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Molecular Oral Microbiology

Victoria N Stone, Ping Xu
Even though the oral microbiome is one of the most complex sites on the body it is an excellent model for narrow-spectrum antimicrobial therapy. Current research indicates disruption of the microbiome leads to a dysbiotic environment allowing for the overgrowth of pathogenic species and the onset of oral diseases. The gram-negative colonizer, Porphyromonas gingivalis has long been considered a key player in the initiation of periodontitis and Streptococcus mutans has been linked to dental caries. With antibiotic research still on the decline, new strategies are greatly needed to combat infectious diseases...
June 13, 2017: Molecular Oral Microbiology
Mayilvahanan Shanmugam, Abimbola O Oyeniyi, Chaitra Parthiban, Satish Kumar Gujjarlapudi, Gerald B Pier, Narayanan Ramasubbu
Aggregatibacter actinomycetemcomitans, a Gram-negative bacterium, is the causative agent of localized aggressive periodontitis. Attachment to a biotic surface is a critical first step in the A. actinomycetemcomitans infection process for which exopolysaccharides have been shown to be essential. In addition, the pga operon, containing genes encoding for biosynthetic proteins for poly-N-acetyl glucosamine (PNAG), plays a key role in A. actinomycetemcomitans virulence, as a mutant strain lacking the pga operon induces significantly less bone resorption...
May 26, 2017: Molecular Oral Microbiology
Susan Mahabady, Natalia Tjokro, Shant Aharonian, Homayoun H Zadeh, Casey Chen, Hooman Allayee, Parish P Sedghizadeh
The periodontal pathogen Aggregatibacter actinomycetemcomitans is known to elicit systemic immune response in infected host, and occasionally causes non-oral infections. Detailed information on its immunopathological responses and the involvement of bacterial virulence factors remains to be elucidated. The aim of this study was to assess the systemic immune response to A. actinomycetemcomitans oral infection. We used an animal model that simulates systemic dissemination of the bacteria by injecting live wild type (WT) D7S-1 and double knockout mutant of leukotoxin and cytolethal distending toxin (ΔltxΔcdt) A...
May 22, 2017: Molecular Oral Microbiology
Lauren Mashburn-Warren, Jennifer S Downey, Steven D Goodman
Streptococcus mutans is recognized as one of the key contributors to the dysbiotic state that results in dental caries. While existing treatment strategies reduce the incidence of tooth decay, they also eliminate both the cariogenic and beneficial microbes. Here we introduce a novel treatment alternative using Sephadex, cross-linked dextranomer microspheres (DMs), typically used for gel filtration chromatography. In addition DM beads can be used for affinity purification of glucosyltransferases (GTFs) from S...
May 14, 2017: Molecular Oral Microbiology
Meng You, Yuki Chan, Donnabella C Lacap-Bugler, Yong-Biao Huo, Wenling Gao, W Keung Leung, Rory M Watt
Treponema denticola and other species (phylotypes) of oral spirochetes are widely-considered to play important etiological roles in periodontitis and other oral infections. The major surface protein (Msp) of T. denticola is directly implicated in several pathological mechanisms. Here, we have analyzed msp sequence diversity across 68 strains of oral phylogroup 1 and 2 treponemes; including reference strains of T. denticola, Treponema putidum, Treponema medium, 'Treponema vincentii', and 'Treponema sinensis'...
April 28, 2017: Molecular Oral Microbiology
Senthil Kumar Velusamy, Vandana Sampathkumar, Dipti Godboley, Daniel H Fine
Experiments were designed to explore a prominent autoinducer-2 (AI-2) producing gene (luxS) related to colonization and survival of Aggregatibacter actinomycetemcomitans, a low abundance member of the indigenous flora, that forms a key component of the dysbiotic flora in localized aggressive periodontitis. The luxS gene was disrupted in a primate strain of A. actinomycetemcomitans prior to implantation into the oral cavity of Rhesus monkeys (Rh). The colonization efficiency of the luxS mutant (RhAa-VS4) was compared to the parental wild-type strain (RhAa3) (positive control) and a ltxA mutant (RhAa-VS2) (negative control)...
