COMPARISON OF IDENTIFICATION SYSTEMS FOR STAPHYLOCOCCUS-EPIDERMIDIS AND OTHER COAGULASE-NEGATIVE STAPHYLOCOCCUS SPECIES

Three commercially available systems (API Staph-Trac, API 20GP, and Vi tek GPI), used to identify coagulase-negative staphylococci, were eval uated against 277 bloodstream isolates, including 94 isolates of Staph ylococcus epidermidis and 183 isolates of other coagulase-negative Sta phylococcus species. The conventional method of Kloos and Schleifer se rved as the reference method. Controls included 14 ATCC type culture s trains of coagulase-negative staphylococci. The API Staph-Trac system showed the highest rate of agreement with reference method, correctly identifying 73% of the isolates. The Vitek GPI System had an overall r are of agreement of 67% and the API 20GP system correctly identified 6 1%. The API Staph-Trac system correctly identified 94% of the isolates of S. epidermidis compared with 64% by both Vitek GPI and API 20GP. T he most common error for both Vitek GPI and API 20GP systems was the f ailure to identify organisms contained within the database of the syst ems. Because none of the tested commercial identification systems iden tified ''non-epidermidis'' coagulase-negative Staphylococcus species w ith a high degree of accuracy, the systems need to be markedly improve d or new systems developed.