Oral microbial communities: biofilms, interactions, and genetic systems

Acquired pellicle engineering: a fascinating approach to prevent demineralization

The acquired enamel pellicle (AEP) consists of an organic, acellular, and bacteria-free film, formed in vivo as a result of biomolecules adsorption onto the tooth surface. It is composed of proteins, glycoproteins, lipids, phospholipids, and other macromolecules, such as carbohydrates. The AEP formation process is complex and can be divided into three stages: initiation, development, and maturation. The pellicle has two main layers: the globular and basal layers. The basal layer offers the most protection against demineralization, as the subsequent globular layer is weaker and less tenacious. The formation of the AEP can be influenced by various factors, such as the physicochemical properties of the teeth, location in the oral cavity, pathologies, and even the oral microbiota. With the advancement of "omics" techniques, it has been possible to observe the presence of acid-resistant proteins in the AEP, which allowed the development of the "acquired pellicle engineering" strategy. This strategy involves enriching and modifying the basal layer with acid-resistant proteins. Among these proteins, hemoglobin, statherin-derived peptide, and a protein derived from sugarcane stand out. The objective of this literature review is to provide a comprehensive overview of the AEP, detailing its composition, formation process, and protective functions. Additionally, the review aims to explore recent advances in the field of "acquired pellicle engineering," highlighting the acid-resistant proteins of the AEP and their potential applications in dentistry. Finally, the review intends to highlight the clinical implications of these findings and how they may contribute to the development of new strategies for the prevention and treatment of dental pathologies according to published studies.

Metabolomics for dental caries diagnosis: Past, present, and future

Dental caries, a prevalent global infectious condition affecting over 95% of adults, remains elusive in its precise etiology. Addressing the complex dynamics of caries demands a thorough exploration of taxonomic, potential, active, and encoded functions within the oral ecosystem. Metabolomic profiling emerges as a crucial tool, offering immediate insights into microecosystem physiology and linking directly to the phenotype. Identified metabolites, indicative of caries status, play a pivotal role in unraveling the metabolic processes underlying the disease. Despite challenges in metabolite variability, the use of metabolomics, particularly via mass spectrometry and nuclear magnetic resonance spectroscopy, holds promise in caries research. This review comprehensively examines metabolomics in caries prevention, diagnosis, and treatment, highlighting distinct metabolite expression patterns and their associations with disease-related bacterial communities. Pioneering in approach, it integrates singular and combinatory metabolomics methodologies, diverse biofluids, and study designs, critically evaluating prior limitations while offering expert insights for future investigations. By synthesizing existing knowledge, this review significantly advances our comprehension of caries, providing a foundation for improved prevention and treatment strategies.

Toxic cultures: e-cigarettes and the oral microbial exposome

We tested the hypothesis that e-cigarette aerosol is metabolized by the indigenous oral microbiome, leading to structural and functional alterations. We combined untargeted metabolomics of in vitro commensal-rich and pathogen-rich biofilms with metatranscriptomics and fluorescent microscopy and verified the results in human samples. Spectral deconvolution of 4215 peaks identified 969 exposomal and endogenous metabolites that mapped to 23 metabolic pathways. The metabolites clustered by both aerosol characteristics and biofilm composition; and several were verified in human saliva of vapers. E-cigarette exposure upregulated xenobiotic degradation, capsule, peptidoglycan biosynthesis, organic carbon-compound metabolism, antimicrobial resistance, and secretion systems. E-cigarette exposure also altered biofilm architecture characterized by low surface-area to biovolume ratio, high biomass, and diffusion distance. In conclusion, our data suggest that bacterial metabolism of e-cigarette aerosol triggers a quorum-sensing-regulated stress response which mediates the formation of dense, exopolysaccharide-rich biofilms in health-compatible communities and antibiotic resistance and virulence amplification in disease-associated communities.

Biofilm-Associated Candidiasis: Pathogenesis, Prevalence, Challenges and Therapeutic Options

The rising prevalence of fungal infections, especially those caused by Candida species, presents a major risk to global health. With approximately 1.5 million deaths annually, the urgency for effective treatment options has never been greater. Candida spp. are the leading cause of invasive infections, significantly impacting immunocompromised patients and those in healthcare settings. C. albicans, C. parapsilosis and the emerging species C. auris are categorized as highly dangerous species because of their pathogenic potential and increasing drug resistance. This review comparatively describes the formation of microbial biofilms of both bacterial and fungal origin, including major pathogens, thereby creating a novel focus. Biofilms can further complicate treatment, as these structures provide enhanced resistance to antifungal therapies. Traditional antifungal agents, including polyenes, azoles and echinocandins, have shown effectiveness, yet resistance development continues to rise, necessitating the exploration of novel therapeutic approaches. Antimicrobial peptides (AMPs) such as the anti-biofilm peptides Pom-1 and Cm-p5 originally isolated from snails represent promising candidates due to their unique mechanisms of action and neglectable cytotoxicity. This review article discusses the challenges posed by Candida infections, the characteristics of important species, the role of biofilms in virulence and the potential of new therapeutic options like AMPs.

Streptococcus mutans biofilms in the establishment of dental caries: a review

Dental caries is considered as the most common and multifactorial disease worldwide, caused by a variety of oral microorganisms like Streptococcus spp., Veillonella spp., Actinomyces spp., Bifidobacterium spp., and Lactobacillus fermentum, which colonize food debris in oral cavities. Of them, Streptococcus mutans is the predominant bacterium and can induce progressive tooth destruction, especially during dentition. The superior characteristics of S. mutans, such as the presence of the cell surface protein P1 and exopolysaccharide-synthesizing enzymes, acid tolerance, biofilm-forming ability mediated by brpA gene, and multidrug resistance, render it a highly virulent pathogen in the etiology of dental caries. Given its significant role in dental caries, extensive research has been conducted over the past few decades, focusing on the development of specific antimicrobial treatments, and other innovative therapeutic approaches. To gain deeper insights into the genetic diversity and epidemiological patterns of S. mutans, various genotypic methods have been developed and successfully employed. By combining the insights gained from genetic studies of S. mutans with the suitable control measures against the biofilm, we can develop innovative and effective strategies for preventing and treating dental caries.

Paving the way for the use of Statherin-Derived Peptide (StN15) to control caries through acquired pellicle and biofilm microbiome engineering: Proof-of-concept in vitro/in vivo studies

OBJECTIVE

This proof-of-concept sequence of in vivo/in vitro studies aimed to unveil the role of acquired enamel pellicle (AEP) engineering with statherin-derived peptide (StN15) on the AEP protein profile, enamel biofilm microbiome in vivo and on enamel demineralization in vitro.

DESIGN

In vivo studies, 10 volunteers, in 2 independent experiments (2 days each), rinsed (10 mL,1 min) with: deionized water (negative control) or 1.88 × 10-5 M StN15. The AEP, formed along 2 h and the biofilm, along 3 h, were collected. AEP was analyzed by quantitative shotgun-label-free proteomics. The enamel biofilm microbiome was evaluated using 16S-rRNA Next Generation Sequencing (NGS). An in vitro model with microcosm biofilm was employed. Bovine enamel samples (n = 72) were treated with 1) Phosphate-Buffer-Solution (PBS), 2) 0.12 %Chlorhexidine, 3) 500ppmNaF; 4) 1.88 × 10-5MStN15; 5) 3.76 × 10-5MStN15 and 6) 7.52 × 10-5MStN15. Biofilm was supplemented with human saliva and McBain saliva and cultivated for 5 days. Resazurin, colony forming units (CFU) and Transversal Microradiography Analysis-(TMR) were performed.

RESULTS

Proteomic results showed several proteins with acid-resistant, calcium-binding, and antimicrobial properties in the StN15 group. The microbiome corroborated these findings, reducing bacteria that are closely related to dental caries in the StN15 group, compared to the PBS. The microcosm biofilm showed that the lowest concentration of StN15 was the most efficient in reducing bacterial activity, CFU and enamel demineralization compared to PBS.

CONCLUSION

StN15 can effectively alter the AEP proteome to inhibit initial bacterial colonization, thereby mitigating enamel demineralization. Future research should explore clinical applications and elucidate the mechanisms underlying the protective effects of StN15.

