Oral microbiome: Unveiling the fundamentals

The dynamic communities of oral microbiome in neonates

The oral microbiome, associated with both oral disease and systemic disease, is in dynamic status along the whole life, and many factors including maternal microbiomes could impact the oral microbiome. While fewer studies have been conducted to study the characteristics of the oral microbiome in neonates and the associated maternal factors. Hence, we collected the microbiome of 15 mother-infant pairs across multiple body sites from birth up to 4 days postpartum and used high-throughput sequencing to characterize the microbiomes in mothers and their neonates. The oral microbiome in the neonates changed obviously during the 4 days after birth. Many bacteria originating from the vagina, skin, and environment disappeared in oral cavity over time, such as Prevotella bivia and Prevotella jejuni. Meanwhile, Staphylococcus epidermidis RP62A phage SP-beta, predominate bacterium in maternal skin microbiome and Streptococcus unclassified, main bacterium in vaginal microbiome, obviously increased in neonatal oral microbiome as time went on. Interestingly, as time progressed, the composition of the oral microbiome in the neonates was more similar to that of the milk microbiome in their mothers. Moreover, we found that the changes in the predominant bacteria in the neonates were in line with those in the neonates exposed to the environment. Together, these data described the sharp dynamics of the oral microbiome in neonates and the importance of maternal efforts in the development of the neonatal microbiome.

Hypothesis of a potential BrainBiota and its relation to CNS autoimmune inflammation

Infectious agents have been long considered to play a role in the pathogenesis of neurological diseases as part of the interaction between genetic susceptibility and the environment. The role of bacteria in CNS autoimmunity has also been highlighted by changes in the diversity of gut microbiota in patients with neurological diseases such as Parkinson's disease, Alzheimer disease and multiple sclerosis, emphasizing the role of the gut-brain axis. We discuss the hypothesis of a brain microbiota, the BrainBiota: bacteria living in symbiosis with brain cells. Existence of various bacteria in the human brain is suggested by morphological evidence, presence of bacterial proteins, metabolites, transcripts and mucosal-associated invariant T cells. Based on our data, we discuss the hypothesis that these bacteria are an integral part of brain development and immune tolerance as well as directly linked to the gut microbiome. We further suggest that changes of the BrainBiota during brain diseases may be the consequence or cause of the chronic inflammation similarly to the gut microbiota.

Salivary Biomarkers in Periodontitis Post Scaling and Root Planing

OBJECTIVES

This study was conducted to evaluate the levels of salivary uric acid and arginase in patients with periodontitis, generalized gingivitis, and in healthy individuals. Then, the effects of non-surgical periodontal therapy on levels of salivary arginase and uric acid were also investigated.

METHODS

A total of 60 subjects were divided into three groups based on periodontal health: group I comprised 20 healthy individuals; group II comprised 20 subjects who had generalized gingivitis; group III comprised 20 subjects who had generalized periodontitis. On day 0, the clinical examination of periodontal status was recorded, following which saliva samples were collected. Group II and group III subjects underwent non-surgical periodontal therapy. These patients were recalled on day 30 to collect saliva samples. The periodontal parameters were reassessed on day 90, and saliva samples were collected for analysis of salivary arginase and uric acid levels.

RESULTS

Group II and group III showed improvement in clinical parameters following non-surgical periodontal therapy on the 90th day. The MGI score, PPD, and CAL showed improvement. On day 0, at baseline, salivary arginase levels in group III and group II were higher than those in healthy subjects, whereas on day 0, salivary uric acid levels in group III and group II were lower than those in healthy subjects. Both on day 0 and day 90, the salivary arginase level showed a positive correlation with the periodontal parameters, whereas the salivary uric acid level was positively correlated with the periodontal parameters on day 90.

CONCLUSION

the level of salivary arginase was a pro-inflammatory marker and a raised level of salivary uric acid was an anti-inflammatory marker following periodontal therapy, suggesting their pivotal role in assessing periodontal status and evaluation of treatment outcome.

Selection of Beneficial Bacterial Strains With Potential as Oral Probiotic Candidates

This study aimed to select beneficial strains from the oral cavity of healthy volunteers and to evaluate these as potential oral probiotic candidates. The selection process was based on the isolation, differentiation, identification, and safety assessment of LAB strains, followed by a series of experiments for the selection of appropriate candidates with beneficial properties. In the screening procedure, 8 isolates from the oral cavity of a Caucasian volunteers were identified as Streptococcus (Str.) salivarius ST48HK, ST59HK, ST61HK, and ST62HK; Lactiplantibacillus plantarum (Lb.) (Lactobacillus plantarum) ST63HK and ST66HK; Latilactobacillus sakei (Lb.) (Lactobacillus sakei) ST69HK; and Lactobacillus (Lb.) gasseri ST16HK based on 16S rRNA sequencing. Physiological and phenotypic tests did not show hemolytic, proteinase, or gelatinase activities, as well as production of biogenic amines. In addition, screening for the presence of efaA, cyt, IS16, esp, asa1, and hyl virulence genes and vancomycin-resistant genes confirmed safety of the studied strains. Moreover, cell-to-cell antagonism indicated that the strains were able to inhibit the growth of tested representatives from the genera Bacillus, Enterococcus, Streptococcus, and Staphylococcus in a strain-specific manner. Various beneficial genes were detected including gad gene, which codes for GABA production. Furthermore, cell surface hydrophobicity levels ranging between 1.58% and 85% were determined. The studied strains have also demonstrated high survivability in a broad range of pH (4.0-8.0). The interaction of the 8 putative probiotic candidates with drugs from different groups and oral hygiene products were evaluated for their MICs. This is to determine if the application of these drugs and hygiene products can negatively affect the oral probiotic candidates. Overall, antagonistic properties, safety assessment, and high rates of survival in the presence of these commonly used drugs and oral hygiene products indicate Str. salivarius ST48HK, ST59HK, ST61HK, and ST62HK; Lb. plantarum ST63HK and ST66HK; Lb. sakei ST69HK; and Lb. gasseri ST16HK as promising oral cavity probiotic candidates.

Healthy microbiome - a mere idea or a sound concept?

Hundreds of studies in last decades have aimed to compare the microbiome of patients suffering from diverse diseases with that of healthy controls. The microbiome-related component was additionally identified in pathophysiology of many diseases formerly considered to depend only on the host physiology. This, however, opens important questions like: "What is the healthy microbiome?" or "Is it possible to define it unequivocally?". In this review, we describe the main hindrances complicating the definition of "healthy microbiome" in terms of microbiota composition. We discuss the human microbiome from the perspective of classical ecology and we advocate for the shift from the stress on microbiota composition to the functions that microbiome ensures for the host. Finally, we propose to leave the concept of ideal healthy microbiome and replace it by focus on microbiome advantageous for the host, which always depends on the specific context like the age, genetics, dietary habits, body site or physiological state.

Evaluation of the Tooth Surface after Irradiation with Diode Laser Applied for Removal of Dental Microorganisms from Teeth of Patients with Gingivitis, Using X-ray Photoelectron (XPS) and Optical Profilometry (OP)

Gingivitis is accompanied by microorganisms, including pathogens, which must be eliminated to speed up the treatment of inflammation. Laser irradiation may be one of the safe methods for reducing tissue contamination on the tooth surface. The aim of the study was the assessment of the tooth surface in patients with gingivitis after the use of a diode laser to eliminate microorganisms living there. In the first stage of the research, microorganisms were isolated (Candida albicans, C. guilliermondii, Escherichia coli, Haemophilus parainfluenzae, Klebsiella oxytoca, Neisseria subflava, Rothia dentocariosa, Rothia mucilaginosa, Streptococcus pneumoniae) from three patients with gingivitis, their identification confirmed using the MALDI-TOF MS technique (matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry). Then, the irradiation process with a diode laser was optimized to a wavelength of 810 nm ± 10 nm in five variants to reduce microorganisms on the tooth. The tooth surface was analyzed by X-ray photoelectron spectroscopy (XPS) and optical profilometry (OP) before and after irradiation. 103 to 106 CFU were detected on a 0.4 cm² tooth area. Nine types of bacteria and two types of fungi dominated among the microorganisms. The laser at the most effective biocidal dose of 25 W/15.000 Hz/10 µs, average = 3.84 W, with three uses after 15 s, increased the reduction of fungi from 57.97% to 93.80%, and bacteria from 30.67% to 100%. This dose also caused a decrease in the degree of oxidation and in the effect of smoothing on the treated surfaces.

