Epidemiology of bacterial pathogens associated with infectious diarrhea in Djibouti.

During a survey examining the causes of diarrhea in the East African country of Djibouti, 140 bacterial pathogens were recovered from 209 diarrheal and 100 control stools. The following pathogens were isolated at comparable frequencies from both diarrheal and control stools: enteroadherent Escherichia coli (EAEC) (10.6 versus 13%), enterotoxigenic E. coli (ETEC) (11 versus 10%), enteropathogenic E. coli (EPEC) (7.7 versus 12%), Salmonella spp. (2.9 versus 3%), and Campylobacter jejuni-C. coli (3.3 versus 5%). Surprisingly, the EAEC strains isolated did not correspond to well-recognized EPEC serogroups. No Yersinia spp., enteroinvasive E. coli, or enterohemorrhagic E. coli were isolated during the course of this study. Only the following two genera were recovered from diarrheal stools exclusively: Shigella spp. (7.7%) and Aeromonas hydrophila group organisms (3.3%). Shigella flexneri was the most common Shigella species isolated. Patients with Shigella species were of a higher average age than were controls (27 versus 13 years), while subjects with Campylobacter or Salmonella species belonged to younger age groups (2.6 and 1.6 years, respectively). Salmonella cases were more often in females. Shigella diarrhea was associated with fecal blood or mucus and leukocytes. ETEC was not associated with nausea or vomiting. Anorexia, weight loss, and fever were associated with the isolation of Salmonella and Aeromonas species. EAEC, ETEC, EPEC, and Shigella species were resistant to most drugs used for treating diarrhea in Africa, while the antibiotic most active against all bacteria tested was norfloxacin. We conclude that in Djibouti in 1989, Shigella and Aeromonas species must be considered as potential pathogens whenever they are isolated from diarrheal stools and that norfloxacin should be considered the drug of choice in adults for treating severe shigellosis and for diarrhea prophylaxis in travelers.     

Distribution and structural variation of the she pathogenicity island in enteric bacterial pathogens

Shigella flexneri serotype 2a carries a chromosomal pathogenicity island (PAI), termed the she PAI, that has been implicated in the pathogenesis of diarrhoeal disease. The complete nucleotide sequence and genetic organisation of the she PAI of S. flexneri 2a strain YSH6000T was determined recently. In the current study the distribution and structure of the she PAI was investigated by PCR and Southern analysis in 65 isolates of enteric pathogens including Shigella spp., enterohaemorrhagic Escherichia coli (EHEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), Yersinia enterocolitica and Salmonella enterica serovar Typhimurium. The study showed that the she PAI has undergone a variety of structural changes, defined by the presence or absence of specific marker genes in the PAI. The she PAI or structural variants of this element were found in all species of Shigella as well as in EIEC, EHEC and EPEC. No evidence of the PAI was found in Y. enterocolitica or Sal. Typhimurium. The structural form of the she PAI that exists in strain YSH6000T was present in all strains of S. flexneri serotype 2a and in some strains of S. flexneri serotypes 2b and 3c. Variants of the PAI that were missing one or more marker regions were found in all species of Shigella and in pathogenic strains of E. coli. In all strains, the PAIs have inserted into either pheV or a phe tRNA gene in another location on the chromosome. It was concluded that the she PAI is one of several closely related genetic elements that have disseminated throughout Shigella and pathogenic strains of E. coli and diverged into distinct stuctural forms.     

Bacterial aetiology of diarrhoea in young children: high prevalence of enteropathogenic Escherichia coli (EPEC) not belonging to the classical EPEC serogroups

Diarrhoeal disease continues to be one of the most common causes of admittance in Children hospital emergency. The aim of the present study was to investigate the relative contribution of enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively) as a cause of infectious bacterial diarrhoea in children from the region of Toulouse. We analysed 280 samples of stools from 280 children (<2 years) with diarrhoea admitted in the "Hopital des Enfants" from January to August 2005. Classic pathogens (Salmonella, Campylobacter, Yersinia, Shigella, Aeromonas and Vibrio) were detected by standard culture methods. Enterotoxigenic Clostridium difficile were identified after culture by immuno-enzyme assay (IEA). Virulence genes of EPEC and EHEC were detected by using PCR. Shiga-toxin production of EHEC strains was confirmed with an IEA test. Potential enteric pathogens were identified in 55 patients. EPEC was the most frequently identified agent (30 patients), followed by Campylobacter (9 cases: 7 C. jejuni and 2 C. coli) and C. difficile (8 patients), then EHEC (5 patients) and Salmonella (3 patients). No Shigella, Yersinia, Aeromonas or other pathogenic bacteria were detected during this period in that class of children. EPEC not belonging to the classical EPEC serogroups were highly prevalent (24 versus 6). EHEC possessed different genotypes and serogroups: O26 (2 strains), O157 (2 strains) and one un-typable strain. This study demonstrates the importance of EPEC (55 % of positive cases) and of EHEC (more frequent than Salmonella) in the aetiology of diarrhoeal diseases of young children. We confirm the usefulness of the PCR methodology: it allows the detection of virulent E. coli and thus increases by two fold the diagnosis of bacterial diarrhoea.     

