耐红霉素肺炎链球菌的分子生物学研究

目的研究耐红霉素肺炎链球菌的分子生物学特点。方法社区获得性肺炎呼吸道标本分离的肺炎链球菌共45株,进行抗生素药物敏感性试验,对耐药菌株采用PCR方法检测红霉素的耐药基因ermA/ermB/mefA,同时采用脉冲场凝胶电泳技术和青霉素结合蛋白基因多态性追踪耐药菌株之间的同源性,以获得耐药菌株的分子流行病学特点。结果45株肺炎链球菌中对红霉素耐药24株,均为多耐药肺炎链球菌;青霉素耐药14株,其中11株（78.6%）同时耐红霉素。22株（92%）的红霉素耐药株为MLS表型,即同时耐克林霉素,2株为M型耐药。经PCR扩增,20株（83.3%）具有ermA/B基因,6株（25.0%）同时有erm和mef基因,2株（8.3%）只有mef基因,2株未能检测到erm或mef基因。脉冲场凝胶电泳和青霉素结合蛋白基因多态性检测未发现不同地区相同的耐药克隆株。结论erm基因编码的核糖体突变是肺炎链球菌耐红霉素的主要机制,本研究未发现不同地区相同的耐药克隆株。

Research on the molecular biology of erythromycin-resistant Streptococcus pneumonia

Objective To explore the molecular biological characteristics of erythromycin-resistant Streptococcus pneumoniae. Methods An antibiotics sensitivity test was performed on 45 strains of S. pneumoniae isolated from respiratory specimens of community-acquired pneumonia. PCR was used to identify erythromycin-resistant genes ermA/ermB/mefA in drug-resistant strains. Pulse field gel electrophoresis （PFGE） was used and penicillin-binding protein gene polymorphism （with PCR-RFLP） was tested to trace the homology and thus the molecular epidemiological characteristics of drugresistant strains. Results Among 45 strains of S. pneumoniae, there were 24 erythromycin-resistant strains and they were all multidrug resistant. Fourteen were penicillin-resistant, including 11 which were erythromycin-resistant （78.6 ~ ）; 22 （92 ~） erythromycln-resistant strains had an MLS phenotype （clindamycin-resistant） and 2 strains had Mtype resistance. PCR amplification showed that 20 strains （83.3%） had ermA/B genes, 6 strains （25%） had both erm and mef genes, 2 strains （8.3%） had only mef genes, and 2 strains had no erm or mef genes. Pulse field gel electrophoresis and penicillin binding protein gene polymorphism did not indicate the same drug-resistant strains of clones in different regions. Conclusion The ribosomal mutation of erm-encoding genes is the main mechanism of erythromycin-resistanee in S. pneumoniae; the same drug-resistant strains of clones in different regions were not identified by this study.