Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The protective effect of recombinant FomA-expressing Lactobacillus acidophilus against periodontal infection

A number of studies have shown that the outer membrane protein FomA found in Fusobacterium nucleatum demonstrates great potential as an immune target for combating periodontitis. Lactobacillus acidophilus is a useful antigen delivery vehicle for mucosal immunisation, and previous studies by our group have shown that L. acidophilus acts as a protective factor in periodontal health. In this study, making use of the immunogenicity of FomA and the probiotic properties of L. acidophilus, we constructed a recombinant form of L. acidophilus expressing the FomA protein and detected the FomA-specific IgG in the serum and sIgA in the saliva of mice through oral administration with the recombinant strains. When serum containing FomA-specific antibodies was incubated with the F. nucleatum in vitro, the number of Porphyromonas gingivalis cells that coaggregated with the F. nucleatum cells was significantly reduced. Furthermore, a mouse gum abscess model was successfully generated, and the range of gingival abscesses in the immune mice was relatively limited compared with the control group. The level of IL-1β in the serum and local gum tissues of the immune mice was consistently lower than in the control group. Our findings indicated that oral administration of the recombinant L. acidophilus reduced the risk of periodontal infection with P. gingivalis and F. nucleatum.

Preservation of Fusobacterium nucleatum and Peptostreptococcus anaerobius DNA after loss of cell viability

AIM

To investigate whether DNA from two obligate anaerobes, Fusobacterium nucleatum and Peptostreptococcus anaerobius, is recoverable after loss of cell viability induced by air exposure.

METHODOLOGY

Harvested cultures of F. nucleatum and P. anaerobius were killed by exposure to air and stored in phosphate-buffered saline. Dead cells were incubated aerobically for up to 6 months. Every month, the presence of detectable DNA in the cell pellet and supernatant was assessed by conventional and quantitative PCR. Cell staining techniques were used to characterize the cell wall permeability of air-killed cells. Scanning electron microscopy was used to examine viable, freshly killed and stored cells.

RESULTS

With conventional PCR, amplifiable DNA was detectable over 6 months in all samples. Quantitative PCR showed a progressive fall in DNA concentration in nonviable cell pellets and a concomitant rise in DNA concentration in the supernatant. DNA staining showed that some air-killed cells retained an intact cell wall. After storage, SEM of both air-killed species revealed shrivelling of the cells, but some cells of P. anaerobius retained their initial form.

CONCLUSION

Amplifiable DNA from F. nucleatum and P. anaerobius was detectable 6 months after loss of viability. Air-killed anaerobes initially retained their cell form, but cells gradually shriveled over time. The morphological changes were more pronounced with the gram-negative F. nucleatum than the gram-positive P. anaerobius. Over 6 months, there was a gradual increase in cell wall permeability with progressive leakage of DNA. Bacterial DNA was recoverable long after loss of cell viability.

Endobronchial lesion due to pulmonary Fusobacterium nucleatum infection in a child

Clinically significant infections due to the members of the genus Fusobacterium are rare. The clinical manifestations of pulmonary Fusobacterium nucleatum infections range from simple aspiration pneumonia to severe diseases as necrotizing pneumonia, lung abscess, and empyema. Endobronchial lesions and obstructions are rarely seen in children and are often a misdiagnosed result in delay of definitive treatment. Here, we report a case of endobronchial lesion due to pulmonary F. nucleatum infection in an entirely healthy child before illness. This is the first case reported in the literature of endobronchial lesion due to pulmonary F. nucleatum infection.

Attachment of Porphyromonas gingivalis to corroded commercially pure titanium and titanium-aluminum-vanadium alloy

BACKGROUND

Titanium dental material can become corroded because of electrochemical interaction in the oral environment. The corrosion process may result in surface modification. It was hypothesized that a titanium surface modified by corrosion may enhance the attachment of periodontal pathogens. This study evaluates the effects of corroded titanium surfaces on the attachment of Porphyromonas gingivalis.

METHODS

Commercially pure titanium (cp-Ti) and titanium-aluminum-vanadium alloy (Ti-6Al-4V) disks were used. Disks were anodically polarized in a standard three-electrode setting in a simulated oral environment with artificial saliva at pH levels of 3.0, 6.5, or 9.0. Non-corroded disks were used as controls. Surface roughness was measured before and after corrosion. Disks were inoculated with P. gingivalis and incubated anaerobically at 37°C. After 6 hours, the disks with attached P. gingivalis were stained with crystal violet, and attachment was expressed based on dye absorption at optical density of 550 nm. All assays were performed independently three times in triplicate. Data were analyzed by two-way analysis of variance, the Tukey honestly significant difference test, t test, and Pearson's correlation test (α = 0.05).

RESULTS

Both cp-Ti and Ti-6Al-4V alloy-corroded disks promoted significantly more bacterial attachment (11.02% and 41.78%, respectively; P <0.0001) than did the non-corroded controls. Significantly more (11.8%) P. gingivalis attached to the cp-Ti disks than to the Ti-6Al-4V alloy disks (P <0.05). No significant difference in P. gingivalis attachment was noted among the corroded groups for both cp-Ti and Ti-6Al-4V alloy (P >0.05). There was no significant correlation between surface roughness and P. gingivalis attachment.

CONCLUSION

A higher degree of corrosion on the titanium surface may promote increased bacterial attachment by oral pathogens.

Fusobacterium species infections: clinical spectrum and outcomes at a district general hospital

PURPOSE

Fusobacterium species infections are rare. Recently, however, this potentially deadly pathogen has been attracting interest, and efforts are being made to characterise its epidemiology and clinical spectrum of disease. The aim of our study is to provide further evidence towards this cause, in what is, to date, the largest study of its kind from the UK.

METHOD

A 22-year, retrospective, descriptive study was performed at Royal Hampshire County Hospital. An electronic database was used to identify patients with microbiologically confirmed infection with Fusobacterium, and clinical records were examined to provide further information on the presentation, source, treatment and outcome.

