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

Abstract

Recent case-control studies in Bangladesh showed a high prevalence of enteropathogenic Escherichia coli (EPEC) strains (identified by DNA probes for virulence genes) associated with childhood diarrhoea. However, the clonal status of these strains is not known. A total of 94 EPEC isolates from 80 children with diarrhoea and 14 healthy matched controls isolated during 1991-1992 and 1993-1994 was characterised by serogrouping, enterobacterial repetitive intergenic consensus sequence PCR, and by a biochemical fingerprinting method (the phene plate or PhP system). Twelve O serogroups were found with O114 (n = 19) and O127 (n = 23) being the dominant serogroups. Most strains of O114 belonged to the same PhP/PCR types. Strains of O127 contained 16 that produced cytolethal distending toxin (CDT) and seven that did not; both were found among patients as well as controls. Results of PCR and PhP typing showed that 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 EPEC strains were O non-typable and 21 strains belonged to other less prevalent serogroups. These strains belonged to diverse PhP/PCR types and did not show any similarity to the strains of two major serogroups, O114 and O127. The results suggest that two clonal groups of EPEC strains are predominantly associated with childhood diarrhoea in Bangladesh