Analysis of 16S rRNA genes reveals reduced Fusobacterial community diversity when translocating from saliva to GI sites

Fusobacterium nucleatum is a Gram-negative oral commensal anaerobe which has been increasingly implicated in various gastrointestinal (GI) disorders, including inflammatory bowel disease, appendicitis, GI cancers. The oral cavity harbors a diverse group of Fusobacterium, and it is postulated that F. nucleatum in the GI tract originate from the mouth. It is not known, however, if all oral Fusobacterium translocate to the GI sites with equal efficiencies. Therefore, we amplified 16S rRNA genes of F. nucleatum and F. periodonticum, two closely related oral species from matched saliva, gastric aspirates, and colon or ileal pouch aspirates of three patients with inflammatory bowel disease (IBD) and three healthy controls, and saliva alone from seven patients with either active IBD or IBD in remission. The 16S rRNA gene amplicons were cloned, and the DNA sequences determined by Sanger sequencing. The results demonstrate that fusobacterial community composition differs more significantly between the oral and GI sites than between different individuals. The oral communities demonstrate the highest level of variation and have the richest pool of unique sequences, with certain nodes/strains enriched in the GI tract and others diminished during translocation. The gastric and colon/pouch communities exhibit reduced diversity and are more closely related, possibly due to selective pressure in the GI tract. This study elucidates selective translocation of oral fusobacteria to the GI tract. Identification of specific transmissible clones will facilitate risk assessment for developing Fusobacterium-implicated GI disorders.

Involvement of Fusobacterium Species in Oral Cancer Progression: A Literature Review Including Other Types of Cancer

Chronic inflammation caused by infections has been suggested to be one of the most important cause of cancers. It has recently been shown that there is correlation between intestinal bacteria and cancer development including metastasis. As over 700 bacterial species exist in an oral cavity, it has been concerning that bacterial infection may cause oral cancer. However, the role of bacteria regarding tumorigenesis of oral cancer remains unclear. Several papers have shown that Fusobacterium species deriving the oral cavities, especially, play a crucial role for the development of colorectal and esophageal cancer. F. nucleatum is a well-known oral bacterium involved in formation of typical dental plaque on human teeth and causing periodontal diseases. The greatest characteristic of F. nucleatum is its ability to adhere to various bacteria and host cells. Interestingly, F. nucleatum is frequently detected in oral cancer tissues. Moreover, detection of F. nucleatum is correlated with the clinical stage of oral cancer. Although the detailed mechanism is still unclear, Fusobacterium species have been suggested to be associated with cell adhesion, tumorigenesis, epithelial-to-mesenchymal transition, inflammasomes, cell cycle, etc. in oral cancer. In this review, we introduce the reports focused on the association of Fusobacterium species with cancer development and progression including oral, esophageal, and colon cancers.

Fusobacterium pseudoperiodonticum sp. nov., Isolated from the Human Oral Cavity

In the present study, three strains (ChDC F213^T, ChDC F251, and ChDC F267) were classified as novel species of genus Fusobacterium based on average nucleotide identity (ANI) and genome-to-genome distance (GGD) analysis and chemotaxonomic characterization. 16S rDNA sequences of strains ChDC F213^T, ChDC F251, and ChDC F267 were highly similar to that of F. periodonticum ATCC 33693^T (99.6, 99.4, and 99.4%, respectively). ANI and GGD values of the three isolates with F. periodonticum ATCC 33693^T ranged from 92.5 to 92.6% and 47.7 to 48.2%, respectively. Considering that threshold of ANI and GGD values for bacterial species discrimination are 95-96% and 70%, respectively, these results indicate that the three isolates represent a novel Fusobacterium species. DNA G + C contents of the three isolates were 28.0 mol% each. Cellular fatty acid analysis of these strains revealed that C_14:0, C_16:0, and C_16:1 ω6c/C_16:1 ω7c were major fatty acids. Therefore, these three strains are novel species belonging to genus Fusobacterium. Strain ChDC F213^T (= KCOM 1259^T = KCTC 5677^T = JCM 33009^T) is the type strain of a novel species of genus Fusobacterium, for which a name of Fusobacterium pseudoperiodonticum sp. nov. is proposed.

Survey of Oral Microbial Diversity using PCR-based Denaturing Gradient Gel Electrophoresis

Polymicrobial biofilms in the human oral cavity exhibit marked diversity. PCR-based denaturing gradient gel electrophoresis (PCR-DGGE) surveys microbial diversity by displaying PCR-generated 16S rDNA fragments that migrate at different distances, reflecting the differences in the base-pair ( i.e., % G+C) composition of the fragment. This study examined DGGE-generated diversity profiles of cultivable bacteria from individuals with different caries status. Initially, we developed a set of PCR-DGGE running conditions appropriate to oral bacteria. Next, we assessed migration standards from known oral bacterial reference strains. To test the methods, we profiled 20 bacterial saliva samples cultivated from young adults. The study produced a battery of species-specific 16S rDNA amplicons that could be used as a migration distance standard necessary for computer-assisted profile analysis. From the clinical samples, we found a significantly greater diversity of oral microbes in caries-free individuals compared with caries-active individuals ( P = 0.01). These findings suggest thtat a portion of oral microbiota of caries-active individuals may be absent, suppressed, or replaced.

[Quantitation of intestinal Fusobacterium and butyrate- producing bacteria in patients with colorectal adenomas and colorectal cancer]

OBJECTIVE

To compare the abundance of 16S rRNA gene of intestinal Fusobacterium and butyrate-producing bacteria in patients with colorectal adenomas patients and colorectal cancer and to reveal the correlation between the target bacteria and the development of colorectal cancer.

METHODS

Feces were collected from colorectal cancer patients (n=19), colorectal adenomas patients (n=12) and healthy subjects (n=19). Bacteria genome DNA from the fecal samples was used to quantitate the Fusobacterium, two butyrate-producing bacteria Eubacterium rectal, Faecalibacterium prausnitzii and total bacteria by real-time polymerase chain reaction. Then the variation of the target bacteria among different groups were assayed using Mann-Whitney U test.

RESULTS

The abundance of Fusobacterium was significantly higher in colorectal cancer patients than that in healthy subjects (P = 0.000) and colorectal adenomas patients (P = 0.013), and it was significantly higher in colorectal cancer patients than that in colorectal adenomas patients (P = 0.002). F. prausnitzii was significantly lower in colorectal adenomas patients compared to healthy subjects (P = 0.033). The total bacteria count was significantly lower in the colorectal adenomas samples than that in the healthy samples (P = 0.002). There was no significantly difference of E. rectal between the three groups.

CONCLUSIONS

The shifts in the colonic bacterial population may potentially contribute to the development of colorectal cancer.

