STUDIES ON THE ACIDURIC ORAL MICROCOCCI

¹ National Institute of Dental Research, National Institutes of Health, and Department of Bacteriology, University of Maryland, College Park, Md.

A total of 109 strains of aerobic, gram-positive, catalase-positive micrococci were isolated from tomato juice agar (pH 5.0) plates from the salivas of 46 of 59 adults sampled. A study of the biochemical characteristics of these strains revealed that 16 strains from 14 individuals were typical Micrococcus pyogenes var. aureus (Staph. aureus) and one strain was identified as M. pyogenes var. albus (Staph. albus). All of these strains (Group I) were coagulase-positive, gelatinase-positive, and fermented mannitol. The remaining strains consisted of a group of 80 coagulase-negative micrococci (Group II) and a group of 12 strains of phosphatase-negative, tetrad-forming micrococci (Group III).

All of the coagulase-positive oral micrococci (Group I) showed acid phosphatase activity with disodium p-nitrophenyl phosphate, phenolphthalein phosphate, or phenyl phosphate as substrates. Most of the coagulase-negative oral micrococci of Group II also possessed similar acid phosphatase activity for these 3 substrates, which would indicate that the phosphatase test alone is not a reliable substitute for the coagulase test. None of the micrococci showed alkaline phosphatase activity at pH 8.7.