Journal of Oral Microbiology最新文献

Aim: This study aimed to explore the composition of the tooth-surface plaque (subgingival with marginal supragingival) microbiome in dentate older adults residing in long-term care (LTC) facilities, stratified by clinically assessed oral disease burden (ODB). A total of 196 LTC residents aged ≥62 years underwent oral examinations and microbial sampling from each dentate quadrant. Microbial profiling was performed using 16S rRNA gene sequencing.

Results: Participants were more frequently categorized into Moderate (n = 95, 48%) than Low (n = 32, 16%) or High (n = 69, 35%) ODB groups. Those with High ODB were oldest and had lowest number of remaining teeth. Alpha diversity did not differ between the ODB groups, whereas beta diversity analysis revealed significant differences between groups (Bray-Curtis: P = 0.005; weighted Unifrac: P = 0.025). The Low and Moderate ODB groups were enriched with both commensals and disease-associated genera, such as Ottowia, Lactococcus, Pseudoramibacter, and Anaeroglobus. High ODB group exhibited an increased abundance of genera linked to both oral and systemic diseases, including Cardiobacterium, Leptotrichia, Stomatobaculum, and Pseudopropionibacterium. Among ODB groups, periodontitis was a stronger determinant of oral microbiome composition than caries, whereas caries had a stronger effect on bacterial diversity.

Conclusion: These findings indicate a progressive shift toward a dysbiotic oral microbiome with increasing ODB.

Background: Porphyromonas gingivalis is a Gram-negative bacterium that plays a central role in the development of periodontal disease. It uses a type IX secretion system (T9SS) to export virulence factors to the bacterial surface where they are attached to A-LPS, one of the two forms of lipopolysaccharide (LPS) produced in P. gingivalis, and then packaged into outer membrane vesicles (OMVs). We previously showed that 1-P dephosphorylation of the lipid A component of LPS is regulated by the T9SS outer membrane protein PorV, and this is linked to membrane destabilisation and OMV blebbing/formation. Objective: This study aimed to investigate whether other T9SS outer membrane proteins are required for correct OMV biogenesis. Design: We examined gingipain activity, gingipain secretion, A-LPS production, OMV morphology, and lipid A structure in P. gingivalis W50, T9SS mutant strains, and a lipid A 1-phosphatase (ΔlpxE) mutant strain. Results: A functional T9SS is required for LpxE activity and correct vesicle formation, and this is likely through the function of an exported type IX-cargo protein. Conclusion: This study provides insight into a new mechanism that links type IX cargo sorting with OMV blebbing, which may also be present in other Bacteroidota that colonise the gut and oral cavity.

Background: Streptococcus suis is a zoonotic pathogen, and its colonization of the host tonsil is believed to be a vital source causing infection, while its mechanism competing for a stable tonsil niche is unknown. Rearrangement hotspot (Rhs) proteins are characterized to facilitate interbacterial competition by their polymorphic C-terminal toxins (CTs) in diverse bacteria, while their distant homologues emerged in S. suis, referred to as wall-associated protein A (WapA), has not been identified.

Methods: Bioinformatics, western blot and interbacterial competition analyses were performed to identify Rhs/WapA toxins and their roles during S. suis infection.

Results: The 350 kDa WapA-CT1, linked with a SecF-like protein and a SrtB sortase, was verified to manipulate the tonsil microbiota for S. suis optimal colonization. The unfolded WapA-CT1 was translocated across the cell membrane via the canonical Sec pathway. Afterward, autocleavage generated four fragments: the N-terminal NCWB fragment, two middle Rhs domains (Rhs1&2) that may fold as a β-barrel structure, and a C-terminal PreT-CT toxin domain. SrtB interacts with the NCWB region, and plays vital roles for the interbacterial antagonism mediated by the toxic CT1.

Conclusion: This discovery underscores the diversity of mechanisms by which pathogens delivering Rhs/WapA polymorphic toxins, and their roles in competing with the host microbiota.

Background: Chlorhexidine (CHX) is widely used in oral care for its broad-spectrum antimicrobial activity but can cause significant side effects. Sodium DNA has emerged as a potential adjunct capable of modulating cellular responses.

Aim: This study assessed whether sodium DNA enhances the antibacterial and antibiofilm activity of 0.20% and 0.12% CHX mouthwashes against Streptococcus mutans and Escherichia coli, and evaluated their effects on the viability and phagocytic activity of Dictyostelium discoideum, a model for mammalian phagocytes.

