Serotype, antimicrobial resistance, and adherence properties of Escherichia coli strains associated with outbreaks of diarrheal illness in children in the United States.

Since most recorded outbreaks of diarrhea in U.S. infants attributed to Escherichia coli occurred before currently available pathogenicity assays existed, we examined the characteristics of nonenterotoxigenic E. coli strains isolated from 50 outbreaks of diarrheal disease in U.S. infants between 1934 and 1987. We assayed the strains for enteropathogenic E. coli (EPEC) serotype, localized adherence (LA) and diffuse adherence to tissue cultures, the presence of EPEC adherence factor genes, Shiga-like (Vero) toxin production, and antimicrobial resistance. EPEC serotypes were identified in 28 outbreaks (56%). LA to HeLa cells was found in 23 outbreak strains and correlated 100% with the EPEC adherence factor probe. LA was observed in 21 of 28 EPEC and 2 of 22 non-EPEC strains; however, 5 of 23 strains that were LA positive for HeLa cells did not adhere to HEp-2 or HL cells. One strain was diffuse adherence positive, and none was Shiga-like toxin positive. Multiple resistance was common in EPEC (64%), LA-positive (74%), and LA-positive EPEC (76%) strains but not in others (10%). EPEC serotypes or LA was found in 60% (n = 30) of the outbreak strains. The remaining E. coli strains may represent nonpathogenic normal flora, as-yet-undefined pathogens, or pathogens that have lost virulence-associated traits during storage or subculturing.     

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.     

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.     

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.     

Detection of Intimins α, β, γ, and δ, Four Intimin Derivatives Expressed by Attaching and Effacing Microbial Pathogens

Intimins are outer membrane proteins expressed by enteric bacterial pathogens capable of inducing intestinal attachment-and-effacement lesions. A eukaryotic cell-binding domain is located within a 280-amino-acid (Int280) carboxy terminus of intimin polypeptides. Polyclonal antiserum was raised against Int280 from enteropathogenic Escherichia coli (EPEC) serotypes O127:H6 and O114:H2 (anti-Int280-H6 and anti-Int280-H2, respectively), and Western blot analysis was used to explore the immunological relationship between the intimin polypeptides expressed by different clinical EPEC and enterohemorrhagic E. coli (EHEC) isolates, a rabbit diarrheagenic E. coli strain (RDEC-1), and Citrobacter rodentium. Anti-Int280-H6 serum reacted strongly with some EPEC serotypes, whereas anti-Int280-H2 serum reacted strongly with strains belonging to different EPEC and EHEC serotypes, RDEC-1, and C. rodentium. These observations were confirmed by using purified Int280 in an enzyme-linked immunosorbent assay and by immunogold and immunofluorescence labelling of whole bacterial cells. Some bacterial strains were recognized poorly by either antiserum (e.g., EPEC O86:H34 and EHEC O157:H7). By using PCR primers designed on the basis of the intimin-encoding eae gene sequences of serotype O127:H6, O114:H2, and O86:H34 EPEC and serotype O157:H7 EHEC, we could distinguish between different eae gene derivatives. Accordingly, the different intimin types were designated α, β, δ, and γ, respectively.     

Enteropathogenic Escherichia coli in Psittaciformes

A total of 103 Escherichia coli isolates from psittaciform birds were examined for the presence of genes coding for shigatoxin 1 (Stx1), shigatoxin 2 (Stx2) and for intimin (eae), using the polymerase chain reaction (PCR). Sixty-eight E. coli strains were isolated from necropsy cases and faecal samples, the other 35 were from 205 cloacal swabs from Psittaciformes with various conditions. All isolates were tested for enterohaemorrhagic E. coli-haemolysin (HlyEHEC), some also for Stx production, but there was no geno-typic or phenotypic evidence of Stx in any of them. Seven isolates, six from birds with diarrhoea, harboured the eae gene, three of them belonging to the O110:H6 serotype, one each to serotypes O153:H10, O131:H-, O63:H6 and Osp:H6. These seven eae-positive strains were negative for shigatoxin and HlyEHEC, and the hlyEHEC gene was not detectable by PCR. However, a PCR amplifying the enteropathogenic E. coli (EPEC)-specific bundle-forming pili structural gene bfpA detected four bfpA positive strains (three of serotype O110:H6, one O131:H-) among the seven eae positive strains, which classifies them as EPEC. Our findings suggest that shigatoxin-producing E. coli are uncommon, but that EPEC should be considered as potential pathogens in psittaciform birds, which may be a source of human EPEC infections.     

