Alikhani, “Serotypes of enteropathogenic Escherichia coli isolated from children under 5 years of age

Background: The purpose of this study was to find out the frequency of different serotypes of enteropathogenic Es-cherichia coli (EPEC) among healthy/diarrheal cases. Methods: A total of 191 strains, 111 from diarrheal and 80 from asymptomatic persons were examined. Determination of the EPEC serogroups was performed by agglutination tests using polyvalent and monovalent O antiserum. PCR-RFLP analysis of the flagellin-encoding (fliC) gene and agglutination tests using polyvalent and monovalent sera against H antigens (H1 to H 56) according to the instructions of the manufacturer was performed. Results: Seventeen (8.9%) strains were non-motile and untypable with conventional serotyping method that showed as H-. Forty-three fliC restriction patterns were found for motile and non-motile serotypes. Each motile serotype was characterized by one or two fliC specific restriction patterns. O142:H48 (6.8%), O86:H48 (6.3%), O111:H21 (4.7%) and O127:H21 (4.2%) were the most prevalent serotypes, and O55:H12/45, O86:H48, O127:H21, O142:H48, O126:H48 and O126:H19 serotypes were the most frequently agents in diarrheal cases, compared to asymptomatic children (P< 0.05). There were common EPEC serotypes in diarrheal and asymptomatic children, however some serotypes either found only in diarrheal cases or isolated from asymptomatic persons. Conclusion: Some serotypes were isolated more frequently from diarrheal cases than asymptomatic persons. The conven-tional serological method using antisera is the basis for the H typing system in E-coli, but it is impossible to serotype non-motile bacteria. PCR-RFLP analysis of fliC gene is a practical method in identifying the H variant in motile and non-motile EPEC serotypes and is useful for epidemiological studies