Classification of black-pigmented anaerobes by pyrolysis mass spectrometry (PMS) and conventional tests (CTs)

Clinical (66: dental 53; vaginal 4; wound 9) and reference (5*) strains of pigmented Gram-negative anaerobic bacilli were examined in pyrolysis mass spectrometry (PMS) and conventional tests (CTs). The strains were identified in CTs as: Prevotella intermedia (48*); Pr. melaninogenica (1); Pr. corporis (7); Porphyromonas asaccharolytica (12*); P. endodontalis (1*) and P. gingivalis (2*). Numerical classification based on CTs resolved five clusters comprising strains identified as (I) Pr. corporis, (II) Pr. melaninogenica, (III) Pr. intermedia, (IV) P. gingivalis and (V) P. asaccharolytica and P. endodontalis. Numerical classification based on PMS showed a similar division, with decreasing homogeneity in the order Pr. intermedia, Pr. corporis, P. asaccharolytica, in agreement with the ordering of homogeneity for these species in CTs. PMS clusters corresponding the Porphyromonas spp. were clearly distinct from those of Prevotella spp. PMS and CT classifications disagreed on cluster membership for only six of the strains. PMS identification from blind challenge sets agreed with conventional identification for 64 of 67 strains.