Willke Ayşe, Sayan Murat, Meriç Meliha, Mutlu Birsen
Department of Infectious Diseases and Clinical Microbiology, Kocaeli University Faculty of Medicine, Kocaeli, Turkey.
Mikrobiyol Bul. 2012 Oct;46(4):671-5.
Bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) has a significant morbidity and mortality. The aim of this study was to evaluate the efficiency of real-time polymerase chain reaction (Rt-PCR) targeting nuc and mec genes in the culture extracts of blood culture systems for the early diagnosis of MRSA. A total of 48 samples that gave positive growth signal in BACTEC 9000 MB (BD, USA) and stained as gram-positive cocci, were included in the study. The samples were collected between 2009 and 2010. VITEC 2 (bioMerieux, France) system was used for the identification and antibiotic susceptibility testing of the isolates. According to the culture results, 15 of the isolates were methicillin-resistant coagulase-negative staphylococci (MRCNS), four were MRSA, 14 were methicillin-susceptible coagulase- negative staphylococci (MSCNS) and 15 were methicillin-susceptible S.aureus (MSSA). However, Rt-PCR yielded 17 MRCNS, eight MRSA, 10 MSCNS and 13 MSSA results. Our findings indicated lack of concordance between blood culture and PCR technique. When the blood culture results were accepted as the gold standard for the determination of methicillin resistance, sensitivity, specificity, positive and negative predictive values of Rt-PCR were found as 73%, 62%, 56% and 78%, respectively. In conclusion, in contrast to the expectations, Rt-PCR was not considered as an appropriate method for the detection of MRSA in routine diagnosis.
耐甲氧西林金黄色葡萄球菌（MRSA）引起的菌血症具有较高的发病率和死亡率。本研究的目的是评估针对nuc和mec基因的实时聚合酶链反应（Rt-PCR）在血培养系统培养提取物中用于MRSA早期诊断的效率。共有48份在BACTEC 9000 MB（美国BD公司）中发出阳性生长信号且革兰氏染色为阳性球菌的样本纳入本研究。样本采集于2009年至2010年期间。使用VITEC 2（法国生物梅里埃公司）系统对分离株进行鉴定和药敏试验。根据培养结果，15株分离株为耐甲氧西林凝固酶阴性葡萄球菌（MRCNS），4株为MRSA，14株为甲氧西林敏感凝固酶阴性葡萄球菌（MSCNS），15株为甲氧西林敏感金黄色葡萄球菌（MSSA）。然而，Rt-PCR检测结果显示有17株MRCNS、8株MRSA、10株MSCNS和13株MSSA。我们的研究结果表明血培养和PCR技术之间缺乏一致性。当将血培养结果作为确定甲氧西林耐药性的金标准时，Rt-PCR的敏感性、特异性、阳性预测值和阴性预测值分别为73%、62%、56%和78%。总之，与预期相反，Rt-PCR在常规诊断中未被认为是检测MRSA的合适方法。
