Prevalence and characteristics of escherichia coli isolates harbouring shiga toxin genes (STX) from acute diarrhoeal patients in Dhaka, Bangladesh

Abstract

Shiga toxin genes (stx) harbouring Escherichia coli (STEC) strains were isolated and identified from diarrhoeal patients visiting the Dhaka Hospital of ICDDR,B: Centre for Health and Population Research, Dhaka, Bangladesh. Of the 189 E. coli strains isolated from 775 diarrhoeal stool specimens, 19 harboured stx1, and one isolate was revealed to have amplicons for both stx1 and stx2 by a PCR assay. Sequence analysis of the 349-bp stx1 from representative isolates revealed 100% homology with the sequence of stx1 available in the GenBank. Among the stx1 positive isolates, two harboured the eae but none were positive for hlyA, katP, etpD or saa genes. Fifteen of the 20 stx positive strains could be categorized into 13 non-O157 serogroups while 4 were untypable and one was a rough strain. Most of the STEC strains were resistant to ampicillin, cephalothin, co-trimoxazole, tetracycline, and nalidixic acid. In the Vero cell assay, all the strains were negative for expression of Shiga toxin (Stx). Randomly amplified polymorphic DNA (RAPD) PCR analysis demonstrated genetic diversity. This is one of the first reports to show the presence of STEC in diarrhoeal patients in Bangladesh.