Results: All CHX-containing mouthwashes were bactericidal against S.mutans, regardless of sodium DNA, whereas CHX-only formulations were more effective against E.coli in time-kill assays. All formulations inhibited biofilm formation at 50-0.01%. In S. mutans, early biofilms were strongly inhibited (50-0.39%), whereas mature biofilms were less affected. In E. coli, sodium DNA enhanced inhibition of both biofilm formation (50-1.56%) and mature biofilms (50-3.12%). The 0.12% CHX-sodium DNA formulation most effectively modulated D.discoideum viability and phagocytic activity, and metabolomics showed that sodium DNA reduced CHX-induced metabolic stress.

Conclusions: This study integrates antimicrobial, antibiofilm, cellular, and metabolomic analyses to assess CHX with sodium DNA. Sodium DNA reduces CHX-induced cytotoxicity and metabolic stress while maintaining antimicrobial activity, offering insights for optimizing oral hygiene formulations through combined microbial and host-cell evaluation.

Background: The oral cavity is an important yet understudied reservoir of antimicrobial resistance genes (ARGs), potentially shaped by geographic variation in antibiotic usage.

Objective: To compare the oral resistomes of healthy adults from Thailand and Norway, two countries with contrasting antimicrobial use practices, using shotgun metagenomic sequencing.

Design: Stimulated saliva samples were collected from healthy adults in Thailand (n = 43) and Norway (n = 50). ARGs were identified with AMRPlusPlus against the MEGARes database, and microbial taxonomy was profiled with KrakenUniq. Diversity metrics, ordination, and clustering analyses assessed resistome and microbiome structures.

Results: Thai samples exhibited significantly greater ARG richness, evenness, and diversity (p < 0.001), driven by higher abundances of multi-biocide, nucleoside, and copper resistance genes. Norwegian samples were enriched in aminoglycoside, sulfonamide, and quaternary ammonium compound resistance genes. Both cohorts shared core oral genera, but Thai samples showed greater taxonomic richness without differences in overall microbiome diversity. Non-metric multidimensional scaling and PERMANOVA revealed stronger geographic separation for resistomes (R² = 0.639) than microbiomes (R² = 0.382). Co-occurrence networks highlighted structured associations between ARG groups and bacterial genera, suggesting ecological influences beyond taxonomic composition.

Conclusions: These results reveal distinct geographic signatures in the oral resistome that are not fully explained by microbiome structure, reflecting the influence of local ecological and societal factors, including antimicrobial exposure. The findings highlight the oral cavity as a dynamic ARG reservoir and support its inclusion in regional antimicrobial resistance surveillance to inform public health strategies.

Background: The pathogenesis of oral squamous cell carcinoma (OSCC) in never-smoking females remains poorly understood, as these patients lack traditional risk factors. This subgroup accounts for an increasing proportion of OSCC cases and may exhibit distinct tumor biology. Here, we investigated the association between the alterations in the salivary microbiome and OSCC in never-smoking female patients.

Materials and methods: Saliva samples from 72 never-smoking female patients with OSCC and 494 never-smoking healthy female controls were analyzed using 16S rRNA gene sequencing. Microbial community structure and function were compared using statistical analyses, machine learning algorithms, and pathway prediction with PICRUSt2.

Results: Patients with OSCC exhibited significantly different microbial diversity and composition compared to controls. The genera Rhodococcus, Slackia, Lactobacillus, and Enterobacterales_g were enriched in the OSCC group, whereas Corynebacterium was more abundant in the Control group. These taxa were associated with oncogenic pathways, including PI3K-Akt signaling and nicotinate/nicotinamide metabolism. Functional inference also indicated enrichment of cancer-related orthologs such as LKB1, NFKB1, ITGAV, and TRAF4.

Conclusions: Salivary microbiome alterations, both taxonomic and functional, are associated with OSCC in never-smoking females. These findings suggest a potential microbial contribution to carcinogenesis in this unique patient population and offer novel insights into disease mechanisms.

Background: Molecular identification of dental caries microbes is advancing rapidly, yet sampling methods remain outdated and imprecise.

Objective: To refine microbe sample harvesting and preserve taxa pre-harvest spatial positions relative to lesion pulpal depth.

Methods: Refinements included a sterile zone surrounding the dissection site and emphasize asepsis, surgical microscope magnification and lighting, and micro-surgical techniques. Retention of taxa pre-harvest spatial positions relative to lesion pulpal depth used shallow-layered dissection (mean 6 mg/layer, SD 2.65 mg), where each layer became a separate sample for molecular identification before sequential reassembly in a layered lesion diagram. To evaluate the method's robustness, 14 lesions varying in severity and type from private dental practices were dissected using the method (7 pit and fissure and 7 facial lesions; 4 untreated, 3 treated).

Results: Pre-harvest taxa detail, not possible previously, showed taxa location, abundance and diversity relative to lesion pulpal depth, as well as absolute abundance per milligram and taxa transitions and fluctuations from superficial through the deepest dissected layers. The method provides these data regardless of lesion type, stage, or complexity, whether untreated or treated.

