Enteropathogenic and enteroaggregative E. coli in stools of children with acute gastroenteritis in Davidson County, Tennessee

Whole-genome sequencing of Escherichia coli from retail meat in China reveals the dissemination of clinically important antimicrobial resistance genes

Escherichia coli is one of the important reservoirs of antimicrobial resistance genes (ARG), which often causes food-borne diseases and clinical infections. Contamination with E. coli carrying clinically important antimicrobial resistance genes in retail meat products can be transmitted to humans through the food chain, posing a serious threat to public health. In this study, a total of 330 E. coli strains were isolated from 464 fresh meat samples from 17 food markets in China, two of which were identified as enterotoxigenic and enteropathogenic E. coli. Whole genome sequencing revealed the presence of 146 different sequence types (STs) including 20 new STs, and 315 different clones based on the phylogenetic analysis, indicating the high genetic diversity of E. coli from retail meat products. Antimicrobial resistance profiles showed that 82.42 % E. coli were multidrug-resistant strains. A total of 89 antimicrobial resistance genes were detected and 12 E. coli strains carried clinically important antimicrobial resistance genes blaNDM-1, blaNDM-5, mcr-1, mcr-10 and tet(X4), respectively. Nanopore sequencing revealed that these resistance genes are located on different plasmids with the ability of horizontal transfer, and their genetic structure and environment are closely related to plasmids isolated from humans. Importantly, we reported for the first time the presence of plasmid-mediated mcr-10 in E. coli from retail meat. This study revealed the high genetic diversity of food-borne E. coli in retail meat and emphasized their risk of spreading clinically important antimicrobial resistance genes.

Pathogenic Escherichia coli, Salmonella spp. and Campylobacter spp. in Two Natural Conservation Centers of Wildlife in Portugal: Genotypic and Phenotypic Characterization

Human-wildlife coexistence may increase the potential risk of direct transmission of emergent or re-emergent zoonotic pathogens to humans. Intending to assess the occurrence of three important foodborne pathogens in wild animals of two wildlife conservation centers in Portugal, we investigated 132 fecal samples for the presence of Escherichia coli (Shiga toxin-producing E. coli (STEC) and non-STEC), Salmonella spp. and Campylobacter spp. A genotypic search for genes having virulence and antimicrobial resistance (AMR) was performed by means of PCR and Whole-Genome Sequencing (WGS) and phenotypic (serotyping and AMR profiles) characterization. Overall, 62 samples tested positive for at least one of these species: 27.3% for STEC, 11.4% for non-STEC, 3.0% for Salmonella spp. and 6.8% for Campylobacter spp. AMR was detected in four E. coli isolates and the only Campylobacter coli isolated in this study. WGS analysis revealed that 57.7% (30/52) of pathogenic E. coli integrated genetic clusters of highly closely related isolates (often involving different animal species), supporting the circulation and transmission of different pathogenic E. coli strains in the studied areas. These results support the idea that the health of humans, animals and ecosystems are interconnected, reinforcing the importance of a One Health approach to better monitor and control public health threats.

Identification of a hybrid atypical enteropathogenic and enteroaggregative Escherichia coli (aEPEC/EAEC) clone of serotype O3:H2 associated with a diarrheal outbreak in Brazil

Enteropathogenic (EPEC) and enteroaggregative (EAEC) Escherichia coli are two of the major pathotypes of diarrheagenic E. coli causing disease worldwide. Here, we report a diarrheal outbreak caused by E. coli of serotype O3:H2, harboring virulence markers from EPEC (eae) and/or EAEC (aggR). This is likely the first E. coli diarrheal outbreak caused by a hybrid atypical-EPEC/EAEC clone reported in Brazil.

Prevalence of β-Lactam Drug-Resistance Genes in Escherichia coli Contaminating Ready-to-Eat Lettuce

Thirty-four Escherichia coli isolates from 91 ready-to-eat lettuce packages, obtained from local supermarkets in Northern California, were genotyped by multilocus sequence typing, tested for susceptibility to antimicrobial agents, and screened for β-lactamase genes. We found 15 distinct sequence types (STs). Six of these genotypes (ST1198, ST2625, ST2432, ST2819, ST4600, and ST5143) have been reported as pathogens found in human samples. Twenty-six (76%) E. coli isolates were resistant to ampicillin, 17 (50%) to ampicillin/sulbactam, 8 (23%) to cefoxitin, and 7 (20%) to cefuroxime. blaCTX-M was the most prevalent β-lactamase gene, identified in eight (23%) isolates. We identified a class A broad-spectrum β-lactamase SED-1 gene, blaSED, reported by others in Citrobacter sedlakii isolated from bile of a patient. This study found that fresh lettuce carries β-lactam drug-resistant E. coli, which might serve as a reservoir for drug-resistance genes that could potentially be transmitted to pathogens that cause human infections.

