Streptococcus oralis previously identified as uncommon 'Streptococcus sanguis' in Behçet's disease

Recurrent Aphthous Stomatitis – An Overview

Recurrent aphthous ulcers are common painful mucosal conditions affecting the oral cavity. Despite their high prevalence and knowledge of many etiological factors, the exact mechanism of disease is still not fully understood. There are three different clinical forms of recurrent aphthous stomatitis and the therapy differs depending on it.

The aim of this article is to provide an overview of current knowledge about the possible causes and treatment of recurrent aphthous stomatitis. We discuss its pathogenesis which is currently the least explained in the literature. This review offers scientists and clinicians useful information about clinical presentation, diagnosis, predisposing aetiological factors and recent trends in the management of recurrent aphthous stomatitis.

Oral Health and Its Aetiological Role in Behçet's Disease

Behçet's disease (BD) is a chronic multi-systemic inflammatory disorder characterised by oro-genital ulcers, cutaneous manifestations, ocular, vascular, neurologic and gastrointestinal involvement. Complex interactions operating on the genetic background e.g.(HLA51), of infectious and other environmental agents, together with immune dysregulation impacts on the pathogenesis of BD. This suggests that the environmental factors triggering immune responses may activate clinical manifestations in genetically susceptible individuals. Since oral health forms the basis of all general health both dental and systemic, it is an important component of both Dentistry and Medicine. Oral ulcers are the most common clinical manifestation of oral mucosal health. Changes in the oral environment consequently acts as an infective and immune trigger. In this review, complex interactions between the oral ulcers, the oral microbiome and immune responses together with the course of oral and systemic disease manifestations in BD are discussed in the context of the aetiologic role of oral health.

The possible role of oral microbiome in autoimmunity

OBJECTIVE

The human microbiome refers to the entire habitat, including microorganisms, their genomes and the surrounding environmental conditions of the microbial ecosystem. When the equilibrium between microbial habitats and host is disturbed, dysbiosis is caused. The oral microbiome (OMB) has been implicated in the manifestation of many intra- and extraoral diseases. Lately, there has been an intense effort to investigate and specify the relationship between microbial complexes, especially that of the oral cavity and intestine and autoimmunity. This study aimed to review the current literature about the possible role of the OMB in the pathogenesis of autoimmune diseases.

METHODS

We searched for published articles in English indexed in PubMed, Medline, Research Gate and Google Scholar using a search strategy that included terms for oral microbiome, autoimmune diseases, dysbiosis and next-generation sequencing.

RESULTS

An important number of articles were gathered and used for the description of the possible impact of dysbiosis of OMB in the pathogenesis of Sjögren's syndrome, systemic lupus erythematosus, rheumatoid arthritis, Behcet's disease, Crohn's disease and psoriasis.

CONCLUSION

This review article draws attention to the relationship between OMB and the triggering of a number of autoimmune diseases. Although this specific topic has been previously reviewed, herein, the authors review recent literature regarding the full list of nosological entities related to the OMB, point out the interaction between the microbiome and sex hormones with regard to their role in autoimmunity and discuss novel and promising therapeutic approaches for systemic autoimmune diseases. Furthermore, the question arises of whether the OMB is associated with oral bullous autoimmune diseases.

Behcet’s disease: from heat shock proteins to infections

Background: Behcet’s disease (BD) is a chronic, inflammatory multisystemic condition of unknown etiology. Although the cause of BD is not clear, it is believed to be the result of an autoimmune process triggered by an infectious or environmental agent (possibly local to a geographic region) in a genetically predisposed individual.

Objective: To detail current knowledge of the role of microorganisms in the pathogenesis of BD and review the infectious etiology of this disease.

Methods: The review based on publication in SCOPUS, Science direct, and PubMed.

Results: A microbial infection has been implicated in the development of the disease to explain the strong inflammatory reactions observed, the activation of monocytes and macrophages, and the induction of proinflammatory cytokines and chemokines detected. Common factors linking some of the possible pathogenetic agents are extrinsically induced tissue stress or heat shock proteins, which react with host tissues and elicit significant T-helper type 1 cell responses.