Expression of Campylobacter jejuni invasiveness in cell cultures coinfected with other bacteria.

Enteroinvasive Salmonella, Shigella, and Escherichia coli strains were found to exert an effect which rendered Campylobacter jejuni capable of intracellular localization in epithelial cells in vitro. When monolayers of HEp-2 or A-549 cells were challenged with pure cultures of C. jejuni or Campylobacter coli, none of the eight strains tested invaded the cells. In contrast, four of these strains were able to localize intracellularly when the cells were challenged with a mixture of campylobacters and enteroinvasive Salmonella typhimurium, Shigella flexneri, Shigella boydii, Shigella sonnei, or E. coli strains. Invasiveness of campylobacters was also induced by one nonenteroinvasive strain of E. coli O124. Coinfection with other nonenteroinvasive E. coli strains did not induce invasiveness in C. jejuni. The degree of internalization induced by S. typhimurium was significantly higher than that induced by Shigella or E. coli strains. The invasive capacity of C. jejuni was found to differ considerably between strains. No evidence of an invasive potential was demonstrable for two C. coli strains or for two enterotoxigenic isolates of C. jejuni examined. C. jejuni was only able to localize intracellularly in cell cultures when the interaction occurred in a microaerobic atmosphere. None of the strains tested evoked keratoconjunctivitis in guinea pig eyes (Sereny test), regardless of the presence of coinfectants. The results indicate that a synergistic interaction that exists between C. jejuni and other enteropathogens facilitates invasion by C. jejuni.     

Role of faecal leucocytes in the diagnostic evaluation of acute diarrhoea.

The value of faecal leucocyte examination was assessed in 400 infants with acute diarrhoea and 40 normal healthy infants. Enteropathogens were isolated from 28.75%. Escherichia coli was the commonest (16.5%) followed by Salmonella typhimurium (7%), Vibrio cholerae (3.25%) and Shigella flexneri (1.5%). Exudative response was observed in 57.1% of stools with Salmonella and 66.6% each with Shigella and E.I.E.C. infections. 81.3%, 89.5% and 87.7% of stools from which EPEC and ETEC and no enteropathogens respectively were isolated showed minimal or no Leucocytic response. The test is useful to recognise probable invasive bacterial diarrhoea and to decide the cases in which stool culture could be advantageous.     

Cadmium chloride susceptibility, a characteristic of Campylobacter spp.

We report a simple diagnostic characteristic useful in the presumptive identification of Campylobacter jejuni and Campylobacter coli. Filter paper disks impregnated with cadmium chloride were placed on streaked agar medium. Zones of growth inhibition for Campylobacter spp. occurred at 1.25 micrograms per disk. Other enteropathogens (Salmonella spp., Shigella spp., Vibrio cholerae, Vibrio parahaemolyticus, Escherichia coli, and Yersinia enterocolitica) were resistant to at least 40 micrograms per disk, with the exception of a strain of Shigella flexneri, which showed first susceptibility at 10 micrograms per disk. Most of the 52 Campylobacter strains, which were isolated from human clinical and animal sources, showed zones of inhibition greater than 10 mm with 2.5 micrograms of cadmium chloride per disk. At 20 micrograms per disk, Campylobacter isolates from clinical sources were significantly (P less than 0.01) more susceptible to cadmium chloride inhibition than were those from meat samples.     

Interaction of enteropathogenic or enterohemorrhagic Escherichia coli with HeLa cells results in translocation of cortactin to the bacterial adherence site

Infection of cultured HeLa epithelial cells with enteropathogenic Escherichia coli (EPEC) or enterohemorrhagic E. coli (EHEC) O157:H7 results in accumulation of cortactin under the adherent bacteria. Tyrosine phosphorylation of cortactin is not induced following HeLa cell infection with EHEC or EPEC, contrary to what has been reported to occur with Shigella flexneri.     

