Abstract: The bacteria were isolated from the intestine of Megalobrama amblycephala, the 4 strains were named MA1-4, respectively. Microscopic examination and bacterial culture results showed that 4 strains of bacteria were straight rod-shaped Gram-negative bacteria, which could grow on LB agar; based on physiological and biochemical characteristics of the strains, MA1 belonged to Edwardsiella ictaluri, MA2 belonged to Morganella morganii, MA3 belonged to Xenorhabdus nematophilua, and MA4 belonged to Shigella Flexneri. Further drug sensitivity test results revealed that the resistance rate were 52.2%, 69.6%, 95.7% and 100%, repectively,four strains were resistant to Azithromycin, Erythromycin, Lincomycin, Clindamycin, Metronidazole, Cefalotin, Vanguard ADM Ⅳ, Sulfamethoxazole and Methoxyl Carbazole, but the strains have different sensitivity to Rifampicin, Chloromycetin, Cefamandole, Cefoperazone, Piperacillin, Ampicillin , Gentamicin, Kanamycin, Tetracycline, etc. The results suggested that the intestine may be a natural reservoir for opportunistic pathogen in fish, thus provided a reference with the application of intestinal bacteria and prevention and control of fish diseases.

Key words: Megalobrama amblycepnala; intestinal bacteria; isolation and identification; drug sensitivity test