was identified as a causative agent of NEC in nine cases. As compared with the control group (n = 32), the onset of disease was earlier in life, the clinical course more severe, and patients had a larger extent of gangrene. Portal venous gas was evident in 77% of all Cp cases, as compared to 25% in the control group. The mortality rate was 44% in the Cp group, and only 18.7% in the control group. Type A Clostridium perfringens was identified in six cases. In each isolate alpha toxin production was proven, but without any correlation to the severity of the clinical course, the extent of intestinal gangrene or mortality. In premature infants NEC in conjunction with Cp seems to be more severe than other NEC cases; it also entails higher mortality and morbidity. Alpha toxin concentrations do not correlate with the severity of the disease. Portal venous gas is highly suggestive for the diagnosis of Cp infection.

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.

Role of micro-organisms in necrotizing enterocolitis

The frequency with which necrotizing enterocolitis occurs in outbreaks makes it likely that the illness can have an infective origin. Immunological and non-immunological defences of the gastrointestinal are impaired in early life. Consequently the gut of the preterm infant is predisposed to bacterial overgrowth. A wide range of pathogenic bacteria and viruses have been isolated from infants with necrotizing enterocolitis or detected histologically. The presence of bacterial metabolites in the breath, intestinal bullae (hydrogen) and urine (D-lactate) during the course of the illness is further confirmatory evidence. The presence of bacteria or bacterial products (such as exo- and endotoxin) in the circulation will lead to ischaemia of the intestine and other organs either directly or via mediators such as cytokines or platelet activating factor. Future studies in necrotizing enterocolitis should be directed to understanding and modulating inflammatory mediators in necrotizing enterocolitis and preventing the disease with breast milk and nutritional supplements (glutamine, short chain fatty acids), chemoprophylaxis, and antibodies.

Clostridial infection in children

A survey of the isolation of Clostridium spp. from 1543 specimens sent to anaerobic microbiology laboratories revealed 113 isolates from 107 specimens (7.0% of all specimens) from 96 children. The isolates comprised 43 (38%) unidentified Clostridium spp., 37 (33%) C. perfringens, 13 (12%) C. ramosum, five (4%) C. innocuum, six (5%) C. botulinum, three (3%) C. difficile, two (2%) C. butyricum, and one isolate each of C. bifermentans, C. clostridiiforme, C. limosum and C. paraputrificum. Most clostridial isolates were from abscesses (38), peritonitis (26), bacteraemia (10), and chronic otitis media (7). Predisposing or underlying conditions were present in 31 (32%) cases. These were immunodeficiency (12), malignancy (9), diabetes (7), trauma (7), presence of a foreign body (6) and previous surgery (6). The clostridia were the only bacterial isolates in 14 (15%) cases; 82 (85%) cases had mixed infection. The species most commonly isolated with clostridia were anaerobic cocci (57); Bacteroides spp. (B. fragilis group) (50), Escherichia coli (22), pigmented Prevotella or Porphyromonas spp. (18) and Fusobacterium spp. (10). Most Bacteroides and Escherichia coli isolates with clostridia were from abdominal infections and skin and soft tissue infections adjacent to the rectal area; most pigmented Prevotella and Porphyromonas isolates were from oropharyngeal, pulmonary, and head and neck sites. Antimicrobial therapy was given to all patients, in conjunction with surgical drainage in 34 (35%). Only two patients died. These data illustrate the importance of Clostridium spp. in paediatric infections.

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: 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.

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.

Intravenous metronidazole in the newborn

Twenty four neonates at high risk of anaerobic sepsis were treated with intravenous metronidazole, 7.5 mg/kg, 8 hourly, for a mean period of 5 days. The highest observed concentration after the first dose (mean +/- SD) 9.6 +/- 4.0 mg/l (56.1 +/- 23.4 mumol/l) was significantly lower (P less than 0.001) than the highest observed concentration after the final dose (mean +/- SD) 19.3 +/- 8.6 mg/l (112.7 +/- 50.2 mumol/l). The overall metronidazole half life was (mean +/- SD) 23.4 +/- 13.1 hours. The half life after the first dose (mean +/- SD) 21.9 +/- 10.1 hours was not appreciably different from the half life after the final dose (mean +/- SD) 21.6 +/- 12.4 hours. The concentrations of the major metabolite of metronidazole (20396RP) also rose appreciably during treatment. No side effects of metronidazole were noted and its extended half life in neonates suggests that less frequent dosage would be appropriate.

Acute necrotizing colitis and obstruction

Acute necrotizing colitis is a rare complication of colonic obstruction. Six cases occurring during a 20-month period are described. The presenting features were those of colonic obstruction with shock but without perforation. At laparotomy changes ranged from mucosal necrosis to frank gangrene in the colon proximal to the obstructing lesion. Gram stains of resected colon showed Gram-positive bacilli, resembling clostridia, invading the mucosa and submucosa. Two patients treated by defunctioning colostomy alone died but the remaining 4 survived after total colectomy. The cause is not known but raised intraluminal pressure may result in terminal mucosal ischaemia allowing anaerobic organisms to invade the bowel wall.

