Abstract:

Comparison of extracellular products (ECP) from a variety of Aeromonas hydrophila isolated from fish, with LD50 values between 2.3 x105 and 3.5 x108 CFU ml-1, was conducted using SDS-polyacrylamide gel electrophoresis. Differences were observed in the silver stain profiles of the ECP preparations, while the total amount of protein obtained from each isolate were very similar (0.14-0.15 mgml-1). Levels of toxicity for the different ECP preparations were determined through intraperitoneal injection (0.2 mgml-1) of fingerling hybrid catfish (Clarias gariepinus x Clarias macrosephalus). The ECP preparation from the high virulence isolates produced 100% mortality in all fish within 18 h of injection, while the ECP from the low virulence isolates produced 100% mortalities after 96 h. The cytolytic enterotoxin was partially purified by chromatography, and this was then used to immune a rabbit and a catfish. Antibody titres of 1/1,024 and 1/32,768 were obtained through an indirect enzyme linked immunosorbent assay, for the catfish and rabbit sera, respectively. Purified enterotoxin from bacteria with LD50 values around 105 CFU ml-1 contained a strong band at 52 kDa, while one of the avirulent isolates with an LD50 value around 108 CFU ml-1 contained a strong band at 45 kDa. The 52 kDa molecule was identified only by the catfish serum in the enterotoxin prepared from virulent isolates of A. hydrophila.

Full text PDF

Date 1999/12/01

Abstract Hits 2984

Downloads 2020