Short-term head-down bed rest microgravity simulation alters salivary microbiome in young healthy men

Microgravity influences are prevalent during orbital flight and can adversely affect astronaut physiology. Notably, it may affect the physicochemical properties of saliva and the salivary microbial community. Therefore, this study simulates microgravity in space using a ground-based -6° head-down bed rest (HDBR) test to observe the effects of microgravity on oral salivary secretion function and the salivary microbiome. Sixteen healthy young male volunteers were recruited for the 15-day -6° HDBR test. Non-stimulated whole saliva was collected on day 1 (pre-HDBR), on days 5, 10, and 15 of HDBR, and day 6 of recovery. Salivary pH and salivary flow rate were measured, and the V3-V4 region of the 16S rRNA gene was sequenced and analyzed in 80 saliva samples. The results showed that there were no significant differences in salivary pH, salivary flow rate, and alpha diversity between any two time points. However, beta diversity analysis revealed significant differences between pre-HDBR and the other four time points. After HDBR, the relative abundances of Actinomyces, Parvimonas, Peptostreptococcus, Porphyromonas, Oribacterium, and Capnocytophaga increased significantly, whereas the relative abundances of Neisseria and Haemophilus decreased significantly. However, the relative abundances of Oribacterium and Capnocytophaga did not recover to the pre-HDBR level on day 6 of recovery. Network analysis revealed that the number of relationships between genera decreased, and the positive and negative correlations between genera changed in a complex manner after HDBR and did not reach their original levels on day 6 of recovery. PICRUSt analysis demonstrated that some gene functions of the salivary microbiome also changed after HDBR and remained significantly different from those before HDBR on day 6 of recovery. Collectively, 15 days of -6° HDBR had minimal effect on salivary secretion function but resulted in significant changes in the salivary microbiome, mainly manifested as an increase in oral disease-related bacteria and a decrease in oral health-related commensal bacteria. Further research is required to confirm these oral microbial changes and explore the underlying pathological mechanisms to determine the long-term effects on astronauts embarking on long-duration voyages to outer space.

Prolonged mask wearing does not alter the oral microbiome, salivary flow rate or gingival health status – A pilot study

The COVID-19 pandemic has resulted in the widespread use of N95 respirators and surgical masks, with anecdotal reports among healthcare providers and the public of xerostomia, halitosis, and gingivitis, a consortium of symptoms colloquially termed “mask mouth”. However, this has not been scientifically verified. The aim of this study was to assess changes in salivary flow rate, gingival health status and oral microbiome associated with prolonged mask use. A total of 25 dental students (mean age = 26.36 ± 1.58) were included in the study and evaluated at three time points: T1, at the end of at least 2 months of full-day mask wear (7.26 ± 1.56 hours/day); T2, at the end of a period of minimal mask use (1.13 ± 1.13 hours/day); and T3, at the end of 2-3 weeks of resuming full-day mask wear (6.93 ± 1.80 hours/day). Unstimulated whole saliva (UWS) flow rate, xerostomia (on a quantitative scale of 10), gingival index (GI) and plaque index (PI) were assessed at each time point. The salivary microbiome was characterized using 16S rRNA gene sequencing. Overall, UWS flow rates were normal (mean of 0.679 ml/min) and xerostomia, PI and GI scores were low (Mean of 3.11, 0.33 and 0.69, respectively) with no significant differences as a result of prolonged mask wearing. Similarly, there were no significant microbial changes at a false discovery rate (FDR) ≤ 0.05. However, some trends were identified using a nominal p-value cut-off of ≤ 0.01, namely Gemella sanguinis, Streptococcus sp. Oral taxon 066 and Oral taxon 058 were associated with prolonged mask wear. Trends were also seen by gender, race and age, for example an increase in P. gingivalis and P. intermedia with age. In conclusion, we found no evidence that prolonged mask wear adversely affects oral health. The findings support that the oral microbiome of healthy individuals is resilient.

Laser printing: trends and perspectives

In this paper, I present my personal view on the possible development and applications of laser printing technologies based on laser-induced forward transfer of inorganic and biological materials. Laser printing of micro- and nanoparticles, living cells, and microorganisms are discussed.

Characterization of Oral Veillonella Species in Dental Biofilms in Healthy and Stunted Groups of Children Aged 6-7 Years in East Nusa Tenggara

Impaired development that causes stunting is one of the most common health problems in Indonesia. In particular, the highest number of cases of stunting in Indonesia was reported in the East Nusa Tenggara (NTT) province. Previous studies have shown a tendency for deteriorating oral hygiene in children with a poor nutritional status. In addition, a higher proportion of oral Veillonella has been reported in children with poor oral hygiene. However, the relationship between populations of oral Veillonella and stunting has not been studied before. Therefore, this study aimed to analyze the oral Veillonella profile in the dental biofilms of healthy and stunted children aged 6-7 years. The participants were 60 elementary school students in the Nangapanda District, Ende, NTT, Indonesia. In this study, real-time polymerase chain reaction was used to examine dental biofilm samples from the healthy (n = 31) and stunted (n = 29) groups. The results revealed that seven oral Veillonella species were found in all groups. However, the number of four oral Veillonella species significantly differed between the healthy and stunted groups: V. denticariosi, V. infantium, V. rogosae, and V. tobetsuensis. This is the first study to demonstrate a potential association between oral Veillonella species and stunting in children.

N-Terminal Lysozyme Conjugation to a Cationic Polymer Enhances Antimicrobial Activity and Overcomes Antimicrobial Resistance

Microbial resistance to antibiotics is one of the greatest global healthcare challenges. There is an urgent need to develop effective strategies to overcome antimicrobial resistance. We, herein, report photoinduced in situ growth of a cationic polymer from the N-terminus of lysozyme. The attachment of the cationic polymer improves the proteolytic and thermal stability of lysozyme. Notably, the conjugate can efficiently overcome lysozyme resistance in Gram-positive bacteria and antibiotics-resistance in Gram-negative bacteria, which may be ascribed to the synergistic interactions of lysozyme and the cationic polymer with the bacteria to disrupt their cell membranes. In a rat periodontitis model, the lysozyme-polymer conjugate not only greatly outperforms lysozyme in therapeutic efficacy but also is superior to minocycline hydrochloride, which is the gold standard for periodontitis therapy. These findings may provide an efficient strategy to dramatically enhance the antimicrobial activities of lysozyme and pave a way to overcome antimicrobial resistance.

Periodontitis and Its Inflammatory Changes Linked to Various Systemic Diseases: A Review of Its Underlying Mechanisms

Periodontitis is a chronic inflammatory disease of the gums. The incidence of periodontitis is increasing all over the world. In patients with periodontitis, there is gradual destruction of the periodontal ligament and the alveolar bone, and later, in advanced stages, there is tooth loss. Different microorganisms, the host’s immune response, and various environmental factors interact in the progression of this chronic inflammatory disease. In the present review, we discuss the epidemiology, clinical features, diagnosis, and complications of periodontitis. We also discuss the association of chronic inflammation found in periodontitis with various other systemic diseases, which include cardiovascular, respiratory, diabetes, Alzheimer’s, cancer, adverse pregnancy, and multiple myeloma, and also highlight microbial carcinogenesis and the microRNAs involved. The latest updates on the molecular mechanism, possible biomarkers, and treatment procedures may be beneficial for diagnostic and therapeutic purposes.

Features of the oral microbiome in Japanese elderly people with 20 or more teeth and a non-severe periodontal condition during periodontal maintenance treatment: A cross-sectional study

Introduction

The aim of the present study was to characterize the profile and diversity of the oral microbiome of a periodontally non-severe group with ≥20 teeth in comparison with a severe periodontitis group of elderly Japanese people.

Methods

A total of 50 patients who had ≥20 teeth and aged ≥60 years were recruited, and 34 participants (13 non-severe participants) were analyzed. After oral rinse (saliva after rinsing) sample collection, the V3–V4 regions of the 16S rRNA gene were sequenced to investigate microbiome composition, alpha diversity (Shannon index, Simpson index, richness, and evenness), and beta diversity using principal coordinate analysis (PCoA) based on weighted and unweighted UniFrac distances. A linear discriminant analysis effect size was calculated to identify bacterial species in the periodontally non-severe group.

Results

The periodontally non-severe group showed lower alpha diversity than that of the severe periodontitis group (p <0.05); however, the beta diversities were not significantly different. A higher relative abundance of four bacterial species (Prevotella nanceiensis, Gemella sanguinis, Fusobacterium periodonticum, and Haemophilus parainfluenzae) was observed in the non-severe group than that in the severe periodontitis group.

Conclusion

The oral microbiome in elderly Japanese people with ≥20 teeth and a non-severe periodontal condition was characterized by low alpha diversity and the presence of four bacterial species.

Medication Use Among Patients Reporting Xerostomia of an Academic Dental Clinic

Background:

Global prevalence of xerostomia has been reported at 22% (range 0.01%-45%), negatively impacting oral health, nutrition intake, and quality of life. The causal relationship between xerostomia and medications remains uncertain but greater understanding could guide interventions.

