Journal of Oral Microbiology最新文献

Background: Dental caries is a bacterial-mediated infectious disease that affects the hard tissues of the tooth, with Streptococcus mutans being the primary cariogenic pathogen due to its robust biofilm-forming ability. Controlling biofilm formation is essential for caries prevention. Recent studies have indicated that D-amino acids, which are not incorporated into proteins, play regulatory roles in bacterial processes such as growth inhibition and biofilm dispersal. However, whether D-amino acids can inhibit the growth of S. mutans remains controversial. This study aimed to investigate the effects of D-amino acids on S. mutans growth and biofilm formation in vitro, as well as their anti-caries efficacy in a rat caries model.

Materials and methods: This study utilized Streptococcus mutans UA159 to screen 15 D-amino acids for growth inhibition, identifying D-histidine (D-His) as the most effective. Minimum inhibitory concentration, growth curves, biofilm assays, and transcriptomic analysis were performed in vitro. Anti-caries efficacy was evaluated in a rat model using Micro-CT and Keyes scoring.

Results: D-His significantly inhibits the planktonic growth of S. mutans and delays biofilm formation, particularly in the early stages. Furthermore, RNA sequencing revealed 417 upregulated genes and 394 downregulated genes in D-His-treated S. mutans, with significant alterations in pathways related to carbohydrate utilization, protein biosynthesis, and transmembrane transport. Moreover, D-His exhibited effective caries prevention in an in vivo rat model.

Conclusion: These findings suggest that D-His has potential as an anti-caries agent by targeting S. mutans growth and biofilm dynamics.

Background/objective: Cariogenic biofilms possess a rich extracellular polysaccharide (EPS) matrix, which can reduce the penetration of anticaries agents such as nanoparticle-based technologies. The aim of this study was to assess the potential of dextranase, an EPS-degrading enzyme, to enhance nanoparticle penetration into Streptococcus mutans in vitro biofilms.

Methods: Commercially available fluorescent nanoparticles (nanospheres, average diameter around 200 nm) were used as a proxy for nanoparticle treatments. Biofilms of fluorescent S. mutans 3209/pVMCherry were developed over 48 h in 24-well glass bottom microplates, simulating daily feast (tryptic soy broth (TSB) supplemented with 1% sucrose) and famine periods (TSB supplemented with 0.1 mM glucose). Nanoparticles were co-administered to biofilms with either dextranase (10 U/mL) or pH 6.5 phosphate buffer (placebo). Time-lapse confocal laser scanning microscopy was used to capture six image stacks over approximately 60 minutes of nanoparticle movement through the biofilm. In-house-developed quantitative image analysis methods assessed nanoparticle penetration.

Results: Nanoparticle signal intensity and overlapping signal with cells increased in the presence of dextranase, being significantly higher in the last two CLSM scans compared with the initial one (p < 0.05). Biofilm architecture changed under dextranase, increasing the interaction of nanoparticles with biofilm components.

Conclusion: Dextranase showed potential to enhance nanoparticle-based anticaries therapies.

Key messages: Dextranase increases the penetration of nanoparticles in cariogenic, extracellular polysaccharide-rich dental biofilms.

Background: Hexylresorcinol (HR) lozenges provide symptomatic relief for sore throats. Despite its recognised anaesthetic and antiseptic properties, evidence of HR bactericidal activity in these formulations is limited, being only recently described in planktonic bacteria. We defined antimicrobial/antiviral activity in planktonic and biofilm models and characterised the pharmacokinetics of HR release from lozenges.

Methods: Antimicrobial activity (purified or released from lozenges) was determined against oropharyngeal pathogens using minimum inhibitory concentration (MIC) and Log₁₀ reduction assays. Antiviral activity was determined by suspension test (EN14476). Antibiofilm effects employed minimum biofilm eradication concentration assays and confocal laser scanning microscopy. HR release from lozenges was studied in vitro and in vivo using HPLC.

Results: HR exhibited MICs ≤ 16 µg/mL against 19/25 strains including: Streptococcus, Staphylococcus and Candida spp. Marked bactericidal activity (>3_log10; >99.9% reduction) occurred within 10 minutes. Significant anti-biofilm activity was evident in streptococcal and candidal biofilms (p < 0.05). Log₁₀ reduction in virucidal infectivity of HR in lozenges ranged from 1-log₁₀ to 3.5-log₁₀. In vivo, HR exhibited rapid release (within 1 minute) from lozenges into saliva.

Conclusion: Rapid release and antimicrobial activity of HR against oropharyngeal pathogens was evident, occurring at concentrations ≥ 2-fold lower than present in saliva, highlighting the potential application of HR in the treatment of oropharyngeal infections.

