Oxacillin minimum inhibitory concentrations (MICs) determined by the Etest (A), relative expression of mecA in the absence (B), and the presence of half MICs of oxacillin (C) and penicillin-binding protein 2a (PBP2a) agglutination (D) of study methicillin-resistant Staphylococcus aureus parental and sarA mutant strain sets. B, Relative transcription levels of mecA represent the mean (+SD) of 3 biological replicates in vitro. The fold changes represent the normalized mecA expression (2−ΔCt) to the housekeeping gene gyrB. *P < .05, compared with their respective parental strains. Open bars, parental strain; shaded bars, sarA mutant. D, mecA-positive (ATCC 43300) and mecA-negative (ATCC 25923) controls. Interpretation of agglutination intensity: +++, high; ++, moderate; +, low; and −, none.