Reproducibility of three identification systems for biotyping of coagulase-negative staphylococci

Three commercial identification systems were evaluated as tools for biotyping coagulase-negative staphylococci. Emphasis was placed on the reproducibility of component tests and not on the ability of these kits to identify these bacteria accurately. Forty-seven clinical and reference strains of Staphylococcus were tested in duplicate with each system. The Staph-Ident profile of test results changed for 20 strains on repeat testing, the Staph-Trac profile changed for 10 strains, and the Vitek GPI profile changed for 14 strains. The component tests of each system that were responsible for these profile changes were identified.