Gut Sphingolipid Composition as a Prelude to Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) remains a major challenge in neonatology. Little is known about NEC pathophysiology apart from the presence of pre-event gut dysbiosis. Here, we applied broad range metabolomics to stools obtained 1-5 days before NEC developed from 9 cases (9 samples) and 19 (32 samples) controls matched for gestational age at birth and birth weight. The 764 identified metabolites identified six pathways that differ between cases and controls. We pursued sphingolipid metabolism because cases had decreased ceramides and increased sphingomyelins compared to controls, and because of the relevance of sphingolipids to human inflammatory disorders. Targeted analysis of samples from 23 cases and 46 controls confirmed the initial broad range observations. While metabolites provided only 73% accuracy of classification by machine learning, hierarchical clustering defined a sphingolipid associated grouping that contained 60% of the cases but only 13% of the controls, possibly identifying a pathophysiologically distinct subset of NEC. The clustering did not associate with any of the analyzed clinical and sample variables. We conclude that there are significant changes in sphingolipid metabolism components in pre-NEC stools compared to controls, but our data urge circumspection before using sphingolipids as broadly applicable predictive biomarkers.

Relationship between enteric pathogens and acute gastroenteritis disease severity: a prospective cohort study

OBJECTIVES

To evaluate the relationship between individual bacterial and viral pathogens and disease severity.

METHODS

Children <18 years with three or more episodes of vomiting and/or diarrhoea were enrolled in two Canadian paediatric emergency departments between December 2014 and August 2016. Specimens were analysed employing molecular panels, and outcome data were collected 14 days after enrolment. The primary outcome was severe disease over the entire illness (symptom onset until 14-day follow-up), quantified employing the Modified Vesikari Scale (MVS) score. The score was additionally analysed in two other time periods: index (symptom onset until enrolment) and follow-up (enrolment until 14-day follow-up).

RESULTS

Median participant age was 20.7 (IQR: 11.3, 44.2) months; 47.4% (518/1093) and 73.4% (802/1093) of participants had index and total MVS scores ≥11, respectively. The most commonly identified pathogens were rotavirus (289/1093; 26.4%) and norovirus (258/1093; 23.6%). In multivariable analysis, severe disease over the entire illness was associated with rotavirus (OR = 9.60; 95%CI: 5.69, 16.19), Salmonella (OR = 6.61; 95%CI: 1.50, 29.17), adenovirus (OR = 2.53; 95%CI: 1.62, 3.97), and norovirus (OR = 1.43; 95%CI: 1.01, 2.01). Pathogens associated with severe disease at the index visit were: rotavirus only (OR = 6.13; 95%CI: 4.29, 8.75), Salmonella (OR = 4.59; 95%CI: 1.71, 12.29), adenovirus only (OR = 2.06; 95%CI: 1.41, 3.00), rotavirus plus adenovirus (OR = 3.15; 95%CI: 1.35, 7.37), and norovirus (OR = 0.68; 95%CI: 0.49, 0.94). During the follow-up period, rotavirus (OR = 2.21; 95%CI: 1.50, 3.25) and adenovirus (OR = 2.10; 95%CI: 1.39, 3.18) were associated with severe disease.

CONCLUSIONS

In children presenting for emergency department care with acute gastroenteritis, pathogens identified were predominantly viruses, and several of which were associated with severe disease. Salmonella was the sole bacterium independently associated with severe disease.

The ecology and pathobiology of Clostridium difficile infections: an interdisciplinary challenge

Clostridium difficile is a well recognized pathogen of humans and animals. Although C. difficile was first identified over 70 years ago, much remains unknown in regards to the primary source of human acquisition and its pathobiology. These deficits in our knowledge have been intensified by dramatic increases in both the frequency and severity of disease in humans over the last decade. The changes in C. difficile epidemiology might be due to the emergence of a hypervirulent stain of C. difficile, ageing of the population, altered risk of developing infection with newer medications, and/or increased exposure to C. difficile outside of hospitals. In recent years, there have been numerous reports documenting C. difficile contamination of various foods, and reports of similarities between strains that infect animals and strains that infect humans as well. The purposes of this review are to highlight the many challenges to diagnosing, treating, and preventing C. difficile infection in humans, and to stress that collaboration between human and veterinary researchers is needed to control this pathogen.

Associations between bovine, human, and raw milk, and beef isolates of non-O157 Shiga toxigenic Escherichia coli within a restricted geographic area of the United States

A survey for Shiga toxigenic Escherichia coli in raw milk and beef was conducted within a defined geographic region of the United States. Prevalence rates based on detection of Shiga toxin gene (stx) were 36% for retail beef, 23% for beef carcasses, and 21% for raw milk samples, which were significantly higher than were Shiga toxigenic E. coli isolation rates of 7.5, 5.8, and 3.2%, respectively. Seasonal prevalence differences were significant for stx positivity among ground beef and milk samples. Distribution of stx subtypes among isolates varied according to sample type, with stx1 predominating in milk, stx2 on carcasses, and the combination of both stx1 and stx2 in beef. Ancillary virulence markers eae and ehx were evident in 23 and 15% of isolates, respectively. Pulsed-field gel electrophoresis demonstrated associations between food isolates and sympatric bovine fecal, and human clinical isolates. These data demonstrate that non-O157 Shiga toxigenic E. coli is present in the food chain in the Pacific Northwest, and its risk to health warrants critical assessment.

