Pathogenicity of Vibrio parahaemolyticus in tiger prawn Penaeus monodon Fabricius:: possible role of extracellular proteases

Tiger prawn, Penaeus monodon, were experimentally challenged with a virulent strain of Vibrio parahaemolyticus 25C, originally isolated from Penaeus orientalis in an outbreak of red leg disease at a shrimp farm in the People's Republic of China. The strain was found to be highly virulent to P. monodon with an LD50 value of 1 X 10(5) colony forming units (CFU)/prawn. The extracellular products (ECP) of the bacteria were also found to be toxic with an LD,, value of 8 mug protein/prawn. The strain was found to be a poor producer of hemolysins. Extracellular proteases present in the ECP were purified by Sephadex G-150 gel filtration and further analyzed by SDS-polyacrylamide gel electrophoresis. Two fractions viz., F I and F II, were obtained and both were found toxic to tiger prawns, but heat-inactivated fractions were not toxic. (C) 2001 Elsevier Science B.V. All rights reserved.