RESUMO
Atypical enteropathogenic Escherichia coli (aEPEC) has emerged as a significant cause of pediatric diarrheaworldwide; however, information regarding its adherence mechanisms to the human gut mucosa is lacking. Inthis study, we investigated the prevalence of several (fimA, ecpA, csgA, elfA, and hcpA) fimbrial genes in 71aEPEC strains isolated from children with diarrhea (54 strains) and healthy individuals (17 strains) in Braziland Australia by PCR. These genes are associated with adhesion and/or biofilm formation of pathogenic andcommensal E. coli. Here, the most prevalent fimbrial genes found, in descending order, were hcpA (98.6%), ecpA(86%), fimA (76%), elfA (72%), and csgA (19.7%). Phenotypic expression of pili in aEPEC strains was assessedby several approaches. We were not able to detect the hemorrhagic coli pilus (HCP) or the E. coli lamininbindingfimbriae (ELF) in these strains by using immunofluorescence. Type 1 pili and curli were detected in59% (by yeast agglutination) and 2.8% (by Congo red binding and immunofluorescence) of the strains,respectively. The E. coli common pilus (ECP) was evidenced in 36.6% of the strains on bacteria adhering toHeLa cells by immunofluorescence, suggesting that ECP could play an important role in cell adherence forsome aEPEC strains. This study highlights the complex nature of the adherence mechanisms of aEPEC strainsinvolving the coordinated function of fimbrial (e.g., ECP) and nonfimbrial (e.g., intimin) adhesins andindicates that these strains bear several pilus operons that could potentially be expressed in different nichesfavoring colonization and survival in and outside the host.