Conclusion: Based on collected data, we conclude that the microorganisms discussed seem to participate and, at least in part, act as triggers during the course of BD. By clarifying the microbial associations of BD and finding its etiology, particularly the causative antigens leading to BD, it would be easier to suggest more effective treatment and preventive strategies for this disease.

Genetic basis of coaggregation receptor polysaccharide biosynthesis in Streptococcus sanguinis and related species

Interbacterial adhesion between streptococci and actinomyces promotes early dental plaque biofilm development. Recognition of coaggregation receptor polysaccharides (RPS) on strains of Streptococcus sanguinis, Streptococcus gordonii and Streptococcus oralis by Actinomyces spp. type 2 fimbriae is the principal mechanism of these interactions. Previous studies of genetic loci for synthesis of RPS (rps) and RPS precursors (rml, galE1 and galE2) in S. gordonii 38 and S. oralis 34 revealed differences between these strains. To determine whether these differences are strain-specific or species-specific, we identified and compared loci for polysaccharide biosynthesis in additional strains of these species and in several strains of the previously unstudied species, S. sanguinis. Genes for synthesis of RPS precursors distinguished the rps loci of different streptococci. Hence, rml genes for synthesis of TDP-L-Rha were in rps loci of S. oralis strains but at other loci in S. gordonii and S. sanguinis. Genes for two distinct galactose epimerases were also distributed differently. Hence, galE1 for epimerization of UDP-Glc and UDP-Gal was in galactose operons of S. gordonii and S. sanguinis strains but surprisingly, this gene was not present in S. oralis. Moreover, galE2 for epimerization of both UDP-Glc and UDP-Gal and UDP-GlcNAc and UDP-GalNAc was at a different locus in each species, including rps operons of S. sanguinis. The findings provide insight into cell surface properties that distinguish different RPS-producing streptococci and open an approach for identifying these bacteria based on the arrangement of genes for synthesis of polysaccharide precursors.

The oral mucosal and salivary microbial community of Behçet's syndrome and recurrent aphthous stomatitis

Background

Behçet's syndrome (BS) is a multisystem immune-related disease of unknown etiology. Recurrent aphthous stomatitis (RAS) is characterized by the presence of idiopathic oral ulceration without extraoral manifestation. The interplay between the oral microbial communities and the immune response could play an important role in the etiology and pathogenesis of both BS and RAS.

Objective

To investigate the salivary and oral mucosal microbial communities in BS and RAS.

Methods

Purified microbial DNA isolated from saliva samples (54 BS, 25 healthy controls [HC], and 8 RAS) were examined by the human oral microbe identification microarray. Cultivable salivary and oral mucosal microbial communities from ulcer and non-ulcer sites were identified by matrix-assisted laser desorption/ionization time-of-flight analysis. Mycobacterium spp. were detected in saliva and in ulcer and non-ulcer oral mucosal brush biopsies following culture on Lowenstein-Jensen slopes and Mycobacterial Growth Indicator Tubes.

Results

There was increased colonization with Rothia denticariosa of the non-ulcer sites of BS and RAS patients (p<0.05). Ulcer sites in BS were highly colonized with Streptococcus salivarius compared to those of RAS (p<0.05), and with Streptococcus sanguinis compared to HC (p<0.0001). Oral mucosa of HC were more highly colonized with Neisseria and Veillonella compared to all studied groups (p<0.0001).

Conclusions

Despite the uncertainty whether the reported differences in the oral mucosal microbial community of BS and RAS are of causative or reactive nature, it is envisaged that restoring the balance of the oral microbial community of the ulcer sites may be used in the future as a new treatment modality for oral ulceration.

The oral microbiota of patients with recurrent aphthous stomatitis

BACKGROUND

Specific pathogenic bacteria have been implicated in recurrent aphthous stomatitis (RAS), a chronic inflammatory condition characterised by ulcerations in the oral mucosa. However, the aetiology behind this condition still remains unclear.