The personal human oral microbiome obscures the effects of treatment on periodontal disease

Periodontitis is a progressive disease of the periodontium with a complex, polymicrobial etiology. Recent Next-Generation Sequencing (NGS) studies of the microbial diversity associated with periodontitis have revealed strong, community-level differences in bacterial assemblages associated with healthy or diseased periodontal sites. In this study, we used NGS approaches to characterize changes in periodontal pocket bacterial diversity after standard periodontal treatment. Despite consistent changes in the abundance of certain taxa in individuals whose condition improved with treatment, post-treatment samples retained the highest similarity to pre-treatment samples from the same individual. Deeper phylogenetic analysis of periodontal pathogen-containing genera Prevotella and Fusobacterium found both unexpected diversity and differential treatment response among species. Our results highlight how understanding interpersonal variability among microbiomes is necessary for determining how polymicrobial diseases respond to treatment and disturbance.

Fusobacterium equinum possesses a leukotoxin gene and exhibits leukotoxin activity

Fusobacterium equinum, a gram negative, rod-shaped and an obligate anaerobic bacterium is a newly described species. The organism is associated with necrotic infections of the respiratory tract in horses that include necrotizing pneumonia, pleuritis and paraoral infections. The species is closely related to F. necrophorum that causes liver abscesses in cattle and sheep, calf-diphtheria in cattle, and foot-rot in sheep and cattle. Leukotoxin, an exotoxin, is an important virulence factor in bovine strains of F. necrophorum. Our objective was to examine strains (n=10) of F. equinum for leukotoxin (lktA) gene and its toxic effects on equine leukocytes. Southern hybridization and partial DNA sequencing revealed that all the 10 strains had the lktA gene with greater similarities to F. necrophorum subsp. necrophorum. The secreted leukotoxin was detected in the culture supernatant and its biological activity was determined by viability assays with equine polymorphonuclear cells (PMNs) using flow cytometry. While culture supernatants of four strains (E1, E7, E9, and E10) were highly toxic to equine PMNs; strain E5 was moderately toxic and the remaining strains (E2, E3, E4, E6, and E8) were only mildly toxic. Our data indicated that F. equinum isolates had lktA gene and its product was toxic to equine leukocytes. Therefore, leukotoxin may be an important virulence factor in F. equinum infections.

Profiling of bacterial flora in crevices around titanium orthodontic anchor plates

OBJECTIVES

The aims of this study were to characterize the microflora in crevices around titanium orthodontic anchor plates using anaerobic culture and molecular biological techniques for bacterial identification, and to compare the microbial composition between crevices around anchor plates and gingival crevices.

MATERIAL AND METHODS

Samples from crevices around titanium anchor plates and healthy gingival crevices of 17 subjects (aged 20-29) were cultured anaerobically, and isolated bacteria were identified by 16S rRNA sequencing.

RESULTS

The average logarithm colony-forming units/ml were 6.84, 7.51 and 8.88 in healthy anchor plate crevices, inflamed anchor plate crevices and healthy gingival crevices, respectively, indicating that the bacterial density of anchor plate crevices was lower than that of healthy gingival crevices. Of 184 strains isolated from healthy anchor plate crevices of seven subjects, 108 (59%) were anaerobic bacteria, while 73 (40%) were facultative bacteria. Predominant isolates were Gram-negative rods, such as Campylobacter (12%), Fusobacterium (10%) and Selenomonas (10%), and Gram-positive facultative bacteria, such as Actinomyces (17%) and Streptococcus (8.2%). Of 133 strains isolated from inflamed anchor plate crevices of three subjects, 110 (83%) were anaerobic bacteria, while predominant isolates were Gram-negative rods, such as Prevotella (47%), Fusobacterium (33%) and Campylobacter (16%). On the other hand, of 146 strains isolated from healthy gingival crevices of seven subjects, 98 (67%) were facultative bacteria, while 45 (31%) were anaerobic bacteria. Predominant isolates were Gram-positive facultative bacteria, such as Actinomyces (37%) and Streptococcus (20%).

CONCLUSIONS

These results suggest that the environment in crevices around titanium orthodontic anchor plates is anaerobic and supportive of anaerobic growth of bacteria, which may trigger inflammation in the tissue around the plates.

In vitro activity of linezolid against clinical isolates of Fusobacterium spp

OBJECTIVES

Although most susceptibility studies for linezolid have investigated aerobic bacteria, only a few have investigated anaerobe isolates. The aim of the present study was to determine the antibacterial activity of linezolid against a larger sample of clinical isolates of Fusobacterium spp. and to report on the detailed susceptibility, stratified by species.

METHODS

The in vitro susceptibility of 80 clinical isolates of Fusobacterium (Fusobacterium necrophorum, n = 34; Fusobacterium nucleatum, n = 20; Fusobacterium varium, n = 18; Fusobacterium mortiferum; n = 8) was tested and compared with the activity of the older compounds amoxicillin and amoxicillin/clavulanic acid.

RESULTS

The MIC of linezolid ranged from 0.016 to 1.0 mg/L, with the MIC(90) being 0.5 mg/L. The highest MIC obtained for linezolid (1.0 mg/L) was measured for an F. varium isolate. The MIC(90) for both, amoxicillin (range: 0.016-0.75 mg/L) and amoxicillin/clavulanic acid (range: 0.047-0.75 mg/L), was 0.5 mg/L. Overall, no resistant strains were found in the study.

CONCLUSIONS

Compared with amoxicillin and amoxicillin/clavulanic acid, linezolid was less active against F. necrophorum (MIC(90) 0.25 mg/L) and F. nucleatum (MIC(90) 0.25 mg/L), equally active against F. varium (MIC(90) 0.75 mg/L) and slightly more active against F. mortiferum (MIC(90) 0.19 mg/L).

Molecular analysis of Filifactor alocis, Tannerella forsythia, and treponema denticola associated with primary endodontic infections and failed endodontic treatment

The aim of this study was to investigate the presence of strict anaerobes such as Filifactor alocis, Tannerella forsythia, and Treponema denticola in primary and secondary root-infected canals with periapical lesions by molecular analysis and the association of these species with specific endodontic signs and symptoms. Microbial samples were taken from 100 root canals, 50 with necrotic pulp tissues (NPT, primary infection), and 50 with failed endodontic treatment (FET, secondary infection). DNA was extracted from the samples, which were analyzed for the presence of three endodontic pathogens using species-specific primers and PCR. F. alocis were isolated from 23 canals with NPT and 12 canals with FET; T. forsythia from 12 canals with NPT and three canals with FET; T. denticola from 19 canals with NPT and 12 canals with TEP. Suggested associations were found between primary infection and the presence of F. alocis and T. forsythia (both p < 0.05). In particular, associations were found between: pain and F. alocis; swelling and F. alocis; tenderness to percussion and T. forsythia; mobility and T. forsythia and T. denticola; wet canals and F. alocis, T. forsythia, and T. denticola; purulent exsudate and F. alocis, T. forsythia and T. denticola; abscess and F. alocis, T. forsythia, and T. denticola (all p < 0.05). The findings of this study indicated that F. alocis, T. forsythia, and T. denticola seem to be associated with endodontic signs and symptoms. Additionally, F. alocis and T. forsythia were detected more frequently in teeth with necrotic pulp than in teeth with failing endodontic treatment.

