Schuenck Ricardo P, Lourenco Maria Cristina S, Iório Natália L P, Ferreira Adriana Lúcia P, Nouér Simone A, Santos Kátia Regina N
Departamento de Microbiologia Médica, Instituto de Microbiologia Prof Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Res Microbiol. 2006 Dec;157(10):971-5. doi: 10.1016/j.resmic.2006.08.004. Epub 2006 Sep 12.
To improve efficiency in detecting nasal methicillin-resistant Staphylococcus aureus (MRSA), we evaluated a multiplex PCR using pre-enrichment of the specimen in selective broths, and compared it with detection performed by routine tests in hospital laboratories. Nasal swab specimens from 311 patients were inoculated onto mannitol-salt agar (MSA) at the hospital laboratories and in two Mueller-Hinton broths with 7% NaCl containing oxacillin at concentrations of 2 and 4 micro g/ml. Isolates on MSA were identified as MRSA by classical laboratory tests (coagulase and oxacillin disk diffusion tests). Oxacillin broth cultures were subcultured on blood agar and MRSA isolates were identified by coagulase and susceptibility tests, including agar dilution and the oxacillin-screening method (gold standard method). Simultaneously, multiplex-PCR was performed from the selective broths to detect S. aureus species-specific and mecA gene segments (OxMPCR method). Thirty-two S. aureus isolates were recovered: 29 (90.6%) were MRSA strains and 3 (9.4%) were oxacillin-susceptible isolates. Twenty-eight (96.5%) MRSA isolates were detected by OxMPCR, while 17 (58.6%) were identified by routine tests (P=0.002). This new method for detection of MRSA nasal carriers showed higher sensitivity and led to faster reporting--i.e., within 24 h--of results.
为提高检测鼻腔耐甲氧西林金黄色葡萄球菌（MRSA）的效率，我们评估了一种在选择性肉汤中对标本进行预富集的多重PCR方法，并将其与医院实验室常规检测方法进行比较。从311名患者采集的鼻拭子标本在医院实验室以及两种含2μg/ml和4μg/ml苯唑西林的7%氯化钠Mueller-Hinton肉汤中接种于甘露醇盐琼脂（MSA）。通过经典实验室检测（凝固酶和苯唑西林纸片扩散试验）将MSA上的分离株鉴定为MRSA。将苯唑西林肉汤培养物转种至血琼脂上，通过凝固酶和药敏试验（包括琼脂稀释法和苯唑西林筛选法，即金标准方法）鉴定MRSA分离株。同时，从选择性肉汤中进行多重PCR以检测金黄色葡萄球菌种特异性和mecA基因片段（OxMPCR方法）。共分离出32株金黄色葡萄球菌：29株（90.6%）为MRSA菌株，3株（9.4%）为苯唑西林敏感分离株。通过OxMPCR检测出28株（96.5%）MRSA分离株，而通过常规检测鉴定出17株（58.6%）（P=0.002）。这种检测鼻腔MRSA携带者的新方法具有更高的灵敏度，且能更快（即24小时内）报告结果。
