Study of the resistance of Streptococcus iniae, Aeromonas hydrophila and Yersinia ruckeri to some environmental factors

Objective: In this study, Streptococcus iniae, Yersinia rucker, and Aeromonas hydrophila the causative agents of streptococcosis, enteric red mouth disease and hemorrhagic septicemia, respectively, in rainbow trout were subjected to some environmental factors such as temperature, salinity and pH. Method & Materials: Bacteria were grown on brain hearth infusion agar and incubated in different temperatures for 48h. For salinity measurement, bacteria were grown in tipticase soy bean broth with different percent of salt also for pH measurement, bacteria were grown in the broth with different pH. Broth cultures were incubated in 25ºC for 48h. Results & Conclusion: Results showed that all three bacteria tolerated 4ºC, however, they did not grow in temperature above 45º C. Streptococcus iniae also grew in 2ºC, salinity up to 3.5% and pH of 7-9. Yersinia ruckeri grew in salinity up to 4% and pH of 6-10. Aeromonas hydrophila grew in salinity up to 5% and pH of 6-10. These data could assist veterinarians to establish control strategies when visiting fish farms.