RESULTS

Fusobacterium species infections were identified in 18 patients during the study period, which is an incidence of 0.76 cases/100,000/year. The overall death rate was 29 %. Half of these patients had Fusobacterium necrophorum infections and were a predominantly young, fit and uniquely male population who had excellent outcomes. Among the remaining patients with Fusobacterium species infections, 22 % had infection with F. varium and 11 % with F. nucleatum. These patients were an older cohort who tended to have co-morbidities and unsurprisingly worse outcomes. We identified a number of Fusobacterium bacteraemias likely to have resulted from pressure ulcers, a presentation that has been rarely reported. Interestingly, we also identified a case of neonatal F. nucleatum bacteraemia that was not associated with premature nor stillborn birth.

CONCLUSION

As work continues to depict the spectrum of disease caused by this enigmatic bacterium, it is hoped that improved clinical suspicion will result in better outcomes and management.

A case of adolescent pelvic inflammatory disease caused by a rare bacterium: Fusobacterium nucleatum

BACKGROUND

Pelvic inflammatory disease (PID) is a polymicrobial infection that typically occurs in sexually active females. PID is rare in premenarchal and/or noncoital young women; however, there are case reports of PID occurring in virginal females. We present the first reported case of PID associated with F. nucleatum. In this unusual case of PID in an adolescent, the responsible organism may have originated from the patient's oral cavity.

CASE

A 13-year-old noncoital Caucasian female presented to a tertiary children's hospital with fever and acute abdominal/pelvic pain. She had experienced a perforated appendix 14 months prior, which was treated by laparoscopy. Postoperatively, she experienced intermittent episodes of recurrent abdominal pain. During this presentation, the physical examination and ultrasound findings were suspicious for an ovarian torsion. She was taken to the operating room where she had an examination under anesthesia and a diagnostic laparoscopy. Findings at the time of laparoscopy were in keeping with a diagnosis of pelvic inflammatory disease. Oral and pelvic fluid cultures were positive for F. nucleatum. She was subsequently treated with antibiotics and her symptoms resolved.

SUMMARY AND CONCLUSION

This case highlights the importance of including PID in the differential diagnosis of noncoital adolescent females presenting with an acute abdomen. Although most Fusobacteria infections are periodontal in nature, translocated infections to the pelvis may have long-term implications for reproductive health. This case also highlights the importance of the role of diagnostic laparoscopy in young women who have persistent pain following previous surgery due to the potential of missed pathology or subclinical infection.

Photodynamic biofilm inactivation by SAPYR--an exclusive singlet oxygen photosensitizer

Prevention and control of biofilm-growing microorganisms are serious problems in public health due to increasing resistances of some pathogens against antimicrobial drugs and the potential of these microorganisms to cause severe infections in patients. Therefore, alternative approaches that are capable of killing pathogens are needed to supplement standard treatment modalities. One alternative is the photodynamic inactivation of bacteria (PIB). The lethal effect of PIB is based on the principle that visible light activates a photosensitizer, leading to the formation of reactive oxygen species, e.g., singlet oxygen, which induces phototoxicity immediately during illumination. SAPYR is a new generation of photosensitizers. Based on a 7-perinaphthenone structure, it shows a singlet oxygen quantum yield ΦΔ of 99% and is water soluble and photostable. Moreover, it contains a positive charge for good adherence to cell walls of pathogens. In this study, the PIB properties of SAPYR were investigated against monospecies and polyspecies biofilms formed in vitro by oral key pathogens. SAPYR showed a dual mechanism of action against biofilms: (I) it disrupts the structure of the biofilm even without illumination; (II) when irradiated, it inactivates bacteria in a polymicrobial biofilm after one single treatment with an efficacy of ≥ 99.99%. These results encourage further investigation on the potential of PIB using SAPYR for the treatment of localized infectious diseases.

Inter-bacterial correlations in subgingival biofilms: a large-scale survey

AIM

Although the complexity of the oral ecology and the ecological differences between health and disease are well accepted, a clear view on the dynamics in relation to disease is lacking. In this study, the prevalence and abundance of 20 key oral bacteria was assessed in health and disease and more importantly a closer look was given to the inter-bacterial relationships.

MATERIALS AND METHODS

A blinded microbiological database was analysed in this cross-sectional, retrospective study. The database was constructed based on microbiological analyses of samples from 6308 patients, with gradations of periodontitis (healthy to periodontitis). Data concerning the abundance of 20 oral bacteria and probing pocket depth were provided.

RESULTS

Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Eubacterium nodatum, Porphyromonas micra and Porphyromonas intermedia showed a clear increase in abundance and prevalence with increasing pocket depth. Correlation matrices illustrated that almost all microorganisms were in one way correlated to other species and most of these correlations were significant. Several beneficial bacteria showed strong correlations with other beneficial bacteria.

CONCLUSION

Knowledge on bacterial correlations can pave the way for new treatment options focusing on restoring the shifted balance.

Crystal structure of the capsular polysaccharide synthesizing protein CapE of Staphylococcus aureus

Enzymes synthesizing the bacterial CP (capsular polysaccharide) are attractive antimicrobial targets. However, we lack critical information about the structure and mechanism of many of them. In an effort to reduce that gap, we have determined three different crystal structures of the enzyme CapE of the human pathogen Staphylococcus aureus. The structure reveals that CapE is a member of the SDR (short-chain dehydrogenase/reductase) super-family of proteins. CapE assembles in a hexameric complex stabilized by three major contact surfaces between protein subunits. Turnover of substrate and/or coenzyme induces major conformational changes at the contact interface between protein subunits, and a displacement of the substrate-binding domain with respect to the Rossmann domain. A novel dynamic element that we called the latch is essential for remodelling of the protein–protein interface. Structural and primary sequence alignment identifies a group of SDR proteins involved in polysaccharide synthesis that share the two salient features of CapE: the mobile loop (latch) and a distinctive catalytic site (MxxxK). The relevance of these structural elements was evaluated by site-directed mutagenesis.

