A numerical taxonomic study of Streptococcus sanguis, S. mitis and similar organisms using conventional tests and pyrolysis mass spectrometry.

Numerical taxonomic methods were applied to the results of pyrolysis mass spectrometry (Py-MS) and conventional test reaction patterns (CTRPs) obtained with 46 strains of oral streptococci identified as representative of six species. Of these: Streptococcus gordonii strains formed a single homogeneous well-differentiated cluster both in the Py-MS and CTRP analyses; S. oralis strains were more diverse, forming 2 CTRP and 3 Py-MS clusters; S. crista, S. parasanguis and S. sanguis formed clear, but diverse and poorly differentiated clusters on the basis of CTRPs, and were poorly differentiated in the Py-MS analysis; and S. mitis strains were clearly diverse in both analyses. Peritrichously fimbriate ('tufted') S. mitis strains formed a tight cluster, well differentiated from the type strain in both Py-MS and CTRP analyses, and may represent a previously unrecognised centre of variation.