Journal of Oral Microbiology最新文献

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.

Background: Low-abundance bacterial (LAB) species, despite their low prevalence, may contribute to oral inflammatory diseases by triggering host immune responses. The NLRP3 inflammasome plays a key role in inflammation, but its activation by LAB species remains unclear.

Aim: This study examined whether selected LAB species and their biofilm-secreted components induce cytokine production and inflammasome activation in human peripheral blood mononuclear cells (PBMCs).

Methods: Biofilms of selected LAB species were established, and supernatants were collected. PBMCs were stimulated with biofilms or supernatants, and cytokine levels were quantified using ELISA. The expression of NLRP3 and Caspase-1 genes was analyzed through real-time PCR.

Results: Biofilms induced significantly higher levels of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β, and IL-18) compared to supernatants, with C. hominis, N. flavescens, and D. pneumosintes being the most potent inducers. Biofilms also led to a marked increase in NLRP3 expression, while supernatants primarily activated Caspase-1 expression, indicating distinct inflammasome activation pathways.

Conclusions: These findings highlight the immunostimulatory potential of LAB species, particularly their ability to activate NLRP3 and drive inflammation. The differential activation of NLRP3/Caspase-1 by biofilms and supernatants suggests distinct pathogenic mechanisms. Targeting such mechanisms/pathways could offer new therapeutic strategies to mitigate inflammation linked to oral infections.

Objective: In periodontal research, subgingival biofilm samples are typically collected using sterile paper points and pooled for molecular analyses. Streamlining this process by using a single paper point for molecular analysis could simplify sample collection and allow additional paper points to be used for other investigations. This pilot study evaluated the performance of three commercial DNA extraction kits for analysing small sample volumes (<10 µL).

Methods: Samples were collected from six participants, each contributing 18 paper points from both healthy and periodontitis-affected sites. Bacterial and human DNA yields were quantified using fluorometric measurements combined with qPCR, employing universal 16S primers for bacterial DNA and human-specific GAPDH primers.

Results: Among the tested kits, the DNeasy Blood and Tissue Kit demonstrated the highest efficiency, yielding significantly more total dsDNA in samples from healthy sites compared to both other kits and in samples from periodontitis-affected sites compared to one kit. Bacterial DNA yields were also significantly higher with the DNeasy Kit compared to one of the other kits in both health conditions.

Conclusion: These results suggest that one paper point is sufficient to extract DNA for subsequent bacterial analyses and that the DNeasy Blood and Tissue Kit appears to be the most efficient among the three tested kits.

Backgrounds: Periodontitis-induced alveolar bone loss is a primary cause of tooth loss. Porphyromonas gingivalis (P. gingivalis) is the primary pathogenic bacterium of periodontitis. Outer membrane vesicles (OMVs) derived from P. gingivalis (P.g-OMVs) contain various bioactive molecules, and several studies have suggested that P.g-OMVs may participate in alveolar bone loss caused by periodontitis.

Materials and methods: P.g-OMVs were isolated and characterized. The effect of P.g-OMVs on BMSCs proliferation and osteogenic differentiation was analyzed. High-throughput sequencing, RT-qPCR, and Western blot analysis were performed in BMSCs to unravel the underlying molecular mechanism.

Results: P.g-OMVs promoted proliferation but inhibited osteogenic differentiation of BMSCs. High-throughput sequencing results showed that serum amyloid A (SAA), especially SAA3, was robustly upregulated in P.g-OMVs-treated BMSCs. Upregulated SAA3 promoted TLR4, MyD88, and NF-κB p65 and inhibited osteogenic differentiation of P.g-OMVs-treated BMSCs. The knockdown of SAA3 in BMSCs downregulated P.g-OMVs-induced TLR4, MyD88, and NF-κB p65 and rescued P.g-OMVs-inhibited osteogenic differentiation.

Conclusions: Our results indicate that P.g-OMVs inhibit osteogenic differentiation of BMSCs via the SAA3-mediated TLR4/MyD88/NF-κB axis, providing novel targets for the treatment of periodontitis-induced alveolar bone loss.

Fusobacterium nucleatum, a microorganism ordinarily detected in the oral cavity, is considered as a pathobiont related to periodontitis and a range of human diseases, including colorectal cancer (CRC). The dynamics of how F. nucleatum encourages CRC tumorigenesis and progression has been well-investigated. Recently, mechanisms by which F. nucleatum regulates the tumor immune microenvironment (TiME) and subsequently alters CRC oncogenesis and advancement have drawn more and more attention. The TiME consists of immune cells and non-cellular components like cytokines in the tumor microenvironment. By contacting immune cells in the TiME, F. nucleatum fosters an immunosuppressive TiME, diminishes anti-tumor immunity and promotes CRC development. This also allows F. nucleatum to interfere with immunotherapy process and efficacy. In this review, we present a summary of how F. nucleatum interacts with immune cells within the TiME, thereby promoting CRC progression and influencing CRC immunotherapy effectiveness. This review also integrates insights from molecular pathological epidemiology (MPE) to contextualize host-microbe-environment interactions in CRC. We identify gaps in current knowledge and outline possible future research paths. These findings may offer valuable insights for future mechanistic research and the development of novel therapeutic strategies.