头孢西丁纸片评价耐甲氧西林葡萄球菌的探讨

Evaluation of Cefoxitin Disk for Detection of Methicillin-resistant Staphylococcus

目的评价头孢西丁纸片法检测耐甲氧西林葡萄球菌(MRS)的特异性和灵敏度。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(CoNS)52株,分别进行头孢西丁纸片法、添加4% NaCl的头孢西丁纸片法、添加2% NaCl的苯唑西林纸片法以及苯唑西林-盐琼脂法检测,以苯唑西林-盐琼脂法作为MRS检测标准,按CLSI2006版标准判读结果。结果头孢西丁纸片、添加4% NaCl的头孢西丁纸片、添加2% NaCl的苯唑西林纸片检测MRS特异性均达100.0%;对于金黄色葡萄球菌3种纸片法的灵敏度分别为82.7%、79.3%、72.4%;对于凝固酶阴性葡萄球菌,3种纸片法的灵敏度分别为97.9%、95.8%、95.8%。加盐与不加盐头孢西丁纸片法检测MRS的差异无显著性(P>0.05),耐药株抑菌圈直径(mm)分别为10.68±6.42、13.36±7.37(P<0.01)。结论加盐与不加盐头孢西丁纸片法均能可靠检测MRS,前者对耐药株结果更易判读。

Objective To evaluate sensitivity and specificity of cefoxitin disk diffusion for detection of methlcillln-resistant Staphylococcus. Methods Staphylococcus aureus（SA） 100 strains and coagulase-negative Staphylococcus（CoNS） 52 strains from clinical samples were tested by cefoxitin disk diffusion,cefoxitin disk diffusion appending 4% salt in muellerhinton agar（MHA）,oxacillin disk diffusion appending 2%salt in MHA and oxacillin-salt agar respectively with oxacillinsalt agar as gold standard. Results The specificities that cefoxitin disk,cefoxitin disk appending 4% salt in MHA and oxacillin disk appending 2% salt in MHA for detection of MRS were 100.0%. The sensitivities of three disks were 82.7%, 79.3%,72.4% in SA. The sensitivities of three disks were 97.9%,95.8%,95.8% in CONS. The difference between cefoxitin disk appending 4% salt in MHA and cefoxitin disk for detection MRS was not significant （P〉0.05）. The inhibitor diameters（mm） were 10. 68±6. 42 and 13. 36±7. 37 in resistant strains （P〈0. 01）. Conclusion The results suggested that cefoxitin disk diffusion appending salt in MHA and cefoxitin disk can detect MRS reliably. The former result is easier to be read in resistant strains.