Development of a conditional plasmid for gene deletion in non-model Fusobacterium nucleatum strains

Fusobacterium nucleatum is an opportunistic pathogen with four subspecies: nucleatum (FNN), vincentii (FNV), polymorphum (FNP), and animalis (FNA), each with distinct disease potentials. Research on fusobacterial pathogenesis has mainly focused on the model strain ATCC 23726 from FNN. However, this narrow focus may overlook significant behaviors of other FNN strains and those from other subspecies, given the genetic and phenotypic diversity within F. nucleatum. While ATCC 23726 is highly transformable, most other Fusobacterium strains exhibit low transformation efficiency, complicating traditional gene deletion methods that rely on non-replicating plasmids. To address this, we developed a conditional plasmid system in which the RepA protein, essential for replication of a pCWU6-based shuttle plasmid, is controlled by an inducible system combining an fdx promoter with a theophylline-responsive riboswitch. This system allows plasmid replication in host cells upon induction and plasmid loss when the inducer is removed, forcing chromosomal integration via homologous recombination in the presence of the antibiotic thiamphenicol. We validated this approach by targeting the galK gene, successfully generating mutants in FNN (ATCC 23726, CTI-2), FNP (ATCC 10953), FNA (21_1A), and the closely related species Fusobacterium periodonticum. Incorporating a sacB counterselection marker in this conditional plasmid enabled the deletion of the radD gene in non-model strains. Interestingly, while radD deletion in 23726, 10953, and 21_1A abolished coaggregation with Actinomyces oris, the CTI-2 mutant retained this ability, suggesting the involvement of other unknown adhesins. This work significantly advances gene deletion in genetically recalcitrant F. nucleatum strains, enhancing our understanding of this pathogen.IMPORTANCEFusobacterium nucleatum is implicated in various human diseases, including periodontal disease, preterm birth, and colorectal cancer, often linked to specific strains and reflecting the species' genetic and phenotypic diversity. Despite this diversity, most genetic research has centered on the model strain ATCC 23726, potentially missing key aspects of other strains' pathogenic potential. This study addresses a critical gap by developing a novel conditional plasmid system that enables gene deletion in genetically recalcitrant strains of F. nucleatum. We successfully deleted genes in the FNN clinical strain CTI-2, the FNA strain 21_1A, and F. periodonticum for the first time. Our findings, particularly the varying behavior of the radD gene production in coaggregation across strains, underscore the complexity of F. nucleatum and the need for broader genetic studies. This work advances our understanding of F. nucleatum virulence at the strain level and provides a valuable tool for future bacterial genetics research.

Comparative analysis of salivary antimicrobial resistance genes in dental students: A PCR and questionnaire study

INTRODUCTION

Antimicrobial resistance (AMR) is a major global healthcare challenge, with limited treatment options due to the decline in new antibiotics. The human oral cavity, home to diverse bacteria, is crucial for maintaining oral and systemic health. Recent studies suggest that saliva may serve as a reservoir for AMR genes. However, there is a lack of research on this topic in the UAE and most Middle Eastern countries. This study investigated the presence of AMR genes in saliva from forty 5th-year dental students and forty 1st-year dental students.

MATERIALS & METHODS

Demographic and health information was collected via a 28-question structured questionnaire. Real-Time PCR was used to detect a panel of preselected AMR genes in bacterial DNA from saliva samples.

RESULTS

Participants' ages ranged from 20 to 31 years, with 41 females and 39 males. The prevalence of AMR genes varied: blaCTX-M grp 1 (29%), blaCTX-M grp 9 (85%), blaCTX-M grp 8 (39%), blaOXA-48 (69%), blaKPC-1 (6%), blaVIM (49%), DHA (53%), ACC (25%), MOX (59%), armA (83%), and rmtB (63%). There were no significant differences in AMR gene prevalence between 5th-year and 1st-year students or between male and female students.

CONCLUSION

The study revealed a high occurrence of AMR genes in the oral microbiome. Comprehensive metagenomic analysis is recommended to further evaluate the prevalence and relative abundance of these genes in the UAE population. Establishing a database for these ARGs could aid in effective future monitoring.

Anti-caries effect of a novel elastic silicone appliance material incorporating sodium fluoride

Introduction

This study developed an elastic silicone appliance material incorporating sodium fluoride (NaF) and evaluated its mechanical properties, biocompatibility, antibacterial effects, and remineralization potential.

Methods

Silicone components A and B were combined with varying concentrations of NaF (0.5, 1, 1.5, 2, and 2.5%), thoroughly mixed, and transferred into molds. After drying and curing, the resulting orthodontic appliance was retrieved from the mold and underwent finishing processes, followed by the assessment of its mechanical properties, cytotoxicity, and antibacterial impact. Additionally, the impact of this novel silicone appliance material on salivary biofilm's activity and acid production was evaluated in samples from children with severe early childhood caries (S-ECC). The hardness of demineralized and remineralized bovine enamel was measured.

Results

Incorporating NaF (0.5, 1, and 1.5%) resulted in no cytotoxic effects, with cell viability >85%. The fluoride release rate initially increased over 14 days, followed by a gradual decline, maintaining a steady release for approximately 28 days. Incorporating 1.5% NaF preserved the mechanical properties and exhibited specific antibacterial properties that inhibited the growth, biofilm formation, and acid production activity of Streptococcus mutans (S. mutans) and saliva biofilms from S-ECC children. Furthermore, all concentrations of the samples helped improve enamel hardness loss.

Discussion

The novel silicone appliance material incorporating NaF exhibited antibacterial, fluoride releasing, and enamel remineralization properties while maintaining its physical and chemical integrity without cytotoxic effects.

Biofilm formation mechanisms of mixed antibiotic-resistant bacteria in water: Bacterial interactions and horizontal transfer of antibiotic-resistant plasmids

Over 95 % of bacteria on water supply pipeline surfaces exist in biofilms, which are hotspots for antibiotic resistance gene (ARG) transmission. This study established mixed biofilm culture systems on a metal iron substrate using Escherichia coli: antibiotic-sensitive bacteria (ASB) and antibiotic-resistant bacteria (ARB). The growth rate and extracellular polymeric substances (EPS) content of mixed biofilm surpassed single-species biofilms due to synergistic interactions among different bacteria. However, the composition of mixed biofilms formed by ASB and ARB became unstable after 72 h, linked to reduced polysaccharide proportions in EPS and inter-bacterial competition. The bacterial composition and conjugative transfer frequency of ARGs in mixed biofilms indicate that biofilm formation significantly enhances horizontal transfer of ARGs. Notably, the conjugative transfer frequency of the mixed biofilm formed by two ARB increased 100-fold within five days. In contrast, the conjugative transfer frequency in the mixed biofilm formed by ASB and ARB was unstable; inter-bacterial competition led to plasmid loss associated with horizontal transfer of ARGs, ultimately resulting in biofilm shedding. Furthermore, genes associated with ARG transfer and biofilm growth up-regulated by 1.5 - 6 and 2 - 7 times, respectively, in mixed biofilm. These findings highlight a mutually reinforcing relationship between biofilm formation and horizontal ARG transmission, with significant environmental implications.

Platelet-rich fibrin obtained from different protocols affects the formation of the in vitro multispecies subgingival biofilm associated with periodontitis

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.

Microbial Dynamics in Endodontic Pathology-From Bacterial Infection to Therapeutic Interventions-A Narrative Review

Endodontic infection is a penetration of microorganisms into the dental pulp. Bacteria are the most common entities that induce an infection. This state is associated with significant pain and discomfort. Therapeutic intervention involves removal of infected pulp from the tooth and roots, which eliminates viable tissue, thus creating a tooth less resistant to mechanical pressure. Studies suggest that there are several types of bacteria most commonly associated with endodontic infections. Furthermore, it is considered that different types of pathogens could play a major role in primary and secondary endodontic infections. The aim of this review is to summarize major bacteria involved in the process of endodontic infection. Furthermore, we discuss the bacterial properties that allow them to penetrate dental pulp and hypothesize about possible future treatment strategies.

Unleashing nature's defense: potent antimicrobial power of plant extracts against oral pathogens and Streptococcus mutans biofilms

Objectives

The increasing demand for alternatives to antibiotics against resistant bacteria has led to research on natural products. The aim of this study was to analyze the antimicrobial and antibiofilm activity of 16 Mediterranean herb extracts.

Materials and methods

The extracts were analyzed using High Performance Thin Layer Chromatography. The minimum inhibitory concentration and minimum bactericidal concentration of the extracts from Achillea taygetea, Cistus creticus ssp. creticus, Cistus monspeliensis, Lavandula stoechas, Mentha aquatica, Mentha longifolia, Origanum vulgare, Phlomis cretica, Rosmarinus officinalis, Salvia sclarea, Satureja parnassica, Satureja thymbra, Sideritis euboea, Sideritis syriaca, Stachys spinosa, and Thymus longicaulis were determined against eight oral bacteria and fungus Candida albicans. Microtiter plate test was conducted to evaluate the antibiofilm activity against Streptococcus mutans.

Results

Overall, all tested extracts efficiently suppressed the growth of obligate anaerobic bacteria. When applied at concentrations ≥0.15 mg/ml, the extracts exhibited moderate to high antibiofilm activity comparable to that of chlorhexidine (CHX) against S. mutans. Interestingly, R. officinalis (MIC: 0.01-0.06 mg/ml) and O. vulgare (MIC: 0.04-1.25 mg/ml) demonstrated the highest antibacterial activity against oral bacteria. Additionally, R. officinalis and L. stoechas significantly inhibited S. mutans biofilm formation at 0.15 mg/ml.

Conclusions

The tested plant extracts can be considered as alternative natural antimicrobial and antibiofilm agents.

Clinical relevance

Mediterranean herb extracts show promise as natural alternatives to combat oral bacteria and biofilm formation, offering potential new therapies for infectious oral diseases in the context of antibiotic resistance.

Photodynamic disruption of a polymicrobial biofilm of two periodontal species using indocyanine green-loaded nanospheres

OBJECTIVE

Antimicrobial photodynamic therapy (aPDT) is considered a potential treatment for biofilm infections, which have become an increasing health issue because of the rise in antimicrobial resistance. This study aimed to evaluate the bactericidal effect of aPDT using indocyanine green-loaded nanospheres with chitosan coating (ICG-Nano/c) against polymicrobial periodontal biofilms.

