Molecular genotyping of Escherichia coli o111 isolated from children with diarrhea in rural and urban areas

Introduction: Enteropathogenic Escherichia coli (EPEC) is a group of bacteria associated with infantile diarrhea. EPEC is defined as being typical (tEPEC) or atypical (aEPEC) depending on whether it presents the EPEC adherence factor (EAF) plasmid or not; tEPEC presents EAF. Objective. Carry out a retrospective study of E. coli strains isolated from children with diarrhea in both rural and urban areas to determine if they belong to tEPEC or aEPEC groups. Material & Methods: Strains that had been reported to be E. coli were analyzed by PCR using specific primers and 188 anti-O sera and 53 anti-H sera. The presence of eae, bfp, eafA, perA, espC and espP genes associated with virulence was analyzed, as was the presence of arpA, chuA, yjaA and TspE4 to define phylogroups. Results: Fifty-three cultures of E. coli isolated between 1985 and 2003 from 35 children under five years of age with severe diarrhea were analyzed. Twelve (34.3%) children came from a rural area and 23 (65.7%) from an urban area. Serologic typing identified the following serotypes: O111ab:NM (67.9%), O111ab:H2 (20.8%), O111ab:H12 (9.4%) and O111ac:H8 (1.9%). The presence of eae was positive in all 53 strains, while bfp and perA was detected in 38 (71.7%) strains and eaf in 35 (66%) strains. The combination of eae/bfp used to determine typical strains was positive in 38 (71.7%) strains and negative in 15 (28.3%) strains. Analysis by year and region showed that between 1985 and 1987, 35 (66%) strains were typical and 4 (7%) atypical in the rural area and urban area1. The same analysis between 1994 and 2003 in the urban areas showed that 11 (20.8%) strains were atypical, which were eae positive but eaf/bfp/perA negative, and 3 (5.7%) strains were typical. Phylogenetic grouping identified B1 and A in 38 (71.7%) and 9 (17%) strains respectively, and 2 (3.8%) each of B2, D and F. Conclusion. Typical EPEC strains were more prevalent in both the rural and urban areas between 1985 and 1987. In contrast, the presence of atypical EPEC strains was more prevalent in urban areas in more recent years. Analysis showed that the strains fell predominantly into commensal phylogroups.