动物源性链球菌红霉素耐药基因的分布

To investigate the mechanisms of erythromycin-resisant streptococcus isolated from animals,the minimal inhibitory concentrations(MICs) of pencillin, erythromycin and clindamycin against streptococcus were detected by agar two-fold dilution, the resistance phenotypes of erythromycin-resistant streptococcus were determined by the double disk test, and the presence of mefA, ermB genes were determined by PCR amplification. The results showed that the rate of resistance to penicillin, erythromycin and clindamycin of 111 strains studied were 54.95%,68.47%and 64.86%,respectively. In 76 erythromycin resistant strains, 62 isolates (81.58%) were assigned to the cMLS_B phenotype, 5 isolates (6.6%) were M phenotype and 9 isolates (11.84%) were inducibly resistant, expressing the iMLS_B phenotype by the double disk test. The mefA gene was present in all of the strains showing the M-resistance phenotype. Some isolates expressing a cMLS_B phenotype and iMLSB phenotype were confirmed genotypically by the presence of the ermB gene, but 6 isolates were n’t detected the ermB and mefA gene. Genes coding for both resistance mechanisms were found in one strain. No amplification was detected in all the erythromycin susceptible streptococcus isolates. Erythromycin resistant Streptococcus isolated from animals mediated by ermB was predominant in China. The PCR amplification can be a useful method to rapidly screen the erythromycin resistant strains.

儿童肺炎链球菌红霉素、四环素相关耐药基因的研究

目的：了解儿童肺炎链球菌（Streptococcus pneumoniae,SP）临床分离株红霉素、四环素耐药基因的流行状况及和耐药表型的关系。方法：对2005年1月-12月从温州附属育英儿童医院住院儿童分离到的47株肺炎链球菌进行了红霉素、四环素药敏试验,并用PCR法检测与红霉素耐药相关的红霉素核糖体甲基化酶基因（ermB）、主动外排转运基因（mefA）,与四环素耐药相关的tetM基因。结果：47株肺炎链球菌红霉素敏感3株、耐药44株;四环素敏感5株、耐药42株。3株红霉素敏感的肺炎链球菌均未检出ermB基因和mefA基因;44株红霉素耐药肺炎链球菌ermB基因和mefA基因的PCR检出率分别为81.8%和29.5%。共有39株肺炎链球菌检出ermB基因或/和mefA基因,其中单独携带ermB基因的耐药表型为29株,占74.4%;单独携带mefA基因的耐药表型2株,占5.1%;同时携带ermB基因和mefA基因的耐药表型8株,占20.5%。47株肺炎链球菌tetM基因的检出率为87.2%,其中四环素耐药组的检出率是95.2%,敏感组为25%。结论：ermB基因和mefA基因同时表达或单独表达均可导致红霉素耐药,ermB基因表达是儿童肺炎链球菌对红霉素耐药的主要原因,mefA基因表达是造成对红霉素耐药的次要原因。tetM基因是造成儿童肺炎链球菌四环素耐药的主要原因。红霉素和四环素已不是治疗肺炎链球菌的有效药物。肺炎链球菌四环素耐药尚存在其他的耐药机制。

肺炎链球菌红霉素相关耐药基因与耐药表型的关系

目的:了解肺炎链球菌(Streptococcuspneum oniae,SP)临床分离株红霉素耐药基因的流行状况及和耐药表型的关系。方法:对住院儿童分离到的43株肺炎链球菌进行红霉素药敏试验,并用PCR法检测与红霉素耐药相关的红霉素核糖体甲基化酶基因(ermB)、主动外排转运基因(mefA)。结果:43株肺炎链球菌红霉素药敏试验40株耐药(占93%),3株敏感。红霉素ermB基因总检出率为76.7%(33/43),mefA基因总检出率为23.3%(10/43)。3株红霉素敏感的肺炎链球菌均未检出ermB基因和mefA基因;40株红霉素耐药肺炎链球菌ermB基因和mefA基因的PCR检出率分别为82.5%(33/40)和25%(10/40)。共有35株肺炎链球菌检出ermB基因或/和mefA基因,其中单独携带ermB基因的耐药表型为25株(占71.4%);单独携带mefA基因的耐药表型2株(占5.7%);同时携带ermB基因和mefA基因的耐药表型8株(占22.9)%。结论:ermB基因和mefA基因同时表达或单独表达均可导致红霉素耐药,ermB基因表达是儿童肺炎链球菌对红霉素耐药的主要原因,mefA基因表达是造成对红霉素耐药的次要原因。红霉素已不是治疗肺炎链球菌的有效药物。

β溶血链球菌中诱导型克林霉素耐药的检测和分析

目的了解β溶血链球菌对红霉素及克林霉素的耐药性,探讨红霉素对克林霉素诱导耐药的表型和基因型。方法按CLSI推荐的K-B法测定并判读β溶血链球菌对红霉素及克林霉素的耐药性,用D试验检测红霉素诱导β溶血链球菌对克林霉素耐药的表型,并且用PCR方法确定所检测的菌株是否携带的ermB基因和mefA基因。结果49株红霉素耐药的β溶血链球菌结果显示有35株β溶血链球菌只扩增到ermB基因,有9株只扩增到mefA基因,有3株同时扩增到ermB和mefA基因,有2株没有扩增到ermB和或mefA基因;17株红霉素耐药克林霉素敏感菌株中D试验阳性8株细菌都只扩增到ermB,D试验阴性9株细菌中都只扩增到mefA;红霉素敏感的β溶血链球菌没有扩增到ermB或mefA基因。结论β溶血链球菌的耐药表型与基因型高度一致,临床上可用PCR方法和D试验检测,D试验检测更为简单方便,临床应该用D试验检测β溶血链球菌的iMLS型耐药。

利血平对化脓隐秘杆菌大环内酯类外排基因mefA表达的影响

化脓隐秘杆菌(Trueperella pyogenes,T.pyogenes)是一种能够引起动物和人化脓性感染的重要病原菌。随着抗生素的广泛使用,该菌已对临床常用的大环内酯类、四环素类等药物产生不同程度的耐药性。本试验拟探讨外排泵抑制剂利血平对T.pyogenes大环内酯类外排基因mefA mRNA及蛋白表达的影响,将为细菌外排泵抑制剂的研究奠定理论基础。以携带mefA基因的T.pyogenes分离株(17,20号)为试验菌株,采用荧光定量PCR及Western blot技术,检测利血平作用前后各菌株mefA基因mRNA及蛋白表达量。结果表明,1/2 MIC利血平作用2株耐药菌株36 h后,大环内酯类抗生素红霉素、罗红霉素、泰乐菌素、阿奇霉素和替米考星对携带mefA基因的T.pyogenes的MIC值均有不同程度的降低。17和20号分离株外排基因mefA mRNA表达水平较药物作用前均极显著降低(利血平作用前是作用后的5.18,17.54倍),外排蛋白MefA表达量较药物作用前也显著降低(利血平作用前是作用后的1.08,1.70倍),且基因水平和蛋白水平的变化与其耐药表型的变化趋势一致;提示利血平可能是通过抑制外排基因mefA的转录和翻译而消减T.pyogenes对大环内酯类抗生素的耐药性。