Background: Oral nitrate-reducing bacteria are associated with good oral health, with inorganic nitrate specifically promoting the growth of these beneficial bacteria. Sugar alcohols affect the composition of oral microbiota, potentially impacting oral health. The present study aimed to investigate the combined effects of nitrate and sugar alcohols on nitrate-reducing bacteria and nitrate metabolism in oral microbiota cultured in vitro.

Methods: Species-level microbial analysis using 16S rRNA gene sequencing of DNA extracted from the supragingival plaque-derived biofilm cultured under micro-aerobic conditions for 48 h with nitrate and/or sugar alcohols was conducted. Nitrate metabolites, lactate, and pH in culture supernatants were also measured.

Results: The combined addition of nitrate and erythritol, but not xylitol or sorbitol, significantly increased the relative abundance of Haemophilus parainfluenzae and Neisseria subflava, which are nitrate-reducing bacteria. This shift was accompanied by a corresponding decrease in Streptococcus oralis, which simultaneously induced an increase in the nitrate-reducing capacity and a decrease in lactate production and acidification from sugar metabolism.

Conclusions: The combination of nitrate and erythritol serve as a preventive and therapeutic approach for periodontitis or dental caries by promoting the growth of oral commensal nitrate-reducing bacteria. However, human clinical studies are required to clarify these beneficial effects.

White spot lesions (WSLs) are a common complication of orthodontic treatment. However, the cariogenic discrepancy in the supragingival microbiome between demineralized and non-demineralized surfaces and the influence of Candida albicans associated with WSLs remain unexplored. This study investigated the changes in supragingival microbiome of orthodontic adolescents with WSLs, encompassing both demineralized and non-demineralized sites, and explored C. albicans colonization in these patients. Supragingival plaques were collected from 29 orthodontic adolescents with WSLs (categorized into demineralized and non-demineralized groups based on the presence/absence of demineralization at sampling sites) and 23 healthy orthodontic adolescents. Supragingival microbiome composition was evaluated using 16S rRNA sequencing, and C. albicans colonization was identified using fungal culture methods. The supragingival microbiome on non-demineralized surfaces showed intermediate cariogenic potential between demineralized and healthy states, but closer to the demineralized state. C. albicans exhibited a propensity for colonization in WSLs patients without site-specificity. C. albicans influenced bacterial composition, with Streptococcus mutans significantly enriched on the demineralized surfaces of C. albicans-positive patients. In orthodontic adolescents with WSLs, non-demineralized surfaces showed microbiome shifts, necessitating interventions to promote a healthy microbiome. C. albicans can impact microbiome composition and potentially contribute to WSLs pathogenesis.

Aim: This study aims to investigate the inhibitory effect of gigantol against P. gingivalis.

Materials and methods: The effect of gigantol against the planktonic culture of P. gingivalis was determined by broth microdilution and CFU assay. In addition, bacterial cell surface hydrophobicity and aggregation were elucidated. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were performed to observe biofilm thickness and the biofilm structure, respectively. The gingipain-related genes were evaluated using qPCR. Moreover, molecular docking analysis has also detected the interaction between gigantol and gingipains. Finally, the cytotoxicity effect of gigantol on human gingival fibroblasts (HGFs) was also observed by MTT assay.

Results: The MIC and MBC of gigantol against planktonic P. gingivalis were 0.312 mg/mL. The findings indicated that the effect of gigantol at sub-MIC concentrations can also suppress bacterial growth. Additionally, this compound increased cell surface hydrophobicity and aggregation. CLSM images demonstrated its inhibitory effect on the pre-formed biofilm of P. gingivalis. SEM exhibited that gigantol could affect the bacterial membrane. The downregulation of gingipain-related gene expression was observed. Moreover, molecular docking showed that this compound blocks Kpg and RgpB proteases. Furthermore, the cytotoxicity of gigantol on HGFs exhibited less toxicity than 0.12% CHX.

Conclusion: Our findings indicated that gigantol inhibits the P. gingivalis biofilm and establishment, which may lead to a potential therapeutic compound for periodontitis patients.

Background: This study examines the relationship between supragingival plaque control and subgingival microbiota during periodontal therapy, focusing on microbial clusters associated with plaque levels.

Methods: Data were drawn from a 26-month multicenter, double-blinded, randomized, placebo-controlled trial. Supragingival plaque was measured using the O'Leary index, and subgingival microbiota were profiled via Illumina 16S rRNA gene sequencing. A novel topic modelling approach using cross-validated Latent Dirichlet Allocation (LDA) identified microbial clusters, and negative binomial mixed models evaluated their association with plaque levels.