METHODS

Composite biofilms of Porphyromonas gingivalis and Streptococcus gordonii were constructed in 96-well plates, and aPDT with ICG-Nano/c and an 810 nm diode laser was performed either by direct irradiation or transmitting irradiation through a 3-mm-thick gingival model. The efficacy of ICG-Nano/c-based aPDT was compared with antibiotics (minocycline and amoxicillin). Additionally, attenuated aPDT under sublethal conditions was used to investigate gene expression related to the antioxidant response (oxyR and sod of P. gingivalis) and biofilm formation via quorum sensing (luxS of both species) with real-time polymerase chain reaction.

RESULTS

ICG-Nano/c-based aPDT significantly reduced the bacterial load in the biofilm, achieving at least a 2 log10 reduction in colony-forming units within 5 min for both irradiation methods. After 6 h of treatment, the bactericidal effects of aPDT and antibiotics were similar, but after 32 h, antibiotics were more effective, particularly against P. gingivalis. Attenuated aPDT showed a slight increase in sod expression in P. gingivalis, while luxS expression decreased in both bacteria.

CONCLUSION

The ICG-Nano/c-based aPDT system exerted a certain degree of bactericidal activity against a composite biofilm of periodontal bacteria. Therefore, it has potential as an alternative option or adjunctive therapy to conventional antibiotics in periodontal treatment.

The Connection Between the Oral Microbiota and the Kynurenine Pathway: Insights into Oral and Certain Systemic Disorders

The oral microbiome, comprising bacteria, fungi, viruses, and protozoa, is essential for maintaining both oral and systemic health. This complex ecosystem includes over 700 bacterial species, such as Streptococcus mutans, which contributes to dental caries through acid production that demineralizes tooth enamel. Fungi like Candida and pathogens such as Porphyromonas gingivalis are also significant, as they can lead to periodontal diseases through inflammation and destruction of tooth-supporting structures. Dysbiosis, or microbial imbalance, is a key factor in the development of these oral diseases. Understanding the composition and functions of the oral microbiome is vital for creating targeted therapies for these conditions. Additionally, the kynurenine pathway, which processes the amino acid tryptophan, plays a crucial role in immune regulation, neuroprotection, and inflammation. Oral bacteria can metabolize tryptophan, influencing the production of kynurenine, kynurenic acid, and quinolinic acid, thereby affecting the kynurenine system. The balance of microbial species in the oral cavity can impact tryptophan levels and its metabolites. This narrative review aims to explore the relationship between the oral microbiome, oral diseases, and the kynurenine system in relation to certain systemic diseases.

Oral Microbiota Development in the First 60 Months: A Longitudinal Study

Childhood is considered crucial in the establishment of future oral microbiota. However, the precise period of oral microbiota development remains unclear. This study aimed to identify the progression of oral microbiota formation in children. We longitudinally investigated the salivary microbiota of 54 children across 13 time points from 1 wk to 60 mo (5 y) old and their parents at 2 time points as a representative sample of the adult microbiota. Using next-generation sequencing, we obtained 10,000 gene sequences of the 16s rRNA V1-V2 region for each sample. The detection rate in children of 110 operational taxonomic units commonly detected in more than 85% of mothers and fathers, defined as the main constituent bacteria, was 25% at 1 wk old, increased to 80% between 6 and 18 mo old, and reached approximately 90% by 36 mo old. Early main constituent bacteria detected at 1 wk old were limited to Streptococcus, Rothia, and Gemella. At 6 to 18 mo old, the detection rates of various main constituent bacteria, including Neisseria, Haemophilus, and Fusobacterium, increased. UniFrac distance analysis showed that the oral microbiota of children approached that of adults at 6 to 18 mo old. In the weighted UniFrac distance index, unlike the unweighted index, there were no significant changes in children between 36 and 60 mo old from adults, and microbiota formation at 60 mo old was sufficiently advanced to be included within the range of adult individual differences. Our findings suggest that the initial 36 mo, particularly the period from 6 to 18 mo old, consists of a time window for oral microbiota maturation. In addition, the development of microbiota during this period may be critical for future oral disease prevention.

The Impact of Prevotella on Neurobiology in Aging: Deciphering Dendritic Cell Activity and Inflammatory Dynamics

Prevotella species, notably Prevotella copri, significantly populate the human gut. In particular, P. copri is prevalent among non-Western populations with diets high in fiber. These species show complex relationships with diverse health aspects, associating with beneficial outcomes, including reduced visceral fat and improved glucose tolerance. Studies implicate various Prevotella species in specific diseases. Prevotella nigrescens and Porphyromonas gingivalis were linked to periodontal disease, promoting immune responses and influencing T helper type 17 (Th17) cells. Prevotella bivia was associated with bacterial vaginosis and a specific increase in activated cells in the vaginal mucosa. In contrast, they have shown substantial potential for inducing connective tissue degradation and alveolar bone resorption. Prevotella's role in neuroinflammatory disorders and autoinflammatory conditions such as Alzheimer's disease and Parkinson's disease has also been noted. The complex relationship between Prevotella and age-related conditions further extends to neurobiological changes in aging, with varying associations with Alzheimer's, Parkinson's, and other inflammatory conditions. Studies have also identified Prevotella to be implicated in cognitive decline in middle aged and the elderly. Future directions in this research area are anticipated to explore Prevotella-associated inflammatory mechanisms and therapeutic interventions. Investigating specific drug targets and immunomodulatory measures could lead to novel therapeutic strategies. Understanding how Prevotella-induced inflammation interacts with aging diseases would offer promising insights for treatments and interventions. This review urges ongoing research to discover therapeutic targets and mechanisms for moderating Prevotella-associated inflammation to further enhance our understanding and improve health outcomes.

Association of Fusobacterium nucleatum in human saliva with periodontal status and composition of the salivary microbiome including periodontopathogens

Fusobacterium nucleatum promotes dental biofilm formation, increases the prevalence of periodontal disease, and is associated with systemic diseases such as colorectal cancer. However, differences in the composition of salivary microbiome among groups based on the abundance of F. nucleatum are unclear. Therefore, we analyzed the difference in salivary microbiome among groups based on the abundance of F. nucleatum in saliva samples collected from 611 subjects in Japan. Salivary DNA was extracted, and the oral microbiome was analyzed using next-generation sequencing of 16S rRNA. The relationship between F. nucleatum and the community periodontal index was evaluated to examine effects on periodontal status, and α- and β-diversity were analyzed in four groups based on quantiles of relative abundance of F. nucleatum. Spearman rank correlation tests were used to examine relationships between the relative abundance of F. nucleatum and oral bacteria. Subjects with the highest quantiles of F. nucleatum had a higher prevalence of periodontitis compared with those with the lowest quantile. β-Diversity also differed among these four groups. F. nucleatum showed significant correlations with several periodontopathogens, including the red complex, Prevotella intermedia, Filifactor alocis, and Fretibacterium ssp. These results suggest that the relative abundance of F. nucleatum in saliva is associated with periodontal status and the composition of the salivary microbiome, including the red complex and periodontopathogens.

IMPORTANCE

We characterized the composition of the saliva microbiome in groups based on the abundance of Fusobacterium nucleatum. There is a lot of periodontitis in subjects with a high abundance of F. nucleatum. The diversity of the saliva microbiome was different among groups based on the abundance of F. nucleatum. The abundance of F. nucleatum correlated with various periodontopathogens including red complex. These results support the influence of the abundance of F. nucleatum in saliva on periodontal status and the composition of the salivary microbiome, including the red complex and periodontopathogens.

Strategic manipulation of biofilm dispersion for controlling Listeria monocytogenes infections

Listeria monocytogenes (L. monocytogenes), a gram-positive foodborne pathogen that can easily cause listeriosis. It secretes extracellular polymers and forms biofilms that are highly resistant to disinfection methods, such as UV light and germicides, posing risks to food processing equipment and food quality. Dispersion of biofilm is the cycle of its formation in which the bacteria return to planktonic state and become susceptible to antimicrobials, the strategic manipulation of biofilm dispersion is thus heralded as a novel and promising approach for the effective control of biofilm-related infections. Compared to the traditional methods, it is more effective to start with the composition of biofilms, cut off the production of their constituent substances, and genetically reduce the probability of biofilm formation. Meanwhile, the dispersion of bacteria can be supplemented with exogenous substances, making long-term control possible. This paper provides a brief but comprehensive overview of the mechanisms of L. monocytogenes biofilms or cross-contamination and their resistance properties, and facilitates our understanding and control of the prevention and containment of L. monocytogenes biofilm contamination based on the biofilm's active and passive diffusion strategies. This work provides practical guidelines for the food industry to guard against the enduring threat to food safety due to L. monocytogenes biofilms.

Fusobacterium nucleatum dysregulates inflammatory cytokines and NLRP3 inflammasomes in oral cells

OBJECTIVE

This study aimed to clarify the difference in Fusobacterium nucleatum (F. nucleatum) induced inflammatory cytokines and nod-like receptor protein 3 (NLRP3) inflammasomes dysregulation among three periodontal cells.

METHODS

Oral epithelial cells (HIOECs), THP-1 macrophages, and human gingival fibroblasts (HGFs) were exposed to F. nucleatum with/without adenosine triphosphate (ATP) and nigericin (Nig). Cell morphology was assessed by scanning electron microscopy. qRT-PCR, protein microarrays, and bioinformatic methods were used to evaluate the cytokines and their complex interplay. NLRP3 inflammasomes activation was detected by western blotting and ELISA.

