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Molecular Oral Microbiology

Keumjin Baek, Youngnim Choi
Oral lichen planus (OLP) is a variant of LP, a common chronic mucocutaneous inflammatory disease. While cutaneous lesions of LP are self-limiting, OLP lesions are non-remissive, alternating periods of exacerbation and quiescence, and only symptomatic treatments exist for OLP. The precise etiology and pathogenesis of OLP are hardly understood, which is a major obstacle to the development of new therapeutics for this disease. OLP is considered a T cell-mediated inflammatory disease. Although various antigens have been considered, what actually triggers the inflammatory response of T cells is unknown...
September 4, 2017: Molecular Oral Microbiology
Liang Song, Guangyu Dong, Lijia Guo, Dana T Graves
Dendritic cells (DCs) are antigen-presenting cells that capture, process and present antigens to lymphocytes to initiate and regulate the adaptive immune response. DCs detect bacteria in skin and mucosa and migrate into regional lymph nodes, where they stimulate antigen-specific T and B lymphocyte activation and proliferation. DCs direct CD4 T cells to differentiate to T cell subsets such as Th1, Th2, Th17 and Treg cells. The periodontium is chronically exposed to oral bacteria that stimulate an inflammatory response to induce gingivitis or periodontitis...
August 28, 2017: Molecular Oral Microbiology
Hidenobu Senpuku, Hideo Yonezawa, Saori Yoneda, Itaru Suzuki, Ryo Nagasawa, Naoki Narisawa
The oral bacterium Streptococcus mutans is the principal agent in the development of dental caries. Biofilm formation by S. mutans requires bacterial attachment, aggregation and glucan formation on the tooth surface under sucrose supplementation conditions. Our previous microarray analysis of clinical strains identified 74 genes in S. mutans that were related to biofilm morphology; however, the roles of almost all these genes in biofilm formation are poorly understood. We investigated the effects of 21 genes randomly selected from our previous study regarding S...
August 28, 2017: Molecular Oral Microbiology
Yingying Wu, Caroline Westwater, E Xiao, Jôice Dias Corrêa, Wenmei Xiao, Dana T Graves
The acquisition of the oral microbiome is a complex process. We examined how the timing of microbial exposure alters bacterial colonization of the tooth surface. Germ-free mice were conventionalized by exposure to specific pathogen free (SPF) mice to acquire a commensal microbiome over three distinct four week periods, 0-4 weeks of age (Conv0-4w), 4-8 weeks (Conv4-8w), or 8-12 weeks (Conv8-12w). Bacterial DNA was extracted from the tooth surface and analyzed by 16S rDNA sequencing. Total bacteria and inflammatory cytokine expression in gingiva were determined by quantitative real-time PCR...
August 4, 2017: Molecular Oral Microbiology
Sumei Liao, Arpan De, Tatyana Thompson, Lynne Chapman, Jacob P Bitoun, Xin Yao, Qingzhao Yu, Fangrui Ma, Zezhang T Wen
Our previous studies showed that brpA in S. mutans, which encodes a member of the LytR-CpsA-Psr family of proteins, can be cotranscribed with brpB upstream as a bicistronic operon, while the intergenic region also has strong promoter activity. To elucidate how brpA expression is regulated, the promoter regions were analyzed using PCR-based deletions and site-directed mutagenesis and a promoterless luciferase gene as a reporter. Allelic exchange mutagenesis was also used to examine genes encoding putative trans-acting factors, and the impact of such mutations on brpA expression was analyzed by reporter assays...
July 26, 2017: Molecular Oral Microbiology
Izabela Sitkiewicz
Streptococci are a diverse group of gram positive microorganisms sharing common virulence traits and similar strategies to escape the oral niche and establish an infection in other parts of the host organism. Invasive infection with oral streptococci is "a perfect storm" that requires the concerted action of multiple biotic and abiotic factors. Our understanding of streptococcal pathogenicity and infectivity should probably be less mechanistic and driven not only by the identification of novel virulence factors...