Identification and characterization of a novel genomic island integrated at selC in locus of enterocyte effacement-negative, Shiga toxin-producing Escherichia coli

The selC tRNA gene is a common site for the insertion of pathogenicity islands in a variety of bacterial enteric pathogens. We demonstrate here that Escherichia coli that produces Shiga toxin 2d and does not harbor the locus of enterocyte effacement (LEE) contains, instead, a novel genomic island. In one representative strain (E. coli O91:H(-) strain 4797/97), this island is 33,014 bp long and, like LEE in E. coli O157:H7, is integrated 15 bp downstream of selC. This E. coli O91:H(-) island contains genes encoding a novel serine protease, termed EspI; an adherence-associated locus, similar to iha of E. coli O157:H7; an E. coli vitamin B12 receptor (BtuB); an AraC-type regulatory module; and four homologues of E. coli phosphotransferase proteins. The remaining sequence consists largely of complete and incomplete insertion sequences, prophage sequences, and an intact phage integrase gene that is located directly downstream of the chromosomal selC. Recombinant EspI demonstrates serine protease activity using pepsin A and human apolipoprotein A-I as substrates. We also detected Iha-reactive protein in outer membranes of a recombinant clone and 10 LEE-negative, Shiga toxin-producing E. coli (STEC) strains by immunoblot analysis. Using PCR analysis of various STEC, enteropathogenic E. coli, enterotoxigenic E. coli, enteroaggregative E. coli, uropathogenic E. coli, and enteroinvasive E. coli strains, we detected the iha homologue in 59 (62%) of 95 strains tested. In contrast, espI and btuB were present in only two (2%) and none of these strains, respectively. We conclude that the newly described island occurs exclusively in a subgroup of STEC strains that are eae negative and contain the variant stx(2d )gene.

Escherichia coli O157:H7

E. coli O157:H7 can cause potentially lethal illness in hosts of all ages. These patients often are evaluated and treated by gastroenterologists. The treating physician should administer adequate hydration, usually parenterally, and avoid the use of antibiotics and antimotility agents. The physician needs to notify immediately the appropriate public health authorities of the diagnosis and to ensure that the isolate is recovered by the microbiologist and forwarded for molecular linkage analyses.

Thrombogenic alleles, Escherichia coli O157:H7 infections, and hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) of childhood most commonly follows gastrointestinal infection with Escherichia coli O157:H7. This pathogen elaborates Shiga toxins that are believed to cause microvascular injury and to trigger a thrombogenic response. The exact mechanisms leading to variable disease manifestations are unknown. Allelic variation in genes encoding selected coagulation factors and inhibitors of fibrinolysis were examined to determine whether or not a causal relationship exists between hypercoagulability and the development of HUS. No correlation between the thrombogenic factor V (G1691A), factor II (G20210A), methylenetetrahydrofolate reductase (C677T), or the plasminogen activator inhibitor (PAI)-1 promotor (4G/5G) genotypes and the risk of infection with E. coli O157:H7, or the risk of development of HUS among infected patients, was found. Serum PAI-1 levels did not correlate with the PAI-1 genotype. We conclude that the alleles studied are not major risk factors for the acquisition of E. coli O157:H7 infection, or of E. coli O157:H7-related HUS.

von Willebrand factor and von Willebrand factor-cleaving metalloprotease activity in Escherichia coli O157:H7-associated hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) usually occurs after infection with Shiga toxin-producing bacteria. Thrombotic thrombocytopenic purpura, a disorder with similar clinical manifestations, is associated with deficient activity of a circulating metalloprotease that cleaves von Willebrand factor at the Tyr842-Met843 peptide bond in a shear stress-dependent manner. We analyzed von Willebrand factor-cleaving metalloprotease activity and the status of von Willebrand factor in 16 children who developed HUS after Escherichia coli O157:H7 infection and in 29 infected children who did not develop this complication. Von Willebrand factor-cleaving metalloprotease activity was normal in all subjects, but von Willebrand factor size was decreased in the plasma of each of 16 patients with HUS. The decrease in circulating von Willebrand factor size correlated with the severity of thrombocytopenia and was proportional to an increase in von Willebrand factor proteolytic fragments in plasma. Immunohistochemical studies of the kidneys in four additional patients who died of HUS demonstrated glomerular thrombi in three patients, and arterial and arteriolar thrombi in one patient. The glomerular thrombi contained fibrin but little or no von Willebrand factor. A decrease in large von Willebrand factor multimers, presumably caused by enhanced proteolysis from abnormal shear stress in the microcirculation, is common in HUS.

Acquisition of the rfb-gnd cluster in evolution of Escherichia coli O55 and O157

The rfb region specifies the structure of lipopolysaccharide side chains that comprise the diverse gram-negative bacterial somatic (O) antigens. The rfb locus is adjacent to gnd, which is a polymorphic gene encoding 6-phosphogluconate dehydrogenase. To determine if rfb and gnd cotransfer, we sequenced gnd in five O55 and 13 O157 strains of Escherichia coli. E. coli O157:H7 has a gnd allele (allele A) that is only 82% identical to the gnd allele (allele D) of closely related E. coli O55:H7. In contrast, gnd alleles of E. coli O55 in distant lineages are >99.9% identical to gnd allele D. Though gnd alleles B and C in E. coli O157 that are distantly related to E. coli O157:H7 are more similar to allele A than to allele D, there are nucleotide differences at 4 to 6% of their sites. Alleles B and C can be found in E. coli O157 in different lineages, but we have found allele A only in E. coli O157 belonging to the DEC5 lineage. DNA 3' to the O55 gnd allele in diverse E. coli lineages has sequences homologous to tnpA of the Salmonella enterica serovar Typhimurium IS200 element, E. coli Rhs elements (including an H-rpt gene), and portions of the O111 and O157 rfb regions. We conclude that rfb and gnd cotransferred into E. coli O55 and O157 in widely separated lineages and that recombination was responsible for recent antigenic shifts in the emergence of pathogenic E. coli O55 and O157.

Comparison of Escherichia coli O157:H7 antigen detection in stool and broth cultures to that in sorbitol-MacConkey agar stool cultures

We evaluated the Meridian IC-STAT direct fecal and broth culture antigen detection methods with samples from children infected with Escherichia coli O157:H7 and correlated the antigen detection results with the culture results. Stools of 16 children who had recently had stool cultures positive for this pathogen (population A) and 102 children with diarrhea of unknown cause (population B) were tested with the IC-STAT device (direct testing). Fecal broth cultures were also tested with this device (broth testing). The results were correlated to a standard of the combined yield from direct culture of stools on sorbitol-MacConkey (SMAC) agar and culture of broth on SMAC agar. Eleven (69%) of the population A stool specimens yielded E. coli O157:H7 when plated directly on SMAC agar. Two more specimens yielded this pathogen when the broth culture was similarly plated. Of these 13 stool specimens, 8 and 13 were positive by direct and broth testing (respective sensitivities, 62 and 100%). Compared to the sensitivity of a simultaneously performed SMAC agar culture, the sensitivity of direct testing was 73%. Three (3%) of the population B stool specimens contained E. coli O157:H7 on SMAC agar culture; one and three of these stool specimens were positive by direct and broth testing, respectively. The direct and broth IC-STAT tests were 100% specific with samples from children from population B. Direct IC-STAT testing of stools is rapid, easily performed, and specific but is insufficiently sensitive to exclude the possibility of infection with E. coli O157:H7. Performing the IC-STAT test with a broth culture increases its sensitivity. However, attempts to recover E. coli O157:H7 by culture should not be abandoned but, rather, should be increased when the IC-STAT test result is positive.

