Lactococcus garvieae isolation, identification and determination of antibacterial sensitivity from cultured rainbow trout (Oncorhynchus mykiss, walbaum) in Eşen Stream

Lactococcus garvieae is one of the most important pathogen species commonly reported in freshwater and marine fish species from different geographical regions. In this study; Lactococcus garvieae fish pathogens were isolated from rainbow trouts in farms which located on Eşen Stream. They were identified by using phenotypic and genotypic methods and determined their antibacterial susceptibility using commercial antibiotic discs. For this purpose; the total 16 strains were isolated from 3 farms and identified by using conventional microbiological methods, API 20 STREP tests and molecular methods. To obtain the antibacterial susceptibility of the strains in total 32 antibiotic discs were used on the Muller Hilton Agar. The strains showed resistance against ampicillin, trimethoprim/ sulfomethoxazole, erythromycin, lincomycin, enrofloxacin, gentamicin, oxolinic acid, ciprofloxacin, kanamycin, colistin, ofloxacin, streptomycin, clindamycin, oxytetracycline, cefoperazone, flumecuin, tylosin, ceftriaxone, spectinomycin, cefoperazone, norfloxacin, cephalothin, oxacillin and apramycin, but sensitive to vancomycin, tetracycline, nitrofurantoin, chloramphenicol, doxycycline, penicillin, efuroxime, pristinamycin, amoxicillin. Among the antibiotic groups such as sulfanomides, macrolides, aminoglycosides were showed 100% resistance, in quinolone groups other than nitrofurantoin displayed resistant, in β-lactam group antibiotics obtained as resistance except penicillin, cefuroxime, amoxicillin, also in tetracycline groups; oxytetracycline showed resistance and in other groups; while colistin was presented resistance, amphenicols was showed sensitivity on the all strains. The results of the study revealed that the biosecurity measurements should be taken to prevent the spread of bacterial pathogens and antimicrobial resistance and also microbiological monitoring is very important issues in rainbow trout farms. Also this study emphasized that the antibiogram tests should be applied onto isolated fish pathogens before the treatment and the importance of using of antibiotics under control one more time.