Journal of Oral Microbiology最新文献

Background: Streptococcus oralis is a commensal bacterium and an early biofilm coloniser found in the human oral cavity. One of the biofilm matrix constituents is bacterial extracellular DNA (eDNA). Neutrophils are innate immune cells that respond to biofilms, employing antimicrobial mechanisms such as neutrophil extracellular trap (NET) and reactive oxygen species (ROS) release. Here, bidirectional effects of neutrophils on S. oralis biofilms were investigated.

Materials and methods: Isolated neutrophils were introduced to S. oralis biofilms at different stages of biofilm development. Biofilm quantity was assessed by crystal violet technique, confocal microscopy and CFU enumeration. Surface adhesion during shear stress was quantified by spectrophotometry. Bacterial and neutrophil extracellular DNA within biofilms and ROS production were analysed using fluorescence and luminescence assays, and neutrophil-eDNA interactions were investigated by flow cytometry and fluorescence microscopy.

Results: Neutrophils decreased S. oralis biofilm quantity transiently and reduced eDNA but did not affect biofilm surface adhesion. Unexpectedly, CFUs were increased by neutrophils. Bacterial DNA was found to co-localise with neutrophil membranes. Neutrophils produced elevated total and intracellular ROS, however, no NETs in response to biofilms.

Conclusion: Neutrophils in vitro are not excessively activated by S. oralis biofilms but are able to reduce biofilm quantity in the short-term, possibly through interfering with eDNA.

Background and objective: Oral bacteria can translocate to the intestine, and their colonization efficiency is influenced by the gastrointestinal tract pH. Understanding how oral bacteria resist acidic environments is crucial for elucidating their role in gut health and disease.

Methods: To investigate the mechanisms of acid resistance in oral bacteria, an in vitro gastrointestinal tract Dynamic pH Model was established. This model was used to simulate the acidic conditions encountered by bacteria during their translocation from the mouth to the intestine.

Results: Fusobacterium nucleatum exhibited the highest survival rate in an acidified fluid mimicking the stomach pH (pH 1.5). The survival was significantly increased in the presence of erucic acid C22:1(n9) in cell membranes. Phylogenetic tree analysis revealed that C22:1(n9) synthesis was significantly associated with FnFabM gene expression in F. nucleatum at pH 1.5. Inhibition of FnFabM expression by cerulenin reduced the C22:1(n9) content and decreased the colonization efficiency of F. nucleatum in the stomach and jejunum of mice.

Conclusions: Oral F. nucleatum translocate to the intestine by resisting the acidic environment owing to the presence of erucic acid in its cell membrane, which is regulated by FnFabM. These results provide novel insights into the mechanisms underlying the oral bacteria survival in acidic environments and their potential to colonize the intestine; thus, shedding light on the oral-gut axis and its implications on human health.

Background: This study aims to develop an oral microbiota-based model for gastric cancer (GC) risk stratification and prognosis prediction.

Methods: Oral microbial markers for GC prognosis and risk stratification were identified from 99 GC patients, and their predictive potential was validated on an external dataset of 111 GC patients. The identified bacterial markers were used to construct a Deep Neural Network (DNN) model, a Random Forest (RF) model, and a Support Vector Machine (SVM) model for predicting GC prognosis.

Results: GC patients with <3 years of survival showed a higher abundance of Aggregatibacter and diminished abundances of Filifactor and Moryella than those who survived ≥3 years. The Boruta algorithm unearthed Leptotrichia as another significant marker for GC prognosis. Consequently, a DNN model was constructed based on the relative abundances of these bacteria, predicting 3-year and 5-year survival in GC patients with Area Under Curve of 0.814 and 0.912, respectively. Notably, the DNN model outperformed the TNM staging system, SVM and RF models. The prognostic value of these bacterial markers was further reinforced by external validation.

Conclusion: The oral microbiota-based DNN model may advance GC prognosis. The biological functions of these oral bacterial markers warrant further investigation from the perspective of GC progression.

Background: The aim of this article is to evaluate the effect of different portions of Platelet Rich Fibrin (PRF) membranes and liquid-PRF, prepared by two distinct protocols/centrifuges each, on the multispecies subgingival biofilm.

Materials and methods: PRF membranes and liquid-PRF were prepared using two protocols: centrifuge 1 uses fixed acceleration while centrifuge 2, progressive acceleration. PRF samples were introduced into device concurrently with 33-species bacterial inoculum. After seven days, biofilm metabolic activity (MA) and microbial profile were evaluated through colorimetric reaction and DNA-DNA hybridization, respectively.

Results: Among PRF membranes, the ones from centrifuge 1 led to better reduction in MA, total biofilm, and F. periodonticum, P. gingivalis and T. forsythia counts when compared to untreated/centrifuge 2 treated biofilms. However, centrifuge 2 liquid-PRF reduced MA, total biofilm and F. periodonticum counts when compared to untreated/centrifuge 1 treated-biofilms.

Conclusion: PRF membrane and exhibited comparable antibiofilm activity. However, PRF distinct forms, obtained by same centrifugation protocol, may present different antimicrobial properties.

Background: Propolis mouthwash (PROP-M) has demonstrated antibacterial properties like those of chlorhexidine mouthwash (CHX-M). However, its impact on the abundance of oral nitrite-producing species (NPS) and nitrite-producing activity (NPA) remains unexplored.

Methods: Forty-five healthy individuals were randomised into 2 groups to rinse their mouth twice a day for seven days with either CHX-M (n = 21) or PROP-M (n = 24). Metagenomic sequencing (16S rRNA) was performed on saliva samples collected before and after each treatment. Additionally, salivary biomarkers and blood pressure were measured.

