Species Identification and Biotyping of Staphylococci by the API Staph-ident System

The API Staph-Ident system, a commercially available biochemical and chromogenic substrate micromethod, was evaluated as a means for identifying the species and determining the biotypes of human strains of staphylococci routinely encountered in a clinical microbiology laboratory. The species identity of 152 of 188 (80.9%) unique clinical isolates of staphylococci was correctly predicted by this method after 5 h of incubation according to the recommendations of the manufacturer. When results were determined after 24 h of incubation, the overall accuracy of this procedure was 90.4%. The API Staph-Ident system was not an adequate procedure for assessing strain biotypes since the patterns of biochemical reactivity observed with 53 of 54 (98.2%) unique isolates of Staphylococcus aureus were identical. Similarly, 58 of 62 (93.6%) different strains of S. epidermidis yielded the same biochemical profile.