Abstract

A pthogenic bacterium Stenotrophomonas maltophilia was isolated from channel catfish (Ictalunes punctatus). We studied the pathogenicity of the extracellular protease (ECPase) of S.maltophilia. The extracellular protease was purified by 70% ammonium sulfate fractionation and DEAE-Sephadex A 50 and injected intraperitoneally to mice. The pathological changes of injected mice were observed. The injected mice showed different lethal rate and their typical symptoms include the demonstration of tachypnea and downcast, with mucous stool on their anuses. The tested animals showed visible lesions in livers, spleens, stomachs and intestines. They had serious gastroenteritis and flatulence. Mural stomach and intestines became thin with pallide-flavens mucus. The spleen was tumescent and hemorrhaging. The hepar was seriously tumid and had necrotic regions. The color of the kidney became light and the lung had no obvious change. The LD₅₀ of the ECPase was 4.33 ug/g.

Key words: Stenotrophomonas maltophilia, extracellular protease, pathology, mice, channel catfish (Ictalunes punctatus)