Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

Carcinogenesis mechanisms of Fusobacterium nucleatum

Transformed cells of cancers may be related to stromal cells, immune cells, and some bacteria such as Fusobacterium nucleatum. This review aimed to evaluate carcinogenesis mechanisms of Fusobacterium spp. in the oral cavity, pancreatic and colorectal cancers. These cancers are the three of the ten most prevalence cancer in the worldwide. Recent findings demonstrated that F. nucleatum could be considered as the risk factor for these cancers. The most important carcinogenesis mechanisms of F. nucleatum are chronic infection, interaction of cell surface molecules of these bacteria with immune system and stromal cells, immune evasion and immune suppression. However, there are some uncertainty carcinogenesis mechanisms about these bacteria, but this review evaluates almost all the known mechanisms. Well-characterized virulence factors of F. nucleatum such as FadA, Fap2, LPS and cell wall extracts may act as effector molecules in the shift of normal epithelial cells to tumor cells. These molecules may provide new targets, drugs, and strategies for therapeutic intervention.

Streptococcus mutans SpaP binds to RadD of Fusobacterium nucleatum ssp. polymorphum

Adhesin-mediated bacterial interspecies interactions are important elements in oral biofilm formation. They often occur on a species-specific level, which could determine health or disease association of a biofilm community. Among the key players involved in these processes are the ubiquitous fusobacteria that have been recognized for their ability to interact with numerous different binding partners. Fusobacterial interactions with Streptococcus mutans, an important oral cariogenic pathogen, have previously been described but most studies focused on binding to non-mutans streptococci and specific cognate adhesin pairs remain to be identified. Here, we demonstrated differential binding of oral fusobacteria to S. mutans. Screening of existing mutant derivatives indicated SpaP as the major S. mutans adhesin specific for binding to Fusobacterium nucleatum ssp. polymorphum but none of the other oral fusobacteria tested. We inactivated RadD, a known adhesin of F. nucleatum ssp. nucleatum for interaction with a number of gram-positive species, in F. nucleatum ssp. polymorphum and used a Lactococcus lactis heterologous SpaP expression system to demonstrate SpaP interaction with RadD of F. nucleatum ssp. polymorphum. This is a novel function for SpaP, which has mainly been characterized as an adhesin for binding to host proteins including salivary glycoproteins. In conclusion, we describe an additional role for SpaP as adhesin in interspecies adherence with RadD-SpaP as the interacting adhesin pair for binding between S. mutans and F. nucleatum ssp. polymorphum. Furthermore, S. mutans attachment to oral fusobacteria appears to involve species- and subspecies-dependent adhesin interactions.

Antibiotic effects against periodontal bacteria in organ cultured tissue

Mechanical reduction of infectious bacteria by using physical instruments is considered the principal therapeutic strategy for periodontal disease; addition of antibiotics is adjunctive. However, local antibiotic treatment, combined with conventional mechanical debridement, has recently been shown to be more effective in periodontitis subjects with type 2 diabetes. This suggests that some bacteria may invade the inflamed inner gingival epithelium, and mechanical debridement alone will be unable to reduce these bacteria completely. Therefore, we tried to establish infected organ culture models that mimic the inner gingival epithelium and aimed to see the effects of antibiotics in these established models. Mouse dorsal skin epithelia were isolated, and periodontal bacteria were injected into the epithelia. Infected epithelia were incubated with test antibiotics, and colony-forming ability was evaluated. Results indicated that effective antibiotics differed according to injected bacteria and the bacterial combinations tested. Overall, in organ culture model, the combination of amoxicillin or cefdinir and metronidazole compensate for the effects of less effective bacterial combinations on each other. This in vitro study would suggest effective periodontal treatment regimens, especially for severe periodontitis.

Inhibition of the MurA enzyme in Fusobacterium nucleatum by potential inhibitors identified through computational and in vitro approaches

Inhibition of MurA in open conformation by orientin and in closed conformation by quercetin-3-O-d-glucuronide with efficient inhibitory constant values.

Evaluation of the microbiome in children's appendicitis

BACKGROUND/AIM

The role of the microbiome has been widely discussed in the etiology of appendicitis. The primary aim was to evaluate the microbiome in the normal appendix and in appendicitis specifically divided into the three clinically and histopathologically defined grades of inflammation. Secondary aims were to examine whether there were any microbiome differences between proximal and distal appendices, and relate the microbiome with histopathological findings.

METHODS

A prospective pilot study was conducted of children undergoing appendectomy for appendicitis. The diagnosis was based on histopathological analysis. Children with incidental appendectomy were used as controls. The proximal and distal mucosa from the appendices were analyzed with 16S rRNA gene sequencing.

RESULTS

A total of 22 children, 3 controls and 19 appendicitis patients; 11 phlegmonous, 4 gangrenous, and 4 perforated appendices, were prospectively included. The amount of Fusobacterium increased and Bacteroides decreased in phlegmonous and perforated appendicitis compared to controls, but statistical significance was not reached, and this pattern was not seen in gangrenous appendicitis. No relation could be seen between different bacteria and the grade of inflammation, and there was a wide variation of abundances at phylum, genus, and species level within every specific group of patients. Further, no significant differences could be detected when comparing the microbiome in proximal and distal mucosa, which may be because the study was underpowered. A trend with more abundance of Fusobacteria in the distal mucosa was seen in appendicitis patients with obstruction (25 and 13 %, respectively, p = 0.06).

CONCLUSION

The pattern of microbiome differed not only between groups, but also within groups. However, no statistically significant differences could be found in the microbiome between groups or clinical conditions. No correlation between a specific bacteria and grade of inflammation was found. In the vast majority of cases of appendicitis, changes in microbiome do not seem to be the primary event. Since there seem to be differences in microbiome patterns depending on the sample site, the exact localization of biopsy sampling must be described in future studies.

