凝固酶阴性葡萄球菌的青霉素结合蛋白产生和苯唑西林MIC相关性研究

目的分析凝固酶阴性葡萄球菌(CNS)的青霉素结合蛋白2a(PBP2a)的产生和苯唑西林MIC相关性. 方法收集82株临床分离株,采用MRSA胶乳凝集法、MIC法分别检测CNS对苯唑西林的耐药性,比较各试验结果. 结果苯唑西林MIC≥0.5 mg/L或产生PBP2a的表皮葡萄球菌和溶血葡萄球菌均能正确地表示苯唑西林耐药;苯唑西林MIC≥0.5 mg/L解释标准对头葡萄球菌、腐生葡萄球菌、人葡萄球菌、模仿葡萄球菌等CNS评价苯唑西林为耐药,正确性很低,有80.0%未产生PBP2a的菌苯唑西林MIC≥0.5 mg/L,使这些菌被错误地报道苯唑西林耐药. 结论新的苯唑西林解释标准对产生PBP2a的CNS均能正确地评价,而对未产生PBP2a的CNS某些菌种缺乏特异性;MRSA胶乳凝集试剂盒可快速、准确地检测耐苯唑西林的CNS.

Correlation of Oxacillin MIC with PBP2a Carriage in Coagulase-negative Staphylococci

OBJECTIVE To study correlation of oxacillin MIC with PBP2a carriage in coagulase negative staphylococci (CNS). METHODS The MRSA screen Latex agglutination test was evaluated for its ability to detect PBP2a from 82 clinical isolates of coagulase negative staphylococci. The assay was compared with susceptibility testing with VITEK GPS 107 susceptibility cards. RESULTS The new breakpoint correctly evaluated all CNS strains with PBP2a as meticillin resistant, and strains of Staphylococcus epidermidis and S. haemolyticus without PBP2a as meticillin susceptible. The breakpoint of 0.5 mg/L was not specific for S. capitis, S. saprophyticus, S. hominis, and S. simulans, in that it categorized 12 of 15 strains of these species without PBP2a (80.0%) as meticillin resistant.CONCLUSIONS The results of this study indicate that the new oxacillin breakpoint accurately identifies strains of CNS with PBP2a but is not specific for strains of certain species of CNS without PBP2a. The MRSA screen test accurately and rapidly detects oxacillin resistance in CNS.