Multiplex PCR assays for the detection of clinically relevant antibiotic resistance genes in staphylococci isolated from patients infected after cardiac surgery

Multiresistant staphylococci (82 Staphylococcus aureus and 114 coagulase-ne gative staphylococci) were characterized by testing with rapid multiplex po lymerase chain reaction (PCR) assays for species identification and detecti on of associated antibiotic resistance genes. These 196 staphylococci were isolated from 149 adult patients who developed wound infection after electi ve coronary artery bypass grafts and/or valve surgery. The multiplex PCR as says allowed identification of the most common staphylococcal species with S. aureus- and Staphylococcus epidermidis-specific primers as well as the d etection of the erythromycin resistance genes ermA, ermB, ermC and msrA, th e aminoglycoside resistance gene aac(6')-aph(2 "), the oxacillin resistance gene mecA and the penicillin resistance gene blaZ. There was a very good c orrelation between the genotypic analysis by PCR and the phenotype determin ed by standard methods of susceptibility testing and identification of stap hylococcal species: 100% for erythromycin resistance, 98.0% for gentamicin resistance, 99.0% for oxacillin resistance, 100% for penicillin resistance and 100% for S. aureus and S. epidermidis species identification. This stud y suggests that the incidence and distribution of the tested clinically rel evant antibiotic resistance genes in staphylococci associated with infectio ns after cardiac surgery do not differ from those in strains from other inf ections. These multiplex PCR assays may be used as diagnostic tools to repl ace or complement standard methods of susceptibility testing and identifica tion of staphylococci.