Genetic relatedness of a non-motile variant O157 enteropathogenic Escherichia coli (EPEC) strain and E. coli strains belonging to pathogenic related groups.

ABSTRACT

The study was undertaken to determine the clonal relationship and the genetic diversity among Escherichia coli isolates by comparing a non-motile O157 variant with three O157H7 EHEC isolates and one O55H7 enteropathogenic E. coli (EPEC) strain. E. coli strains were characterized by sorbitol phenotype, multilocus enzyme electrophoresis, pulsed-field gel electrophoresis, random amplification polymorphic DNA, and the presence of specific virulence genes (stx, E-hly and LEE genes). Sorbitol fermentation was observed in O157H- (strain 116I), O55H7 and O157H7 (strain GC148) serotypes. stx1 or stx2 and E-hly genes were only detected among O157H7 isolates. LEE typing revealed specific allele distribution eaegamma, tirgamma, espAgamma, espBgamma associated with EPEC O55H7 and EHEC O157H7 strains (B1/1 and EDL 933), eaealpha, tiralpha, espAalpha, espBalpha related to the 116I O157H- strain and the GC148 strain presented non-typable LEE sequences. Multilocus enzyme profiles revealed two main clusters associated with specific LEE pathotypes. E. coli strains were discriminated by random amplification of polymorphic DNA-polymerase chain reaction and pulsed-field gel electrophoresis methodologies. The molecular approaches used in this study allowed the determination of the genetic relatedness among E. coli strains as well as the detection of lineage specific group markers.