Prevalence, phylogeny, and antimicrobial resistance of Escherichia coli pathotypes isolated from children less than 5 years old with community acquired- diarrhea in Upper Egypt

Background

Diarrhoea, affecting children in developing countries, is mainly caused by diarrheagenic Escherichia coli (DEC). This study principally aimed to determine the prevalence of DEC pathotypes and Extended-spectrum β-lactamase (ESBL) genes isolated from children under 5 years old with diarrhea.

Methods

A total of 320 diarrhoea stool samples were investigated. E. coli isolates were investigated for genes specific for enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC) and enterohemorrhagic E. coli (EHEC) using polymerase chain reaction (PCR). Furthermore, antimicrobial susceptibility testing, detection of antibiotic resistance-genes and phylogenetic typing were performed.

Results

Over all, DEC were isolated from 66/320 (20.6%) of the children with diarrhoea. EAEC was the predominant (47%), followed by typical EPEC (28.8%) and atypical EPEC (16.6%). Co-infection by EPEC and EAEC was detected in (7.6%) of isolates. However, ETEC, EIEC and EHEC were not detected. Phylogroup A (47%) and B2 (43.9%) were the predominant types. Multidrug-resistance (MDR) was found in 55% of DEC isolates. Extended-spectrum β-lactamase (ESBL) genes were detected in 24 isolates (24 blaTEM and 15 blaCTX-M-15). Only one isolate harbored AmpC β-lactamase gene (DHA gene).

Conclusion

The study concluded that, EAEC and EPEC are important causative agents of diarrhoea in children under 5 years. MDR among DEC has the potential to be a big concern.

Myoviridae phage PDX kills enteroaggregative Escherichia coli without human microbiome dysbiosis

Introduction. Bacteriophage therapy can be developed to target emerging diarrhoeal pathogens, but doing so in the absence of microbiome disruption, which occurs with antibiotic treatment, has not been established.Aim. Identify a therapeutic bacteriophage that kills diarrhoeagenic enteroaggregative Escherichia coli (EAEC) while leaving the human microbiome intact.Methodology. Phages from wastewater in Portland, OR, USA were screened for bacteriolytic activity by overlay assay. One isolated phage, PDX, was classified by electron microscopy and genome sequencing. A mouse model of infection determined whether the phage was therapeutic against EAEC. 16S metagenomic analysis of anaerobic cultures determined whether a normal human microbiome was altered by treatment.Results. Escherichia virus PDX, a member of the strictly lytic family Myoviridae, killed a case-associated EAEC isolate from a child in rural Tennessee in a dose-dependent manner, and killed EAEC isolates from Columbian children. A single dose of PDX (multiplicity of infection: 100) 1 day post-infection reduced EAEC recovered from mouse faeces. PDX also killed EAEC when cultured anaerobically in the presence of human faecal bacteria. While the addition of EAEC reduced the β-diversity of the human microbiota, that of the cultures with either faeces alone, faeces with EAEC and PDX, or with just PDX phage was not different statistically.Conclusion. PDX killed EAEC isolate EN1E-0007 in vivo and in vitro, while not altering the diversity of normal human microbiota in anaerobic culture, and thus could be part of an effective therapy for children in developing countries and those suffering from EAEC-mediated traveller's diarrhoea without causing dysbiosis.