OBJECTIVE

The buccal microbiota of patients with RAS was compared to that of control subjects to investigate its potential role for this condition.

DESIGN

Buccal swabs were obtained from non-ulcerative areas of 60 patients, of whom 42 patients had lesions at the time of sampling, and 60 healthy age- and gender-matched controls. Bacterial DNA was extracted and analysed by Terminal-Restriction Fragment Length Polymorphism, using enzymatic digestion of the polymerase chain reaction-amplified 16S rRNA gene, yielding a series of peaks, each representing a bacterial taxon.

RESULTS

Two peaks, 60 and 489, were more prevalent in patients with RAS than controls. Conversely, peaks 58 and 490 were less common in patients than controls. When the patients were divided into subgroups, we found that the observed differences in peak-pattern were related to the presence of lesions during sampling.

CONCLUSIONS

The microbiota of the non-inflamed buccal mucosa differed between patients and controls. The differences were most pronounced in patients who presented with lesions during sampling, suggesting that a disturbance in the normal buccal microbiota triggers the presence of lesions or that presence of lesions alters the microbiota.

Streptococcal taxonomy based on genome sequence analyses

The identification of the clinically relevant viridans streptococci group, at species level, is still problematic. The aim of this study was to extract taxonomic information from the complete genome sequences of 67 streptococci, comprising 19 species, by means of genomic analyses, multilocus sequence analysis (MLSA), average amino acid identity (AAI), genomic signatures, genome-to-genome distances (GGD) and codon usage bias. We then attempted to determine the usefulness of these genomic tools for species identification in streptococci. Our results showed that MLSA, AAI and GGD analyses are robust markers to identify streptococci at the species level, for instance, S. pneumoniae, S. mitis, and S. oralis. A Streptococcus species can be defined as a group of strains that share ≥ 95% DNA similarity in MLSA and AAI, and > 70% DNA identity in GGD. This approach allows an advanced understanding of bacterial diversity.

The possible role of HSPs on Behçet's disease: a bioinformatic approach

Current evidence lends increasing support to immunoinflammatory mechanisms as one of the prime pathogenic processes involved in the development and progression of Behçet's disease (BD). It has been observed that most human beings have cellular and humoral reactions against microbial heat shock proteins (HSPs). The observation that eukaryotic and prokaryotic HSPs have high sequence similarity promoted the hypothesis that HSPs might be potential candidates for molecular mimicry and could act as potentially dangerous autoantigens. In this study, using bioinformatics tools, we examined the hypothesis that HSPs (evolutionarily conserved proteins), which are present in pathogenic and commensal organisms and their hosts, provide the stimulus that initiates BD in susceptible individuals. In this regards, the nucleotide and amino acid sequences of the human HSP 60 kDa and bacterial HSP 60 kDa deposited in the NCBI and PDB databases were subjected to analysis using bioinformatics tools, including The CLC Sequence Viewer and MEGA softwares. These data showed that the sequence homology between bacterial and self HSPs (leading to cross-reactivity and molecular mimicry phenomenon) may be associated with the development of the disease; and suggesting that microbial HSPs, which cross-react with host tissues and elicit significant immune responses are possible pathogenetic agents involved in the development and progression of BD.

Mitis group streptococci express variable pilus islet 2 pili

Background

Streptococcus oralis, Streptococcus mitis, and Streptococcus sanguinis are members of the Mitis group of streptococci and agents of oral biofilm, dental plaque and infective endocarditis, disease processes that involve bacteria-bacteria and bacteria-host interactions. Their close relative, the human pathogen S. pneumoniae uses pilus-islet 2 (PI-2)-encoded pili to facilitate adhesion to eukaryotic cells.