The risk of the hemolytic-uremic syndrome after antibiotic treatment of Escherichia coli O157:H7 infections

BACKGROUND

Children with gastrointestinal infections caused by Escherichia coli O157:H7 are at risk for the hemolytic-uremic syndrome. Whether antibiotics alter this risk is unknown.

METHODS

We conducted a prospective cohort study of 71 children younger than 10 years of age who had diarrhea caused by E. coli O157:H7 to assess whether antibiotic treatment in these children affects the risk of the hemolytic-uremic syndrome and to assess the influence of confounding factors on this outcome. Estimates of relative risks were adjusted for possible confounding effects with the use of logistic-regression analysis.

RESULTS

Among the 71 children, 9 (13 percent) received antibiotics and the hemolytic-uremic syndrome developed in 10 (14 percent). Five of these 10 children had received antibiotics. Factors significantly associated with the hemolytic-uremic syndrome were a higher initial white-cell count (relative risk, 1.3; 95 percent confidence interval, 1.1 to 1.5), evaluation with stool culture soon after the onset of illness (relative risk, 0.3; 95 percent confidence interval, 0.2 to 0.8), and treatment with antibiotics (relative risk, 14.3; 95 percent confidence interval, 2.9 to 70.7). The clinical and laboratory characteristics of the 9 children who received antibiotics and the 62 who did not receive antibiotics were similar. In a multivariate analysis that was adjusted for the initial white-cell count and the day of illness on which stool was obtained for culture, antibiotic administration remained a risk factor for the development of the hemolytic uremic syndrome (relative risk, 17.3; 95 percent confidence interval, 2.2 to 137).

CONCLUSIONS

Antibiotic treatment of children with E. coli O157:H7 infection increases the risk of the hemolytic-uremic syndrome.

Molecular epidemiological and phylogenetic associations of two novel putative virulence genes, iha and iroN(E. coli), among Escherichia coli isolates from patients with urosepsis

Two novel putative Escherichia coli virulence genes, iha and iroN from E. coli (iroN(E. coli)), were detected in 55 and 39%, respectively, of 67 E. coli isolates from patients with urosepsis. iha and iroN(E. coli) exhibited divergent associations with other putative virulence genes, phylogenetic markers, host characteristics, and antimicrobial resistance.

Iha: a novel Escherichia coli O157:H7 adherence-conferring molecule encoded on a recently acquired chromosomal island of conserved structure

The mechanisms used by Shiga toxin (Stx)-producing Escherichia coli to adhere to epithelial cells are incompletely understood. Two cosmids from an E. coli O157:H7 DNA library contain an adherence-conferring chromosomal gene encoding a protein similar to iron-regulated gene A (IrgA) of Vibrio cholerae (M. B. Goldberg, S. A. Boyko, J. R. Butterton, J. A. Stoebner, S. M. Payne, and S. B. Calderwood, Mol. Microbiol. 6:2407-2418, 1992). We have termed the product of this gene the IrgA homologue adhesin (Iha), which is encoded by iha. Iha is 67 kDa in E. coli O157:H7 and 78 kDa in laboratory E. coli and is structurally unlike other known adhesins. DNA adjacent to iha contains tellurite resistance loci and is conserved in structure in distantly related pathogenic E. coli, but it is absent from nontoxigenic E. coli O55:H7, sorbitol-fermenting Stx-producing E. coli O157:H-, and laboratory E. coli. We have termed this region the tellurite resistance- and adherence-conferring island. We conclude that Iha is a novel bacterial adherence-conferring protein and is contained within an E. coli chromosomal island of conserved structure. Pathogenic E. coli O157:H7 has only recently acquired this island.

Bacterial DNA in mixed cholesterol gallstones

OBJECTIVE

Numerous investigators have proposed a role for bacteria in biliary lithogenesis. We hypothesized that bacterial DNA is present in gallstones, and that categorical differences exist between gallstone type and the frequency of bacterial sequences.

METHODS

Polymerase chain reaction (PCR) was used to amplify bacterial 16S rRNA and uidA (encoding Escherichia coli [E. coli] beta-glucuronidase) genes in different types of gallstones. PCR products were sequenced.

RESULTS

Bacterial 16S rRNA and uidA DNA sequences in E. coli were detected in all brown pigment, common bile duct, and mixed cholesterol gallstones (n = 14). In contrast, only one (14%) of seven pure cholesterol gallstones yielded a PCR product. Most (88%) mixed cholesterol gallstones yielded PCR amplification products from their central, as well as their outer, portions. Sequenced products possessed 88-98% identity to 16S rRNA genes of E. coli and Pseudomonas species.

CONCLUSIONS

Bacterial DNA sequences are usually present in mixed cholesterol (to 95% cholesterol content), brown pigment, and common bile duct, but rarely in pure cholesterol gallstones. The presence of bacterial beta-glucuronidase is also suggested. The role of bacteria and their products in the formation of mixed cholesterol gallstones, which comprise the majority of cholesterol gallstones, warrants further study.

