头孢西丁纸片扩散法检测耐甲氧西林葡萄球菌

Detection of methicillin-resistant staphylococcus with cefoxitin disk diffusion

目的 以PCR法检测葡萄球菌的mecA基因(mecA基因法)为标准,评价头孢西丁纸片扩散法、苯唑西林纸片扩散法和苯唑西林盐平板法检测葡萄球菌中耐甲氧西林葡萄球菌的灵敏度和特异性。方法 PCR扩增葡萄球菌的特异性mecA基因片段,头孢西丁纸片扩散法、苯唑西林纸片扩散法和苯唑西林盐平板法检测葡萄球菌中耐甲氧西林葡萄球菌,药敏试验方法按标准K B(Kirby Bauer)法进行。结果 在190株临床分离的葡萄球菌中金黄色葡萄球菌(金葡菌)138 株,表皮葡萄球菌30株,溶血葡萄球菌22株,经PCR法检测mecA基因,金葡菌中耐甲氧西林金葡菌(MRSA)和凝固酶阴性葡萄球菌中耐甲氧西林凝固酶阴性葡萄球菌(MRCNS)的发生率分别为81.2%(112/138)、96.1%(50/52)。头孢西丁纸片扩散法检测金葡菌中MRSA和CNS中MRCNS的发生率分别为81.2%(112/138)、94.2%(49/52),与mecA基因法结果相比较,头孢西丁纸片扩散法检测葡萄球菌中MRS的灵敏度和特异度分别为99.4%(161/162)、100.0%(28/28), 两者符合率为99.5%(189/190),2种方法所获得的结果经统计学处理,两者差异无显著性。结论 头孢西丁纸片扩散法检测耐甲氧西林葡萄球菌具有很高的灵敏度和特异度,适合在临床微生物实验室中进行推广。

Objective To evaluate the effectiveness of the cefoxitin disk diffusion method,oxacillin disk diffusion method and oxacillin salt agar method for detecting methicillin-resistant staphylococcus (MRS) using PCR amplification of mecA gene as reference.Methods mecA gene of staphylococcus was amplified by PCR.The susceptibility of staphylococcus strains to cefoxitin,oxacillin was tested by Kirby-Bauer method.Results Of the 190 Staphylococcal strains isolated from Huashan Hospital during February 2004-April 2004 (S.aureus 138,S.epidermidis 30 and S.hemolyticus 22),81.2% (112/138) were MRSA and 96.1% (50/52) were MRCNS confirmed by PCR amplification of mecA gene.Results obtained by cefoxitin disk diffusion method:81.2% (112/138) were MRSA and 94.2% (49/52) were MRCNS.The sensitivity and specificity of cefoxitin disk diffusion for the detection of MRS were 99.4% (161/162) and 100.0% (28/28) respectively.The results of cefoxitin disk diffusion and PCR method were consistent in 99.5% (189/190) of the isolates.Conclusions Cefoxitin disk diffusion method is highly sensitive and specific for the detection of methicillin-resistant staphylococcus.It is applicable in clinical microbiology laboratory.