Performance of the chromogenic medium CHROMagar Staph aureus and the staphychrom coagulase test in the detection and identification of Staphylococcusaureus in clinical specimens

CHROMagar Staph aureus (CSAM) (CHROMagar Microbiology, Paris, France) is a new chromogenic medium designed to enable detection of colonies of Staphylo coccus aureus by their pink color, A total of 775 specimens were cultured i n parallel on CHROMagar Staph aureus and conventional media. Among the 267 S. aureus strains recovered on at least one medium, 263 were isolated on CS AM medium (sensitivity, 98.5%), and 245 (sensitivity, 91.8%) were isolated on conventional media. The specificity of presumptive identification of S. aureus on the basis of pink colony color on CSAM medium was 97% (493 of 508 ), This specificity increased to 100% when coagulase detection with the Sta phychrom coagulase test was added and to 98.8% when S. aureus surface compo nents were detected by agglutination in the Pastorex Staph Plus test. Susce ptibility testing of 67 S. aureus strains, performed in parallel on pink CS AM colonies and on colonies grown on blood agar, gave similar results. Thus , rapid and accurate recognition and identification of S. aureus isolates w ere achieved with CSAM as the primary isolation medium, followed by the sta phylocoagulase Staphychrom test. Antimicrobial susceptibility testing (disk -diffusion method or ATE STAPH System) can be performed directly on pink CS AM colonies.