Detection and characterization of verotoxin-producing strains among sorbitol non-fermenting Escherichia coli

ABSTRACT

The presence of genes for verotoxin 1 and 2 [VT1 and 2] among sorbitol non-fermenting Escherichia coli isolates from diarrhoeal cases was assessed using polymerase chain reaction assay. Of 60 [88%] positive isolates, 37 [62%] harboured VT1 and 23 [38%] both VT1 and VT2. In HeLa cell adherence assay, 48 [71%] isolates exhibited mannose-resistant adherence to HeLa cells. Multidrug resistance was observed in 56 [82%] isolates, with ampicillin, chloramphenicol, streptomycin, sulfamethoxazole-trimethoprim and tetracycline pattern being the most common. There were 13 common and 22 single biochemical phenotypes identified. Isolates belonging to common biochemical phenotypes normally had a similar pattern of adherence and VT production, but differed greatly in their pattern of antibiotic resistance, pointing to a high rate of antibiotic-resistance transfer among these isolates