Biocontrol of Escherichia coli O157 with O157-specific bacteriophages

Escherichia coli O157 antigen-specific bacteriophages were isolated and tested to determine their ability to lyse laboratory cultures of Escherichia coli O157:H7. A total of 53 bovine or ovine fecal samples were enriched for phage, and 5 of these samples were found to contain lytic phages that grow on E. coli O157:H7. Three bacteriophages, designated KH1, KH4, and KH5, were evaluated. At 37 or 4 degrees C, a mixture of these three O157-specific phages lysed all of the E. coli O157 cultures tested and none of the non-O157 E. coli or non-E. coli cultures tested. These results required culture aeration and a high multiplicity of infection. Without aeration, complete lysis of the bacterial cells occurred only after 5 days of incubation and only at 4 degrees C. Phage infection and plaque formation were influenced by the nature of the host cell O157 lipopolysaccharide (LPS). Strains that did not express the O157 antigen or expressed a truncated LPS were not susceptible to plaque formation or lysis by phage. In addition, strains that expressed abundant mid-range-molecular-weight LPS did not support plaque formation but were lysed in liquid culture. Virulent O157 antigen-specific phages could play a role in biocontrol of E. coli O157:H7 in animals and fresh foods without compromising the viability of other normal flora or food quality.

Escherichia coli O157:H7 in retail ground beef in Seattle: results of a one-year prospective study

Escherichia coli O157:H7 was sought systematically in 1,400 samples of retail ground beef in Seattle in a 1-year prospective study. Sorbitol-nonfermenting, lactose-fermenting, indole-positive colonies isolated after enrichment culture were probed for the presence of Shiga toxin genes. Totals of 67,040 sorbitol-nonfermenting and 66,705 sorbitol-fermenting colonies were characterized, but E. coli O157:H7 was not identified. The sensitivity of this technique was usually sufficient to detect E. coli O157:H7 at a concentration below 1 CFU/g of meat. These data demonstrate that retail ground beef in Seattle is neither frequently nor heavily contaminated with E. coli O157:H7.

Non-O157:H7 pathogenic Shiga toxin-producing Escherichia coli: phenotypic and genetic profiling of virulence traits and evidence for clonality

The virulence profiles of most non-O157 Shiga toxin (Stx)-producing Escherichia coli (STEC) are unknown. STEC belonging to serogroups O26, O103, and O111 were characterized to determine clonality and to profile virulence traits. Isolates within STEC serogroups O26, O111, and O103 were >80% identical in their randomly amplified polymorphic DNA pattern, suggesting clonality in these serogroups. The serogroups were distantly related to each other and to E. coli O157:H7. stx restriction fragment length polymorphism differentiated some STEC with the same randomly amplified polymorphic DNA pattern. The hemolytic phenotype of STEC O103:H2 isolates resembled that of alpha- and not enterohemorrhagic E. coli hemolysin. Virulence gene (eae, E-hly, espP, etp, katP, stx) probing demonstrated serogroup-specific profiles. Pathogenic STEC O26, O103, and O111 belong to their own lineages and have unique profiles of virulence traits that are different from the virulence profile of E. coli O157:H7.

The immunohistological diagnosis of E. coli O157:H7 colitis: possible association with colonic ischemia

OBJECTIVE

E. coli O157:H7 may cause hemorrhagic colitis resembling ischemic colitis. Diagnosis is usually made by finding sorbitol-negative colonies on MacConkey agar that react with O157 and H7 antisera. Most ischemic colitis is idiopathic, but some may be caused by E. coli O157:H7, inasmuch as this organism can produce fibrin thrombi in colon vasculature. The objectives of this study were to determine whether E. coli O157:H7 infection can be diagnosed retrospectively from paraffin blocks of colon sections and whether an association exists between E. coli O157:H7 infection and colonic ischemia.

METHODS

Paraffin-embedded sections of normal colon (n = 2) and various colitides [ischemic (n = 11), E. coli O157:H7 (n = 2), IBD (n = 8) and pseudomembranous (n = 3)] were used. Sections were deparaffinized, rehydrated, incubated with 3% peroxide in methanol, rinsed, and incubated with peroxidase-labeled antibody isolated from goats immunized with whole E. coli O157:H7. Sections were stained with peroxidase chromagen reagent and counterstained with hematoxylin. Coarse, granular, orange-brown staining was considered positive. To determine the localization of the chromagen deposits, three cases that stained positive, including one of the culture-proved E. coli O157:H7 colitis and two of colonic ischemia, were processed for electron microscopy.

RESULTS

Both cases (100%) of E. coli O157:H7 colitis and three of 11 (27.3%) cases of ischemic colitis stained positive by light microscopy. In one culture-proved case, electron microscopy demonstrated staining of bacillary structures; in two cases of colonic ischemia, extensive deposits of chromagen material were present that were associated neither with inflammatory cells nor with bacterial forms.

CONCLUSIONS

Immunoperoxidase staining of archival sections may be used to diagnose E. coli O157:H7 infection. An etiological role for this organism is possible in some cases of colonic ischemia.

A PCR specific for Escherichia coli O157 based on the rfb locus encoding O157 lipopolysaccharide

A PCR was developed for the detection of Escherichia coli O157 based on the rfbE O-antigen synthesis genes. A 479-bp PCR product was amplified specifically from E. coli O157 in cell lysates containing 200 or 2 CFU following crude DNA extraction. The PCR detected < 1 CFU of E. coli O157 per ml in raw milk following enrichment.

Cholelithiasis following Escherichia coli O157:H7-associated hemolytic uremic syndrome

Sequelae of Escherichia coli O157:H7-associated hemolytic uremic syndrome (HUS) 2-3 years following an outbreak in Washington State have been prospectively studied to identify predictors of adverse sequelae. Logistic regression analysis was used to examine associations between findings in the acute course and long-term renal and gastrointestinal outcomes. Twenty-one percent of patients had gastrointestinal sequelae, which included cholelithiasis resulting in cholecystectomy (3/29), persistent pancreatitis (2/29), late colon stricture (1/29), and/or glucose intolerance (1/29). Logistic regression analysis found long-term gastrointestinal sequelae were higher in patients who, during HUS, had hypertension [odds ratio (OR) = 21.2, 95% confidence interval (CI) = 1.9-164.4, P = 0.01] or gastrointestinal complications (OR = 21.2, 95% CI = 1.9-164.4, P = 0.01). Renal sequelae were seen in 35% of patients. One patient (4%) had persistent hypertension and 9 (31%) had minor urinary findings (hematuria or proteinuria). Thrombocytopenia lasting longer than 10 days during the acute illness was associated with a risk for subsequent renal sequelae (OR = 15.0, 95% CI = 1.98-1,703.0, P = 0.009). We conclude a high incidence of gastrointestinal sequelae, especially cholelithiasis presenting long after the acute illness, may be seen with HUS. The short follow-up period may underestimate the extent and severity of eventual renal sequelae.