Objective:

To describe the demographic characteristics and medication regimens in patients with xerostomia of an academic dental clinic.

Method:

This is a retrospective academic dental clinic record review from July 1, 2018 to October 27, 2020. Patient records were obtained from the University at Buffalo, School of Dental Medicine. Xerostomia status was determined via query of electronic health records and validated by manual review. Pharmacologic class and xerostomic potential of medications were identified by the Veterans Affairs Drug Classification System and drug compendia, respectively. Predictors of medication use were assessed using a multiple logistic regression model.

Results:

Of 37 403 examined records, 366 (0.98%) were identified as xerostomic. After excluding confounding factors (Sjogren’s and radiation), 275 of 317 patients received at least one xerostomic medication, majority were female (240, 66%) versus male (126, 34%). Mean ± (SD) age was 64.9 ± 15.11 years. A total of 208 (57%) patients were aged ≥65. The median number of total and xerostomic medications were 8 (interquartile range [IQR], 4-12) and 4 (IQR, 2-7), respectively. The 3 most prevalent xerostomic pharmacologic classes were antidepressants (131, 35%), gastric medications (101, 28%), and vitamin D (87, 24%).

Conclusion:

Despite observed prevalence of xerostomia lower than global prevalence, xerostomic medication burden for patients experiencing xerostomia was high. Pharmacist-led interprofessional collaborations should be investigated to reduce xerostomic burden.

Porphyromonas Gingivalis in the Development of Periodontitis: Impact on Dysbiosis and Inflammation

Chronic periodontitis is an inflammatory disease of the dental plaque and affects the soft tissues supporting the tooth. It is one of the most practical oral health issues across the globe and adversely affects the quality of life. In a neutrophil-mediated action, the inflammatory response to periodontitis destroys the periodontal ligaments, gums, the alveolar bone, and the cementum. Some of the most associated invasive pathogens with periodontitis are Porphyromonas Gingivalis, Aggregatibacter actinomycetecomitans, and Fusobacterium nucleatum. Google Scholar and PubMed were used to search the evidence using key terms like 'periodontitis,' 'Porphyromonas Gingivalis,' 'Oral Dysbiosis and Periodontitis,' 'Porphyromonas Gingivalis and Periodontitis,' etc. Only studies were included reviewing the Porphyromonas Gingivalis and its role in periodontitis. It has been observed from several oral pathogens that P. gingivalis has received immense attention due to a strong association between Porphyromonas Gingivalis and periodontal disease. Porphyromonas Gingivalis also disrupts the delicate balance between various members of the oral microbial communities and promotes oral dysbiosis. The dysbiotic state of the oral microbiome is distinct in functional capabilities and shows a higher expression of genes involved in lipopolysaccharide synthesis, energy regulation, and bacterial motility. Certain virulence factors such as gingipains, LPS, and fimbriae also increase the invasion and pathogenicity of Porphyromonas Gingivalis. Its presence in the periodontal tissues increases the secretion of numerous pro-inflammatory mediators such as TNF-α, IL-8, and IL-1β, leading to the destruction of soft gingival tissues and ligaments. Early detection of periodontitis and immediate treatment can prevent soft tissue destruction and dentition loss. In conclusion, details about the oral microbiome, oral dysbiosis, and inflammation may offer new therapeutic options in the future, including a personalized approach and the use of combination therapy.

Purification, crystallization and crystallographic analysis of the PorX response regulator associated with the type IX secretion system

Pathogenic bacteria utilize specialized macromolecular secretion systems to transport virulence factors across membrane(s) and manipulate their infected host. To date, 11 secretion systems have been identified, including the type IX secretion system (T9SS) associated with human, avian and farmed-fish diseases. As a bacterial secretion system, the T9SS also facilitates gliding motility and the degradation of different macromolecules by the secretion of metabolic enzymes in nonpathogenic bacteria. PorX is a highly conserved protein that regulates the transcription of essential T9SS components and additionally mediates the function of T9SS via direct interaction with PorL, the rotary motor protein of the T9SS. PorX is also a member of a two-component system regulatory cascade, where it serves as the response regulator that relays a signal transduced from a conserved sensor histidine kinase, PorY, to a designated sigma factor. Here, the recombinant expression and purification of PorX homologous proteins from the pathogenic bacterium Porphyromonas gingivalis and the nonpathogenic bacterium Flavobacterium johnsoniae are reported. A bioinformatical characterization of the different domains comprising the PorX protein is also provided, and the crystallization and X-ray analysis of PorX from F. johnsoniae are reported.

Polysaccharide Based Implantable Drug Delivery: Development Strategies, Regulatory Requirements, and Future Perspectives

Implantable drug delivery systems advocate a wide array of potential benefits, including effective administration of drugs at lower concentrations and fewer side-effects whilst increasing patient compliance. Amongst several polymers used for fabricating implants, biopolymers such as polysaccharides are known for modulating drug delivery attributes as desired. The review describes the strategies employed for the development of polysaccharide-based implants. A comprehensive understanding of several polysaccharide polymers such as starch, cellulose, alginate, chitosan, pullulan, carrageenan, dextran, hyaluronic acid, agar, pectin, gellan gum is presented. Moreover, biomedical applications of these polysaccharide-based implantable devices along with the recent advancements carried out in the development of these systems have been mentioned. Implants for the oral cavity, nasal cavity, bone, ocular use, and antiviral therapy have been discussed in detail. The regulatory considerations with respect to implantable drug delivery has also been emphasized in the present work. This article aims to provide insights into the developmental strategies for polysaccharide-based implants.

Changes in Oral Microbial Diversity in a Piglet Model of Traumatic Brain Injury

Dynamic changes in the oral microbiome have gained attention due to their potential diagnostic role in neurological diseases such as Alzheimer's disease and Parkinson's disease. Traumatic brain injury (TBI) is a leading cause of death and disability in the United States, but no studies have examined the changes in oral microbiome during the acute stage of TBI using a clinically translational pig model. Crossbred piglets (4-5 weeks old, male) underwent either a controlled cortical impact (TBI, n = 6) or sham surgery (sham, n = 6). The oral microbiome parameters were quantified from the upper and lower gingiva, both buccal mucosa, and floor of the mouth pre-surgery and 1, 3, and 7 days post-surgery (PS) using the 16S rRNA gene. Faith's phylogenetic diversity was significantly lower in the TBI piglets at 7 days PS compared to those of sham, and beta diversity at 1, 3, and 7 days PS was significantly different between TBI and sham piglets. However, no significant changes in the taxonomic composition of the oral microbiome were observed following TBI compared to sham. Further studies are needed to investigate the potential diagnostic role of the oral microbiome during the chronic stage of TBI with a larger number of subjects.

The interplay between Helicobacter pylori and the gut microbiota: An emerging driver influencing the immune system homeostasis and gastric carcinogenesis

The human gut microbiota are critical for preserving the health status because they are required for digestion and nutrient acquisition, the development of the immune system, and energy metabolism. The gut microbial composition is greatly influenced by the colonization of the recalcitrant pathogen Helicobacter pylori (H. pylori) and the conventional antibiotic regimens that follow. H. pylori is considered to be the main microorganism in gastric carcinogenesis, and it appears to be required for the early stages of the process. However, a non-H. pylori microbiota profile is also suggested, primarily in the later stages of tumorigenesis. On the other hand, specific groups of gut microbes may produce beneficial byproducts such as short-chain fatty acids (acetate, butyrate, and propionate) that can modulate inflammation and tumorigenesis pathways. In this review, we aim to present how H. pylori influences the population of the gut microbiota to modify the host immunity and trigger the development of gastric carcinogenesis. We will also highlight the effect of the gut microbiota on immunotherapeutic approaches such as immune checkpoint blockade in cancer treatment to present a perspective for further development of innovative therapeutic paradigms to prevent the progression of H. pylori-induced stomach cancer.

Alternative Antibiotics in Dentistry: Antimicrobial Peptides

The rise of antibiotic resistant bacteria due to overuse and misuse of antibiotics in medicine and dentistry is a growing concern. New approaches are needed to combat antibiotic resistant (AR) bacterial infections. There are a number of methods available and in development to address AR infections. Dentists conventionally use chemicals such as chlorohexidine and calcium hydroxide to kill oral bacteria, with many groups recently developing more biocompatible antimicrobial peptides (AMPs) for use in the oral cavity. AMPs are promising candidates in the treatment of (oral) infections. Also known as host defense peptides, AMPs have been isolated from animals across all kingdoms of life and play an integral role in the innate immunity of both prokaryotic and eukaryotic organisms by responding to pathogens. Despite progress over the last four decades, there are only a few AMPs approved for clinical use. This review summarizes an Introduction to Oral Microbiome and Oral Infections, Traditional Antibiotics and Alternatives & Antimicrobial Peptides. There is a focus on cationic AMP characteristics and mechanisms of actions, and an overview of animal-derived natural and synthetic AMPs, as well as observed microbial resistance.

