Optimum Temperatures for the Peak Growth of Some Selected Bacterial Fish Pathogens

The optimal growth temperatures for 24 strains of 15 bacterial fish pathogens were determined under uniform cultural conditions. For Flavobacterium psychrophila, peak growth temperature (tpeak) was 21±0.4°C for the strain tested. Flavobacterium columnaris exhibited 29.8±0.2 and 29.9±0.3°C, respectively, as tpeaks for two strains. The tpeaks of Flavobacterium branchiophilum were 24.9±0.2 and 24.1±0.5°C, respectively, for two strains. Three strains of Edwardsiella tarda were examined and they showed tpeaks at 36.1±0.4, 35.5±0.2 and 36±0.3°C, respectively. Citrobacter freundii showed its tpeak at 36.1±0.4°C. For Aeromonas hydrophila, two strains were tested and it was found that tpeaks were 32.9±0.6 and 34.8±0.5°C, respectively. The tpeaks of Aeromonas salmonicida were 26.1±0.4 and 25.6±0.2°C, respectively. Temperature 27.8±0.3°C was found as tpeak of a Vibrio anguillarum strain while Vibrio ordalii strain exhibited it at 26.5±0.4°C. Peak growth at temperatures of 26.7±0.5 and 27.6±0.4°C, respectively, was found for Photobacterium damselae (formerly Pasteurella piscicida). In Pseudomonas fluorescens, the peak growth occurred at temperatures of 29.9±0.2 and 28.5±0.3°C, respectively. Pseudomonas sp. showed tpeaks at 24.9±0.1 and 29.2±0.5°C, respectively. The peak growth for the two strains of Lactococcus garvieae (formerly Enterococcus seriolicida) was at tempera-tures of 29.7±0.4 and 31.1±0.2°C, respectively where the Streptococcus sp. showed tpeak at 28.3±0.5°C.