Predictors of hemolytic uremic syndrome in children during a large outbreak of Escherichia coli O157:H7 infections

OBJECTIVE

To evaluate risk factors for progression of Escherichia coli O157:H7 infection to the hemolytic uremic syndrome (HUS).

STUDY DESIGN

We conducted a retrospective cohort study among 278 Washington State children <16 years old who developed symptomatic culture-confirmed E coli O157:H7 infection during a large 1993 outbreak. The purpose of the study was to determine the relative risk (RR) of developing HUS according to demographic characteristics, symptoms, laboratory test results, and medication use in the first 3 days of illness.

RESULTS

Thirty-seven (14%) children developed HUS. In univariate analysis, no associations were observed between HUS risk and any demographic characteristic, the presence of bloody diarrhea or of fever, or medication use. In multivariate analysis, HUS risk was associated with, in the first 3 days of illness, use of antimotility agents (odds ratio [OR] = 2.9; 95% confidence interval [CI] 1.2-7.5) and, among children <5.5 years old, vomiting (OR = 4. 2; 95% CI 1.4-12.7). Among the 128 children tested, those whose white blood cell (WBC) count was >/=13 000/microL in the first 3 days of illness had a 7-fold increased risk of developing HUS (RR 7. 2; 95% CI 2.8-18.5). Thirteen (38%) of the 34 patients with a WBC count >/=13 000/microL developed HUS, but only 5 (5%) of the 94 children whose initial WBC count was <13 000/microL progressed to HUS. Among children who did not develop HUS, use of antimotility agents in the first 3 days of illness was associated with longer duration of bloody diarrhea.

CONCLUSIONS

Prospective studies are needed to further evaluate measures to prevent the progression of E coli O157:H7 infection to HUS and to assess further clinical and laboratory risk factors. These data argue against the use of antimotility agents in acute childhood diarrhea. Our finding that no intervention decreased HUS risk underscores the importance of preventing E coli O157:H7 infections.

Genetic and phenotypic analysis of Escherichia coli with enteropathogenic characteristics isolated from Seattle children

Coliform colonies from children whose stools were submitted for microbiologic analysis were studied prospectively to determine the frequency of shedding of enteropathogenic Escherichia coli (EPEC). In total, 2225 isolates from 445 patients were probed with eaeA (encoding intimin) and the EAF (EPEC adherence factor) probe, and adherence and actin-aggregating phenotypes were determined. Twenty-five patients (5.6%) shed non-O157:H7 eaeA+ EAF- E. coli. Of these 25 patients, isolates from 5 produced Shiga toxins and from 3 possessed bfpA (encoding the bundle-forming pilus) sequences. Non-O157:H7 eaeA+ E. coli from 21 (84%) of 25 patients adhered locally to and aggregated actin in HeLa cells. Four patients shed nonadherent EAF+ eaeA- E. coli. Non-O157:H7 eaeA+ and EAF- isolates belonged to diverse electrophoretic types and classical and nonclassical enteropathogenic serotypes. EPEC are relatively common in stools submitted for analysis in this North American pediatric hospital. Their etiologic role in childhood diarrhea warrants elucidation.

A longitudinal study of Escherichia coli O157 in fourteen cattle herds

Escherichia coli O157 shedding in 14 cattle herds was determined by faecal culture at intervals of approximately 1 month for up to 13 months. The overall prevalence was 1.0% (113/10832 faecal samples) and 9 of the 14 herds were detected as positive. Herds positive 2 years previously (n = 5) had a higher prevalence of positive cattle (median = 1.9%) than herds which had been negative on a previous sampling (n = 8, median = 0.2%). Weaned heifers had a higher prevalence (1.8%) than did unweaned calves (0.9%) or adults (0.4%). For all herds the highest prevalence occurred in the summer months, which resulted in most of the positive faecal samples being collected on a minority of sampling visits.

Duration of detection of fecal excretion of Escherichia coli O157:H7 in cattle

To better define the bovine reservoir of Escherichia coli O157:H7, cattle were tested monthly by bacteriologic culture for fecal excretion of E. coli. E. coli O157:H7 was isolated from feces of 56 cattle sampled an average of 6.98 times (2-12 samples). By broth enrichment culture, immunomagnetic separation, or both, 35 cattle had 1 positive sample, 12 had 2, 7 had 3, and 1 each had 4 and 5. Five cattle with > or = 2 positive samples were in a herd in which 5 pulsed-field gel electrophoretic (PFGE) types were simultaneously present; in 3 of these cattle, different PFGE types were detected in different samples. The duration of detected excretion E. coli O157:H7 by individual cattle in this study was <1 month in 35 (63%) of 56 cattle. Both serial and concurrent excretion of different E. coli O157:H7 strains by individual cattle was observed.

