Isolation and properties of bacteriolytic enzyme-producing cocci from the human mouth

Abstract One-hundred-and-one bacteriolytic enzyme-producing organisms were isolated from various sites of the mouth. All were non-hemolytic, Gram-positive, and chain-forming cocci. Ninety-one strains, like the reference strains of Streptococcus defectivus and S. adjacens, were dependent on pyridoxal for growth and produced a chromophore. The Rapid ID32 STREP system speciated these isolates as S. defectivus, S. adjacens or Gemella morbillorum. The remaining 10 bacteriolytic isolates were pyridoxal-independent and 8 belonged to S. intermedius. Some pyridoxal-independent S. intermedius reference strains including ATCC27335T and all group D Enterococcus strains tested were also bacteriolytic. Thus, bacteriolytic enzyme production is common to nutritionally variant streptococci but not unique to S. defectivus and S. adjacens. The nutritionally variant strains generally had arylamidases but not alkaline phosphatase. The S. defectivus strains produced α- and β-galactosidases (biotype 1) whereas the S. adjacens strains generally produced N-acetyl-β-glucosaminidase and some had β-glucuronidase but others did not (biotypes 2 and 3). The G. morbillorum strains had no detectable activity of these glycosidases (biotype 4) but produced a chromophore and an arginine dihydrolase, exhibiting a physiological profile atypical of the Gemella species. This indicates the possible presence of an additional phenotypic group or a new species among the nutritionally variant streptococci.