This study was conducted in a freshwater tilapia farm that has not used any antibiotic. It was selected one pond, caught 15 fishes and collected samples of intestinal content and mucus surface, water influent and pond water, ration, fresh tilapia fillets and frozen fillets.. Phenotypical characteristics, Gram stain, oxidase production, oxidative-fermentative utilization of glucose (O-F) were determined of representative colony. Were selected 89 strains and submitted for antimicrobial sensitivy test using several antibiotics. The major identified bacterial families were belonged Enterobacteriaceae and Vibrionaceae. The most isolates showed resistance to ampicilin and eritromicin. From the 89 isolates evaluated 74 (83%) showed a multiple antibiotic resistance index (MAR) ³ 0.2, that mean resistance to two or more antibiotics. The MAR índice frequency were higher and bigger in the rations.
Bactéria; antibiotic resistance; Nile tilapia
