Distinction ofPrevotella intermediaandPrevotella nigrescensfrom Endodontic Bacteremia through their Fatty Acid Contents

Dysgonomonas macrotermitis sp. nov., isolated from the hindgut of a fungus-growing termite

A Gram-stain-negative, facultatively anaerobic, non-motile and coccoid- to short-rod-shaped bacterium, designated strain Dys-CH1T, was isolated from the hindgut of a fungus-growing termite Macrotermes barneyi. The optimal pH and cultivation temperature of strain Dys-CH1T were pH 7.2–7.6 and 35–37 °C, respectively. Sequence analysis of 16S rRNA gene showed that Dys-CH1T shared 94.6 % and 90.9 % similarity with Dysgonomonas capnocytophagoides JCM 16697T and Dysgonomonas gadei CCUG 42882T, respectively. Strain Dys-CH1T was found to be different from other species of the genus Dysgonomonas with validly published names with respect to taxonomically important traits, including habitat, biochemical tests, DNA G+C content, bile resistance, fatty-acid composition and susceptibility to antimicrobial agents. On the basis of these characteristics, strain Dys-CH1T represents a novel species of the genus Dysgonomonas for which the name Dysgonomonas macrotermitis sp. nov. is proposed. The type strain is Dys-CH1T ( = JCM 19375T = DSM 27370T).

Ribotyping of bacteria from root canal and blood of patients receiving endodontic therapy

DNA restriction patterns and corresponding ribotypes of 26 bacterial isolates (Propionibacterium acnes, Peptostreptococcus prevotii, Fusobacterium nucleatum, Prevotella intermedia, Prevotella nigrescens, Actinomyces israelii, Streptococcus intermedius, and Streptococcus sanguis) recovered from patients with infected root canals and their peripheral blood, collected during and after endodontic therapy, were examined. Eleven additional reference strains including type strains were also examined. Purified DNA was digested with BglI,EcoRI, and HindIII. Hybridization was carried out with a digoxigenin-labeled cDNA probe obtained by reverse transcription of Escherichia coli 16S + 23S rRNA. Ribotypes of the bacteria recovered from root canal and blood showed identical characteristics within the patients, and differed between the patients. The results were confirmed when the similarity coefficient (S(AB)) of the ribotypes from the isolates were assessed by the Dendron computer-assisted system. These results suggested that the bacteria isolated from the blood originated from the root canal.

Prevotella marshii sp. nov. and Prevotella baroniae sp. nov., isolated from the human oral cavity

Eleven strains of anaerobic Gram-negative bacilli isolated from the human oral cavity were subjected to a comprehensive range of phenotypic and genotypic tests and were found to comprise two homogeneous groups, designated E2 and E4. 16S rRNA gene sequence analysis revealed that members of both groups belonged to the genus Prevotella but were distinct from any species with validly published names. This distinction was confirmed by DNA–DNA hybridization and phenotypic tests. Two novel species are therefore proposed: Prevotella marshii sp. nov. (group E2) and Prevotella baroniae (group E4). Both species are saccharolytic; the end-products of fermentation for P. marshii are acetic, propionic and succinic acids, while P. baroniae produces acetic and succinic acids with minor amounts of isovaleric and isobutyric acids. The G+C content of the DNA of the type strain of Prevotella marshii is 51 mol% and that of Prevotella baroniae is 52 mol%. The type strain for P. marshii is E9.34T (=DSM 16973T=CCUG 50419T) and that for P. baroniae is E9.33T (=DSM 16972T=CCUG 50418T).

Direct quantitative differentiation between Prevotella intermedia and Prevotella nigrescens in clinical specimens

This paper describes a quantitative fluorescent in situ hybridization (FISH) assay for the differential identification of Prevotella intermedia and Prevotella nigrescens in clinical samples, and compares its performance with less discriminatory culture and quantitative immunofluorescence (IF) assays. Fluorescence-labelled oligonucleotide probes directed to specific 16S rRNA sequences of P. intermedia, P. nigrescens, Prevotella pallens and Prevotella denticola were hybridized under stringent conditions with cultured reference strains or plaque samples from deep periodontal pockets. Probe specificity was defined with strains from multiple oral Prevotella species. The lower detection level of the assays was approximately 3x10(3) target cells per ml of plaque-sample suspension. P. intermedia, P. nigrescens, P. pallens and P. denticola were detected in plaques with prevalences of 69, 67, 0 and 28%, respectively. On average, 3.9 x 10(6) P. intermedia, 3.1 x 10(6) P. nigrescens and 5.6 x 10(5) P. denticola cells were counted per positive sample. All three species were found almost exclusively in dense mixed aggregates. Quantitative FISH data agreed satisfactorily with corresponding IF data (r=0.711). Both FISH and IF enumerations of the sum of P. intermedia and P. nigrescens markedly exceeded the c.f.u. counts of black-pigmented colonies in Porphyromonas gingivalis-free cultured subgingival plaques. The results demonstrate the validity of this new assay. Unlike established IF, culture, PCR or checkerboard DNA hybridization assays, this FISH assay differentiates quantitatively between P. intermedia and P. nigrescens, provides visual accuracy control, and offers insights into the spatial distribution of the target cells within a clinical sample.

Anaerobic bacteremia and fungemia in patients undergoing endodontic therapy: an overview

Oral focal infection, a concept neglected for several decades, is a subject of controversy. Recent progress in classification and identification of oral microorganisms has renewed interest in focal infection. The aim of this study was to use phenotypic and genetic methods to trace microorganisms released into the bloodstream during and after endodontic treatment back to their presumed source--the root canal. Microbiological samples were taken from the root canals of 26 patients with asymptomatic apical periodontitis of single-rooted teeth. The blood of the patients was drawn during and 10 minutes after endodontic therapy. Microorganisms in blood were collected after anaerobic lysis filtration and cultured anaerobically on blood agar plates. The phenotypic methods used for characterization and tracing of microorganisms in blood and root canals were: biochemical and antimicrobial susceptibility test, SDS-PAGE of whole-cell soluble proteins, and gas chromatography of cellular fatty acids. Phenotypic data were verified by DNA restriction patterns and corresponding ribotypes of the root canal and blood isolates by using a computer-assisted system fro gel analysis. All root canals contained anaerobic bacteria. The frequency of bacteremia varied from 31% to 54%. The microorganisms from the root canal and blood presented identical phenotype and genetic characteristics within the patients examined. These characteristics differed between patients. The present study demonstrated that endodontic treatment can be the cause of anaerobic bacteremia and fungemia. The phenotypic and genetic methods used appeared valuable for tracing microorganisms in the blood back to their origin.