Journal of Oral Microbiology最新文献

The primary etiological agent for the initiation and progression of periodontal disease is the dental plaque biofilm which is an organized aggregation of microorganisms residing within a complex intercellular matrix. The non-specific plaque hypothesis was the first attempt to explain the role of the dental biofilm in the pathogenesis of periodontal diseases. However, the introduction of sophisticated diagnostic and laboratory assays has led to the realisation that the development of periodontitis requires more than a mere increase in the biomass of dental plaque. Indeed, multispecies biofilms exhibit complex interactions between the bacteria and the host. In addition, not all resident microorganisms within the biofilm are pathogenic, since beneficial bacteria exist that serve to maintain a symbiotic relationship between the plaque microbiome and the host's immune-inflammatory response, preventing the emergence of pathogenic microorganisms and the development of dysbiosis. This review aims to highlight the development and structure of the dental plaque biofilm and to explore current literature on the transition from a healthy (symbiotic) to a diseased (dysbiotic) biofilm in periodontitis and the associated immune-inflammatory responses that drive periodontal tissue destruction and form mechanistic pathways that impact other systemic non-communicable diseases.

Oral health and declining cognition may have a bi-directional association. We characterized the subgingival microbiota composition of subjects from normal cognition to severe cognitive decline in two cohorts. Memory and Periodontitis (MINOPAR) include 202 home-living participants (50-80 years) in Sweden. Finnish Oral Health Studies in Older Adults (FINORAL) include 174 participants (≥65 years) living in long-term care in Finland. We performed oral examination and assessed the cognitive level with Mini Mental State Examination (MMSE). We sequenced the 16S-rRNA gene (V3-V4 regions) to analyse the subgingival bacterial compositions. The microbial diversities only tended to differ between the MMSE categories, and the strongest determinants were increased probing pocket depth (PPD) and presence of caries. However, abundances of 101 taxa were associated with the MMSE score. After adjusting for age, sex, medications, PPD, and caries, only eight taxa retained the significance in the meta-analyses of the two cohorts. Especially Lachnospiraceae [XIV] at the family, genus, and species level increased with decreasing MMSE. Cognitive decline is associated with obvious changes in the composition of the oral microbiota. Impaired cognition is accompanied with poor oral health status and the appearance of major taxa of the gut microbiota in the oral cavity. Good oral health-care practices require special deliberations among older adults.

Objectives: To evaluate the effect and mechanism of action of the flavonoid phloretin on the growth and sucrose-dependent biofilm formation of Streptococcus mutans.

Methods: Minimum inhibitory concentration, viability, and biofilm susceptibility assays were conducted to assess antimicrobial and antibiofilm effect of phloretin. Biofilm composition and structure were analysed with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Water-soluble (WSG) and water-insoluble glucan (WIG) were determined using anthrone method. Lactic acid measurements and acid tolerance assay were performed to assess acidogenicity and aciduricity. Reverse transcription quantitative PCR (RT-qPCR) was used to measure the expression of virulence genes essential for surface attachment, biofilm formation, and quorum sensing.

Results: Phloretin inhibited S. mutans growth and viability in a dose-dependent manner. Furthermore, it reduced gtfB and gtfC gene expression, correlating with the reduction of extracellular polysaccharides (EPS)/bacteria and WIG/WSG ratio. Inhibition of comED and luxS gene expression, involved in stress tolerance, was associated with compromised acidogenicity and aciduricity of S. mutans.

Conclusions: Phloretin exhibits antibacterial properties against S. mutans, modulates acid production and tolerance, and reduces biofilm formation.

Clinical significance: Phloretin is a promising natural compound with pronounced inhibitory effect on key virulence factors of the cariogenic pathogen, S. mutans.

Objective: To develop an in vitro model for real-time monitoring of endodontic biofilm growth and evaluate the ex vivo effect of antibiotics on biofilm growth.

Material and methods: Root canal samples were taken from 40 patients and inoculated into 96-well plates in a system that measures biofilm growth through electrical impedance. Biofilm bacterial composition at the genus and species level was analyzed by Illumina sequencing. ANCOM-BC corrected data were used to compare bacterial composition after antibiotic treatment through compositional analysis, and to compare microbiological with clinical data.

