Nguyen Van J-C, Kitzis M-D, Ly A, Chalfine A, Carlet J, Ben Ali A, Goldstein F
Laboratoire de microbiologie médicale, Fondation hôpital Saint-Joseph, 185, rue Raymond-Losserand 75674 Paris cedex 14, France.
Pathol Biol (Paris). 2006 May;54(5):285-92. doi: 10.1016/j.patbio.2006.01.001. Epub 2006 Mar 10.
In contrast to "classical" genic amplification, real-time genic amplification can be performed in every laboratory without the need of sophisticated isolation procedures. Moreover, real-time genic amplification allows an early detection of meticillin resistant Staphylococcus aureus colonization, 2 hours compared to 1 or 2 days for culture.
In order to assess the feasibility on Smartcycler of the IDI-MRSA real-time genic amplification assay in comparison with chromogenic media.
A prospective study has been initiated in July 2004: nasal swabs were taken from patients entering the ICU, vascular surgery, diabetology and geriatry wards. During a 4 months period, 682 specimens have been obtained from 508 patients.
Sixty-four (9.3%) patients were positive by genic amplification and selective agar culture (CHROMagar MRSA, MRSASelect and/or ORSAB), 19 (2.9%) were positive by genic amplification only (3 of these patients were under antibiotic treatment); 572 specimens remained negative by both methods. The sensitivity and specificity of this assay were 100% and 96% respectively with a positive predictive value of 70% and negative predictive value of 100%. Initially 82 nasal specimens were unresolved (12%). 38 were resolved following a freeze-thaw cycle. Thus, 44 (6.4%) were unresolved specimens. Comparison between CHROMagar MRSA and MRSASelect showed a good correlation for the detection at 24 hours (5.5% and 5.6% respectively). These two chromogenic media allowed a much better detection of MRSA than ORSAB medium within 24H.
The results obtained by the early real-time genic amplification for the detection of meticillin resistant Staphylococcus aureus are promising. Despite 6.4% amplification failure, we consider that IDI-MRSA real-time genic amplification assay represents a significant breakthrough in the detection of colonization.
与“经典”基因扩增不同，实时基因扩增可在每个实验室进行，无需复杂的分离程序。此外，实时基因扩增能够早期检测耐甲氧西林金黄色葡萄球菌定植，培养需要1或2天，而实时基因扩增只需2小时。
为评估IDI-MRSA实时基因扩增检测法与显色培养基相比在Smartcycler上的可行性。
2004年7月启动一项前瞻性研究：从入住重症监护病房、血管外科、糖尿病科和老年病科病房的患者中采集鼻拭子。在4个月期间，从508例患者中获取了682份标本。
64例（9.3%）患者通过基因扩增和选择性琼脂培养（CHROMagar MRSA、MRSASelect和/或ORSAB）呈阳性，19例（2.9%）仅通过基因扩增呈阳性（其中3例患者正在接受抗生素治疗）；572份标本两种方法均为阴性。该检测法的敏感性和特异性分别为100%和96%，阳性预测值为70%，阴性预测值为100%。最初有82份鼻标本结果未明确（12%）。38份标本经冻融循环后结果明确。因此，有44份（6.4%）标本结果未明确。CHROMagar MRSA和MRSASelect在24小时检测时显示出良好的相关性（分别为5.5%和5.6%）。在24小时内，这两种显色培养基对耐甲氧西林金黄色葡萄球菌的检测效果比ORSAB培养基好得多。
早期实时基因扩增检测耐甲氧西林金黄色葡萄球菌所获得的结果很有前景。尽管有6.4%的扩增失败率，但我们认为IDI-MRSA实时基因扩增检测法在定植检测方面代表了一项重大突破。