RESULTS

F. nucleatum adhered to and invaded cells. In HIOECs, F. nucleatum enhanced interleukin (IL)-1α/1β/6/10/13, TNF-α, and interferon (IFN)-γ expression. In THP-1 macrophages, F. nucleatum up-regulated IL-1α/1β/6/10 and TNF-α levels. In HGFs, F. nucleatum increased IL-6 levels. F. nucleatum and ATP synergistically boosted IFN-γ level in THP-1 macrophages and IL-13 level in HGFs. IL-1α/1β/6, and TNF-α served as epicenters of the inflammatory response. Additionally, F. nucleatum activated NLRP3 inflammasomes in HIOECs, and ATP/Nig boosted the activation. F. nucleatum also triggered NLRP3 inflammasomes in THP-1 macrophages, but in HGFs, only NLRP3 and caspase-1 levels were elevated.

CONCLUSION

F. nucleatum infiltrated periodontal supporting cells and dysregulated inflammatory cytokines and NLRP3 inflammasomes.

Glycolanguage of the oral microbiota

The oral cavity harbors a diverse and dynamic bacterial biofilm community which is pivotal to oral health maintenance and, if turning dysbiotic, can contribute to various diseases. Glycans as unsurpassed carriers of biological information are participating in underlying processes that shape oral health and disease. Bacterial glycoinfrastructure-encompassing compounds as diverse as glycoproteins, lipopolysaccharides (LPSs), cell wall glycopolymers, and exopolysaccharides-is well known to influence bacterial fitness, with direct effects on bacterial physiology, immunogenicity, lifestyle, and interaction and colonization capabilities. Thus, understanding oral bacterias' glycoinfrastructure and encoded glycolanguage is key to elucidating their pathogenicity mechanisms and developing targeted strategies for therapeutic intervention. Driven by their known immunological role, most research in oral glycobiology has been directed onto LPSs, whereas, recently, glycoproteins have been gaining increased interest. This review draws a multifaceted picture of the glycolanguage, with a focus on glycoproteins, manifested in prominent oral bacteria, such as streptococci, Porphyromonas gingivalis, Tannerella forsythia, and Fusobacterium nucleatum. We first define the characteristics of the different glycoconjugate classes and then summarize the current status of knowledge of the structural diversity of glycoconjugates produced by oral bacteria, describe governing biosynthetic pathways, and list biological roles of these energetically costly compounds. Additionally, we highlight emerging research on the unraveling impact of oral glycoinfrastructure on dental caries, periodontitis, and systemic conditions. By integrating current knowledge and identifying knowledge gaps, this review underscores the importance of studying the glycolanguage oral bacteria speak to advance our understanding of oral microbiology and develop novel antimicrobials.

Cocktail Approach with Polyserotonin Nanoparticles and Peptides for Treatment of Streptococcus mutans

Dental plaque, formed by a Streptococcus mutans biofilm, is a major contributor to cavity formation. While antimicrobial strategies exist, the growing risk of antibiotic resistance necessitates alternative therapeutic solutions. Polyserotonin nanoparticles (PSeNPs), recently recognized for their photothermal property and promising biomedical applications, open up a new avenue for antimicrobial use. Here, we introduced a UV-initiated synthetic route for PSeNPs with improved yield. Using these PSeNPs, a cocktail treatment to reduce the viability of this cavity-causing bacteria was developed. This cocktail comprises an S. mutans-targeting antimicrobial peptide (GH12), an intraspecies competence-stimulating peptide that triggers altruistic cell death in S. mutans, and laser-activated heating of PSeNPs. The "peptide + PSeNP + laser" combination effectively inhibits S. mutans growth in both planktonic and biofilm states. Moreover, the cocktail approach remains effective in reducing the viability of S. mutans in a more virulent dual-species biofilm with Candida albicans. Overall, our results reinforce the utility of a multipronged therapeutic strategy to reduce cariogenic bacteria in the complex model oral biofilm.

Microbiological and functional traits of peri-implant mucositis and correlation with disease severity

Osseointegrated dental implants replace missing teeth and create an artificial surface for biofilms of complex microbial communities to grow. These biofilms on implants and dental surfaces can trigger infection and inflammation in the surrounding tissue. This study investigated the microbial characteristics of peri-implant mucositis (PM) and explored the correlation between microbial ecological imbalance, community function, and disease severity by comparing the submucosal microflora from PM with those of healthy inter-subject implants and intra-subject gingivitis (G) within a group of 32 individuals. We analyzed submucosal plaques from PM, healthy implant (HI), and G sites using metagenome shotgun sequencing. The bacterial diversity of HIs was higher than that of PM, according to the Simpson index. Beta diversity revealed differences in taxonomic and functional compositions across the groups. Linear discriminant analysis of the effect size identified 15 genera and 37 species as biomarkers that distinguished PM from HIs. Pathways involving cell motility and protein processing in the endoplasmic reticulum were upregulated in PM, while pathways related to the metabolism of cofactors and vitamins were downregulated. Microbial dysbiosis correlated positively with the severity of clinical inflammation measured by the sulcus bleeding index (SBI) in PM. Prevotella and protein processing in the endoplasmic reticulum also correlated positively with the SBI. Our study revealed PM's microbiological and functional traits and suggested the importance of certain functions in disease severity.IMPORTANCEPeri-implant mucositis is an early stage in the progression of peri-implantitis. The high prevalence of it has been a threat to the widespread use of implant prosthodontics. The link between the submucosal microbiome and peri-implant mucositis was demonstrated previously. Nevertheless, the taxonomic and functional composition of the peri-implant mucositis microbiome remains controversial. In this study, we comprehensively characterize the microbial signature of peri-implant mucositis and for the first time, we investigate the correlations between microbial dysbiosis, functional potential, and disease severity. With the help of metagenomic sequencing, we find the positive correlations between microbial dysbiosis, genus Prevotella, pathway of protein processing in the endoplasmic reticulum, and more severe mucosal bleeding in the peri-implant mucositis. Our studies offer insight into the pathogenesis of peri-implant mucositis by providing information on the relationships between community function and disease severity.

Porphyromonas gingivalis LPS and Actinomyces naeslundii Conditioned Medium Enhance the Release of a Low Molecular Weight, Transcriptionally Active, Fragment of Glycogen Synthase-3 Kinase in IMR-32 Cell Line

Background

Glycogen synthase-3 kinase (GSK3) is one of the major contributors of tau hyperphosphorylation linked to neurofibrillary tangles in Alzheimer's disease (AD).

Objective

To determine a mechanism of GSK-3β activation by two periodontal bacteria consistently confirmed in AD autopsied brains.

Methods

Porphyromonas gingivalis FDC381 and Actinomyces naeslundii ATCC10301 conditioned media were collected. IMR-32 cells were challenged for 48 h with the conditioned media alongside P. gingivalis (ATCC33277) ultrapurified lipopolysaccharide (LPS) designated Pg.LPS under established cell culture conditions either alone or combined. Gene expression and protein analyses for GSK-3β were carried out.

Results

qPCR demonstrated that GSK-3β gene was overexpressed in IMR-32 cells treated with Pg.LPS with a 2.09-fold change (p = 0.0005), while A. naeslundii treated cells demonstrated 1.41-fold change (p = 0.004). Western blotting of the cells challenged with Pg.LPS (p = 0.01) and A. naeslundii conditioned medium (p = 0.001) demonstrated the 37 kDa band for each treatment with variable intensity across the medium control. Immunohistochemistry with the GSK-3β of the IMR-32 cells challenged with Pg.LPS and A. naeslundii alone demonstrated cytoplasmic and nuclear localization.

Conclusions

Exposure to various bacterial factors upregulated the gene expression of GSK-3β. Western blotting for GSK-3β confirmed the presence of the cleaved fragment by Pg.LPS (37 kDa band p = 0.01) and A. naeslundii conditioned medium (37 kDa band p = 0.001). Immunostaining demonstrated both cytoplasmic and nuclear localization of GSK-3β. Therefore, Pg.LPS and an unknown factor from the A. naeslundii conditioned medium mediated GSK-3β activation via its transcriptionally active, cleaved, fragment. These virulence factors in the body appear to be detrimental to brain health.

Aggregatibacter actinomycetemcomitans: From the Oral Cavity to the Heart Valves

Aggregatibacter actinomycetemcomitans (A. actinomycetecomitans) is a Gram-negative bacterial species that is an essential component of the oral microbiota. Due to its aggregative properties, it plays a role in the pathogenesis of human diseases. The presence of the surface proteins Fim, Briae, and microvesicles enables the bacterium to adhere to the epithelial surface and the tooth's surface. The presence of leukotoxin A (LtxA), which plays an important role in the pathogenicity of the bacterium, has been associated with both periodontitis and the etiology of rheumatoid arthritis (RA). A. actinomycetecomitans is also associated with several other systemic diseases and complications, such as endocarditis and different abscesses. In addition to leukotoxin A, A. actinomycetecomitans possesses several different virulence factors, including bacteriocins, chemotaxis inhibitory factors, cytotoxic factors, Fc-binding proteins, immunosuppressive factors, lipopolysaccharide collagenase, fibroblast inhibitory factors, antibiotic resistance determinants, adhesins, invasive factors and factors that inhibit the function of polymorphonuclear leukocytes. The ability of A. actinomycetemcomitans lipopolysaccharide to induce macrophages to secrete the interleukins IL-1, IL-1β, and tumor necrosis factor (TNF) is of considerable importance. The primary etiologic factor in the pathogenesis of periodontal disease is the oral biofilm colonized by anaerobic bacteria. Among these, A. actinomycetemcomitans occupies an important place as a facultative anaerobic bacterium. In addition, A. actinomycetemcomitans possesses many virulence factors that contribute to its potential to cause cancer. This article provides an overview of the virulence factors of A. actinomycetecomitans and its association with various systemic diseases, its oncogenic potential, and the treatment options for infections caused by A. actinomycetecomitans.

