Antibiotic resistance of coagulase-negative staphylococci and micrococci.

Five hundred and seventy strains of Gram-positive, catalase-positive, coagulasenegative cocci from various sources were classified on the basis of their ability to grow anaerobically and to ferment mannitol. Five groups were distinguished. The frequency of strains classified in the five groups varied with the source. Only 26% of the strains were sensitive to all the nine antibiotics used in the tests. About half the strains from the lesions of hospital patients were resistant to penicillin, streptomycin, and tetracycline, and about 10% of them were resistant to cloxacillin. In general the frequency of antibiotic resistance and the ;width' of the resistance spectrum were greater in strains from hospital sources than in those from outside hospital, and they were also greater among strains regarded as falling in the genus Staphylococcus than in those classed as Micrococcus.