Matrix Metalloproteinases in Dental and Periodontal Tissues and Their Current Inhibitors: Developmental, Degradational and Pathological Aspects

Objectives: This review article aims to describe some of the roles of Matrix metalloproteinases (MMPs) in enamel, dentine, dental caries, hybrid layer degradation, pulp and periodontal tissues, throwing light on their current inhibitors. The article addresses the potential of MMPs to serve as biomarkers with diagnostic and therapeutic value. Design: The sections of this review discuss MMPs’ involvement in developmental, remodeling, degradational and turnover aspects of dental and periodontal tissues as well as their signals in the pathogenesis, progress of different lesions and wound healing of these tissues. The literature was searched for original research articles, review articles and theses. The literature search was conducted in PubMed and MEDLINE for articles published in the last 20 years. Results: 119 published papers, two textbooks and two doctoral theses were selected for preparing the current review. Conclusions: MMPs are significant proteases, of evident contribution in dental and periapical tissue development, health and disease processes, with promising potential for use as diagnostic and prognostic disease biomarkers. Continuing understanding of their role in pathogenesis and progress of different dental, periapical and periodontal lesions, as well as in dentine-pulp wound healing could be a keystone to future diagnostic and therapeutic regimens.

Variations in oral microbiome and its predictive functions between tumorous and healthy individuals

Introduction. The oral cavity is one of the largest reservoirs of microorganisms and many pathogenic bacteria have been shown to be associated with the aetiology of oral cancers.Gap Statement. Owing to the complexity of oral microbial communities and their unclear relationship with oral cancer, identification of specific bacteria which contribute to oral cancer is a key imperative.Aim. To compare and investigate the variations in the composition of the bacterial microbiome and its functions between patients with oral tumorous lesions and healthy subjects.Methodology. Twenty-seven samples from individuals with oral tumours (five oral benign tumours and 22 oral squamous cell carcinomas) and 15 samples from healthy subjects were collected. Genomic DNA was extracted and the V3-V5 region of the 16S rRNA gene was sequenced. Subsequently, bioinformatic assessment was conducted using QIIME2, PICRUSt and linear discriminant analysis effect size analyses (LEfSe).Results. The oral microbiota was composed mainly of the phyla Proteobacteria (31.76 %, 35.00 %), Bacteroidetes (30.13 %, 25.13 %) and Firmicutes (23.92 %, 17.07 %) in tumorous and healthy individuals, respectively. Neisseria, Prevotella, Fusobacterium, Streptococcus, Capnocytophaga, Veillonella, Haemophilus, Prevotella, Porphyromonas and Leptotrichia were the most abundant genera. Alpha diversity in the tumour group was significantly greater than that in the healthy group (P<0.05). Differential analysis of microbes between groups demonstrated a significantly higher number of Neisseria, Veillonella, Streptococcus, Leptotrichia, Lautropia, Sphingopyxis, Sphingobium, Tannerella, Actinomyces and Rothia in healthy controls compared with the tumour group. However, the genera Treponema, Micrococcus, Pseudomonas, Janthinobacterium, Parvimos, Loktanella, Staphylococcus, Acinetobacter, Catonella, Aggregatibacter and Propionibacterium were significantly higher in the tumour group. Pathways related to cancers, cell motility, environmental adaptation, metabolism and signal transduction were enhanced in the tumour group, while functions associated with immune system diseases, replication, repair and translation were significantly enhanced in the healthy group.Conclusion. Variations in the oral microbiota and its functions showed a correlation with oral tumours. The tumour group showed an increased abundance of some multi-drug-resistant and periodontitis-related pathogens. The significantly altered microbiotas may serve as potential biomarkers or inform combination therapy for oral tumours.

The Mechanistic Pathways of Periodontal Pathogens Entering the Brain: The Potential Role of Treponema denticola in Tracing Alzheimer’s Disease Pathology

Alzheimer’s Disease (AD) is a complex neurodegenerative disease and remains the most common form of dementia. The pathological features include amyloid (Aβ) accumulation, neurofibrillary tangles (NFTs), neural and synaptic loss, microglial cell activation, and an increased blood–brain barrier permeability. One longstanding hypothesis suggests that a microbial etiology is key to AD initiation. Among the various periodontal microorganisms, Porphyromonas gingivalis has been considered the keystone agent to potentially correlate with AD, due to its influence on systemic inflammation. P. gingivalis together with Treponema denticola and Tannerella forsythia belong to the red complex consortium of bacteria advocated to sustain periodontitis within a local dysbiosis and a host response alteration. Since the implication of P. gingivalis in the pathogenesis of AD, evidence has emerged of T. denticola clusters in some AD brain tissue sections. This narrative review explored the potential mode of spirochetes entry into the AD brain for tracing pathology. Spirochetes are slow-growing bacteria, which can hide within ganglia for many years. It is this feature in combination with the ability of these bacteria to evade the hosts’ immune responses that may account for a long lag phase between infection and plausible AD disease symptoms. As the locus coeruleus has direct connection between the trigeminal nuclei to periodontal free nerve endings and proprioceptors with the central nervous system, it is plausible that they could initiate AD pathology from this anatomical region.

Oral Microbiota, Its Equilibrium and Implications in the Pathophysiology of Human Diseases: A Systematic Review

Imbalances of the oral microbiota and dysbiosis have traditionally been linked to the occurrence of teeth and oral diseases. However, recent findings indicate that this microbiota exerts relevant influence in systemic health. Dysbiosis of the oral microbiota is implicated in the apparition and progression of cardiovascular, neurodegenerative and other major human diseases. In fact, the oral microbiota are the second most diverse and largely populated microbiota of the human body and its relationships with systemic health, although widely explored, they still lack of proper integration. The purpose of this systematic review is thus to widely examine the implications of oral microbiota in oral, cardiovascular and neurodegenerative diseases to offer integrative and up-to-date interpretations. To achieve that aim, we identified a total of 121 studies curated in PUBMED from the time interval January 2003–April 2022, which after careful screening resulted in 79 studies included. The reviewed scientific literature provides plausible vias of implication of dysbiotic oral microbiota in systemic human diseases, and encourages further research to continue elucidating the highly relevant and still poorly understood implications of this niche microbiota in systemic health. PROSPERO Registration Number: CRD42022299692. This systematic review follows relevant PRISMA guidelines.

Cross Talk between Synthetic Food Colors (Azo Dyes), Oral Flora, and Cardiovascular Disorders

Synthetic food colors are important ingredients in the food industry. These synthetic food colorants are azo dyes, majorly acidic in nature such as Allura red and Tartrazine. They are present in sweets, carbonated drinks, meat products, and candies to attract the consumers. This review article is an attempt to explain the adverse effects of azo dyes and their association with oral cavities and cardiovascular disorders. These synthetic dyes (azo dyes) have staining effects on dentin. Poor dental care accelerates the bacterial accumulation on the dental crown (Gram-negative bacteria P. gingivalis, T. denticola, and T. forsythia and Gram-positive bacteria Strep. Gordonii), causing the washing of enamel, forming dental plaque. Bacterial pathogens (P. ginigivalis and F. nacleatum) release different chemicals (FadA and Fap2) that bind to protein on the cell by producing an inflammatory response through different line-host defenses, such as Gingival epithelial cells (ECs), Hemi-desmosomes, and desmosomes, which helps the bacterium migration from the cell–cell junction. This makes the junctions slightly open up and makes the whole vessel permeable, through which the bacterium enters into the blood stream line. This leads to different major arteries, such as the carotid artery, and causes the accumulation of plaque in major cardiac arteries, which causes different cardiovascular disorders. These bacterial species present in gums cause cardiovascular diseases, such as ischemic heart disease, coronary artery disease, heart attacks and strokes, and arrhythmias, which can lead to death.

Expression of Macrophage Polarization Markers against the Most Prevalent Serotypes of Aggregatibacter actinomycetemomitans

Aggregatibacter actinomycetemcomitans, a Gram-negative bacterium with seven serotypes (a–g) according to the structure of its LPS, has been defined as one of the most important pathogens in the development of a dysbiotic periodontal biofilm and the onset of periodontitis (an inflammatory chronic disease of the tissues around the teeth), where the serotype b is characterized as the most virulent compared with the other serotypes. The aim of this study was to evaluate the expression of the macrophage polarization markers M0, M1, and M2 against A. actinomycetemcomitans. Methods: THP-1 cells were infected with A. actinomycetemcomitans serotypes a, b, and c. The expression of CD11b, CD4, CD14, and CD68 for M0; IL-6, HLA/DRA, and CXCL10 for M21, and IL-10, CD163, fibronectin-1 or FN1, and CCL17 was evaluated by qPCR at 2 and 24 h after infection. Results: An increase in the expression of these molecules was induced by all serotypes at both times of infection, showing higher levels of expression to the M1 panel at 2 and 24 h compared to other markers. Conclusions: A. actinomycetemcomitans has a role in the macrophage polarization to the M1 phenotype in a non-serotype-dependent manner.

