葡萄球菌对大环内酯类抗生素耐药及诱导耐药表型与基因型的相关性研究

The correlation between phenotype and genotype of macrolides resistance in staphylococci

目的了解葡萄球菌对大环内酯类抗生素生物耐药表型与基因型的符合情况,分析耐药基因检出与生物耐药诱导的关系,并预测细菌耐药流行趋势,从基因水平指导临床合理用药。方法用KB纸片法检测本院2004～2005年分离的136株葡萄球菌对红霉素和克林霉素的耐药性,以聚合酶链反应(PCR)法检测葡萄球菌MsrA、vgb、Sat4、ermA、ermB、ermC、mphA、MefA/E、ereA、ereB 10种耐药基因,并将其耐药表型与基因型进行比较。将对红霉素表型敏感而耐药基因阳性的菌株进行诱导,对比诱导前后药敏结果。结果136株葡萄球菌对红霉素耐药的占80.88%,对红霉素和克林霉素同时耐药占43.38%,结果表明葡萄球菌对大环内酯类有较高的耐药率。耐药基因检测结果表明,共检出MsrA、Sat4、ermA、ermB、ermC、mphA、ereB 7种耐药基因,耐药基因检出率为83.82%。其中核糖体甲基化酶基因ermC的阳性率最高,占检测基因的67.54%;其次为Sat4、MsrA、ereB、ermA、ermB、mphA,分别占50.00%、28.95%、22.81%、15.80%、9.65%、1.75%。MRSA、MRCNS、MSSA、MSCNS菌株耐药基因的检出率分别为100.00%、90.78%、73.08%、55.55%。11株对红霉素敏感而耐药基因阳性的菌株经红霉素诱导后有9株转为耐药,诱导阳性率为81.82%。结论葡萄球菌对大环内酯类抗生素有较高的耐药性,在部分敏感株中检测出耐药基因,经诱导可产生耐药,提示菌株有潜在耐药性,需特别引起临床的重视。临床微生物实验室应同时开展表型及基因型检测,指导临床更加合理使用抗生素。

Objective To investigate the coincidence between the phenotype and genotype of macrolides resistance in staphylococci, analyze the relationship between resistance gene and induced resistance, forecast the bacterial resistance tendency, and to provide a reasonable drug use guide for clinic at gene level. Methods Disk diffusion method was used to test the erythromycin and clindamycin resistance phenotype of 136 isolates of staphylococci in our hospital from 2004 to 2005. Ten genes such as MsrA, vgb, Sat4, ermA, ermB, ermC, mphA, MefA/E, ereA and ereB were detected by applying polymerase chain reaction （PCR）, and the strains of negative phenotype and positive genotype were induced. Results 80.88% of staphylococcus isolates was resistant to erythromycin, and 43.38% was resistance to both erythromycin and clindamycin. The results showed that staphylococcus was highly resistant to macrolides. Seven genes were detected, i.e. MsrA, Sat4, ermA, ermB, ermC, mphA and ereB. The detection rate of resistance genes was 83.82%, in which erythromycin ribosome methylase gene ermC was the highest（67.54%）, followed by Sat4（50.00%）, MsrA（28.95%）, ereB （22.81%）, ermA（15. 80%）, ermB（9.65%） and mphA（1.75%）. The detection rate of resistance genes of MRSA, MRCNS, MSSA and MSCNS strains was 100.00%, 90.78%, 73.08% and 55.55% respectively. A total of 11 strains with resistance gene positive were sensitive to erythromycin,but after erythromycin induction, 9 strains （81.82%） became resistant to erythromycin. Conclusion Staphylococcus exhibits high resistance to macrolides. Drug resistance gene can be detected in some sensitive strains, indicating these strains may posses potential drug resistance. Therefore, the drug resistance of surveillance must be strengened, and we must emphasize on reasonable option of antimicrobial agents in clinical therapy in our area.