Methodology/Principal Findings

PI-2 pilus-encoding genetic islets were identified in S. oralis, S. mitis, and S. sanguinis, but were absent from other isolates of these species. The PI-2 islets resembled the genetic organization of the PI-2 islet of S. pneumoniae, but differed in the genes encoding the structural pilus proteins PitA and PitB. Two and three variants of pitA (a pseudogene in S. pneumoniae) and pitB, respectively, were identified that showed ≈20% difference in nucleotide as well as corresponding protein sequence. Species-independent combinations of pitA and pitB variants indicated prior intra- and interspecies horizontal gene transfer events. Polyclonal antisera developed against PitA and PitB of S. oralis type strain ATCC35037 revealed that PI-2 pili in oral streptococci were composed of PitA and PitB. Electronmicrographs showed pilus structures radiating >700 nm from the bacterial surface in the wild type strain, but not in an isogenic PI-2 deletion mutant. Anti-PitB-antiserum only reacted with pili containing the same PitB variant, whereas anti-PitA antiserum was cross-reactive with the other PitA variant. Electronic multilocus sequence analysis revealed that all PI-2-encoding oral streptococci were closely-related and cluster with non-PI-2-encoding S. oralis strains.

Conclusions/Significance

This is the first identification of PI-2 pili in Mitis group oral streptococci. The findings provide a striking example of intra- and interspecies horizontal gene transfer. The PI-2 pilus diversity provides a possible key to link strain-specific bacterial interactions and/or tissue tropisms with pathogenic traits in the Mitis group streptococci.

[Ocular manifestations of Behçet's disease]

Eye involvement in Behçet's disease (BD) is frequent and an important cause of morbidity. The mean age at onset of uveitis is between 20 and 30 years in male and 30 years in female patients. Ocular involvement includes anterior, posterior or panuveitis. Uveitis may be the presenting manifestation of the disease in 20% of cases or may appear 2 or 3 years after the disease onset. The estimated risk of blindness at 5 years ranges from 15 to 25%. The main goals in the management of patients with BD uveitis are the rapid control of intraocular inflammation, the prevention of recurrent attacks, the achievement of complete remission, and preservation of vision. The medical treatment of patients with severe uveitis relies on the use of systemically administered drugs, including corticosteroids and cytotoxic agents. Anti-TNF agents and interferon-alpha seem to be efficient and well-tolerated alternative therapeutic options. Controlled clinical trials are mandatory to define the place of these new immunomodulatory agents in the therapeutic strategy, and especially their use as first-line therapy.

Raised concentration of soluble form of vascular endothelial cadherin and IL-23 in sera of patients with Behçet's disease

Behçet's disease (BD) is a chronic multisystem vasculitis disease that can affect any organ and usually is combined with hyperactivation of neutrophils. Involvement of inflammatory cytokines such as interleukin (IL)-12 in BD has been shown before. However, IL-12 shares a p40 subunit with IL-23, which has additional inflammatory effects apart of IL-12. IL-23 increases neutrophils' transmigration and therefore could contribute in BD induction or progression. Moreover, endothelial cells express vascular endothelial cadherin adhesion molecule (VE-cadherin), which plays critical roles in angiogenesis and endothelial integrity. VE-cadherin may shed into the circulation in a soluble form (sVE-cadherin), and inflammatory cytokines can increase this process. Therefore, a correlation between IL-23 concentration and amount of sVE-cadherin was proposed. We enrolled 44 healthy persons and 53 patients with BD of different disease activities and examined their serum concentrations of IL-23 and sVE-cadherin. A significant correlation was found between the concentrations of these two factors among patients only. Comparing sVE-cadherin mean concentration in patients and controls showed a significant difference, which for IL-23 was not considered significant. Results showed higher IL-23 in sera of patients with uveitis. Moreover, there was a meaningful correlation between IL-23 content and disease activity. These results could extend the biological effects of IL-23 in BD and introduce sVE-cadherin as a potential new biomarker in the course of BD pathogenesis.

