0px; "> A study was conducted to investigate the pathogenicity and the median lethal dose (LD50) of Aeromonas hydrophila isolated from clinically diseased catfish against apparently healthy homologous fish to evaluate the lethality of extra-cellular products (ECPs) of the isolated strain in vivo. For pathogenicity experiment, five different concentrations of Aeromonas hydrophila strain BNS 01614 including 3× 108, 1.5 × 108, 1.5 × 107, 1.5 × 106 and 1.5 × 105 CFU/fish used via intra peritoneal. The results revealed that pathogenicity of BNS 01614 was confirmed by the mortality of 30 % to 100 % of all tested fish within 4 to 12 days with LD50 1.5 × 107 CFU/fish. The Concentrated extracellular products (ECPs) of the selected bacterium were prepared and confirmed to be toxic in Clarias garipineus with LC50 of 20µg.