Characterization of staphylococci using the API 20E system

Fifty-four strains of coagulase-negative staphylococci, five isolates of coagulase-positive staphylococci, and seven species of Micrococcus were tested in the API 20E system. After 48 hours' incubation, results indicated that the various species and subgroups could be separated by their reactions. Staphylococcus saphrophyticus subgroup 3 was ONPG and mannitol positive. S. epidermidis subgroup 1 was positive for arginine dihydrolase (ADH), whereas S. epidermidis subgroup 4 was positive for ADH, mannitol, and arabinose. S. aureus coagulase negative was characterized by positive ONPG, ADH, and mannitol. In contrast, S. aureus coagulase positive was not positive for ONPG but was positive for ADH and mannitol. Most of these staphylococci were able to utilize nitrates, urea, glucose, and sucrose. The micrococci, on the other hand, gave varied reactions, with most species being only weakly reactive.