Identification of coagulase-negative staphylococci with the API STAPH-IDENT system

A group of 300 clinically derived isolates of coagulase-negative staphylococci were tested in parallel with the API STAPH-IDENT system (Analytab Products) and 14 conventional biochemical tests contained in Kloos and Schleifer's simplified scheme for identification of human Staphylococcus species. STAPH-IDENT is a miniaturized biochemical test strip that incorporates four synthetic chromogenic substrates, urea, arginine, and four carbohydrates and that requires only a 5-h test period. Use of the STAPH-IDENT system alone allowed correct or partly correct classification of 67% (201 of 300) of the study isolates. However, if a supplemental test was performed (most often novobiocin susceptibility), correct classification of an additional 25.7% (77) was possible, for a total of 92.7% of isolates identified to the species level. Species correctly identified included 94% (116 of 123) of Staphylococcus epidermidis isolates, 98% (63 of 64) of S. saprophyticus, 71% (34 of 48) of S. hominis, 100% (22) of S. simulans, 100% (18) of S. haemolyticus, 100% (17) of S. warneri, and 100% (8) of S. capitis. Fourteen percent (42 of 300) of profile codes encountered in this study were not included in the STAPH-IDENT profile register, but were included in Analytab Products' expanded computer data base.