Saliva: a Dynamic Proteome

The proteome of whole saliva, in contrast to that of serum, is highly susceptible to a variety of physiological and biochemical processes. First, salivary protein secretion is under neurologic control, with protein output being dependent on the stimulus. Second, extensive salivary protein modifications occur in the oral environment, where a plethora of host- and bacteria-derived enzymes act on proteins emanating from the glandular ducts. Salivary protein biosynthesis starts with the transcription and translation of salivary protein genes in the glands, followed by post-translational processing involving protein glycosylation, phosphorylation, and proteolysis. This gives rise to salivary proteins occurring in families, consisting of structurally closely related family members. Once glandular secretions enter the non-sterile oral environment, proteins are subjected to additional and continuous protein modifications, leading to extensive proteolytic cleavage, partial deglycosylation, and protein-protein complex formation. All these protein modifications occur in a dynamic environment dictated by the continuous supply of newly synthesized proteins and removal by swallowing. Understanding the proteome of whole saliva in an environment of continuous turnover will be a prerequisite to gain insight into the physiological and pathological processes relevant to oral health, and be crucial for the identification of meaningful biomarkers for oral disease.

Noncontiguous finished genome sequence and description of Fusobacterium massiliense sp. nov. isolated from human duodenum

The strain Marseille-P2749^T (= CSUR P2749 = DSM 103085) was isolated as part of culturomics study from a liquid duodenum sample from a French man. Bacterial cells were Gram-negative bacilli, fusiform shaped and non–spore forming, and they grew in microaerophilic and anaerobic atmosphere. Its genome is 1 809 169 bp long and contains 1646 protein-coding genes. The DNA G+C content was 27.33 mol%. This strain exhibited a 95.9% sequence similarity with Fusobacterium periodonticum, the phylogenetically closest species with standing in nomenclature. Strain Marseille-P2749^T is suggested to be a novel species belonging to the genus Fusobacterium, for which the name Fusobacterium massiliense sp. nov. is proposed.

Porphyromonas gingivalis Capsule-Mediated Coaggregation as a Virulence Factor in Mixed Infection With Fusobacterium nucleatum

BACKGROUND

Porphyromonas gingivalis (Pg) capsule enables evasion from phagocytosis, invasion of keratinocytes, and bacterial survival. In mixed infection, the capsule also participates in coaggregation, which may lead to characteristic virulence not present in the monoinfection. The aim of this study is to evaluate the role of Pg capsule as a virulence factor in coaggregated mixed infection with Fusobacterium nucleatum (Fn).

METHODS

Mixed infections containing Fn and non-capsulated or capsulated strains of Pg were compared with the same infection with lactose as coaggregation inhibitor. Murine experimental periodontitis was used to assess disease severity. Primary polymorphonuclear leukocytes and keratinocytes were used to examine phagocytosis and bacterial invasion, respectively.

RESULTS

Mixed infection with capsulated Pg augmented alveolar bone loss compared with that of mixed infection with non-capsulated Pg. Addition of lactose led to attenuation of bone loss in the capsulated mixed infection and to intensification of bone loss in the non-capsulated mixed infection. In the latter mixed infection, Fn evaded phagocytosis, whereas in the capsulated mixed infection Pg displayed a greater capacity for invasion of keratinocytes.

CONCLUSIONS

Pg capsule was found to serve as a unique virulence factor in mixed infection with Fn. Capsule-dependent coaggregation led to augmented invasion of Pg and may be responsible for the severity of disease after mixed infection with Fn.

Strain-Specific Impact of Fusobacterium nucleatum on Neutrophil Function

BACKGROUND

Neutrophil function is critical for initiation and progression of infecto-inflammatory diseases. Key quorum-sensing plaque bacteria, such as Fusobacterium nucleatum, act as bridging species between early and late colonizer pathogens, such as Porphyromonas gingivalis, as the biofilm ages and periodontal inflammation increases. This study is designed to determine impact of different F. nucleatum strains on neutrophil function.

METHODS

Cells of human promyelocytic leukemia cell line-60 were differentiated into neutrophil-like cells and cultured with F. nucleatum strains of subspecies (ssp.) nucleatum ATCC 25586, ssp. polymorphum ATCC 10953, and ssp. vincentii ATCC 49256. Neutrophil phagocytosis of F. nucleatum strains and neutrophil apoptosis were analyzed by flow cytometry. Superoxide generation was measured by cytochrome C reduction in the presence and absence of N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) (1 μM) stimulation. Proinflammatory cytokine release was determined after 2, 6, and 24 hours of culture in the presence/absence of different F. nucleatum strains. Expression of Toll-like receptor (TLR)2, TLR4, and nuclear factor (NF)-kappa B mRNA levels were analyzed using real-time quantitative polymerase chain reaction. Each experiment was repeated at least three times in triplicate. Data were analyzed using analysis of variance followed by post hoc Bonferroni correction.

RESULTS

All strains of F. nucleatum significantly increased phagocytic capacity of neutrophils. Neutrophil phagocytosis of F. nucleatum ssp. polymorphum was significantly greater than that of F. nucleatum ssp. vincentii and ssp. nucleatum (P <0.001). F. nucleatum ssp. nucleatum and ssp. polymorphum significantly blocked fMLP-induced superoxide generation (P <0.001). Although F. nucleatum vincentii also reduced superoxide generation (25%), the impact was not as strong as that of ssp. nucleatum (83%) and ssp. polymorphum (100%). All F. nucleatum strains stimulated significant increase in neutrophil apoptosis compared with control (P <0.001) and significantly increased expression of NF-κB mRNA in neutrophils (P <0.05). Levels of interleukin-8 and tumor necrosis factor-α produced by neutrophils were significantly increased in all F. nucleatum groups compared with control (P <0.001).

