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Research Project: Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture

Location: Aquatic Animal Health Research

Title: Influence of kaolin clay on Aeromonas hydrophila growth, chemotaxis, and virulence to channel catfish, Ictalurus punctatus

Author
item Aksoy, Mediha
item Mohammed, Haitham - Auburn University
item Peatman, Eric - Auburn University
item Fuller, Adam
item Beck, Benjamin

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2018
Publication Date: 8/16/2018
Citation: Aksoy, M., Mohammed, H., Peatman, E., Fuller, S.A., Beck, B.H. 2018. Influence of kaolin clay on Aeromonas hydrophila growth, chemotaxis, and virulence to channel catfish, Ictalurus punctatus. North American Journal of Aquaculture. https://doi.org/10.1002/naaq.10059.
DOI: https://doi.org/10.1002/naaq.10059

Interpretive Summary: Aeromonas hydrophila is one of the most widespread bacterial pathogens affecting freshwater fish and a new strain of A. hydrophila has severely impacted the catfish industry over the last decade. In this study, we evaluated the effect of treatment with kaolin, an inert clay, for controlling A. hydrophila outbreaks. Tests revealed that kaolin clay significantly blocked the movement and binding ability of A. hydrophila to catfish mucus. Kaolin treatment at a level of 0.1% led to a significant improvement in survival (66.7%) of experimentally infected catfish as compared to untreated fish (28.9%). Kaolin treatment did not alter the growth of A. hydrophila, but bacterial concentrations in the upper phase of treated cultures were significantly reduced by kaolin treatment within 15 min, indicating the rapid formation of settleable complexes between kaolin and bacteria. These findings suggest that the integration of kaolin-based approaches into some production settings may be beneficial, particularly in scenarios where the large-scale use of antibiotics is not appropriate or advisable, or when it is likely that an Aeromonas outbreak is going to occur following stressors such as grading, stocking, or transport of fish.

Technical Abstract: Aeromonas hydrophila is one of the most widespread bacterial pathogens affecting freshwater fish and an emerging pathotype of A. hydrophila has severely impacted the catfish industry over the last decade. In this study, we evaluated the effect of treatment with kaolin (Al2Si2O5(OH)4), an inert clay, on the chemotaxis and adhesion (two important steps of the infective process) of A. hydrophila to catfish mucus and the potential use of kaolin for controlling A. hydrophila outbreaks. Chemotaxis assays revealed kaolin clay significantly blocked the chemotaxis and adherence of A. hydrophila to catfish mucus. Kaolin treatment at a level of 0.1% led to a significant improvement in survival (66.7%) of experimentally challenged catfish as compared to untreated fish (28.9%). Kaolin treatment did not alter the growth of A. hydrophila, but bacterial concentrations in the upper phase of treated cultures were significantly reduced by kaolin treatment within 15 min, and significantly increased in the pellet by 45 min of treatment, indicating the rapid formation of physical complexes through adsorption followed by gravitational settling.