Results: The stationary phase was reached at 8 hours. The biofilm formed had a similar bacterial composition to the inoculum, and Enterococcus faecalis was virtually absent from the samples. The bacterial composition and the effect of antibiotics were sample-dependent. Metronidazole was the antibiotic that most inhibited biofilm formation and azithromycin the one that inhibited it in the highest percentage of cases. The antibiotic effect could not be related to the biofilm original bacterial composition.

Conclusions: The impedance system allowed real-time monitoring of endodontic biofilm formation, and we propose it as a model for ex vivo evaluation of the whole biofilm susceptibility to antimicrobials, as opposed to evaluating antibiotic sensitivity of specific bacterial isolates.

Effective control of gene expression is crucial for understanding gene function in both eukaryotic and prokaryotic cells. While several inducible gene expression systems have been reported in Streptococcus mutans, a conditional pathogen that causes dental caries, the significant non-inducible basal expression in these systems seriously limits their utility, especially when studying lethal gene functions and molecular mechanisms. We introduce a tightly controlled xylose-inducible gene expression system, TC-Xyl, for Streptococcus mutans. Western blot results and fluorescence microscopy analysis indicate that TC-Xyl exhibits an extremely low non-inducible basal expression level and a sufficiently high expression level post-induction. Further, by constructing a mutation in which the only source FtsZ is under the control of TC-Xyl, we preliminarily explored the function of the ftsz gene. We found that FtsZ depletion is lethal to Streptococcus mutans, resulting in abnormal round cell shape and mini cell formation, suggesting FtsZ's role in maintaining cell shape stability.

Background: Dental caries is a multifactorial disease, and the bacteria such as Streptococcus mutans (S. mutans) is one of the risk factors. The poor effect of existing anti-bacterial is mainly related to drug resistance, the short time of drug action, and biofilm formation.

Methods: To address this concern, we report here on the cinnamaldehyde (CA) loaded chitosan (CS) nanocapsules (CA@CS NC) sustained release CA for antibacterial treatment. The size, ζ-potential, and morphology were characterized. The antibacterial activities in vitro were studied by growth curve assay, pH drop assay, biofilm assay, and qRT-PCR In addition, cytotoxicity assay, organ index, body weight, and histopathology results were analyzed to evaluate the safety and biocompatibility in a rat model.

Results: CA@CS NC can adsorb the bacterial membrane due to electronic interaction, releasing CA slowly for a long time. At the same time, it has reliable antibacterial activity against S. mutans and downregulated the expression levels of QS, virulence, biofilm, and adhesion genes. In addition, it greatly reduced the cytotoxicity of CA and significantly inhibited dental caries in rats without obvious toxicity.

Conclusion: Our results showed that CA@CS NC had antibacterial and antibiofilm effects on S. mutans and inhibit dental caries. Besides, it showed stronger efficacy and less toxicity, and was able to adsorb bacteria releasing CA slowly, providing a new nanomaterial solution for the treatment of dental caries.

The oral cavity is an unique ecosystem formed by different structures, tissues, and a complex microbial community formed by hundreds of different species of bacteria, fungi, viruses, phages, and the candidate phyla radiation (CPR) group, all living in symbiosis with healthy individuals. In an opposite state, dental caries is a biofilm-mediated dysbiosis that involves changes in the core microbiome composition and function, which leads to the demineralization of tooth tissues due to the fermentation of dietary carbohydrates, producing acid by select oral bacteria. The cariogenic biofilm is typically characterized by bacterial species with the ability of adhering to the saliva-coated tooth surface, production of exopolysaccharides-rich matrix (which will limit the diffusion of acidic products of carbohydrate fermentation), and the ability of surviving in this acidic environment. Besides years of research and dental treatment, dental caries remains the most common chronic disease in children worldwide. This article aims to bring an insightful discussion about important questions that remain unanswered in the Cariology and Oral Microbiology fields, to move Science forward, characterize the interrelationships of these communities, and understand mechanistic functions between microorganisms and the host, therefore leading to translatable knowledge that benefits the provision of care to our pediatric patients.

