Hussain Z, Stoakes L, Garrow S, Longo S, Fitzgerald V, Lannigan R
London Health Sciences Centre, The University of Western Ontario, London, Ontario, Canada.
J Clin Microbiol. 2000 Jun;38(6):2051-4. doi: 10.1128/JCM.38.6.2051-2054.2000.
A rapid slide latex agglutination (LA) test, MRSA-Screen (Denka Seiken Co., Niigata, Japan), which detects PBP 2a, was tested for its ability to differentiate between mecA-positive and -negative coagulase-negative staphylococci. A total of 463 isolates from 13 species were included in the study. The mecA gene was detected by PCR, and the oxacillin MIC was determined by the agar dilution method according to the guidelines of the National Committee for Clinical Laboratory Standards (NCCLS). The LA test was performed with oxacillin-induced isolates. The true-positive and true-negative results were defined on the basis of the presence or the absence of the mecA gene. By PCR, 251 isolates were mecA positive and 212 were mecA negative. The sensitivities, specificities, and positive and negative predictive values for the LA test compared to the NCCLS breakpoint for oxacillin resistance (>/=0.5 mg/liter) were as follows: for the LA test, 100, 99.5, 99.6, and 100%, respectively; for the NCCLS breakpoint, 100, 60.8, 75.1, and 100%, respectively. One hundred twenty-five mecA-positive isolates were also tested by the LA test without induction of PBP 2a; only 72 (57.6%) gave a positive result and required 3 to 15 min for reaction. With induction, all 251 isolates were positive within 3 min. The LA test was reliable in classifying mecA-negative isolates, but it classified isolates for which the oxacillin MIC was >/=0.5 mg/liter as oxacillin susceptible. For the reliable detection of oxacillin resistance by the MRSA-Screen in coagulase-negative staphylococci, induction of the mecA gene appears to be necessary.
一种快速玻片乳胶凝集（LA）试验，即MRSA-Screen（日本新潟市电気化学工业株式会社），可检测青霉素结合蛋白2a（PBP 2a），对其区分mecA阳性和阴性凝固酶阴性葡萄球菌的能力进行了检测。该研究共纳入了来自13个菌种的463株分离株。通过聚合酶链反应（PCR）检测mecA基因，并根据美国国家临床实验室标准委员会（NCCLS）的指南，采用琼脂稀释法测定苯唑西林的最低抑菌浓度（MIC）。LA试验用于检测经苯唑西林诱导的分离株。根据mecA基因的有无来定义真阳性和真阴性结果。通过PCR检测，251株分离株mecA阳性，212株mecA阴性。与NCCLS规定的苯唑西林耐药断点（≥0.5mg/L）相比，LA试验的敏感性、特异性、阳性预测值和阴性预测值分别如下：LA试验分别为100%、99.5%、99.6%和100%；NCCLS断点分别为100%、60.8%、75.1%和100%。还对125株mecA阳性分离株进行了未诱导PBP 2a的LA试验；只有72株（57.6%）呈阳性结果，反应时间为3至l5分钟。经过诱导后，所有251株分离株在3分钟内均呈阳性。LA试验在对mecA阴性分离株进行分类时是可靠的，但它将苯唑西林MIC≥0.5mg/L的分离株分类为苯唑西林敏感株。对于通过MRSA-Screen可靠检测凝固酶阴性葡萄球菌中的苯唑西林耐药性，mecA基因的诱导似乎是必要的。