HeLa cell adherence and cytotoxin production by enteropathogenic Escherichia coli isolated from infants with diarrhea in Thailand.

Enteropathogenic Escherichia coli (EPEC) strains isolated from hospitalized infants with diarrhea in Thailand were examined for HeLa cell adherence and cytotoxin production. Of 101 strains examined, 56 adhered to HeLa cells in a localized pattern (LA), 27 adhered in a diffuse pattern (DA), and 18 did not adhere. All 56 LA EPEC strains were O:K serotype O119:K69. A total of 20 (83%) of 24 EPEC O86:K61 strains and 7 (38%) of 19 EPEC strains belonging to six other O:K serotypes exhibited DA. All LA EPEC strains hybridized with a DNA probe for genes encoding EPEC adherence factor, whereas none of the 27 DA or 18 nonadherent EPEC strains hybridized with EPEC adherence factor probe. Sonic extracts of 57 (58%) of 98 EPEC strains tested at a dilution of 1:100 caused greater than 25% mortality of HeLa cell monolayers. A total of 50 (88%) of 57 cytotoxic sonic extracts were inhibited to various degrees by a 1:500 dilution of polyclonal rabbit antisera to purified Shiga toxin. The mean percent inhibition of cytotoxic sonic extracts by anti-Shiga toxin was 67% (range, 29 to 89%). Fifty percent (38 of 56) of LA EPEC strains, fifty-two percent (14 of 27) of DA EPEC strains, and fifty-three percent (8 of 15) of nonadherent EPEC strains produced Shiga-like toxins. Both adherence and low levels of cell-associated cytotoxins were identified in EPEC strains from Thailand, but there did not appear to be an association between these two factors.     

HeLa cell-adherent enteropathogenic Escherichia coli in children under 1 year of age in Thailand.

Enteropathogenic Escherichia coli (EPEC) was isolated from 11% of 148 Hmong children under 1 year old with diarrhea at a refugee camp in northern Thailand. Of 16 children with EPEC-associated diarrhea, 11 were infected with EPEC that adhered to HeLa cells in a diffuse pattern, 3 were infected with EPEC that adhered to HeLa cells in a localized adherence (LA) pattern, and 2 were infected with EPEC that were nonadherent. In Bangkok, EPEC was isolated from 6% of 64 children under 1 year old with diarrhea and 7% of 56 children of the same age without diarrhea. Of four children with diarrhea, two were infected with EPEC with an LA pattern, and two were infected with nonadherent EPEC. Of four children without diarrhea, one was infected with EPEC with an LA pattern, one was infected with EPEC that adhered in a diffuse pattern, and two were infected with nonadherent EPEC. The 21 EPEC isolates with an LA pattern hybridized with the EPEC adherence factor DNA probe. EPEC was the only enteric pathogen identified in 16 (80%) of 20 children with EPEC-associated diarrhea. EPEC was as frequently isolated from children under 1 year old as were other bacterial enteric pathogens. The problem of identifying EPEC with pools of polyvalent antisera are described, and the need to identify additional enteropathogenic determinants of EPEC is discussed.     

Polymorphisms within EspA filaments of enteropathogenic and enterohemorrhagic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) possess a filamentous type III secretion system (TTSS) employed to deliver effector proteins into host cells. EspA is a type III secreted protein which forms the filamentous extension to the TTSS and which interacts with host cells during early stages of attaching and effacing (A/E) lesion formation. By immunofluorescence, a polyclonal antibody previously raised to EspA from EPEC strain E2348/69 (O127:H6) stained approximately 12-nm-diameter EspA filaments produced by this strain but did not stain similar filaments produced by EHEC serotype O157:H7. Similarly, an antibody that we subsequently raised to EHEC strain 85-170 (O157:H7) EspA stained approximately 12-nm-diameter EspA filaments produced by strain 85-170 but did not stain E2348/69 EspA filaments. Given such heterogeneity between EPEC and EHEC EspA filaments, we examined polymorphisms of functional EspA filaments among different EPEC and EHEC serotypes. With use of the EPEC EspA antiserum, EspA filaments were observed only with EPEC serotypes O127:H6 and O55:H6, serotypes which encode an identical EspA protein. When stained with the EHEC EspA antiserum, EspA filaments were detected only on EHEC strains belonging to serotype O157:H7; the EHEC antiserum did, however, stain EspA filaments produced by the closely related EPEC serotype O55:H7 but not filaments of any other EPEC serotype tested. Such polymorphisms among functional EspA filaments of EPEC and EHEC would be expected to have important implications for the development of broad-range EspA-based vaccines.     

