Characterization and Pathology of Aeromonas veronii Biovar Sobria from Diseased Sheatfish Silurus glanis in China

Aeromonas spp., is an important opportunistic pathogen responsible for great economic losses in aquaculture. In this paper, we report our study of an Aeromonas infection that occurred in cultured sheatfish Silurus glanis in May 2016 in a farm in Tianjin city. Typical external symptoms included petechial skin hemorrhages, ascitic distension of the abdomen, redness and swelling of the anus. The isolate SAV-165 from the diseased fish was identified as A. veronii biovar sobria by biochemical properties and molecular techniques. Experimental challenge showed that a 50% lethal dose (LD50) of SAV-165 was 1.59 × 106 CFU/ml in zebrafish Danio rerio. The antimicrobial susceptibility test indicated that the isolate was susceptible to aminoglycosides and chloramphenicol, but resistant to penicillins and sulphonamides. Histopathological examination showed fatty changes and swelling of hepatocytes in the liver, congestion in the submucosa of intestine and the renal veins of the kidney. This is the first report of A. veronii biovar sobria infection in S. glanis in China.