金黄色葡萄球菌甲氧苄啶/磺胺甲恶唑耐药小菌落变异体的筛选方法。
Screening method for trimethoprim/sulfamethoxazole-resistant small colony variants of Staphylococcus aureus.
机构信息
Division of Clinical Infectious Diseases and Chemotherapy, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi Prefecture 981-8558, Japan.
Division of Clinical Infectious Diseases and Chemotherapy, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi Prefecture 981-8558, Japan.
出版信息
J Glob Antimicrob Resist. 2018 Dec;15:1-5. doi: 10.1016/j.jgar.2018.05.008. Epub 2018 May 29.
OBJECTIVES
Trimethoprim/sulfamethoxazole (SXT) is used to treat Staphylococcus aureus infections. However, the effect of treatment with SXT is sometimes not sufficient and there are patients whose treatment has to be prolonged. There are few reports of isolated strains of SXT-resistant S. aureus, but it is possible that some resistant strains cannot be detected by current testing methods We have therefore developed a tool to identify these resistant strains.
METHODS
The mutant selection window (MSW) of SXT for 40 clinical isolates of S. aureus, including 20 methicillin-resistant S. aureus (MRSA), was determined. The optimum concentration of SXT and thymidine in agar for detecting SXT-resistant small colony variants (SCVs) of S. aureus was investigated.
RESULTS
The MSW and MSW of SXT, presented as a multiple of the minimum inhibitory concentration (MIC), were 16× MIC and >256× MIC, respectively. SCVs were detected within the MSW in 32 (80%) of the 40 clinical isolates studied. To maintain the morphology of SCVs, the most suitable concentrations of SXT and thymidine for screening were 4mg/L and 0.01μg/mL, respectively. All 32 SCVs were resistant to SXT (MIC >32mg/L). The sensitivity and specificity of this screening method was 100% and 88.9%, respectively.
CONCLUSIONS
SXT-resistant SCVs are not usually detected by routine laboratory tests performed in hospitals. However, the screening test described here can easily distinguish SXT-resistant SCVs among S. aureus isolated from specimens. This newly developed screening test could become an important tool to prevent inappropriate use of SXT.
目的
甲氧苄啶-磺胺甲噁唑（SXT）用于治疗金黄色葡萄球菌感染。然而，SXT 的治疗效果有时并不充分，有些患者的治疗需要延长。虽然有少数 SXT 耐药金黄色葡萄球菌的分离株的报道，但有可能有些耐药株无法被当前的检测方法检测到。因此，我们开发了一种识别这些耐药株的工具。
方法
测定了 40 株金黄色葡萄球菌临床分离株（包括 20 株耐甲氧西林金黄色葡萄球菌（MRSA））对 SXT 的突变选择窗（MSW）。研究了琼脂中 SXT 和胸苷检测金黄色葡萄球菌 SXT 耐药小菌落变异体（SCV）的最佳浓度。
结果
SXT 的 MSW 和 MSW 分别表示为最小抑菌浓度（MIC）的 16 倍和>256 倍。在所研究的 40 株临床分离株中，有 32 株（80%）在 MSW 内检测到 SCVs。为了保持 SCVs 的形态，筛选最适的 SXT 和胸苷浓度分别为 4mg/L 和 0.01μg/mL。所有 32 株 SCV 对 SXT 均耐药（MIC>32mg/L）。该筛选方法的灵敏度和特异性分别为 100%和 88.9%。
结论
医院常规实验室检测通常无法检测到 SXT 耐药 SCVs。然而，这里描述的筛选试验可以很容易地在从标本中分离的金黄色葡萄球菌中区分 SXT 耐药 SCVs。这种新开发的筛选试验可能成为预防 SXT 不当使用的重要工具。
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