CONCLUSIONS

These findings suggest that different strains of F. nucleatum impact neutrophil function in different ways. Two of three subspecies blocked neutrophil superoxide generation in response to a secondary stimulus, preventing oxidative killing by neutrophils. The direct role of bridging species in pathogenesis of periodontitis may be greater than previously suspected in which they create a favorable environment for pathogenic transition of the dental ecosystem.

Evaluation of antibody level against Fusobacterium nucleatum in the serological diagnosis of colorectal cancer

Fusobacterium nucleatum (F. nucleatum, Fn) is associated with the colorectal cancer (CRC). Fn-infection could induce significant levels of serum Fn-specific antibodies in human and mice. The objective of this study was to identify Fn-infection that elicit a humoral response in patients with CRC and evaluate the diagnostic performance of serum anti-Fn antibodies. In this work, we showed the mean absorbance value of anti-Fn-IgA and -IgG in the CRC group were significantly higher than those in the benign colon disease group and healthy control group (P < 0.001). The sensitivity and specificity of ELISA for the detection of anti-Fn-IgA were 36.43% and 92.71% based on the optimal cut-off. The combination of anti-Fn-IgA and carcino-embryonic antigen (CEA) was better for diagnosing CRC (Sen: 53.10%, Spe: 96.41%; AUC = 0.848). Furthermore, combining anti-Fn-IgA with CEA and carbohydrate antigen 19-9 (CA19-9) (Sen: 40.00%, Spe: 94.22%; AUC = 0.743) had the better ability to classify CRC patients with stages I-II. These results suggested that Fn-infection elicited high level of serum anti-Fn antibodies in CRC patients, and serum anti-Fn-IgA level may be a potential diagnosing biomarker for CRC. Serum anti-Fn-IgA in combination with CEA and CA19-9 increases the sensitivity of detecting early CRC.

D-Galactose as an autoinducer 2 inhibitor to control the biofilm formation of periodontopathogens

Autoinducer 2 (AI-2) is a quorum sensing molecule to which bacteria respond to regulate various phenotypes, including virulence and biofilm formation. AI-2 plays an important role in the formation of a subgingival biofilm composed mostly of Gram-negative anaerobes, by which periodontitis is initiated. The aim of this study was to evaluate D-galactose as an inhibitor of AI-2 activity and thus of the biofilm formation of periodontopathogens. In a search for an AI-2 receptor of Fusobacterium nucleatum, D-galactose binding protein (Gbp, Gene ID FN1165) showed high sequence similarity with the ribose binding protein (RbsB), a known AI-2 receptor of Aggregatibacter actinomycetemcomitans. D-Galactose was evaluated for its inhibitory effect on the AI-2 activity of Vibrio harveyi BB152 and F. nucleatum, the major coaggregation bridge organism, which connects early colonizing commensals and late pathogenic colonizers in dental biofilms. The inhibitory effect of D-galactose on the biofilm formation of periodontopathogens was assessed by crystal violet staining and confocal laser scanning microscopy in the absence or presence of AI-2 and secreted molecules of F. nucleatum. D-Galactose significantly inhibited the AI-2 activity of V. harveyi and F. nucleatum. In addition, D-galactose markedly inhibited the biofilm formation of F. nucleatum, Porphyromonas gingivalis, and Tannerella forsythia induced by the AI-2 of F. nucleatum without affecting bacterial growth. Our results demonstrate that the Gbp may function as an AI-2 receptor and that galactose may be used for prevention of the biofilm formation of periodontopathogens by targeting AI-2 activity.

Caveolin-1 serves as a negative effector in senescent human gingival fibroblasts during Fusobacterium nucleatum infection

It is well established that aging is associated with increased susceptibility to infectious diseases. Fusobacterium nucleatum is a well-known bacterial species that plays a central bridging role between early and late colonizers in the human oral cavity. Further, the ability of F. nucleatum to invade gingival fibroblasts (GFs) is critical to the development of periodontal diseases. However, the mechanisms underlying the age-related infection of GFs by F. nucleatum remain unknown. We used young (fourth passage) and senescent (22nd passage) GFs to investigate the mechanisms of F. nucleatum infection in aged GFs and first observed increased invasion of F. nucleatum in senescent GFs. We also found that the co-localization of caveolin-1 (Cav-1), a protein marker of aging, with F. nucleatum and the knockdown of Cav-1 in GFs reduced F. nucleatum invasion. Additionally, F. nucleatum infection triggered the production of reactive oxygen species (ROS) through activation of NADPH oxidase in GFs, but senescent GFs exhibited significantly lower levels of NADPH oxidase activity and ROS production compared with young GFs in both the uninfected and infected conditions. Also, senescent GFs exhibited a decline in proinflammatory cytokine production and extracellular signal regulated kinase (ERK) phosphorylation following F. nucleatum infection. Interestingly, the knockdown of Cav-1 in senescent GFs increased NADPH oxidase activity and caused the upregulation of interleukin-6 and interleukin-8 and the phosphorylation of ERK. Collectively, the increased expression of Cav-1 might play a critical role in F. nucleatum invasion and could hinder the host response in senescent GFs.