The Oral Microbiome and Its Role in Systemic Autoimmune Diseases: A Systematic Review of Big Data Analysis

Introduction

Despite decades of research, systemic autoimmune diseases (SADs) continue to be a major global health concern and the etiology of these diseases is still not clear. To date, with the development of high-throughput techniques, increasing evidence indicated a key role of oral microbiome in the pathogenesis of SADs, and the alterations of oral microbiome may contribute to the disease emergence or evolution. This review is to present the latest knowledge on the relationship between the oral microbiome and SADs, focusing on the multiomics data generated from a large set of samples.

Methodology

By searching the PubMed and Embase databases, studies that investigated the oral microbiome of SADs, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and Sjögren's syndrome (SS), were systematically reviewed according to the PRISMA guidelines.

Results

One thousand and thirty-eight studies were found, and 25 studies were included: three referred to SLE, 12 referred to RA, nine referred to SS, and one to both SLE and SS. The 16S rRNA sequencing was the most frequent technique used. HOMD was the most common database aligned to and QIIME was the most popular pipeline for downstream analysis. Alterations in bacterial composition and population have been found in the oral samples of patients with SAD compared with the healthy controls. Results regarding candidate pathogens were not always in accordance, but Selenomonas and Veillonella were found significantly increased in three SADs, and Streptococcus was significantly decreased in the SADs compared with controls.

Conclusion

A large amount of sequencing data was collected from patients with SAD and controls in this systematic review. Oral microbial dysbiosis had been identified in these SADs, although the dysbiosis features were different among studies. There was a lack of standardized study methodology for each study from the inclusion criteria, sample type, sequencing platform, and referred database to downstream analysis pipeline and cutoff. Besides the genomics, transcriptomics, proteomics, and metabolomics technology should be used to investigate the oral microbiome of patients with SADs and also the at-risk individuals of disease development, which may provide us with a better understanding of the etiology of SADs and promote the development of the novel therapies.

Association between Vitamin D Receptor Gene Polymorphisms and Periodontal Bacteria: A Clinical Pilot Study

Background: Periodontitis is an inflammatory disease caused by microorganisms involving the supporting tissues of the teeth. Gene variants may influence both the composition of the biofilm in the oral cavity and the host response. The objective of the study was to investigate the potential correlations between the disease susceptibility, the presence and the quantity of periodontopathogenic oral bacterial composition and the VDR gene polymorphisms. Methods: Fifty (50) unrelated periodontal patients and forty-one (41) healthy controls were selected for genomic DNA extraction. DNA concentration was measured and analyzed. The periodontopathogenic bacterial species were identified and quantified using a Real Time PCR performed with species-specific primers and probes. Results: Genotype distribution showed a different distribution between the groups for BsmI rs1544410 genotypes (p = 0.0001) with a prevalence of the G(b) allele in periodontal patients (p = 0.0003). Statistical significance was also found for VDR TaqI rs731236 (p ≤ 0.00001) with a prevalence of the T(T) allele in periodontal patients (p ≤ 0.00001). The average bacterial copy count for the periodontitis group was significantly higher than that of control group. Dividing patients into two groups based on high or low bacterial load, FokI rs2228570 T allele (f) was statistically more represented in patients with high bacterial load. Conclusions: The findings of the study suggest the involvement of the VDR gene BsmI and TaqI polymorphisms in periodontal disease, while FokI and BsmI may be involved in determining an increased presence of periodontopathogens.

Connecting the Human Microbiome and Pancreatic Cancer

Pancreatic cancer is a deadly disease that is increasing in incidence throughout the world. There are no clear causal factors associated with the incidence of pancreatic cancer; however, some correlation to smoking, diabetes and alcohol has been described. Recently, a few studies have linked the human microbiome (oral and gastrointestinal tract) to pancreatic cancer development. A perturbed microbiome has been shown to alter normal cells while promoting cancer-related processes such as increased cell signaling, immune system evasion and invasion. In this article, we will review in detail the alterations within the gut and oral microbiome that have been linked to pancreatic cancer and explore the ability of other microbiomes, such as the lung and skin microbiome, to contribute to disease development. Understanding ways to identify a perturbed microbiome can result in advancements in pancreatic cancer research and allow for prevention, earlier detection and alternative treatment strategies for patients.

The Composition and Functional Capacities of Saliva Microbiota Differ Between Children With Low and High Sweet Treat Consumption

Excess sugar consumption—common in youth—is associated with poor health. Evidence on the relationship between sugar consumption and the oral microbiome, however, remains scarce and inconclusive. We explored whether the diversity, composition, and functional capacities of saliva microbiota differ based on the consumption of select sugary foods and drinks (“sweet treats”). Using 16S rRNA gene sequencing, we characterized saliva microbiota from 11 to 13-year-old children who participated in the Finnish Health in Teens (Fin-HIT) cohort study. The sample comprised children in the lowest (n = 227) and highest (n = 226) tertiles of sweet treat consumption. We compared differences in the alpha diversity (Shannon, inverse Simpson, and Chao1 indices), beta diversity (principal coordinates analysis based on Bray–Curtis dissimilarity), and abundance (differentially abundant operational taxonomic units (OTUs) at the genus level) between these low and high consumption groups. We performed PICRUSt2 to predict the metabolic pathways of microbial communities. No differences emerged in the alpha diversity between low and high sweet treat consumption, whereas the beta diversity differed between groups (p = 0.001). The abundance of several genera such as Streptococcus, Prevotella, Veillonella, and Selenomonas was higher in the high consumption group compared with the low consumption group following false discovery rate correction (p < 0.05). Children with high sweet treat consumption exhibited higher proportions of nitrate reduction IV and gondoate biosynthesis pathways compared with the low consumption group (p < 0.05). To conclude, sweet treat consumption shapes saliva microbiota. Children who consume a high level of sweet treats exhibited different compositions and metabolic pathways compared with children who consume low levels of sweet treats. Our findings reveal novel insights into the relationship between sugary diets and oral microbiota.

Electrospun Membrane Surface Modification by Sonocoating with HA and ZnO:Ag Nanoparticles—Characterization and Evaluation of Osteoblasts and Bacterial Cell Behavior In Vitro

Guided tissue regeneration and guided bone regeneration membranes are some of the most common products used for bone regeneration in periodontal dentistry. The main disadvantage of commercially available membranes is their lack of bone cell stimulation and easy bacterial colonization. The aim of this work was to design and fabricate a new membrane construct composed of electrospun poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) fibers sonocoated with layers of nanoparticles with specific properties, i.e., hydroxyapatite and bimetallic nanocomposite of zinc oxide–silver. Thus, within this study, four different variants of biomaterials were evaluated, namely: poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) biomaterial, poly(D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite biomaterial, poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano zinc oxide–silver biomaterial, and poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite/nano zinc oxide–silver biomaterial. First, it was demonstrated that the wettability of biomaterials—a prerequisite property important for ensuring desired biological response—was highly increased after the sonocoating process. Moreover, it was indicated that biomaterials composed of poly (D,L-lactic acid)/poly (lactic-co-glycolic acid) with or without a nano hydroxyapatite layer allowed proper osteoblast growth and proliferation, but did not have antibacterial properties. Addition of a nano zinc oxide–silver layer to the biomaterial inhibited growth of bacterial cells around the membrane, but at the same time induced very high cytotoxicity towards osteoblasts. Most importantly, enrichment of this biomaterial with a supplementary underlayer of nano hydroxyapatite allowed for the preservation of antibacterial properties and also a decrease in the cytotoxicity towards bone cells, associated with the presence of a nano zinc oxide–silver layer. Thus, the final structure of the composite poly (D,L-lactic acid)/poly (lactic-co-glycolic acid)/nano hydroxyapatite/nano zinc oxide–silver seems to be a promising construct for tissue engineering products, especially guided tissue regeneration/guided bone regeneration membranes. Nevertheless, additional research is needed in order to improve the developed construct, which will simultaneously protect the biomaterial from bacterial colonization and enhance the bone regeneration properties.

