18h判读CHROMagar MRSA显色筛查培养基的研究

Study on the cultures of CHROMagar MRSA in 18 hours

目的评估CHRO Magar耐甲氧西林金黄色葡萄球菌(MRSA)显色培养基在孵育18h时判读的敏感性和特异性等试验指标。方法选择2007年7月至2009年5月临床分离的176株MRSA阳性菌株和738株MRSA阴性菌株,分别孵育18h和24h判读后进行特异性和敏感性比较。结果 18h和24h判读结果的特异性分别为84.1%、90.0%;敏感性分别为92.1%、87.0%;阳性预测值分别为72.0%、67.0%;阴性预测值分别为96%、97%;阳性似然比分别为10.5、8.2;阴性似然比分别为0.17、0.11。与18h比较,在24h判读结果中有11株阳性菌株在孵育24h时变色(18h判读为阴性),20株阴性菌株在孵育18h时出现红色。假设MRSA的患病率分别为15%、25%、35%时孵育18h的判读阳性预测值分别为65%、78%、85%;孵育24h的判读阳性预测值分别为60%、74%、82%。结论数据证明CHROMagar MRSA用于MRSA的筛查在18h时就具有较高的特异性和敏感性;随着患病率的增高,18h和24h判读阳性预测值差距缩小;在实际工作中,18h判读可缩短样本报告周期,并且使临床医生在选择抗生素时更加快速、准确。

Objective To validate the importance of stringent incubation times for plate CHROMagar per- formance. Methods 176 strains of MRSA-positive and 738 strains of MRSA negative cultures eolleted from July 2007 to May 2009 were evaluated by clinical swabs about the CHROMagar MRSA medium at controlled intervals af ter 18 and 24 hours of incubation. Results 18 h sensitivity and specificity of CHROMagar MRSA were 84.1% and 92.1%respectively. The 18-h positive predictive values ofCHROMagar MRSA, supposing MRSA disease rate was 15% ,25% ,and 35% ,were65%,78% ,and 85% ,respectively. Conclusion CHROMagar MRSA medium held for 18 h incubation is a highly sensitive and specific MRSA-screening tool. 18 h incubation could reduce the time of the sample report, and help the doctors with fast and correct selection of drugs to cure the disease.