Anti-biofilm Activities from Resveratrol against Fusobacterium nucleatum

Fusobacterium nucleatum is a Gram-negative, anaerobic bacterium that plays an important role in dental plaque biofilm formation. In this study, we evaluate the effect of resveratrol, a phytoalexin compound, on F. nucleatum biofilm formation. The effects of different concentrations of resveratrol on biofilms formed on 96-well microtiter plates at different time points were determined by the MTT assay. The structures and thicknesses of the biofilm were observed by confocal laser scanning microscopy (CLSM), and gene expression was investigated by real-time PCR. The results showed that resveratrol at sub-MIC levels can significantly decrease biofilm formation, whereas it does not affect the bacterial growth rate. It was observed by CLSM images that the biofilm was visually decreased with increasing concentrations of resveratrol. Gene expression was down regulated in the biofilm in the presence of resveratrol. Our results revealed that resveratrol can effectively inhibit biofilm formation.

Target identification in Fusobacterium nucleatum by subtractive genomics approach and enrichment analysis of host-pathogen protein-protein interactions

Background

Fusobacterium nucleatum, a well studied bacterium in periodontal diseases, appendicitis, gingivitis, osteomyelitis and pregnancy complications has recently gained attention due to its association with colorectal cancer (CRC) progression. Treatment with berberine was shown to reverse F. nucleatum-induced CRC progression in mice by balancing the growth of opportunistic pathogens in tumor microenvironment. Intestinal microbiota imbalance and the infections caused by F. nucleatum might be regulated by therapeutic intervention. Hence, we aimed to predict drug target proteins in F. nucleatum, through subtractive genomics approach and host-pathogen protein-protein interactions (HP-PPIs). We also carried out enrichment analysis of host interacting partners to hypothesize the possible mechanisms involved in CRC progression due to F. nucleatum.

Results

In subtractive genomics approach, the essential, virulence and resistance related proteins were retrieved from RefSeq proteome of F. nucleatum by searching against Database of Essential Genes (DEG), Virulence Factor Database (VFDB) and Antibiotic Resistance Gene-ANNOTation (ARG-ANNOT) tool respectively. A subsequent hierarchical screening to identify non-human homologous, metabolic pathway-independent/pathway-specific and druggable proteins resulted in eight pathway-independent and 27 pathway-specific druggable targets. Co-aggregation of F. nucleatum with host induces proinflammatory gene expression thereby potentiates tumorigenesis. Hence, proteins from IBDsite, a database for inflammatory bowel disease (IBD) research and those involved in colorectal adenocarcinoma as interpreted from The Cancer Genome Atlas (TCGA) were retrieved to predict drug targets based on HP-PPIs with F. nucleatum proteome. Prediction of HP-PPIs exhibited 186 interactions contributed by 103 host and 76 bacterial proteins. Bacterial interacting partners were accounted as putative targets. And enrichment analysis of host interacting partners showed statistically enriched terms that were in positive correlation with CRC, atherosclerosis, cardiovascular, osteoporosis, Alzheimer’s and other diseases.

Conclusion

Subtractive genomics analysis provided a set of target proteins suggested to be indispensable for survival and pathogenicity of F. nucleatum. These target proteins might be considered for designing potent inhibitors to abrogate F. nucleatum infections. From enrichment analysis, it was hypothesized that F. nucleatum infection might enhance CRC progression by simultaneously regulating multiple signaling cascades which could lead to up-regulation of proinflammatory responses, oncogenes, modulation of host immune defense mechanism and suppression of DNA repair system.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0700-0) contains supplementary material, which is available to authorized users.

Selected dietary (poly)phenols inhibit periodontal pathogen growth and biofilm formation

Periodontitis (PD) is a chronic infectious disease mediated by bacteria in the oral cavity. (Poly)phenols (PPs), ubiquitous in plant foods, possess antimicrobial activities and may be useful in the prevention and management of periodontitis. The objective of this study was to test the antibacterial effects of selected PPs on periodontal pathogens, on both planktonic and biofilm modes of growth. Selected PPs (n = 48) were screened against Streptococcus mitis (S. mitis), Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis (P. gingivalis). The antibacterial potential of each compound was evaluated in terms of planktonic minimum inhibitory concentration (PMIC) and planktonic minimum bactericidal concentration (PMBC) using standardized broth microdilution assays. The most active PPs were further tested for their effect on mono-species and multi-species biofilms using a colorimetric resazurin-based viability assay and scanning electron microscopy. Of the 48 PPs tested, 43 showed effective inhibition of planktonic growth of one or more test strains, of which curcumin was the most potent (PMIC range = 7.8-62.5 μg mL(-1)), followed by pyrogallol (PMIC range = 2.4-2500 μg mL(-1)), pyrocatechol (MIC range = 4.9-312.5 μg mL(-1)) and quercetin (PMIC range = 31.2-500 μg mL(-1)). At this concentration, adhesion of curcumin and quercetin to the substrate also inhibited adhesion of S. mitis, and biofilm formation and maturation. While both curcumin and quercetin were able to alter architecture of mature multi-species biofilms, only curcumin-treated biofilms displayed a significantly reduced metabolic activity. Overall, PPs possess antibacterial activities against periodontopathic bacteria in both planktonic and biofilm modes of growth. Further cellular and in vivo studies are necessary to confirm their beneficial activities and potential use in the prevention and or treatment of periodontal diseases.

Fusobacterial head and neck infections in children

Fusobacterium species are increasingly recognized as a cause of head and neck infections in children. These infections include acute and chronic otitis, sinusitis, mastoiditis, and tonsillitis; peritonsillar and retropharyngeal abscesses; Lemierre syndrome; post-anginal cervical lymphadenitis; and periodontitis. They can also be involved in brain abscess and bacteremia associated with head and neck infections. This review describes the clinical spectrum of head and neck fusobacterial infection in children and their management.