Incidence, risk factors, and outcomes of Fusobacterium species bacteremia

Background

The aim of this study was to assess the epidemiology of intestinal parasitoses during a 5-year period in patients attending a tertiary-care hospital in a non-endemic setting.

Methods

In the period 2006–2010, 15,752 samples from 8,886 patients with clinically suspected parasitosis were subjected to macroscopic and microscopic examination, to parasitic antigen detection assays, and to cultures for protozoa and nematodes. Real-time PCR assays for the differentiation of Entamoeba histolytica and E. dispar and for the detection of Dientamoeba fragilis were also used.

A statistical analysis evaluating the demographic data of the patients with intestinal parasitic infections was performed.

Results

Intestinal parasitic infections were diagnosed in 1,477 patients (16.6% prevalence), mainly adults and immigrants from endemic areas for faecal-oral infections; protozoa were detected in 93.4% and helminths in 6.6% of the cases, the latter especially in immigrants. Blastocystis hominis was the most common intestinal protozoan, and G. intestinalis was the most frequently detected among pathogenic protozoa, prevalent in immigrants, males, and pediatric patients. Both single (77.9%) and mixed (22.1%) parasitic infections were observed, the latter prevalent in immigrants.

Conclusions

Despite the importance of the knowledge about the epidemiology of intestinal parasitoses in order to adopt appropriate control measures and adequate patient care all over the world, data regarding industrialized countries are rarely reported in the literature. The data presented in this study indicate that intestinal parasitic infections are frequently diagnosed in our laboratory and could make a contribution to stimulate the attention by physicians working in non-endemic areas on the importance of suspecting intestinal parasitoses.

Incidence, risk factors, and outcomes of Fusobacterium species bacteremia

Background

Fusobacterium species (spp.) bacteremia is uncommon and has been associated with a variety of clinical presentations. We conducted a retrospective, population based study to determine the relative proportion of species in this genus causing bacteremia and the risk factors for infection and adverse clinical outcomes.

Methods

All cases of Fusobacterium spp. bacteremia detected at a regional microbiology laboratory serving outpatient and acute care for a population of approximately 1.3 million people over 11 years were identified from a computerized database. Clinical data on these cases was extracted from an administrative database and analyzed to determine underlying risk factors for and outcomes of infection.

Results

There were 72 incident cases of Fusobacterium spp. bacteremia over the study period (0.55 cases/100,000 population per annum). F. nucleatum was the most frequent species (61%), followed by F. necrophorum (25%). F. necrophorum bacteremia occurred in a younger population without underlying comorbidities and was not associated with mortality. F. nucleatum bacteremia was found in an older population and was associated with underlying malignancy or receiving dialysis. Death occurred in approximately 10% of F. nucleatum cases but causality was not established in this study.

Conclusions

Fusobacterium spp. bacteremia in our community is uncommon and occurs in approximately 5.5 cases per million population per annum. F. necrophorum occurred in an otherwise young healthy population and was not associated with any mortality. F. nucleatum was found primarily in older patients with chronic medical conditions and was associated with a mortality of approximately 10%. Bacteremias from other Fusobacterium spp. were rare.

Fusobacterial infections in children

Fusobacteria are members of the oral and gastrointestinal flora and are important potential pathogens in children. They are increasingly recognized as a cause of infections in children. These include infections of the head and neck (Lemierre syndrome, acute and chronic mastoiditis, chronic otitis and sinusitis, tonsillitis, peritonsillar and retropharyngeal abscesses, postanginal cervical lymphadenitis, periodontitis), brain, lungs, abdomen, pelvis, bones, joints, and blood. This review describes the clinical spectrum of fusobacterial infection in children and their management.

Co-occurrence of anaerobic bacteria in colorectal carcinomas

BACKGROUND

Numerous cancers have been linked to microorganisms. Given that colorectal cancer is a leading cause of cancer deaths and the colon is continuously exposed to a high diversity of microbes, the relationship between gut mucosal microbiome and colorectal cancer needs to be explored. Metagenomic studies have shown an association between Fusobacterium species and colorectal carcinoma. Here, we have extended these studies with deeper sequencing of a much larger number (n = 130) of colorectal carcinoma and matched normal control tissues. We analyzed these data using co-occurrence networks in order to identify microbe-microbe and host-microbe associations specific to tumors.

RESULTS

We confirmed tumor over-representation of Fusobacterium species and observed significant co-occurrence within individual tumors of Fusobacterium, Leptotrichia and Campylobacter species. This polymicrobial signature was associated with over-expression of numerous host genes, including the gene encoding the pro-inflammatory chemokine Interleukin-8. The tumor-associated bacteria we have identified are all Gram-negative anaerobes, recognized previously as constituents of the oral microbiome, which are capable of causing infection. We isolated a novel strain of Campylobacter showae from a colorectal tumor specimen. This strain is substantially diverged from a previously sequenced oral Campylobacter showae isolate, carries potential virulence genes, and aggregates with a previously isolated tumor strain of Fusobacterium nucleatum.

CONCLUSIONS

A polymicrobial signature of Gram-negative anaerobic bacteria is associated with colorectal carcinoma tissue.

Microbial dysbiosis and colon carcinogenesis: could colon cancer be considered a bacteria-related disease?

Colorectal cancer (CRC) is posing an increasingly important burden on the health care system, with western countries seeing a growing incidence of the disease. Except for germline DNA mutations which have been attributed to less than 5% of patients, little is known about the main causes of CRC. However, environment factors such as food, lifestyle and medication are now suspected to have a major influence on inducing cancers. Today, exhaustive quantitative and qualitative evaluation of all environmental factors is not possible. Various environment-induced diseases have been characterized based on colon microflora, also called microbiota, analyses. Growing data have shown specific changes in microflora (i.e. dysbiosis) in the stools of patients with colon cancer or those adherent to the colonic mucosa. Thus, it appears that microbiota may be considered a platform offering host and environment interactions for studying CRCs. The hypothesis that colon cancer might be a bacteria-related disease is suggested and perspectives are discussed.

