Investigation of culturable vibrio cholerae 01 and 0139 from selected aquatic environments along the coastal areas of Tanzania

Vibrio cholerae are capable of inhabiting multiple niches in the aquatic environment. However, their diversity and ecology in aquatic settings along the coast of Tanzania remains poorly understood. This study aimed at establishing the distribution of culturable V. cholerae serogroup O1 and O139 in the selected estuaries of Tanzania namely: Pangani, Mzinga Creek and Ruvu. A total of 480 samples were collected between July 2009 and June 2010 from three stations along the salinity gradients (i.e., fresh water, brackish and marine waters) on each estuary. The samples were then enriched in alkaline peptone water and inoculated on TCBS agar. Sucrose fermenting colonies were then subjected to biochemical tests; oxidase and Analytical Profile Index tests (API 20E kit) followed by serological tests. DNA extraction and PCR was used to screen for the presence of cholera toxin gene ctx in all isolates identified by API 20E kit. In total, 39 isolates were found to be V. cholerae with cholera toxin gene, whereby, 5 (13%) isolates were V. cholerae O1 the only toxigenic serogroup to have been isolated in Tanzania and 1 (3%) was V. cholerae O139 which had never been reported to be found in Tanzania. V. cholerae O1 were found to be harbored most in free waters and in zooplanktons samples. However phytoplankton samples were observed to harbor more other toxigenic V. cholerae (64%) which have never even been isolated from clinical samples in Tanzania. Marine waters were found to have higher occurrence of all toxigenic V. cholerae (54%) than brackish waters (23%) and fresh waters (23%). The occurrence of V. cholera O1 was found in all the three estuaries while V. cholerae O139 was found only in Ruvu estuary. The findings from this study suggest that marine waters in associations with planktons are the best ecological niche for culturable toxigenic V. cholerae and may be a good source of spread of this bacterium to human being.