Sensitivity of antibiotics against Lactococcus garvieae isolated from rainbow trout farms in Chahrmehal va Bakhtiari Province.

Objectives: In the present study antibiotic sensitivity of Lactococcus garvieae isolated from rainbow trout was evaluated. This bacterium is the aetiological agent of lactococcosis, an emergent disease, which affects cultured freshwater with special incidence in rainbow trout in Chahrmehal va Bakhtiari Province, Iran. Although L. garvieae is a pathogen of economic importance, data pertaining to pathogenesis of disease, control and treatment of disease were not known well. Materials Methods: L. garvieae strains were isolated from fish tissues such as kidney and spleen from different farms in Chahrmehal va Bakhtiari Province. After culturing the bacteria, they were identified by biochemical tests and PCR. The isolated bacteria were seeded in Mueller-Hinton agar. Commercially available disks the following antibiotics were used: nalidixic acid, erythromycin, bacitracin, methicilin, cloxacilin, penicillin, ampicillin, kanamycin, amikasin, cefepime, florfenicol and enrofloxacin. Results Conclusion: Among the all antibiotics, it seems that the most effective antibiotics were enrofloxacin, erythromycin and florfenicol and respectively, bacitracin, methicilin, penicillin, kanamycin, amikasin and cefepime were after that. Antibiotic resistance surveillance programs are necessary to monitor the susceptibility of bacteria to commonly used antibiotics. Such information is important to discover the development of resistance and the choice of appropriate antibiotics. The results of the present study provide useful information in the search for safe and efficient antibiotics. Our findings also showed a high rate of antibiotic resistance among the strains of the aetiological agent of lactococcosis that can be transferred to other bacteria such as aetiological agent of Streptococcosis in fish farms. Further studies are necessary in order to confirm the effectiveness of these antibiotics in farm using (in vivo situation).