Microbial Diversity in the Early In Vivo-Formed Dental Biofilm

Oral microbiota: Taxonomic composition and functional profile in caries-free and in caries-affected individuals - A systematic review

OBJECTIVE

To compare the oral microbiota among caries-free (CF) with caries-affected (CA) individuals, both at taxonomic and at functional levels.

DESIGN

This systematic review was conducted following PRISMA guidelines. A structured search was carried out in MEDLINE/PUBMED, Web of Science, EMBASE, LILACS, SciELO, Scopus and Google Scholar databases up to September, 2023. Observational studies, without any restriction on date of publication and using next-generation targeted or untargeted sequencing methods for identification of microbial communities were included. Qualitative synthesis was performed from all included studies.

RESULTS

54 studies were included (43 cross-sectional; 11 cohort) comprising more than 3486 participants (at least 1666 CF and 1820 CA) whose saliva and/or dental plaque were used as clinical samples. Methodological quality was graded as "fair" for most of the studies. The abundance of 87 bacterial and 44 fungal genera were statistically different among CF and CA individuals. Atopobium spp., Capnocytophaga spp., Lactobacillus spp., Prevotella spp., Scardovia spp., Selenomonas spp. among others were frequently reported as being more abundant in CA individuals. Several functional patterns, such as lipids, carbohydrate, starch, sucrose, amino sugar metabolisms, among others, were identified as being specifically related to CF or to CA conditions.

CONCLUSION

In spite of the variability among the included studies and of the predominance of qualitative synthesis, groups of microorganisms as well as specific functional profiles coded by the assessed microbiota are differently abundant among caries-affected and caries-free individuals. These results need to be interpreted with caution considering the limitations inherent to each assessed primary study.

The recovery of the microbial community after plaque removal depends on periodontal health status

Plaque accumulation and microbial community changes are important causes of periodontal disease. Cleaned plaque microorganisms will reattach to form biofilms, but the recovery and outcome of plaque microbial communities in different periodontal health states remain unknown. In this study, we tracked the biofilm remodeling process in 206 dental plaque samples from 40 healthy periodontal, gingivitis and periodontitis volunteers at 6 time points before and after supragingival scaling. We found that microbial communities of different periodontal states changed asynchronously during the process, and the more severe the periodontal disease condition, the more lagged the recovery of plaque microorganisms to their original state after cleaning; this reflected a higher degree of plaque development in periodontitis samples. The plaque index and bleeding index were significantly correlated with plaque recovery, especially the recovery of bacteria such as Abiotrophia and Capnocytophaga. Meanwhile, we found that the microbial community structure of different periodontal health states was most similar at the Day 3 after plaque cleaning, and the communities gradually differentiated and developed in different directions. Abiotrophia and other bacteria might play an important role in determining the development trend of plaque biofilms. The discovery of specific time points and bacteria was of great value in clarifying the pathogenesis of periodontal disease and in seeking targets for prevention and treatment.

Sensors for in situ monitoring of oral and dental health parameters in saliva

OBJECTIVES

The oral cavity is an easily accessible unique environment and open system which is influenced by the oral fluids, microbiota, and nutrition. Little is known about the kinetics and dynamics of metabolic processes at the intraoral surfaces. Real-time monitoring of salivary biomarkers, e.g., glucose, lactate, fluoride, calcium, phosphate, and pH with intraoral sensors is therefore of major interest. The aim of this review is to overview the existing literature for intraoral saliva sensors.

MATERIALS AND METHODS

A comprehensive literature search was performed to review the most relevant studies on intraoral saliva sensor technology.

RESULTS

There is limited literature about the in situ saliva monitoring of salivary biomarkers. Bioadhesion and biofouling processes at the intraoral surfaces limit the performances of the sensors. Real-time, long-term, and continuous intraoral measurement of salivary metabolites remains challenging and needs further investigation as only few well-functioning sensors have been developed until today. Until now, there is no sensor that measures reliably beyond hours for any analyte other than glucose.

CONCLUSIONS

Saliva's complex and dynamic structure as well as bioadhesion are key challenges and should be addressed in the future developments. Consequently, more studies that focus particularly on biofouling processes and interferential effects of the salivary matrix components on sensor surfaces are required.

CLINICAL RELEVANCE

By monitoring fluids in the oral cavity, as the entrance to the digestive system, extensive information can be obtained regarding the effects of foods and preventive agents on the oral microbiota and the tooth surfaces. This may lead to a better understanding of strategies to modulate oral and general health.

Preliminary landscape of Candidatus Saccharibacteria in the human microbiome

Introduction

Candidate Phyla Radiation (CPR) and more specifically Candidatus Saccharibacteria (TM7) have now been established as ubiquitous members of the human oral microbiota. Additionally, CPR have been reported in the gastrointestinal and urogenital tracts. However, the exploration of new human niches has been limited to date.

Methods

In this study, we performed a prospective and retrospective screening of TM7 in human samples using standard PCR, real-time PCR, scanning electron microscopy (SEM) and shotgun metagenomics.

Results

Using Real-time PCR and standard PCR, oral samples presented the highest TM7 prevalence followed by fecal samples, breast milk samples, vaginal samples and urine samples. Surprisingly, TM7 were also detected in infectious samples, namely cardiac valves and blood cultures at a low prevalence (under 3%). Moreover, we observed CPR-like structures using SEM in all sample types except cardiac valves. The reconstruction of TM7 genomes in oral and fecal samples from shotgun metagenomics reads further confirmed their high prevalence in some samples.

Conclusion

This study confirmed, through their detection in multiple human samples, that TM7 are human commensals that can also be found in clinical settings. Their detection in clinical samples warrants further studies to explore their role in a pathological setting.

Prevalence of Oral Pathogen Slackia exigua among Clinical Orthodontic and Non-Orthodontic Saliva Samples

Slackia exigua (SE) is a recently identified intestinal microbe, which recent oral surveys suggest may be associated with oral diseases including caries and periodontal disease. Based upon the lack of information regarding this organism, the primary objective of this study was to determine the oral prevalence of this microbe and any potential associations with patient characteristics such as age, sex, or the presence of orthodontic appliances. This retrospective study involved the screening of an existing saliva repository composed of previously collected unstimulated clinical saliva samples. More specifically, N = 266 were identified and screened using a spectrophotometer at absorbances of A260 and A280 nm to determine their DNA purity and concentration. qPCR screening of these samples revealed a higher prevalence of Slackia exigua positive samples among pediatric patients (63.1%) compared with adults (36.9%) in this clinic population, p = 0.0007. In addition, higher percentages of Slackia exigua were observed among orthodontic patients (71.2%) compared with non-orthodontic patients (28.8%), p = 0.0001. These results did not vary by sex with nearly equal percentages of Slackia exigua positive males and females among adult and pediatric patients, as well as orthodontic and non-orthodontic samples. These results suggest a strong potential for association between the prevalence of this organism with age as well as orthodontic status, given that younger patients and those with orthodontic brackets (regardless of age) were most likely to harbor this pathogen in sufficient levels to be detected in saliva. More research will be needed to determine any associations with specific outcomes, such as caries or periodontal disease, among Slackia exigua positive patients within these specific populations.

New Technological Approaches for Dental Caries Treatment: From Liquid Crystalline Systems to Nanocarriers

Dental caries is the most common oral disease, with high prevalence rates in adolescents and low-income and lower-middle-income countries. This disease originates from acid production by bacteria, leading to demineralization of the dental enamel and the formation of cavities. The treatment of caries remains a global challenge and the development of effective drug delivery systems is a potential strategy. In this context, different drug delivery systems have been investigated to remove oral biofilms and remineralize dental enamel. For a successful application of these systems, it is necessary that they remain adhered to the surfaces of the teeth to allow enough time for the removal of biofilms and enamel remineralization, thus, the use of mucoadhesive systems is highly encouraged. Among the systems used for this purpose, liquid crystalline systems, polymer-based nanoparticles, lipid-based nanoparticles, and inorganic nanoparticles have demonstrated great potential for preventing and treating dental caries through their own antimicrobial and remineralization properties or through delivering drugs. Therefore, the present review addresses the main drug delivery systems investigated in the treatment and prevention of dental caries.