Fusobacterium nucleatum: a rare cause of pyogenic liver abscess

While pyogenic liver abscesses are uncommon, they are associated with significant mortality and morbidity. Most pyogenic liver abscesses are polymicrobial and are caused by enteric bacteria and anaerobes. Rarely, mono-microbial infections may occur, typically in immunocompromised individuals. We report the unusual case of a 69 year-old immunocompetent female who developed a pyogenic liver abscess due to Fusobacterium nucleatum infection, likely from a dental source. Poor oropharyngeal hygiene seems to have a major role in infection from this organism and therefore F. nucleatum should be considered as a differential for causes of pyogenic liver abscess in such patients. Drainage of the abscess and antibiotic therapy are the mainstays of therapy.

Fusobacterium nucleatum Alters Atherosclerosis Risk Factors and Enhances Inflammatory Markers with an Atheroprotective Immune Response in ApoE(null) Mice

The American Heart Association supports an association between periodontal disease (PD) and atherosclerotic vascular disease (ASVD) but does not as of yet support a causal relationship. Recently, we have shown that major periodontal pathogens Porphyromonas gingivalis and Treponema denticola are causally associated with acceleration of aortic atherosclerosis in ApoEnull hyperlipidemic mice. The aim of this study was to determine if oral infection with another significant periodontal pathogen Fusobacterium nucleatum can accelerate aortic inflammation and atherosclerosis in the aortic artery of ApoEnull mice. ApoEnull mice (n = 23) were orally infected with F. nucleatum ATCC 49256 and euthanized at 12 and 24 weeks. Periodontal disease assessments including F. nucleatum oral colonization, gingival inflammation, immune response, intrabony defects, and alveolar bone resorption were evaluated. Systemic organs were evaluated for infection, aortic sections were examined for atherosclerosis, and inflammatory markers were measured. Chronic oral infection established F. nucleatum colonization in the oral cavity, induced significant humoral IgG (P=0.0001) and IgM (P=0.001) antibody response (12 and 24 weeks), and resulted in significant (P=0.0001) alveolar bone resorption and intrabony defects. F. nucleatum genomic DNA was detected in systemic organs (heart, aorta, liver, kidney, lung) indicating bacteremia. Aortic atherosclerotic plaque area was measured and showed a local inflammatory infiltrate revealed the presence of F4/80+ macrophages and CD3+ T cells. Vascular inflammation was detected by enhanced systemic cytokines (CD30L, IL-4, IL-12), oxidized LDL and serum amyloid A, as well as altered serum lipid profile (cholesterol, triglycerides, chylomicrons, VLDL, LDL, HDL), in infected mice and altered aortic gene expression in infected mice. Despite evidence for systemic infection in several organs and modulation of known atherosclerosis risk factors, aortic atherosclerotic lesions were significantly reduced after F. nucleatum infection suggesting a potential protective function for this member of the oral microbiota.

Lemierre Syndrome Presenting as Acute Mastoiditis in a 2-Year-Old Girl with Congenital Dwarfism

Lemierre syndrome is defined by septic thrombophlebitis of the internal jugular vein caused by Fusobacterium. Historically, these infections originate from the oropharynx and typically are seen in older children, adolescents and young adults. More recently, otogenic sources in younger children have been described with increasing frequency. We present a case of a two-year old, who initially developed an otitis media with perforation of the tympanic membrane and went on to develop mastoiditis and non-occlusive thrombosis of the venous sinus and right internal jugular vein. Fusobacterium necrophorum was grown from operative cultures of the mastoid, ensuing computed tomography scan revealed occlusion of the internal jugular vein and the patient was successfully treated with clindamycin, ciprofloxacin and enoxaparin. This case demonstrates the importance of considering Fusobacterium in otogenic infections and the consideration of Lemierre syndrome when F. necrophorum is identified

Identification of subgingival periodontal pathogens and association with the severity of periodontitis in patients with chronic kidney diseases: a cross-sectional study

BACKGROUND

The aim of our study was to assess the subgingival profile of 9 periodontal pathogens, by means of real-time PCR, in a group of predialysis chronic kidney disease patients with and without periodontal disease and to identify the risk factors associated with periodontal disease in these patients.

MATERIAL AND METHODS

This is a single centre cross-sectional cohort study performed on 70 CKD patients. Patients received a full-mouth periodontal examination and the following parameters were assessed: periodontal pocket depth (PPD), clinical attachment level, bleeding on probing, and plaque index; subgingival biofilm samples were collected from the deepest periodontal pocket of each quadrant and were pooled in one transporting unit. Clinical data were drawn from the medical file of the patients.

RESULTS

T. denticola (P = 0.001), T. forsythia (P < 0.001), and P. micros (P = 0.003) are significantly associated with periodontal disease in CKD subjects but in a multivariate model only age and T. forsythia remain independent risk factors for periodontal disease in patients with CKD.

CONCLUSIONS

In our cohort, age and T. forsythia are independently associated with periodontitis in CKD patients. Within the limits of this study, CKD was not significantly associated with a particular subgingival periodontal pathogens profile in periodontitis patients.

High individuality of respiratory bacterial communities in a large cohort of adult cystic fibrosis patients under continuous antibiotic treatment

Background

Routine clinical diagnostics of CF patients focus only on a restricted set of well-known pathogenic species. Recent molecular studies suggest that infections could be polymicrobial with many bacteria not detected by culture-based diagnostics.

Methodology and Principal Findings

A large cohort of 56 adults with continuous antibiotic treatment was studied and different microbial diagnostic methods were compared, including culture-independent and culture-based bacterial diagnostics. A total of 72 sputum samples including longitudinal observations was analysed by 16S rRNA gene sequence comparison. Prevalence of known pathogens was highly similar among all methods but the vast spectrum of bacteria associated with CF was only revealed by culture-independent techniques. The sequence comparison enabled confident determination of the bacterial community composition and revealed a high diversity and individuality in the communities across the cohort. Results of microbiological analyses were further compared with individual host factors, such as age, lung function and CFTR genotype. No statistical relationship between these factors and the diversity of the entire community or single bacterial species could be identified. However, patients with non-ΔF508 mutations in the CFTR gene often had low abundances of Pseudomonas aeruginosa. Persistence of specific bacteria in some communities was demonstrated by longitudinal analyses of 13 patients indicating a potential clinical relevance of anaerobic bacteria, such as Fusobacterium nucleatum and Streptococcus millerii.

