Influence of Kaolin Clay on Aeromonas hydrophila Growth, Chemotaxis, and Virulence to Channel Catfish

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 A. hydrophila chemotaxis and adhesion (two important steps of the infective process) to catfish mucus and the potential use of kaolin for controlling A. hydrophila outbreaks. Chemotaxis assays revealed that 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 Channel Catfish Ictalurus punctatus 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 were significantly increased in the pellet by 45 min of treatment, indicating the rapid formation of physical complexes through adsorption followed by gravitational settling.

The Use of Kaolin as a Prophylactic Treatment to Prevent Columnaris Disease (Flavobacterium covae) in Commercial Baitfish and Sportfish Species

“…They concluded that kaolin could reduce gill pathologies and bacterial attachment to key tissues and increase survival in Channel Catfish exposed to F. covae . Kaolin has also been proven to be effective in blocking chemotaxis and adherence of Aeromonas hydrophila in the mucus of Channel Catfish [ 39 ]. Kaolin treatment at a rate of 0.1% increased survival ( p < 0.05) compared to control (untreated) Channel Catfish in the same study [ 39 ].…”

“…Kaolin has also been proven to be effective in blocking chemotaxis and adherence of Aeromonas hydrophila in the mucus of Channel Catfish [ 39 ]. Kaolin treatment at a rate of 0.1% increased survival ( p < 0.05) compared to control (untreated) Channel Catfish in the same study [ 39 ].…”