Hanaki H, Hiramatsu K
Dept. Bacteriology, Juntendo-Univ., Tokyo, Japan.
Jpn J Antibiot. 1997 Sep;50(9):794-8.
We evaluated a clinical strain of methicillin-resistant Staphylococcus aureus (MRSA), Mu50, for vancomycin susceptibility. Mu50 was isolated from a patient with infection of a surgical incision site which resisted vancomycin therapy. Mu50 showed a decrease in susceptibility to vancomycin, but this strain did not carry vanA or vanB or vanC genes as judged from PCR amplification. MICs of vancomycin against Mu50 and vancomycin-susceptible S. aureus FDA209P, S. aureus ATCC-29213, and MRSA H-1 were 8, 1, 1, and 1 microgram/ml, respectively by agar dilution and macro-broth dilution methods according to NCCLS. MIC values with agar dilution method using MHA + 20% horse serum, HIA, and BHIA agreed with the MIC values with micro- and macro-broth dilution method. Population analysis revealed that vancomycin concentration required for inhibition of ca. 10(7) cells of Mu50, S. aureus FDA209P, S. aureus ATCC29213, and MRSA H-1 were 36, 2, 2, and 2 micrograms/ml, respectively. These results showed that the activity of vancomycin against Mu50 was at least 8-fold decreased compared to that against S. aureus FDA209P, S. aureus ATCC29213, and MRSA H-1.
我们评估了一株耐甲氧西林金黄色葡萄球菌（MRSA）临床菌株Mu50对万古霉素的敏感性。Mu50是从一名手术切口部位感染且万古霉素治疗无效的患者身上分离得到的。Mu50对万古霉素的敏感性有所下降，但通过PCR扩增判断该菌株未携带vanA、vanB或vanC基因。根据美国国家临床实验室标准委员会（NCCLS）的方法，采用琼脂稀释法和微量肉汤稀释法测定万古霉素对Mu50以及万古霉素敏感的金黄色葡萄球菌FDA209P、金黄色葡萄球菌ATCC - 29213和MRSA H - 1的最低抑菌浓度（MIC），结果分别为8、1、1和1微克/毫升。使用MHA + 20%马血清、HIA和BHIA的琼脂稀释法得到的MIC值与微量肉汤稀释法和常量肉汤稀释法的结果一致。群体分析显示，抑制约10(7)个Mu50、金黄色葡萄球菌FDA209P、金黄色葡萄球菌ATCC29213和MRSA H - 1细胞所需的万古霉素浓度分别为36、2、2和2微克/毫升。这些结果表明，与对金黄色葡萄球菌FDA209P、金黄色葡萄球菌ATCC29213和MRSA H - 1相比，万古霉素对Mu50的活性至少降低了8倍。