Identification of keystone taxa in root canals and periapical lesions of post-treatment endodontic infections: Next generation microbiome research

AIM

The aim of this study was to analyse and compare the microbiome present in root canals and periapical lesions of teeth with post-treatment infections, and to identify the presence of keystone taxa in both habitats using next-generation sequencing analysis.

METHODOLOGY

Apices and periapical lesions of patients with post-treatment apical periodontitis were surgically extracted. Specimens were cryo-pulverized, bacterial DNA was extracted, and the V3-V4 hypervariable regions of the 16S rRNA gene were sequenced using the Illumina Miseq platform. Bioinformatic analysis was carried out with Mothur software, whilst diversity indices were obtained using operational taxonomic units (OTUs). The diversity indices were compared with the Kruskal-Wallis test, and community composition differences were explored with Permutational Multivariate Analysis of Variance (PERMANOVA). A bacterial functional study was performed with the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis. Co-occurrence network analyses were performed using the Sparse Correlations for Compositional data (SparCC). Eigencentrality, clr-based abundance and ubiquitousness were applied to infer keystone taxa. P values <.05 were considered statistically significant.

RESULTS

Thirty-two apices and thirty-nine periapical lesions were sequenced and analysed. A similar alpha-diversity (p < .05) and community composition (p = .91) was observed for apices and lesion samples. The most abundant OTUs identified amongst all samples included Fusobacterium nucleatum, Prevotella loescheii, Streptococcus intermedius, Porphyromonas gingivalis, Parvimonas micra, Synergistetes bacterium, Tannerella forsythia and Peptostreptococcus stomatis. The metabolic pathways with >0.81% abundances included membrane transport, genetic information processing and metabolic pathways. F. nucleatum was identified as a keystone taxon as it showed ubiquitousness, an eigenvector centrality value of 0.83 and a clr-based abundance >4.

CONCLUSIONS

The microbiome in apices and periapical lesions of post-treatment endodontic infections showed a similar diversity and taxonomic composition. Co-occurrence network analyses at OTU level identified F. nucleatum as a keystone taxon candidate in these infections.

Commensalism of Fusobacterium nucleatum - The dilemma

Fusobacterium nucleatum is a Gram-negative, anaerobic bacterium that serves as a periodontal pathogen and plays a key role in linking Gram-positive and Gram-negative bacteria within the periodontal biofilm. It was shown that Fusobacterium produces significant amounts of butyric acid, which is a great source of energy for anti-inflammatory cells. On the other hand, it is associated with the destruction of periodontal structures. This bacterium can enter the blood circulation as a result of periodontal infection. It could cause numerous conditions such as halitosis, dental pulp infection, oral cancer, and systemic diseases. The present review discusses the virulence mechanisms involved in the diseases, with emphasis on its colonization, systemic dissemination, and induction of host inflammatory and tumorigenic responses. This would motivate future research on the role of this bacterium on periodontal pathology as well as its influence on the evolution of systemic diseases.

Antibacterial activities of phytochemicals against Porphyromonas gingivalis with and without experimental fluoride varnish for periodontal disease prevention

We aimed to evaluate the antibacterial activity of phytochemicals with or without an experimental fluoride varnish against Porphyromonas gingivalis. Five phytochemicals, chrysophanol (CHR), emodin (EMO), anthrarufin (ANT), bavachalcone (BCC), and isobavachromene (IBC), were tested using agar diffusion, minimal inhibition concentration (MIC), and minimum bacterial concentration (MBC) assays. We also assessed the cell viability and cytotoxicity of phytochemicals. All phytochemicals showed clear inhibition zones in the agar diffusion test. The inhibition zones of all phytochemical-containing fluoride varnishes were similar to or larger than that of the positive control, excluding that of 1 mM EMO. With or without the fluoride varnish, BCC exhibited the lowest MIC and MBC levels. Cell viability was high in the presence of all phytochemicals except 200 μM EMO. In conclusion, BCC was most effective as a phytochemical alone, while all phytochemical-containing fluoride varnishes inhibited P. gingivalis growth without cytotoxicity.

Combination of Neovestitol and Vestitol Modifies the Profile of Periodontitis-Related Subgingival Multispecies Biofilm

The aim of this study was to evaluate the effect of the combination of neovestitol-vestitol (CNV) compounds obtained from Brazilian red propolis on the microbiological profile of a mature multispecies subgingival biofilm. The biofilm with 32 bacterial species associated with periodontitis was formed for seven days using a Calgary device. Treatment with CNV (1600, 800, 400, and 200 μg/mL), amoxicillin (54 μg/mL), and vehicle control was performed for 24 h on the last day of biofilm formation. Biofilm metabolic activity and DNA-DNA hybridization (checkerboard) assays were performed. The groups treated with CNV 1600 and amoxicillin reduced 25 and 13 species, respectively, compared to the control vehicle treatment (p ≤ 0.05); both reduced P. gingivalis, while only CNV reduced T. forsythia. When the data from the two treatments (CNV and AMOXI) were compared, a statistically significant difference was observed in 13 species, particularly members of Socransky's orange complex. Our results showed that CNV at 1600 μg/mL showed the best results regarding the metabolic activity of mature biofilms and obtained a reduction in species associated with the disease, such as T. forsythia, showing a better reduction than amoxicillin. Therefore, CNV seems to be a promising alternative to eradicate biofilms and reduce their pathogenicity.

Coaggregated E. faecalis with F. nucleatum regulated environmental stress responses and inflammatory effects

To investigate the cell-cell interactions of intergeneric bacterial species, the study detected the survival of Enterococcus faecalis (Ef) under monospecies or coaggregation state with Fusobacterium nucleatum subsp. polymorphum (Fnp) in environmental stress. Ef and Fnp infected the human macrophages with different forms (Ef and Fnp monospecies, Ef-Fnp coaggregates, Ef + Fnp cocultures) for exploring the immunoregulatory effects and the relevant molecular mechanisms. Meanwhile, the transcriptomic profiles of coaggregated Ef and Fnp were analyzed. Ef was shown to coaggregate with Fnp strongly in CAB within 90 min by forming multiplexes clumps. Coaggregation with Fnp reinforced Ef resistance against unfavorable conditions including alkaline, hypertonic, nutrient-starvation, and antibiotic challenges. Compared with monospecies and coculture species, the coaggregation of Ef and Fnp significantly facilitates both species to invade dTHP-1 cells and aid Ef to survive within the cells. Compared with coculture species, dual-species interaction of Ef and Fnp significantly decreased the levels of pro-inflammatory cytokines IL-6, TNF-α, and chemokines MCP-1 secreted by dTHP-1 cells and lessened the phosphorylation of p38, JNK, and p65 signaling pathways. The transcriptome sequencing results showed that 111 genes were differentially expressed or Ef-Fnp coaggregated species compared to Ef monospecies; 651 genes were differentially expressed for Fnp when coaggregation with Ef. The analysis of KEGG pathway showed that Ef differentially expressed genes (DEGs) were enriched in quorum sensing and arginine biosynthesis pathway; Fnp DEGs were differentially concentrated in lipopolysaccharide (LPS) biosynthesis, biofilm formation, and lysine degradation pathway compared to monospecies. KEY POINTS: • Coaggregated with Fnp aids Ef's survival in environmental stress, especially in root canals after endodontic treatment. • The coaggregation of Ef and Fnp may weaken the pro-inflammatory response and facilitate Ef to evade killed by macrophages. • The coaggregation between Ef and Fnp altered interspecies transcriptional profiles.

Investigation of a novel biofilm model close to the original oral microbiome

A more optimized culture medium used in vitro to mimic the bacterial composition of original oral flora as similar as possible remains difficult at present, and the goal of this study is to develop a novel oral biofilm medium to restore the original oral microbiome. Firstly, we conducted a systematic literature review by searching PubMed and summarized the current reported culture media in vitro. Seven culture media were found. We used mixed saliva as the origin of oral species to compare the effects of the above media in culturing oral multispecies biofilms. Results indicated that among the seven media brain heart infusion containing 1% sucrose (BHIs) medium, PG medium, artificial saliva (AS) medium, and SHI medium could obviously gain large oral biofilm in vitro. The nutrients contained in different culture media may be suitable for the growth of different oral bacteria; therefore, we optimized several novel media accordingly. Notably, results of crystal violet staining showed that the biofilm cultured in our modified artificial saliva (MAS) medium had the highest amount of biofilm biomass. 16S rRNA gene sequencing showed that the operational taxonomic units (OTUs) and Shannon index of biofilm cultured in MAS medium were also the highest among all the tested media. More importantly, the 16S rRNA gene sequencing analysis indicated that the biofilm cultured in MAS medium was closer to the original saliva species. Besides, biofilm cultured by MAS was denser and produced more exopolysaccharides. MAS supported stable biofilm formation on different substrata. In conclusion, this study demonstrated a novel MAS medium that could culture oral biofilm in vitro closer to the original oral microbiome, showing a good application prospect. KEY POINTS: • We compare the effects of different media in culturing oral biofilms • A novel modified artificial saliva (MAS) medium was obtained in our study • The MAS medium could culture biofilm that was closer to oral microbiome.

