Abstract
Vibrio cholerae is a usual inhabitant of the marine environment and causes severe diarrheal disease contaminating thousands of people each year in developing countries. The virulence of Vibrio spp. is regulated by the ctxAB and tcpA genes. These genes are supposed to be exclusively associated with clinical strains of O1 and O139 serogroups. In the present study, we examined the presence of virulence genes that contains OmpW, ctxA and tcpA of V. cholerae classical and Eltor variants in environmental strains of non-O1 and non O139 V. cholerae that were cultured seasonally from four sampling stations of the Karun River in Ahwaz. One hundred water samples were collected from four stations of Ahvaz Karun River. The colonies that were grown on TCBS confirmed to beVibrio spp. by biochemical, serological and molecular methods. After DNA extraction, a polymeras chian reaction (PCR) assay was performed for detection of ctxA and tcpA (both Classical and ElTor variants) and OmpW was in the strain that was recognized asV. cholerae non - O139 and non - O1. Among 100 environmental samples of fresh water in this study, 27 isolate confirmed as V. cholerae spp. by PCR assay with ompW gene. Of among them, 4 isolate that were confirmed V. cholerae non O1- non O139 had gene for toxin coregulated pilli (Classical and Eltor). V. cholerae is one of the major causes of morbidity and mortality in the developing countries. The studies that were performed on V. cholera nonO1, nonO139 strains that usually do not carry the ctx genes coding for cholera toxin (CT) or toxin-co regulated pilus which are the most important virulence characteristics of the cholera causing strains. Key words: Vibrio cholerae non-O1, non-O139, ctxA, tcpA, OmpW.
Highlights
Cholera is still a threat to a large number of people in the universe
We examined the presence of virulence genes that contains OmpW, ctxA and tcpA of V. cholerae classical and Eltor variants in environmental strains of non-O1 and non O139 V. cholerae that were cultured seasonally from four sampling stations of the Karun River in Ahwaz
The studies that were performed on V. cholera nonO1, nonO139 strains that usually do not carry the ctx genes coding for cholera toxin (CT) or toxinco regulated pilus which are the most important virulence characteristics of the cholera causing strains
Summary
Cholera is still a threat to a large number of people in the universe. In 2009, 45 countries reported 221,226 cholera cases and 4,946 cholera deaths (case-fatality ratio, 2.24%) to WHO (WHO, 2010). Haiti is the latest country to be affected by the ongoing cholera pandemic which began 49 years ago in Sulawesi, Indonesia, and has lasted longer and spread farther than any previously known cholera pandemic (Wachsmuth et al, 1994). The causal organism of cholera can be classified into >200 serogroups according to the differences in antigenicity of their heat-stable somatic O antigen (Shimada et al, 1994). Pathogenic and epidemic strains of V. cholerae contains two essential genetic elements, CTX element and the vibrio pathogenicity island (VPI) which are concerned in coding for cholera
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