Microbial dysbiosis and colon carcinogenesis: could colon cancer be considered a bacteria-related disease?

Colorectal cancer (CRC) is posing an increasingly important burden on the health care system, with western countries seeing a growing incidence of the disease. Except for germline DNA mutations which have been attributed to less than 5% of patients, little is known about the main causes of CRC. However, environment factors such as food, lifestyle and medication are now suspected to have a major influence on inducing cancers. Today, exhaustive quantitative and qualitative evaluation of all environmental factors is not possible. Various environment-induced diseases have been characterized based on colon microflora, also called microbiota, analyses. Growing data have shown specific changes in microflora (i.e. dysbiosis) in the stools of patients with colon cancer or those adherent to the colonic mucosa. Thus, it appears that microbiota may be considered a platform offering host and environment interactions for studying CRCs. The hypothesis that colon cancer might be a bacteria-related disease is suggested and perspectives are discussed.

Activated zeolite--suitable carriers for microorganisms in anaerobic digestion processes?

Plant cell wall structures represent a barrier in the biodegradation process to produce biogas for combustion and energy production. Consequently, approaches concerning a more efficient de-polymerisation of cellulose and hemicellulose to monomeric sugars are required. Here, we show that natural activated zeolites (i.e. trace metal activated zeolites) represent eminently suitable mineral microhabitats and potential carriers for immobilisation of microorganisms responsible for anaerobic hydrolysis of biopolymers stabilising related bacterial and methanogenic communities. A strategy for comprehensive analysis of immobilised anaerobic populations was developed that includes the visualisation of biofilm formation via scanning electron microscopy and confocal laser scanning microscopy, community and fingerprint analysis as well as enzyme activity and identification analyses. Using SDS polyacrylamide gel electrophoresis, hydrolytical active protein bands were traced by congo red staining. Liquid chromatography/mass spectroscopy revealed cellulolytical endo- and exoglucanase (exocellobiohydrolase) as well as hemicellulolytical xylanase/mannase after proteolytic digestion. Relations to hydrolytic/fermentative zeolite colonisers were obtained by using single-strand conformation polymorphism analysis (SSCP) based on amplification of bacterial and archaeal 16S rRNA fragments. Thereby, dominant colonisers were affiliated to the genera Clostridium, Pseudomonas and Methanoculleus. The specific immobilisation on natural zeolites with functional microbes already colonising naturally during the fermentation offers a strategy to systematically supply the biogas formation process responsive to population dynamics and process requirements.

The surface layer of Tannerella forsythia contributes to serum resistance and oral bacterial coaggregation

Tannerella forsythia is an anaerobic, Gram-negative bacterium involved in the so-called "red complex," which is associated with severe and chronic periodontitis. The surface layer (S-layer) of T. forsythia is composed of cell surface glycoproteins, such as TfsA and TfsB, and is known to play a role in adhesion/invasion and suppression of proinflammatory cytokine expression. Here we investigated the association of this S-layer with serum resistance and coaggregation with other oral bacteria. The growth of the S-layer-deficient mutant in a bacterial medium containing more than 20% non-heat-inactivated calf serum (CS) or more than 40% non-heat-inactivated human serum was significantly suppressed relative to that of the wild type (WT). Next, we used confocal microscopy to perform quantitative analysis on the effect of serum. The survival ratio of the mutant exposed to 100% non-heat-inactivated CS (76% survival) was significantly lower than that of the WT (97% survival). Furthermore, significant C3b deposition was observed in the mutant but not in the WT. In a coaggregation assay, the mutant showed reduced coaggregation with Streptococcus sanguinis, Streptococcus salivarius, and Porphyromonas gingivalis but strong coaggregation with Fusobacterium nucleatum. These results indicated that the S-layer of T. forsythia plays multiple roles in virulence and may be associated with periodontitis.

The relationship between turbidity of mouth-rinsed water and oral health status

OBJECTIVES

The purpose of this study was to examine the relationship between turbidity of mouth rinsed water and oral health status such as dental and periodontal conditions, oral hygiene status, flow rate of saliva and oral bacteria.

MATERIALS AND METHODS

Subjects were 165 patients who visited the Dental Hospital, Tokyo Medical and Dental University. Oral health status, including dental and periodontal conditions, oral hygiene status and flow rate of saliva, was clinically examined. The turbidity was measured with a turbidimeter. Quantification of Fusobacterium spp, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola and total bacteria levels was performed using real-time PCR. The Pearson correlation and multiple regression analysis were used to explore the associations between the turbidity and oral health parameters.

RESULTS

The turbidity showed significant correlations with the number of decayed teeth and deep pockets, the plaque index, extent of tongue coating and Fusobacterium spp, P. gingivalis, T. forsythia, T. denticola and total bacteria levels. In a multiple regression model, the turbidity was negatively associated with the flow rate of saliva and positively associated with the total number of bacteria (p < 0.001).

CONCLUSION

Current findings suggested that turbidity of mouth rinsed water could be used as an indicator to evaluate oral health condition and the amount of bacteria in the oral cavity. In addition, the turbiditimeter appeared as a simple and objective device for screening abnormality of oral health condition at chair side as well as community-based research.