Escherichia coli ST302: Genomic Analysis of Virulence Potential and Antimicrobial Resistance Mediated by Mobile Genetic Elements

aEPEC are associated with persistent diarrhea, and diarrheal outbreaks in both humans and animals worldwide. They are differentiated from typical EPEC by the lack of bundle-forming pili, and from EHEC by the lack of phage-mediated stx toxins. However, phylogenetic analyses often associate aEPEC with EHEC, promoting the hypothesis that aEPEC are the progenitors of EHEC, which is supported by aEPEC conversion to EHEC by stx-carrying phages. While aEPEC can cause disease outright, the potential to acquire stx, one of the most potent bacterial toxins known, merits close monitoring. Escherichia coli ST302 (O108:H9, O182:H9, O45:H9) are aEPEC that have been isolated from diarrheic human, pig and rabbit hosts, as well as in healthy pigs, however, no study to date has focused on E. coli ST302 strains. Through WGS and hybrid assembly we present the first closed chromosome, and two circularized plasmids of an ST302 strain - F2_18C, isolated from a healthy pig in Australia. A phylogenetic analysis placed E. coli ST302 strains in proximity to EHEC ST32 (O145:H28) strains. Public databases were interrogated for WGSs of E. coli ST302 strains and short-read gene screens were used to compare their virulence-associated gene (VAG) and antimicrobial resistance gene (ARG) cargo. E. coli ST302 strains carry diverse VAGs, including those that typically associated with extraintestinal pathogenic E. coli (ExPEC). Plasmid comparisons showed that pF2_18C_FIB shared homology with EHEC virulence plasmids such as pO103 while pF2_18C_HI2 is a large multidrug resistance IncHI2:ST3 plasmid. A comparison of 33 HI2:ST3 plasmids demonstrated that those of Australian origin have not acquired resistances to extended-spectrum beta-lactams, colistin, fosfomycin or rifampicin, unlike those originating from Asia. F2_18C was shown to carry two additional pathogenicity islands – ETT2, and the STEC-associated PAI_CL3, plasmid-associated heavy metal resistance genes, as well as several unoccupied stx-phage attachment sites. This study sheds light on the virulence and AMR potential of E. coli ST302 strains and informs AMR genomic surveillance.

The Type III Secretion System (T3SS)-Translocon of Atypical Enteropathogenic Escherichia coli (aEPEC) Can Mediate Adherence

The intimin protein is the major adhesin involved in the intimate adherence of atypical enteropathogenic Escherichia coli (aEPEC) strains to epithelial cells, but little is known about the structures involved in their early colonization process. A previous study demonstrated that the type III secretion system (T3SS) plays an additional role in the adherence of an Escherichia albertii strain. Therefore, we assumed that the T3SS could be related to the adherence efficiency of aEPEC during the first stages of contact with epithelial cells. To test this hypothesis, we examined the adherence of seven aEPEC strains and their eae (intimin) isogenic mutants in the standard HeLa adherence assay and observed that all wild-type strains were adherent while five isogenic eae mutants were not. The two eae mutant strains that remained adherent were then used to generate the eae/escN double mutants (encoding intimin and the T3SS ATPase, respectively) and after the adherence assay, we observed that one strain lost its adherence capacity. This suggested a role for the T3SS in the initial adherence steps of this strain. In addition, we demonstrated that this strain expressed the T3SS at significantly higher levels when compared to the other wild-type strains and that it produced longer translocon-filaments. Our findings reveal that the T3SS-translocon can play an additional role as an adhesin at the beginning of the colonization process of aEPEC.

Curative effects of Distemonanthus benthamianus Baillon. Trunk-bark extracts on enteropathogenic Escherichia coli 31-induced diarrhea in rats

Background Distemonanthus benthamianus is used in the Western part of Cameroon to treat diarrheal episodes and infections. This study assessed its trunk-bark extracts activity against enteropathogenic Escherichia coli 31 (EPEC 31)-induced diarrhea in rats. Methods Aqueous and methanolic extracts were analyzed through high-performance liquid chromatography (HPLC). In vitro minimum inhibitory and bactericidal concentrations (MICs/MBCs) were evaluated on Enterococcus faecalis (ATCC 10,541), E. coli (ATCC 6539), Klebsiella pneumoniae (ATCC 13,883), Salmonella typhi (ATCC 6539) strains and on Proteus mirabilis, Pseudomonas aeruginosa (PA 01) and Shigella flexneri isolates using the microdilution method. Diarrhea was induced by inoculating rats with EPEC 31 (1.5 × 108 CFU/mL; p.o). Serum transaminases level assay and enzyme-linked immunosorbent assay (ELISA) for cytokines determination were performed. Hematoxylin-eosin (H-E) staining was used for intestinal tissue analysis. Results HPLC fingerprints of extracts showed presence of gallic acid and other unidentified compounds. The lowest MIC of 256 µg/mL was obtained with methanolic extract. At 100 mg/kg, both extracts significantly (p<0.001) inhibited diarrhea, with the methanolic extract being the most active. In addition, the methanolic extract significantly (p<0.001) increased the relative mass of the liver compared to negative control (Tween-DMSO 8%). The aqueous extract (100 mg/kg) significantly (p<0.01) increased alanine aminotransferase (ALT) serum concentration; while the methanolic extract (100 mg/kg) exhibited similar effect over aspartate aminotransferase (AST). At 50 and 100 mg/kg, the methanolic extract significantly (p<0.05 and p<0.01) decreased the Interleukin-1β (IL-1β) serum level, compared to negative control (Tween-DMSO 8%). Serum level of tumor necrosis factor alpha (TNF-α) significantly (p<0.001) decreased with 100 mg/kg of aqueous extract and all doses of methanolic extract. Inhibition of inflammatory cells tissue infiltration and epithelial regeneration was highly noticed in the ileum and colon of extracts-treated rats than in ciprofloxacin-treated animals. Conclusion These findings suggest that D. benthamianus trunk-bark extracts displayed therapeutic effects against infectious diarrhea in rats.

