Evaluation of antibiotic resistance among isolated pathogenic bacteria from shrimp hatcheries in Bushehr province

Rapid development of shrimp aquaculture has resulted in widespread use of antibiotics for preventing and curing diseases. In aquaculture، particularly shrimp hatcheries antibiotics are routinely used at therapeutic levels to treat disease and at sub-therapeutic levels as prophylactic agents to increase feed efficiency. Antibiotic residues in the environment are likely to lead to the development and maintenance of antibiotic resistance in microbial populations. The aim of this study was determine of antibiotic resistance to two shrimp pathogens Vibrio harveyi، V. alginolyticus، that they are agents of mortality in shrimp hatcheries. After isolation and detection (by biochemical tests) of two species of bacterial pathogens from three hatcheries of Bushehr province، bacterial strains were tested for sensitivity to antibiotics including erythromycin، streptomycin، oxytetracyclin، and trimetoprim by disk diffusion method. Results showed that all isolated bacteria Vibrio harveyi from three hatcheries were sensitive to oxytetracyclin and trimetoprim، but to streptomycin were resistant، and to erythromycin in hatcheries A، B، C was intermediate، resistance، sensitive respectively. Bacteria Vibrio alginolyticus isolated from three hatcheries were resistant to streptomycin. But they isolated from a hatchery to the other antibiotics erythromycin، oxytetracyclin and trimetoprim were resistant، intermediate and intermediate، respectively. Also they isolated from B hatchery were resistant، sensitive and sensitive to erythromycin، oxytetracyclin and trimetoprim، respectively And from C hatchery were intermediate، sensitive and sensitive to antibiotics، respectively. Isolated bacteria showed the most resistance to streptomycin and erythromycin respectively. These antibiotics is used frequently in medicine and veterinary، with entrance of human and animal''s bacteria resistance via waste and fluid water to the sea، maybe transferred the resistant plasmid from resistant bacteria to Vibrio spp.