Detection of Cholera Toxin-Producing Vibrio cholerae in Phytoplankton from Santubong and Samariang Estuaries

Many cholera outbreaks worldwide were associated with cholera toxin-producing Vibrio cholerae. The bacteria are ubiquitous in aquatic environment, whilst phytoplankton is associated with adaptation of the Vibrio species. This study was conducted to detect cholera toxin-producing Vibrio cholerae, and to determine association of the selected water physicochemical parameters with the number of the bacteria. In this study, a total of ten phytoplankton samples were collected at Santubong and Samariang Estuaries in Kuching, Sarawak. Water physicochemical parameters (temperature, pH and salinity) were recorded. Vibrio bacteria were cultivated on thiosulfate citrate bile-salts sucrose selective agar and analysed for cholera toxin-producing Vibrio cholerae using polymerase chain reaction by targeting ctxA gene that encodes for virulence cholera enterotoxin subunit A. The result revealed that a range of 1.0 × 107 – 8.0 × 107 CFU/ml of yellow colonies growing on the thiosulfate citrate bile-salts sucrose agars. Inversely, no samples were positive with cholera toxin-producing Vibrio cholerae. The physicochemical parameters at Samariang Estuary were more associated with the number of bacteria in the samples compared to Santubong Estuary.