Microbial diversity in coastal subsurface sediments: a cultivation approach using various electron acceptors and substrate gradients

Microbial communities in coastal subsurface sediments are scarcely investigated and have escaped attention so far. But since they are likely to play an important role in biogeochemical cycles, knowledge of their composition and ecological adaptations is important. Microbial communities in tidal sediments were investigated along the geochemical gradients from the surface down to a depth of 5.5 m. Most-probable-number (MPN) series were prepared with a variety of different carbon substrates, each at a low concentration, in combination with different electron acceptors such as iron and manganese oxides. These achieved remarkably high cultivation efficiencies (up to 23% of the total cell counts) along the upper 200 cm. In the deeper sediment layers, MPN counts dropped significantly. Parallel to the liquid enrichment cultures in the MPN series, gradient cultures with embedded sediment subcores were prepared as an additional enrichment approach. In total, 112 pure cultures were isolated; they could be grouped into 53 different operational taxonomic units (OTU). The isolates belonged to the Proteobacteria, "Bacteroidetes," "Fusobacteria," Actinobacteria, and "Firmicutes." Each cultivation approach yielded a specific set of isolates that in general were restricted to this single isolation procedure. Analysis of the enrichment cultures by PCR and denaturing gradient gel electrophoresis revealed an even higher diversity in the primary enrichments that was only partially reflected by the culture collection. The majority of the isolates grew well under anoxic conditions, by fermentation, or by anaerobic respiration with nitrate, sulfate, ferrihydrite, or manganese oxides as electron acceptors.

Identification and localization of extraradicular biofilm-forming bacteria associated with refractory endodontic pathogens

Bacterial biofilms have been found to develop on root surfaces outside the apical foramen and be associated with refractory periapical periodontitis. However, it is unknown which bacterial species form extraradicular biofilms. The present study aimed to investigate the identity and localization of bacteria in human extraradicular biofilms. Twenty extraradicular biofilms, used to identify bacteria using a PCR-based 16S rRNA gene assay, and seven root-tips, used to observe immunohistochemical localization of three selected bacterial species, were taken from 27 patients with refractory periapical periodontitis. Bacterial DNA was detected from 14 of the 20 samples, and 113 bacterial species were isolated. Fusobacterium nucleatum (14 of 14), Porphyromonas gingivalis (12 of 14), and Tannellera forsythensis (8 of 14) were frequently detected. Unidentified and uncultured bacterial DNA was also detected in 11 of the 14 samples in which DNA was detected. In the biofilms, P. gingivalis was immunohistochemically detected in all parts of the extraradicular biofilms. Positive reactions to anti-F. nucleatum and anti-T. forsythensis sera were found at specific portions of the biofilm. These findings suggested that P. gingivalis, T. forsythensis, and F. nucleatum were associated with extraradicular biofilm formation and refractory periapical periodontitis.

Genetic determinant of intrinsic quinolone resistance in Fusobacterium canifelinum

Fourteen fluoroquinolone-resistant fusobacterial strains, originating from cats or dogs, were characterized by sequencing of the 16S-23S and 16S rRNA genes and DNA-DNA hybridization and were described as a new species, Fusobacterium canifelinum. All of the strains are intrinsically resistant (MIC, >4 g/ml) to levofloxacin and other fluoroquinolones. Compared to the quinolone resistance-determining region (gyrA) of the susceptible relative F. nucleatum, we found that Ser79 was replaced with leucine and Gly83 was replaced with arginine.

Fusobacterium canifelinum sp. nov., from the oral cavity of cats and dogs

Fourteen strains of Gram-negative, anaerobic, fluoroquinolone-resistant, non-sporulating rods were isolated from various infections in cats and dogs, as well as from wounds in humans after cat- or dog-bites. These strains were characterized by sequencing of the 16S-23S rDNA internal transcribed spacer (ITS) regions, 16S rDNA, DNA-DNA hybridization, phylogenetic analysis, and phenotypic tests. The results indicate that the novel strains belong to a distinct species, closely related to Fusobacterium nucleatum. The species Fusobacterium canifelinum sp. nov. is proposed, with strain ATCC BAA 689T as the type strain.

Effects of periodontitis and smoking on the microbiota of oral mucous membranes and saliva in systemically healthy subjects

BACKGROUND/AIM

To examine the differences in the proportions of 40 bacterial species in samples from eight oral soft-tissue surfaces and saliva in systemically healthy adult subjects with and without periodontitis and in smokers and nonsmokers.

METHODS

Saliva and microbial samples were taken from eight oral soft-tissue surfaces in 229 systemically healthy subjects stratified by periodontal and smoking status. Subjects included 84 periodontally healthy and 145 periodontitis individuals. Of these, there were 182 nonsmokers and 47 smokers. Soft-tissue samples were taken using a "buccal brush" and saliva was taken by expectoration. All samples were individually evaluated for their content of 40 bacterial species using checkerboard DNA-DNA hybridization. The percentage of total DNA probe count was determined for each species at each sample location and averaged across subjects. The significance of differences among the proportions of the 40 test species at different sample locations was sought in these populations using the Kruskall-Wallis test and adjusted for multiple comparisons.

RESULTS

When stratified for periodontal status or smoking status, microbial profiles at most sites did not differ significantly. Generally, periodontal pathogens were found at higher levels on the soft tissues of periodontitis subjects than in periodontally healthy subjects, and at higher levels in smokers than nonsmokers. Few significant differences were found, although trends in the populations were noted.

CONCLUSIONS

Small differences in the proportions of bacterial species were observed on soft tissues and in saliva comparing periodontally healthy and periodontitis subjects. Somewhat greater differences between smokers and nonsmokers were found; however, these were not statistically significant.

Polymerase chain reaction–based analysis of microorganisms associated with failed endodontic treatment

OBJECTIVE

In this study, we aimed to investigate the occurrence of several microbial species in cases of failed endodontic therapy by means of the polymerase chain reaction (PCR). Study design Root canal samples were taken from 22 root-filled teeth with persistent periradicular lesions selected for re-treatment. DNA was extracted from the samples and analyzed for the presence of 19 microbial taxa by using the polymerase chain reaction.

RESULTS

All samples were positive for at least 1 of the target microbial species. Enterococcus faecalis was the most prevalent species-detected in 77% of the cases. The other most prevalent species were Pseudoramibacter alactolyticus (52%), Propionibacterium propionicum (52%), Dialister pneumosintes (48%), and Filifactor alocis (48%). Candida albicans was found in 9% of the samples. The mean number of species in samples filled up to 2 mm short of the radiographic apex was 3 (range, 1-5), whereas cases in which the filling was greater than 2 mm from the apex yielded a mean of 5 species (range, 2-11). This difference was statistically significant (P <.05).