Conclusions

The high individuality in community composition and the lack of correlation to clinical host factors might be due to the continuous treatment with antibiotics. Since this is current practice for adult CF patients, the life-long history of the patient and the varying selection pressure on the related microbial communities should be a focus of future studies and its relation to disease progression. These studies should be substantially larger, providing more molecular information on the microbial communities complemented by detailed genetic assessment of the host.

Fusobacterium nucleatum subspecies identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry

We explored the use of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for identification of Fusobacterium nucleatum subspecies. MALDI-TOF MS spectra of five F. nucleatum subspecies (animalis, fusiforme, nucleatum, polymorphum, and vincentii) were analyzed and divided into four distinct clusters, including subsp. animalis, nucleatum, polymorphum, and fusiforme/vincentii. MALDI-TOF MS with the modified SARAMIS database further correctly identified 28 of 34 F. nucleatum clinical isolates to the subspecies level.

Fap2 of Fusobacterium nucleatum is a galactose-inhibitable adhesin involved in coaggregation, cell adhesion, and preterm birth

Fusobacterium nucleatum is a common oral anaerobe involved in periodontitis that is known to translocate and cause intrauterine infections. In the oral environment, F. nucleatum adheres to a large diversity of species, facilitating their colonization and creating biological bridges that stabilize the multispecies dental biofilm. Many of these interactions (called coadherences or coaggregations) are galactose sensitive. Galactose-sensitive interactions are also involved in the binding of F. nucleatum to host cells. Hemagglutination of some F. nucleatum strains is also galactose sensitive, suggesting that a single galactose-sensitive adhesin might mediate the interaction of fusobacteria with many partners and targets. In order to identify the fusobacterial galactose-sensitive adhesin, a system for transposon mutagenesis in fusobacteria was created. The mutant library was screened for hemagglutination deficiency, and three clones were isolated. All three clones were found to harbor the transposon in the gene coding for the Fap2 outer membrane autotransporter. The three fap2 mutants failed to show galactose-inhibitable coaggregation with Porphyromonas gingivalis and were defective in cell binding. A fap2 mutant also showed a 2-log reduction in murine placental colonization compared to that of the wild type. Our results suggest that Fap2 is a galactose-sensitive hemagglutinin and adhesin that is likely to play a role in the virulence of fusobacteria.

Anti-inflammatory, Antioxidant and Antimicrobial Effects of Artemisinin Extracts from Artemisia annua L

The anti-inflammatory, antioxidant, and antimicrobial properties of artemisinin derived from water, methanol, ethanol, or acetone extracts of Artemisia annua L. were evaluated. All 4 artemisinin-containing extracts had anti-inflammatory effects. Of these, the acetone extract had the greatest inhibitory effect on lipopolysaccharide-induced nitric oxide (NO), prostaglandin E₂ (PGE₂), and proinflammatory cytokine (IL-1β , IL-6, and IL-10) production. Antioxidant activity evaluations revealed that the ethanol extract had the highest free radical scavenging activity, (91.0±3.2%), similar to α-tocopherol (99.9%). The extracts had antimicrobial activity against the periodontopathic microorganisms Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum subsp. animalis, Fusobacterium nucleatum subsp. polymorphum, and Prevotella intermedia. This study shows that Artemisia annua L. extracts contain anti-inflammatory, antioxidant, and antimicrobial substances and should be considered for use in pharmaceutical products for the treatment of dental diseases.

Myopericarditis associated with Fusobacterium nucleatum-caused liver abscess

A wide clinical spectrum of bacteremic disease caused by Fusobacterium has been presented in this journal. We wish to extend this spectrum by presenting a case of myopericarditis resulting from a liver abscess caused by F. nucleatum. While F. nucleatum plays an important role in periodontal disease, and has been isolated from skin ulcers, liver abscesses, urinary tract infections, and endocarditis, a single case of F. nucleatum-induced pericarditis is documented in the literature.

Periodontal and peri-implant microbiota in patients with healthy and inflamed periodontal and peri-implant tissues

OBJECTIVE

To compare the prevalence and levels of six bacterial pathogens within the subgingival/submucosal microbiota at teeth versus implants with various clinical conditions.

MATERIAL AND METHODS

Twenty-two Chinese were included. Four subgingival/submucosal sites were selected for microbiological sampling within each subject, that is, (1) healthy peri-implant tissues; (2) peri-implantitis [PPD ≥ 5 mm, presence of bleeding on probing (BOP) and confirmed radiographic bone loss]; (3) healthy gingiva; and (4) periodontitis (PPD ≥4 mm). Subgingival/submucosal plaque was sampled using paper points. Quantitative real-time polymerase chain reaction (q-PCR) was used to quantify six pathogens, including Porphyromonas gingivalis (P.g.), Treponema denticola (T.d.), Aggregatibacter actinomycetemcomitans (A.a.), Fusobacterium nucleatum (F.n.), Prevotella intermedia (P.i.), and Staphylococcus aureus (S.a.). Counts were log10-transformed.

