Evaluation of a latex agglutination assay for rapid detection of oxacillinresistant Staphylococcus aureus

Oxacillin resistance in Staphylococcus aureus is mediated by the mecA gene, resulting in production of penicillin-binding protein 2a (PBP2a), which is not present in the oxacillin susceptible strains. We evaluated the ability of a 30-min latex agglutination (LA) test (Seiken, Tokyo, Japan) to detect production of PBP2a in 315 clinical isolates of S. aureus. The LA results were compared with results of susceptibility testing using the Vitek GPS-SV test card. The latex test was positive for all 206 isolates determined to be methicillin resistant by Vitek (sensitivity 100%), the latex test was ne gative for 108 of 109 isolates determined to be oxacillin susceptible by Vi tek, and the latex test was positive for 1 isolate determined to be suscept ible by Vitek (specificity 99.1%). The discrepant isolate was negative for the mecA gene by polymerase chain reaction (PCR). The LA test is a rapid an d reliable method for detecting oxacillin resistant S. aureus. (C) 2000 Els evier Science Inc. All rights reserved.