Maternal oral origin of Fusobacterium nucleatum in adverse pregnancy outcomes as determined using the 16S-23S rRNA gene intergenic transcribed spacer region

Fusobacterium nucleatum, a common Gram-negative anaerobe prevalent in the oral cavity, possesses the ability to colonize the amniotic cavity and the fetus. However, F. nucleatum may also be part of the vaginal microbiota from where it could reach the amniotic tissues. Due to the heterogeneity of F. nucleatum, consisting of five subspecies, analysis at the subspecies/strain level is desirable to determine its precise origin. The aims of this study were: (i) to evaluate the use of the 16S-23S rRNA gene intergenic transcribed spacer (ITS) region as a tool to differentiate subspecies of F. nucleatum, and (ii) to design a simplified technique based on the ITS to determine the origin of F. nucleatum strains associated with adverse pregnancy outcomes. Amplified fragments of the 16S-23S rRNA gene ITS region corresponding to the five subspecies of F. nucleatum were subjected to cloning and sequencing to characterize the different ribosomal operons of the subspecies. Distinctive length and sequence patterns with potential to be used for identification of the subspecies/strain were identified. These were used to evaluate the origin of F. nucleatum identified in neonatal gastric aspirates (swallowed amniotic fluid) by sequence comparisons with the respective oral and vaginal maternal samples. A simplified technique using a strain-specific primer in a more sensitive nested PCR was subsequently developed to analyse ten paired neonatal-maternal samples. Analysing the variable fragment of the ITS region allowed the identification of F. nucleatum subsp. polymorphum from an oral origin as potentially being involved in neonatal infections. Using a strain-specific primer, the F. nucleatum subsp. polymorphum strain was detected in both neonatal gastric aspirates and maternal oral samples in cases of preterm birth from mothers presenting with localized periodontal pockets. Interestingly, the same strain was not present in the vaginal sample of any case investigated. The 16S-23S rRNA gene ITS can be a useful tool to determine the origin of F. nucleatum. The results of this study strongly indicate that F. nucleatum subsp. polymorphum of oral origin could be involved with pregnancy complications.

A proteomic investigation of Fusobacterium nucleatum alkaline-induced biofilms

Background

The Gram negative anaerobe Fusobacterium nucleatum has been implicated in the aetiology of periodontal diseases. Although frequently isolated from healthy dental plaque, its numbers and proportion increase in plaque associated with disease. One of the significant physico-chemical changes in the diseased gingival sulcus is increased environmental pH. When grown under controlled conditions in our laboratory, F. nucleatum subspecies polymorphum formed mono-culture biofilms when cultured at pH 8.2. Biofilm formation is a survival strategy for bacteria, often associated with altered physiology and increased virulence. A proteomic approach was used to understand the phenotypic changes in F. nucleatum cells associated with alkaline induced biofilms. The proteomic based identification of significantly altered proteins was verified where possible using additional methods including quantitative real-time PCR (qRT-PCR), enzyme assay, acidic end-product analysis, intracellular polyglucose assay and Western blotting.

Results

Of 421 proteins detected on two-dimensional electrophoresis gels, spot densities of 54 proteins varied significantly (p < 0.05) in F. nucleatum cultured at pH 8.2 compared to growth at pH 7.4. Proteins that were differentially produced in biofilm cells were associated with the functional classes; metabolic enzymes, transport, stress response and hypothetical proteins. Our results suggest that biofilm cells were more metabolically efficient than planktonic cells as changes to amino acid and glucose metabolism generated additional energy needed for survival in a sub-optimal environment. The intracellular concentration of stress response proteins including heat shock protein GroEL and recombinational protein RecA increased markedly in the alkaline environment. A significant finding was the increased abundance of an adhesin, Fusobacterial outer membrane protein A (FomA). This surface protein is known for its capacity to bind to a vast number of bacterial species and human epithelial cells and its increased abundance was associated with biofilm formation.

Conclusion

This investigation identified a number of proteins that were significantly altered by F. nucleatum in response to alkaline conditions similar to those reported in diseased periodontal pockets. The results provide insight into the adaptive mechanisms used by F. nucleatum biofilms in response to pH increase in the host environment.

T-RFLP-based differences in oral microbial communities as risk factor for development of oral diseases under stress

The human oral microbiome is comprised of approximately 800 different bacterial species many of which are as yet uncultivated. Their dynamics and variability in relation to health and disease are still poorly understood. Here we tested the hypothesis that the emergence of stress-induced periodontal diseases is predictable based on the composition of the initial microbiota. As a model, we analysed 58 individuals performing a challenging expedition (exposure to various stress-factors due to changes in diet, hygiene, temperature, physical and mental stress) in remote regions of the Himalayans (Annapurna Himal). Plaque samples were taken at start (Bhulbule) and destination (3000 meter difference in altitude) seven days later (Manang). Twenty-eight individuals remained symptom-free (Group I) while 30 participants developed periodontal problems, mostly gingivitis (Group II). The microbiota was monitored via T-RFLP-analysis of amplified 16S rRNA genes directly from the plaque samples. Based on the Additive-Main-Effects-Multiplicative-Interactions-model (AMMI) using the T-Rex software variation from T-RF main effects was at least 95%, indicating that most variation was due to inherent differences in microbial communities among individuals. However, an interaction signal up to 3% was consistently observed between groups I and II but not between the two time points of sampling regardless of selected analytical parameters. The data, supported by heterogeneity, diversity and similarity indices indicated marked differences between groups I and II already prior the onset of clinical symptoms. These differences may provide the basis for using ecological parameters of oral microbial communities as early diagnostic marker for the onset of oral disorders and infections.

Fusobacterium nucleatum infection mimicking metastatic cancer

A 48-year-old man presented with fevers, chills, weight loss, multiple liver masses, and several superficial and deep venous thromboses in lower extremities. Cancer work up was negative. A liver biopsy grew Fusobacterium nucleatum. To our knowledge, F. nucleatum infection presenting with multiple liver masses and Trousseau-like syndrome has not been reported earlier.