RESULTS

The most commonly detected species were S. a. and F. n., while A. a. and. P. i. had the lowest detection frequency. The detection frequencies of diseased tooth or implant sites for each of the six target species were either equal to or higher than the respective frequencies at the corresponding healthy sites. There were no statistically significant differences for any of the species or clinical sites (P > 0.05, Cochran's Q test). No statistically significant differences in the bacterial loads were found among the four clinical sites; with the exception of F. nucleatum. This was more abundant in periodontitis sites (P = 0.023, Friedman's 2-way anova). Both periodontal and peri-implant sites, irrespective of their health status, were revealed to harbor S. aureus cells. The log10-transformed loads of S. aureus were approximately 3.5 within each of the clinical sites (P = 0.232). This was the highest of the six species analyzed.

CONCLUSIONS

Within the same subjects, putative periodontal pathogens were common to both periodontal and peri-implant sites irrespective of health status. The prevalence and levels of P. gingivalis and F. nucleatum were significantly associated with periodontitis, but not with peri-implantitis. A. actinomycetemcomitans was associated with both disease conditions, periodontitis and peri-implantitis, but not with either gingival or mucosal health.

Evolution of invasion in a diverse set of Fusobacterium species

The diverse Fusobacterium genus contains species implicated in multiple clinical pathologies, including periodontal disease, preterm birth, and colorectal cancer. The lack of genetic tools for manipulating these organisms leaves us with little understanding of the genes responsible for adherence to and invasion of host cells. Actively invading Fusobacterium species can enter host cells independently, whereas passively invading species need additional factors, such as compromise of mucosal integrity or coinfection with other microbes. We applied whole-genome sequencing and comparative analysis to study the evolution of active and passive invasion strategies and to infer factors associated with active forms of host cell invasion. The evolution of active invasion appears to have followed an adaptive radiation in which two of the three fusobacterial lineages acquired new genes and underwent expansions of ancestral genes that enable active forms of host cell invasion. Compared to passive invaders, active invaders have much larger genomes, encode FadA-related adhesins, and possess twice as many genes encoding membrane-related proteins, including a large expansion of surface-associated proteins containing the MORN2 domain of unknown function. We predict a role for proteins containing MORN2 domains in adhesion and active invasion. In the largest and most comprehensive comparison of sequenced Fusobacterium species to date, we have generated a testable model for the molecular pathogenesis of Fusobacterium infection and illuminate new therapeutic or diagnostic strategies.

Fusobacterium species have recently been implicated in a broad spectrum of human pathologies, including Crohn’s disease, ulcerative colitis, preterm birth, and colorectal cancer. Largely due to the genetic intractability of member species, the mechanisms by which Fusobacterium causes these pathologies are not well understood, although adherence to and active invasion of host cells appear important. We examined whole-genome sequence data from a diverse set of Fusobacterium species to identify genetic determinants of active forms of host cell invasion. Our analyses revealed that actively invading Fusobacterium species have larger genomes than passively invading species and possess a specific complement of genes—including a class of genes of unknown function that we predict evolved to enable host cell adherence and invasion. This study provides an important framework for future studies on the role of Fusobacterium in pathologies such as colorectal cancer.

Fusobacterium hwasookii sp. nov., Isolated from a Human Periodontitis Lesion

In this study, we classified the five strains (ChDC F128(T), ChDC F145, ChDC F174, ChDC F206, and ChDC F300) as a novel species of genus Fusobacterium by DNA-DNA hybridization and multi-locus phylogenetic analysis (MLPA), based on a single sequence (24,715 bp) of 22 concatenated housekeeping genes, with morphological and chemotaxonomic characteristics. DNA-DNA hybridization data showed that the values of genomic relatedness between ChDC F128(T) and each of the other novel strains were ranged from 79.0 to 82.6 %, while those of genomic relatedness between ChDC F128(T) and type strain of each of subspecies of F. nucleatum or Fusobacterium periodonticum were ranged from 40.9 to 54.4 %. MLPA revealed that the 5 strains were clustered as one group and clearly discriminated with F. nucleatum and F. periodonticum with 100 % bootstrap value. The DNA G+C content of the five novel strains were ranged from 26.9 to 27.0 mol%. The cellular fatty acid analysis of clinical isolates and type strains revealed C14:0, C16:0, and cis-9 C16:1 as the major fatty acids. The cell wall peptidoglycan of the 5 strains was comprised of meso-lanthionine. These results show that the 5 strains are novel species and belong to the genus Fusobacterium. Strain ChDC F128(T) (=KCOM 1249(T) = KCTC 5108(T) = JCM 30218(T)) is suggested to be the type strain of a novel species of genus Fusobacterium, for which the name Fusobacterium hwasookii sp. nov. is proposed.

Proteomics of Fusobacterium nucleatum within a model developing oral microbial community

Fusobacterium nucleatum is a common oral organism that can provide adhesive and metabolic support to developing periodontal bacterial communities. It is within the context of these communities that disease occurs. We have previously reported whole cell proteomics analyses of Porphyromonas gingivalis and Streptococcus gordonii in early-stage communities with each other and with F. nucleatum, modeled using 18 h pellets. Here, we report the adaptation of F. nucleatum to the same experimental conditions as measured by differential protein expression. About 1210 F. nucleatum proteins were detected in single species F. nucleatum control samples, 1192 in communities with P. gingivalis, 1224 with S. gordonii, and 1135 with all three species. Quantitative comparisons among the proteomes revealed important changes in all mixed samples with distinct responses to P. gingivalis or S. gordonii alone and in combination. The results were inspected manually and an ontology analysis conducted using DAVID (Database for annotation, visualization, and integrated discovery). Extensive changes were detected in energy metabolism. All multispecies comparisons showed reductions in amino acid fermentation and a shift toward butanoate as a metabolic byproduct, although the two organism model community with S. gordonii showed increases in alanine, threonine, methionine, and cysteine pathways, and in the three species samples there were increases in lysine and methionine. The communities with P. gingivalis or all three organisms showed reduced glycolysis proteins, but F. nucleatum paired with S. gordonii displayed increased glycolysis/gluconeogenesis proteins. The S. gordonii containing two organism model also showed increases in the ethanolamine pathway while the three species sample showed decreases relative to the F. nucleatum single organism control. All of the nascent model communities displayed reduced translation, lipopolysaccharide, and cell wall biosynthesis, DNA replication and DNA repair.

