Detection of methicillin-resistant staphylococci.

Susceptibility tests commonly used in the clinical laboratory for detection of methicillin-resistant strains of staphylococci are discussed. The biochemical and genetic basis of methicillin resistance, including heterogeneous expression of resistance, is summarized. The conditions that can affect results of disk diffusion, broth dilution, and agar screen tests and sensitivity and specificity of these tests are reviewed. DNA detection methodologies, which, with their greater accuracy, may replace susceptibility testing, also are discussed.