During studies of human periodontal disease, a number of bacterial strains were encountered that, on the basis of results of standard biochemical tests, appeared to be PrevoteZla buccah, PrevoteUa denticola, PrevoteUa rnelaninogenica, or Prevoteh loescheii. However, use of the standard biochemical tests, cellular fatty acid analyses, and the polyacrylamide gel electrophoresis patterns of soluble proteins resulted in conflicting identifications of these strains. The results of tests for cellobiose fermentation, inulin fermentation, and pigment production were responsible for most of the discordant results. Cellular fatty acid analyses in which the Microbial Identification System was used did not differentiate these strains from validly described species, even though separate library entries were created for them. DNA reassociation determinations in which the S1 nuclease procedure was used showed that cellobiose fermentation and pigment production are variable among strains of P. melaninogenica and P. denticola and that fermentation of xylan is not a reliable characteristic for differentiating P. buccaZis from PrevoteUa vetoralis. In contrast to previous indications, most strains of P. vemraZis do not ferment xylan. These species can be differentiated by DNA-DNA reassociation and by cellular fatty acid analysis, using the Microbial Identification System, but differentiation by currently described phenotypic characteristics is not reliable. Similarly, P. loescheii and the genetically distinct (but closely related) D1C-20 group cannot be distinguished reliably from each other or from P. veroralis, P. denticola, and P. melaninogenica on the basis of currently described phenotypic tests other than cellular fatty acid composition or, for some species, electrophoretic patterns of soluble whole-cell proteins.Prevotella species are a major portion of the microflora of human gingival crevices in patients with periodontal disease (9). The similarity of the phenotypic characteristics of these species often makes their routine differentiation and identification difficult. A total of 19 strains of phenotypically similar Prevotella (Bacteroides) species were used in this study in an attempt to determine their DNA relatedness and to identify reliable phenotypic characteristics for their differentiation. As a result of these analyses, we propose emended descriptions of Prevotella veroralis, Prevotella denticola, Prevotella melaninogenica (2381 DNA-DNA similarity group that contains the type strain), Prevotella loescheii, and the genetically closely related D1C-20 group (3).
MATERIALS AND METHODSThe strains used in this study are shown in Table 1. Most of these strains were isolated from human gingival or subgingival plaque; the exceptions were P. loescheii VPI 9621, which came from a human cranial abscess, and P. melaninogenica VPI 15087, which came from sputum. Strain VPI D1C-20B was a recent single-colony isolate obtained from the original lyophilized culture of strain D1C-20, and strain VPI 15056 was strain D1C-20 accessioned ...
