[HeLa-cell adherence patterns of shiga toxin- producing Escherichia coli [STEC] serotypes isolated from faecal samples]

ABSTRACT

Shiga toxin-producing Escherichia coli [STEC] has been recognized as an important cause of diarrheal diseases. The ability to colonize the human intestine is an essential part of the infection. To determine the importance of the adherence among non-O157 STEC serotypes isolated from diarrheal and asymptomatic healthy persons, HeLa cell adherence pattern was studied. Polymerase chain reaction-restriction fragment length polymorphism [PCR-RFLP] analysis of the flagellin gene [fliC] was performed in 35 strains of STECO serogroups for determining their flagellar antigen [H] status. The entire coding sequence of fliC was amplified by PCR, the amplicon was restricted with HhaI, and the restriction fragment pattern was examined after gel electrophoresis. The adherence property of 35 Shiga toxin-producing Escherichia coli [STEC] not belonged to O157H7 serotype was checked on HeLa cell adherence pottern. Three to five individual colonies from each case were assessed. These strains were isolated from patients with bloody, non-bloody diarrhea and healthy cases. Of the 35 STEC colonies, 2 strains [5.7%] were isolated from bloody diarrheal cases, 25 strains [71.5%] from non-bloody diarrheal and 8 strains [22.8%] from healthy persons. None of the strains belonged to O157 H7 serotype but 22 strains belonged to O126 and O128, O26 and O111 serogroups. Out of 27 strains isolated from bloody and non-bloody diarrheal cases 3 strains [11.1%] were non-adherent [NA] and 24 strains [88.9%] were adherent. However, aggregative adherence [AA] was observed in 10 serotypes [O128 H2, O128 H9, O125 H12 and O125 H15] and diffuse adherence [DA] and localized adherence [LA] were exhibited by 1 serotype, respectively. The remaining 12 strains showed non-specific adherence [NSA]. Among adherence patterns, LA and AA were found to be significantly associated with diarrhea [p < 0.001]. Human pathogenicity of E. coli strains belonging to STEC group varied according to serotypes, virulence attribute and adherence patterns. Based on the observation obtained in this study, it can be concluded that STEC strains with adherence property are more virulent than the non-adherence ones and further detail studies on adherence factors and their mechanisms of pathogenesis are needed