Toxigenic Vibrio cholerae, the cause of cholera, is a native flora of the aquatic environment which is transmitted through drinking water and still remains the leading cause of morbidity and mortality in many developing countries. In the present study, we examined the presence of virulence genes (ctxA, ctxB and tcpA of El Tor) in environmental strains of V. cholerae cultured from three sampling stations of the Sarchnar stream in Sulaimania-Iraq. We also evaluated the effect of different pre-PCR conditions: 1- water filtered and enriched in alkaline peptone water (APW) for 6 h before PCR, 2- water filtered without enrichment before PCR, and 3- use of only enrichment in APW for 6 h before PCR. Unexpectedly, the PCR analysis of 2 out of 30 isolates revealed the presence of cholera toxin genes (ctxA, ctxB) and the gene for toxin co-regulated pilus (tcpA) among environmental non-O1 V. cholerae isolates. To our knowledge, this is the first evidence of the presence of toxin genes in non-O1 V. cholerae from the water environment in north Iraq. This study supports the idea that cholera toxin has an environmental derivation and that the intricate aquatic environment can give rise to pathogenic Vibrio organisms.
Key words: Vibrio cholerae, ctxA, ctxB, tcpA gene, environmental isolates, PCR
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