Cuny C, Werner W, Braulke C, Klare I, Witte W (2002): Diagnostics of staphylococci with special reference to MRSA
J. Lab. Med. 26: 165-173.

Until now, 32 species of the genus Staphylococcus have been described, and most have been confirmed at DNA level (DNA-DNA hybridization kinetics, 16S rRNA sequences). Most clinical microbiological diagnostics use agglutination tests for the identification of S. aureus. Since these tests rely on the demonstration of the clumping factor and since this is problematic for epidemic methicillin-resistant S. aureus (MRSA), currently available tests are supplemented with IgG and antibodies against capsular polysaccharides. DNA-based tests have also been established with PCR (e.g., demonstration of a S. aureus specific sequence), some with reverse hybridization. Species diagnostics of coagulase-negative staphylococci is mainly performed by phenotypical biochemical reaction patterns. More recent approaches are based on 16S rRNA sequences, as well as polymorphisms of the hsp60, gap, and internal rRNA gene spacers. Test substances used for phenotypical susceptibility testing of staphylococci should have an indicator function for certain important resistance mechanisms, and results should be interpreted with regard to cross resistance. The gold standard for the demonstration of oxacillin resistance is still PCR for mecA, which can be assessed by reverse hybridization. Phenotypically, penicillin-binding protein 2a can be reliably determined by an antibody-based assay. When using screening tests, the (beta)-lactamase inhibitor sulbactam should be used for excluding borderline resistant isolates (BORSA). Identification of glycopeptide intermediate susceptible S. aureus (GISA) can still only be made phenotypically (screening test, E-test with high inoculum); reliable confirmation is possible by in vitro population assay.