An evaluation of the novobiocin disc diffusion method for identifying clinical isolates of Staphylococcus...

A total of 350 clinical isolates of gram-positive, catalase-positive cocci were collected from patients at three hospitals over a five-month period. Each isolate was biochemically identified using coagulase production, mannitol and dextrose fermentation, and resistance to a 5-micrograms disc of novobiocin on sheep blood agar, Mueller-Hinton agar, and P agar. After 18-24 hours of incubation at 35 degrees C, zone sizes were read in millimeters, and the results were compared to the reference method of Kloos and Schleifer on P agar. The zone sizes obtained using Mueller-Hinton agar most closely resembled the reference method, while the zone sizes on sheep blood agar had markedly smaller values.