National Center for Antimicrobials and Infection Control, Statens Serum Institut, Copenhagen, Denmark.
J Antimicrob Chemother. 2010 Apr;65(4):717-20. doi: 10.1093/jac/dkq001. Epub 2010 Feb 3.
To evaluate two enrichment broths for methicillin-resistant Staphylococcus aureus (MRSA) detection and compare results with direct plating.
Swabs from 1224 patients were re-analysed for MRSA in a central laboratory (Münster) using six methods. Swabs were suspended in 0.5 mL of non-selective enrichment broth (NB) and vortexed. Aliquots of 100 microL were inoculated on/into: (I) ChromID MRSA agar; (II) Columbia sheep blood (5%) agar (BA) and ChromID MRSA; (III, IV) NB incubated overnight followed by plating on BA and ChromID MRSA; and (V, VI) a semi-selective broth containing cefoxitin and aztreonam (TSB-SSI) incubated overnight followed by plating on BA and ChromID MRSA. In III-VI, 100 microL of the enriched broth was plated on each agar.
The combined MRSA-positive rate was 21.5%. MRSA isolates detected by each method were: TSB-SSI, n = 223; NB, n = 205; BA and ChromID MRSA, n = 203; ChromID MRSA alone, n = 183. TSB-SSI detected more positive throat samples than the comparators and significantly reduced methicillin-susceptible S. aureus (MSSA) growth. The maximum sensitivity obtained was only 85%, possibly due to the study design using pre-used swabs and dilution of swab material. For 997 samples, results from Münster were compared with initial results. Peripheral laboratories identified 172 MRSA compared with Münster where 186, 186 and 204 MRSA were found for direct plating, NB and TSB-SSI broth, respectively.
TSB-SSI was superior to both NB and direct plating on ChromID MRSA and BA. Despite re-using swabs for the study, we showed that routine diagnostic screening could be significantly improved, using a semi-selective enrichment broth.
评估两种用于耐甲氧西林金黄色葡萄球菌（MRSA）检测的增菌肉汤，并与直接平板培养法比较结果。
在一个中央实验室（明斯特）中，使用六种方法对 1224 名患者的拭子进行 MRSA 再分析。将拭子混悬于 0.5 mL 非选择性增菌肉汤（NB）中并涡旋。取 100μL 等分试样接种于：（I）ChromID MRSA 琼脂；（II）哥伦比亚绵羊血（5%）琼脂（BA）和 ChromID MRSA；（III、IV）NB 孵育过夜，然后在 BA 和 ChromID MRSA 平板上划线；（V、VI）含有头孢西丁和氨曲南的半选择性肉汤（TSB-SSI）孵育过夜，然后在 BA 和 ChromID MRSA 平板上划线。在 III-VI 中，将 100μL 增菌肉汤分别接种于各琼脂平板。
联合 MRSA 阳性率为 21.5%。每种方法检测到的 MRSA 分离株为：TSB-SSI，n=223；NB，n=205；BA 和 ChromID MRSA，n=203；单独 ChromID MRSA，n=183。TSB-SSI 比对照方法检测到更多的阳性咽喉样本，且显著减少了耐甲氧西林金黄色葡萄球菌（MSSA）生长。获得的最高灵敏度仅为 85%，这可能是由于使用预用拭子和稀释拭子材料的研究设计所致。对 997 个样本，将明斯特的结果与初始结果进行比较。外围实验室鉴定出 172 株 MRSA，而明斯特则分别发现直接平板培养、NB 和 TSB-SSI 肉汤法中 186、186 和 204 株 MRSA。
TSB-SSI 优于 NB 和直接平板培养 ChromID MRSA 和 BA。尽管该研究重新使用了拭子，但我们表明，使用半选择性增菌肉汤可以显著改进常规诊断筛查。
