Occurrence of atypical aeromonas salmonicida in mandarin fish (ssogari: Korean name) siniperca scherzeri

Abstract

Mandarin fish (SSOGARI: Korean name) has emerged as new aquaculture and aquarium fish among Korean native fish species. Unfortunately, this fish could not exempt from infectious agent invasion. As an epidemiological survey, high mortality of mandarin fish (Siniperca scherzeri) observed from a fish farm in Gyeongnam province of South Korea. The major macroscopic sign of the diseased fish was severe multifocal dermal ulceration. Histological observation revealed inflammation, necrosis and colonization of bacteria in various tissues. Seven bacterial isolates from the diseased fish were identified as Aeromonas salmonicida subsp. salmonicida (typical A. salmonicida) using API 20E and 20NE system. However, the polymerase chain reaction (PCR) assay using two different primers (AP and MIY) revealed that the bacterial strains were not typical A. salmonicida, but atypical A. salmonicida. This study demonstrates that PCR assay is a reliable method for the confirmation of atypical A. salmonicida in mandarin fish as compared to biochemical tests. Furthermore, this is the first account of extensive dermatitis in mandarin fish due to atypical A. salmonicida infection, which has high potential in aquaculture and aquarium fish among native fish species.