The FomA porin from Fusobacterium nucleatum is a Toll-like receptor 2 agonist with immune adjuvant activity

Many bacterial components selectively activate immune and nonhematopoietic target cells via Toll-like receptor (TLR) signaling; modulation of such host responses defines the immune adjuvant properties of these bacterial products. For example, the outer membrane protein porins from Neisseria, Salmonella, and Shigella are known TLR2 agonists with established systemic and mucosal immune adjuvanticity. Early work indicated that the FomA porin from Fusobacterium nucleatum has immune adjuvant activity in mice. Using a purified recombinant FomA, we have verified its immune stimulatory properties and have defined a role for TLR2 signaling in its in vitro and in vivo activity. FomA induces interleukin 8 (IL-8) secretion and NF-κB-dependent luciferase activity in HEK cells expressing TLR2, IL-6 secretion, and cell surface upregulation of CD86 and major histocompatibility complex (MHC) II in primary B cells from wild-type mice, but it fails to activate cells from TLR2 knockout mice. Accordingly, the immune adjuvant activity of FomA is also TLR2 dependent. In a mouse model of immunization with ovalbumin (OVA), FomA induces enhanced production of OVA-specific IgM and IgG, including IgG1 and IgG2b antibodies, as well as enhanced secretion of IL-10 and IL-6, consistent with a Th2-type adjuvant effect. We also observe a moderate production of anti-FomA antibodies, suggesting that FomA is also immunogenic, a quality that is also TLR2 dependent. Therefore, modulation of host immune responses by FomA may be effective for targeting general host immunity not only to pathogens (as a novel TLR2 adjuvant) but also to F. nucleatum itself (as an antigen), expanding its use as a self-adjuvanted antigen in an immunization strategy against polymicrobial infections, including those by F. nucleatum.

The role of coaggregation between Porphyromonas gingivalis and Fusobacterium nucleatum on the host response to mixed infection

AIM

To evaluate the role of coaggregation between Porphyromonas gingivalis and Fusobacterium nucleatum on the virulence of the mixed infection in mice.

MATERIALS AND METHODS

Inhibition of coaggregation was carried out using lactose. In vitro, inhibition of coaggregation was verified using a coaggregation assay. In vivo, the virulence of the mixed infection, with and without coaggregation, was examined in a model of experimental periodontitis in mice. The local host response to the mixed infection, with or without coaggregation, was examined using the subcutaneous chamber model of infection.

RESULTS

Lactose inhibited the coaggregation between P. gingivalis and F. nucleatum at all the tested concentrations (1-0.0625 M). Surprisingly, the addition of lactose to the mixed infection increased the severity of experimental periodontitis (as measured by alveolar bone loss) compared with mixed infection with coaggregating bacteria. The addition of lactose to the mixed infection resulted in mild attenuation of TNFα and IL-1β levels. In addition, inhibition of coaggregation resulted in inhibition of the phagocytosis of F. nucleatum and augmentation of the phagocytosis of P. gingivalis.

CONCLUSIONS

The ability of P. gingivalis and F. nucleatum to coaggregate may limit their ability to induce experimental periodontitis in a mixed infection model. Moreover, there is a shift in the phagocytosis pattern of the bacteria with the annulment of coaggregeaiton, with a reduction in F. nucleatum phagocytosis and amplification of P. gingivalis phagocytosis. The increased virulence of the mixed infection without coaggregation may surprisingly lay in the sustention of F. nucleatum in the infected sites.

Fusobacterium nucleatum and Tannerella forsythia induce synergistic alveolar bone loss in a mouse periodontitis model

Tannerella forsythia is strongly associated with chronic periodontitis, an inflammatory disease of the tooth-supporting tissues, leading to tooth loss. Fusobacterium nucleatum, an opportunistic pathogen, is thought to promote dental plaque formation by serving as a bridge bacterium between early- and late-colonizing species of the oral cavity. Previous studies have shown that F. nucleatum species synergize with T. forsythia during biofilm formation and pathogenesis. In the present study, we showed that coinfection of F. nucleatum and T. forsythia is more potent than infection with either species alone in inducing NF-κB activity and proinflammatory cytokine secretion in monocytic cells and primary murine macrophages. Moreover, in a murine model of periodontitis, mixed infection with the two species induces synergistic alveolar bone loss, characterized by bone loss which is greater than the additive alveolar bone losses induced by each species alone. Further, in comparison to the single-species infection, mixed infection caused significantly increased inflammatory cell infiltration in the gingivae and osteoclastic activity in the jaw bones. These data show that F. nucleatum subspecies and T. forsythia synergistically stimulate the host immune response and induce alveolar bone loss in a murine experimental periodontitis model.

Sialic acid, periodontal pathogens and Tannerella forsythia: stick around and enjoy the feast!

Periodontal pathogens, like any other human commensal or pathogenic bacterium, must possess both the ability to acquire the necessary growth factors and the means to adhere to surfaces or reside and survive in their environmental niche. Recent evidence has suggested that sialic acid containing host molecules may provide both of these requirements in vivo for several periodontal pathogens but most notably for the red complex organism Tannerella forsythia. Several other periodontal pathogens also possess sialic acid scavenging enzymes - sialidases, which can also expose adhesive epitopes, but might also act as adhesins in their own right. In addition, recent experimental work coupled with the release of several genome sequences has revealed that periodontal bacteria have a range of sialic acid uptake and utilization systems while others may also use sialic acid as a cloaking device on their surface to mimic host and avoid immune recognition. This review will focus on these systems in a range of periodontal bacteria with a focus on Ta. forsythia.

Fusobacterium nucleatum infection is prevalent in human colorectal carcinoma

An estimated 15% or more of the cancer burden worldwide is attributable to known infectious agents. We screened colorectal carcinoma and matched normal tissue specimens using RNA-seq followed by host sequence subtraction and found marked over-representation of Fusobacterium nucleatum sequences in tumors relative to control specimens. F. nucleatum is an invasive anaerobe that has been linked previously to periodontitis and appendicitis, but not to cancer. Fusobacteria are rare constituents of the fecal microbiota, but have been cultured previously from biopsies of inflamed gut mucosa. We obtained a Fusobacterium isolate from a frozen tumor specimen; this showed highest sequence similarity to a known gut mucosa isolate and was confirmed to be invasive. We verified overabundance of Fusobacterium sequences in tumor versus matched normal control tissue by quantitative PCR analysis from a total of 99 subjects (p = 2.5 × 10(-6)), and we observed a positive association with lymph node metastasis.