Immobilization-based isolation of capsule-negative mutants of Streptococcus pneumoniae

The capsular polysaccharide (CPS) is the most important identified virulence factor of Streptococcus pneumoniae, a human pathogen of the upper respiratory tract. One limitation in studies of S. pneumoniae surface virulence factors is the lack of a reliable procedure for isolation of capsule-negative mutants of clinical strains. This paper presents an approach, based on the immobilization of pneumococci in semi-liquid (0.04 % agar) medium, to easily distinguish and select for non-capsulated mutants. A clinical S. pneumoniae type 37 strain was used as a model to show that CPS production results in bacterial immobilization in semi-liquid agar medium and restricts cell sedimentation. Descendants of CPS(-) mutants sedimented faster under these conditions and therefore could be separated from immobilized parental cells. The CPS(-) phenotype of the obtained mutants was confirmed by both immunoagglutination and immunostaining experiments using specific type 37 capsular antibodies. Complementation of immobilization with the cloned tts gene, encoding type 37 CPS synthase, confirmed that faster sedimentation of mutants was specifically due to loss of the capsule. DNA sequence determination of three independent mutants revealed a point mutation, a 46 nt deletion and a heptanucleotide duplication in the tts gene. Immobilization of strains producing other CPSs (type 2, 3 and 6) also resulted in the appearance of CPS(-) mutants, thus showing that immobilization-based isolation is not restricted to type 37 pneumococci. Bacterial growth in semi-liquid medium proved to be a useful model system to identify the genetic consequences of immobilization. The results indicate that immobilization due to CPS may impose selective pressure against capsule production and thus contribute to capsule plasticity.

Use of housekeeping gene sequencing for species identification of viridans streptococci

Based on the genetic analysis of 20 reference strains, we describe an approach using the sequencing of 2 housekeeping genes, zwf and gki, to identify members of the mitis-sanguinis group of viridans streptococci to the species level, with a better discrimination compared with 16S rDNA sequencing. This approach also suggested that some reference strains may not be correctly classified.

Pathogenesis of Adamantiades-Behçet's disease

The aetiology of Adamantiades-Behçet's disease remains unknown and its pathogenesis is not fully understood. Linked intrinsic and extrinsic factors are thought to contribute to the development of the disease, which probably occurs by environmental triggering of a genetically determined disorder. Transmission is solely vertical, indicating that the disease is not contagious. Genetic factors have been investigated and a significant link of HLA-B51, especially of HLA-B5101, has been identified. However, none of the functional correlates of the disease appear to be restricted by HLA-B51. Recently, the role of the genes encoding TNF, Tap proteins and MICA has been emphasised. Extrinsic pathogenetic candidates have been identified, including bacterial ( Streptococcus sanguis, Mycoplasma fermentas) and viral (human herpes virus) antigens and environmental pollution, which may cross-react with oral mucosal antigens and induce immunological mechanisms. A common factor linking some of the possible pathogenetic agents is extrinsically induced tissue stress or heat shock proteins, which react with host tissues and elicit significant Th1 cell responses. Neutrophils may also play a role in the pathogenesis of the disease, as they are attracted by macrophages and activated endothelial cells, which release cytokines and chemokines (especially IL-8) at the site of the lesions, and thus contribute to tissue damage and self maintenance of inflammation. Endothelial activation leading to a chronic local inflammation process together with platelet and serum factors enhance coagulation and thrombosis.

Reactive liposomes encapsulating a glucose oxidase-peroxidase system with antibacterial activity

Liposomes were prepared from phospholipid mixtures of dipalmitoylphosphatidylcholine (DPPC) and phosphatidylinositol (PI), encapsulating the enzymes glucose oxidase (GO) and GO in combination with horse radish peroxidase (HRP) by both extrusion (VET) and reverse-phase evaporation (REV). The optimum level of PI in DPPC/PI liposomes for targeting to biofilms of the oral bacterium Streptococcus gordonii has been established. The liposomes were characterised in terms of the content and activity of the encapsulated enzymes. The antibacterial activity of these 'reactive' liposomes arising from hydrogen peroxide and oxyacids in the presence of the substrates glucose and iodide ions, after targeting to the biofilms, were measured both as a function of liposome-biofilm incubation time and incubation time with the substrates. Bacterial inhibition increases with both liposome-biofilm and substrate-biofilm incubation time and with the extent of enzyme encapsulation. The reactive liposomes also display antibacterial activity in the presence of saliva. The reactive liposomes have potential value in the context of oral hygiene.