Vibrio cholerae and other vibrios associated with paddy field cultured prawns

Abstract

During a 6-month survey, 131 prawn samples belonging to five different species cultured in paddy fields were examined for the presence ofVibrio cholerae and related vibrios associated with human disease. Non-O1V. cholerae was the most commonVibrio species associated with the prawn samples followed byV. parahaemolyticus, V. mimicus, V. vulnificus andV. alginolyticus, in that order.V. cholerae non-O1 appeared to constitute the normal microflora of prawns and this association was not limited by salinity. Examination of a representative number ofV. cholerae andV. parahaemolyticus isolates for established virulence factors revealed that none of theV. cholerae strains possessed genes that were homologous with cholera-toxin genes and none produced a heat stable enterotoxin while none of theV. parahaemolyticus isolates were Kanagawa phenomenon-positive and most of the strains were untypeable. The presence of such high numbers of vibrios in paddy field cultured prawn samples and its impact on the bacteriological quality of prawns destined for human consumption needs critical assessment.