Fluoride and gallein inhibit polyphosphate accumulation by oral pathogen Rothia dentocariosa

The uptake and storage of extracellular orthophosphate (Pi) by polyphosphate (polyP) accumulating bacteria may contribute to mineral dissolution in the oral cavity. To test the effect of potential inhibitors of polyP kinases on Rothia dentocariosa, gallein (0, 25, 50, and 100 μM) and fluoride (0, 50, and 100 ppm) were added to R. dentocariosa cultures grown in brain-heart infusion broth. At a late log growth phase (8 h), extracellular Pi was measured using an ascorbic acid assay, and polyP was isolated from bacterial cells treated with RNA/DNAases using a neutral phenol/chloroform extraction. Extracts were hydrolyzed and quantified as above. Gallein and fluoride had minor effects on bacterial growth with NaF having a direct effect on media pH. Gallein (≥25 μM) and fluoride (≥50 ppm) attenuated the bacterial drawdown of extracellular Pi by 56.7% (P < 0.05) and 37.3% (P < 0.01). There was a corresponding polyP synthesis decrease of 73.2% (P < 0.0001) from gallein and 83.1% (P < 0.0001) from fluoride. Attenuated total reflectance-Fourier-transform infrared spectroscopy validated the presence of polyP and its reduced concentration in R. dentocariosa bacterial cells following gallein and fluoride treatment. Rothia dentocariosa can directly change extracellular Pi and accumulate intracellular polyP, but the mechanism is attenuated by gallein and NaF.

MICROBIOLOGICAL FEATURES OF STAPHYLOCOCCUS ASSOCIATED WITH COMPLICATIONS OF DENTAL IMPLANTATION

OBJECTIVE

The aim: To describe microbiological features of the Staphylococcus spp. involved in complications of dental implantation.

PATIENTS AND METHODS

Materials and methods: The main method was bacteriological. Indentification of the obtained isolates was done using commercially available test kits. Adhesive properties were evaluated using Brillis technique. Biofilm-forming ability was studied according to Christensen et al. Antimicrobial susceptibility testing was done following EUCAST recomendations.

RESULTS

Results: There were 26 smears taken from the peri-implant area and gingival pockets of 12 patients. We obtained 38 isolates. Most of the patients were positive for Streptococcus spp. - 94% and Staphylococcus spp. - 90%. Among the representatives of Staphylococcus spp., the initial share of clinical isolates was S. aureus (34.21%) with inherent coagulase-positive properties. Coagulase-negative pathogens accounted for 65.79% of Staphylococcus spp., among them S. epidermidis, S. hominis, S. warneri were the main. All obtained isolates had typical properties, but appearance of small colonial variants of S. aureus was also recorded. Antimicrobial susceptibility testing was performed in 100% of cases. Among 13 isolates of S. aureus there were 2 cultures resistant to cefoxitin, i. e. methicillin-resistant by phenotype. Clinical isolates of S. aureus, colonizing peri-implant tissues in infectious-inflammatory complications of dental implantation, also had high adhesive and biofilm-forming properties. Clinical isolates of S. epidermidis an average ability to form biofilms.

CONCLUSION

Conclusions: There is a prooved direct correlation between biofilm-forming ability and adhesive properties in highly biofilm-forming clinical isolates involved in the occurrence of purulent-inflammatory complications in peri-implant site.

Caries Management-The Role of Surface Interactions in De- and Remineralization-Processes

BACKGROUND

Bioadhesion and surface interactions on enamel are of essential relevance for initiation, progression and prevention of caries and erosions. Salivary proteins on and within initial carious and erosive lesions can facilitate or aggravate de- and remineralization. This applies for the pellicle layer, the subsurface pellicle and for proteins within initial carious lesions. Little is known about these proteinaceous structures related to initial caries and erosion. Accordingly, there is a considerable demand for an understanding of the underlying processes occurring at the interface between the tooth surface and the oral cavity in order to develop novel agents that limit and modulate caries and erosion. Objectives and findings: The present paper depicts the current knowledge of the processes occurring at the interface of the tooth surface and the oral fluids. Proteinaceous layers on dental hard tissues can prevent or aggravate demineralization processes, whereas proteins within initial erosive or carious lesions might hinder remineralization considerably and restrict the entry of ions into lesions.

CONCLUSIONS

Despite the fact that organic-inorganic surface interactions are of essential relevance for de- and remineralization processes at the tooth surface, there is limited knowledge on these clinically relevant phenomena. Accordingly, intensive research is necessary to develop new approaches in preventive dentistry.

Effectiveness of the Human Oral Microbe Identification Microarray in Identifying Periodontal Pathogens: A Systematic Review

The aim of this review was to investigate the effectiveness of the Human Oral Microbe Identification Microarray (HOMIM) in identifying and quantifying bacterial species of the oral microbiome in periodontal disease. The search for articles was conducted in CENTRAL, CINAHL, MEDLINE and EMBASE by two reviewers, and included articles published in English between January 1990 and December 2021. The selected articles were human observational studies in adults between 18 and 65 years, presenting specific predefined keywords. Articles were initially selected by title and abstract; articles that met the inclusion criteria were analyzed for methodological quality using a detailed checklist for quality assessment. Data were extracted and reported using the PRISMA tool. The study design, sample, follow-up period, collection and microbial analysis methods, statistical treatment, results and discussion were quality assessed and risk of bias was evaluated using the Cochrane Risk-of-Bias tool. A narrative synthesis approach was used to synthesize and interpret the extracted data. From the initial search, 2931 articles were retrieved; 51 of these were then selected after screening by title and abstract. Subsequently, 8 articles met the inclusion after full-text reading and were classed according to methodological quality as high (2), moderate (3) or low (3). Studies included in this review were of high and medium quality. Data from the Human Oral Microbe Identification Microarray (HOMIM) provide much more robust results, showing major shifts between periodontal health and periodontal disease. Compared to earlier techniques such as Denaturing Gradient Gel Electrophoresis (DGGE), HOMIM represents a more effective approach for quantification due to its high sensitivity; thus, it is able to identify a high prevalence of periodontal pathogens and novel species in low abundance. The literature provides moderate evidence that the Human Oral Microbe Identification Microarray (HOMIM) is more effective in identifying and quantifying bacterial species of the oral microbiome in periodontal disease, compared to earlier molecular and non-molecular methods such as Denaturing Gradient Gel Electrophoresis (DGGE) and a culture-based approach with phenotypic tests.

The Common and Unique Pattern of Microbiome Profiles among Saliva, Tissue, and Stool Samples in Patients with Crohn’s Disease

This study aimed to elucidate common and unique microbiome patterns in saliva, intestinal tissue biopsy, and stool samples from patients with Crohn’s disease (CD). Saliva, tissue, and stool samples from patients with CD were prospectively collected. Quantitative and phylogenetic analyses of 16s rRNA sequencing data were performed with bioinformatical pipelines. A total of 30 patients were enrolled in this study. The composition of major microbial taxa was similar between tissue and stool samples. A total of 11 of the 20 most abundant microbiota were found in both samples. The microbial community in saliva was significantly distinct from that in tissue and stool. The major species of microbiota and their composition also differed significantly from those of tissue and stool samples. However, Streptococcus and Prevotella are common genera in saliva, tissue, and stool microbiome. The abundance of Streptococcus, Pantoea, and Actinomyces from the saliva sample group were significantly different, varying with the location of the inflammation. Saliva has a distinct microbial community compared with tissues and stools in patients with CD. Prevotella and Streptococcus, which are commonly observed in saliva, stool, and tissue, can be considered a potential biomarker related to the diagnosis or prognosis of CD.

