Predictive values of species' identifications from the Vitek Gram-Positive Identification Card using clinical isolates of coagulase-negative staphylococci.

The Gram-Positive Identification Card (GPI, bioMerieux Vitek) was compared to conventional tests for identification of 616 clinical isolates of coagulase-negative staphylococci. All tests were inoculated with subcultures from single isolated colonies. The predictive values of GPI species' identifications (the number of the system's correct calls divided by the total number of calls for each species) were 100% (12 of 12) for Staphylococcus capitis, 100% (79 of 79) for S saprophyticus, 98.4% (246 of 250) for S epidermidis and 96.0% (120 of 125) for S haemolyticus, but only 64.5% (69 of 107) for the other species analyzed. When an infrequently encountered Staphylococcus species is named using the GPI, the identification should be confirmed using additional tests.