Bacterial infections in cancer: A bilateral relationship

Bacteria share a long commensal relationship with the human body. New findings, however, continue to unravel many complexities associated with this old alliance. In the past decades, the dysbiosis of human microbiome has been linked to tumorigenesis, and more recently to spontaneous colonization of existing tumors. The topic, however, remains open for debate as the claims for causative-prevailing dual characteristics of bacteria are mostly based on epidemiological evidence rather than robust mechanistic models. There are also no reviews linking the collective impact of bacteria in tumor microenvironments to the efficacy of cancer drugs, mechanisms of pathogen-initiated cancer and bacterial colonization, personalized nanomedicine, nanotechnology, and antimicrobial resistance. In this review, we provide a holistic overview of the bilateral relationship between cancer and bacteria covering all these aspects. Our collated evidence from the literature does not merely categorize bacteria as cancer causative or prevailing agents, but also critically highlights the gaps in the literature where more detailed studies may be required to reach such a conclusion. Arguments are made in favor of dual drug therapies that can simultaneously co-target bacteria and cancer cells to overcome drug resistance. Also discussed are the opportunities for leveraging the natural colonization and remission power of bacteria for cancer treatment. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Microbiota in health and diseases

The role of microbiota in health and diseases is being highlighted by numerous studies since its discovery. Depending on the localized regions, microbiota can be classified into gut, oral, respiratory, and skin microbiota. The microbial communities are in symbiosis with the host, contributing to homeostasis and regulating immune function. However, microbiota dysbiosis can lead to dysregulation of bodily functions and diseases including cardiovascular diseases (CVDs), cancers, respiratory diseases, etc. In this review, we discuss the current knowledge of how microbiota links to host health or pathogenesis. We first summarize the research of microbiota in healthy conditions, including the gut-brain axis, colonization resistance and immune modulation. Then, we highlight the pathogenesis of microbiota dysbiosis in disease development and progression, primarily associated with dysregulation of community composition, modulation of host immune response, and induction of chronic inflammation. Finally, we introduce the clinical approaches that utilize microbiota for disease treatment, such as microbiota modulation and fecal microbial transplantation.

From Mouth to Brain: Distinct Supragingival Plaque Microbiota Composition in Cerebral Palsy Children With Caries

Children with cerebral palsy (CP) present a higher prevalence and severity of caries. Although researchers have studied multiple risk factors for caries in CP, the role of microorganisms in caries remains one of the critical factors worth exploring. In order to explore the differences in the supragingival plaque microbiota (SPM), supragingival plaque samples were collected from 55 CP children and 23 non-CP children for 16S rRNA sequencing. Distinct SPM composition was found between CP children with severe caries (CPCS) and non-CP children with severe caries (NCPCS). Further subanalysis was also done to identify if there were any differences in SPM among CP children with different degrees of caries, namely, caries-free (CPCF), mild to moderate caries (CPCM), and severe caries (CPCS). After selecting the top 15 most abundant species in all groups, we found that CPCS was significantly enriched for Fusobacterium nucleatum, Prevotella intermedia, Campylobacter rectus, Porphyromonas endodontalis, Catonella morbi, Alloprevotella tannerae, Parvimonas micra, Streptobacillus moniliformis, and Porphyromonas canoris compared to NCPCS. By comparing CPCF, CPCM, and CPCS, we found that the core caries-associated microbiota in CP children included Prevotella, Alloprevotella, Actinomyces, Catonella, and Streptobacillus, while Capnocytophaga and Campylobacter were dental health-associated microbiota in CP children. Alpha diversity analysis showed no significant difference between NCPCS and CPCS, but the latter had a much simpler core correlation network than that of NCPCS. Among CP children, CPCM and CPCF displayed lower bacterial diversity and simpler correlation networks than those of CPCS. In summary, the study showed the specific SPM characteristics of CPCS compared to NCPCS and revealed the core SPM in CP children with different severities of caries (CPCF, CPCM, and CPCS) and their correlation network. Hopefully, the study would shed light on better caries prevention and therapies for CP children. Findings from the current study offer exciting insights that warrant larger cohort studies inclusive of saliva and feces samples to investigate the potential pathogenic role of oral microbiota through the oral-gut-brain axis in CP children with caries.

The Oral-Microbiome-Brain Axis and Neuropsychiatric Disorders: An Anthropological Perspective

In the 21st century, neuropsychiatric disorders (NPDs) are on the rise, yet the causal mechanisms behind this global epidemic remain poorly understood. A key to these unknowns may lie within the vast communities of bacteria, fungi, and viruses in the body (microbiota), which are intimately linked with health and disease. NPDs were recently shown to be connected to gut microbiota, which can communicate with and influence the brain through the Gut-Brain-Axis (GBA). Parallel studies examining oral microbiota and their connections to the brain also suggest that microbes in the mouth can similarly influence NPD outcomes. However, the mechanisms and pathways that illuminate how oral microbiota and brain communicate in NPDs remain unknown. Here, we review identified mechanisms and pathways that oral microbiota use to engage the brain, and we lay the theoretical foundation for an oral-microbiota-brain axis (OMBA). Specifically, we examine established neuroinflammatory and immune system activation responses that underpin interactions between the oral microbiota and the central nervous system (CNS), detailing four specific mechanisms: (1) microbial and metabolite escape, (2) neuroinflammation, (3) CNS signaling, and (4) response to neurohormones. We then scrutinize why including the OMBA, in addition to the GBA, is critically needed to elucidate specific causal relationships between microbial dysbiosis and observed NPD development and progression. Furthermore, we argue for comprehensive, interdisciplinary approaches that integrate lab-based microbiome research and population-level studies that examine the OMBA to improve NPDs. We specifically identify key anthropological perspectives that integrate sociocultural, epidemiological, genetic, and environmental factors that shape the oral microbiome and its interactions with NPDs. Together, future studies of the OMBA in conjunction with interdisciplinary approaches can be used to identify NPD risks and improve outcomes, as well as develop novel intervention and treatment strategies.

Oral-Gut Microbiome Axis in the Pathogenesis of Cancer Treatment-Induced Oral Mucositis

Oral mucositis (OM) is one of the most common and debilitating oral complications of cancer treatments including chemotherapy, radiotherapy, and hematopoietic stem cell transplantation. It is associated with severe pain and difficulties in chewing, swallowing, and speech. This leads to impairment of basic oral functions and could result in unplanned treatment interruption or modification. As such, OM negatively impacts both patients' quality of life as well as tumor prognostic outcomes. Understanding pathways underlying OM pathogenesis help identify new targets for intervention or prevention. The pathophysiology of OM has been widely studied over past decades with several pathways related to oxidative stress, inflammation, and molecular and cellular signaling being implicated. In this mini-review, we will discuss the emerging role of the oral-gut microbiome axis in the development of OM. Particularly, we will elaborate on how the alterations in the oral and gut microbiota as well as intestinal dysfunction caused by cancer treatments could contribute to the pathogenesis of OM. Further, we will briefly discuss the potential methods for targeting the oral-gut microbiome axis to improve OM outcomes.

Oral Microbiome: Getting to Know and Befriend Neighbors, a Biological Approach

The oral microbiome, forming a biofilm that covers the oral structures, contains a high number of microorganisms. Biofilm formation starts from the salivary pellicle that allows bacterial adhesion-colonization-proliferation, co-aggregation and biofilm maturation in a complex microbial community. There is a constant bidirectional crosstalk between human host and its oral microbiome. The paper presents the fundamentals regarding the oral microbiome and its relationship to modulator factors, oral and systemic health. The modern studies of oral microorganisms and relationships with the host benefits are based on genomics, transcriptomics, proteomics and metabolomics. Pharmaceuticals such as antimicrobials, prebiotics, probiotics, surface active or abrasive agents and plant-derived ingredients may influence the oral microbiome. Many studies found associations between oral dysbiosis and systemic disorders, including autoimmune diseases, cardiovascular, diabetes, cancers and neurodegenerative disorders. We outline the general and individual factors influencing the host-microbial balance and the possibility to use the analysis of the oral microbiome in prevention, diagnosis and treatment in personalized medicine. Future therapies should take in account the restoration of the normal symbiotic relation with the oral microbiome.

Does the Amniotic Fluid of Mice Contain a Viable Microbiota?