Bacteriophage-Mediated Control of Biofilm: A Promising New Dawn for the Future

Biofilms are complex microbial microcolonies consisting of planktonic and dormant bacteria bound to a surface. The bacterial cells within the biofilm are embedded within the extracellular polymeric substance (EPS) consisting mainly of exopolysaccharides, secreted proteins, lipids, and extracellular DNA. This structural matrix poses a major challenge against common treatment options due to its extensive antibiotic-resistant properties. Because biofilms are so recalcitrant to antibiotics, they pose a unique challenge to patients in a nosocomial setting, mainly linked to lower respiratory, urinary tract, and surgical wound infections as well as the medical devices used during treatment. Another unique property of biofilm is its ability to adhere to both biological and man-made surfaces, allowing growth on human tissues and organs, hospital tools, and medical devices, etc. Based on prior understanding of bacteriophage structure, mechanisms, and its effects on bacteria eradication, leading research has been conducted on the effects of phages and its individual proteins on biofilm and its role in overall biofilm removal while also revealing the obstacles this form of treatment currently have. The expansion in the phage host-species range is one that urges for improvement and is the focus for future studies. This review aims to demonstrate the advantages and challenges of bacteriophage and its components on biofilm removal, as well as potential usage of phage cocktail, combination therapy, and genetically modified phages in a clinical setting.

Polymicrobial Interactions of Oral Microbiota: a Historical Review and Current Perspective

The oral microbiota is enormously diverse, with over 700 microbial species identified across individuals that play a vital role in the health of our mouth and our overall well-being. In addition, as oral diseases such as caries (cavities) and periodontitis (gum disease) are mediated through interspecies microbial interactions, this community serves as an important model system to study the complexity and dynamics of polymicrobial interactions. Here, we review historical and recent progress in our understanding of the oral microbiome, highlighting how oral microbiome research has significantly contributed to our understanding of microbial communities, with broad implications in polymicrobial diseases and across microbial community ecology. Further, we explore innovations and challenges associated with analyzing polymicrobial systems and suggest future directions of study. Finally, we provide a conceptual framework to systematically study microbial interactions within complex communities, not limited to the oral microbiota.

Polymicrobial Aggregates in Human Saliva Build the Oral Biofilm

Biofilm community development has been established as a sequential process starting from the attachment of single cells on a surface. However, microorganisms are often found as aggregates in the environment and in biological fluids. Here, we conduct a comprehensive analysis of the native structure and composition of aggregated microbial assemblages in human saliva and investigate their spatiotemporal attachment and biofilm community development. Using multiscale imaging, cell sorting, and computational approaches combined with sequencing analysis, a diverse mixture of aggregates varying in size, structure, and microbial composition, including bacteria associated with host epithelial cells, can be found in saliva in addition to a few single-cell forms. Phylogenetic analysis reveals a mixture of complex consortia of aerobes and anaerobes in which bacteria traditionally considered early and late colonizers are found mixed together. When individually tracked during colonization and biofilm initiation, aggregates rapidly proliferate and expand tridimensionally, modulating population growth, spatial organization, and community scaffolding. In contrast, most single cells remain static or are incorporated by actively growing aggregates. These results suggest an alternative biofilm development process whereby aggregates containing different species or associated with human cells collectively adhere to the surface as “growth nuclei” to build the biofilm and shape polymicrobial communities at various spatial and taxonomic scales.

Biofilm disruption and bactericidal activity of aqueous ozone coupled with ultrasonic dental scaling

Background

The COVID-19 pandemic has heightened the awareness of a common hazard encountered in the dental clinic: aerosol transmission of pathogens. Treatment of sources of infection before or during dental procedures is one means of decreasing pathogen load and aerosol transmission.

Methods

An ultrasonic scaler supplied with aqueous ozone was used to examine the effect of its viability on planktonic cultures and biofilms formed by 2 model bacteria: Rothia mucilaginosa and Escherichia coli.

Results

Both organisms showed susceptibility to aqueous ozone alone (97% and 99.5% lethality, respectively). When combined with manual scaling using an ultrasonic scaler, a greater than 99% reduction in colony-forming units (CFUs)/mL could be reached with an aqueous ozone concentration of approximately 2 mg/L (R. mucilaginosa) or 0.75 mg/L (E. coli) after 5 through 6 seconds of scaling.

Conclusions

Aqueous ozone coupled with ultrasonic scaling exhibited a higher efficiency of microbial kill than either method used alone. Both gram-positive and gram-negative species were affected by this treatment. Studies on other oral microbiota constituents, including fungi and viruses, will provide information on the efficacy of this method on a greater biological scale. Studies to verify concomitant reduction of microbial load in dispersed aerosols in clinical settings should be completed to support practical applications of this treatment.

Gemella haemolysans inhibits the growth of the periodontal pathogen Porphyromonas gingivalis

The oral microbiome plays an important role in the human microbial community and in maintaining the health of an individual. Imbalances in the oral microbiome may contribute to oral and systemic diseases. The progression of periodontal disease is closely related to the growth of bacteria, such as Porphyromonas gingivalis, in the oral cavity. However, the pathogen growth mechanism specific to periodontal disease remains unknown. This study aimed to identify bacteria associated with periodontal health by focusing on hemolytic bacteria. Unstimulated saliva samples were collected from ten periodontitis patients and five healthy subjects to detect and identify the presence of hemolytic bacteria. The saliva of healthy subjects contained a higher proportion of G. haemolysans than saliva samples from patients with periodontitis. Growth inhibition assays indicated that the protein components contained in the culture supernatant of G. haemolysans directly suppressed the growth of P. gingivalis. This study shows that the presence of G. haemolysans in saliva is associated with periodontal health and that it inhibits the growth of P. gingivalis in vitro.

Advances in the Microbiology of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen of significant concern to susceptible patient populations. This pathogen can cause nosocomial and community-acquired respiratory and bloodstream infections and various other infections in humans. Sources include water, plant rhizospheres, animals, and foods. Studies of the genetic heterogeneity of S. maltophilia strains have identified several new genogroups and suggested adaptation of this pathogen to its habitats. The mechanisms used by S. maltophilia during pathogenesis continue to be uncovered and explored. S. maltophilia virulence factors include use of motility, biofilm formation, iron acquisition mechanisms, outer membrane components, protein secretion systems, extracellular enzymes, and antimicrobial resistance mechanisms. S. maltophilia is intrinsically drug resistant to an array of different antibiotics and uses a broad arsenal to protect itself against antimicrobials. Surveillance studies have recorded increases in drug resistance for S. maltophilia, prompting new strategies to be developed against this opportunist. The interactions of this environmental bacterium with other microorganisms are being elucidated. S. maltophilia and its products have applications in biotechnology, including agriculture, biocontrol, and bioremediation.

Changes in oral flora of patients with functional dyspepsia

To explore the changes in oral flora in people with functional dyspepsia (FD). Unstimulated saliva was collected from 21 FD patients diagnosed according to the Rome IV criteria and from 12 healthy controls (HCs) for 16SrRNA sequencing. The pH of saliva samples and community periodontal index (CPI) were tested. The prevalence of small intestinal bacterial overgrowth (SIBO) was obtained by the methane-and hydrogen-based breath test. At the phylum level, FD patients had a higher relative abundance of Spirochaetes and a lower relative abundance of Fusobacteria, TM7 and Proteobacteria than HCs (p < 0.01). In the saliva, Kingella and Abiotrophia genus levels showed significant changes between the FD and HC groups (p < 0.01). Salivary species level marker Intermedia was significantly different between FD and HC groups (p < 0.01). The oral pH of FD patients was higher than that of HCs (p < 0.01). The mean CPI of the FD group was 1.52 and that of the HC group was 0.17 (p < 0.01). Moreover, 71.4% of the FD group was positive for SIBO. The oral flora of FD patients was different from that of HCs. Spirochaetes, Kingella, Abiotrophia, and Intermedia may be diagnostic indicators of FD.

An Overview of Biological and Computational Methods for Designing Mechanism-Informed Anti-biofilm Agents

Bacterial biofilms are complex and highly antibiotic-resistant aggregates of microbes that form on surfaces in the environment and body including medical devices. They are key contributors to the growing antibiotic resistance crisis and account for two-thirds of all infections. Thus, there is a critical need to develop anti-biofilm specific therapeutics. Here we discuss mechanisms of biofilm formation, current anti-biofilm agents, and strategies for developing, discovering, and testing new anti-biofilm agents. Biofilm formation involves many factors and is broadly regulated by the stringent response, quorum sensing, and c-di-GMP signaling, processes that have been targeted by anti-biofilm agents. Developing new anti-biofilm agents requires a comprehensive systems-level understanding of these mechanisms, as well as the discovery of new mechanisms. This can be accomplished through omics approaches such as transcriptomics, metabolomics, and proteomics, which can also be integrated to better understand biofilm biology. Guided by mechanistic understanding, in silico techniques such as virtual screening and machine learning can discover small molecules that can inhibit key biofilm regulators. To increase the likelihood that these candidate agents selected from in silico approaches are efficacious in humans, they must be tested in biologically relevant biofilm models. We discuss the benefits and drawbacks of in vitro and in vivo biofilm models and highlight organoids as a new biofilm model. This review offers a comprehensive guide of current and future biological and computational approaches of anti-biofilm therapeutic discovery for investigators to utilize to combat the antibiotic resistance crisis.