The prevalence of Clostridium difficile and toxin in a nursery population: a comparison between patients with necrotizing enterocolitis and an asymptomatic group

During a period when certain neonates in our nursery developed necrotizing enterocolitis, we studied stool specimens from a population of symptomatic and asymptomatic patients for the presence of Clostridium difficile and its toxin. The presence of the organism among nursery personnel and in the nursery environment was also evaluated. Results showed that five symptomatic neonates and 17 asymptomatic neonates in a population of 37 patients studied in our neonatal intensive care and intermediate care nurseries had positive stool cultures for C. difficile. Toxin was detected in stool from four of five symptomatic patients and was present at dilutions of greater than 1/125 in stool from six asymptomatic patients who were culture positive for C difficile. The organism was not found in stool samples from any nursery personnel but was recovered from the hand culture of a nursery worker and from the inanimate environment. Although our findings support the notion of nosocomial spread of C difficile, we were unable to clearly implicate the organism as the cause of necrotizing enterocolitis in our nursery.

Evidence for an immune complex vasculitis in neonatal necrotising enterocolitis

Despite many attractive hypotheses, neonatal necrotising enterocolitis (NNEC) remains a disease of unknown aetiology. By means of the immunofluorescent direct sandwich technique we have demonstrated immune complex deposition in the small vessels of the diseased bowel wall. We believe this is the first report of evidence of an immunological reaction occurring in this disease.

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.

Neonatal necrotizing enterocolitis: implications for an infectious disease

There is a broad spectrum of presentations and severity of necrotizing enterocolitis. Because it may have several different causes, ncerotizing enterocolitis may be a syndrome rather than a specific disease. The triad of formula feeding, intestinal ischemia, and bacterial growth may be part of the pathogenesis of necrotizing enterocolitis. Bacteria are of central importance for the production of pneumatosis, a prerequisite of which is formula feeding. Bacteria may also contribute to the intestinal injury seen after ischemia. However, the disease in the low risk patient seen during an epidemic associated with a single organism is probably caused by a primary gastrointestinal infection. On the other hand, in the stressed newborn infant with mucosal injury the presence of the appropriate bacteria may be all that is needed to initiate the chain of events leading to necrotizing enterocolitis. Figure 2 illustrates the importance of bacteria in all the causes proposed to be involved in the pathogenesis of necrotizing enterocolitis. Whether bacteria are primary or secondary agents, necrotizing enterocolitis should always be approached therapeutically as an infectious disease.

Epidemiologic and bacteriologic evaluation of neonatal necrotizing enterocolitis

The incidence of necrotizing enterocolitis (NEC) in our neonatal unit has varied from 4.7% to zero to 4.4% during three time periods. Simultaneously, significant changes have occurred in the spectrum of bacterial species in the gastrointestinal tract of unaffected infants in the same unit. During the first period of increased attack rate, 82% of gastric and 88% of fecal Enterobacteriaceae were E. coli and K. pneumoniae. When the attack rate decreased the frequencies were 11% (gastric) and 47% (fecal), and P. mirabilis was retrieved with increased frequency. The return of E. coli and K. pneumoniae as the dominant organisms was associated with an increase in NEC. Infants with NEC, compared with controls, had a statistically significant increased frequency of retrieval of E. coli and K. pneumoniae from gastric and fecal samplings. The data suggest an active role for certain enteric bacteria in the pathogenesis of NEC.

Fulminant necrotising enterocolitis associated with Clostridia

5 infants with no growth of bacteria on cultures of blood and peritoneal fluid recovered from necrotising enterocolitis after medical treatment alone. 12 infants with positive cultures required surgery. 5 of these 12, who did not harbour clostridia, had a mild clinical course and all 5 survived segmental bowel resection. The 7 infants who harboured clostridia had a more severe clinical course and 4 died. In 3 of 4 infants with Clostridium perfringens, the necrotising enterocolitis was fulminant, characterised by severe pneumatosis intestinalis, extensive gangrene, early intestinal perforation, and a fatal outcome.

Outbreak of necrotising enterocolitis caused by Clostridium butyricum

12 hospital-born babies had necrotising enterocolitis, of varying severity, within six weeks, 5 of them within ten days. The usually described predisposing causes were absent in most, though no baby was exclusively breast -fed. Evidence of the presence of Clostridium butyricum was found in the blood of 9 out of 10 babies examined. Cl. butyricum is probably a primary, not a secondary invader.

The clinical significance of pneumatosis cystoides intestinalis: a report of 5 cases

Pneumatosis cystoides intestinalis is an uncommon condition characterized by the presence of gas within the wall of the bowel. In most cases the clinical course is benign and may well be self-limiting, while in others the appearance of pneumatosis may indicate the presence of bowel ischaemia and necessitate emergency laparotomy. This paper describes 5 cases which demonstrate some of the difficulties in diagnosis and management and the improvement which can result from clinical awareness of the condition.