Abstract: In this study, SS agar was used for selective isolation of bacteria from the intestine of carp (Cyprinus carpio) (body weight 0.5 to 0.6 kg) sold in the open-air market of Jiangsu province. One hundred and seven strains of bacteria were gained, of which two typical strains were named CS-1 and CS-2, respectively. The results of the physiobiochemical characteristics and the antimicrobial susceptibility assay showed that they were all Gram staining negative and small rod-shaped bacteria, and produce acids and gas by using glucose, MR test were positive, oxidase and VP test were negative. The motility test and H₂S were positive, and indole was negative for CS-1 strain, while CS-2 strain were reversed. Preliminary identification of the strains of bacteria, CS-1 and CS-2 belong to Salmonellas and Shigella species, respectively. Further drug sensitivity test results revealed that two strains were highly sensitive to cefoperazone, cephalexin Ⅳ, cefamandole, cephalothin, nitrofurantoin and piperacillin, but they were resistant to clindamycin, lincomycin, metronidazole, rifampin, erythromycin. This study may provide a scientific reference in the aquatic food safety and quarantine inspection, and treatment of diseases in fish.

Key words: carp; Salmonellas; Shigella; isolation and identification; drug sensitivity test