Prospective study of diarrheal diseases in Venezuelan children to evaluate the efficacy of rhesus rotavirus vaccine

The efficacy of a rhesus rotavirus vaccine (MMU 18006, serotype 3) against infantile diarrhea was evaluated by active home surveillance of a group of 320 children 1-10 months of age in Caracas, Venezuela. During a 1 year period following oral administration of vaccine or placebo under a double-masked code, over 600 diarrheal episodes were detected. Etiologic studies revealed that heat-stable toxin (ST) producing enterotoxigenic E. coli (ETEC) was the most common diarrheal agent detected (34%) followed by enteropathogenic E. coli (EPEC, 10.9%), heat-labile toxin (LT) producing ETEC (7.6%), rotavirus (6.9%), Cryptosporidium (4.8%) and Campylobacter (1.3%). ST-producing ETEC were also recovered from over 20% of control stool specimens obtained during diarrhea-free periods, whereas EPEC, rotavirus, Cryptosporidium, and Campylobacter were rarely detected in such control specimens. Rotavirus was responsible for about one-half of the more severe cases of diarrhea. Twenty-two of 151 infants who received placebo (14.6%) and eight of 151 receiving a 10(4) PFU dose of vaccine (5.3%) had rotavirus diarrhea during the follow-up period for an efficacy level of 64% against any rotavirus diarrhea. However, vaccine efficacy reached 90% against the more severe cases of rotavirus diarrhea and was noticeably high in the 1-4 month age group. Serotypic analysis of the rotaviruses detected suggests that the resistance induced by the vaccine was type specific since significant protection was only evident against serotype 3 rotaviruses. A 10(3) PFU dose tested initially in 18 children did not appear to protect against rotavirus diarrhea.     

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.     

Flagellin-dependent and -independent inflammatory responses following infection by enteropathogenic Escherichia coli and Citrobacter rodentium

Enteropathogenic Escherichia coli (EPEC) and the murine pathogen Citrobacter rodentium belong to the attaching and effacing (A/E) family of bacterial pathogens. These noninvasive bacteria infect intestinal enterocytes using a type 3 secretion system (T3SS), leading to diarrheal disease and intestinal inflammation. While flagellin, the secreted product of the EPEC fliC gene, causes the release of interleukin 8 (IL-8) from epithelial cells, it is unclear whether A/E bacteria also trigger epithelial inflammatory responses that are FliC independent. The aims of this study were to characterize the FliC dependence or independence of epithelial inflammatory responses to direct infection by EPEC or C. rodentium. Following infection of Caco-2 intestinal epithelial cells by wild-type and DeltafliC EPEC, a rapid activation of several proinflammatory genes, including those encoding IL-8, monocyte chemoattractant protein 1, macrophage inflammatory protein 3alpha (MIP3alpha), and beta-defensin 2, occurred in a FliC-dependent manner. These responses were accompanied by mitogen-activated protein kinase activation, as well as the Toll-like receptor 5 (TLR5)-dependent activation of NF-kappaB. At later infection time points, a subset of these proinflammatory genes (IL-8 and MIP3alpha) was also induced in cells infected with DeltafliC EPEC. The nonmotile A/E pathogen C. rodentium also triggered similar innate responses through a TLR5-independent but partially NF-kappaB-dependent mechanism. Moreover, the EPEC FliC-independent responses were increased in the absence of the locus of enterocyte effacement-encoded T3SS, suggesting that translocated bacterial effectors suppress rather than cause the FliC-independent inflammatory response. Thus, we demonstrate that infection of intestinal epithelial cells by A/E pathogens can trigger an array of proinflammatory responses from epithelial cells through both FliC-dependent and -independent pathways, expanding our understanding of the innate epithelial response to infection by these pathogens.     