April 6, 2017: Molecular Oral Microbiology
Susanne Bloch, Thomas Thurnheer, Yukitaka Murakami, Georgios N Belibasakis, Christina Schäffer
As a member of subgingival multispecies biofilms, Tannerella forsythia is commonly associated with periodontitis. The bacterium has a characteristic cell surface (S-) layer modified with a unique O-glycan. Both the S-layer and the O-glycan were analyzed in this study for their role in biofilm formation by employing an in vitro multispecies biofilm model mimicking the situation in the oral cavity. Different T. forsythia strains and mutants with characterized defects in cell surface composition were incorporated into the model, together with nine species of select oral bacteria...
April 5, 2017: Molecular Oral Microbiology
Livia A Alves, Erika N Harth-Chu, Thais H Palma, Rafael N Stipp, Flávia S Mariano, José F Höfling, Jacqueline Abranches, Renata O Mattos-Graner
Streptococcus mutans, a dental caries pathogen, can promote systemic infections upon reaching the bloodstream. The two-component system (TCS) VicRKSm of S. mutans regulates the synthesis of and interaction with sucrose-derived exopolysaccharides (EPS), processes associated with oral and systemic virulence. In this study, we investigated the mechanisms by which VicRKSm affects S. mutans susceptibility to blood-mediated immunity. Compared with parent strain UA159, the vicKSm isogenic mutant (UAvic) showed reduced susceptibility to deposition of C3b of complement, low binding to serum immunoglobulin G (IgG), and low frequency of C3b/IgG-mediated opsonophagocytosis by polymorphonuclear cells in a sucrose-independent way (P<...
April 5, 2017: Molecular Oral Microbiology
J Kreth, R A Giacaman, R Raghavan, J Merritt
The commensal oral microbial flora has evolved with the human host to support colonization of the various intraoral sites without triggering a significant immune response. In exchange, the commensal microbes provide critical protection against invading pathogens. The intrinsic ability of the oral flora to create a symbiotic microbial community with the host can be disturbed, selecting for the overgrowth of a dysbiotic community that can result in dental diseases, such as caries and periodontitis. Although the mechanisms of molecular pathogenesis in oral diseases are well characterized, much less is known about the molecular mechanisms used by the commensal flora to maintain oral health...
June 2017: Molecular Oral Microbiology
G Papadopoulos, Y B Shaik-Dasthagirisaheb, N Huang, G A Viglianti, A J Henderson, A Kantarci, F C Gibson
Macrophages adapt both phenotypically and functionally to the cytokine balance in host tissue microenvironments. Recent studies established that macrophages contribute an important yet poorly understood role in the development of infection-elicited oral bone loss. We hypothesized that macrophage adaptation to inflammatory signals encountered before pathogen interaction would significantly influence the subsequent immune response of these cells to the keystone oral pathobiont Porphyromonas gingivalis. Employing classically activated (M1) and alternatively activated (M2) murine bone-marrow-derived macrophage (BMDMø), we observed that immunologic activation of macrophages before P...
June 2017: Molecular Oral Microbiology
S S Chukkapalli, I M Velsko, M F Rivera-Kweh, H Larjava, A R Lucas, L Kesavalu
Toll-like-receptors (TLRs) play a significant role in the generation of a specific innate immune response against invading pathogens. TLR2 and TLR4 signaling contributes to infection-induced inflammation in periodontal disease (PD) and atherosclerosis. Observational studies point towards a relationship between PD and atherosclerosis, but the role of TLR2 and TLR4 in the recognition of multiple oral pathogens and their modulation of host response leading to atherosclerosis are not clear. We evaluated the role of TLR2 and TLR4 signaling in the induction of both PD and atherosclerosis in TLR2(-/-) and TLR4(-/-) mice to polymicrobial infection with periodontal pathogens Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Fusobacterium nucleatum...
June 2017: Molecular Oral Microbiology
A Itzek, Z Chen, J Merritt, J Kreth
Salivary agglutination is an important host defense mechanism to aggregate oral commensal bacteria as well as invading pathogens. Saliva flow and subsequent swallowing more easily clear aggregated bacteria compared with single cells. Phagocytic clearance of bacteria through polymorphonuclear neutrophil granulocytes also seems to increase to a certain extent with the size of bacterial aggregates. To determine a connection between salivary agglutination and the host innate immune response by phagocytosis, an in vitro agglutination assay was developed reproducing the average size of salivary bacterial aggregates...