Role of the Escherichia coli O157:H7 O side chain in adherence and analysis of an rfb locus

Shiga-toxigenic Escherichia coli strains belonging to serotype O157 are important human pathogens, but the genetic basis of expression of the O157 antigen and the role played by the lipopolysaccharide O side chain in the adherence of this organism to epithelial cells are not understood. We performed TnphoA mutagenesis on E. coli O157:H7 strain 86-24 to identify a mutant (strain F12) deficient in O-antigen expression. Nucleotide sequence analysis demonstrated that the transposon inserted within an open reading frame with significant homology to rfbE of Vibrio cholerae O1 (U. H. Stroeher, L. E. Karageorgos, R. Morona, and P. A. Manning, Proc. Natl. Acad. Sci. USA 89:2566-2570, 1992), which is postulated to encode perosamine synthetase. This open reading frame was designated rfbE(EcO157:H7). The guanine-plus-cytosine fraction (0.35) suggests that rfbE(EcO157:H7) may have originated in a species other than E. coli. rfbE(EcO157:H7) is conserved in nontoxigenic E. coli O157 strains expressing a variety of other flagellar antigens but is not found in E. coli O55:H7 strains, which are more closely related to E. coli O157:H7. Strain F12 was significantly more adherent to HeLa cells in a quantitative adherence assay than was its E. coli O157:H7 parent, but they did not differ in other phenotypes. Restoration of the expression of the O side chain by complementation of the TnphoA mutation in strain F12 by a plasmid expressing intact rfbE(EcO157:H7) reduced the adherence of the hyperadherent strain F12. We conclude that rfbE(EcO157:H7) is necessary for the expression of the O157 antigen, that acquisition of E. coli rfb genes occurred independently in E. coli O157:H7 and unrelated O157 strains, and that the O side chain of E. coli O157:H7 lipopolysaccharide interferes with the adherence of E. coli O157:H7 to epithelial cells.

Biliary atresia, cytomegalovirus, and age at referral

OBJECTIVE

To determine the frequency with which patients with extrahepatic biliary atresia (EHBA) are infected with cytomegalovirus (CMV) and to ascertain the age at referral to a specialty center for surgical correction of EHBA.

METHODS

The charts of all patients discharged from the Children's Hospital and Medical Center between July 1, 1989 and December 31, 1993 with a new diagnosis of EHBA were reviewed to determine the frequency with which EHBA was accompanied by CMV infection. Data analyzed included age at referral and sex of patients, histopathologic evidence of CMV infection and size of bile ducts in the resected liver, and serologic (IgM) or culture diagnosis of CMV infection.

RESULTS

Twenty-three patients with EHBA were evaluated at Children's Hospital and Medical Center in the study period. Twenty-one of the patients with EHBA were appropriately evaluated for infection with CMV and infection was documented in 5 (24%) patients. The median age of referral for all patients was 61 days (range 10 to 124 days). Infected patients were referred later (82.4 +/- 28.7 days) than noninfected patients (48.8 +/- 21.8 days) (P = .01) and were more likely to be girls, bu the medians of the diameters of the bile ducts in the resected porta hepatis were similar. Viral inclusions were not identified in any of the liver specimens.

CONCLUSIONS

CMV infection is present in an unexpectedly large proportion of patients with EHBA at the time of referral. The establishment of CMV infection in infants with cholestasis should not deter the search for EHBA. Physicians should strive to reduce the age of referral of patients with EHBA to pediatric surgical centers by evaluating infants who remained jaundiced at 4 weeks of age.

Acute gastric dilatation in Duchenne muscular dystrophy: a case report and review of the literature

Duchenne muscular dystrophy (DMD) is the most common neuromuscular disorder of childhood. Its clinical characteristics that derive from skeletal muscle involvement have been well described. Less well known is that visceral smooth muscle is affected in DMD. We report a case of a 19-year-old man with DMD who presented with severe nonradiating epigastric pain. He was initially sent home from the emergency department with a diagnosis of costochondritis. Acute gastric dilation was not considered in the differential diagnosis despite supportive history, physical examination findings, and radiographs. The case illustrates the lack of familiarity by clinicians of the gastrointestinal manifestations of DMD, including gastric dilatation and intestinal pseudoobstruction. Following a case discussion, the literature relevant to acute gastric atony is reviewed.

Molecular epidemiology of a fast-food restaurant-associated outbreak of Escherichia coli O157:H7 in Washington State

We studied the molecular epidemiology of the recent fast-food restaurant chain-associated Escherichia coli O157:H7 outbreak in Washington State. Genomic DNAs prepared from strains isolated from 433 patients were probed with radiolabelled Shiga-like toxin (SLT) I and SLT II genes and bacteriophage lambda DNA and were subsequently analyzed for their restriction fragment length polymorphism (RFLP) patterns. The SLT RFLP and lambda RFLP profiles of an E. coli O157:H7 strain isolated from the incriminated beef and prototype patient were compared with those of the patient isolates for determination of the concordance between patterns. Of the 377 patients with primary and secondary cases of infection epidemiologically linked to the outbreak, isolates from 367 (97.3%) of the patients displayed SLT RFLP and lambda RFLP profiles identical to those of the outbreak strains. Isolates from 10 of the 377 (2.6%) patients possessed SLT RFLP and lambda RFLP profiles different from those of the outbreak strains, and the patients from whom those isolates were obtained were subsequently characterized as having non-outbreak-related infections. The E. coli O157:H7 strains isolated from 31 of 44 (70.4%) patients who were epidemiologically excluded from the outbreak were linked to the outbreak by RFLP typing. Our results indicate that SLT RFLP and lambda RFLP analyses are stable and sensitive methods, and when they are used in conjunction with an epidemiological investigation they could result in an earlier recognition of outbreaks and their sources, hence prompting measures to prevent the continued transmission of E. coli O157:H7.

Escherichia coli O157:H7: clinical, diagnostic, and epidemiological aspects of human infection

E. coli O157:H7 is one of many E. coli organisms that contain genes encoding one or more toxins similar in structure and function to Shiga toxin. E. coli O157:H7 is the most frequently isolated diarrheagenic type of E. coli isolated in North America today; this pathogen can cause serious, even fatal disease. Syndromes caused by E. coli O157:H7 include diarrhea, hemorrhagic colitis, and HUS. Poorly cooked ground beef has been the most frequently implicated vehicle of transmission, but additional vehicles are being identified. Treatment consists of rehydration during hemorrhagic colitis and support of the patient during the multiple systemic complications of HUS. A policy of routine screening for E. coli O157:H7 in clinical microbiology laboratories, without reliance on the physician to request that this organism be sought or the technician to notice blood in the stool, is the most effective way to find cases. Timely and accurate diagnosis can prevent secondary transmission, avert unnecessary and possibly dangerous procedures and/or therapies, and detect continuing outbreaks. SLTEC strains other than E. coli O157:H7 may cause diseases similar to or less severe than those caused by E. coli O157:H7. At present, however, screening for such pathogens in clinical laboratories is too labor-intensive to be practical. Education and legislation should promote safe food-preparation and food-handling practices. Research should be directed at reducing the carriage of E. coli O157:H7 at its bovine source, minimizing the microbial content of food and water, and averting systemic microangiopathic hemolytic anemia after infection with this pathogen.