Survey of Culture,GoldenGate Assay,Universal Biosensor Assay,and 16S rRNA Gene Sequencing as Alternative Methods of Bacterial Pathogen Detection

Cultivation-based assays combined with PCR or enzyme-linked immunosorbent assay (ELISA)-based methods for finding virulence factors are standard methods for detecting bacterial pathogens in stools; however, with emerging molecular technologies, new methods have become available. The aim of this study was to compare four distinct detection technologies for the identification of pathogens in stools from children under 5 years of age in The Gambia, Mali, Kenya, and Bangladesh. The children were identified, using currently accepted clinical protocols, as either controls or cases with moderate to severe diarrhea. A total of 3,610 stool samples were tested by established clinical culture techniques: 3,179 DNA samples by the Universal Biosensor assay (Ibis Biosciences, Inc.), 1,466 DNA samples by the GoldenGate assay (Illumina), and 1,006 DNA samples by sequencing of 16S rRNA genes. Each method detected different proportions of samples testing positive for each of seven enteric pathogens, enteroaggregative Escherichia coli (EAEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), Shigella spp., Campylobacter jejuni, Salmonella enterica, and Aeromonas spp. The comparisons among detection methods included the frequency of positive stool samples and kappa values for making pairwise comparisons. Overall, the standard culture methods detected Shigella spp., EPEC, ETEC, and EAEC in smaller proportions of the samples than either of the methods based on detection of the virulence genes from DNA in whole stools. The GoldenGate method revealed the greatest agreement with the other methods. The agreement among methods was higher in cases than in controls. The new molecular technologies have a high potential for highly sensitive identification of bacterial diarrheal pathogens.     

Contribution of Efa1/LifA to the adherence of enteropathogenic Escherichia coli to epithelial cells

Enteropathogenic E. coli(EPEC) is an important diarrhoeal pathogen that induces characteristic lesions on the host intestine termed attaching and effacing (A/E) lesions. In this study we have examined the contribution of a large gene, efa1, which is present in all A/E pathogens, to the adherence phenotype of EPEC. An efa- derivative of EPEC JPN15 was constructed and this mutant was significantly less adherent to epithelial cells than the parent strain. The JPN15 efa- derivative was FAS-positive, produced EspA filaments and showed comparable levels of EspA secretion to JPN15. In addition, polyclonal antibodies raised to Efa1 partially inhibited the adherence of JPN15 to cultured epithelial cells. In further work, we showed that human and rabbit hosts infected with an A/E pathogen produced antibodies to Efa1 and we observed that the truncated form of efa1 present in EHEC O157:H7 was specific to that serotype. Generally efa1 was present in its entirety in the genomes of other A/E pathogens. Overall our data suggest that Efa1 has host cell binding activity, at least in tissue culture, and that it is produced during infection. These findings suggest that Efa1 may play a direct role in the pathogenesis of infections caused by A/E pathogens.     

An in-vitro model for studying the interaction of Escherichia coli O157:H7 and other enteropathogens with bovine primary cell cultures

Sections of kidney, trachea, ileum, colon, rectum and rumen were removed at post mortem from a neonatal calf and, with the exception of the rumen, primary cell lines were established for each of the cell types. The adherence of enterohaemorrhagic Escherichia coli (EHEC) serotype O157:H7, enteropathogenic E. coli (EPEC) serotype O111, E. coli K12 (a laboratory adapted non-pathogenic strain) and Salmonella enterica serotype Typhimurium was assayed on each cell type. For all adherence assays on all cell lines, EHEC O157:H7 adhered to a significantly greater extent than the other bacteria. S. Typhimurium and EPEC O111 adhered to a similar extent to one another, whereas E. coli K12 was significantly less adherent by 100-fold. In all cell types, >10% of adherent S. Typhimurium bacteria invaded, whereas c. 0.01-0.1% of adherent EHEC O157:H7 and EPEC O111 bacteria invaded, although they are regarded as non-invasive. EHEC O157 generated actin re-arrangements in all cell types as demonstrated by fluorescent actin staining (FAS) under densely packed bacterial micro-colonies. EPEC O111 readily generated the localised adherent phenotype on bovine cells but generated only densely packed micro-colonies on HEp-2 cells. The intensity of actin re-arrangements induced in bovine cells by EPEC O111 was less than that induced by EHEC O157:H7. The intimate attachment on all cell types by both EHEC O157:H7 and EPEC O111 was clearly demonstrated by scanning electron microscopy.     

Characterization of two virulence proteins secreted by rabbit enteropathogenic Escherichia coli, EspA and EspB, whose maximal expression is sensitive to host body temperature.