The existence of an amniotic fluid microbiota (i.e., a viable microbial community) in mammals is controversial. Its existence would require a fundamental reconsideration of fetal in utero exposure to and colonization by microorganisms and the role of intra-amniotic microorganisms in fetal immune development as well as in pregnancy outcomes. In this study, we determined whether the amniotic fluid of mice harbors a microbiota in late gestation. The profiles of the amniotic fluids of pups located proximally or distally to the cervix were characterized through quantitative real-time PCR, 16S rRNA gene sequencing, and culture (N = 21 dams). These profiles were compared to those of technical controls for bacterial and DNA contamination. The load of 16S rRNA genes in the amniotic fluid exceeded that in controls. Additionally, the 16S rRNA gene profiles of the amniotic fluid differed from those of controls, with Corynebacterium tuberculostearicum being differentially more abundant in amniotic fluid profiles; however, this bacterium was not cultured from amniotic fluid. Of the 42 attempted bacterial cultures of amniotic fluids, only one yielded bacterial growth – Lactobacillus murinus. The 16S rRNA gene of this common murine-associated bacterium was not detected in any amniotic fluid sample, suggesting it did not originate from the amniotic fluid. No differences in the 16S rRNA gene load, 16S rRNA gene profile, or bacterial culture were observed between the amniotic fluids located Proximally and distally to the cervix. Collectively, these data indicate that, although there is a modest DNA signal of bacteria in murine amniotic fluid, there is no evidence that this signal represents a viable microbiota. While this means that amniotic fluid is not a source of microorganisms for in utero colonization in mice, it may nevertheless contribute to fetal exposure to microbial components. The developmental consequences of this observation warrant further investigation.

Early life inter-kingdom interactions shape the immunological environment of the airways

BACKGROUND

There is increasing evidence that the airway microbiome plays a key role in the establishment of respiratory health by interacting with the developing immune system early in life. While it has become clear that bacteria are involved in this process, there is a knowledge gap concerning the role of fungi. Moreover, the inter-kingdom interactions that influence immune development remain unknown. In this prospective exploratory human study, we aimed to determine early post-natal microbial and immunological features of the upper airways in 121 healthy newborns.

RESULTS

We found that the oropharynx and nasal cavity represent distinct ecological niches for bacteria and fungi. Breastfeeding correlated with changes in microbiota composition of oropharyngeal samples with the greatest impact upon the relative abundance of Streptococcus species and Candida. Host transcriptome profiling revealed that genes with the highest expression variation were immunological in nature. Multi-omics factor analysis of host and microbial data revealed unique co-variation patterns.

CONCLUSION

These data provide evidence of a diverse multi-kingdom microbiota linked with local immunological characteristics in the first week of life that could represent distinct trajectories for future respiratory health.

TRIAL REGISTRATION

NHS Health Research Authority, IRAS ID 199053. Registered 5 Oct 2016. https://www.hra.nhs.uk/planning-and-improving-research/application-summaries/research-summaries/breathing-together/ Video abstract.

Effects of Antibiotic Use on Saliva Antibody Content and Oral Microbiota in Sprague Dawley Rats

Antibiotics are often used to treat systemic diseases not associated with the oral cavity. This application of antibiotics may affect the healthy oral microbiota community, as it destroys the balance between specific bacterial populations throughout the ecosystem and may lead to dysbacteriosis. We hypothesized that the effects on antibiotics on oral microbiota regulation and function would affect antibody content in saliva, depending on the antibiotic type. To address this, a total of 24 Sprague Dawley rats (divided into 4 cages, 6 per pen) were administered amoxicillin (AMX), spiramycin (SP), metronidazole (MTZ), or water (control) daily for 14 days (gavage). After treatment was completed, high-throughput sequencing of 16S rRNA genes was used to determine changes in the composition, metabolic function, and diversity of oral microbiota in the rats. Enzyme-linked immunosorbent assay was used to detect antibodies in saliva, including SIgA, IgG, and IgM. Results showed that AMX, MTZ, and SP significantly affected oral microbiota composition, diversity, and metabolic function in rats. AMX induced substantial changes in the rat salivary antibody concentrations. At the genus level, the relative abundance of Rothia and Haemophilus was higher in the AMX group than in the other groups. In conclusion, antibiotics-induced changes in oral microbiota populations may be associated with changes in salivary antibody concentrations. However, the specific interaction mechanisms remain unknown, and it is still unclear whether significant changes in the oral microbiota cause changes in salivary antibody concentrations or vice versa.

Why Are Bifidobacteria Important for Infants?

The presence of Bifidobacterium species in the maternal vaginal and fecal microbiota is arguably an evolutionary trait that allows these organisms to be primary colonizers of the newborn intestinal tract. Their ability to utilize human milk oligosaccharides fosters their establishment as core health-promoting organisms throughout life. A reduction in their abundance in infants has been shown to increase the prevalence of obesity, diabetes, metabolic disorder, and all-cause mortality later in life. Probiotic strains have been developed as supplements for premature babies and to counter some of these ailments as well as to confer a range of health benefits. The ability to modulate the immune response and produce short-chain fatty acids, particularly acetate and butyrate, that strengthen the gut barrier and regulate the gut microbiome, makes Bifidobacterium a core component of a healthy infant through adulthood.

A Narrative Review on Oral and Periodontal Bacteria Microbiota Photobiomodulation, through Visible and Near-Infrared Light: From the Origins to Modern Therapies

Photobiomodulation (PBM) consists of a photon energy transfer to the cell, employing non-ionizing light sources belonging to the visible and infrared spectrum. PBM acts on some intrinsic properties of molecules, energizing them through specific light wavelengths. During the evolution of life, semiconducting minerals were energized by sun radiation. The molecules that followed became photoacceptors and were expressed into the first proto-cells and prokaryote membranes. Afterward, the components of the mitochondria electron transport chain influenced the eukaryotic cell physiology. Therefore, although many organisms have not utilized light as an energy source, many of the molecules involved in their physiology have retained their primordial photoacceptive properties. Thus, in this review, we discuss how PBM can affect the oral microbiota through photo-energization and the non-thermal effect of light on photoacceptors (i.e., cytochromes, flavins, and iron-proteins). Sometimes, the interaction of photons with pigments of an endogenous nature is followed by thermal or photodynamic-like effects. However, the preliminary data do not allow determining reliable therapies but stress the need for further knowledge on light-bacteria interactions and microbiota management in the health and illness of patients through PBM.

Efficacy of bakuchiol-garlic combination against virulent genes of Candida albicans

Background

Polymicrobial biofilms are notorious for causing intraoral tissue destruction. Streptococcus sanguinis and Streptococcus mitis, commensals of oral cavities, have been found co-existing with C. albicans in resistant oral infections. There is an urgent need to find alternative treatment options. This study aims to assess the efficacy of garlic (G) and bakuchiol (Bk) combination against candida virulent genes and their subsequently secreted proteins.

Methods

In vitro single species biofilms of C. albicans, and mixed species biofilms formed in combination with streptococci were exposed to bakuchiol and garlic extract (Bk+G). Gene expression of agglutinin-like sequence (ALS1), (ALS3), adhesin-like wall proteins (HWP1) and aspartyl proteinases (SAP5) were determined using qPCR and their subsequent proteins were assessed through Western blotting.

Results

Virulent genes were significantly downregulated in single species biofilms when they were treated with Bk+G combination. However, Bk+G did not have significant effect on ALS1 and HWP1 gene in polymicrobial biofilms. ALS3 and SAP5 were significantly downregulated in Bk+G treated polymicrobial biofilm. Similar results were portrayed in Western blotting.

Conclusion

Bk+G combination exhibited antimicrobial effects against single and mixed species biofilms. The findings might provide insights for treating resistant candida infections. This combination could potentially serve as an herbal alternative to traditional antifungals following further research.

Armed to the Teeth-The Oral Mucosa Immunity System and Microbiota

The oral cavity is inhabited by a wide spectrum of microbial species, and their colonization is mostly based on commensalism. These microbes are part of the normal oral flora, but there are also opportunistic species that can cause oral and systemic diseases. Although there is a strong exposure to various microorganisms, the oral mucosa reduces the colonization of microorganisms with high rotation and secretion of various types of cytokines and antimicrobial proteins such as defensins. In some circumstances, the imbalance between normal oral flora and pathogenic flora may lead to a change in the ratio of commensalism to parasitism. Healthy oral mucosa has many important functions. Thanks to its integrity, it is impermeable to most microorganisms and constitutes a mechanical barrier against their penetration into tissues. Our study aims to present the role and composition of the oral cavity microbiota as well as defense mechanisms within the oral mucosa which allow for maintaining a balance between such numerous species of microorganisms. We highlight the specific aspects of the oral mucosa protecting barrier and discuss up-to-date information on the immune cell system that ensures microbiota balance. This study presents the latest data on specific tissue stimuli in the regulation of the immune system with particular emphasis on the resistance of the gingival barrier. Despite advances in understanding the mechanisms regulating the balance on the microorganism/host axis, more research is still needed on how the combination of these diverse signals is involved in the regulation of immunity at the oral mucosa barrier.

Assessing the drug resistance profiles of oral probiotic lozenges

Background

Probiotic lozenges have been developed to harvest the benefits of probiotics for oral health, but their long-term consumption may encourage the transfer of resistance genes from probiotics to commensals, and eventually to disease-causing bacteria.