Increased proliferation and decreased membrane permeability as defense mechanisms of Fusobacterium nucleatum against human neutrophilic peptide-1

Human neutrophilic peptides (HNPs) constitute a class of host defense molecules, which contribute to the non-oxidative killing of bacteria and other microorganisms. Since the adaptability is crucial to bacterial survival in changing environments, it is of interest to know how Fusobacterium nucleatum, the major bridge organism connecting early and late colonizers in dental biofilms, defends itself against HNPs. This study aimed to examine the planktonic growth, membrane permeability, and biofilm formation characteristics as defense mechanisms of F. nucleatum against HNP-1. In all experiments, the type strain of F. nucleatum (ssp. nucleatum ATCC 25586) and two clinical strains (ssp. nucleatum AHN 9508 and ssp. polymorphum AHN 9910) were used. Planktonic growth (measured in colony forming units), capsular polysaccharide production (visualized by Ziehl-Neelsen stain), membrane permeability (demonstrated as N-phenyl-1-naphthylamine uptake), biofilm formation, and established biofilm development (measured as total mass and polysaccharide levels) were analyzed in the presence of 0 μg/ml (control), 1 μg/ml, 5 μg/ml, and 10 μg/ml of HNP-1. Planktonic growth of the strains AHN 9508 and ATCC 25586 were significantly (p<0.05) increased in the presence of HNP-1, while their membrane permeability decreased (p<0.005) in the planktonic form. HNP-1 decreased the biofilm formation of the strains ATCC 25586 and AHN 9910, whereas it increased the growth of the strain AHN 9508 in established biofilms. Capsule formation and polysaccharide production were not observed in any strain. We conclude that the inhibition of the membrane permeability and the increase in planktonic and established biofilm growth could act as bacterial defense mechanisms against neutrophilic defensins. In addition, this strain-dependent survival ability against HNP-1 may explain the variation in the virulence of different F. nucleatum strains.

Phylogeny and molecular signatures for the phylum Fusobacteria and its distinct subclades

The members of the phylum Fusobacteria and its two families, Fusobacteriaceae and Leptotrichiaceae, are distinguished at present mainly on the basis of their branching in the 16S rRNA gene trees and analysis of the internal transcribed spacer sequences in the 16S-23S rDNA. However, no biochemical or molecular characteristics are known that are uniquely shared by all of most members of these groups of bacteria. We report here detailed phylogenetic and comparative analyses on 45 sequenced Fusobacteria genomes to examine their evolutionary relationships and to identify molecular markers that are specific for the members of this phylum. In phylogenetic trees based on 16S rRNA gene sequences or concatenated sequences for 17 conserved proteins, members of the families Fusobacteriaceae and Leptotrichiaceae formed strongly supported clades and were clearly distinguished. In these trees, the species from the genus Fusobacterium also formed a number of well-supported clades. In parallel, comparative analyses on Fusobacteria genomes have identified 44 conserved signature indels (CSIs) in proteins involved in a broad range of functions that are either specific for the phylum Fusobacteria or a number of distinct subclades within this phylum. Seven of these CSIs in important proteins are uniquely present in the protein homologs of all sequenced Fusobacteria and they provide potential molecular markers for this phylum. Six and three other CSIs in other protein sequences are specific for members of the families Fusobacteriaceae and Leptotrichiaceae, respectively, and they provide novel molecular means for distinguishing members of these two families. Fourteen additional CSIs in different proteins, which are specific for either members of the genera Fusobacterium or Leptotrichia, or a number of other well-supported clades of Fusobacteria at multiple phylogenetic levels, provide molecular markers for these groups and information regarding the evolutionary relationships among the members of this phylum. Lastly, the present work has also identified 14 CSIs in divergent proteins that are specific for three specific subclades of Fusobacterium species, which are also indicated to be distinct by phylogenetic analyses. The members of these three Fusobacterium subclades also differ significantly from each other in their whole genome average nucleotide identities values, suggesting that they are possible candidates for recognition as different genera. The molecular markers reported here provide novel means for the identification of members of the phylum Fusobacteria and for their classification.

Ubiquitous sialometabolism present among oral fusobacteria

Fusobacterium nucleatum is a ubiquitous member of the human oral flora and is associated with the development of periodontitis and a variety of other types of polymicrobial infections of the mucosa. In the oral cavity, this species is one of the few that is prevalent in both healthy and diseased subgingival plaque. Using microarray analysis, we examined the transcriptional response of F. nucleatum subspecies nucleatum to whole blood in order to identify some of the genetic responses that might occur during the transition from health to disease. From these studies, we identified a sialic acid catabolism operon that was induced by the presence of blood. We subsequently confirmed that this operon was inducible by the presence of synthetic sialic acid, but we found no evidence suggesting sialic acid was used as a major carbon source. However, this organism was found to possess a de novo synthesized surface sialylation ability that is widely conserved among the various F. nucleatum subspecies as well as in F. periodonticum. We provide evidence that fusobacterial sialylation does occur in the oral cavity irrespective of health status. Interestingly, only a minority of fusobacterial cells exhibit surface sialylation within dental plaque, whereas most cells are uniformly sialylated when grown in pure culture. The implications of these results are discussed.

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.