Fusobacterium nucleatum prosthetic hip infection in an adult with sickle cell-beta thalassemia

Fusobacterium nucleatum is an anaerobic Gram-negative bacillus commensal to the human oropharynx and gastrointestinal tract which causes an array of human infection, yet it has never been associated with infection of prosthetic joints. We report the first case of prosthetic hip infection caused by F. nucleatum in a man with sickle cell-beta thalassemia.

Characteristics and outcomes of Fusobacterium nucleatum bacteremia--a 6-year experience at a tertiary care hospital in northern Taiwan

Fusobacterium nucleatum bacteremia is critical and not well defined. To identify the clinical characteristics and outcomes, we conducted a retrospective review of hospitalized patients from January 2004 to December 2009 at a tertiary center in northern Taiwan. Fifty-seven patients were enrolled. The mean age was 58.1 years, and the mean Pitt bacteremia score was 4.7. Males predominated (59.6%), and the overall 30-day mortality rate was up to 47.4%. Malignancy was the major comorbidity (26/57, 45.6%), especially oropharyngeal and gastrointestinal cancers (19/26, 73.1%). Pneumonia (17/57, 29.8%) was the most common presentation with high rates of respiratory failure (15/17, 88.2%) and mortality (11/17, 64.7%), followed by intra-abdominal infections (7/57, 12.3%). In multivariate analysis, higher Pitt bacteremia score, nosocomial infection, anemia, and intensive care unit stay were the independent factors for 30-day mortality. Nosocomial F. nucleatum bacteremia was a significant mortality predictor independent to other parameters of disease severities.

Oxidative stress response in the opportunistic oral pathogen Fusobacterium nucleatum

The anaerobic, Gram-negative bacillus Fusobacterium nucleatum plays a vital role in oral biofilm formation and the development of periodontal disease. The organism plays a central bridging role between early and late colonizers within dental plaque and plays a protective role against reactive oxygen species. Using a two-dimensional gel electrophoresis and mass spectrometry approach, we have annotated 78 proteins within the proteome of F. nucleatum subsp. nucleatum and identified those proteins whose apparent intracellular concentrations change in response to either O(2)- or H(2)O(2)-induced oxidative stress. Three major protein systems were altered in response to oxidative stress: (i) proteins of the alkyl hydroperoxide reductase/thioredoxin reductase system were increased in intracellular concentration; (ii) glycolytic enzymes were modified by oxidation (i.e. D-glyceraldehyde 3-phosphate dehydrogenase, and fructose 6-phosphate aldolase) or increased in intracellular concentration, with an accompanying decrease in ATP production; and (iii) the intracellular concentrations of molecular chaperone proteins and related proteins (i.e. ClpB, DnaK, HtpG, and HrcA) were increased.

Glutamate racemization and catabolism in Fusobacterium varium

The pathways of glutamate catabolism in the anaerobic bacterium Fusobacterium varium, grown on complex, undefined medium and chemically defined, minimal medium, were investigated using specifically labelled (13)C-glutamate. The metabolic end-products acetate and butyrate were isolated from culture fluids and derivatized for analysis by nuclear magnetic resonance and mass spectrometry. On complex medium, labels from L-[1-(13)C]glutamate and L-[4-(13)C]glutamate were incorporated into C1 of acetate and equally into C1/C3 of butyrate, while label derived from L-[5-(13)C]glutamate was not incorporated. The isotopic incorporation results and the detection of glutamate mutase and 3-methylaspartate ammonia lyase in cell extracts are most consistent with the methylaspartate pathway, the best known route of glutamate catabolism in Clostridium species. When F. varium was grown on defined medium, label from L-[4-(13)C]glutamate was incorporated mainly into C4 of butyrate, demonstrating a major role for the hydroxyglutarate pathway. Upon addition of coenzyme B(12) or cobalt ion to the defined medium in replicate experiments, isotope was located equally at C1/C3 of butyrate in accord with the methylaspartate pathway. Racemization of D-glutamate and subsequent degradation of L-glutamate via the methylaspartate pathway are supported by incorporation of label into C2 of acetate and equally into C2/C4 of butyrate from D-[3-(13)C]glutamate and the detection of a cofactor-independent glutamate racemase in cell extracts. Together the results demonstrate a major role for the methylaspartate pathway of glutamate catabolism in F. varium and substantial participation of the hydroxyglutarate pathway when coenzyme B(12) is not available.

Predation of oral pathogens by Bdellovibrio bacteriovorus 109J

Periodontal diseases are multifactorial infections elicited by a complex of primarily gram-negative bacteria that interact with host tissues and lead to the destruction of the periodontal structures. Bdellovibrio bacteriovorus is a gram-negative bacterium that preys upon other gram-negative bacteria. It was previously shown that B. bacteriovorus has an ability to attack and remove surface-attached bacteria or biofilms. In this study, we examined the host specificity of B. bacteriovorus strain 109J and its ability to prey on oral pathogens associated with periodontitis, including; Aggregatibacter actinomycetemcomitans, Eikenella corrodens, Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis and Tannerella forsythia. We further demonstrated that B. bacteriovorus 109J has an ability to remove biofilms of Ei. corrodens as well as biofilms composed of A. actinomycetemcomitans. Bdellovibrio bacteriovorus was able to remove A. actinomycetemcomitans biofilms developed on hydroxyapatite surfaces and in the presence of saliva, as well as to detach metabolically inactive biofilms. Experiments aimed at enhancing the biofilm removal aptitude of B. bacteriovorus with the aid of extracellular-polymeric-substance-degrading enzymes demonstrated that proteinase-K inhibits predation. However, treating A. actinomycetemcomitans biofilms with DspB, a poly-N-acetylglucosamine (PGA) -hydrolysing enzyme, increased biofilm removal. Increased biofilm removal was also recorded when A. actinomycetemcomitans PGA-defective mutants were used as host cells, suggesting that PGA degradation could enhance the removal of A. actinomycetemcomitans biofilm by B. bacteriovorus.

