Virulence of Starved Aeromonas hydrophila to Cyprinid Fish

Abstract

The survival of Aeromonas hydrophila was studied in a variety of waters containing different concentrations of salts. The survival of A. hydrophila for a period of 120 h was found to be optimal at 0.85 and 0.35% NaCl, 1% KC1, 0.2% CaCl₂ · 2H₂O or 0.4% MgCl₂·6H₂O, respectively. Among the formulated salt water solutions examined, the best survival was found in that containing 0.60% NaCl, 0.50% KCl, 0.10% CaCl₂· 2H₂O and 0.20% MgCl₂· 6H₂O in distilled water (FW₂). Virulence of the bacterium starved for 24 h in FW₂ and 0.85% NaCl was compared to that of the bacterium cultured in nutrient broth to carp and goldfish by intraperitoneal injection. The median lethal dose obtained by the infection verified that the bacterium starved in both salt solutions had obviously higher virulence than the cultured bacterium.