CONCLUSIONS

Microorganisms occurred in all cases of root-filled teeth associated with periradicular lesions, which lends strong support to the assertion that treatment failures are rather of infectious etiology, caused by persistent or secondary intraradicular infections. E faecalis was the most prevalent species, followed by 4 other anaerobic species: P. alactolyticus, P. propionicum, D. pneumosintes, and F. alocis. All examined samples harbored at least 1 of the following gram-positive bacterial species: E. faecalis, P. alactolyticus, or P. propionicum.

Distribution of Periodontal Pathogens in Korean Aggressive Periodontitis

BACKGROUND

Microbial associations in aggressive periodontitis versus different ethnic origins are substantially unknown. We undertook this study to determine the prevalence of seven putative periodontopathogens in Korean patients and to evaluate microbial differences in localized and generalized aggressive periodontitis patients.

METHODS

Thirty-nine aggressive periodontitis patients between 20 and 35 years old (24 males and 15 females; mean age 29.6 years) were selected according to clinical criteria. The patients were subclassified into 17 localized and 22 generalized aggressive periodontitis patients. In each of the 39 individuals, subgingival plaque samples were collected from four diseased teeth (> or = 6 mm probing depth, 156 sites) and one healthy site (< or = 3 mm probing depth, 39 sites). Polymerase chain reaction (PCR) of the 16S ribosomal RNA gene fragments (about 530 bp) of plaque bacteria and their subsequent detection by dot-blot hybridization using specific oligonucleotide probes were performed to determine the presence of seven periodontopathogens.

RESULTS

The prevalences were 75% for Actinobacillus actinomycetemcomitans, 94.2% for Tannerella forsythensis (formerly Bacteroides forsythus), 99.4% for Fusobacterium sp., 85.9% for Micromonas micros (formerly Peptostreptococcus micros), 96.8% for Porphyromonas gingivalis, 78.8% for Prevotella intermedia, and 96.8% for Treponema sp. The prevalences of these bacteria were significantly higher in diseased sites than in healthy sites. Logistic regression analysis showed that P. intermedia was more significantly associated with generalized aggressive periodontitis than the localized form, with an odds ratio of 3.28 (95% confidence interval 1.26-8.56, P = 0.015).

CONCLUSIONS

Our results demonstrate that the seven periodontal pathogens analyzed are strongly associated with Korean aggressive periodontitis. In particular, P. intermedia are more significantly associated with generalized aggressive periodontitis, a more severe and progressive form, than with localized aggressive periodontitis.

Oligonucleotide probes that detect quantitatively significant groups of butyrate-producing bacteria in human feces

16S rRNA-targeted oligonucleotide probes were designed for butyrate-producing bacteria from human feces. Three new cluster-specific probes detected bacteria related to Roseburia intestinalis, Faecalibacterium prausnitzii, and Eubacterium hallii at mean populations of 2.3, 3.8, and 0.6%, respectively, in samples from 10 individuals. Additional species-level probes accounted for no more than 1%, with a mean of 7.7%, of the total human fecal microbiota identified as butyrate producers in this study. Bacteria related to E. hallii and the genera Roseburia and Faecalibacterium are therefore among the most abundant known butyrate-producing bacteria in human feces.

Aetiology of ovine footrot in the Portuguese region of Alto Alentejo

In this work, we found it appropriate to carry out a study directed towards isolating and identifying the entailed microorganisms which trigger off footrot in sheep, placing special emphasis on the serotipification of the different Dichelobacter nodosus species. With this goal in mind four flocks from the Portuguese region of 'Alto Alentejo' were selected, all of them had one common feature: their main health problem was ovine footrot. We also set out to determine the elastolitic capacity of isolated strict-anaerobic bacteria, in order to be able to clarify the direct involvement of these microorganisms in the outbreak of this infectious process.

Growth requirements and fermentation products of Fusobacterium prausnitzii, and a proposal to reclassify it as Faecalibacterium prausnitzii gen. nov., comb. nov

Two newly isolated strains of obligately anaerobic bacteria from human faeces are shown here to be related to Fusobacterium prausnitzii, which is regarded as one of the most abundant colonizers of the human colon. These strains, along with Fusobacterium prausnitzii ATCC 27768(T) and 27766, are non-motile and produce butyrate, formate and lactate, but not hydrogen as fermentation products. A new finding is that all four strains produce D-lactate, but not L-lactate. The strains have a requirement for acetate in the growth medium and this may account for the previously reported requirement for rumen fluid. The DNA G+C content of the four strains is 47-57 mol%. Together with phylogenetic analysis based on 16S rRNA sequencing, this establishes that Fusobacterium prausnitzii strains are only distantly related to Fusobacterium sensu stricto and are more closely related to members of Clostridium cluster IV (the Clostridium leptum group). It is proposed that a new genus, Faecalibacterium gen. nov. be created; this genus should include Faecalibacterium prausnitzii gen. nov., comb. nov. ATCC 27768(T) (= NCIMB 13872(T)) (formerly Fusobacterium prausnitzii) as the type species together with ATCC 27766 and the newly isolated strains A2-165 and L2-6.

Stress and the periodontal diseases: effects of catecholamines on the growth of periodontal bacteria in vitro

Microorganisms possess the ability to recognize hormones within the host and utilize them to adapt to their surroundings. Noradrenaline and adrenaline, which are released during human stress responses, may act as environmental cues to alter the growth of individual organisms within subgingival biofilms. The aims of this study were to modify, for anaerobic culture, existing methodology used in determining microorganism catecholamine responses and to investigate the growth responses to noradrenaline and adrenaline of 43 microorganisms found within subgingival microbial complexes. We established initial inocula for each strain using anaerobic culture, re-inoculated into a minimal serum-based medium and grown anaerobically at 35 degrees C. We assessed organism growth by optical density (OD(600nm)) readings, with test and control cultures performed in triplicate. Test cultures were supplemented with 50 microm noradrenaline or 100 microm adrenaline. We observed significant growth effects for supplementation with noradrenaline (20 species responding positively) and adrenaline (27 species responding positively), with differences in growth response observed within bacterial species and within and between microbial complexes. The most pronounced positive growth effects of noradrenaline were demonstrated in Actinomyces naeslundii (+ 49.4%), Actinomyces gerenscseriae (+ 57.2%), Eikenella corrodens (+ 143.3%) and Campylobacter gracilis (+ 79.9%). We also observed inhibitory effects of noradrenaline supplementation for Porphyromonas gingivalis (- 11.9%) and Bacteroides forsythus (- 22.2%). Responses to adrenaline tended to mirror the responses seen with noradrenaline. Individual organisms from different microbial complexes vary in their in vitro growth responses to noradrenaline and adrenaline. Such variation may influence the in vivo composition of the subgingival biofilm in response to stress-induced changes in local catecholamine levels and play a significant role in the aetiology and pathogenesis of the periodontal diseases.