A Rare Case of Periprosthetic Joint Infection Caused by a Periodontal Pathogen, Slackia exigua: A Case Report

CASE

A 72-year-old woman with a history of right total hip arthroplasty and subsequent revision 18 years ago developed right hip periprosthetic joint infection with significant bone destruction caused by Slackia exigua. She underwent a dental cavity filling without prophylactic antibiotics before presentation that may have contributed to development of the infection. The patient required total hip revision and prolonged antibiotic therapy to eradicate the bacteria.

CONCLUSION

This case is an example that certain high-risk patients undergoing invasive dental procedures are at risk of developing prosthetic joint infection.

A novel sialic acid-binding adhesin present in multiple species contributes to the pathogenesis of Infective endocarditis

Bacterial binding to platelets is a key step in the development of infective endocarditis (IE). Sialic acid, a common terminal carbohydrate on host glycans, is the major receptor for streptococci on platelets. So far, all defined interactions between streptococci and sialic acid on platelets are mediated by serine-rich repeat proteins (SRRPs). However, we identified Streptococcus oralis subsp. oralis IE-isolates that bind sialic acid but lack SRRPs. In addition to binding sialic acid, some SRRP^- isolates also bind the cryptic receptor β-1,4-linked galactose through a yet unknown mechanism. Using comparative genomics, we identified a novel sialic acid-binding adhesin, here named AsaA (associated with sialic acid adhesion A), present in IE-isolates lacking SRRPs. We demonstrated that S. oralis subsp. oralis AsaA is required for binding to platelets in a sialic acid-dependent manner. AsaA comprises a non-repeat region (NRR), consisting of a FIVAR/CBM and two Siglec-like and Unique domains, followed by 31 DUF1542 domains. When recombinantly expressed, Siglec-like and Unique domains competitively inhibited binding of S. oralis subsp. oralis and directly interacted with sialic acid on platelets. We further demonstrated that AsaA impacts the pathogenesis of S. oralis subsp. oralis in a rabbit model of IE. Additionally, we found AsaA orthologues in other IE-causing species and demonstrated that the NRR of AsaA from Gemella haemolysans blocked binding of S. oralis subsp. oralis, suggesting that AsaA contributes to the pathogenesis of multiple IE-causing species. Finally, our findings provide evidence that sialic acid is a key factor for bacterial-platelets interactions in a broader range of species than previously appreciated, highlighting its potential as a therapeutic target.

Infective endocarditis (IE) is typically a bacterial infection of the heart valves that causes high mortality. Infective endocarditis can affect people with preexisting lesions on their heart valves (Subacute IE). These lesions contain platelets and other host factors to which bacteria can bind. Growth of bacteria and accumulation of host factors results in heart failure. Therefore, the ability of bacteria to bind platelets is key to the development of IE. Here, we identified a novel bacterial protein, AsaA, which helps bacteria bind to platelets and contributes to the development of disease. Although this virulence factor was characterized in Streptococcus oralis, a leading cause of IE, we demonstrated that AsaA is also present in several other IE-causing bacterial species and is likely relevant to their ability to cause disease. We showed that AsaA binds to sialic acid, a terminal sugar present on platelets, thereby demonstrating that sialic acid serves as a receptor for a wider range of IE-causing bacteria than previously appreciated, highlighting its potential as a therapeutic target.

In vitro Interactions between Streptococcus intermedius and Streptococcus salivarius K12 on a Titanium Cylindrical Surface

Peri-implantitis is a steadily rising disease and is caused by oral bacterial pathogens able to form biofilm on implant surfaces and peri-implant tissues, making antibiotics treatment less effective. The use of commercial probiotics against oral pathogens could serve as an alternative to prevent biofilm formation. Streptococcus intermedius is one of the early colonizers of biofilm formation in dental implants. The aim of this study was to model the interaction between S. intermedius and Streptococcus salivarius strain K12, a probiotic bacterium producing bacteriocins. S. intermedius was co-cultured with S. salivarius K12 in an in vitro model simulating the biofilm formation in a dental implant composed by a titanium cylinder system. Biofilm formation rate was assessed by Real-Time PCR quantification of bacterial count and expression levels of luxS gene, used in response to cell density in the biofilm. Biofilm formation, bacteriocin production, luxS expression patterns were found to be already expressed within the first 12 h. More importantly, S. salivarius K12 was able to counter the biofilm formation in a titanium cylinder under the tested condition. In conclusion, our dental implant model may be useful for exploring probiotic-pathogen interaction to find an alternative to antibiotics for peri-implantitis treatment.

Tetracycline and multidrug resistance in the oral microbiota: differences between healthy subjects and patients with periodontitis in Spain

Introduction: Antibiotic resistance is widely found even among bacterial populations not having been exposed to selective pressure by antibiotics, such as tetracycline. In this study we analyzed the tetracycline-resistant subgingival microbiota of healthy subjects and of patients with periodontitis, comparing the prevalence of tet genes and their multidrug resistance profiles.

Methods: Samples from 259 volunteers were analyzed, obtaining 813 tetracycline-resistant isolates. The prevalence of 12 antibiotic resistance genes was assessed, and multidrug profiles were built. Each isolate was identified by 16S rRNA sequencing. Differences in qualitative data and quantitative data were evaluated using the chi-square test and the Mann-Whitney-U test, respectively.

Results: tet(M) was the most frequently detected tet gene (52.03%). We observed significant differences between the prevalence of tet(M), tet(W), tet(O), tet(32) and tet(L) in both populations studied. Multidrug resistance was largely observed, with resistance to kanamycin being the most detected (83.64%). There were significant differences between the populations in the prevalence of kanamycin, chloramphenicol, and cefotaxime resistance. Resistant isolates showed significantly different prevalence between the two studied groups.

Conclusion: The high prevalence of multidrug resistance and tetracycline resistance genes found in the subgingival microbiota, highlights the importance of performing wider and more in-depth analysis of antibiotic resistance in the oral microbiota.

Bioadhesion in the oral cavity and approaches for biofilm management by surface modifications

BACKGROUND

All soft and solid surface structures in the oral cavity are covered by the acquired pellicle followed by bacterial colonization. This applies for natural structures as well as for restorative or prosthetic materials; the adherent bacterial biofilm is associated among others with the development of caries, periodontal diseases, peri-implantitis, or denture-associated stomatitis. Accordingly, there is a considerable demand for novel materials and coatings that limit and modulate bacterial attachment and/or propagation of microorganisms.

OBJECTIVES AND FINDINGS

The present paper depicts the current knowledge on the impact of different physicochemical surface characteristics on bioadsorption in the oral cavity. Furthermore, it was carved out which strategies were developed in dental research and general surface science to inhibit bacterial colonization and to delay biofilm formation by low-fouling or "easy-to-clean" surfaces. These include the modulation of physicochemical properties such as periodic topographies, roughness, surface free energy, or hardness. In recent years, a large emphasis was laid on micro- and nanostructured surfaces and on liquid repellent superhydrophic as well as superhydrophilic interfaces. Materials incorporating mobile or bound nanoparticles promoting bacteriostatic or bacteriotoxic properties were also used. Recently, chemically textured interfaces gained increasing interest and could represent promising solutions for innovative antibioadhesion interfaces. Due to the unique conditions in the oral cavity, mainly in vivo or in situ studies were considered in the review.

CONCLUSION

Despite many promising approaches for modulation of biofilm formation in the oral cavity, the ubiquitous phenomenon of bioadsorption and adhesion pellicle formation in the challenging oral milieu masks surface properties and therewith hampers low-fouling strategies.