Etiology of diarrhea in young children in Denmark: a case-control study

Infectious gastroenteritis is one of the most common diseases in young children. To clarify the infectious etiology of diarrhea in Danish children less than 5 years of age, we conducted a 2-year prospective case-control study. Stools from 424 children with diarrhea and 870 asymptomatic age-matched controls were examined, and their parents were interviewed concerning symptoms. Rotavirus, adenovirus, and astrovirus were detected by enzyme-linked immunosorbent assay, and norovirus and sapovirus were detected by PCR. Salmonella, thermotolerant Campylobacter, Yersinia, Shigella, and Vibrio spp. were detected by standard methods. Shiga toxin-producing (STEC), attaching-and-effacing (A/EEC), enteropathogenic (EPEC), enterotoxigenic, enteroinvasive, and enteroaggregative Escherichia coli were detected by using colony hybridization with virulence gene probes and serotyping. Parasites were detected by microscopy. Overall, a potential pathogen was found in 54% of cases. More cases than controls were infected with rotavirus, Salmonella, norovirus, adenovirus, Campylobacter, sapovirus, STEC, classical EPEC, Yersinia, and Cryptosporidium strains, whereas A/EEC, although common, was not associated with illness. The single most important cause of diarrhea was rotavirus, which points toward the need for a childhood vaccine for this pathogen, but norovirus, adenovirus, and sapovirus were also major etiologies. Salmonella sp. was the most common bacterial pathogen, followed by Campylobacter, STEC, Yersinia, and classical EPEC strains. A/EEC not belonging to the classical EPEC serotypes was not associated with diarrhea, underscoring the importance of serotyping for the definition of EPEC.     

A novel serotype of enteropathogenic Escherichia coli (EPEC) as a major pathogen in an outbreak of infantile diarrhoea

An outbreak of infantile diarrhoea was investigated in 32 children, all <2 years old, in the tropical north of Australia. Rotavirus (63%) and enteropathogenic Escherichia coli (EPEC) (59%) were the most common pathogens identified. Of the 19 EPEC isolates, 14 (74%) were of serotype O126:H12, hitherto unreported as an EPEC serotype. Other pathogens isolated included Salmonella spp. (16%), Campylobacter spp. (3%), Giardia (3%) and Shigella spp. (3%). EPEC-related gastro-enteritis is an uncommon but recognised cause of diarrhoeal outbreaks in Australia and clinicians need to be aware of the possibility of this serotype being implicated. This report highlights the disadvantages of relying on serotyping alone for the recognition of EPEC.     

Development and testing of invasion-associated DNA probes for detection of Shigella spp. and enteroinvasive Escherichia coli.

Genetic determinants of the invasive phenotype of Shigella spp. and enteroinvasive Escherichia coli (EIEC), two common agents of bacillary dysentery, are encoded on large (180- to 210 kilobase), nonconjugative plasmids. Several plasmid-encoded antigens have been implicated as important bacterial ligands that mediate the attachment and invasion of colonic epithelial cells by the bacteria. Selected invasion plasmid antigen (ipa) genes have recently been cloned from Shigella flexneri serotype 5 into the lambda gt11 expression vector. Portions of three ipa genes (ipaB, ipaC, and ipaD) were tested as DNA probes for diagnostic detection of bacillary dysentery. Under stringent DNA hybridization conditions, all three DNA sequences hybridized to a single 4.6-kilobase HindIII fragment of the invasion plasmids of representative virulent Shigella spp. and EIEC strains. No hybridization was detected in isogenic, noninvasive Shigella mutants which had lost the invasion plasmid or had deleted the ipa gene region. Furthermore, these probes did not react with over 300 other enteric and nonenteric gram-negative bacteria tested, including Salmonella, Yersinia, Edwardsiella, Campylobacter, Vibrio, Klebsiella, Aeromonas, Enterobacter, Rickettsia, and Citrobacter spp. and various pathogenic E. coli strains. The use of unique invasion-essential gene segments as probes for the specific detection of invasive dysentery organisms should benefit both epidemiologic and diagnostic analyses of Shigella spp. and EIEC.     