Update on the taxonomy and clinical aspects of the genus fusobacterium

The genus Fusobacterium currently includes 13 species. Fusobacterium nucleatum, the most frequently encountered species in humans, is heterogeneous and currently includes 5 subspecies. A potentially new subspecies of F. nucleatum that is intrinsically quinolone-resistant and phylogenetically separate from the other 5 subspecies has been identified from dog and cat oral flora. Two subspecies have been described for Fusobacterium necrophorum, and a new species, Fusobacterium equinum, which is related to F. necrophorum, has been described from horse oral flora. Additional molecular studies have characterized Fusobacterium ulcerans as separate from the phenotypically similar Fusobacterium mortiferum and Fusobacterium varium. Fusobacterium sulci and Fusobacterium alocis have been reclassified as Eubacterium sulci and Filifactor alocis, respectively. Fusobacterium prausnitzii is phylogenetically related to the Eubacterium-like organisms and will likely be reclassified in the future. The status of the remaining species is unchanged.

Recent taxonomic changes and terminology update of clinically significant anaerobic gram-negative bacteria (excluding spirochetes)

Because of access to 16S rDNA sequencing, changes in the taxonomy and nomenclature of anaerobic gram-negative bacteria have occurred lately. New genera and species have been described, and existing taxa have been reclassified. The present article compiles a list of clinically relevant anaerobes and provides synonyms as well as the old nomenclature used for these bacteria. Although names and classifications of anaerobic bacteria are changing quickly, it is important to keep track of new bacterial names to work toward better description and recognition of bacterium-disease associations.

16S-23S rDNA internal transcribed spacer sequences for analysis of the phylogenetic relationships among species of the genus Fusobacterium

The 16S-23S rDNA internal transcribed spacer (ITS) regions of all currently defined Fusobacterium species and related taxa such as Leptotrichia buccalis, Sebaldella termitidis and Streptobacillus moniliformans, were analysed to examine inter- and intraspecies as well as subspecies relationships. For the ITS-amplification, a new eubacterial universal primer pair was designed and used. The majority of the Fusobacterium strains, along with L. buccalis showed one major, and two to three weaker, distinct bands (short and long versions) with lengths of 800-830 bp and 1000-1100 bp. Nevertheless, six other patterns were also found within the genus Fusobacterium, demonstrating its heterogeneity. The ITS region was sequenced and found to consist both of conserved motifs, which functioned as a framework for alignment, and of variable sites, which provided high phylogenetic resolution. Analyses of the ITS-DNA sequences and ITS relative length (short version) allowed species and subspecies differentiation in most cases. The results confirmed the strikingly distant relationship between Fusobacterium prausnitzii and the genus Fusobacterium. Fusobacterium nucleatum subspecies, along with Fusobacterium naviforme, Fusobacterium simiae and Fusobacterium periodonticum, formed a cluster with an inherently high potential for diversification. Other clusters were formed by Fusobacterium necrophorum subspecies with Fusobacterium gonidaformans and by Fusobacterium varium with Fusobacterium mortiferum and Fusobacterium ulcerans. Fusobacterium russii as well as Fusobacterium perfoetens formed separate branches. Fusobacterium necrophorum subspp. necrophorum and funduliforme on the one hand, and Fusobacterium varium and Fusobacterium mortiferum on the other, were found to be very similar, even at the high-resolution ITS level.

Comparison of the 16S-23S rRNA intergenic spacer regions between Fusobacterium varium and "Fusobacterium pseudonecrophorum" strains

The 16S-23S rRNA intergenic spacer regions (ISRs) of five strains of "Fusobacterium pseudonecrophorum" which had been proposed as a new species, were compared with those of F. varium ATCC 8501T. All the strains of "F. pseudonecrophorum" exhibited of sequence similarities of 97.7% to 100% to the strain of F. varium in their 16S-23S rRNA ISR sequences. This indicates that the strains of "F. pseudonecrophorum" and the type strain of F. varium are identical at the species level.

The effects of an immediately pre-surgical chlorhexidine oral rinse on the bacterial contaminants of bone debris collected during dental implant surgery

Dental implant surgery produces bone debris that can be used in the "simultaneous augmentation" technique. Although this debris is contaminated with oral bacteria, a stringent aspiration protocol has been shown to reduce the levels of contamination. Chlorhexidine mouthrinse is a well-proven antibacterial rinse that has been shown to reduce infectious complications associated with dental implants. This study examined the effect of pre-operative rinsing with a 0.1% chlorhexidine digluconate mouthrinse on the bacterial contaminants present in collected bone debris bone (CBD). Twenty partially edentate patients were randomly allocated into equal groups and underwent bone collection using the Frios Bone Collector (FBC) during the insertion of two dental implants. In group T a pre-operative chlorhexidine rinse was used, whilst in group C sterile water was used. For both groups, a stringent bone collection protocol was used. Bone samples were immediately transported for microbial analysis. Colonial and microscopic morphology, gaseous requirements and identification kits were utilised for identification of the isolated microbes. Thirty-nine species were identified including a number associated with disease, in particular Actinomyces odontolyticus, Clostridium bifermentans, Prevotella intermedia, and Propionibacterium propionicum. Samples from group T (chlorhexidine mouthrinse) yielded significantly fewer organisms (P < 0.001) than in group C (sterile water mouthrinse). Gram-positive cocci dominated the isolates from both groups. It is concluded that if bone debris is to be used for the purpose of immediate simultaneous augmentation, a preoperative chlorhexidine mouthrinse should be utilised in conjunction with a stringent aspiration protocol to reduce further the bacterial contamination of CBD.

Molecular epidemiology and association of putative pathogens in root canal infection

The purpose of this study was to investigate the epidemiology of putative pathogens in root canals with apical periodontitis and to determine the associations among the putative pathogens. Eighteen symptomatic and 20 asymptomatic teeth from 36 subjects were studied. This research was performed with polymerase chain reaction and hybridization using rRNA-based oligonucleotide probes. The most frequently found species was Fusobacterium sp. (68.4%), followed by Peptostreptococcus micros (44.7%) and Porphyromonas gingivalis (26.3%). Sixteen teeth (42.1%) contained one or more species of the selected black-pigmented bacteria. Bacteroides forsythus and Treponema sp. were detected in 8 teeth and 6 teeth, respectively. Among the analyzed bacteria, significant relationships were shown in the combination of B. forsythus/P. gingivalis and Treponema sp./P. gingivalis. There was no significant association between any bacteria and any symptoms.

Fusobacterial infections: an underestimated threat

The involvement of fusobacteria in a wide range of human and animal infection has long been recognised. Slow-growing anaerobes, often in polymicrobial culture, they are not always identified but are present mainly in the oropharynx, from where they are bloodborne to other sites or aspirated into the lung. Fusobacterium nucleatum is commonly found in periodontal disease and produces tissue irritants such as butyric acid, proteases and cytokines. It has strong adhesive properties due to the presence of lectins, and these outer-membrane proteins mediate adhesion to epithelia and tooth surfaces, and coagglutination with other suspected pathogens. F. necrophorum may cause necrotising tonsillitis and septicaemia, leading to the spread of infection and the development of abscesses in the lung and brain--a form of Lemierre's syndrome. Calf diphtheria, foot rot and other infections in animals are well defined, with the pathogenic mechanisms involving leucotoxins, endotoxins and adhesins. A foul smell produced by butyric acid and other metabolic products is common to all fusobacterial infections. Identification using simple tests is within the scope of most laboratories.