Characteristics of antibiotic-resistant Escherichia coli O157:H7 in Washington State, 1984-1991

The resistance of Escherichia coli O157:H7 to amoxicillin/clavulanic acid, ampicillin, ceftazidime, ceftriaxone, cefuroxime, cephalothin, chloramphenicol, ciprofloxacin, gentamicin, streptomycin, sulfisoxazole, tetracycline, ticarcillin, tobramycin, and trimethoprim-sulfamethoxazole was examined, and resistant strains were characterized. All 56 isolates collected between 1984 and 1987 were susceptible to all antibiotics tested; 13 (7.4%) of 176 strains isolated between 1989 and 1991 were resistant to streptomycin, sulfisoxazole, and tetracycline. lambda-restriction fragment length polymorphism analysis suggested that the 13 resistant strains belonged to nine different clones. The emerging resistance of E. coli O157:H7 to antibiotics could portend an increased prevalence of this pathogen in food animals that receive antibiotics. Antimicrobial resistance of E. coli O157:H7 could be useful as a rapid epidemiologic marker and as a way to select this pathogen from suspected vehicles of transmission, but this resistance could also complicate therapeutic trials with sulfa-containing antibiotics.

A multistate outbreak of Escherichia coli O157:H7-associated bloody diarrhea and hemolytic uremic syndrome from hamburgers. The Washington experience

OBJECTIVE

To determine the source of and describe a large outbreak of Escherichia coli O157:H7 infections in Washington State.

DESIGN

Case-control study; environmental investigation; provider-based surveillance for E coli O157:H7 infections.

SETTING

Chain of fast-food restaurants, hospitals, physician offices, local laboratories, and local health departments.

PARTICIPANTS

Patients with diarrhea and neighborhood controls. A case was defined as diarrhea with culture-confirmed E coli O157:H7 infection or postdiarrheal hemolytic uremic syndrome (HUS) occurring from December 1, 1992, through February 28, 1993, in a Washington State resident. Controls were age- and neighborhood-matched friends of the first 16 case patients.

INTERVENTIONS

Announcement to the public; recall of implicated hamburger lots.

MAIN OUTCOME MEASURE

Abatement of outbreak due to E coli O157:H7.

RESULTS

Infection was associated with eating at a fast-food chain (chain A) in the 10 days before symptoms began. Twelve (75%) of 16 case patients but no controls had eaten at chain A (matched odds ratio undefined; lower 95% confidence interval, 3.5; P < .001). In total, 501 cases were reported, including 151 hospitalizations (31%), 45 cases of HUS (9%), and three deaths. Forty-eight patients (10%) had secondary infections. Of the remaining 453 patients (90%), 398 (86%) reported eating at a Washington chain A restaurant; 92% of them reported eating a regular hamburger. The pulsed-field gel electrophoresis pattern of the E coli O157:H7 strains isolated from all regular hamburger lots of a single production date shipped to Washington was identical to that of the strains isolated from patients. Ten (63%) of 16 regular hamburgers cooked according to chain A policy had internal temperatures below 60 degrees C. Public health action removed more than 250,000 potentially contaminated hamburgers, preventing an estimated 800 cases.

CONCLUSIONS

This E coli O157:H7 outbreak, the largest reported, resulted from errors in meat processing and cooking. Public health surveillance through state-mandated reporting of E coli O157:H7 infection as is carried out in Washington State was critical for prompt outbreak recognition and control. Measures should be developed to reduce meat contamination. Consumers and food service workers should be educated about cooking hamburger meat thoroughly.

Etiology and outcome of diarrhea after marrow transplantation: a prospective study

BACKGROUND/AIMS

Acute diarrhea after marrow transplant is usually ascribed to acute graft-vs.-host disease (GVHD) or infection, with a reported 40%-50% incidence of infection. The aim of this study was to determine the incidence of acute diarrhea after transplantation, its causes, and its outcome.

METHODS

Two hundred ninety-six patients were followed up; patients with diarrhea were studied using standard evaluation of stool plus immunoelectron microscopy; assays for astrovirus, picobirnavirus, and Norwalk virus; and gene-probe methods for toxin-producing Escherichia coli. In 38 patients with diarrhea, intestinal biopsy specimens and duodenal fluid were also analyzed.

RESULTS

One hundred fifty acute diarrheal episodes developed in 126 patients (an incidence of 43%). Intestinal infection was found in 20 of 150 episodes: viruses (astrovirus, adenovirus, cytomegalovirus, and rotavirus) in 12 patients, nosocomially acquired bacteria (Clostridium difficile and Aeromonas) in 7 patients, and mixed infection in 1 patient. Acute GVHD was responsible for 72 of 150 episodes (48%). Clinical signs and symptoms of infection and GVHD were similar. In 58 of 150 episodes (39%), no clear etiology could be found for self-limited diarrhea.

CONCLUSIONS

Intestinal infection accounted for 13% and acute GVHD for 48% of diarrheal episodes. The most common infecting organisms were astrovirus, C. difficile, and adenovirus. Most cases of diarrhea after marrow transplant are not caused by infection.

The prevalence of Escherichia coli O157.H7 in dairy and beef cattle in Washington State

Escherichia coli O157.H7 was found in 10 of 3570 (0.28%) faecal samples from dairy cattle in 5 of 60 herds (8.3%). Several tentative associations with manure handling and feeding management practices on dairy farms were identified. Faecal/urine slurry samples, bulk milk samples, and milk filters from dairy herds were negative for E. coli O157.H7. E. coli O157.H7 was also isolated from 10 of 1412 (0.71%) faecal samples from pastured beef cattle in 4 of 25 (16%) herds. The prevalence of E. coli O157.H7 excretion in feedlot beef cattle was 2 of 600 (0.33%). The identification of cattle management practices associated with colonization of cattle by E. coli O157.H7 suggests the possibility that human E. coli O157.H7 exposure may be reduced by cattle management procedures.

