Evaluation of Vitek and API 20S for species identification of enterococci.

The performance of the Vitek System and the API 20S for identifying enterococci to the species level was evaluated in comparison with a conventional reference test scheme. A total of 369 isolates originally derived from a sample from 97 medical centers were tested, and the percentage of correctly identified organisms was (Vitek/API): 97.6%/79.2%, 95.3%/91.2%, and 86.0%/20.7% for Enterococcus faecalis, Enterococcus faecium, and Enterococcus non-faecalis-non-faecium species, respectively. In addition, the predictive values for species identification of the results reported by the systems were 98.1% for Vitek and 85.9% for API. The Vitek System GPI card (software version > or = 8.1) was considered to be very acceptable for enterococci identification, with errors principally among the rare Enterococcus raffinosus isolates.