Coliform in Shrimp Farms: Total Content and Detection of Enterovirulent Escherichia Coli Strains by Polymerase Chain Reaction

Abstract

The presence of coliform indicates that Citrobacter, Enterobacter, Escherichia, Hafnia and Klebsiella as well as other pathogenic bacteria such as Salmonella sp., Shigella sp. and Vibrio sp. might be present. In Bangladesh, traditional shrimp culture farms are highly susceptible to contamination with pathogenic bacterial species because of lacking proper sanitation near to these farms. However, the aim of the present study was to quantify coliform as well as enterovirulent groups (EHEC, enterohaemorrhagic, EPEC, enteropathogenic and ETEC, enterotoxigenic) of E. coli in different shrimp farms in Khulna district, Bangladesh. Water samples were collected in winter (November to February, 2011-2012) and summer (May to August, 2011-2012) seasons. All the farms were contaminated with coliform but E. coli was present only in 55% farms. The number of coliform was varied from season to season and also farm to farm. In winter season, average number of coliform and E. coli in hygienic farms were 4.94 × 10² (cfu/mL) and 0 (cfu/mL) whereas that in unhygienic farms were 8.17 × 10² (cfu/mL) and 4.15 × 10² (cfu/mL), respectively. However, in summer the number were larger than winter. In the summer, the number of coliform and E. coli in hygienic farms were 82.65 × 10² (cfu/mL) and 8.51 × 10² (cfu/mL) whereas that in unhygienic farms were 111.32 × 10² (cfu/mL) and 45.27 × 10² (cfu/mL), respectively. Using cultural, biochemical and PCR technique, 76 E. coli were identified. Among them, EPEC and ETEC groups were 22% and 29%, respectively whereas EHEC group was absent. Based on the results, it might be concluded that 55% shrimp farms of Khulna district were contaminated by feces and unsafe for shrimp production.