The first isolation and identification of Staphylococcus aureus from Siberian sturgeon (Acipenser baeri) cultured in Iran

This study was done after report of some mortality in one Sturgeon fish farm (Acipenser baeri) in Sari (north of Iran) during June- July 2011. Sampling was done on 20 fish and waters from selective farm for detection and identification of its agent. After recording the clinical observation, necropsy, bacterial cultures, biochemical analysis and molecular survey (PCR) was done to identify the genus and species of bacteria. The results showed clinical signs including: lethargy, reduce of appetite, motionless, up-down swimming, also, in necropsy symptoms such as hyperemia and hemorrhage in external and internal organs, petechial hemorrhage and congestion in the liver, spleen and gills was observed. After culture, biochemical tests and by molecular study on 20 gram-positive isolates, 18 isolates were identified as Staphylococcus aureus that had the expected 270 bp fragment. Antibiotic susceptibility testing on isolates showed more sensitivity to Florfenicel. The following, after taking 10 mg per kilogram of the drug orally for 14 days, mortality completely stop and disease was control. The results indicate the occurrence of a severe toxemia in Siberian sturgeon have been caused by S. aureus. According to our knowledge, this is first report of isolation and identification of S. areuse from A. baeri.