CLINICAL RELEVANCE

Improved dental materials and surface coatings with easy-to-clean properties have the potential to improve oral health, but extensive and systematic research is required in this field to develop biocompatible and effective substances.

High-throughput sequencing provides insights into oral microbiota dysbiosis in association with inflammatory bowel disease

Although the prevalence of inflammatory bowel disease (IBD) has been increasing worldwide, the etiology remains elusive. Investigating oral microbiota dysbiosis is essential to understanding IBD pathogenesis. Our study evaluated variations in salivary microbiota and identified potential associations with IBD. The saliva microbiota of 22 IBD patients and 8 healthy controls (HCs) was determined using 16S ribosomal RNA (rRNA) gene sequencing and analyzed using QIIME2. A distinct saliva microbiota dysbiosis in IBD, characterized by alterations in microbiota biodiversity and composition, was identified. Saccharibacteria (TM7), Absconditabacteria (SR1), Leptotrichia, Prevotella, Bulleidia, and Atopobium, some of which are oral biofilm-forming bacteria, were significantly increased. Moreover, levels of inflammatory cytokines associated with IBD were elevated and positively correlated with TM7 and SR1. Functional variations include down-regulation of genetic information processing, while up-regulation of carbohydrate metabolism and protein processing in the endoplasmic reticulum in IBD. Our data implicate salivary microbiota dysbiosis involving in IBD pathogenesis.

Human oral microbiome dysbiosis as a novel non-invasive biomarker in detection of colorectal cancer

Background: The oral microbiome may play an important role in colorectal carcinogenesis. However, few studies have investigated the association between oral microbiome and the development of colorectal cancer (CRC). We aimed to investigate whether oral health-colorectal tumor association has an underlying microbial basis, in the quest for novel non-invasive biomarkers for CRC.

Methods: We collected oral swab samples from 161 patients with CRC, 34 patients with colorectal adenoma (CRA), and 58 healthy volunteers. The oral microbiota was assessed using 16S rRNA sequencing. We characterized oral microbiome, identified microbial markers, constructed and validated colorectal tumor (CRA and CRC) classifier.

Results: Oral microbial composition and diversity were significantly different among the three groups, and the CRA group had the highest diversity. Analysis of the functional potential of oral microbiota demonstrated that the pathway involving cell motility was overrepresented in the CRA and CRC groups relative to that in the healthy controls. Moreover, a random forest model was constructed based on oral microbial markers, which could distinguish the colorectal tumor groups from the healthy controls and achieve a powerful classification potential in the discovery and validation cohorts.

Conclusion: This study suggests a potential association between oral microbiome dysbiosis and colorectal cancer. Oral microbiota-based biomarkers may be helpful in predicting the risks for the development of CRA and CRC.

Microbiomes of colored dental biofilms in children with or without severe caries experience

BACKGROUND

Biofilm coloration can compromise maturation and increase the risk of oral disease in adulthood, though children with colored biofilm do not always demonstrate a poor oral health status.

AIM

The microbial compositions of colored and white biofilms in children were compared.

DESIGN

Thirty-two dental biofilm samples from 16 children (age < 13 years) were analyzed using 16S rRNA pyrosequencing, then the subjects were divided into severe caries and healthy (caries-free) groups. Correlations between microbiomes and oral health status were also examined.

RESULTS

Phylogenetic analysis revealed no distinctly different patterns between colored and white biofilms. In the severe caries group, genus Actinomyces, Cardiobacterium, Kingella, Lautropia, and Veillonella, and family Neisseriaceae were detected, though abundance was significantly different between colored and white biofilm specimens, in contrast to the healthy group. In addition, five colored biofilm samples from the severe caries group contained greater than 15% Actinomyces, which led us to consider that genus to be possibly associated with formation of colored biofilm in children.

CONCLUSIONS

Our findings indicate that differences in bacterial composition between colored and white biofilms are higher in individuals with severe caries. Additional research may reveal the significance of colored dental biofilm in children.

Antimicrobial Peptide GH12 Prevents Dental Caries by Regulating Dental Plaque Microbiota

Due to the complex microecology and microenvironment of dental plaque, novel caries prevention strategies require modulating the microbial communities ecologically and reducing the cariogenic properties effectively. Antimicrobial peptide GH12 reduced the lactic acid production and exopolysaccharide (EPS) synthesis of a Streptococcus mutans biofilm and a three-species biofilm in vitro in previous studies. However, the anticaries effects and microecological effects of GH12 remained to be investigated in a complex biofilm model in vitro and an animal caries model in vivo In the present study, GH12 at 64 mg/liter showed the most effective inhibition of lactic acid production, EPS synthesis, pH decline, and biofilm integrity of human dental plaque-derived multispecies biofilms in vitro, and GH12 at 64 mg/liter was therefore chosen for use in subsequent in vitro and in vivo assays. When treated with 64-mg/liter GH12, the dental plaque-derived multispecies biofilms sampled from healthy volunteers maintained its microbial diversity and showed a microbial community structure similar to that of the control group. In the rat caries model with a caries-promoting diet, 64-mg/liter GH12 regulated the microbiota of dental plaque, in which the abundance of caries-associated bacteria was decreased and the abundance of commensal bacteria was increased. In addition, 64-mg/liter GH12 significantly reduced the caries scores of sulcal and smooth surface caries in all locations. In conclusion, GH12 inhibited the cariogenic properties of dental plaque without perturbing the dental plaque microbiota of healthy individuals and GH12 regulated the dysbiotic microbial ecology and arrested caries development under cariogenic conditions.IMPORTANCE The anticaries effects and microecological regulation effects of the antimicrobial peptide GH12 were evaluated systematically in vitro and in vivo GH12 inhibited the cariogenic virulence of dental plaque without overintervening in the microbial ecology of healthy individuals in vitro GH12 regulated the microbial ecology of dental plaque to a certain extent in vivo under cariogenic conditions, increased the proportion of commensal bacteria, and decreased the abundance of caries-associated bacteria. GH12 significantly suppressed the incidence and severity of dental caries in vivo This study thus describes an alternative antimicrobial therapy for dental caries.

Amixicile depletes the ex vivo periodontal microbiome of anaerobic bacteria

OBJECTIVES

Although periodontal diseases result from overgrowth of anaerobic bacteria, the effect of a specific knockdown of anaerobes on the disease outcome has yet to be examined. We have reported that amixicile, a non-toxic, readily bioavailable, and novel antimicrobial, specifically targets selected oral anaerobes through inhibition of the activity of pyruvate ferredoxin oxidoreductase (PFOR), a major enzyme mediating oxidative decarboxylation of pyruvate.

METHODS

Here, we generated an ex vivo microbiome derived from gingival pockets of human subjects with chronic periodontal disease and evaluated the efficacy of amixicile in generating a specific knockdown of anaerobic bacteria present in the microbiome.

RESULTS

Our bioinformatics analysis identified PFOR-like coding capacity in over 100 genomes available from the HOMD database. Many of those bacteria were present in our ex vivo microbiome. Significantly, the anaerobic pathogens relying on PFOR for energy generation were specifically reduced in abundance following treatment with amixicile while non-PFOR bacteria were spared. Specifically, Prevotella, Veillonella, Slackia, Porphyromonas, Treponema, Megasphera, and Atobium were reduced in abundance. Such treatment resulted in the conversion of a microbiome resembling a microbiome derived from sites with periodontal disease to one resembling a microbiome present at healthy sites. We also compared the inhibitory spectrum of amixicile to that of metronidazole and showed that the antibiotics have a similar inhibitory spectrum.

CONCLUSIONS

This work further demonstrates that amixicile has the potential to reverse and prevent the outgrowth of anaerobic pathogens observed in subjects with periodontal disease.

