Clonal groups of enteropathogenic escherichia coli isolated in case-control studies on diarrhoea in Bangladesh

Abstract

Objective: Investigate the clonal status of enteropathogenic Escherichia coli (EPEC) strains isolated from case-control studies in Bangladesh. Methodology: Eighty EPEC isolates from children with diarrhoea and 14 isolates from matched healthy controls from two case-control studies were analyzed. The first study, conducted during 1991-1992, comprised 451 children aged up to five years with diarrhoea and 602 matched control children without diarrhoea. The second study, conducted during 1991-1994, comprised 546 children with diarrhoea and 215 matched healthy children recruited from the same neighbourhood. The EPEC isolates were characterized by serogrouping, enterobacterial repetitive intergenic consensus (ERIC) sequence PCR, and biochemical fingerprinting method (the automated phene plate or PhP system). Results: Twelve EPEC serogroups were found with 0114 (n=19) and 0127 (n=23) being the dominant serogroups. Most strains of 0114 serogroup belonged to the same PhP and PCR types. Strains of 0127 serogroup contained those producing cytolethal distending toxin CDT (n=16) and those which did not (n=7). Both were found among the patients and the controls, the results of PCR and PhP typing showed that the CDT-positive strains belonged to the same clonal group and were related to one of the two PhP/PCR types of CDT-negative O127 strains. Thirty-one O-non-typable EPEC strains and 21 strains of other less prevalent serogroups belonged to diverse Ph/PCR types. Furthermore, they did not show any similarity to the strains of the two major serogroups: 0114 and 0127. Conclusion: Recent case-control studies in Bangladesh showed a high prevalence of EPEC strains associated with childhood diarrhoea. The results of the present study suggest that single clonal groups of EPEC strains belonging to serogroup O114 and O127 are predominantly associated with childhood diarrhoea in Bangladesh