Aim: Our aim was to compare the prevalence and load of nine pathobionts in subgingival samples of healthy individuals and periodontitis patients from four different countries.

Methods: Five hundred and seven subgingival biofilm samples were collected from healthy subjects and periodontitis patients in Belgium, Chile, Peru and Spain. The prevalence and load of Eubacterium brachy, Filifactor alocis, Fretibacterium fastidiosum, Porphyromonas endodontalis, Porphyromonas gingivalis, Selenomonas sputigena, Treponema denticola, Tannerella forsythia and Treponema socranskii were measured by quantitative PCR.

Results: The association with periodontitis of all species, except for T. socranskii, was confirmed in all countries but Peru, where only P. endodontalis, P. gingivalis and T. denticola were found to be significantly associated. Moreover, most species showed higher loads at greater CAL and PPD, but not where there was BOP. Through Principal Component Analysis, samples showed clearly different distributions by diagnosis, despite observing a smaller separation in Peruvian samples.

Conclusions: Unlike prevalence, relative load was found to be a reliable variable to discriminate the association of the species with periodontitis. Based on this, F. alocis, P. endodontalis, P. gingivalis, T. denticola and T. forsythia may be biomarkers of disease in Belgium, Chile and Spain, due to their significantly higher abundance in periodontitis patients.

Acyl-homoserine lactones (AHLs) are typical quorum-sensing molecules of gram-negative bacteria. Recent evidence suggests that AHLs may also affect gram-positives, although knowledge of these interactions remains scarce. Here, we assessed the effect of AHLs on biofilm formation and transcriptional regulations in the gram-positive Enterococcus faecalis. Five E. faecalis strains were investigated herein. Crystal violet was employed to quantify the biomass formed, and confocal microscopy in combination with SYTO9/PI allowed the visualisation of biofilms' structure. The differential expression of 10 genes involved in quorum-sensing, biofilm formation and stress responses was evaluated using reverse-transcription-qPCR. The AHL exposure significantly increased biofilm production in strain ATCC 29212 and two isolates from infected dental roots, UmID4 and UmID5. In strains ATCC 29212 and UmID7, AHLs up-regulated the quorum-sensing genes (fsrC, cylA), the adhesins ace, efaA and asa1, together with the glycosyltransferase epaQ. In strain UmID7, AHL exposure additionally up-regulated two membrane-stress response genes (σ^V, groEL) associated with increased stress-tolerance and virulence. Altogether, our results demonstrate that AHLs promote biofilm formation and up-regulate a transcriptional network involved in virulence and stress tolerance in several E. faecalis strains. These data provide yet-unreported insights into E. faecalis biofilm responses to AHLs, a family of molecules long-considered the monopole of gram-negative signalling.

We assessed the level of evidence for the presence of new periodontal pathogens by (i) comparing the occurrence of non-classical periodontal taxa between healthy vs. periodontitis patients (Association study); (ii) assessing the modifications in the prevalence and levels of these species after treatments (Elimination study). In the Association study, we compared the prevalence and levels of 39 novel bacterial species between periodontally healthy and periodontitis patients. In the Elimination study, we analyzed samples from periodontitis patients assigned to receive scaling and root planing alone or with metronidazole+ amoxicillin TID/ 14 days. Levels of 79 bacterial species (39 novel and 40 classic) were assessed at baseline, 3 and 12 months post-therapy. All samples were analyzed using Checkerboard DNA-DNA hybridization. Out of the 39 novel species evaluated, eight were categorized as having strong and four as having moderate association with periodontitis. Our findings suggest strong evidence supporting Lancefieldella rimae, Cronobacter sakazakii, Pluralibacter gergoviae, Enterococcus faecalis, Eubacterium limosum, Filifactor alocis, Haemophilus influenzae, and Staphylococcus warneri, and moderate evidence supporting Escherichia coli, Fusobacterium necrophorum, Spiroplasma ixodetis, and Staphylococcus aureus as periodontal pathogens. These findings contribute to a better understanding of the etiology of periodontitis and may guide future diagnostic and interventional studies.