Distribution of genes encoding toxins and antibiotic resistance patterns in diarrhoeagenic Escherichia coli isolates in Tehran

Pathogenicity of Escherichia coli can involve a large number of virulence factors, toxins being the most obvious. We assessed the distribution of genes encoding toxins among E. coli isolates from diarrhoeal cases using DNA probes. From 200 isolates, 92 (46.0%) carried genes encoding for toxins, 43.5% of these being multitoxigenic. Enteroaggregative heat-stable enterotoxin was detected in 40 (43.5%) isolates, verotoxin in 38 (41.3%), cytolethal distending toxin in 24 (26.1%), heat-stable enterotoxin in 12 (13.0%) and heat-labile enterotoxin in 10 (10.9%). Furthermore, 40 strains (70.0%) carried resistance. We conclude that toxigenicity and antibiotic resistance are the main contributing factors leading to the virulence potential of these E. coli isolates.