Prevalence and Characterization of Atypical Enteropathogenic Escherichia coli Isolated from Retail Foods in China

Atypical enteropathogenic Escherichia coli (aEPEC) is an emerging pathogen that has been implicated in outbreaks of diarrhea worldwide. The objective of this study was to investigate the occurrence of aEPEC in retail foods at markets in the People's Republic of China and to characterize the isolates for virulence genes, intimin gene ( eae) subtypes, multilocus sequence types (STs), and antimicrobial susceptibility. From May 2014 to April 2015, 1,200 food samples were collected from retail markets in China, and 41 aEPEC isolates were detected in 2.75% (33 of 1,200) of the food samples. The virulence genes tir, katP, etpD, efa/lifA, ent, nleB, and nleE were commonly detected in these isolates. Nine eae subtypes were detected in the isolates, among which θ (23 isolates) and β1 (6 isolates) were the most prevalent. The 41 isolates were divided into 27 STs by multilocus sequence typing. ST752 and ST10 were the most prevalent. Antibiotic susceptibility testing revealed high resistance among isolates to streptomycin (87.80%), cephalothin (73.16%), ampicillin (51.22%), tetracycline (63.42%), trimethoprim-sulfamethoxazole (43.90%), and kanamycin (43.90%). Thirty isolates (73.17%) were resistant to at least three antibiotics, and 20 (53.66 %) were resistant to five or more antibiotics. Our results suggest that retail foods in markets are important sources of aEPEC. The presence of virulent and multidrug-resistant aEPEC in retail foods poses a potential threat to consumers. Surveillance of aEPEC contamination and prudent use of antibiotics is strongly recommended in China.

Diarrheagenic Escherichia coli Associated with Acute Gastroenteritis in Children from Soriano, Uruguay

INTRODUCTION

Acute diarrheal disease still deserves worldwide attention due to its high morbidity and mortality, especially in developing countries. While etiologic determination is not mandatory for management of all individual cases, it is needed for generating useful epidemiologic knowledge. Diarrheagenic Escherichia coli (DEC) are relevant enteropathogens, and their investigation requires specific procedures to which resources and training should be dedicated in reference laboratories.

METHODOLOGY

Following the hypothesis that enteric pathogens affecting children in towns located in the interior of Uruguay may be different from those found in Montevideo, we conducted a diagnostic survey on acute diarrheal disease in 83 children under 5 years of age from populations in the south of the country.

RESULTS

DEC pathotypes were the only bacterial pathogens found in diarrheal feces (20.48%), followed by rotavirus (14.45%) and enteric adenovirus (4.81%). Atypical EPEC (aEPEC) was the most frequent DEC pathotype identified, and unexpectedly, it was associated with bloody diarrheal cases. These patients were of concern and provided with early consultation, as were children who presented with vomiting, which occurred most frequently in rotavirus infections. aEPEC serotypes were diverse and different from those previously reported in Montevideo children within the same age group and different from serotypes identified in regional and international studies. Enteroinvasive (EIEC) O96 : H19, associated with large outbreaks in Europe, was also isolated from two patients. Antibiotic susceptibility of pathogenic bacteria identified in this study was higher than that observed in previous national studies, which had been mainly carried out in children from Montevideo.

