Virulence of Vibrio harveyi possessing a transferable chloramphenicol resistance determinant to larvae of Indian white shrimp Fenneropenaeus indicus (Decapoda)

275-278The virulence of luminous Vibrio harveyi possessing a transferable chloramphenicol-resistance determinant to Indian white shrimp, Fenneropenaeus indicus larvae was studied. The V. harveyi strains isolated from luminous F. indicus larvae produced extracellular virulence factors such as haemolysin, chitinase, proteinase, lipase and phospholipase were resistant to at least four of six antibiotics tested. The chloramphenicol-resistance determinant was transferred from V. harveyi to Escherichia coli at frequencies of 6.69 10⁻⁴ - 4.27 10⁻³. The concentration of V. harveyi cells capable of causing 50% mortality differed significantly (P