Department of Microbiology & Infectious Diseases, Liverpool Hospital, Locked Bag 7090, Liverpool BC, NSW 1871, Australia.
J Clin Microbiol. 2011 Apr;49(4):1489-94. doi: 10.1128/JCM.02302-10. Epub 2011 Jan 26.
The best screening method for detecting heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) remains unclear. Using population analysis profiling utilizing the area under the concentration-time curve (PAP-AUC) as the gold standard, we screened 458 consecutive methicillin-resistant S. aureus (MRSA) bloodstream isolates to determine the most accurate and cost-effective testing strategy to detect the presence of heteroresistance. All isolates were also tested using the macromethod Etest (MET) and glycopeptide resistance detection (GRD) Etest. The MIC was determined by several methods, including standard vancomycin Etest, vancomycin broth microdilution (BMD), and Vitek2 testing. Fifty-five (12%) hVISA and 4 (1%) VISA isolates were detected by PAP-AUC. Compared to PAP-AUC, the sensitivities and specificities of MET, GRD Etest, BMD (using a MIC cutoff of ≥ 2 mg/liter), and standard vancomycin Etest (using a MIC cutoff of ≥ 2 mg/liter) were 89 and 55%, 71 and 94%, 82 and 97%, and 71 and 94%, respectively. Combination testing increased the overall testing accuracy by reducing the number of false-positive results. Cost was determined predominately by the number of PAP-AUC runs required following a screening assay. The most cost-effective strategy was BMD (using a MIC cutoff of ≥ 2 μg/ml) as a standalone assay or in combination with PAP-AUC, provided that BMD testing was batched. GRD Etest remained an alternative, with 71% of hVISA isolates detected. Prevalence influenced both cost and test accuracy, with results remaining unchanged for hVISA prevalences of up to 25%. Implementation of any testing strategy would therefore be dependent on balancing cost with accuracy in a given population and clinical context.
目前，用于检测异质性万古霉素中介金黄色葡萄球菌（hVISA）的最佳筛选方法仍不明确。本研究使用基于浓度-时间曲线下面积（AUC）的群体分析轮廓法（PAP-AUC）作为金标准，筛选了 458 株连续的耐甲氧西林金黄色葡萄球菌（MRSA）血流感染分离株，以确定最准确和最具成本效益的检测策略，用于检测异质性耐药的存在。所有分离株还使用宏法 Etest（MET）和糖肽耐药检测（GRD）Etest 进行了检测。MIC 通过几种方法确定，包括标准万古霉素 Etest、万古霉素肉汤微量稀释（BMD）和 Vitek2 检测。通过 PAP-AUC 检测到 55（12%）株 hVISA 和 4（1%）株 VISA 分离株。与 PAP-AUC 相比，MET、GRD Etest、BMD（使用 MIC 截断值≥2mg/L）和标准万古霉素 Etest（使用 MIC 截断值≥2mg/L）的敏感性和特异性分别为 89%和 55%、71%和 94%、82%和 97%以及 71%和 94%。联合检测通过减少假阳性结果的数量，提高了整体检测准确性。成本主要取决于筛选试验后所需的 PAP-AUC 运行次数。最具成本效益的策略是 BMD（使用 MIC 截断值≥2μg/ml）作为单独检测或与 PAP-AUC 联合检测，如果将 BMD 检测成批进行的话。GRD Etest 仍然是一种替代方法，可检测到 71%的 hVISA 分离株。流行率影响成本和测试准确性，在 hVISA 流行率高达 25%的情况下，结果保持不变。因此，任何检测策略的实施都将取决于在特定人群和临床环境中平衡成本与准确性。