Conclusions: This method provides new details and perspectives on dental caries taxa that could help develop diagnostic instruments and treatments to halt dental caries progression.

Background: Tonsillar hypertrophy (TH) and adenotonsillar hypertrophy (ATH) are primary risk factors for paediatric obstructive sleep apnoea (OSA), but their salivary microbiota differ.

Objective: This study aimed to investigate whether the tonsillar surface and core microbiota resemble the salivary microbiota, and whether these microbial profiles are influenced by adenoid hypertrophy and related clinical factors.

Design: Forty-nine children undergoing tonsillectomy were enrolled, including 21 children with TH and 28 with ATH. Saliva and tonsillar surface swabs were collected preoperatively, and core tissues were obtained intraoperatively. Microbiota were profiled via 16S rRNA sequencing, compared across sites and groups, and correlated with preoperative clinical indicators.

Results: The tonsillar core microbiota was relatively stable across all children, whereas the surface and salivary microbiota shifted with adenoid hypertrophy. Prevotella, Neisseria, Veillonella, Alloprevotella, Lancefieldella and Haemophilus were consistently more abundant on the tonsillar surface compared to the core. Gemella was uniquely enriched on the surface and positively correlated with the obstructive apnoea-hypopnoea index and red cell distribution width in the TH group.

Conclusions: This study reveals distinct microbial profiles between the tonsillar surface and core. In TH, surface microbiota was associated with OSA severity and haematological indicators, suggesting potential relevance that warrants further investigation.

Background: Smoking increases mortality risk and alters the oral microbiome, but its mediating role in the smoking-survival relationship remains unclear. This study examined whether oral microbiome diversity mediates the association between smoking and all-cause mortality.

Methods: We included 8,223 participants from the National Health and Nutrition Examination Survey with linked mortality data through 2019. Oral microbiome diversity was assessed using alpha and beta diversity metrics. Associations between smoking, diversity, and mortality were assessed using Weibull Accelerated Failure Time models. Multivariable linear regression evaluated the relationship between smoking and oral microbiome diversity. Mediation analysis estimated the Natural Direct Effect (NDE) and Natural Indirect Effect (NIE). Sensitivity analyses assessed effect heterogeneity.

Results: Among participants, 429 were deceased. Current smoking was associated with a 42.3% shorter survival time (TR = 0.577). Greater ln-transformed observed Operational Taxonomic Units (OTU) richness was associated with 33.2% longer survival time (TR = 1.332). Smoking was associated with survival time through NIE = 1.013 (95% CI: 1.003, 1.033) and NDE = 0.577 (95% CI: 0.474, 0.697). Sensitivity analyses supported the findings.

Discussion: Oral microbiome diversity partially mediated the association between smoking and mortality. Although smoking shortened survival, its effect on increasing OTU richness modestly suppressed this risk. These results highlight a complex microbial pathway and support further investigation into species-level mechanisms and potential microbiome-targeted interventions.

Background: Porphyromonas gingivalis, a key pathogen in chronic periodontitis, produces heterogeneous lipopolysaccharides (LPS) that are weakly recognized by Toll-like receptor 4 (TLR4). Human cells detect cytosolic LPS via caspase-4 (CASP4); however, whether P. gingivalis LPS (PgLPS) can directly activate CASP4 remains unclear. This study aimed to investigate the CASP4-activating properties of purified PgLPS.

Methods: Standard-grade (ST) and ultrapure-grade (UP) purified PgLPS were tested for CASP4 activation using recombinant CASP4 in fluorogenic and IL-18 assays. PgLPS-CASP4 interactions were examined by pull-down. In HSC-2 cells, IL-18 maturation, gasdermin D cleavage, pyroptosis, and dependence on CASP4 or TLR4 were assessed after cytosolic LPS delivery. Guanylate-binding protein-1 (GBP1) involvement was evaluated by siRNA knockdown. Effects of outer membrane vesicles (OMVs) were also tested.

Results: ST-PgLPS directly activated recombinant CASP4, while UP-PgLPS did not. Intracellular delivery of ST-PgLPS induced weak pyroptosis, while UP-PgLPS had no effect. Responses were abrogated by CASP4 inhibition but not by TLR4 inhibition. IFN-γ priming enhanced responses: ST-PgLPS induced moderate activation, whereas UP-PgLPS triggered robust, GBP1-dependent activation. OMVs activated CASP4 in IFN-γ-primed cells.

Conclusion: CASP4 activation depends on PgLPS purity and host cell priming. GBP1 contributes to PgLPS sensing, and OMVs serve as vehicles for PgLPS delivery to the cytosol.