Evaluation of Staph ID 32 system and Staph-Zym system for identification of coagulase-negative staphylococci

Abstract

The purpose of the investigation was to evaluate two commercially available identification systems: a new modification of the Staph-Zym system (Rosco, Tastrup, Denmark) and the Staph ID 32 API system (API System, BioMerieux, Paris, France). A local standard method to be used in routine laboratories was also evaluated. A total of 200 staphylococcal isolates, including strains from both the American Type Culture Collection and the Czechoslovak Collection of Microorganisms as well as 89 clinical isolates, were used in tests of all three identification systems. The Staph ID 32 API system identified from 50 to 100% of the reference strains and 82.1% of the clinical isolates correctly. The Staph-Zym system identified from 90 to 100% of the reference strains and 82.1% of the clinical isolates correctly. Most misidentifications were of minor importance, but in both systems major failures appeared (Staphylococcus aureus was identified as a coagulase- negative staphylococcus). Both systems needed backup from a reference laboratory to determine if two isolates were of the same strain.