EspG, a novel type III system-secreted protein from enteropathogenic Escherichia coli with similarities to VirA of Shigella flexneri

The function of the rorf2 gene located on the locus of enterocyte effacement (LEE) pathogenicity island of enteropathogenic Escherichia coli (EPEC) has not been described. We report that rorf2 encodes a novel protein, named EspG, which is secreted by the type III secretory system and which is translocated into host epithelial cells. EspG is homologous with Shigella flexneri protein VirA, and the cloned espG (rorf2) gene can rescue invasion in a Shigella virA mutant, indicating that these proteins are functionally equivalent in Shigella. An EPEC espG mutant had no apparent defects in in vitro assays of virulence phenotypes, but a rabbit diarrheagenic E. coli strain carrying a mutant espG showed diminished intestinal colonization and yet diarrheal attack rates similar to those of the wild type. A second EspG homolog, Orf3, is encoded on the EspC pathogenicity islet. The cloned orf3 gene could also rescue invasion in a Shigella virA mutant, but an EPEC espG orf3 double mutant was not diminished in any tested in vitro assays for EPEC virulence factors. Our results indicate that EspG plays an accessory but as yet undefined role in EPEC virulence that may involve intestinal colonization.     

Curli loci of Shigella spp

An unstable chromosomal element encoding multiple antibiotic resistance in Shigella flexneri serotype 2a was found to include sequences homologous to the csg genes encoding curli in Escherichia coli and Salmonella enterica serovar Typhimurium. As curli have been implicated in the virulence of serovar Typhimurium, we investigated the csg loci in all four species of Shigella. DNA sequencing and PCR analysis showed that the csg loci of a wide range of Shigella strains, of diverse serotypes and different geographical distributions, were almost universally disrupted by deletions or insertions, indicating the existence of a strong selective pressure against the expression of curli. Strains of enteroinvasive E. coli (EIEC), which share virulence traits with Shigella spp. and cause similar diseases in humans, also possessed insertions or deletions in the csg locus or were otherwise unable to produce curli. Since the production of curli is a widespread trait in environmental isolates of E. coli, our results suggest that genetic lesions that abolish curli production in the closely related genus Shigella and in EIEC are pathoadaptive mutations.     

Probiotic activities of Lactobacillus casei rhamnosus: in vitro adherence to intestinal cells and antimicrobial properties

The interest of probiotics as remedies for a broad number of gastrointestinal and other infectious diseases has gained wide interest over the last few years, but little is known about their underlying mechanism of action. In this study, the probiotic activities of a human isolate of Lactobacillus casei subsp. rhamnosus strain (Lcr35) were investigated. Using intestinal Caco-2 cell line in an in vitro model, we demonstrated that this strain exhibited adhesive properties. The inhibitory effects of Lcr35 organisms on the adherence of three pathogens, enteropathogenic Escherichia coli (EPEC), enterotoxigenic E. coli (ETEC) and Klebsiella pneumoniae, were determined. A decrease in the number of adhering pathogens was observed, using either preincubation, postincubation or coincubation of the pathogens with Lcr35. Moreover, the antibacterial activities of cell-free Lcr35 supernatant was examined against nine human pathogenic bacteria, ETEC, EPEC, K. pneumoniae, Shigella flexneri, Salmonella typhimurium, Enterobacter cloacae, Pseudomonas aeruginosa, Enterococcus faecalis and Clostridium difficile. The growth of all strains was inhibited, as measured by determining the number of viable bacteria over time, but no bactericidal activity was detected in this in vitro assay. Together, these findings suggest that this probiotic strain could be used to prevent colonization of the gastrointestinal tract by a large variety of pathogens.     

Properties of equine anti-lipopolysaccharide hyperimmune plasma: binding to lipopolysaccharide and bactericidal activity against gram-negative bacteria

Anti-lipopolysaccharide equine hyperimmune plasma (anti-LPS), which has been used successfully to treat LPS (endotoxin)-mediated disorders, has been further characterised. IgG present in anti-LPS had the highest affinity for LPS prepared from Salmonella typhimurium, S. typhi, S. abortus equi and Shigella flexneri and intermediate affinity for Escherichia coli O55:B5, E. coli O127:B8 and S. enteritidis. Anti-LPS destroyed by means of complement activation a wide range of gram-negative bacteria, including various species and strains of Klebsiella, Enterobacter, E. coli, Sh. flexneri, Providencia, Salmonella and Pseudomonas. Control plasmas or saline had little or no effect. Maximum killing occurred within seconds to minutes. Electronmicroscopy showed that anti-LPS treatment of K. pneumoniae caused extensive cell wall and cytoplastic membrane disruption, followed by the appearance of spheroplasts and cell ghosts. Antibodies were required in 100,000-fold excess to inhibit the limulus amoebocyte lysate reaction with LPS from E. coli. Anti-LPS thus contains IgG that binds to a wide range of LPS, and can destroy a wide range of gram-negative bacteria by means of complement activation.     