Escherichia coli O 157:H7-associated hemolytic-uremic syndrome after ingestion of contaminated hamburgers

We conducted a retrospective analysis of 37 children with Escherichia coli O157:H7-associated hemolytic-uremic syndrome. The infection was traced to contaminated hamburgers at a fast-food restaurant chain. Within 5 days of the first confirmed case, the Washington State Department of Health identified the source and interrupted transmission of infection. Ninety-five percent of the children initially had severe hemorrhagic colitis. Nineteen patients (51%) had significant extrarenal abnormalities, including pancreatitis, colonic necrosis, glucose intolerance, coma, stroke, seizures, myocardial dysfunction, pericardial effusions, adult respiratory disease syndrome, and pleural effusions. Three deaths occurred, each in children with severe multisystem disease. At follow-up two children have significant impairment of renal function (glomerular filtration rate < 80 ml/min/per 1.73 Hm2); both of these children have a normal serum creatinine concentration. Hemolytic-uremic syndrome is the most common cause of acute renal failure in children, and this experience emphasizes the systemic nature of this disease. Clinicians should anticipate that multisystem involvement may occur in these patients, necessitating acute intervention or chronic follow-up. This outbreak of Hemolytic-uremic syndrome also highlights the microbiologic hazards of inadequately prepared food and emphasizes the importance of public health intervention in controlling Hemolytic-uremic syndrome.

Occurrence of Shiga-like toxin-producing Escherichia coli in retail fresh seafood, beef, lamb, pork, and poultry from grocery stores in Seattle, Washington

Fresh meat, poultry, and seafood purchased from Seattle area grocery stores were investigated for the presence of Shiga-like toxin-producing Escherichia coli by using DNA probes for Shiga-like toxin (SLT) genes I and II. Of the 294 food samples tested, 17% had colonies with sequence homology to SLT I and/or SLT II genes.

Shiga-like toxin-producing Escherichia coli in Seattle children: a prospective study

BACKGROUND

The frequency with which stools contain Shiga-like toxin producing Escherichia coli not belonging to serotype O157:H7 is unknown in the United States. The aim of this study was to determine the frequency with which these E. coli are present in stools from children from Seattle submitted for bacteriologic analysis.

METHODS

2225 coliform colonies from 445 stools submitted for bacterial culture from Seattle children were probed with the structural genes of Shiga-like toxins I and II in a 1-year prospective study. The adherence and actin aggregating characteristics of these E. coli were subsequently determined.

RESULTS

Five (1.1%) patients had non-O157:H7 Shiga-like toxin producing E. coli, a rate of isolation higher than Shigella or Yersinia (0.2% each) but lower than Campylobacter (2.5%), E. coli O157:H7 (2.9%), or Salmonella (3.4%). Only one of the five patients had bloody diarrhea. None developed hemolytic uremic syndrome. All strains adhered in a localized pattern to, and induced actin aggregation in, HeLa cells, and produced a toxin that was lethal to Vero cells.

CONCLUSIONS

Non-O157:H7 Shiga-like toxin producing E. coli are present in stools submitted for bacterial culture in a North American childhood population. Their role in childhood diarrhea warrants better definition.

Molecular epidemiology of Escherichia coli O157:H7 strains by bacteriophage lambda restriction fragment length polymorphism analysis: application to a multistate foodborne outbreak and a day-care center cluster

Genomic DNAs prepared from 168 isolates of Escherichia coli O157:H7 were analyzed for restriction fragment length polymorphisms on Southern blots probed with bacteriophage lambda DNA. The isolates analyzed included strains from a recent large multistate outbreak of E. coli O157:H7 infection associated with consumption of poorly cooked beef in restaurants, a day-care center cluster, and temporally and geographically unrelated isolates. E. coli O157:H7 isolates recovered from the incriminated meat and from 61 (96.8%) of 63 patients from Washington and Nevada possessed identical lambda restriction fragment length patterns. The lambda restriction fragment length polymorphisms observed in 11 (91.7%) of 12 day-care center patients were identical, but they differed from that of the strain associated with the multistate outbreak. E. coli O157:H7 from 42 patients temporally or geographically unrelated to either cluster of infection possessed unique and different lambda restriction fragment length patterns, except for paired isolates from three separate clusters of infection. These data demonstrate that the hybridization of DNA digests of E. coli O157:H7 with radiolabelled bacteriophage lambda DNA can be a useful, stable, and discriminatory epidemiologic tool for analyzing the linkage between strains of E. coli O157:H7.

A comparison of human and bovine Escherichia coli O157:H7 isolates by toxin genotype, plasmid profile, and bacteriophage lambda-restriction fragment length polymorphism profile

Foods of bovine origin have been linked to human disease outbreaks caused by Escherichia coli O157:H7 and may be linked to the more common sporadic cases as well. In this study, E. coli O157:H7 from the bovine reservoir (22 isolates: 12 from dairy and 10 from beef breed cows) and from human patients (50 isolates from sporadic human infections) were compared using Shiga-like toxin genotypes, plasmid profiles, and DNA restriction fragment length polymorphisms identified with a bacteriophage lambda probe (lambda-RFLP). Twenty-three lambda-RFLP profiles, 4 Shiga-like toxin genotypes, and 8 plasmid profiles were identified among the isolates tested. Together the typing methods distinguished 43 strains, of which 3 were isolated from both humans (5 isolates) and cattle (6 isolates; 5 from dairy herds). These data demonstrate the value of lambda-RFLP as a means of strain identification for E. coli O157:H7.

Bacterial ileocecitis caused by Escherichia coli O157:H7

Escherichia coli O157:H7 is most commonly linked to hemorrhagic colitis and the hemolytic uremic syndrome. Diagnostic ultrasound was used to demonstrate terminal ileum abnormalities suggestive of bacterial ileocecitis, a recently described entity that resembles acute appendicitis, in a patient whose stool culture yielded E. coli O157:H7. This case extends the spectrum of disease caused by E. coli O157:H7 and expands the number of organisms that can cause bacterial ileocecitis.