| Lactic acid bacteria As a kind of probiotic are widely used in food fermentation and theyalso widely exist in human and animal gastrointestinal environment. In recent years, substantialstudies indicated that there are many drug-resistant strains of lactic acid bacteria in which somespecies own multiple drug resistance. Considering that lactic acid bacteria are widespread and areclosely related to people’s life, it is of a high possibility that probiotic tends to be a drug-resistantgene carrier. This may brings irrevocably catastrophic effects on public healthy when lactic acidbacteria spread a lot of resistance genes to pathogenic bacteria and then they are integrated inpathogenic bacteria, these phenomenon will make a large range of antibiotics useless. In thispaper, lactic acid bacteria were isolated from yoghourt sold in Guangzhou. Then theirsusceptibility of the stains to19antibiotics, relevant resistance mechanism as well as horizontaltransmission capacity is explored.48strains (20strains of L.delbrueckii,3strains of L.paracasei and25S.thermophilus) oflactic acid bacteria were isolated from41samples of yoghourt in Guangzhou through the mediumof the selective culture, gram staining microscopy and biochemical identification in this study.K-B method was used to acquire the information of susceptibility of these stains to19antibiotics. All of the strains tested are shown to be susceptible to ampicillin/sulbactam,doxycycline,c0eftazidime, cefotaxime, erythromycin and rifampicin. In addition, they showrelatively high resistance to kanamycin, streptomycin, sulfamethoxazole and gentamicin (100%,95.83%,81.25%and95.83%respectively); as a comparision, they indicate lower resistance tociprofloxacin, trimethoprim/sulfamethoxazole and vancomycin (45.83%,41.67%and35.42%respectively). These strains are sensitive or moderate sensitive to tetracycline, ampicillin,imipenem, penicillin, cephalothin and chloramphenicol antibiotics. Multiple drug-resistant strainsof lactic acid bacteria is significant in this study, more than50%of the strains are able to resistant5-8kinds of antibiotics.PCR amplification techniques were used to detect resistance genes of these drug-resistantstrains of lactic acid bacteria. The results show that3in4tetracycline resistant strains containing tetracycline resistance genes tetM with the detection rate of75%;13in38strains ofsulfamethoxazole drug-resistant species are detected to contain sulI resistant gene, in addition,one the stains is indicated to own sulII drug-resistant genes at the same time with the detectionrate of34.2%and2.63%respectively.According to the research of S4thermophilic streptococcus in which sulfanilamide resistancegene sulI are detected by PCR amplification. And this gene can horizontally transferred to E. coliDH5α by chemical conversion, this makes the E. coli DH5α resistant to sulfamethoxazole. |