July 20, 2017: Molecular Oral Microbiology
Joe Adserias Garriga, Narciso M Quijada, Marta Hernandez, David Rodríguez Lázaro, Dawnie Steadman, Jesús Garcia-Gil
Oral cavity harbors one of the most diverse microbiomes in the human body. It has been shown to be the second most complex in the body after the gastro- intestinal tract. Upon death, the indigenous microorganisms lead the decomposition of the carcass. Therefore, oral cavity and gastro-intestinal tract microbiomes, play a key role in human decomposition. The aim of the present study is to monitor the microbiome of decaying bodies on a daily basis and to identify signature bacterial taxa, that can improve postmortem interval estimation...
June 27, 2017: Molecular Oral Microbiology
Senthil K 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 before implantation into the oral cavity of Rhesus monkeys (Rh). The colonization efficiency of the luxS mutant (RhAa-VS4) was compared with the parental wild-type strain (RhAa3) (positive control) and a ltxA mutant (RhAa-VS2) (negative control)...
October 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<...
October 2017: Molecular Oral Microbiology
M M Jones, S T Vanyo, M B Visser
Treponema denticola is an oral spirochete strongly associated with severe periodontal disease. A prominent virulence factor, the major outer sheath protein (Msp), disorients neutrophil chemotaxis by altering the cellular phosphoinositide balance, leading to impairment of downstream chemotactic events including actin rearrangement, Rac1 activation, and Akt activation in response to chemoattractant stimulation. The specific regions of Msp responsible for interactions with neutrophils remain unknown. In this study, we investigated the inhibitory effect of truncated Msp regions on neutrophil chemotaxis and associated signaling pathways...
October 2017: Molecular Oral Microbiology
Lihong Guo, Bhumika Shokeen, Xuesong He, Wenyuan Shi, Renate Lux
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...
October 2017: Molecular Oral Microbiology
(no author information available yet)
No abstract text is available yet for this article.
August 2017: Molecular Oral Microbiology
J B Kaplan, V Sampathkumar, M Bendaoud, A K Giannakakis, E T Lally, N V Balashova
The Gram-negative bacterium Kingella kingae is part of the normal oropharyngeal mucosal flora of children <4 years old. K. kingae can enter the submucosa and cause infections of the skeletal system in children, including septic arthritis and osteomyelitis. The organism is also associated with infective endocarditis in children and adults. Although biofilm formation has been coupled with pharyngeal colonization, osteoarticular infections, and infective endocarditis, no studies have investigated biofilm formation in K...
August 2017: Molecular Oral Microbiology
C Liu, D P Miller, Y Wang, M Merchant, R J Lamont
The development of synergistically pathogenic communities of Porphyromonas gingivalis and Streptococcus gordonii is controlled by a tyrosine-phosphorylation-dependent signaling pathway in P. gingivalis. The Ptk1 bacterial tyrosine (BY) kinase of P. gingivalis is required for maximal community development and for the production of extracellular polysaccharide. We show that the consensus BY kinase Walker A and B domains, the RK cluster, and the YC domain of Ptk1 are necessary for autophosphorylation and for substrate phosphorylation...
August 2017: Molecular Oral Microbiology
M Doke, H Fukamachi, H Morisaki, T Arimoto, H Kataoka, H Kuwata
Periodontitis is an inflammatory disease caused by periodontal bacteria in subgingival plaque. These bacteria are able to colonize the periodontal region by evading the host immune response. Neutrophils, the host's first line of defense against infection, use various strategies to kill invading pathogens, including neutrophil extracellular traps (NETs). These are extracellular net-like fibers comprising DNA and antimicrobial components such as histones, LL-37, defensins, myeloperoxidase, and neutrophil elastase from neutrophils that disarm and kill bacteria extracellularly...
August 2017: Molecular Oral Microbiology
M Varanat, E M Haase, J G Kay, F A Scannapieco
Periodontitis is a highly prevalent disease caused in part by an aberrant host response to the oral multi-species biofilm. A balance between the oral bacteria and host immunity is essential for oral health. Imbalances in the oral microbiome lead to an uncontrolled host inflammatory response and subsequent periodontal disease (i.e. gingivitis and periodontitis). TREM-1 is a signaling receptor present on myeloid cells capable of acting synergistically with other pattern recognition receptors leading to amplification of inflammatory responses...
August 2017: 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
J London, D Lunsford, R J Palmer
No abstract text is available yet for this article.
June 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
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