Results: CHX-M increased the relative abundance of NPS (p < 0.001) but significantly impaired the NPA (p < 0.001) compared to baseline and PROP-M. No significant differences in the relative abundance of NPS and NPA were observed in the PROP-M group. However, a significant increase of plasma nitrate (+7 µmol/L, p = 0.047) and a decrease in systolic BP (-2 mmHg, p = 0.022) was observed in this group compared to the baseline.

Conclusion: The results indicate that PROP-M had a smaller effect on the abundance of NPS and NPA compared to CHX-M. Additionally, PROP-M reduced blood pressure in healthy individuals, but this effect was not associated with changes in the oral microbiome.

Objective: Both periodontal disease and obesity are risk factors for dementia, but their links to 1brain function remain unclear. In this study, we examined the effects of oral infection with a periodontal pathogen on cognitive function in a mouse model of obesity, focusing on the roles of microglia.

Methods: To create a mouse model of diet-induced obesity and periodontitis, male C57BL/6 J mice were first fed a high-fat diet containing 60% lipid calories for 18 weeks, beginning at 12 weeks of age, to achieve diet-induced obesity. Then, Porphyromonas gingivalis administration in the oral cavity twice weekly for 6 weeks was performed to induce periodontitis in obese mice.

Results: Obese mice orally exposed to P. gingivalis showed cognitive impairment in the novel object recognition test. Increased expression levels of inflammatory cytokines (e.g. interleukin-1β and tumor necrosis factor-α) were observed in the hippocampus of P. gingivalis-treated obese mice. Immunohistochemical analysis revealed that microglia cell body size was increased in the hippocampus and prefrontal cortex of P. gingivalis-treated obese mice, indicating microglial activation. Furthermore, depletion of microglia by PLX3397, a colony-stimulating factor 1 receptor inhibitor, ameliorated cognitive dysfunction.

Conclusion: These results suggest that microglia mediate periodontal infection-induced cognitive dysfunction in obesity.

Background: Biofilm formation on implant-abutment surfaces can cause inflammatory reactions. Ethical concerns often limit intraoral testing, necessitating preliminary in vitro or animal studies. Here, we propose an in vitro model using human saliva and hypothesize that this model has the potential to closely mimic the dynamics of biofilm formation on implant-abutment material surfaces in vivo.

Methods: A saliva stock was mixed with modified Brain-Heart-Infusion medium to form biofilms on Titanium-Aluminum-Vanadium (Ti6Al4V) and Yttria-partially Stabilized Zirconia (Y-TZP) discs in 24-well plates. Biofilm analyses included crystal violet staining, intact cell quantification with BactoBox, 16S rRNA gene analysis, and short-chain fatty acids measurement. As a control, discs were worn in maxillary splints by four subjects for four days to induce in vivo biofilm formation.

Results: After four days, biofilms fully covered Ti6Al4V and Y-TZP discs both in vivo and in vitro, with similar cell viability. There was a 60.31% overlap of genera between in vitro and in vivo biofilms in the early stages, and 41% in the late stages. Ten key oral bacteria, including Streptococcus, Haemophilus, Neisseria, Veillonella, and Porphyromonas, were still detectable in vitro, representing the common stages of oral biofilm formation.

Conclusion: This in vitro model effectively simulates oral conditions and provides valuable insights into biofilm dynamics.

Background: Probiotics serve as a novel preventive or therapeutic approach for dental caries owing to their ability to reverse dysbiosis and restore a healthy microbiota. Here, we identified Burkholderia ambifaria AFS098024 as a probiotic candidate isolated from plants.

Methods: The safety of B. ambifaria was evaluated by hemolytic activity, D-lactic acid production and antibiotic susceptibility. In vitro biofilm model derived from the saliva of caries-free and caries-active donors and in vivo rat caries model were used to assess the efficacy of B. ambifaria in caries prevention and treatment.

Results: B. ambifaria was safe as a probiotic candidate and it could integrate with in vitro biofilm model. It significantly reduced the biomass and lactate production of biofilms from caries-active donors and disrupted biofilm structures. B. ambifaria effectively reduced the severity of carious lesions in rat molars, regardless of the inoculation sequence. Molars pretreated or treated with B. ambifaria demonstrated notably higher enamel volumes. Additionally, colonization of rat molars by B. ambifaria persisted for 6 weeks.

Conclusion: The B. ambifaria strain used in this study holds promise as a probiotic for inhibiting dental caries, both in vitro and in vivo.

Methanobrevibacter oralis (M. oralis) has predominated human oral microbiota methanogenic archaea as far back as the Palaeolithic era in Neanderthal populations and gained dominance from the 18^th century onwards. M. oralis was initially isolated from dental plaque samples collected from two apparently healthy individuals allowing its first characterization. The culture of M. oralis is fastidious and has been the subject of several studies to improve its laboratory growth. Various PCR methods are used to identify M. oralis, targeting either the 16S rRNA gene or the mcrA gene. However, only one RTQ-PCR system, based on a chaperonin gene, offers specificity, and allows for microbial load quantification. Next-generation sequencing contributed five draft genomes, each approximately 2.08 Mb (±0.052 Mb) with a 27.82 (±0.104) average GC%, and two ancient metagenomic assembled genomes. M. oralis was then detected in various oral cavity sites in healthy individuals and those diagnosed with oral pathologies, notably periodontal diseases, and endodontic infections. Transmission pathways, possibly involving maternal milk and breastfeeding, remain to be clarified. M. oralis was further detected in brain abscesses and respiratory tract samples, bringing its clinical significance into question. This review summarizes the current knowledge about M. oralis, emphasizing its prevalence, associations with dysbiosis and pathologies in oral and extra-oral situations, and symbiotic relationships, with the aim of paving the way for further investigations.