A Uniquely Altered Oral Microbiome Composition Was Observed in Pregnant Rats With Porphyromonas gingivalis Induced Periodontal Disease

Porphyromonas gingivalis is an anaerobic bacterium commonly found in the oral cavity and associated with the development of periodontal disease. P. gingivalis has also been linked to several systemic vascular and inflammatory diseases including poor pregnancy outcomes. Little is known about the changes in the oral flora during pregnancy in connection to P. gingivalis infection. This pilot study aims to explore changes in the oral microbiome due to P. gingivalis inoculation and pregnancy in an in vivo rat model of periodontal disease. A metagenomic sequencing analysis targeting seven of the 16S rRNA gene variable regions was performed for oral samples collected at the following time points: baseline control (week 0), P. gingivalis inoculated (week 11), P. gingivalis inoculated and pregnant rat at necropsy (week 16). A second set of animals were also sampled to generate a sham-inoculated (week 11) control group. We found that the rat oral microbiome profiles were more similar to that of the human oral cavity compared to previous reports targeting one or two 16S variable regions. Overall, there appears to be a relatively stable core microbiome in the oral cavity. As expected, P. gingivalis induced periodontal disease resulted in oral microbiome dysbiosis. During pregnancy, some aspects of the oral microbiome shifted toward a more baseline-like profile. However, population analyses in terms of dissimilarity measures and especially metagenomic based predictions of select characteristics such as cell morphology, oxygen requirement, and major metabolite synthesis showed that pregnancy did not restore the composition of the oral microbiome. Rather, a uniquely altered oral microbiome composition was observed in pregnant rats with pre-established periodontal disease.

Analysis of plaque microbiota and salivary proteins adhering to dental materials

OBJECTIVES

Plaque causes oral diseases and aspiration-pneumonia in the elderly. It is not known whether pellicle-like attached salivary proteins and microbiota on dental materials are identical to those on teeth. The purpose of this study was to determine the properties of salivary proteins and microbiota that attach to dental materials.

METHODS

Eight subjects wore removable oral splints with pieces of pure-titanium, cobalt-chromium alloy, silver-palladium-copper-gold-alloy, denture-base-resin, and hydroxyapatite for 24 h. The bacteria that adhered to each material were analyzed using 16S rRNA sequencing simultaneously. Each material sample was then immersed in pooled saliva, and the attached proteins were collected. Salivary proteins were analyzed using MALDI-TOF/MS, and high molecular weight proteins were identified using peptide mass fingerprinting.

RESULTS

Among the dental materials, the α- and β-diversity of adherent flora were similar. The bacterial species that adhered easily to materials were Streptococcus sp. oral taxon 058, Neisseria mucosa, Gemella haemolysans, and Rothia dentocariosa. Regardless of material, the peaks or spots of attached salivary proteins had similar patterns, containing functioning proteins such as anchoring receptors for early colonizers.

CONCLUSIONS

There were no significant differences in microbiota and protein adherence in hydroxyapatite compared to the dental materials. Therefore, similar microbiota was determined to have formed on the similar pellicle-like proteins. In our study, the characteristics of plaque adhesion on both hydroxyapatite and dental materials were clarified. Based on this study, the creation of new methods of inhibiting plaque adhesion to prevent aspiration-pneumonia and oral infections can be undertaken.

PcsB Expression Diversity Influences on Streptococcus mitis Phenotypes Associated With Host Persistence and Virulence

S. mitis is an abundant member of the commensal microbiota of the oral cavity and pharynx, which has the potential to promote systemic infections. By analyzing a collection of S. mitis strains isolated from the oral cavity at commensal states or from systemic infections (blood strains), we established that S. mitis ubiquitously express the surface immunodominant protein, PcsB (also called GbpB), required for binding to sucrose-derived exopolysaccharides (EPS). Immuno dot blot assays with anti-PcsB antibodies and RT-qPCR transcription analyses revealed strain-specific profiles of PcsB production associated with diversity in pcsB transcriptional activities. Additionally, blood strains showed significantly higher levels of PcsB expression compared to commensal isolates. Because Streptococcus mutans co-colonizes S. mitis dental biofilms, and secretes glucosyltransferases (GtfB/C/D) for the synthesis of highly insoluble EPS from sucrose, profiles of S. mitis binding to EPS, biofilm formation and evasion of the complement system were assessed in sucrose-containing BHI medium supplemented or not with filter-sterilized S. mutans culture supernatants. These analyses showed significant S. mitis binding to EPS and biofilm formation in the presence of S. mutans supernatants supplemented with sucrose, compared to BHI or BHI-sucrose medium. In addition, these phenotypes were abolished if strains were grown in culture supernatants of a gtfBCD-defective S. mutans mutant. Importantly, GtfB/C/D-associated phenotypes were enhanced in high PcsB-expressing strains, compared to low PcsB producers. Increased PcsB expression was further correlated with increased resistance to deposition of C3b/iC3b of the complement system after exposure to human serum, when strains were previously grown in the presence of S. mutans supernatants. Finally, analyses of PcsB polymorphisms and bioinformatic prediction of epitopes with significant binding to MHC class II alleles revealed that blood isolates harbor PcsB polymorphisms in its functionally conserved CHAP-domain, suggesting antigenic variation. These findings reveal important roles of PcsB in S. mitis-host interactions under commensal and pathogenic states, highlighting the need for studies to elucidate mechanisms regulating PcsB expression in this species.

Identification of Initial Colonizing Bacteria in Dental Plaques from Young Adults Using Full-Length 16S rRNA Gene Sequencing

Selective attachment of salivary bacteria to the tooth surface is an initial and repetitive phase in dental plaque development. We employed full-length 16S rRNA gene sequence analysis with a high taxonomic resolution using a third-generation sequencer, PacBio Sequel, to determine the bacterial composition during early plaque formation in 74 young adults accurately and in detail. The results revealed 21 bacterial taxa primarily involved in early plaque formation on hydroxyapatite disks in young adults, which include several streptococcal species as well as nonstreptococcal species, such as Neisseria sicca/N. flava/N. mucosa and Rothia dentocariosa. Given that no notable variations in the microbiota composition were associated with the dental caries status, the maturation process, rather than the specific bacterial species that are the initial colonizers, is likely to play an important role in the development of dysbiotic microbiota associated with dental caries.

Development of dental plaque begins with the adhesion of salivary bacteria to the acquired pellicle covering the tooth surface. In this study, we collected in vivo dental plaque formed on hydroxyapatite disks for 6 h from 74 young adults and identified initial colonizing taxa based on full-length 16S rRNA gene sequences. A long-read, single-molecule sequencer, PacBio Sequel, provided 100,109 high-quality full-length 16S rRNA gene sequence reads from the early plaque microbiota, which were assigned to 90 oral bacterial taxa. The microbiota obtained from every individual mostly comprised the 21 predominant taxa with the maximum relative abundance of over 10% (95.8 ± 6.2%, mean ± SD), which included Streptococcus species as well as nonstreptococcal species. A hierarchical cluster analysis of their relative abundance distribution suggested three major patterns of microbiota compositions: a Streptococcus mitis/Streptococcus sp. HMT-423-dominant profile, a Neisseria sicca/Neisseria flava/Neisseria mucosa-dominant profile, and a complex profile with high diversity. No notable variations in the community structures were associated with the dental caries status, although the total bacterial amounts were larger in the subjects with a high number of caries-experienced teeth (≥8) than in those with no or a low number of caries-experienced teeth. Our results revealed the bacterial taxa primarily involved in early plaque formation on hydroxyapatite disks in young adults.

IMPORTANCE Selective attachment of salivary bacteria to the tooth surface is an initial and repetitive phase in dental plaque development. We employed full-length 16S rRNA gene sequence analysis with a high taxonomic resolution using a third-generation sequencer, PacBio Sequel, to determine the bacterial composition during early plaque formation in 74 young adults accurately and in detail. The results revealed 21 bacterial taxa primarily involved in early plaque formation on hydroxyapatite disks in young adults, which include several streptococcal species as well as nonstreptococcal species, such as Neisseria sicca/N. flava/N. mucosa and Rothia dentocariosa. Given that no notable variations in the microbiota composition were associated with the dental caries status, the maturation process, rather than the specific bacterial species that are the initial colonizers, is likely to play an important role in the development of dysbiotic microbiota associated with dental caries.

