Resumo

Introduction: EPEC strains produce an adherence factor, called intimin, which is chromosomally encoded by the eae (EPEC attaching and effacing) gene located within the locus for enterocyte effacement (LEE) pathogenicity island. “Typical” EPEC contain, in addition to eae, the EPEC adherence factor (EAF) plasmid, which encodes the bundle-forming pili (BFP) and a transcriptional activator called plasmid-encoded regulator (Per). EPEC strains, lacking the EAF plasmid, have been designated “atypical” EPEC (aEPEC). The aim of this study was to describe the allelic diversity of critical EPEC virulence genes in atypical and typical EPEC to provide insights into the relationship between the two groups. Methods: A collection of 105 EPEC strains belonging to the 12 classic EPEC O serogroups and isolated from a diarrhea epidemiological study in Brazilian children were characterized for the allele type of eae and perA genes by PCR-RFLP. Results: Typical EPEC (eae+, bfp+) were the most common pathotype in diarrhea (47/87, 54%) in diarrhea, whereas aEPEC (eae+, bfp-) were the most common in control samples from children without diarrhea (11/18, 61.1%). Overall, there were 9 eae alleles; the most common were beta(29/105, 27.6%), gamma (13/105, 12.4%), alpha (8/105, 7.6%), iota(3/105, 2.9%), epsilon2(3/105, 2.9%), epsilon1(2/105, 1.9%), alpha2(2/105), 1.9%), tau1 (1/105, 0.9%) and teta(1/105, 0.9%). There were four perA alleles: alpha (16/49, 32.6%), beta (15/49, 30.6%), delta (10/49, 20.4%) and gamma (2/49, 4.1%). The strains belonged to 9 different EPEC serogroups O26, O55, O86, O111, O114, O119, O126, O127, O128, and O142; O119 was the most frequent. There were no significant differences in the distribution of intimin alleles between diarrhea and control samples or in their distribution between typical and atypical strains. The majority of atypical strains were negative for perA by PCR strains, whereas 58.3% of O119 strains were delta-perA. Conclusion. Further studies are necessary to evaluate additional virulence markers determine whether relationships exist between both EPEC groups.