[Virulence-related genes of Vibrio alginolyticus and its virulence in mice]

We determinated the virulence factors of Vibrio alginolyticus strains isolated from the environment by multiplex PCRs and animal experiments, in order to compare the differences between the highly virulent strain and attenuated virulent strain, and to explore the virulent mechanism of V. alginolyticus in mammals.

The virulence-related genes of V. alginolyticus were investigated by multiplex PCRs. Hemolysin and pathogenic proteins were detected using Kanagawa phenomenon tests and enzyme activity tests. In vivo pathogenetic tests of V. alginolyticus were done through orogastric and intraperitoneal Kunming mouse.

Amylase and lecithinase activities were observed in 100% of the strains, whereas lipase and gelatinase activities were found in only 70% and urease activity was not detected. In Kanagawa phenomenon tests 60% of the strains gave positive results. The related virulence genes such as toxR, Collagenase, tlh, FlaA, ompW, AspA and fur were distributed among 10 strains of V. alginolyticus collected, with the exception of toxS, trh, tdh and UreR. Among those 10 strains, VA009 has shown a strong pathogenesis to the mouse, which caused fluid accumulation and led the mortality rate as high as 80% within 7 days by intraperitoneal infection.

This study indicates that there is a great difference in pathogenicity among V. alginolyticus strains to mouse. The cell toxicity of V. alginolyticus made more contribution than extracellular secretion, while the extracellular secretion of V. parahaemolyticus played a major role in its toxicity. The virulence gene profiles were consistent between the highly virulent and attenuated virulent strains, indicating that V. alginolyticus might have a different virulence system and different pathogenic mechanism compared with V. parahaemolyticus.