DEOXYRIBONUCLEIC-ACID RELATEDNESS AND PHENOTYPIC CHARACTERISTICS OF ORAL STREPTOCOCCUS-MILLERI STRAINS

Strains of oral Streptococcus milleri group were compared with the typ e strains of Streptococcus anginosus, S. intermedius, and S. constella tus by DNA-DNA hybridization at 60-degrees-C. Of the 29 strains tested , twelve, twelve, and two strains were closely related to S. anginosus ATCC 33397T, S. intermedius ATCC 27335T, and S. constellatus ATCC 278 23T, respectively. Generally, the strains classified in the S. anginos us group in DNA homology were non-beta-haemolytic and belonged to API S. milleri II and biotype I (lactose fermenting), whereas the strains of S. constellatus group were beta-haemolytic and belonged to API S. m illeri I and biotype II (lactose non-fermenting). The strains of the S . intermedius group were all non-beta-haemolytic and belonged to API S . milleri II and mostly biotype II (lactose fermenting). Furthermore, all except one strain of the S. anginosus group were Lancefield group A/serotype a (A/a), ungroupable/serotype b (-/b), C/c, -/d, -/e, F/f o r G/k, whereas those of the S. constellatus group were F/-. The strain s of the S. intermedius group were -/g, -/h, -/i, -/j, or -/-.