Effect of mechanically stimulated saliva on initial human dental biofilm formation

This study evaluated the impact of mechanically stimulated saliva on initial bacterial colonization. Interaction between oral bacteria and both unstimulated and stimulated saliva was examined in vitro by laying labeled bacteria over SDS-PAGE-separated salivary proteins. The effects of chewing on in vivo biofilm, microbial composition, and spatial arrangement were examined in two human volunteers using an intraoral stent containing retrievable enamel chips. In vitro experiments showed that bacterial binding to proteins from stimulated saliva was lower than that to proteins from unstimulated saliva. Lack of binding activity was noted with Streptococcus mutans and Lactobacillus casei. Human Oral Microbe Identification Microarray (HOMIM) analyses revealed a consistent chewing-related increase in the binding of Streptococcus anginosus and Streptococcus gordonii. Immunofluorescence microscopy demonstrated the presence of multi-species colonies and cells bearing different serotypes of the coaggregation-mediating streptococcal cell-surface receptor polysaccharides (RPS). Differences in bacterial colonization were noted between the two volunteers, while the type 4 RPS-reactive serotype was absent in one volunteer. Cells reacting with antibody against Rothia or Haemophilus were prominent in the early biofilm. While analysis of the data obtained demonstrated inter-individual variations in both in vitro and in vivo bacterial binding patterns, stimulating saliva with multiple orosensory stimuli may modulate oral bacterial colonization of tooth surfaces.

A Comparison of Flavorless Electronic Cigarette-Generated Aerosol and Conventional Cigarette Smoke on the Survival and Growth of Common Oral Commensal Streptococci

Background: The use of electronic cigarettes (ECIG) has become very common. Consequently, critical analysis of the biological effects of ECIG aerosol deserves attention. Flavorless ECIG aerosol is known to comprise fewer harmful constituents than cigarette smoke. Therefore, we hypothesize that aerosol has less immediate effect on the viability of oral commensal streptococci than smoke. Methods: Survival and growth of four strains of commensal streptococci were measured after exposure to flavorless ECIG aerosol ± nicotine and smoke. Peristaltic pumps were used to transport aerosol or smoke into chambers containing recently seeded colony-forming units (CFUs) of the oral commensal streptococci on agar plates. Bacterial survival and growth, based on colony counts and sizes, were determined 24 h post-exposure. Additionally, aerosol or smoke were delivered into chambers containing pre-adhered streptococci to plastic coverslips and biofilm formation was determined 24 h post-exposure via scanning electron microscopy. Results: The results suggest that flavorless aerosol ± nicotine has a modest effect on bacterial growth both as colonies on agar and as biofilms. In contrast, smoke dramatically decreased bacterial survival and growth in all parameters measured. Conclusion: Unlike cigarette smoke, flavorless ECIG aerosol has only a small effect on the survival and growth of oral commensal streptococci.

Streptococcus gordonii Challisin protease is required for sensing cell--cell contact with Actinomyces oris

The ability of microorganisms to regulate gene expression is thought to be critical for survival and growth during the development of polymicrobial biofilms such as dental plaque. The commensal dental plaque colonizer, Streptococcus gordonii, responds to cell--cell contact (coaggregation) with Actinomyces oris by regulating >20 genes, including those involved in arginine biosynthesis. We hypothesized that an S. gordonii extracellular protease is critical for sensing by providing amino acids that modulate gene expression. S. gordonii coaggregated strongly with A. oris in buffer, saliva or chemically defined medium (CDM). In wild-type S. gordonii, expression of arginine biosynthesis genes argC and argG increased within two hours' growth in CDM in monocultures, but not following coaggregation with A. oris. By contrast, coaggregation of A. oris with an S. gordonii mutant lacking sgc, encoding the extracellular protease Challisin, resulted in increases in argC and argG gene expression that were similar to monocultures. Genetic complementation of sgc restored the ability of S. gordonii to sense coaggregation with A. oris. Coaggregation enabled growth of S. gordonii in low/no arginine and disruption of sgc did not affect this ability. We propose that extracellular bacterial proteases may be key mediators of cell--cell contact sensing by diverse microbial species.

Antimicrobial activity of mouth rinses against bacteria that initially colonizes dental’s surface

Abstract Introduction Much advertising in mouthwash is conveyed in all media appealing to the anti-plaque effect and rendering a disservice to the community. Mouth rinses are available over-the-count and differ on their compositions and antimicrobial effectiveness. Objective In this study, we evaluated the antimicrobial activity of 35 widely available mouth rinses against bacterial species involved in initiation of dental biofilm – Streptococcus gordonii, Streptococcus mitis, Streptococcus oralis, Streptococcus salivarius, and Streptococcus sanguinis. Material and method The Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of the evaluated mouth rinses were determined according to the Clinical & Laboratory Standards Institute protocols. Data were submitted to Kruskal-Wallis test and Mann-Whitney post hoc (α=0.05). Result About 70% of the mouth rinses achieved high antibacterial activity and 30%, a low antibacterial activity against all the species tested. The most ineffective mouth rinse showed antibacterial activity (MIC) at 1:1 dilution, while the most effective showed activity even at 1:2048 dilution, which may imply prolonged effect in the mouth. About 51% of mouth rinses showed bactericidal activity, and it was verified that cetylpyridinium chloride or chlorhexidine digluconate containing in the formulation were associated with the highest activity. Conclusion Most - but not all - mouth rinses commercially available are effective in inhibiting in vitro initial colonizers of dental surfaces.

Comparison of intraoral biofilm reduction on silver-coated and silver ion-implanted stainless steel bracket material : Biofilm reduction on silver ion-implanted bracket material

PURPOSE

The objective of this in situ study was to quantify the intraoral biofilm reduction on bracket material as a result of different surface modifications using silver ions. In addition to galvanic silver coating and physical vapor deposition (PVD), the plasma immersion ion implantation and deposition (PIIID) procedure was investigated for the first time within an orthodontic application.

MATERIALS AND METHODS

An occlusal splint equipped with differently silver-modified test specimens based on stainless steel bracket material was prepared for a total of 12 periodontally healthy patients and was worn in the mouth for 48 h. The initially formed biofilm was fluorescently stained and a quantitative comparative analysis of biofilm volume, biofilm surface coverage and live/dead distribution of bacteria was performed by confocal laser scanning microscopy (CLSM).

RESULTS

Compared to untreated stainless steel bracket material, the antibacterial effect of the PIIID silver-modified surface was just as significant with regard to reducing the biofilm volume and the surface coverage as the galvanically applied silver layer and the PVD silver coating. Regarding the live/dead distribution, however, the PIIID modification was the only surface that showed a significant increase in the proportion of dead cells compared to untreated bracket material and the galvanic coating.

CONCLUSIONS

Orthodontic stainless steel with a silver-modified surface by PIIID procedure showed an effective reduction in the intraoral biofilm formation compared to untreated bracket material, in a similar manner to PVD and galvanic silver coatings applied to the surface. Additionally, the PIIID silver-modified surface has an increased bactericidal effect.

In vitro and ex vivo systems at the forefront of infection modeling and drug discovery

Bacterial infections and antibiotic resistant bacteria have become a growing problem over the past decade. As a result, the Centers for Disease Control predict more deaths resulting from microorganisms than all cancers combined by 2050. Currently, many traditional models used to study bacterial infections fail to precisely replicate the in vivo bacterial environment. These models often fail to incorporate fluid flow, bio-mechanical cues, intercellular interactions, host-bacteria interactions, and even the simple inclusion of relevant physiological proteins in culture media. As a result of these inadequate models, there is often a poor correlation between in vitro and in vivo assays, limiting therapeutic potential. Thus, the urgency to establish in vitro and ex vivo systems to investigate the mechanisms underlying bacterial infections and to discover new-age therapeutics against bacterial infections is dire. In this review, we present an update of current in vitro and ex vivo models that are comprehensively changing the landscape of traditional microbiology assays. Further, we provide a comparative analysis of previous research on various established organ-disease models. Lastly, we provide insight on future techniques that may more accurately test new formulations to meet the growing demand of antibiotic resistant bacterial infections.

