肺炎链球菌对大环内酯类的耐药机制研究

目的 探讨台州医院肺炎链球菌临床分离株的耐药性及对红霉素的耐药机制,为临床用药提供依据.方法 收集临床分离的肺炎链球菌31株,运用K-B纸片法及VITEK细菌鉴定仪检测其对抗菌药物的药敏谱；通过纸片法筛选对大环内酯类抗菌药物(红霉素)的耐药表型,PCR扩增红霉素耐药基因:ermB、mefA,并送测序鉴定.结果 K-B法纸片药敏结果显示,肺炎链球菌临床分离株主要对红霉素、磺胺甲噁唑/甲氧苄啶和四环素耐药,耐药率分别为:100.0％、64.5％、32.2％;未发现有对青霉素、万古霉素及替考拉宁耐药的菌株；31株肺炎链球菌临床分离株耐药表型均为组成型耐药；31株红霉素耐药菌株的基因均为ermB(+)/mefA(+),测序结果正确.结论 台州医院肺炎链球菌临床分离株对红霉素耐药率高,erm基因介导的靶修饰作用和mef基因介导的外排泵机制的共同作用,是主要的耐药机制.

Study on mechanism of macrolide resistance in Streptococcus pneumoniae

OBJECTIVE To investigate the antimicrobial susceptibility of Streptococcus pneumoniae isolated in Taizhou Hospital and their mechanisms of resistance to erythromycin so as to guide the rational use of drug in clinic.METHODS Antimicrobial susceptibility of 31 strains of S.pneumoniae was determined by KB disk diffusion method and VITEK identification system.Phenotypes of macrolide-resistant S.pneumoniae were determined using double disk test with erythromycin.ermB,mefA genes were amplified by PCR and sent for sequencing.RESULTS The antimicrobial susceptibility results showed that of the 31 S.pneumoniae isolates,the resistance rates to erythromycin,sulfamethoxazole,and tetracycline were 100.0%,64.5%,32.2%,respectively.No strain was resistant to penicillin,vancomycin and teicoplanin.31 clinical isolates were of the constitutive resistance phenotype.All erythromycin-resistant isolates had ermB(+)/mefA(+) genes.CONCLUSION The resistance of S.pneumoniae to erythromycin is serious in Taizhou Hospital.Target modification by erm methylase and gene modification by mef efflux pump are the main mechanism of macrolide-resistance in S.pneumoniae isolates.