Toxicity ability and median lethal dose in striped catfish of Aeromonas veronii

Abstract

Aeromonas veronii-related illnesses in aquatic animals have been studied recently, but no research on striped catfish has been documented. The current study was carried out to determine the toxicity and median lethal dose (LD₅₀) of A. veronii in striped catfish Pangasianodon hypophthalmus. Experimental fish (size of 15 – 20 g) were injected with bacterial solution after 20 hours of culture at 28^oC and diluted at a series of concentrations: 10⁸, 10⁷, 10⁶, 10⁵, 10⁴ CFU/mL (in triplicate). The fish injected with physiological saline water were used as a control batch. The results showed that, after 20 hours of bacterial culture, the bacterial density reached 1.1 ´ 10⁹ CFU/mL, the 50% lethal dose of A. veronii in common carp was 6.2 ´ 10⁷ CFU/mL. The skin, fins, and abdomen of the fish may bleed; the gallbladder and spleen may swell; there may be internal bleeding; and the intestine may swell and bleed. After bacterial infection, mortality was highest between 1 and 3 days; after day 4, no dead fish were discovered. Fresh microscopic examination of the bacteria using the results of bacterial re-isolation and tissue staining revealed that the bacteria were gram-negative bacilli with rounded, ivory-white colonies.