Virulent Aeromonas hydrophila (vAh), a Gram-negative, facultative anaerobic pathogen, causes severe outbreaks of motile Aeromonas septicemia (MAS) in U.S. catfish production, the largest component of the aquaculture industry in the United States. In 2022, catfish production contributed $447 million to the nation’s economy according to estimates by the USDA. Tens of millions of pounds of market-size catfish are lost annually due to this significant catfish pathogen. Typically, A. hydrophila causes swift outbreaks characterized by rapid onset and high mortality rates. However, there are no preventive strategies developed for this pathogen and the current control measures are ineffective.
An analysis of farm-level risk factors for MAS outbreaks in farmed catfish in the southeastern U.S. showed that using salt (sodium chloride, NaCl) in catfish farms significantly decreased the incidence of vAh outbreaks. Therefore, the objectives of this study are to explore bacterial growth dynamics, morphological changes, survival, biofilm formation, and virulence of vAh grown in a standard culture medium but with different salt concentrations (0.5%, 1.5%, and 4.5% salt). Our preliminary data suggests a negative correlation between salinity and vAh growth. Moreover, biofilm formation was reduced at higher salinity conditions. Bacterial morphology and survivability were also assessed and the results will be presented. In vivo trials revealed that high salt concentration decreased the virulence of vAh. Overall, the results of our research show that high salt concentration negatively impacts vAh. This research provides a better understanding of how vAh survives in the aquatic environment and includes important information regarding the management of MAS outbreaks in catfish ponds.