Necrobacillosis in free-living male European bison in Poland

In the Bialowieza Primeval Forest (Poland) a chronic disease of the external genital organs has been observed in free-living male European bison (Bison bonasus) since 1980. Investigations on this disease started in the late 1980s. The most striking findings are necrotic and ulcerative lesions of the prepuce and penis of bison aged from 6 mo to >10 yr. Histologic examination of tissue samples from the prepuce of six bison (9-mo- to 8-yr-old), and from the penis of two bison (3- and 8-yr-old), were characteristic of necrobacillosis. Masses of slender, Gram-negative, rod-like or filamentous bacteria occurred in necrotic tissue. At the periphery of necrotic tissue filamentous bacteria were often arranged in large clusters and strands that advanced towards healthy tissue. Immunolabeling and electron microscopy also suggest that these organisms are Fusobacterium sp.

Isolation of fusobacteria from the oral cavities of malnourished Nigerian children living in agricultural and herding villages

A previous study demonstrated the presence and possible involvement of Fusobacterium necrophorum in the pathogenesis of noma lesions of children living in agricultural and herding villages in northwestern Nigeria. In order to determine if F. necrophorum was part of the oral flora of malnourished children with no noma lesions, a study of the fusobacteria present in the oral cavities of 30 children, 2-6 years of age in Sokoto State, was undertaken. Swabs taken of the oral cavity were cultured on selective fusobacteria medium using conventional anaerobic microbiological techniques. F. nucleatum was recovered from each child and F. necrophorum was isolated from the oral cavity of only one child. The presence of F. nucleatum and the lack of F. necrophorum, except in one case, suggests that the latter is not normal flora in the children at risk for noma. F. necrophorum, a putative trigger organism for noma may gain a foothold only when certain staging conditions (i.e., lowered host resistance and/or oral lesion) are present.

Direct analysis of genes encoding 16S rRNA from complex communities reveals many novel molecular species within the human gut

The human intestinal tract harbors a complex microbial ecosystem which plays a key role in nutrition and health. Although this microbiota has been studied in great detail by culture techniques, microscopic counts on human feces suggest that 60 to 80% of the observable bacteria cannot be cultivated. Using comparative analysis of cloned 16S rRNA gene (rDNA) sequences, we have investigated the bacterial diversity (both cultivated and noncultivated bacteria) within an adult-male fecal sample. The 284 clones obtained from 10-cycle PCR were classified into 82 molecular species (at least 98% similarity). Three phylogenetic groups contained 95% of the clones: the Bacteroides group, the Clostridium coccoides group, and the Clostridium leptum subgroup. The remaining clones were distributed among a variety of phylogenetic clusters. Only 24% of the molecular species recovered corresponded to described organisms (those whose sequences were available in public databases), and all of these were established members of the dominant human fecal flora (e.g., Bacteroides thetaiotaomicron, Fusobacterium prausnitzii, and Eubacterium rectale). However, the majority of generated rDNA sequences (76%) did not correspond to known organisms and clearly derived from hitherto unknown species within this human gut microflora.

Phylogenetic analysis of Fusobacterium alocis and Fusobacterium sulci based on 16S rRNA gene sequences: proposal of Filifactor alocis (Cato, Moore and Moore) comb. nov. and Eubacterium sulci (Cato, Moore and Moore) comb. nov

Genes encoding the 16S rRNA of Fusobacterium alocis ATCC 35896T and Fusobacterium sulci ATCC 35585T were sequenced. These sequences did not have any affinity with the 16S rRNA gene sequences of members of the genus Fusobacterium. Fusobacterium alocis ATCC 35896T and Fusobacterium sulci ATCC 35585T belonged to Clostridium cluster XI; the species most closely related to these strains were Filifactor villosus NCTC 11220T and Eubacterium infirmum W1471, respectively. Two new combinations are proposed: Filifactor alocis (Cato, Moore and Moore) comb. nov. (type strain ATCC 35896T) and Eubacterium sulci (Cato, Moore and Moore) comb. nov. (type strain ATCC 35585T).

Development of a PCR test for identification of Haemophilus somnus in pure and mixed cultures

Based on the 16S rRNA sequences of a collection of well-characterized strains of Haemophilus somnus a set of primers was selected as candidates for a species-specific PCR test. All investigated H. somnus strains were found positive in the test, including 12 strains earlier found to represent H. somnus by DNA-DNA hybridization as well as representatives of the 16 ribotypes previously described within this species. The specificity of the test was evaluated on a broad collection of strains within the family Pasteurellaceae and on other Gram positive and negative species. None of these strains gave rise to an amplicon in the PCR test. The performance of the test on mixed cultures was evaluated by adding P. multocida to serial dilutions of H. somnus and incubating the agarplates for 1 and 2 days. This showed that the PCR test applied to the harvest from an agarplate can be expected to detect a single colony of H. somnus in the presence of 10(9) CFU of P. multocida even after 2 days of incubation. In conclusion, the present PCR test has been shown to represent a specific test for identification of H. somnus both in pure and mixed cultures. It represents a quick, sensitive and reliable method for identification of bacteria belonging to this phenotypically heterogeneous and often slow growing species.

Subgingival microflora associated with nifedipine-induced gingival overgrowth

The purpose of this study was to examine the composition of subgingival plaque of 140 periodontal lesions in 35 patients with cardiovascular disorders who were administered nifedipine and manifested nifedipine-induced gingival overgrowth (GO). Age was inversely associated with the GO. Plaque index and bleeding index showed a significant association with GO, while nifedipine dosage and duration of nifedipine therapy were not found to be significant predictors of GO. The gingival inflammation as expressed in the logistic regression model by the interaction term color x tone was found to be significantly associated with the GO. Statistically significant differences between the groups of comparable probing depth and different degrees of GO were detected for Propionibacterium acnes, Capnocytophaga gingivalis, Capnocytophaga ochracea, Capnocytophaga sputigena, Bacteroides gracilis, Fusobacterium mortiferum, Fusobacterium nucleatum, Fusobacterium varium and Selenomonas sputigena in deep and enlarged lesions. Significantly more frequently isolated were the bacterial species Eubacterium alactolyticum, Campylobacter concisus, C. gingivalis, C. ochracea, C. sputigena, F. mortiferum, F. nucleatum, and F. varium from the more enlarged lesions (GO >3).

