Antibiotic Resistance And Related Genes Of Lactic Acid Bacteria Isolated From Traditional Fermented Dairy Products

Ninety-three strains of Lactic acid bacteria (LAB), including L.casei, L.fermentrum, L.kefirgranum, L.helveticus, L.plantrum, L.delbrueckii, Lactococccus, Streptoccus, Enterococcus and Leuconostoc, which were isolated from traditional fermented dairy products were analyzed for antibiotic resistance, to detect the frequency of antibiotic strains, we determined the MIC of each strain. Seventeen related resistance genes were examined to make a correlation between genes and antibiotic resistance.The results revealed antibiotic resistance showed specificity over species, there is very little intra-specific and no region-specific. Most of the strains resistant to neomycin, polymyxin B, streptomycin, kanamycin, chloramphenicol and vancomycin; and susceptible to penicillin G, erythromycin and rifamipicin; the resistance to tetracycline, gentamicin and ciprofloxacin were varied of different species. Most Streptoccus thermophilus, Lactococcus and Entercoccus could tolerate neomycin, streptomycin and polymyxin B.According to PCR reaction, 17 related antibiotic resistant genes were detected in the test. It was found that the genes showed specificity in species and between different species. Pep1a, tetO, tetK and tetL genes were not detected in all the strains. GrA gene was detected in most strains; rdxA gene and parC gene were different in different species. FrxA,cat,rpoB,ermB,rpp,mefA and tetM gene were found in a few kinds of species; The frequency of bla,tetS and int was lowest in all species.We also investigated the correlation between resistance genes and antibiotic resistance. The results suggested that rpp, tetM, tetS and int gene may influence the resistance to tetracycline; rpoB gene may relate to rifampicin resistance; cat gene plays some role in the resistance to chloramphemciol; mefA and ermB can influence the resistance to erythromycin, bla gene may play some role on the resistance of lactam antibiotics. Strains harboring parC and gyrA gene can tolerate to kanamycin, streptomycin, and polymyxin B. Strains that harbored gyrA were resistant to vancomycin.These results may provide useful data for further studies on antibiotic resistance of LAB, the antibiotic resistance of LAB was an important factor to the safety assessment of probiotics.