Fusobacterium nucleatum mechanism of action in alveolar bone destruction: Scoping review

Fusobacterium nucleatum is implicated in periodontitis, a chronic inflammatory disease that destroys the periodontal tissue and alveolar bone due to host-microbe dysbiosis. This study focuses on understanding how F. nucleatum contributes to bone destruction in periodontitis. The literature search was conducted using PubMed and Scopus databases based on Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines by entering preselected keyword combinations of inclusion and exclusion criteria. Qualifying literature was evaluated based on four inclusion criteria: research articles, published in English, within the last ten years, and available in full text. The literature search yielded five articles exploring the mechanism of bone resorption by F. nucleatum. It was found that the bacteria increases the production of inflammatory mediators, such as interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-alpha, C-C motif chemokine ligand (CCL) 2, CCL20, and C-X-C motif chemokine ligand 1, which leads to the destruction of alveolar bone. During infection, biomechanical stress also raises levels of prostaglandin E2 and cyclooxygenase-2. The elevated levels of inflammatory mediators and enzymes generate an imbalance in the receptor activator of nuclear factor kappa-B ligand to osteoprotegerin ratio, hindering osteogenic differentiation and heightening bone destruction. In conclusion, F. nucleatum infection promotes alveolar bone destruction by inducing inflammatory responses and inhibiting osteogenic differentiation stimulated by biomechanical loading. More research is essential to explore the connection between F. nucleatum virulence and its alveolar bone degradation mechanisms.

Transcriptome fine-mapping in Fusobacterium nucleatum reveals FoxJ, a new σE-dependent small RNA with unusual mRNA activation activity

The oral commensal Fusobacterium nucleatum can spread to extra-oral sites, where it is associated with diverse pathologies, including pre-term birth and cancer. Due to the evolutionary distance of F. nucleatum to other model bacteria, we lack a deeper understanding of the RNA regulatory networks that allow this bacterium to adapt to its various niches. As a first step in that direction, we recently showed that F. nucleatum harbors a global stress response governed by the extracytoplasmic function sigma factor, σE, which displays a striking functional conservation with Proteobacteria and includes a noncoding arm in the form of a regulatory small RNA (sRNA), FoxI. To search for putative additional σE-dependent sRNAs, we comprehensively mapped the 5' and 3' ends of transcripts in the model strain ATCC 23726. This enabled the discovery of FoxJ, a ~156-nucleotide sRNA previously misannotated as the 5' untranslated region (UTR) of ylmH. FoxJ is tightly controlled by σE and activated by the same stress conditions as is FoxI. Both sRNAs act as mRNA repressors of the abundant porin FomA, but FoxJ also regulates genes that are distinct from the target suite of FoxI. Moreover, FoxJ differs from other σE-dependent sRNAs in that it also positively regulates genes at the post-transcriptional level. We provide preliminary evidence for a new mode of sRNA-mediated mRNA activation, which involves the targeting of intra-operonic terminators. Overall, our study provides an important resource through the comprehensive annotation of 5' and 3' UTRs in F. nucleatum and expands our understanding of the σE response in this evolutionarily distant bacterium.IMPORTANCEThe oral microbe Fusobacterium nucleatum can colonize secondary sites, including cancer tissue, and likely deploys complex regulatory systems to adapt to these new environments. These systems are largely unknown, partly due to the phylogenetic distance of F. nucleatum to other model organisms. Previously, we identified a global stress response mediated by σE that displays functional conservation with the envelope stress response in Proteobacteria, comprising a coding and noncoding regulatory arm. Through global identification of transcriptional start and stop sites, we uncovered the small RNA (sRNA) FoxJ as a novel component of the noncoding arm of the σE response in F. nucleatum. Together with its companion sRNA FoxI, FoxJ post-transcriptionally modulates the synthesis of envelope proteins, revealing a conserved function for σE-dependent sRNAs between Fusobacteriota and Proteobacteria. Moreover, FoxJ activates the gene expression for several targets, which is a mode of regulation previously unseen in the noncoding arm of the σE response.

Promising dawn in tumor microenvironment therapy: engineering oral bacteria

Despite decades of research, cancer continues to be a major global health concern. The human mouth appears to be a multiplicity of local environments communicating with other organs and causing diseases via microbes. Nowadays, the role of oral microbes in the development and progression of cancer has received increasing scrutiny. At the same time, bioengineering technology and nanotechnology is growing rapidly, in which the physiological activities of natural bacteria are modified to improve the therapeutic efficiency of cancers. These engineered bacteria were transformed to achieve directed genetic reprogramming, selective functional reorganization and precise control. In contrast to endotoxins produced by typical genetically modified bacteria, oral flora exhibits favorable biosafety characteristics. To outline the current cognitions upon oral microbes, engineered microbes and human cancers, related literatures were searched and reviewed based on the PubMed database. We focused on a number of oral microbes and related mechanisms associated with the tumor microenvironment, which involve in cancer occurrence and development. Whether engineering oral bacteria can be a possible application of cancer therapy is worth consideration. A deeper understanding of the relationship between engineered oral bacteria and cancer therapy may enhance our knowledge of tumor pathogenesis thus providing new insights and strategies for cancer prevention and treatment.

Isolation, characterization of Weissella confusa and Lactococcus lactis from different milk sources and determination of probiotic features

This study aimed to investigate the probiotic properties of Lactic Acid Bacteria (LAB) isolates derived from various milk sources. These isolates identified based on their morphological characteristics and 16S rRNA gene sequencing. Four strains of Lactococcus lactis and two strains of Weissella confusa were identified with over 96% 16S rRNA gene similarity according to the NCBI-BLAST results. The survival of the isolates was determined in low pH, pepsin, bile salts, and pancreatin, and their adhesion ability was assessed by in vitro cell adhesion assay, hydrophobicity, auto- and co-aggregation, and safety criteria were determined by hemolytic, gelatinase activities, and DNAse production ability tests. The results showed that the LAB isolates had different levels of resistance to various stress factors. L. lactis subsp. cremoris MH31 showed the highest resistance to bile salt, while the highest pH resistance was observed in L. lactis MH31 at pH 3.0. All the isolates survived in pepsin exposure at pH 3.0 for 3 h. The auto-aggregation test results showed that all strains exhibited auto-aggregation ranging from 84.9 to 91.4%. Co-aggregation percentage ranged from 19 - 54% and 17 - 57% against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, respectively. The hydrophobicity capacity of the LAB isolated ranged from 35-61%. These isolates showed different adhesion abilities to Caco-2 cells (81.5% to 92.6%). None of the isolates exhibited DNase, gelatinase and hemolytic activity (γ-hemolysis). All results indicate that these LAB strains have the potential to be used as probiotics.

Acquired Pellicle and Biofilm Engineering by Rinsing with Hemoglobin Solution

INTRODUCTION

The identification of acid-resistant proteins, including hemoglobin (Hb), within the acquired enamel pellicle (AEP) led to the proposition of the "acquired pellicle engineering" concept, which involves the modification of the AEP by incorporating specific proteins, presenting a novel strategy to prevent dental demineralization.

OBJECTIVE

Combining in vivo and in vitro proof-of-concept protocols, we sought to reveal the impact of AEP engineering with Hb protein on the biofilm microbiome and enamel demineralization.

METHODS

In the in vivo studies, 10 volunteers, in 2 independent experiments, rinsed (10 mL,1 min) with deionized water-negative control or 1.0 mg/mL Hb. The AEP and biofilm formed along 2 or 3 h, respectively, were collected. AEP was analyzed by quantitative shotgun-label-free proteomics and biofilm by 16S-rRNA next-generation sequencing (NGS). In in vitro study, a microcosm biofilm protocol was employed. Seventy-two bovine enamel specimens were treated with (1) phosphate-buffered solution (PBS), (2) 0.12% chlorhexidine, (3) 500 ppm NaF, (4) 1.0 mg/mL Hb, (5) 2.0 mg/mL Hb, and (6) 4.0 mg/mL Hb. The biofilm was cultivated for 5 days. Resazurin, colony forming units (CFU), and transversal microradiography were performed.

RESULTS

Proteomics and NGS analysis revealed that Hb increased proteins with antioxidant, antimicrobial, acid-resistance, hydroxyapatite-affinity, calcium-binding properties and showed a reduction in oral pathogenic bacteria. In vitro experiments demonstrated that the lowest Hb concentration was the most effective in reducing bacterial activity, CFU, and enamel demineralization compared to PBS.

CONCLUSION

These findings suggest that Hb could be incorporated into anticaries dental products to modify the oral microbiome and control caries, highlighting its potential for AEP and biofilm microbiome engineering.

Interfacial morphodynamics of proliferating microbial communities

In microbial communities, various cell types often coexist by occupying distinct spatial domains. What determines the shape of the interface between such domains-which in turn influences the interactions between cells and overall community function? Here, we address this question by developing a continuum model of a 2D spatially-structured microbial community with two distinct cell types. We find that, depending on the balance of the different cell proliferation rates and substrate friction coefficients, the interface between domains is either stable and smooth, or unstable and develops finger-like protrusions. We establish quantitative principles describing when these different interfacial behaviors arise, and find good agreement both with the results of previous experimental reports as well as new experiments performed here. Our work thus helps to provide a biophysical basis for understanding the interfacial morphodynamics of proliferating microbial communities, as well as a broader range of proliferating active systems.