Ribotyping to compare Fusobacterium necrophorum isolates from bovine liver abscesses, ruminal walls, and ruminal contents

Restriction fragment length polymorphism analysis of rRNA genes was employed to genetically compare Fusobacterium necrophorum subsp. necrophorum and F. necrophorum subsp. funduliforme isolates from multiple abscesses of the same liver and isolates from liver abscesses, the ruminal wall, and ruminal contents from the same animal. Four livers with multiple abscesses and samples of ruminal contents, ruminal walls, and liver abscesses were collected from 11 cattle at slaughter. F. necrophorum was isolated from all liver abscesses, nine ruminal walls, and six ruminal content samples. Chromosomal DNA of the isolates was extracted and single or double digested with restriction endonucleases (EcoRI, EcoRV, SalI, and HaeIII); then restriction fragments were hybridized with a digoxigenin-labeled cDNA probe transcribed from a mixture of 16S and 23S rRNAs from Escherichia coli. EcoRI alone or in combination with EcoRV yielded the most discriminating ribopatterns for comparison. Within the subspecies multiple isolates from the same liver were indistinguishable based on the ribopattern obtained with EcoRI. The hybridization patterns of liver abscess isolates were concordant with those of the corresponding isolates from ruminal walls in eight of nine sets of samples. None of the six ruminal content isolates matched either the liver abscess isolates or the ruminal wall isolates. The genetic similarity between the isolates from liver abscesses and ruminal walls supports the hypothesis that F. necrophorum isolates of liver abscesses originate from the rumen.

Endopeptidase activities of selected Porphyromonas spp., Prevotella spp. and Fusobacterium spp. of oral and non-oral origin

The ability of three Porphyromonas spp., seven Prevotella spp., seven Fusobacterium spp. and two related Bacteroides spp. (B. levii and B. macacae) to degrade an extensive range of synthetic endo-, amino- and diamino peptidase substrates linked to the fluorescent leaving group 7-amido-4-methylcoumarin (NHMec) was investigated. Many more species than was previously recognized exhibited peptidase activities, albeit at lower levels than those already described for Porphyromonas gingivalis. Detection of chymotrypsin-like activity was dependent on which of three NHMec-linked substrates was used, but all species exhibited degradative activity with at least one of these substrates. Elastase-like activity was detected in all species though not all species reacted with each of the elastase substrates. Glycylprolyl peptidase activity was detected in all of the species tested with the exception of F. mortiferum, F. gonidiaformans, F. naviforme and F. necrophorum. While the detection of peptidase activities does not appear to be useful for the differentiation of species within the genera Bacteroides and Prevotella, its ability to differentiate species of the genus Porphyromonas or Fusobacterium warrants further investigation.

[The study on SDS-PAGE technic classification of the whole protein of oral bacteria]

Oral flora was classificated by SDS-PAGE combined with Comassie blue staining and silver staining. The results showed that each species of the test oral bacteria expressed its specific electrophorectic protein pattern, the way of sample preparation, staining did not change the protein pattern. This indicated that SDS-PAGE could be used to classificate oral flora. The protein pattern was more obvious among the genus than that of within the genus. This showed that different relationship was among the bacteria.

Phylogenetic analysis of Fusobacterium prausnitzii based upon the 16S rRNA gene sequence and PCR confirmation

In order to develop a PCR method to detect Fusobacterium prausnitzii in human feces and to clarify the phylogenetic position of this species, its 16S rRNA gene sequence was determined. The sequence described in this paper is different from the 16S rRNA gene sequence is specific for F. prausnitzii, and the results of this assay confirmed that F. prausnitzii is the most common species in human feces. However, a PCR assay based on the original GenBank sequence was negative when it was performed with two strains of F. prausnitzii obtained from the American Type Culture Collection. A phylogenetic tree based on the new 16S rRNA gene sequence was constructed. On this tree F. prausnitzii was not a member of the Fusobacterium group but was closer to some Eubacterium spp. and located between Clostridium "clusters III and IV" (M.D. Collins, P.A. Lawson, A. Willems, J.J. Cordoba, J. Fernandez-Garayzabal, P. Garcia, J. Cai, H. Hippe, and J.A.E. Farrow, Int. J. Syst. Bacteriol. 44:812-826, 1994).

Fusobacterial infections in children

A total of 243 strains of Fusobacteria species was recovered from 226 of 1399 (16%) specimens obtained from 213 children. The strains included 65 (27%) Fusobacterium sp., 144 (59%) Fusobacterium nucleatum, 25 (10%) Fusobacterium necrophorum, five (2%) Fusobacterium varium, three (1%) Fusobacterium mortiferum, and one (0.4%) Fusobacterium gonidiaformans. Most Fusobacteria species were recovered from patients with abscesses (100), aspiration pneumonia (24), paronychia (15), bites (14), chronic sinusitis (ten), chronic otitis media (nine), and osteomyelitis (eight). Predisposing conditions were noted in 32 (15%) of the cases. These included immunodeficiency in nine (4%), steroid therapy in eight (4%), previous surgery in six (3%), diabetes in six (3%) and malignant neoplasms in five (2%). Fusobacteria sp. was the only isolate in 16 (8%) instances while mixed infections were encountered in 197 (92%) patients. The organisms most commonly isolated with Fusobacteria sp. were anaerobic cocci (155), pigmented Prevotella sp. and Porphyromonas sp. (95), Bacteroides fragilis group (80), Escherichia coli (43) and Bacteroides sp. (39). Most strains of B. fragilis group and E. coli were recovered from intra-abdominal infections and skin and soft tissue infections proximal to the rectal area. Most pigmented Prevotella sp. and Porphyromonas sp. were recovered from oropharyngeal and pulmonary sites and from sites around the head and neck. Antimicrobial therapy was administered to all patients; surgical drainage was performed in 85 (40%). All patients, except two who died, recovered. These findings illustrate the prevalence of Fusobacteria sp. associated with infections in children.

Characterization, distribution, and microbiological associations of Fusobacterium spp. in clinical specimens of animal origin

During the years from 1984 through 1991, 1,067 specimens from canine, equine, exotic, feline, porcine, and ruminant animal sources were found to contain members of the genus Fusobacterium: The most common sites or conditions from which members of this genus were isolated were abscesses, the respiratory tract, and pleural and peritoneal cavities. Most specimens contained a single Fusobacterium species. The most commonly isolated species was Fusobacterium necrophorum. Almost all of the specimens contained other obligate anaerobes together with facultative and obligate aerobes. The identities of the other isolates depended upon the species of animal from which the sample was obtained.

Fusobacteria: new taxonomy and related diseases

Fusobacteria are anaerobic gram-negative bacilli. Since the first reports in the late nineteenth century, various names have been applied to these organisms, sometimes with the same name being applied to different species. More recently, not only have there been changes to the nomenclature, but also attempts to differentiate between species which are believed to be either pathogenic or commensal or both. Because of their asaccharolytic nature, and a general paucity of positive results in routine biochemical tests, laboratory identification of the fusobacteria has been difficult. However, the application of novel molecular biological techniques to taxonomy has established a number of new species, together with the subspeciation of Fusobacterium necrophorum and F. nucleatum, and provided new methods for identification. The involvement of fusobacteria in a wide spectrum of human infections causing tissue necrosis and septicaemia has long been recognised, and, more recently, their importance in intra-amniotic infections, premature labour and tropical ulcers has been reported.

