四种初筛试验检测耐甲氧西林葡萄球菌的评价

Evaluation of Four Screening Methods for Methicillin-Resistant Staphylococcus

目的评价四种初筛试验检测耐甲氧西林葡萄球菌(MRS)的价值。方法收集临床分离金黄色葡萄球菌100株、凝固酶阴性葡萄球菌51株,分别进行头孢西丁纸片、MHA中添加4%NaCl的头孢西丁纸片、MHA中添加2%NaCl的苯唑西林纸片、苯唑西林-盐琼脂,以PBP2a胶乳凝集作为MRS检测标准,按CLSI2006版标准操作和判读结果。结果对于金黄色葡萄球菌,头孢西丁纸片、MHA中添加4%NaCl的头孢西丁纸片、MHA中添加2%NaCl的苯唑西林纸片、苯唑西林-盐琼脂检测MRS灵敏度和特异性分别为96.3%和100.0%、85.2%和100.0%、77.8%和100.0%、92.6%和94.5%,其中2株苯唑西林-盐琼脂24h未生长但延长至48h生长,48h内敏感性100.0%;对于凝固酶阴性葡萄球菌,四种方法检测MRS灵敏度和特异性分别为97.8%和80.0%、95.6%和80.0%、95.6%和80.0%、100.0%和80.0%(P>0.05)。结论四种方法均能可靠检测MRS,头孢西丁纸片和苯唑西林-盐琼脂具有较高应用价值。

Objective To evaluate the clinical values of four screening methods for methicillin-resistant Staphylococcus （MRS）. Method According to CLSI 2006 standard, 100 strains of Staphylococcus aureus （SA） and 51 strains of coagulase-negative Staphylococcus （CONS） isolated from clinical samples were tested by cefoxitin disk diffusion method, cefoxitin disk diffusion supplemented with 4% salt inmueller-hinton agar （MHA）, oxacillin disk diffusion supplemented with 2% salt in MHA, and oxacillin-salt agar. The results were compared with the gold standard （penicillin binding protein 2a （PBP2a） latex agglutination test. Result The sensitivity and specificity of cefoxitin disk, cefoxitin disk supplemented with 4% salt in MHA, oxacillin disk supplemented with 2% salt in MHA, and oxacillin-salt agar in the detection of MRS were 96.3% and 100.0%, 85.2% and 100.0%, 77.8% and 100.0%, 92.6% and 94.5%, respectively for SA. 2 strains of SA formed colonies on the oxaciUin-salt agar at 48 hours after incubation. The sensitivity of detection of SA in oxacillin-salt agar was 100% in 48 hours. The sensitivity and specificity of these four methods were 97.8% and 80.0%, 95.6% and 80.0%, 95.6% and 80.0%, and 100% and 80.0%, respectively in CoNS（P〉0.05）. Conclusion Results from this study inducated that all these four screening methods are reliable in the detection of MRS. Both the cefoxitin disk and oxaciUin-salt agars have a high application value.