Results: Supragingival plaque was positively associated with bleeding on probing (BOP) and microbial diversity, but not with dysbiosis. A specific subgingival microbial cluster dominated by Selenomonas and Leptotrichia was linked to elevated plaque levels and increased in abundance following both antibiotic and placebo treatments. The odds ratio for plaque associated with this cluster was 1.20 (95% CI: 1.07-1.35). Stratified analyses showed this association was reduced in the antibiotic group but remained in the placebo group.

Conclusion: Ineffective supragingival plaque control correlates with increased BOP and microbial diversity, though not necessarily with dysbiosis. Adjunctive antibiotics may promote a more cariogenic subgingival microbiota by disrupting the association between plaque accumulation and the abundance of acidogenic taxa such as Selenomonas and Leptotrichia.

Background: Nitrite (NO₂ ^-) is produced through enzymatic reduction of dietary nitrate (NO₃ ^-) by oral bacteria: a process contributing to cardiovascular - and possibly oral - health. NO₂ ^- quantitation in biological samples is a complex exercise, and available methods are not well-adapted for chairside use. Therefore, we aimed to develop and evaluate a semi-quantitative chairside test for NO₂ ^- in oral samples. We also evaluated NO₂ ^- generation in several bacterial species in vitro.

Materials and methods: From 12 healthy individuals, tongue, saliva and plaque samples were collected and evaluated chairside across 4 weeks, using the rapid Griess assay (RGA). The RGA was further used to test bacterial species for NO₂ ^- production.

Results: In saliva, plaque and tongue samples, low, variable and high NO₂ ^- levels, respectively, were found. Tongue samples were the most stable over time. High and medium NO₂ ^- production capacities were shown by Actinomyces spp. (including Schaalia odontolytica), Veillonella parvula, and Rothia spp. RGA results were reproducible.

Conclusion: The RGA provided stable and reliable results for chairside NO₂ ^- semi-quantitation, and revealed elevated and stable NO₂ ^- levels on the tongue. In vitro, bacterial NO₂ ^- production was consistent with the available literature, but uncertainty remains regarding Neisseria spp. Our results showed promise for clinical and research applications of the RGA.

Objectives: To investigate the oral microbiome and metabolome longitudinal changes associated with orthodontic treatment-induced gingival enlargement (OT-GE).

Methods: Twenty-six subjects were divided into case and control groups based on the gingival overgrowth index (GOi). The OT-GE group was divided into the no gingival enlargement (OT-GE0, n = 5) and persistent gingival enlargement (OT-GE1, n = 11). The control group included orthodontic treatment periodontal health (OT-GH, n = 5), and no orthodontic treatment periodontal health (NOT-GH, n = 5). Microbial composition and metabolites in saliva were investigated using cross-omics.

Results: Longitudinal analysis linked orthodontic treatment-induced gingival enlargement to distinct oral microbiome and metabolome shifts. The OT-GE group showed significantly higher bleeding on probing (BOP), plaque scores (p < 0.001), probing depth, GOi, and ligature wire differences (p < 0.05) versus controls. Microbial diversity and species richness were elevated in OT-GE (p < 0.05), though no differences emerged between OT-GE0 and OT-GE1) subgroup (p > 0.05). Cross-omics identified specific periodontal pathogens and metabolites linked to gingival enlargement. Disrupted amino acid biosynthesis pathways, particularly citrulline metabolism, correlated with functional gene dysregulation and microbial imbalance. Aberrant citrulline intake appeared to drive dysbiosis, potentially contributing to gingival overgrowth.

Conclusions: OT-GE pathogenesis involves functional gene-regulated metabolite metabolism influencing periodontal pathogens.

Introduction: Coaggregation may reduce the abundance of bacteria in physiological fluids, such as saliva, as aggregated bacteria are cleared more easily than planktonic cells. This study aimed to identify Lactobacillus strains that coaggregate with oral pathogens with the perspective of using this approach to improve oral health.

Material and methods: Coaggregation of 719 postbiotic Lactobacillus strains with target pathogens Fusobacterium nucleatum, Porphyromonas gingivalis, and Prevotella intermedia was quantified by absorbance. Coaggregation efficacy of selected strains with clinical isolates and in the presence of other salivary bacteria was determined by flow cytometry. Brightfield and confocal microscopy were applied to characterize the size and structure of coaggregates. Pangenome analysis was used to identify genomic regions potentially involved in the coaggregation activity.

Results: Two strains, Lacticaseibacillus rhamnosus 1B06 and Lacticaseibacillus paracasei 8A12, coaggregated efficiently with all three target pathogens and clinical isolates of the same species even in the presence of other salivary bacteria. The coaggregation capability of the selected Lactobacillus strains was unique and could not be reproduced with other genetically similar lactic acid bacteria of the same species.

Conclusion: Lactobacillus strains capable of coaggregating oral pathogens were identified as promising candidates for the development of new postbiotic ingredients for oral hygiene products.