Classification of coagulase-negative staphylococci in the diagnostic laboratory

One hundred and ninety-eight coagulase-negative staphylococci isolated from urines, blood cultures, and pus samples were classified by means of two identification schemes, and their wall teichoic acids were determined serologically. S. epidermidis, S. saprophyticus, and S. cohnii were identified reliably by the use of five criteria: acid aerobically from sucrose, trehalose, and mannitol, phosphatase production, and sensitivity to novobiocin. Further species, notably S. haemolyticus and S. hominis, could be identified when haemolysis on blood agar plates was included in the criteria group. The investigation shows, that a considerable number of coagulase-negative staphylococci isolated from human specimens belong to species other than S. epidermidis and S. saprophyticus. These staphylococci can cause human infections and should be identified in the diagnostic laboratory. S. epidermidis and S. saprophyticus were found to contain the teichoic acids previously identified in these species. S. cohnii contained the same teichoic acids as S. saprophyticus. No characteristic teichoic acid was demonstrated in the other species, but several strains contained poly C (beta-N-acetylglucosaminylglycerol teichoic acid).