Takahashi A, Yamane N, Igari J, Oguri T, Toyoshima S, Moriyasu I, Takemori K, Tosaka M, Minamide W
Department of Clinical Laboratories, Gunma University School of Medicine, Maebashi.
Rinsho Byori. 1994 Sep;42(9):953-60.
The Showa disk susceptibility test using two penicillinase-resistant penicillins, oxacillin and methicillin, was evaluated to discriminate between the strains of Staphylococcus aureus resistant to methicillin (MRSA) and those susceptible (MSSA) in the multi-center trials. The study included 651 clinical isolates of S. aureus, comprising of 329 MRSA and 322 MSSA isolates. The inhibitory zone diameters by Showa disks to oxacillin and methicillin highly correlated with minimum inhibitory concentrations (MICs) determined by standard agar dilutions with 0.961 and 0.930 correlation coefficients, respectively. Of 651 duplicate MIC determinations, 79.9% (oxacillin) and 80.3% (methicillin) were within +/- 1 log2 dilutions with each other. When Showa oxacillin and methicillin disks were incubated at 35 degrees C, sensitivity and specificity of oxacillin to detect MRSA were 95.4% and 98.1%, and those of methicillin were 94.8% and 95.2%. When tested on agar plates supplemented with 5% NaCl, sensitivity and specificity markedly improved to > 97%. Also, when incubated at 30 degrees C, sensitivity and specificity became to nearly 100%. Of 329 MRSA isolates, the interpretive criteria combined with incubation at 30 degrees C and testing onto 5% NaCl supplemented agar plates could correctly identify 324 (98.5%) and 329 (100%) isolates, respectively. In conclusion, when the Showa oxacillin and methicillin disk susceptibility tests were employed exactly according to the manufacturer's instruction, the test performances to detect MRSA were enough reliable to screen MRSA isolates in clinical microbiology laboratories.
在多中心试验中，对使用两种耐青霉素酶青霉素（苯唑西林和甲氧西林）的昭和纸片药敏试验进行了评估，以区分耐甲氧西林金黄色葡萄球菌（MRSA）菌株和敏感菌株（MSSA）。该研究纳入了651株金黄色葡萄球菌临床分离株，其中包括329株MRSA和322株MSSA分离株。昭和纸片对苯唑西林和甲氧西林的抑菌圈直径与通过标准琼脂稀释法测定的最低抑菌浓度（MIC）高度相关，相关系数分别为0.961和0.930。在651次重复的MIC测定中，79.9%（苯唑西林）和80.3%（甲氧西林）彼此之间在±1个log2稀释度范围内。当将昭和苯唑西林和甲氧西林纸片在35℃孵育时, 苯唑西林检测MRSA的敏感性和特异性分别为95.4%和98.1%，甲氧西林的敏感性和特异性分别为94.8%和95.2%。当在补充有5%氯化钠的琼脂平板上进行测试时，敏感性和特异性显著提高至>97%。此外，当在30℃孵育时，敏感性和特异性几乎达到100%。在329株MRSA分离株中，结合在30℃孵育并在补充有5%氯化钠的琼脂平板上进行测试的解释标准，分别可以正确鉴定324株（98.5%）和329株（100%）分离株。总之，当严格按照制造商的说明使用昭和苯唑西林和甲氧西林纸片药敏试验时，检测MRSA的试验性能足够可靠，可用于临床微生物实验室筛选MRSA分离株。