Evolutionary relationships among pathogenic and nonpathogenic Escherichia coli strains inferred from multilocus enzyme electrophoresis and mdh sequence studies.

Within the species Escherichia coli, there are commensal strains and a variety of pathogenic strains, including enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), and urinary tract infection (UTI) strains. The pathogenic strains are identified by serotype and by possession of specific virulence determinants (toxins and adhesions, etc.) encoded by either monocistronic genes, plasmids, or pathogenicity islands. Although there are studies on the relationships between selected pathogenic strains, the relatedness among the majority of the pathogenic forms to each other, to commensal E. coli, and to the genus Shigella (which has often been suggested to be part of E. coli) has not been determined. We used multilocus enzyme electrophoresis (MLEE) at 10 enzyme loci and the sequence of the mdh housekeeping gene to study the genetic relationships of pathogenic E. coli strains (including Shigella clones), namely, 5 EPEC strains (serotypes O111 and O55), 3 EHEC strains (serotype O157), 6 ETEC strains (serotypes O78, O159, and O148), 5 EIEC strains (serotypes O124, O28, and O112), and 13 Shigella strains representing clones Flexneri, Dysenteriae, Boydii, and Sonnei, to commensal E. coli strains. Both the MLEE and mdh sequence trees reveal that EPEC, EHEC, ETEC, EIEC, and UTI strains are distributed among the ECOR set groups, with no overall clustering of EPEC, ETEC, EIEC, or UTI strains. The genus Shigella is shown to comprise a group of closely related pathogenic E. coli strains. Six pathogenic strains, i.e., M502 (EIEC; O112ac:NM), M503 (EPEC; O111:H12), M526 (ETEC; O159:H4), M522 (EPEC; O111ac:H12), M524 (ETEC; O78:H11), and M506 (ETEC; O78:H11), were found to have mdh sequences identical to those of five ECOR group A strains (ECOR5, ECOR10, ECOR14, ECOR6, and K-12). All 11 strains are closely related by MLEE. The results indicate that pathogenic strains of E. coli do not have a single evolutionary origin within E. coli but have arisen many times. The results also suggest the possibility that any E. coli strain acquiring the appropriate virulence factors may give rise to a pathogenic form.     

Interaction Between Escherichia coli and Shigella flexneri in the Digestive Tract of “Gnotobiotic” Mice

When a strain of Shigella flexneri and then a strain of Escherichia coli were implanted at an interval of 1 day in the digestive tract of germfree mice, the S. flexneri was eliminated in 8 days. However, when S. flexneri was mono-associated with germfree mice in the absence of E. coli, a population of S. flexneri appeared which was resistant to the antagonistic effects of E. coli in vivo. The emergence of this population appeared to be a stepwise process, extending over a period of 3 months. The interaction between S. flexneri and E. coli in vivo and in vitro was significantly different in that the Shigella capable of coexisting with E. coli in the digestive tract was suppressed by that organism in vitro.     

Characterization of monoclonal antibodies against Shiga-like toxin from Escherichia coli

Three monoclonal antibodies, designated MAb 16E6, MAb 13C4, and MAb 19G8, were produced which recognize Shiga-like toxin (SLT) from Escherichia coli. All three monoclonal antibodies neutralized the cytotoxicity of E. coli SLT and were able to immunoprecipitate intact labeled toxin with Staphylococcus aureus protein A. The three antibodies were of the G1 heavy and kappa light chain classes. MAb 16E6 bound to the B subunit of SLT in Western blots and also neutralized the lethality of the toxin for mice and the enterotoxicity of the toxin in ligate rabbit ileal loops. The ability of MAb 16E6 to neutralize the cytotoxicity, lethality, and enterotoxicity of E. coli confirms the hypothesis that all three activities are associated with a single toxin. MAb 16E6 and MAb 13C4 also neutralized the cytotoxicity of purified Shiga toxin from Shigella dysenteriae type 1 and Shiga-like toxic activities in crude cell extracts from Shigella flexneri, Vibrio cholerae, Vibrio parahaemolyticus, and Salmonella typhimurium. Thus, Shiga toxin and the SLTs from E. coli, Shigella flexneri, V. cholerae, V. parahaemolyticus, and Salmonella typhimurium share a common B subunit epitope that is involved in neutralization. MAb 13C4 has been successfully used in a colony blot assay for the detection of bacterial colonies which produce high levels of SLT. Sixty-two different strains of bacteria were tested by both the cytotoxicity and colony blot assays for the presence of SLT. The colony blot assay detected all strains of bacteria which produce greater than or equal to 10(5) 50% cytotoxic doses of SLT per ml of sonic lysate. There were no false-positive results among the 62 samples tested.     