Isolation of a novel bacteriophage specific for the periodontal pathogen Fusobacterium nucleatum

Fusobacterium nucleatum is a periodontal pathogen that has been directly associated with the development and progression of periodontal disease, a widespread pathology that affects the support tissues of the tooth. We isolated a new bacteriophage (FnpΦ02) that specifically infects this bacterium. Transmission electron microscopy showed that the virion is composed of an icosahedral head and a segmented tail. The size of the phage genome was estimated to be approximately 59 kbp of double-stranded DNA. The morphological features and the genetic characteristics suggest that FnpΦ02 is part of the Siphoviridae family. Using one-step growth and adsorption experiments, the latent period, burst size, and adsorption rate were estimated to be 15 h, 100 infectious units per cell, and 7.5 × 10⁻¹⁰ ml min⁻¹, respectively. A small fragment of phage DNA was cloned and sequenced, showing 93% nucleotide identity with the phage PA6 of Propionibacterium acnes and amino acid identity with fragments of two proteins (Gp3 and Gp4) of this phage. To our knowledge, FnpΦ02 is the first phage described to infect Fusobacterium nucleatum and provides the base for future exploration of phages in the control of periodontal disease.

Fusobacterium nucleatum outer membrane proteins Fap2 and RadD induce cell death in human lymphocytes

Bacterially induced cell death in human lymphocytes is an important virulence factor for pathogenic bacteria. Previously discovered mechanisms of bacterially induced cell death are predominantly based on the transfer of bacterial proteins to the target host cell, such as the toxins secreted through type I, II, and VI secretion systems or effector proteins injected through type III, IV, and Vb secretion systems. Here, we report a mechanism employed by the Gram-negative oral pathogen Fusobacterium nucleatum for cell death induction of human lymphocytes via two outer membrane proteins (OMPs), Fap2 and RadD, which share regions homologous to autotransporter secretion systems (type Va secretion systems). Genetic and physiological studies established that inactivation of the two OMPs led to significantly reduced ability to trigger cell death in Jurkat cells, while the corresponding double mutant was almost completely attenuated. Additional biochemical and molecular analyses demonstrated that cell-free F. nucleatum membranes are sufficient to induce cell death in Jurkat cells, suggesting that no active process or effector protein transfer was necessary to induce eukaryotic cell death.

Production of indole from L-tryptophan and effects of these compounds on biofilm formation by Fusobacterium nucleatum ATCC 25586

The l-tryptophan degradation product indole is a purported extracellular signaling molecule that influences biofilm formation in various bacteria. Here we analyzed the mechanisms of indole production in Fusobacterium nucleatum and the effects of tryptophan and indole on F. nucleatum planktonic and biofilm cells. The amino acid sequence deduced from the fn1943 gene in F. nucleatum ATCC 25586 was 28% identical to that deduced from tnaA in Escherichia coli, which encodes tryptophanase catalyzing the beta-elimination of l-tryptophan to produce indole. The fn1943 gene was cotranscribed with the downstream gene fn1944, which is a homolog of tnaB encoding low-affinity tryptophan permease. The transcript started at position -68 or -153 from the first nucleotide of the fn1943 translation initiation codon. Real-time quantitative PCR showed that much more F. nucleatum fn1943 transcripts were obtained from log-phase cells than from stationary-phase cells. Indole production by the purified recombinant protein encoded by fn1943 was examined using high-performance liquid chromatography. The K(m) and k(cat) of the enzyme were 0.26 +/- 0.03 mM and 0.74 +/- 0.04 s(-1), respectively. F. nucleatum biofilm formation and the biofilm supernatant concentration of indole increased dose dependently with increasing tryptophan concentrations. Exogenous indole also increased F. nucleatum biofilm formation in a dose-dependent manner. Even at very high concentrations, tryptophan did not affect fn1943 expression, whereas similar indole concentrations decreased expression. Thus, exogenous tryptophan and indole were suggested to increase F. nucleatum biofilms.

Vaccination targeting surface FomA of Fusobacterium nucleatum against bacterial co-aggregation: Implication for treatment of periodontal infection and halitosis

The mechanical therapy with multiple doses of antibiotics is one of modalities for treatment of periodontal diseases. However, treatments using multiple doses of antibiotics carry risks of generating resistant strains and misbalancing the resident body flora. We present an approach via immunization targeting an outer membrane protein FomA of Fusobacterium nucleatum (F. nucleatum), a central bridging organism in the architecture of oral biofilms. Neutralization of FomA considerably abrogated the enhancement of bacterial co-aggregation, biofilms and production of volatile sulfur compounds mediated by an inter-species interaction of F. nucleatum with Porphyromonas gingivalis (P. gingivalis). Vaccination targeting FomA also conferred a protective effect against co-infection-induced gum inflammation. Here, we advance a novel infectious mechanism by which F. nucleatum co-opts P. gingivalis to exacerbate gum infections. FomA is highlighted as a potential target for development of new therapeutics against periodontal infection and halitosis in humans.

Novel bisstyryl derivatives of bakuchiol: targeting oral cavity pathogens

Novel bisstyryl derivatives of bakuchiol using Heck coupling reaction as the key step were synthesized and screened against a panel of six oral cavity pathogens for their antimicrobial activity. Four compounds (9-12) showed two to fourfold and four to eightfold better activity (MIC 0.25-16 microg/ml) than bakuchiol and triclosan respectively. These compounds effectively inhibit the biofilm formation of single and multiple species at 2 - 8 x MICs. 4- and 4'-Hydroxy/methoxy styryl moieties of the bakuchiol derivatives play a pivotal role towards the activity as established in the SAR studies. Mechanism of action studies revealed microbial membrane structure disruption as the probable mode of action of these compounds.