牛源肠球菌耐药基因与表型关系及16S rDNA同源性分析

Phenotype and genotype of bovine Enterococci antimicrobial properties and its 16S rDNA homology

为探究牛源肠球菌耐药性基因型与表现型之间的关系,采用微量肉汤稀释法分析62株肠球菌对7种抗生素的耐药表型,采用PCR技术检测相关的抗药基因,并分析62株肠球菌16SrDNA的同源性。结果显示,98.4%,98.4%,63.9%,6.5%,6.5%的菌株分别对万古霉素、红霉素、四环素、氯霉素和庆大霉素不敏感,100.0%菌株对卡那霉素敏感。100.0%的菌株均携带aphA3、aadA、aadE和aac6aph2基因;98.4%,98.4%,98.4%,95.2%,88.7%,72.6%,3.2%的菌株分别携带ermB、tet(M)、tet(O)、aac、mefA、vanB和vanA基因。62株肠球菌中均未检测出catpIP基因。结果表明,红霉素的耐药性(98.4%)与ermB(98.4%)基因呈正相关,与mefA(88.7%)的相关性也较好。氯霉素的耐药表型(6.5%)与catpIP(0)基因的相关性较好,万古霉素耐药表型(98.4%)与vanB(73.6%)基因相关性较好,其他耐药表型与检测的基因无明显相关性。16SrDNA分析表明,62株肠球菌按同源性可分为A、B、C、D、E、F这6种类型,其中E型与致病株EU717958的同源性较近,F型与致病株EU717964的同源性较近。

All isolates（62）were tested for susceptibility to 7different antimicrobial agents using broth micro-dilution method,and the presence of genes encoding these properties was tested.Furthermore,16 SrDNA of all isolates were screened and sequenced for molecular characterization.All isolates were susceptible to kanamycin,93.5%（58/62）for ciprofloxacin,gentamicin and chloramphenicol,37.1%（23/62）for tetracycline,1.6%（1/62）for erythromycin and vancomycin,respectively.All isolates were positive for aphA3,aadA,aadE,and aac6-aph2,followed by ermB（98.4%）,tet（M）（98.4%）,tet（O）（98.4%）,aac（95.2%）,mefA（88.7%）,vanB（72.6%）,and vanA（3.2%）,respectively.However,catpIPgene was not found in the 62 isolates.Furthermore,phenotype of erythromycin-resistant was positively correlated with ermB（98.4%）and mefA（88.7%）.Phenotype of chloramphenicol-resistant（6.5%）was well correlated with catpIP（0）,and the phenotype of vancomycin-resistant（98.4%）was well correlated with vanB（73.6%）gene.While other genes have no obvious correlations between their genotype and phenotype.All 62 isolates were divided into 6clusters,including A,B,C,D,E and F clusters.The homology of cluster E was closed to EU717958,and the homology of cluster F was closed to EU717964.