CONCLUSION

The reduced number of detected species, the marked prevalence of aEPEC, the scarce resistance traits, and the diverse range of serotypes in the virulent DEC identified in this study confirm that differences exist between enteropathogens affecting children from interior towns of Uruguay and those circulating among children in Montevideo.

Intestinal Pathogenic Escherichia coli: Insights for Vaccine Development

Diarrheal diseases are one of the major causes of mortality among children under five years old and intestinal pathogenic Escherichia coli (InPEC) plays a role as one of the large causative groups of these infections worldwide. InPECs contribute significantly to the burden of intestinal diseases, which are a critical issue in low- and middle-income countries (Asia, Africa and Latin America). Intestinal pathotypes such as enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC) are mainly endemic in developing countries, while ETEC strains are the major cause of diarrhea in travelers to these countries. On the other hand, enterohemorrhagic E. coli (EHEC) are the cause of large outbreaks around the world, mainly affecting developed countries and responsible for not only diarrheal disease but also severe clinical complications like hemorrhagic colitis and hemolytic uremic syndrome (HUS). Overall, the emergence of antibiotic resistant strains, the annual cost increase in the health care system, the high incidence of traveler diarrhea and the increased number of HUS episodes have raised the need for effective preventive treatments. Although the use of antibiotics is still important in treating such infections, non-antibiotic strategies are either a crucial option to limit the increase in antibiotic resistant strains or absolutely necessary for diseases such as those caused by EHEC infections, for which antibiotic therapies are not recommended. Among non-antibiotic therapies, vaccine development is a strategy of choice but, to date, there is no effective licensed vaccine against InPEC infections. For several years, there has been a sustained effort to identify efficacious vaccine candidates able to reduce the burden of diarrheal disease. The aim of this review is to summarize recent milestones and insights in vaccine development against InPECs.

Characteristics of diarrheagenic Escherichia coli among children under 5 years of age with acute diarrhea: a hospital based study

BACKGROUND

Diarrhea is the leading infectious cause of childhood morbidity and mortality. Among bacterial agents, diarrheagenic Escherichia coli (DEC) is the major causal agent of childhood diarrhea in developing countries, particularly in children under the age of 5 years. Here, we performed a hospital-based prospective study to explore the pathotype distribution, epidemiological characteristics and antibiotic resistance patterns of DEC from < 5-year-old diarrheal children.

METHODS

Between August 2015 and September 2016, 684 stool samples were collected from children (< 5 years old) with acute diarrhea. All samples were cultured and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and biochemical tests. PCR was used for subtyping, and enteropathogenic E. coli (EPEC) isolates were identified simultaneously with serology. Furthermore, antimicrobial sensitivity tests and sequencing of antibiotic resistance-related genes were conducted.

RESULTS

DEC strains were identified in 7.9% of the 684 stool samples. Among them, the most commonly detected pathotype was EPEC (50.0% of DEC), of which 77.8% were classified as atypical EPEC (aEPEC). Age and seasonal distribution revealed that DEC tended to infect younger children and to occur in summer/autumn periods. Multidrug-resistant DEC isolates were 66.7%; resistance rates to ampicillin, co-trimoxazole, cefazolin, cefuroxime, cefotaxime, and ciprofloxacin were ≥ 50%. Among 5 carbapenem-resistant DEC, 60.0% were positive for carbapenemase genes (2 blaNDM-1 and 1 blaKPC-2). Among 30 cephalosporin-resistant DEC, 93.3% were positive for extended-spectrum β-lactamase (ESBL) genes, with blaTEM-1 and blaCTX-M-55 being the most common types. However, no gyrA or gyrB genes were detected in 16 quinolone-resistant isolates. Notably, aEPEC, which has not received much attention before, also exhibited high rates of drug resistance (81.0%, 66.7%, and 14.3% for ampicillin, co-trimoxazole , and carbapenem resistance, respectively).

CONCLUSIONS

EPEC was the most frequent DEC pathotype in acute diarrheal children, with aEPEC emerging as a dominant diarrheal agent in central China. Most DEC strains were multidrug-resistant, making even ciprofloxacin unsuitable for empiric treatment against DEC infection. Among carbapenem-resistant DEC strains, those harboring blaNDM-1 and blaKPC-2 were the main causal agents. blaTEM-1 and blaCTX-M-55 were the major genetic determinants associated with high levels of cephalosporin resistance.

