Journal of Oral Microbiology最新文献

Objective: Mitis group streptococci (MGS) are the predominant oral bacteria that cause bacteremia and infective endocarditis. Although membrane vesicle (MV) secretion has been reported in Streptococcus pneumoniae among MGSs, comprehensive studies using various streptococcal species are limited. We aimed to determine whether MGS species produce MVs and to examine their biological functions.

Materials and methods: MVs were isolated from MGS cultures using density gradient ultracentrifugation. The particle sizes of MVs were measured, and proteins in MVs were identified by liquid-chromatography tandem mass spectrometry analysis. Effects of MVs on host cells and oral pathogenic bacteria were investigated.

Results: MV production was confirmed in Streptococcus mitis strains NCTC12261, Nm-65, and Nm-76, with particle diameters ranging from 100 to 120 nm. The MVs contained numerous cytoplasmic proteins. The MVs showed internalization into alveolar epithelial cells and induced the production of multiple cytokines, including TNF-α, IL-8, IL-6, IL-1β, and IL-10, in macrophages while suppressing phagocytic activity. In neutrophil-differentiated cells, MVs induced IL-8 but not TNF-α production. MVs from S. pneumoniae TIGR4 and S. mitis Nm-65 inhibited biofilm formation of Aggregatibacter actinomycetemcomitans.

Conclusions: MVs play crucial roles in MGS survival strategies through immune modulation and interspecies competition, contributing to their pathogenicity and host-pathogen interactions.

Objective: To explore the plaque biofilm microbiome associated with severe dental fluorosis (SF), and to describe its metagenome and metabolome.

Methods: Sixteen plaque biofilm samples were collected from eight 6- to 15-year-old Thai children with SF and eight age-matched, caries-free and controls. Biofilms were analyzed using shotgun metagenomic sequencing, followed by bioinformatics evaluation.

Results: Taxonomic profiling of biofilms from SF and controls identified a total of 12 phyla and 354 species. While alpha diversity was similar between the groups, beta diversity analysis (P = 0.0010) indicated distinct microbial community structures. LEfSe highlighted key discriminatory taxa: five health-associated species (Actinomyces dentalis, Tannerella sp. HOT 286, Candidatus Nanosynbacter sp, Selenomonas noxia and Treponema sp OMZ 804 ) were enriched in controls, while Neisseria sicca, known for fluoride-sensitive esterase production, was significantly elevated in SF. Functionally, eight metabolic pathways were altered; three of these (phosphatidylcholine acyl editing, anhydromuropeptides recycling II, ubiquinol-7 biosynthesis), hypothesized to support N. sicca activity, were upregulated in the SF group.

Conclusion: SF is associated with a significant shift in the biofilm microbiota, characterized by enrichment of N. sicca and a reduction in health-associated taxa. Altered metabolic pathways supporting N. sicca provide mechanistic insights into its role as a candidate biomarker for fluorosis, warranting further investigation.

Background: While the microbiome of caries-derived periapical lesions has been extensively characterized, the microbial profile of trauma-derived periapical lesions remains poorly understood. This study aimed to characterize the apical microbiome of trauma-derived periapical lesions and identify taxonomic differences between trauma- and caries-derived periapical lesions.

Methods: Twenty patients with periapical lesions were enrolled, comprising 10 trauma-derived cases (trauma group) and 10 caries-derived cases (caries group). Microbial samples were collected using sterile paper points inserted into the root canal exudate, followed by DNA extraction and Illumina sequencing of the hypervariable V3-V4 regions of the 16S rRNA gene. Bioinformatic analyses included α-diversity, β-diversity based on Bray-Curtis distance and differential abundance testing (LEfSe method with LDA score ≥ 2.0).

Results: Sequencing revealed 36 bacterial phyla and 587 genera across all samples. Trauma group showed significantly greater relative abundance of Campylobacter (P = 0.002) compared to caries group, whereas Prevotella (P = 0.008), Vibrio (P = 0.041) and Filifactor (P = 0.006) exhibited reduced abundance. The core microbiota in the trauma group included Phocaeicola, Porphyromonas and Pyramidobacter, based on relative abundance. LEfSe analysis identified Campylobacter as a biomarker for the trauma group.

Conclusions: Trauma-derived periapical lesions exhibited reduced microbial diversity compared to caries-derived periapical lesions, with Campylobacter identified as a potential pathognomonic taxon for trauma-derived periapical lesions.

Background: C andida albicans is the predominant opportunistic pathogen causing oral candidiasis in immunocompromised head and neck cancer (HNC) patients. Fluconazole (FLC) is commonly used for treatment and prophylaxis; however, persistent infections remain a clinical challenge during cancer therapy. We hypothesized that C. albicans survival under FLC exposure may be driven by the development of tolerance or resistance, accompanied by altered virulence traits.

