Isolation and identification of bacteria pathogens from Epinephelus coioides with tail-rotted disease

A very serious tail-rotted disease broken out in the cage-cultured Epinephelus coioides in Sanya city and Lingshui County,Hainan province,China in May 2008.Three strains of HS08001,HS08002,and XC08001 were isolated from the dis-eased grouper and were shown to be the pathogens by artificial infection.All the three isolates were identified as Vibrio har-veyi by biochemical tests and 16S rDNA sequence analysis.The LD50 value of strain HS08001 for E.coioides was 1.05×104 CFU/g body weight.Sensitivity test to 25 chemotherapeutic agents indicated that the pathogen was only highly sensitive to gentamicin,chloramphenicol,and rifampicin.