EVALUATION OF RAPIDEC STAPH FOR IDENTIFICATION OF STAPHYLOCOCCUS-AUREUS, STAPHYLOCOCCUS-EPIDERMIDIS, AND STAPHYLOCOCCUS-SAPROPHYTICUS

RapiDEC Staph is a test for presumptive identification of the principa l human staphylococcal species, Staphylococcus aureus, S. epidermidis, and S. saprophyticus. The test includes control and test cupules for fluorogenic detection of coagulase and chromogenic substrates for alka line phosphatase and beta-galactosidase. These tests identify S. aureu s, S. epidermidis, and S. saprophyticus, respectively. Positive result s with both chromogenic substrates provide a presumptive identificatio n of S. xylosus or S. intermedius (S. xylosus-S. intermedius). Test cu pules are inoculated with an organism suspension, and reactions are re ad after a 2-h incubation. RapiDEC-Staph was evaluated with 303 clinic al and stock staphylococcal strains. Identifications were compared wit h those obtained by the tube coagulase test, a latex slide coagulase t est (StaphAUREX), another commercial identification system (Staph-TRAC ), and additional conventional tests. RapiDEC-Staph correctly identifi ed 100% of 130 S. aureus strains, 70.3% of 74 S. epidermidis strains, and 81.3% of 32 S. saprophyticus strains. Four of five S. xylosus isol ates were called S. xylosus-S. intermedius. Unidentified S. epidermidi s and S. saprophyticus strains were called ''Staphylococcus spp.'' Amo ng the 62 other coagulase-negative staphylococci, 4 were misidentified as S. epidermidis and 7 were misidentified as S. saprophyticus. While the sensitivity and specificity of the fluorogenic coagulase test for S. aureus were 100%, failure to detect alkaline phosphatase activity in several S. epidermidis isolates resulted in fewer correct identific ations by the RapiDEC-Staph test for this species.