Classification of oral pigmented anaerobic bacilli by pyrolysis mass spectrometry and biochemical tests.

Clinical (66) and reference (5) strains of pigmented gram-negative anaerobic bacilli, identified as Prevotella intermedia (47), Pr. melaninogenica (1), Pr. corpora (8), Porphyromonas asaccharolyticus (12), P. endodontalis (1) and P. gingivalis (2), were examined by pyrolysis mass spectrometry (PMS) and in conventional tests. Numerical classification based on conventional test reaction patterns (CTRPs) resolved five clusters, four comprising strains identified as Pr. intermedia, Pr. corpora, Pr. melaninogenica, and P. gingivalis respectively, and one comprising strains identified as P. asaccharolyticus and P. endodontalis. Numerical classification based on PMS showed a similar division, with decreasing homogeneity of chemical composition in the order Pr. intermedia, Pr. corpora, P. asaccharolyticus, which agreed with the order of homogeneity in CTRPs. PMS clusters corresponding to the genus Porphyromonas were clearly distinct from those of the genus Prevotella. PMS and CTRP classification disagreed on cluster membership for six strains. PMS identification from blind challenge sets was in agreement with conventional identification for 64 of 67 strains.