FilmArray™ GI panel performance for the diagnosis of acute gastroenteritis or hemorragic diarrhea

Background

Acute gastroenteritis is a common cause of morbidity and mortality in humans worldwide. The rapid and specific identification of infectious agents is crucial for correct patient management. However, diagnosis of acute gastroenteritis is usually performed with diagnostic panels that include only a few pathogens. In the present bicentric study, the diagnostic value of FilmArray™ GI panels was assessed in unformed stool samples of patients with acute gastroenteritis and in a series of samples collected from pediatric patients with heamorragic diarrhea. The clinical performance of the FilmArray™ gastrointestinal (GI) panel was assessed in 168 stool samples collected from patients with either acute gastroenteritis or hemorragic diarrhea. Samples showing discordant results between FilmArray and routine methods were further analyzed with an additional assay.

Results

Overall, the FilmArray™ GI panel detected at least one potential pathogen in 92/168 (54.8%) specimens. In 66/92 (71.8%) samples, only one pathogen was detected, while in 26/92 (28.2%) multiple pathogens were detected.

The most frequent pathogens were rotavirus 13.9% (22/168), Campylobacter 10.7% (18/168), Clostridium difficile 9.5% (16/168), and norovirus 8.9% (15/168). Clostridium difficile was identified only in patients with acute gastroenteritis (p < 0.01), while STEC was detected exclusively in patients with hemorragic diarrhea (p < 0.01). In addition, Campylobacter spp., Salmonella spp., EPEC and E. coli producing Shiga-like toxin were more frequently detected in patients with hemorragic diarrhea (p < 0.05). The overall percent agreement calculated in samples was 73.8% and 65.5%, while 34.5% were discordant. After additional confirmatory analyses, the proportion of discordant samples decreased to 7.7%. Rotavirus and astrovirus were the most frequently unconfirmed pathogens.

Conclusion

In conclusion, the FilmArray™ GI panel has proved to be a valuable new diagnostic tool for improving the diagnostic efficiency of GI pathogens.

Diarrheagenic Escherichia coli

Most Escherichia coli strains live harmlessly in the intestines and rarely cause disease in healthy individuals. Nonetheless, a number of pathogenic strains can cause diarrhea or extraintestinal diseases both in healthy and immunocompromised individuals. Diarrheal illnesses are a severe public health problem and a major cause of morbidity and mortality in infants and young children, especially in developing countries. E. coli strains that cause diarrhea have evolved by acquiring, through horizontal gene transfer, a particular set of characteristics that have successfully persisted in the host. According to the group of virulence determinants acquired, specific combinations were formed determining the currently known E. coli pathotypes, which are collectively known as diarrheagenic E. coli. In this review, we have gathered information on current definitions, serotypes, lineages, virulence mechanisms, epidemiology, and diagnosis of the major diarrheagenic E. coli pathotypes.

Atypical enteropathogenic Escherichia coli as aetiologic agents of sporadic and outbreak-associated diarrhoea in Brazil

Enteropathogenic Escherichia coli (EPEC) are important agents of diarrhoea in industrialized as well as developing countries, such as Brazil. The hallmark of EPEC pathogenesis is the establishment of attaching and effacing lesions in enterocytes, in which pedestal-like structures are formed underneath adherent bacteria. EPEC are divided into two subgroups, typical (tEPEC) and atypical (aEPEC), based on the presence of the EPEC adherence factor plasmid in tEPEC and its absence in aEPEC. This study was designed to characterize 82 aEPEC isolates obtained from stool samples of diarrhoeic patients during 2012 and 2013 in Brazil. The majority of the aEPEC were assigned to the phylo-group B1 (48.8 %), and intimin subtypes θ (20.7 %), β1 (9.7 %) and λ (9.7 %) were the most prevalent among the isolates. The nleB and nleE genes were concomitantly detected in 32.9 % of the isolates, demonstrating the occurrence of the pathogenicity island O122 among them. The O157-plasmid genes (ehxA and/or espP) were detected in 7.3 % of the isolates, suggesting that some aEPEC could be derived from Shiga-toxin-producing E. coli that lost the stx genes while trafficking in the host. PFGE of 14 aEPEC of serotypes O2 : H16, O33 : H34, O39 : H9, O108 : H- and ONT : H19 isolated from five distinct outbreaks showed serotype-specific PFGE clusters, indicating a high degree of similarity among the isolates from the same event, thus highlighting these serotypes as potential aetiologic agents of diarrhoeal outbreaks in Brazil.