Hypochlorous Acid as a Potential Postsurgical Antimicrobial Agent in Periodontitis: A Randomized, Controlled, Non-Inferiority Trial

BACKGROUND

Hypochlorous acid (HOCl) is an antimicrobial agent with high affinity to Gram-negative bacteria of the subgingival biofilm. It could have an equivalent or no inferiority effect to chlorhexidine (CHX) to avoid recolonization of these microorganisms after the post-surgical period.

OBJECTIVE

The objective is to compare the reduction of plaque index (PI), gingival index (GI), pocket depth (PD), gain of clinical attachment level (CAL), and bacterial recolonization of periodontopathic microorganisms in subgingival biofilm at 7, 21, and 90 days after Open Flap Debridement (OFD) under two antimicrobial protocols: (A) HOCl 0.05% followed by HOCl 0.025% and (B) CHX 0.2%/CHX 0.12% used per 21 days without regular oral hygiene during the post-surgical period.

MATERIAL AND METHODS

A no-inferiority randomized controlled trial was carried out. Thirty-two patients were randomly divided to receive each antiplaque protocol after OFD in patients with periodontitis. Clinical indexes and bacterial recolonization were assessed using qPCR for up to 90 days. Data were analyzed using repeated measures ANOVA, mixed effects models adjusted for treatment, time, and the Chi-squared/Fisher test. A no-inferiority analysis was also performed using the Hodges-Lehmann hypothesis test for non-inferiority.

RESULTS

HOCl was not inferior to CHX in reducing PI. Both groups showed a comparable reduction of recolonization for Porphyromonas gingivalis, Tannerella forsythia, and Eubacterium nodatum. However, the HOCl protocol was non-inferior to the CHX protocol for Treponema denticola and Aggregatibacter actinomicetemcomitans.

CONCLUSIONS

HOCl improved periodontal healing. HOCl showed an impact in reducing the recolonization of periodontopathic bacteria in the postoperative period.

Lactobacillus acidophilus impairs the establishment of pathogens in a subgingival multispecies biofilm

The present study evaluated the antibiofilm effects of Lactobacillus acidophilus within a subgingival multispecies biofilm. Lactobacillus acidophilus (La5) at 1 × 102, 1 × 104, and 1 × 106 were included at the beginning of biofilm formation, which lasted 7 days. The biofilms comprised 33 periodontitis-related bacterial species and the Calgary Biofilm device was used. At the end, DNA-DNA hybridization (checkerboard) was performed. A Kruskal-Wallis test followed by a Dunn post hoc test were performed (p ≤ 0.05). La5 at 1 × 104 and 1 × 106 reduced the total counts of biofilm and the proportions of red and green complexes when compared to the control biofilm without La5 (p ≤ 0.05). La5 at 1 × 104 increased the proportions of Actinomyces complex compared to the controls (p ≤ 0.05). Both La5 at 1 × 104 and 1 × 106 decreased levels of 20 and 14 distinct species, respectively, including Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum polymorphum, and Parvimonas micra compared to the control (p ≤ 0.05). Only La5 at 1 × 104 reduced the levels of Tannerella forsythia, Fusobacterium periodonticum, and Aggregatibacter actinomycetencomytans compared to the control (p ≤ 0.05). L. acidophilus inhibited establishing periodontic pathogens from red complex such as P. gingivalis and T. forsythia in a subgingival multispecies biofilm.

Numerical and experimental investigation of multi-species bacterial co-aggregation

This paper deals with the mathematical modeling of bacterial co-aggregation and its numerical implementation in a FEM framework. Since the concept of co-aggregation refers to the physical binding between cells of different microbial species, a system composed of two species is considered in the modeling framework. The extension of the model to an arbitrary number of species is straightforward. In addition to two-species (multi-species growth) dynamics, the transport of a nutritional substance and the extent of co-aggregation are introduced into the model as the third and fourth primary variables. A phase-field modeling approach is employed to describe the co-aggregation between the two species. The mathematical model is three-dimensional and fully based on the continuum description of the problem without any need for discrete agents which are the key elements of the individual-based modeling approach. It is shown that the use of a phase-field-based model is equivalent to a particular form of classical diffusion-reaction systems. Unlike the so-called mixture models, the evolution of each component of the multi-species system is captured thanks to the inherent capability of phase-field modeling in treating systems consisting of distinct multi-phases. The details of numerical implementation in a FEM framework are also presented. Indeed, a new multi-field user element is developed and implemented in ANSYS for this multiphysics problem. Predictions of the model are compared with the experimental observations. By that, the versatility and applicability of the model and the numerical tool are well established.

Hydrogel-Encapsulated Biofilm Inhibitors Abrogate the Cariogenic Activity of Streptococcus mutans

We designed and synthesized analogues of a previously identified biofilm inhibitor IIIC5 to improve solubility, retain inhibitory activities, and to facilitate encapsulation into pH-responsive hydrogel microparticles. The optimized lead compound HA5 showed improved solubility of 120.09 μg/mL, inhibited Streptococcus mutans biofilm with an IC50 value of 6.42 μM, and did not affect the growth of oral commensal species up to a 15-fold higher concentration. The cocrystal structure of HA5 with GtfB catalytic domain determined at 2.35 Å resolution revealed its active site interactions. The ability of HA5 to inhibit S. mutans Gtfs and to reduce glucan production has been demonstrated. The hydrogel-encapsulated biofilm inhibitor (HEBI), generated by encapsulating HA5 in hydrogel, selectively inhibited S. mutans biofilms like HA5. Treatment of S. mutans-infected rats with HA5 or HEBI resulted in a significant reduction in buccal, sulcal, and proximal dental caries compared to untreated, infected rats.

Effect of anaerobic or/and microaerophilic atmosphere on microcosm biofilm formation and tooth demineralization

OBJECTIVE

Microcosm biofilms can reproduce the complexity of a dental biofilm. However, different forms of cultivation have been used. The impact of the culture atmosphere on the development of microcosm biofilms and their potential to cause tooth demineralization has not yet been deeply studied. This study analyzes the effects of three experimental cultivation models (microaerophile vs. anaerobiosis vs. experimental mixed) on the colony-forming units (CFU) of the cariogenic microorganisms and tooth demineralization.

METHODOLOGY

90 bovine enamel and 90 dentin specimens were distributed into different atmospheres: 1) microaerophilia (5 days, 5% CO2); 2) anaerobiosis (5 days, jar); 3) mixed (2 days microaerophilia and 3 days anaerobiosis), which were treated with 0.12% chlorhexidine (positive control - CHX) or Phosphate-Buffered Saline (negative control - PBS) (n=15). Human saliva and McBain's saliva containing 0.2% sucrose were used for microcosm biofilm formation, for 5 days. From the second day to the end of the experiment, the specimens were treated with CHX or PBS (1x1 min/day). Colony-forming units (CFU) were counted, and tooth demineralization was analyzed using transverse microradiography (TMR). Data were subjected to two-way ANOVA and Tukey's or Sidak's test (p<0.05).

RESULTS

CHX was able to reduce total microorganism's CFU compared to PBS (differences of 0.3-1.48 log10 CFU/mL), except for anaerobiosis and microaerophilia in enamel and dentin biofilm, respectively. In the case of dentin, no effect of CHX on Lactobacillus spp. was observed. CHX significantly reduced enamel demineralization compared to PBS (78% and 22% reductions for enamel and dentin, respectively). Enamel mineral loss did not differ when compared with the other atmospheres; however, the enamel lesion depth was greater under anaerobiosis. Dentin mineral loss was lower under anaerobiosis when compared with the other atmospheres.

CONCLUSION

The type of atmosphere has, in general, little influence on the cariogenic ability of the microcosm biofilm.

Antibacterial and Antibiofilm Efficacy of Copper-Doped Phosphate Glass on Pathogenic Bacteria

This study aimed to investigate the antibacterial [minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC)] and antibiofilm activity [log10 colony forming unit/mL (CFU/mL) and biofilm disruption] of copper-doped phosphate glass (CDPG) against Streptococcus oralis, Enterococcus faecalis, Lactobacillus casei, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Methods: the antibacterial activity was determined using microbroth dilution and time-kill assay. The antibiofilm activity was investigated using crystal violet and confocal laser scanning microscopy. Bacteria growing in absence of CDPG were used as controls. Results: the MIC was ≥125 mg of CPDG/mL; the log10 CFU/mL reduction ranged from 2.66–3.14 to 6.23–9.65 after 4 and 24 h respectively. Generally, no growth was observed after 24 h of treatment with CDPG; the MBC was 250 mg/mL for L. casei and S. oralis while 500 mg/mL for the rest of the bacteria. The highest and lowest antibiofilm activity was observed against S. oralis and E. coli respectively. Three patterns of complete biofilm disruption were seen: (i) large areas with E. fecalis and S. oralis, (ii) medium-size pockets with S. aureus and P. aeruginosa, or (iii) small areas with E. coli and L. casei. Conclusion: CDPG can be potentially used as an antibacterial and an antibiofilm agent against oral biofilm-forming bacteria.

