CLASSIFICATION OF ISOLATES OF VIBRIO-HARVEYI VIRULENT TO PENAEUS-MONODON LARVAE BY PROTEIN PROFILE ANALYSIS AND M13 DNA-FINGERPRINTING

A total of 17 Vibrio harveyi isolates were examined for virulence to Penaeus monodon larvae and classified by total soluble protein profiles generated by sodium-dodecyl-sulphate polyacrylamide-gel electrophoresis (SDS-PAGE) under reducing conditions. Two isolates out of 17 proved to be virulent. Most isolates fell. within 2 protein groups. Group I was characterised by a 42 kDa protein and contained 8 isolates including both virulent isolates. Group II was characterised by a 40 kDa polypeptide and contained 7 isolates. A further 2 isolates could not be assigned to either group, Isolates were further characterised by M13 DNA fingerprinting. V. harveyi isolates were compared to V. parahaemolyticus isolates and found to be substantially more diverse in genotype. This suggested high genetic diversity within V. harveyi. The separation of isolates into Groups I and II by SDS-PAGE was shown to be genetically based, however the 2 virulent isolates classified within Group I did not demonstrate a high genetic association. Based on the present results, it is suggested that virulent isolates within V. harveyi are rare and that virulence may be explained by genetic transfer of virulence factors.