June 2017: Molecular Oral Microbiology
O Chioma, A W Aruni, T-A Milford, H M Fletcher
To successfully colonize host cells, pathogenic bacteria must circumvent the host's structural barrier such as the collagen-rich extracellular matrix (ECM), as a preliminary step to invasion and colonization of the periodontal tissue. Filifactor alocis possesses a putative Peptidase U32 family protein (HMPREF0389_00504) with collagenase activity that may play a significant role in colonization of host tissue during periodontitis by breaking down collagen into peptides and disruption of the host cell. Domain architecture of the HMPREF0389_00504 protein predicted the presence of a characteristic PrtC-like collagenase domain, and a peptidase domain...
April 2017: Molecular Oral Microbiology
J L Baker, R C Faustoferri, R G Quivey
No abstract text is available yet for this article.
April 2017: Molecular Oral Microbiology
G Hajishengallis, J L Krauss, R Jotwani, J D Lambris
The complement system plays a central role in immunity and inflammation, although certain pathogens can exploit complement to undermine protective immunity. In this context, the periodontal keystone pathogen Porphyromonas gingivalis was previously shown by our group to evade killing by neutrophils or macrophages through exploitation of complement C5a receptor 1 (C5aR1) and complement receptor 3 (CR3). Here, we examined whether P. gingivalis uses complement receptors to also subvert killing by dendritic cells...
April 2017: Molecular Oral Microbiology
L C C Galvão, P L Rosalen, I Rivera-Ramos, G C N Franco, J K Kajfasz, J Abranches, B Bueno-Silva, H Koo, J A Lemos
In oral biofilms, the major environmental challenges encountered by Streptococcus mutans are acid and oxidative stresses. Previously, we showed that the transcriptional regulators SpxA1 and SpxA2 are involved in general stress survival of S. mutans with SpxA1 playing a primary role in activation of antioxidant and detoxification strategies whereas SpxA2 serves as a back up activator of oxidative stress genes. We have also found that spxA1 mutant strains (∆spxA1 and ∆spxA1∆spxA2) are outcompeted by peroxigenic oral streptococci in vitro and have impaired abilities to colonize the teeth of rats fed a highly cariogenic diet...
April 2017: Molecular Oral Microbiology
E Nagata, T Oho
Streptococcus mutans, the primary etiologic agent of dental caries, can gain access to the bloodstream and has been associated with cardiovascular disease. However, the roles of S. mutans in inflammation in cardiovascular disease remain unclear. The aim of this study was to examine cytokine production induced by S. mutans in human aortic endothelial cells (HAECs) and to evaluate the participation of toll-like receptors (TLRs) and cytoplasmic nucleotide-binding oligomerization domain (NOD) -like receptors in HAECs...
April 2017: Molecular Oral Microbiology
A Avilés-Reyes, J H Miller, J A Lemos, J Abranches
The ability of Streptococcus mutans to interact with collagen through the expression of collagen-binding proteins (CBPs) bestows this oral pathogen with an alternative to the sucrose-dependent mechanism of colonization classically attributed to caries development. Based on the abundance and distribution of collagen throughout the human body, stringent adherence to this molecule grants S. mutans with the opportunity to establish infection at different host sites. Surface proteins, such as SpaP, WapA, Cnm and Cbm, have been shown to bind collagen in vitro, and it has been suggested that these molecules play a role in colonization of oral and extra-oral tissues...
April 2017: Molecular Oral Microbiology
C J Rocco, M E Davey, L O Bakaletz, S D Goodman
Bacteria that persist in the oral cavity exist within complex biofilm communities. A hallmark of biofilms is the presence of an extracellular polymeric substance (EPS), which consists of polysaccharides, extracellular DNA (eDNA), and proteins, including the DNABII family of proteins. The removal of DNABII proteins from a biofilm results in the loss of structural integrity of the eDNA and the collapse of the biofilm structure. We examined the role of DNABII proteins in the biofilm structure of the periodontal pathogen Porphyromonas gingivalis and the oral commensal Streptococcus gordonii...
April 2017: Molecular Oral Microbiology
Z Chen, L Mashburn-Warren, J Merritt, M J Federle, J Kreth
The 5' untranslated region (5' UTR) of an mRNA molecule embeds important determinants that modify its stability and translation efficiency. In Streptococcus pyogenes, a strict human pathogen, a gene encoding a secreted protease (speB) has a large 5' UTR with unknown functions. Here we describe that a partial deletion of the speB 5' UTR caused a general accumulation of mRNA in the stationary phase, and that the mRNA accumulation was due to retarded mRNA degradation. The phenotype was observed in several M serotypes harboring the partial deletion of the speB 5' UTR...
March 30, 2017: Molecular Oral Microbiology
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