Role of cathepsin D induced by Porphyromonas gingivalis lipopolysaccharide in periodontitis

Periodontitis is an inflammatory disease of tooth-supporting tissues caused by oral bacteria. Periodontal ligament loss and alveolar bone destruction occur in progressive periodontitis. Since gingival crevicular fluids (GCF) reflects the inflammatory environment of the periodontal pocket, it is a very important specimen for developing targets for periodontitis diagnosis. An antibody array was performed using GCF collected from healthy participants and patients with periodontitis to identify the proteolytic enzymes involved in periodontitis. Of 21 targets on the antibody array membrane, kallikrein 6 (KLK6), kallikrein 10 (KLK10), cathepsin A (CathA), and cathepsin D (CathD) showed higher levels in periodontitis GCF than in GCF from healthy participants. Lipopolysaccharide stimulation of Porphyromonas gingivalis (PG-LPS) in immortalized gingival fibroblasts only increased CathD protein levels among the four targets. The substrate cleavage activity of CathD was increased in PG-LPS-treated immortalized gingival fibroblast extract. The PG-LPS-induced substrate cleavage effect was abolished by the CathD inhibitor pepstatin A. Osteoclast formation was promoted by treatment with conditioned media from PG-LPS- treated immortalized gingival fibroblasts but inhibited by the CathD inhibitor pepstatin A. These results suggest that PG-LPS affected the osteoclast formation process by increasing CathD expression in cells around the alveolar bone, thereby participating in periodontitis progression.

Fusobacterium nucleatum, a key pathogenic factor and microbial biomarker for colorectal cancer

Colorectal cancer (CRC), one of the most prevalent cancers, has complex etiology. The dysbiosis of intestinal bacteria has been highlighted as an important contributor to CRC. Fusobacterium nucleatum, an oral anaerobic opportunistic pathogen, is enriched in both stools and tumor tissues of patients with CRC. Therefore, F. nucleatum is considered to be a risk factor for CRC. This review summarizes the biological characteristics and the mechanisms underlying the regulatory behavior of F. nucleatum in the tumorigenesis and progression of CRC. F. nucleatum as a marker for the early warning and prognostic prediction of CRC, and as a target for prevention and treatment, is also described.

Improvement of halitosis by probiotic bacterium Weissella cibaria CMU: A randomized controlled trial

Several in vitro and in vivo studies have evaluated the effect of probiotics on oral health; however, human clinical studies are still limited. Therefore, this study aimed to examine the effects of Weissella cibaria Chonnam Medical University (CMU)-containing tablets on halitosis. This randomized, double-blinded, placebo-controlled study included 100 adults with halitosis (age, 20-70 years). The participants were randomly assigned to the test group (n = 50) and control group (n = 50). One tablet [1 × 10⁸ colony forming units (CFU)/tablet] was to be taken each day over 8 weeks. The concentrations of volatile sulfur compounds (VSCs), bad breath improvement scores, and oral colonization of W. cibaria were measured. Psychosocial indicators including depression, self-esteem, oral health-related quality of life, and subjective oral health status were evaluated. Most variables were assessed at baseline, 4, and 8 weeks, and W. cibaria number and safety variables were assessed at baseline and 8 weeks. Intergroup comparisons were carried out using Student's t-test, Chi-square test, or Fisher's exact test on per-protocol analysis. Intragroup differences before and after intake were analyzed using the linear mixed-effect model (LMM). Per-protocol analysis was carried out in the test group (n = 45) and control group (n = 46). Total VSC was significantly lower in the probiotics group than in the placebo group at baseline (week 0, p = 0.046) and at 8 weeks (p = 0.017). The sum of hydrogen sulfide and methyl mercaptan did not differ significantly between the groups at baseline; however, it was significantly lower in the probiotics group than in the placebo group at week 8 (p = 0.012). Bad breath improvement (BBI) scores were significantly reduced at week 8 (p = 0.006) in the probiotics group. Statistically significant intergroup differences were observed for changes in the level of W. cibaria at week 8 (p < 0.001). Psychological indicators significantly improved from baseline to week 8 in the probiotics group. No safety issues were observed in either group. The levels of W. cibaria was higher in patients with halitosis using W. cibaria CMU-containing tablets. The subjective degree of bad breath and psychological indicators were improved in patients with halitosis using W. cibaria CMU-containing tablets.

Uncovering the link between the SpnIII restriction modification system and LuxS in Streptococcus pneumoniae meningitis isolates

Streptococcus pneumoniae is capable of randomly switching their genomic DNA methylation pattern between six distinct bacterial subpopulations (A-F) via recombination of a type 1 restriction-modification locus, spnIII. These pneumococcal subpopulations exhibit phenotypic changes which favor carriage or invasive disease. In particular, the spnIIIB allele has been associated with increased nasopharyngeal carriage and the downregulation of the luxS gene. The LuxS/AI-2 QS system represent a universal language for bacteria and has been linked to virulence and biofilm formation in S. pneumoniae. In this work, we have explored the link between spnIII alleles, the luxS gene and virulence in two clinical pneumococcal isolates from the blood and cerebrospinal fluid (CSF) of one pediatric meningitis patient. The blood and CSF strains showed different virulence profiles in mice. Analysis of the spnIII system of these strains recovered from the murine nasopharynx showed that the system switched to different alleles commensurate with the initial source of the isolate. Of note, the blood strain showed high expression of spnIIIB allele, previously linked with less LuxS protein production. Importantly, strains with deleted luxS displayed different phenotypic profiles compared to the wildtype, but similar to the strains recovered from the nasopharynx of infected mice. This study used clinically relevant S. pneumoniae strains to demonstrate that the regulatory network between luxS and the type 1 restriction-modification system play a key role in infections and may support different adaptation to specific host niches.

Adhesion of Yeast and Bacteria to Oral Surfaces

Colonization of surfaces in the human body by microorganisms is an early, essential, step in the initiation of infectious disease. We have developed in vitro assays to investigate interactions between yeast or bacterial cells and human tissues, fluids, or prostheses. Such assays can be used to identify the adhesins, ligands, and receptors involved in these interactions, for example, by determining which components of the microbe or human tissue/fluid interfere with adherence in the assay. The assays can also be applied to find ways of preventing adhesion, and subsequent disease, by investigating the effects of different conditions and added compounds on adherence in the in vitro assays. Here we describe assays for measuring adhesion of the oral yeast Candida albicans, a common commensal and opportunistic pathogen, or the bacterium Staphylococcus epidermidis, which is not normally pathogenic but is known to form biofilms on medical prostheses. The assays described belong to two approaches to investigating adhesion and biofilm formation: (i) retention at a fixed time point following liquid washes, and (ii) retention against a continuous flow of medium.

Biofilm ecology associated with dental caries: Understanding of microbial interactions in oral communities leads to development of therapeutic strategies targeting cariogenic biofilms

A biofilm is a sessile community characterized by cells attached to the surface and organized into a complex structural arrangement. Dental caries is a biofilm-dependent oral disease caused by infection with cariogenic pathogens, such as Streptococcus mutans, and associated with frequent exposure to a sugar-rich diet and poor oral hygiene. The virulence of cariogenic biofilms is often associated with the spatial organization of S. mutans enmeshed with exopolysaccharides on tooth surfaces. However, in the oral cavity, S. mutans does not act alone, and several other microbes contribute to cariogenic biofilm formation. Microbial communities in cariogenic biofilms are spatially organized into complex structural arrangements of various microbes and extracellular matrices. The balance of microbiota diversity with reduced diversity and a high proportion of acidogenic-aciduric microbiota within the biofilm is closely related to the disease state. Understanding the characteristics of polymicrobial biofilms and the association of microbial interactions within the biofilm (e.g., symbiosis, cooperation, and competition) in terms of their potential role in the pathogenesis of oral disease would help develop new strategies for interventions in virulent biofilm formation.

Characterization of the anti-pathogenic, genomic and phenotypic properties of a Lacticaseibacillus rhamnosus VHProbi M14 isolate

A strain of lactic acid bacteria from cheese was isolated, that showed strong growth inhibitory effects on Streptococcus mutans. The API 50CH system and 16S rDNA sequencing verified that this was a novel strain, and was named Lacticaseibacillus rhamnosus VHProbi M14. The strain inhibited the growth of S. mutans and Fusobacterium nucleatum under mixed culture conditions, coaggregated with S. mutans and F. nucleatum, and reduced the adhesion of S. mutans and F. nucleatum on cultured human primary gingival epithelial (HPGE) cells. The pH, peroxidase and protease sensitivity testing found antibacterial substances of protein- and peptide-like structures in addition to organic acids. The antimicrobial substances were sensitive to hydrolysis with trypsin, papain and pineapple protease and were inactived at temperatures above 100°C. Ammonium sulphate-precipitated proteins from the M14 strain retained the ability to inhibit the growth of S. mutans and F. nucleatum. The M14 strain contained 23 bacteriocin-related genes encoding for metabolites, belonging to class II bacteriocins. The M14 strain also showed inhibitory effects on 8 other pathogenic strains (A. actinomycetemcomitans, C. albicans, E. coli, G. vaginalis, P. acnes, P. gingivalis, S. aureus, S. enteritids), and thus has a broad spectrum of bacterial inhibition. This new isolate has been identified as having potential to be used as a probiotic bacterium in clinical applications.