Comparison of initial oral microbiomes of young adults with and without cavitated dentin caries lesions using an in situ biofilm model

Dental caries is caused by acids released from bacterial biofilms. However, the in vivo formation of initial biofilms in relation to caries remains largely unexplored. The aim of this study was to compare the oral microbiome during the initial phase of bacterial colonization for individuals with (CC) and without (NC) cavitated dentin caries lesions. Bovine enamel slabs on acrylic splints were worn by the volunteers (CC: 14, NC: 13) for in situ biofilm formation (2 h, 4 h, 8 h, 1 ml saliva as reference). Sequencing of the V1/V2 regions of the 16S rRNA gene was performed (MiSeq). The relative abundances of individual operational taxonomic units (OTUs) were compared between samples from the CC group and the NC group. Random forests models were furthermore trained to separate the groups. While the overall heterogeneity did not differ substantially between CC and NC individuals, several individual OTUs were found to have significantly different relative abundances. For the 8 h samples, most of the significant OTUs showed higher relative abundances in the CC group, while the majority of significant OTUs in the saliva samples were more abundant in the NC group. Furthermore, using OTU signatures enabled a separation between both groups, with area-under-the-curve (AUC) values of ~0.8. In summary, the results suggest that initial oral biofilms provide the potential to differentiate between CC and NC individuals.

The oral microbiota in colorectal cancer is distinctive and predictive

BACKGROUND AND AIMS

Microbiota alterations are linked with colorectal cancer (CRC) and notably higher abundance of putative oral bacteria on colonic tumours. However, it is not known if colonic mucosa-associated taxa are indeed orally derived, if such cases are a distinct subset of patients or if the oral microbiome is generally suitable for screening for CRC.

METHODS

We profiled the microbiota in oral swabs, colonic mucosae and stool from individuals with CRC (99 subjects), colorectal polyps (32) or controls (103).

RESULTS

Several oral taxa were differentially abundant in CRC compared with controls, for example, Streptococcus and Prevotellas pp. A classification model of oral swab microbiota distinguished individuals with CRC or polyps from controls (sensitivity: 53% (CRC)/67% (polyps); specificity: 96%). Combining the data from faecal microbiota and oral swab microbiota increased the sensitivity of this model to 76% (CRC)/88% (polyps). We detected similar bacterial networks in colonic microbiota and oral microbiota datasets comprising putative oral biofilm forming bacteria. While these taxa were more abundant in CRC, core networks between pathogenic, CRC-associated oral bacteria such as Peptostreptococcus, Parvimonas and Fusobacterium were also detected in healthy controls. High abundance of Lachnospiraceae was negatively associated with the colonisation of colonic tissue with oral-like bacterial networks suggesting a protective role for certain microbiota types against CRC, possibly by conferring colonisation resistance to CRC-associated oral taxa and possibly mediated through habitual diet.

CONCLUSION

The heterogeneity of CRC may relate to microbiota types that either predispose or provide resistance to the disease, and profiling the oral microbiome may offer an alternative screen for detecting CRC.

Oral microbiota in youth with perinatally acquired HIV infection

BACKGROUND

Microbially mediated oral diseases can signal underlying HIV/AIDS progression in HIV-infected adults. The role of the oral microbiota in HIV-infected youth is not known. The Adolescent Master Protocol of the Pediatric HIV/AIDS Cohort Study is a longitudinal study of perinatally HIV-infected (PHIV) and HIV-exposed, uninfected (PHEU) youth. We compared oral microbiome levels and associations with caries or periodontitis in 154 PHIV and 100 PHEU youth.

RESULTS

Species richness and alpha diversity differed little between PHIV and PHEU youth. Group differences in average counts met the significance threshold for six taxa; two Corynebacterium species were lower in PHIV and met thresholds for noteworthiness. Several known periodontitis-associated organisms (Prevotella nigrescens, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, and Filifactor alocis) exhibited expected associations with periodontitis in PHEU youth, associations not observed in PHIV youth. In both groups, odds of caries increased with counts of taxa in four genera, Streptococcus, Scardovia, Bifidobacterium, and Lactobacillus.

CONCLUSIONS

The microbiomes of PHIV and PHEU youth were similar, although PHIV youth seemed to have fewer "health"-associated taxa such as Corynebacterium species. These results are consistent with the hypothesis that HIV infection, or its treatment, may contribute to oral dysbiosis.

Evidence of Early Emergence of the Primary Dentition in a Northern Plains American Indian Population

The purposes of this study were to describe primary tooth emergence in an American Indian (AI) population during the first 36 mo of life to compare 1) patterns of emergence between male and female children and 2) tooth emergence between these AI children and other U.S. ethnic groups. Data were derived from a birth cohort of 239 AI children from a Northern Plains tribe participating in a longitudinal study of early childhood caries, with examination data at target ages of 8, 12, 16, 22, 28, and 36 mo of age (±1 mo). Patterns of emergence in AI children were characterized and sex comparisons accomplished with interval-censored survival methodology. Numbers of erupted teeth in AI children at each age were compared via Kruskal-Wallis tests against those in children of the same age, as drawn from a cross-sectional study of dental caries patterns in Arizona; these comparisons were based on the dental examinations of 547 White non-Hispanic and 677 Hispanic children. Characterization of time to achievement of various milestones-including emergence of the anterior teeth, the first molars, and the complete primary dentition-provided no evidence of sex differences among AI children. AI children had significantly more teeth present at 8 mo (median, 3) than either White non-Hispanic (P < 0.0063) or Hispanic (P < 0.0001) children (median, 2 each). This was also true at 12 mo (P < 0.001; medians, 8 vs. 6 and 7, respectively) and 16 mo (P < 0.001; medians, 12 vs. 11 each). Less pronounced differences were seen at 22 mo (P < 0.0001). White non-Hispanic and Hispanic children did not differ at any time considered (P > 0.05). These results provide evidence of earlier tooth emergence in AI children than in the other 2 ethnicities. Although the underlying etiology of the severity of early childhood caries in AI children is likely to be multifactorial, earlier tooth emergence may be a contributing factor. Knowledge Transfer Statement: The findings of this study have practical implications for practitioners providing childhood oral health care to ethnic groups with early tooth emergence. It may be important to provide parents with information on toothbrushing, dentist visits, and other practices supportive of good oral health as early as possible to protect their children's primary dentition.

Genome analysis and clinical implications of the bacterial communities in early biofilm formation on dental implants restored with titanium or zirconia abutments

This cross-sectional study aimed to identify and quantify up to 42 target species colonizing the early biofilm of dental implants restored with titanium or zirconia abutments. A total of 720 samples from 20 healthy individuals were investigated. Biofilm samples were collected from the peri-implant sulci, inner parts of implants, abutment surfaces and prosthetic crowns over a functioning period of 30 days. Checkerboard DNA-DNA hybridization was used for microbial detection and quantitation. Clinical characteristics (probing depth, bleeding on probing, clinical attachment level and marginal bone loss) were also investigated during the monitoring period. Genome counts were low at the implant loading time point for both the abutment materials, and increased over time. Both the titanium and the zirconia groups presented similar microbial counts and diversity over time, and the microbiota was very similar to that colonizing the remaining teeth. Clinical findings were consistent with a healthy condition with no significant difference regarding marginal bone loss between the two materials.

Full validation of a method for the determination of drugs of abuse in non-mineralized dental biofilm using liquid chromatography-tandem mass spectrometry and application to postmortem samples

Alternative matrices play a major role in postmortem forensic toxicology, especially if common matrices (like body fluids or hair) are not available. Incorporation of illicit and medicinal drugs into non-mineralized dental biofilm (plaque) seems likely but has not been investigated so far. Analysis of plaque could therefore extend the spectrum of potentially used matrices in postmortem toxicology. For this reason, a rapid, simple and sensitive method for the extraction, determination and quantification of ten drugs of abuse from plaque using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and fully validated. Amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), 3,4-methylenedioxyamphetamine (MDA), cocaine, benzoylecgonine, morphine, codeine and 6-acetylmorphine were extracted from 2mg of dried and powdered plaque via ultrasonication with acetonitrile. The extracts were analyzed on a triple-quadrupole linear ion trap mass spectrometer in scheduled multiple reaction monitoring mode (sMRM). The method was fully validated and proved accurate, precise, selective and specific with satisfactory linearity within the calibrated ranges. The lower limit of quantification was 10-15pgmg^-1 for all compounds except for MDA (100pgmg^-1) and amphetamine (200pgmg^-1). The method has been successfully applied to three authentic postmortem samples with known drug history. Amphetamine, MDMA, cocaine, benzoylecgonine, morphine and codeine could be detected in these cases in concentrations ranging from 18pgmg^-1 for cocaine to 1400pgmg^-1 for amphetamine.