Methods: In this study, we characterized FLC susceptibility and virulence profiles of clinical C. albicans isolates obtained from HNC patients.

Results: Most isolates were susceptible to FLC, but two tolerant phenotypes, moderate (MT) and heavy tolerance (HT), were identified. FLC prophylaxis did not significantly affect tolerance prevalence or severity. Both tolerant isolates exhibited upregulation of key resistance genes, ERG11. Under FLC exposure, the MT isolate modestly increased expression of ALS1 and SAP6, while downregulating other virulence genes, correlating with reduced adhesion and biofilm formation. Conversely, the HT isolate upregulated ALS3, HWP1, and SAP6, enhancing adhesion and sustaining biofilm integrity. Despite SAP6 upregulation in both, host cell cytotoxicity was similar.

Conclusion: These findings highlight adaptive mechanisms by which FLC-tolerant C. albicans retain pathogenicity under antifungal stress, posing potential challenges for clinical management in HNC patients.

Background: The kynurenine (KYN) pathway produces key metabolites for immunoregulation and neuromodulation in humans, but its presence and activity in the oral microbiome are unclear. This study investigates the functionality of the key kynureninase (KynU), which catalyses kynurenine to anthranilic acid (AA), in oral bacteria.

Methods: Bioinformatic analysis identified putative kynU genes in oral bacterial genomes, and structural similarity of the predicted proteins was evaluated using Template Modeling (TM)-score and Root Mean Square Deviation (RMSD) analyses. Selected kynU sequences were cloned into the pBAD-His A expression vector. Enzymatic activity was accessed by quantifying AA concentrations using liquid chromatography-mass spectrometry (LC-MS).

Results: Among 71 species, seven oral bacteria were identified to possess the kynU. Structural analyses indicated KynU from four species may fold into functional enzymes. Three recombinant KynU from Burkholderia cepacia, Ralstonia pickettii, and Stenotrophomonas maltophilia produced detectable levels of AA (21.27 ± 12.0 µM, 19.59 ± 8.6 µM, and 46.43 ± 36.8 µM, respectively), confirming functional KYN-to-AA conversion.

Conclusions: This study demonstrates KynU activity in oral bacteria, revealing an unrecognised aspect of microbial metabolism with potential implications for host-microbe interactions. Further investigation is required to elucidate the biological significance of bacterial KYN metabolites and their role in oral diseases.

Background: Oral squamous cell carcinoma (OSCC) often recurs locally, reducing survival. The oral microbiome may influence tumor recurrence, but its prognostic role is unclear. This study investigated oral microbiomes associated with OSCC recurrence and their prognostic merit.

Materials and methods: Saliva samples were collected from 133 patients with OSCC. 16S rRNA gene sequencing was performed, and microbial signatures were predicted via XGBoost. Functional metagenomic prediction was conducted using PICRUSt2.

Results: XGBoost identified Eubacterium, Lactobacillus, Kingella, Paludibacter, Parvimonas, Staphylococcus, and Veillonella as predictive for OSCC recurrence. Eubacterium and Lactobacillus were significantly enriched in recurrent disease and associated with poor survival. Staphylococcus and Veillonella were abundant in non-recurrent disease, correlating with a favorable prognosis. The microbiome-based model achieved superior predictive performance (AUC = 0.741) compared with the clinical N-stage model (AUC = 0.66). Eubacterium and Lactobacillus showed positive correlations with key genes, such as protein kinase B (AKT), fibroblast growth factor receptor 1 and guanine nucleotide-binding protein G subunit beta-2, within the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway. In contrast, Veillonella was negatively correlated with these genes.

Conclusions: Oral saliva microbiome profiling reveals distinct microbial patterns associated with OSCC recurrence. Our correlation-based functional predictions indicated that the enrichment of Eubacterium and Lactobacillus along with a lower abundance of Veillonella may influence recurrence through oncogenic PI3K/AKT/mTOR, underscoring the prognostic potential of saliva-based microbial biomarkers.

Backgroud: Hypochlorous acid solution (HAS), a novel bio-friendly antimicrobial, has garnered attention for its antimicrobial activity, while less is known about its antibiofilm effects on periodontal pathogenic biofilms and the underlying mechanisms.

Objective: This study aimed to explore HAS's antibiofilm effect on periodontal pathogenic biofilms and the potential mechanisms.

Design: In vitro, the minimum inhibitory concentration (MIC) of HAS was determined by microdilution method. Alterations in biofilms were analysed using crystal violet (CV) staining, MTT assay and microscopic imaging techniques. The biocompatibility of HAS was assessed via CCK-8 and scratch assays. The regulatory mechanism of HAS within biofilms were investigated using bioluminescence assays, reactive oxygen species (ROS) detection and RT‒qPCR. In vivo, rat periodontitis models were established. Imaging and histological techniques were employed to evaluate the inhibitory effects of HAS on alveolar bone resorption and inflammatory cytokines.