Aim

To screen commercial probiotic lozenges for resistance to antibiotics, characterize the resistance determinants, and examine their transferability in vitro.

Results

Probiotics of all lozenges were resistant to glycopeptide, sulfonamide, and penicillin antibiotics, while some were resistant to aminoglycosides and cephalosporins. High minimum inhibitory concentrations (MICs) were detected for streptomycin (>128 µg/mL) and chloramphenicol (> 512 µg/mL) for all probiotics but only one was resistant to piperacillin (MIC = 32 µg/mL). PCR analysis detected erythromycin (erm(T), ermB or mefA) and fluoroquinolone (parC or gyr(A)) resistance genes in some lozenges although there were no resistant phenotypes. The dfrD, cat-TC, vatE, aadE, vanX, and aph(3")-III or ant(2")-I genes conferring resistance to trimethoprim, chloramphenicol, quinupristin/dalfopristin, vancomycin, and streptomycin, respectively, were detected in resistant probiotics. The rifampicin resistance gene rpoB was also present. We found no conjugal transfer of streptomycin resistance genes in our co-incubation experiments.

Conclusion

Our study represents the first antibiotic resistance profiling of probiotics from oral lozenges, thus highlighting the health risk especially in the prevailing threat of drug resistance globally.

The Impact of Mouthwash on the Oropharyngeal Microbiota of Men Who Have Sex with Men: a Substudy of the OMEGA Trial

Mouthwash is a commonly used product and has been proposed as an alternative intervention to prevent gonorrhea transmission. However, the long-term effects of mouthwash on the oral microbiota are largely unknown. We investigated the impact of 12 weeks of daily mouthwash use on the oropharyngeal microbiota in a subset of men who have sex with men who participated in a randomized trial comparing the efficacy of two alcohol-free mouthwashes for the prevention of gonorrhea. We characterized the oropharyngeal microbiota using 16S rRNA gene sequencing of tonsillar fossae samples collected before and after 12 weeks of daily use of Listerine mouthwash or Biotène dry mouth oral rinse. Permutational multivariate analysis of variance (PERMANOVA) was used to assess differences in oropharyngeal microbiota composition following mouthwash use. Differential abundance testing was performed using ALDEx2, with false-discovery rate correction. A total of 306 samples from 153 men were analyzed (Listerine, n = 78 and Biotène, n = 75). There was no difference in the overall structure of the oropharyngeal microbiota following Listerine or Biotène use (PERMANOVA P = 0.413 and P = 0.331, respectively). Although no bacterial taxa were significantly differentially abundant following Listerine use, we observed a small but significant decrease in the abundance of both Streptococcus and Leptotrichia following Biotène use. Overall, our findings suggest that daily use of antiseptic mouthwash has minimal long-term effects on the composition of the oropharyngeal microbiota.

IMPORTANCE Given the role of the oral microbiota in human health, it is important to understand if and how external factors influence its composition. Mouthwash use is common in some populations, and the use of antiseptic mouthwash has been proposed as an alternative intervention to prevent gonorrhea transmission. However, the long-term effect of mouthwash use on the oral microbiota composition is largely unknown. We found that daily use of two different commercially available mouthwashes had limited long-term effects on the composition of the oropharyngeal microbiota over a 12-week period. The results from our study and prior studies highlight that different mouthwashes may differentially affect the oral microbiome composition and that further studies are needed to determine if mouthwash use induces short-term changes to the oral microbiota that may have detrimental effects.

Mesenchymal Stromal/Stem Cells-Derived Exosomes as an Antimicrobial Weapon for Orodental Infections

The oral cavity as the second most various microbial community in the body contains a broad spectrum of microorganisms which are known as the oral microbiome. The oral microbiome includes different types of microbes such as bacteria, fungi, viruses, and protozoa. Numerous factors can affect the equilibrium of the oral microbiome community which can eventually lead to orodental infectious diseases. Periodontitis, dental caries, oral leukoplakia, oral squamous cell carcinoma are some multifactorial infectious diseases in the oral cavity. In defending against infection, the immune system has an essential role. Depending on the speed and specificity of the reaction, immunity is divided into two different types which are named the innate and the adaptive responses but also there is much interaction between them. In these responses, different types of immune cells are present and recent evidence demonstrates that these cell types both within the innate and adaptive immune systems are capable of secreting some extracellular vesicles named exosomes which are involved in the response to infection. Exosomes are 30-150 nm lipid bilayer vesicles that consist of variant molecules, including proteins, lipids, and genetic materials and they have been associated with cell-to-cell communications. However, some kinds of exosomes can be effective on the pathogenicity of various microorganisms and promoting infections, and some other ones have antimicrobial and anti-infective functions in microbial diseases. These discrepancies in performance are due to the origin of the exosome. Exosomes can modulate the innate and specific immune responses of host cells by participating in antigen presentation for activation of immune cells and stimulating the release of inflammatory factors and the expression of immune molecules. Also, mesenchymal stromal/stem cells (MSCs)-derived exosomes participate in immunomodulation by different mechanisms. Ease of expansion and immunotherapeutic capabilities of MSCs, develop their applications in hundreds of clinical trials. Recently, it has been shown that cell-free therapies, like exosome therapies, by having more advantages than previous treatment methods are emerging as a promising strategy for the treatment of several diseases, in particular inflammatory conditions. In orodental infectious disease, exosomes can also play an important role by modulating immunoinflammatory responses. Therefore, MSCs-derived exosomes may have potential therapeutic effects to be a choice for controlling and treatment of orodental infectious diseases.

Oral microbiota and periodontitis severity among Hispanic adults

Background

Periodontitis, one of the most common bacterial infections characterized by chronic inflammation, is also known to be a risk factor for chronic conditions, including cardiovascular disease and cancer. This inflammation is driven by an altered microbiota with an increase in pathogenic bacteria. We evaluated the association between oral microbiota and periodontitis severity in high-risk Hispanics.

Method

This cross-sectional study recruited 134 sexually active participants aged 21 to 49 years old from STI Clinics in Puerto Rico. A periodontal examination, saliva collection, and an interviewer-administered questionnaire were performed. Periodontal severity was categorized as: having no disease, mild, and moderate/severe and BOP and tooth loos was noted. Saliva samples were collected for genomic DNA extraction, downstream 16S rDNA amplification sequencing, and bioinformatics analyses.

Results

The structure, composition, and diversity of bacterial communities differed significantly according to periodontal severity. The richness and overall diversity also differed between participants without periodontitis and participants with some level of periodontal disease. A higher abundance of Prevotella, Veillonella, or Treponema was attributed to periodontal disease and Aggregatibacter to severe bleeding on probing, while Neisseria was found in higher abundance in healthy participants, decreasing its levels with drinking, smoking, and oral sex practices.

Conclusions

Our findings indicate that dysbiosis occurs as periodontal disease progresses, and both alcohol consumption and smoking habits pose risk factors for oral dysbiosis. These results are of public health and clinical impact, as several bacteria identified could serve in the future as biomarkers for periodontitis and oral cancer risk.

Mucosal immunology of the ocular surface

The eye is a sensory organ exposed to the environment and protected by a mucosal tissue barrier. While it shares a number of features with other mucosal tissues, the ocular mucosal system, composed of the conjunctiva, Meibomian glands, and lacrimal glands, is specialized to address the unique needs of (a) lubrication and (b) host defense of the ocular surface. Not surprisingly, most challenges, physical and immunological, to the homeostasis of the eye fall into those two categories. Dry eye, a dysfunction of the lacrimal glands and/or Meibomian glands, which can both cause, or arise from, sensory defects, including those caused by corneal herpes virus infection, serve as examples of these perturbations and will be discussed ahead. To preserve vision, dense neuronal and immune networks sense various stimuli and orchestrate responses, which must be tightly controlled to provide protection, while simultaneously minimizing collateral damage. All this happens against the backdrop of, and can be modified by, the microorganisms that colonize the ocular mucosa long term, or that are simply transient passengers introduced from the environment. This review will attempt to synthesize the existing knowledge and develop trends in the study of the unique mucosal and immune elements of the ocular surface.

Autophagy in aging-related oral diseases

Autophagy is an intracellular degradation mechanism that allows recycling of organelles and macromolecules. Autophagic function increases metabolite availability modulating metabolic pathways, differentiation and cell survival. The oral environment is composed of several structures, including mineralized and soft tissues, which are formed by complex interactions between epithelial and mesenchymal cells. With aging, increased prevalence of oral diseases such as periodontitis, oral cancer and periapical lesions are observed in humans. These aging-related oral diseases are chronic conditions that alter the epithelial-mesenchymal homeostasis, disrupting the oral tissue architecture affecting the quality of life of the patients. Given that autophagy levels are reduced with age, the purpose of this review is to discuss the link between autophagy and age-related oral diseases.