Enteropathogenic Escherichia coli (EPEC) and rabbit EPEC (RDEC-1) cause unique histopathological features on intestinal mucosa, including attaching/effacing (A/E) lesions. Due to the human specificity of EPEC, RDEC-1 has been used as an animal model to study EPEC pathogenesis. At least two of the previously identified EPEC-secreted proteins, EspA and EspB, are required for triggering host epithelial signal transduction pathways, intimate adherence, and A/E lesions. However, the functions of these secreted proteins and their roles in pathogenesis have not been characterized. To investigate the function of EspA and EspB in RDEC-1, the espA and espB genes were cloned and their sequences were compared to that of EPEC O127. The EspA proteins showed high similarity (88.5% identity), while EspB was heterogeneous in internal regions (69.8% identity). However, RDEC-1 EspB was identical to that of enterohemorrhagic E. coli serotype O26. Mutations in RDEC-1 espA and espB revealed that the corresponding RDEC-1 gene products are essential for triggering of host signal transduction pathways and invasion into HeLa cells. Complementation with plasmids containing EPEC espA or/and espB genes into RDEC-1 mutant strains demonstrated that they were functionally interchangeable, although the EPEC proteins mediated higher levels of invasion. Furthermore, maximal expression of RDEC-1 and EPEC-secreted proteins occurred at their respective host body temperatures, which may contribute to the lack of EPEC infectivity in rabbits.     

Epidemiology of rotavirus serotypes in Melbourne, Australia, from 1973 to 1989.

Fecal rotavirus strains collected between 1973 and 1989 from 943 children admitted with acute diarrhea to one hospital in Melbourne, Australia, were serotyped by using an enzyme-linked immunosorbent assay. The assay incorporated neutralizing monoclonal antibodies specific for VP7 of the four major human serotypes (1 through 4). A serotype could be assigned to 690 of 943 specimens (73.2%). Typeable strains comprised serotype 1 (72.5%), serotype 2 (6.8%), serotype 3 (2.9%), or serotype 4 (15.4%). Monotypes 1a and 1c comprised 52 and 44%, respectively, of serotype 1 strains. All serotypes and monotypes exhibited polymorphic genomic RNAs. Specimens reacting as mixed serotypes were rare (3.2%) and included intertypic strains (0.7%) and mixed infections (1.0%). Nontypeable strains for which an electropherotype could be determined appeared to be identical with typeable strains present concurrently in the community. Serotypes exhibited various epidemiological patterns. Serotype 1 strains were dominant except during three successive winters when 60 to 90% of the disease was caused by serotype 2. Serotype 4 strains showed an episodic pattern of appearance, recurring at peak incidence approximately every 3 years. Fecal rotavirus strains collected from 145 newborn babies housed in Melbourne obstetric hospitals between 1974 and 1986 were also serotyped. All 135 typeable strains (93.1%) belonged to serotype 3. It is hypothesized that endemic infection with serotype 3 rotaviruses in nurseries for the newborn influenced the epidemiology of rotavirus serotypes responsible for severe clinical disease in young children in the same community.     

Escherichia coli O125ac:H6 encompasses atypical enteropathogenic E. coli strains that display the aggregative adherence pattern

O125 is an enteropathogenic Escherichia coli (EPEC) serogroup, which includes the O125ac:H6 serotype, defined as atypical EPEC. Strains of this serotype displayed the aggregative adherence (AA) pattern with HEp-2, Caco-2, T84, and HT-29 cells, possessed all the LEE region genes, and expressed intimin, Tir, and EspABD, although the attaching-effacing lesion was not detected in vitro. These results confirm that E. coli O125ac:H6 is atypical EPEC that displays the AA pattern and indicate the necessity of testing for EPEC genes combined with the determination of the adherence pattern for atypical EPEC identification.     

Escherichia coli strains of serotype O51:H40 comprise typical and atypical enteropathogenic E. coli strains and are potentially diarrheagenic

Escherichia coli strains of serotype O51:H40 were studied with regard to the presence of several virulence properties and their genetic diversity and enteropathogenicity in rabbit ileal loops. This serotype encompasses potential enteropathogenic strains mostly classified as being atypical enteropathogenic E. coli (EPEC) strains, which are genetically closer to enterohemorrhagic E. coli than to typical EPEC strains.