肺炎链球菌对大环内酯类抗生素耐药机制研究

目的了解肺炎链球菌对大环内酯类抗生素的耐药机制和转座子整合酶的流行情况。方法188株红霉素耐药肺炎链球菌，用E试验和K—B纸片扩散法检测其对11种抗菌药物的敏感性；用双纸片法（红霉素和克林霉素）确定其耐药表型；用PCR扩增这些菌株的耐药基因ermB、mefa、mefE、tetM及转座子整合酶基因intTn。结果188株红霉素耐药株中耐药基因ermB总检出率为91．5％（172／188），mefE总检出率为38．3％，未检出mefA基因。97．9Yoo的红霉素耐药株中存在转座子整合酶intTn。耐药基因组合ermB（＋）mefE（-）和ermB（＋）mef（＋），占91．5％，两者均呈cMLSB耐药表型。ermB（-）mefE（＋）占8．5％，耐药表型为M型。结论我院分离的肺炎链球菌大环内酯耐药以errnB介导的cMLS。耐药表型为主。转座子可能在本地区肺炎链球菌耐药基因的水平转移和克隆播散中起重要作用。

Study on the mechanism of macrolide resistance in Streptococcus pneumoniae

Objective To investigate the mechanism of macrolide resistance and the prevalence of transposon in Streptococcus pneumoniae isolates.Methods Antibiotic susceptibility was determined by E-test or K-B disk diffusion method for 188 erythromycin-resistant S. pneumoniae isolates. Macrolide resistant phenotypes were identified using double disc test with erythromycin and clindamycin discs. The ermB, mefA, mefE, tetM and intTn genes were amplified by PCR.Results Of the 188 erythromycin-resistant isolates, 94.1% were resistant to clindamycin and 72.7% were penicillin non-susceptible S. pneumoniae (PNSSP). Amoxicillin-clavulanic acid and levofloxacin were still active against most of the isolates. The prevalence of resistant genes was: ermB, 91.5%; mefE, 38.3%; mefA 0%; transposon integrase gene (intTn) 94.5%. The most common macrolide-resistant phenotype was cMLSB (91.5%), which had ermB( )mefE( ) and ermB( )mefE(-) genotypes. About 8.5% was M phenotype, which had ermB(-)mefE( ) pattern. Conclusions The ermB-mediated cMLSB is the most prevalent phenotype among erythromycin-resistant S. pneumoniae isolates. Transposon may play an important role in resistance spread both horizontally and clonally.