Recovery of Pseudomonas aeruginosa from Diseased Grass carp (Ctenopharyngodon idella) in China

An epizootic was discovered in grass carp (Ctenopharyngodon idellus) in earthen ponds in Ninghe, Tianjin Province, northern China, from May to June 2013. The cumulative mortality was 30% within 25 days, and the diseased fish presented with hemorrhaging in the abdominal wall, ascites in the abdomen and pale liver. Strains named PA131207 and PA131208 were isolated from the moribund fish, and were identified as Pseudomonas aeruginosa according to both biochemical tests and phylogenetic analysis derived from the 16S rRNA gene. The pathogenicity of PA131207 was confirmed by infectivity experiments and histopathological examination. Antimicrobial susceptibility tests showed that PA131207 was resistant to 9 of 15 antimicrobial agents tested.