Emory University School of Medicine, Atlanta, Georgia, USA.
J Clin Microbiol. 2011 Jan;49(1):177-83. doi: 10.1128/JCM.01128-10. Epub 2010 Nov 3.
Staphylococcus aureus clinical isolates with vancomycin MICs of 2 μg/ml have been associated with vancomycin therapeutic failure and the heteroresistant vancomycin-intermediate S. aureus (hVISA) phenotype. A population analysis profile (PAP) with an area under the curve (AUC) ratio of ≥ 0.9 for the AUC of the clinical isolate versus the AUC for hVISA strain Mu3 is most often used for determining hVISA, but it is time-consuming and labor-intensive. A collection of 140 MRSA blood isolates with vancomycin MICs of 2 μg/ml by reference broth microdilution and screened for hVISA using PAP-AUC (21/140 [15%] hVISA) were tested by additional methods to detect hVISA. The methods included (i) Etest macromethod using vancomycin and teicoplanin test strips, brain heart infusion (BHI) agar, and a 2.0 McFarland inoculum; (ii) Etest glycopeptide resistance detection (GRD) using vancomycin-teicoplanin double-sided gradient test strips on Mueller-Hinton agar (MHA) with 5% sheep blood and a 0.5 McFarland inoculum; and (iii) BHI screen agar plates containing 4 μg/ml vancomycin and 16 g/liter casein using 0.5 and 2.0 McFarland inocula. Each method was evaluated using PAP-AUC as the reference method. The sensitivity of each method for detecting hVISA was higher when the results were read at 48 h. The Etest macromethod was 57% sensitive and 96% specific, Etest GRD was 57% sensitive and 97% specific, and BHI screen agar was 90% sensitive and 95% specific with a 0.5 McFarland inoculum and 100% sensitive and 68% specific with a 2.0 McFarland inoculum. BHI screen agar with 4 μg/ml vancomycin and casein and a 0.5 McFarland inoculum had the best sensitivity and specificity combination, was easy to perform, and may be useful for clinical detection of hVISA.
金黄色葡萄球菌临床分离株的万古霉素 MIC 值为 2μg/ml 与万古霉素治疗失败和异质性万古霉素中介金黄色葡萄球菌(hVISA)表型有关。用于确定 hVISA 的最常用方法是使用 AUC 比值≥0.9 的曲线下面积(AUC)比值的群体分析谱(PAP),与 hVISA 菌株 Mu3 的 AUC 进行比较,但这种方法既耗时又费力。通过参考肉汤微量稀释法测定万古霉素 MIC 值为 2μg/ml 的 140 株耐甲氧西林金黄色葡萄球菌(MRSA)血分离株,并通过 PAP-AUC 筛查 hVISA(21/140[15%]hVISA),用其他方法检测 hVISA。这些方法包括(i)使用万古霉素和替考拉宁测试条、脑心浸液(BHI)琼脂和 2.0 McFarland 接种物的 Etest 大方法;(ii)在含 5%绵羊血的 Mueller-Hinton 琼脂(MHA)上使用万古霉素-替考拉宁双面梯度测试条的 Etest 糖肽耐药检测(GRD),接种物为 0.5 McFarland;和(iii)含有 4μg/ml 万古霉素和 16g/l 酪蛋白的 BHI 筛选琼脂平板,接种物为 0.5 和 2.0 McFarland。每种方法均使用 PAP-AUC 作为参考方法进行评估。当在 48 小时读取结果时,每种方法检测 hVISA 的灵敏度更高。Etest 大方法的灵敏度为 57%,特异性为 96%,Etest GRD 的灵敏度为 57%,特异性为 97%,BHI 筛选琼脂的灵敏度为 90%,特异性为 95%,接种物为 0.5 McFarland,灵敏度为 100%,特异性为 68%,接种物为 2.0 McFarland。含有 4μg/ml 万古霉素和酪蛋白的 0.5 McFarland 接种物的 BHI 筛选琼脂具有最佳的灵敏度和特异性组合,操作简单,可能有助于临床检测 hVISA。