Polymerase chain reaction-amplified nonradioactive probes for identification of Fusobacterium nucleatum

A polymerase chain reaction probe with 100% sequence identity to 120 deoxyribonucleotides of Fusobacterium nucleatum Fev1, coding for a part of the 40-kDa major outer membrane protein, was labeled with the steroid hapten digoxigenin. The probe was compared with various degenerate oligonucleotide probes and found to tolerate much more stringent washing conditions. It was therefore superior in distinguishing, by means of Southern blots and slot blots, F. nucleatum from other oral gram-negative bacteria in the periodontal pocket and from other fusobacterial species and in distinguishing among different strains of F. nucleatum. F. periodonticum was found to be more similar to F. nucleatum than the other fusobacterial species tested.

Cellular fatty acids in Fusobacterium species as a tool for identification

Identification of fusobacteria from clinical specimens currently requires analysis of metabolic end products by gas-liquid chromatography in addition to certain biochemical and enzymatic tests because of the relative biochemical inactivity of these bacteria. Even the finding of pointed, thin gram-negative cells on Gram-stained slides can no longer be relied on for identification of Fusobacterium nucleatum, since at least four other species of fusobacteria have been seen to exhibit similar morphology. We examined 46 clinical isolates and six American Type Culture Collection type strains of fusobacteria by conventional methods and by the Microbial ID Systems MIDI software package for analyzing cellular fatty acid patterns measured by capillary column gas-liquid chromatography. Distinctive patterns of major fatty acids could be used to reliably identify most clinical isolates to the species level. The MIDI system identified 89% of the isolates correctly and provides an alternative to conventional methods.

Intrageneric relationships of members of the genus Fusobacterium as determined by reverse transcriptase sequencing of small-subunit rRNA

The phylogenetic interrelationships of 14 members of the genus Fusobacterium were investigated by performing a comparative analysis of the 16S rRNA sequences of these organisms. The sequence data revealed considerable intrageneric heterogeneity. The four species Fusobacterium nucleatum (including F. nucleatum subsp. nucleatum, F. nucleatum subsp. polymorphum, "F. nucleatum subsp. fusiforme," and "F. nucleatum subsp. animalis"), Fusobacterium alocis, Fusobacterium periodonticum, and Fusobacterium simiae, which colonize oral cavities, exhibited high levels of sequence homology with each other and formed a distinct group within the genus. Fusobacterium mortiferum, Fusobacterium varium, and Fusobacterium ulcerans also formed a phylogenetically coherent group, as did the two species Fusobacterium gonidiaformans and Fusobacterium necrophorum. Fusobacterium russii and Fusobacterium necrogenes displayed no specific relationship with any of the other fusobacteria. The sequence data are discussed in the context of previous physiological and chemical findings.

Identification, and susceptibility to seven antimicrobial agents, of 61 gram-negative anaerobic rods from periodontal pockets

Sixty-one cultures of Gram-negative anaerobic rods were isolated from deep periodontal pockets of patients with rapidly progressive periodontitis. Isolates were speciated as Bacteroides gingivalis (18 isolates), Bacteroides intermedius (8), Bacteroides oris (1), Bacteroides gracilis (17) and Fusobacterium nucleatum (17). Their susceptibilities, to seven antimicrobial agents, were determined in vitro using a plate dilution technique. Amoxycillin and amoxycillin with clavulanic acid were active against all isolates (MIC less than 1 mg/l) and proved the most effective agents tested. F. nucleatum and B. gracilis showed resistance to erythromycin; F. nucleatum had MIC values ranging from 0.03 mg/l up to 128 mg/l when tested with this, least effective agent. Metronidazole was effective against all isolates except for a few strains of B. gracilis (MIC less than 4 mg/l). Tetracycline hydrochloride and minocycline were active against all isolates except for a few strains of B. gracilis (MIC less than 2 mg/l with both minocycline and tetracycline hydrochloride). Penicillin proved less effective than amoxycillin with regard to inhibition of B. gracilis.

Identification of Fusobacterium species by the electrophoretic migration of glutamate dehydrogenase and 2-oxoglutarate reductase in relation to their DNA base composition and peptidoglycan dibasic amino acids

Rapid identification of Fusobacterium spp. is hampered by their inability to ferment carbohydrates and the availability of relatively few useful phenotypic characters. In an attempt to identify new diagnostic markers for species, we reported recently the potential utility of glutamate dehydrogenase (GDH) electrophoretic mobilities for distinguishing eight species of Fusobacterium. We have extended these observations to include all recognised members of the genus except F. prausnitzii and F. perfoetens, and our results show that they cluster into three broad electrophoretic groups. Some species, such as F. periodonticum, F. simiae and F. necrophorum, possessed GDH with similar electrophoretic mobilities. However, within such clusters, the electrophoretic migration of 2-oxoglutarate reductase (OGR) distinguished between species. Neither GDH or OGR mobility alone clearly differentiated all species, but their combined use provided unambiguous discrimination of all species except F. varium and F. mortiferum. The DNA base compositions of all species except F. naviforme (ATCC 25832) and F. sulci, were within the range 26-34 mol% G + C, suggesting the genus may be homogeneous. However, the peptidoglycan composition divided the genus into two major groups that contained either lanthionine or diaminopimelic acid; F. mortiferum peptidoglycan contained both dibasic amino acids.

Amino acid utilization by Fusobacterium nucleatum grown in a chemically defined medium

The present investigation evaluated amino acid utilization by 120 strains of Fusobacterium nucleatum in a chemically defined medium and attempted to relate the patterns to 3 proposed subspecies of F. nucleatum. Strains were inoculated into a chemically defined medium, with and without 2 g/l glucose, consisting of 14 inorganic salts, 21 amino acids, 23 vitamins and cofactors, and 7 purines and pyrimidines. After 7 days of anaerobic incubation, the spent culture medium, as well as the uninoculated control medium, were analyzed for amino acid content by ion chromatography. Amino acid utilization was determined by the differences in concentrations of amino acids found in inoculated and uninoculated samples. If greater than 34% of the amino acid was removed from the medium, the amino acid was considered to be utilized. Of the 21 amino acids present in the chemically defined medium, 8 amino acids, lysine, glutamine, asparagine, histidine, threonine, serine, glutamate and cysteine were consistently utilized. Four amino acids, tyrosine, tryptophan, methionine and aspartate were utilized by some strains but not others. Nine amino acids, alanine, leucine, isoleucine, glycine, valine, phenylalanine, proline, ornithine, and arginine were not utilized by any of the strains. The utilization patterns did not relate to subspecies formed on the basis of SDS-PAGE and DNA hybridization.

The problem of the taxonomy of the fusiform bacillus of acute necrotizing ulcerative gingivitis (Vincent's gingivitis)

The characteristic microscopic appearance of the fusospirochaetal complex in smears from patients with acute necrotizing ulcerative gingivitis has long been regarded as virtually pathognomonic of the disease. Unfortunately there is considerable confusion surrounding the taxonomy of the fusiform organism in the fusospirochaetal complex. The conflicting views appear to be irreconcilable and a re-evaluation of the taxonomy of oral fusiforms is urgently required.