Possible role of enteric organisms in the pathogenesis of ankylosing spondylitis and other seronegative arthropathies.

One-hundred eighty-five clinical isolates of Salmonella sp., Shigella sp., Escherichia coli, and Campylobacter sp. were tested for their ability to absorb the lymphocytotoxic activity of an antiserum (anti-Klebsiella sp. K43) directed against a specific HLA-B27-associated cell surface determinant on the lymphocytes of patients with ankylosing spondylitis (AS). Seven of these isolates (three Salmonella sp., two Shigella sp., one E. coli, and one Campylobacter sp.) were found to cross-react with the B27-positive cells of AS patients (B27+ AS+); an E. coli organism isolated from the rectal swab of an HLA-B27-negative clinically normal individual also cross-reacted with B27+ AS+ cells. These cross-reactive enteric organisms elaborate a factor (modifying factor) which specifically modifies the B27-positive lymphocytes of normal individuals; this factor is structurally and antigenically related to a functionally similar factor secreted by certain isolates of Klebsiella sp. These data suggest that certain enteric organisms share a common determinant which cross-reacts with B27+ AS+ cells. It is suggested that this cross-reactivity is somehow related to an early event in the pathogenesis of AS and possibly of other seronegative arthropathies.     

Evaluation of multiplex PCRs for diagnosis of infection with diarrheagenic Escherichia coli and Shigella spp

We have developed two multiplex PCR assays that detect typical and atypical enteropathogenic Escherichia coli (EPEC) isolates, enteroaggregative E. coli (EAEC) isolates, enterotoxigenic E. coli (ETEC) isolates, enteroinvasive E. coli (EIEC) isolates, Shiga toxin-producing E. coli (STEC) isolates, and Shigella spp. The targets selected for each group were eae and bfpA for EPEC isolates, the target of probe CVD432 for EAEC isolates, the genes encoding heat-labile and heat-stable toxins for ETEC isolates, stx(1) and stx(2) for STEC isolates, and ipaH for EIEC isolates and Shigella spp. These PCRs were specific and sensitive for rapid detection of target isolates in stools. Among 150 stool specimens from the acute diarrhea tested, 9 samples (6%) had atypical EPEC, 9 (6%) had typical EPEC, 7 (4.7%) had EAEC, 3 (2%) had EIEC, 3 (2%) had Shigella spp., and 1 (0.7%) had an O26 STEC strain; we also detected mixed infections, 2 (1.3%) with EAEC and Shigella spp., 1 (0.7%) with atypical and typical EPEC strains, and another with atypical EPEC and EAEC strains. One of the multiplex PCRs directly applied to 36 stool specimens correctly identified 100% of EPEC and EAEC isolates.     

Evaluation of an immunoassay for direct detection of Escherichia coli O157 in stool specimens.

An enzyme-linked immunosorbent assay (ELISA) produced by LMD Laboratories, Inc., Carlsbad, Calif., was compared with culture for the detection of Escherichia coli O157. Nine of 185 stool specimens evaluated had positive results by the LMD E. coli O157 ELISA and grew E. coli O157 on culture; 174 had negative by LMD E. coli O157 ELISA results and did not grow E. coli O157 on culture. Of 174 specimens negative by LMD E. coli O157 ELISA, 117 specimens grew other enteric pathogens: Campylobacter spp. (46 isolates), Salmonella spp. (43 isolates), Yersinia spp. (20 isolates), and Shigella spp. (8 isolates). There were two indeterminant results by the LMD E. coli O157 ELISA. One stool specimen did not grow other enteric pathogens on culture, and one grew a Campylobacter sp. on culture. Both had negative LMD E. coli O157 ELISA results upon repeat testing. The LMD E. coli O157 ELISA is an accurate, easy-to-read screening method for the detection of E. coli O157 in fecal specimens.