耐甲氧西林金葡菌的头孢西丁检测法与耐药性分析

Detection of methicillin-resistant Staphylococcus aureus by cefoxitin agar diffusion and their drug resistance analysis

目的评价头孢西丁纸片扩散法检测耐甲氧西林金葡菌(M RSA)的效果,了解M RSA的耐药状况。方法用头孢西丁及苯唑西林纸片扩散法、m ecA基因聚合酶链反应(PCR)检测M RSA,并以m ecA基因PCR法为参考方法与头孢西丁及苯唑西林纸片扩散法检测M RSA进行比较分析。按CLS I(原NCCLS)规定的标准测定M RSA对青霉素等10种抗生素的耐药率(KB法)。结果95株金葡菌(SA)中m ecA基因阳性株42株。头孢西丁纸片法筛选出40株M RSA,其中39株m ecA基因阳性,方法特异性为97.5%,灵敏度92.9%;苯唑西林纸片法筛选出44株M RSA,其中36株m ecA基因阳性,方法特异性为81.8%,灵敏度85.7%。M RSA对青霉素、苯唑西林100%耐药,对万古霉素全部敏感,对红霉素、头孢唑林、克林霉素、氨苄西林/舒巴坦、头孢呋辛、左氧氟沙星、奈替米星呈不同程度耐药。结论头孢西丁纸片扩散法检测M RSA特异性和灵敏度优于苯唑西林纸片扩散法。M RSA具有多重耐药性,须加强其对抗生素的耐药性监测。

Objective To evaluate the efficiency of cefoxitin agar diffusion method for the detection of methicillin-resistant Staphylococcus aureus （MRSA） and analyze their drug resistance. Methods The detection of MRSA was performed by cefoxitin agar diffusion and oxacillin agar diffusion. The method was com- pared with mecA gene amplification with polymerase chain reaction （PCR） which was used as a control method. The drug resistance rates of MRSA to 10 antibiotics were analyzed by Kirby-Bauer agar diffusion method recommended by CLSI （formerly NCC[.S）. Result There were 42 mecA-positive strains in 95 Staphylococcus aureus isolates. Forty isolates of MRSA were detected by cefoxitin agar diffusion, in which 39 strains had mecA gene. The specificity and sensitivity of the method was 97.5% and 92.9%. Forty-four isolates of MRSA were detected by oxacillin agar diffusion, in which 36 strains had mecA gene. The specificity and sensitivity of the method was 81.8% and 85.7~. The MRSA isolates were susceptible to vancomycin, partially resistant to erythromycin, cefazolin, clindamycin, ampicillin/sulbactam, cefuroxine, levofloxacin and netilmicin, and resistant to penicillin and oxacillin. Conclusion The sensitivity and specificity of cefoxitin agar diffusion were better than those of oxacillin agar diffusion. The multidrug resistance of MRSA is common, and the surveillance of resistance should be paid more attention.