Evaluation of three rapid methods for detection of methicillin resistance in Staphylococcus aureus.
The probe-based Velogene Rapid MRSA Identification Assay (ID Biomedical Corp., Vancouver, British Columbia, Canada) and the latex agglutination MRSA-Screen (Denka Seiken Co., Tokyo, Japan) were evaluated for their ability to identify methicillin-resistant Staphylococcus aureus (MRSA) and to distinguish strains of MRSA from borderline oxacillin-resistant S. aureus (BORSA; mecA-negative, oxacillin MICs of 2 to 8 microgram/ml). The Velogene is a 90-min assay using a chimeric probe to detect the mecA gene. MRSA-Screen is a 15-min latex agglutination test with penicillin-binding protein 2a antibody-sensitized latex particles. We compared these assays with the BBL Crystal MRSA ID System (Becton Dickinson, Cockeysville, Md.) and with PCR for mecA gene detection. A total of 397 clinical isolates of S. aureus were tested, consisting of 164 methicillin-susceptible strains, 197 MRSA strains, and 37 BORSA strains. All assays performed well for the identification of MRSA with sensitivities and specificities for Velogene, MRSA-Screen, and BBL Crystal MRSA ID of 98.5 and 100%, 98.5 and 100%, and 98.5 and 98%, respectively. Three MRSA strains were not correctly identified by each of the Velogene and MRSA-Screen assays, but repeat testing with a larger inoculum resolved the discrepancies. The BBL Crystal MRSA ID test misclassified four BORSA strains as MRSA. Both the Velogene and the MRSA-Screen assays are easy to perform, can accurately differentiate BORSA isolates from MRSA isolates, and provide a rapid alternative for the detection of methicillin resistance in S. aureus in clinical laboratories, especially when mecA PCR gene detection is unavailable.
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Department of Microbiology, SD Laboratory Services, Sunnybrook and Women's College Health Sciences Centre, and the University of Toronto, Toronto, Ontario M4N 3M5, Canada. llouie@srcl.sunnybrook.utoronto.ca
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D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification; D005069:Evaluation Studies as Topic; D006602:Hexosyltransferases; D006801:Humans; D007841:Latex Fixation Tests / Q000379:methods*; D016106:Methicillin Resistance / Q000235:genetics; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000235:genetics / Q000302:isolation & purification; D010068:Oxacillin / Q000494:pharmacology; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D016133:Polymerase Chain Reaction / Q000379:methods*; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects*
D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D011933:Reagent Kits, Diagnostic; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D010068:Oxacillin