Detection of antibiotic resistance genes in some Lactococcus garvieae strains isolated from infected rainbow trout

The present study was done to evaluate the presence of antibiotic resistance genes in Lactococcus garvieae isolated from cultured rainbow trout, West Iran. The isolates were examined for antimicrobial resistance using disc diffusion method. Of the 24 strains tested, 21 were resistant to ampicillin (87.5%), 9 to erythromycin (37.5%) and 19 to tetracycline (79.1%). Fourteen strains were resistant to four antibiotics, 8 resistant to five antibiotics and 2 to six antibiotics. The strains were also characterized for their genotypic resistance profiles. The results revealed that all 24 isolates contained one to three of the antibiotic resistance genes. StrA, tetS and ermB genes coding for streptomycin, tetracycline and erythromycin resistance were found in 7, 10 and 9 isolates, respectively and sulfamethoxazole resistance gene, sul2, was not detected in the examined isolates. High levels of antibiotic resistance and detection of resistance genes in L. garvieae strains should be considered as a potential danger for trout culture as well as for public health.