Regulation of iron on bacterial growth and production of thermostable direct hemolysin by Vibrio parahaemolyticus in intraperitoneal infected mice.

Pathogenesis of Vibrio parahaemolyticus is not clearly understood. Effects of iron on the bacterial proliferation and production of thermostable direct hemolysin (TDH) in intraperitoneal infected mice were studied. Injection of bacterial culture in the presence of ferric ammonium citrate (100 micrograms/ml) significantly enhanced the lethality for mice, and simultaneously activated bacterial proliferation in vivo. The iron-limited cultures showed better proliferation than those iron-rich cultures in response to the addition of supplementary iron source. Production of TDH by the hemolytic strains ST550 and D62 was higher in the iron-limited cultures than the iron-rich cultures. Production of TDH by both the iron-limited or iron-rich cultures was inhibited by the addition of iron. In conclusion, the virulence enhancement effect of iron in V. parahaemolyticus was probably by activating bacterial proliferation in vivo and not by stimulating the production of TDH. V. parahaemolyticus precultured in iron-limited condition may be more adaptable to in vivo environment.