Department of Emergency Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan.
J Antimicrob Chemother. 2014 Jan;69(1):211-8. doi: 10.1093/jac/dkt340. Epub 2013 Aug 29.
Emerging evidence shows that methicillin-resistant Staphylococcus aureus (MRSA) infections caused by isolates with higher vancomycin MICs within the susceptibility range are associated with adverse outcomes. No study, however, has examined different susceptibility tests in predicting treatment outcomes of MRSA infections.
This retrospective cohort study included 393 patients with MRSA bacteraemia. Vancomycin MICs for all MRSA isolates were determined simultaneously by agar dilution and the Etest, and using the MicroScan, VITEK-2 and Phoenix automated systems, and categorized into low- and high-MIC isolates at a breakpoint of ≥ 2 mg/L. The essential and categorical agreement between testing methods was compared. The method-specific ability to predict in-hospital mortality was examined by multivariate logistic regression analysis controlling for other potential confounders using clinical data from 310 vancomycin-treated MRSA bacteraemia patients.
The agar dilution, Etest, MicroScan, VITEK-2 and Phoenix methods assessed 14.2% (56/393), 9.7% (38/393), 28.8% (113/393), 22.6% (89/393) and 3.1% (12/393) of MRSA isolates as having high (≥ 2 mg/L) vancomycin MICs. The essential and categorical agreement between testing methods ranged from 98.5% to 100% and from 73.8% to 91.9%, respectively. High vancomycin MICs for isolates determined using agar dilution and the Etest independently predicted mortality when controlling for confounding factors [adjusted OR, 2.321; 95% CI, 1.160-4.641; and adjusted OR, 3.121; 95% CI, 1.293-7.536, respectively]. High vancomycin MICs determined using all three automated systems failed to predict mortality.
Vancomycin MICs generated by the agar dilution and Etest methods, but not the automated systems, independently predicted mortality among vancomycin-treated MRSA bacteraemia patients. Clinicians should incorporate this information with clinical assessment for decisions on appropriate anti-MRSA treatment.
新出现的证据表明，在药敏范围内，较高万古霉素 MIC 的耐甲氧西林金黄色葡萄球菌（MRSA）分离株引起的感染与不良结局相关。然而，尚无研究检查不同的药敏试验在预测 MRSA 感染的治疗结果方面的作用。
本回顾性队列研究纳入了 393 例 MRSA 菌血症患者。通过琼脂稀释法和 Etest 同时测定所有 MRSA 分离株的万古霉素 MIC，并使用 MicroScan、VITEK-2 和 Phoenix 自动化系统进行测定，以 2mg/L 为分界点将 MIC 分为低和高 MIC 分离株。比较了不同检测方法之间的关键和分类一致性。通过多变量逻辑回归分析，根据 310 例接受万古霉素治疗的 MRSA 菌血症患者的临床数据，控制其他潜在混杂因素，评估方法特异性预测院内死亡率的能力。
琼脂稀释法、Etest、MicroScan、VITEK-2 和 Phoenix 方法分别评估了 14.2%（56/393）、9.7%（38/393）、28.8%（113/393）、22.6%（89/393）和 3.1%（12/393）的 MRSA 分离株具有较高（≥2mg/L）的万古霉素 MIC。不同检测方法之间的关键和分类一致性分别为 98.5%至 100%和 73.8%至 91.9%。在控制混杂因素后，琼脂稀释法和 Etest 确定的分离株万古霉素 MIC 较高独立预测死亡率[调整后的比值比，2.321；95%可信区间，1.160-4.641；和调整后的比值比，3.121；95%可信区间，1.293-7.536]。所有三个自动化系统确定的高万古霉素 MIC 均未能预测死亡率。
琼脂稀释法和 Etest 方法产生的万古霉素 MIC 可独立预测接受万古霉素治疗的 MRSA 菌血症患者的死亡率，而自动化系统则不能。临床医生应将这些信息与临床评估相结合，以便对适当的抗-MRSA 治疗做出决策。