Results: Compared to 0.25% NaClO solution, it exhibited better biocompatibility. HAS downregulated biofilmvirulence factors and upregulated oxidative stress response-related genes, suggesting that inducing ROS production is a crucial mechanism of HAS in biofilm inhibition. Furthermore, HAS significantly inhibited autoinducer-2 (AI-2) activity and downregulated the QS-related genes. In vivo, HAS significantly reduced bone resorption and periodontal inflammation.

Conclusions: Given HAS's accessibility, excellent biocompatibility, and outstanding antibiofilm properties, it may offer a safe antibiofilm approach for clinical periodontal therapy, effectively removing biofilms in areas inaccessible to instrumental therapy and persistent biofilms.

Background: The neonatal period is critical for oral microbiome establishment, but temporal patterns in preterm newborns remain unclear. This study examined longitudinal microbiome changes in full-term and preterm newborns and assessed perinatal and clinical influences.

Methods: Oral swabs were collected from 98 newborns (23 full-term, 75 preterm). Samples were obtained at birth and Day 2 for full-term, and at birth, Day 7, and Day 28 for preterm newborns. 16S rRNA gene sequencing was used to analyze microbial diversity, taxonomic shifts, and virulence-related genes.

Results: Preterm newborns showed persistently lower α-diversity and delayed succession compared with full-term newborns. Full-term infants transitioned rapidly from Proteobacteria-dominant to Firmicutes- and Actinobacteria-rich communities, while preterm infants maintained Proteobacteria longer. Diversity in preterm newborns was significantly affected by gestational age, birthweight, delivery mode, feeding type, and β-lactam exposure. Breastfeeding supported more stable diversity, whereas cesarean delivery and formula feeding reduced diversity. Functional profiling revealed greater abundance of virulence-associated genes in preterm newborns, suggesting differences in early host-microbe interactions. .

Conclusions: Preterm newborns exhibit delayed oral microbiome development, influenced by multiple modifiable factors. Supportive strategies, such as breastfeeding and prudent antibiotic use, may help foster microbial stability and potentially reduce infection risk in this vulnerable population.

Objectives: This study aims to explore the mechanisms of the detrimental effects of postmenopausal osteoporosis (PMO) on periodontitis.

Methods: An ovariectomized (OVX) rat model was established to investigate the effects of PMO on alveolar bone homeostasis and periodontal inflammation. Chlorhexidine digluconate (CHX) was administered to rats with OVX - periodontitis to ascertain the involvement of the oral microbiota in the influence of PMO on periodontitis. Finally, oral microbiota transplantation was conducted to examine the oral microbiota's pathogenicity.

Results: OVX rats exhibited increased periodontal trabecular bone resorption and inflammation. In addition, depletion of the oral microbiota by CHX decreased the alveolar bone destruction in OVX - periodontitis rats. Furthermore, 16S rRNA gene sequencing demonstrated that PMO changes the composition of the oral microbiota. Finally, oral microbiota transplantation indicated that PMO enhanced the oral microbiota's pathogenicity.

Conclusion: PMO detrimentally affects periodontitis by increasing periodontal inflammation and the pathogenicity of the oral microbiota, which provides a mechanistic understanding of how PMO affects periodontitis and highlights the necessity of more regular monitoring of the oral microbiota in PMO patients.

Background: Behçet's Disease (BD), a complex autoinflammatory disorder, is increasingly linked to microbial dysbiosis, yet the specific microbial signatures and their functional consequences remain incompletely characterized. Elucidating these alterations is crucial for understanding BD pathogenesis.

Objective: To identify distinct microbial community structures and functional potentials in supragingival plaque microbiomes of BD patients versus healthy controls (HC) using high-resolution shotgun metagenomic sequencing.

Methods: Supragingival plaque from 18 BD patients and 22 HCs was subjected to shotgun metagenomics. Analyses included alpha/beta diversity, taxonomic composition, and MetaCyc pathway abundance, with statistical comparisons.

Results: Despite similar age and clinical attachment levels, BD patients exhibited significantly increased alpha diversity and distinct beta diversity compared to HCs. Differential abundance analysis revealed an enrichment of anaerobic and opportunistic taxa in BD (implicating 4 phyla and 28 genera), alongside 19 significantly altered MetaCyc pathways, indicating substantial functional reprogramming within the BD oral microbiome.

Conclusion: This high-resolution metagenomic analysis reveals profound oral microbiome dysbiosis in Behçet's Disease, characterized by altered diversity, a distinct taxonomic signature enriched with pathobionts, and significant functional shifts. These comprehensive microbial alterations are implicated in contributing to the local and systemic inflammatory processes driving BD pathogenesis, offering potential avenues for diagnostic biomarkers and targeted therapies.