Oral microbial habitat a dynamic entity

Re-framing the importance of Group B Streptococcus as a gut-resident pathobiont

Streptococcus agalactiae (Group B Streptococcus, GBS) is a Gram-positive bacterial species that causes disease in humans across the lifespan. While antibiotics are used to mitigate GBS infections, it is evident that antibiotics disrupt human microbiomes (which can predispose people to other diseases later in life), and antibiotic resistance in GBS is on the rise. Taken together, these unintended negative impacts of antibiotics highlight the need for precision approaches for minimizing GBS disease. One possible approach involves selectively depleting GBS in its commensal niches before it can cause disease at other body sites or be transmitted to at-risk individuals. One understudied commensal niche of GBS is the adult gastrointestinal (GI) tract, which may predispose colonization at other body sites in individuals at risk for GBS disease. However, a better understanding of the host-, microbiome-, and GBS-determined variables that dictate GBS GI carriage is needed before precise GI decolonization approaches can be developed. In this review, we synthesize current knowledge of the diverse body sites occupied by GBS as a pathogen and as a commensal. We summarize key molecular factors GBS utilizes to colonize different host-associated niches to inform future efforts to study GBS in the GI tract. We also discuss other GI commensals that are pathogenic in other body sites to emphasize the broader utility of precise de-colonization approaches for mitigating infections by GBS and other bacterial pathogens. Finally, we highlight how GBS treatments could be improved with a more holistic understanding of GBS enabled by continued GI-focused study.

Microbial corrosion of metallic biomaterials in the oral environment

A wide variety of microorganisms have been closely linked to metal corrosion in the form of adherent surface biofilms. Biofilms allow the development and maintenance of locally corrosive environments and/or permit direct corrosion including pitting corrosion. The presence of numerous genetically distinct microorganisms in the oral environment poses a threat to the integrity and durability of the surface of metallic prostheses and implants used in routine dentistry. However, the association between oral microorganisms and specific corrosion mechanisms is not clear. It is of practical importance to understand how microbial corrosion occurs and the associated risks to metallic materials in the oral environment. This knowledge is also important for researchers and clinicians who are increasingly concerned about the biological activity of the released corrosion products. Accordingly, the main goal was to comprehensively review the current literature regarding oral microbiologically influenced corrosion (MIC) including characteristics of biofilms and of the oral environment, MIC mechanisms, corrosion behavior in the presence of oral microorganisms and potentially mitigating technologies. Findings included that oral MIC has been ascribed mostly to aggressive metabolites secreted during microbial metabolism (metabolite-mediated MIC). However, from a thermodynamic point of view, extracellular electron transfer mechanisms (EET-MIC) through pili or electron transfer compounds cannot be ruled out. Various MIC mitigating methods have been demonstrated to be effective in short term, but long term evaluations are necessary before clinical applications can be considered. Currently most in-vitro studies fail to simulate the complexity of intraoral physiological conditions which may either reduce or exacerbate corrosion risk, which must be addressed in future studies. STATEMENT OF SIGNIFICANCE: A thorough analysis on literature regarding oral MIC (microbiologically influenced corrosion) of biomedical metallic materials has been carried out, including characteristics of oral environment, MIC mechanisms, corrosion behaviors in the presence of typical oral microorganisms and potential mitigating methods (materials design and surface design). There is currently a lack of mechanistic understanding of oral MIC which is very important not only to corrosion researchers but also to dentists and clinicians. This paper discusses the significance of biofilms from a biocorrosion perspective and summarizes several aspects of MIC mechanisms which could be caused by oral microorganisms. Oral MIC has been closely associated with not only the materials research but also the dental/clinical research fields in this work.

Assessment of salivary microbiota profile as a potential diagnostic tool for pediatric celiac disease

The association between oral dysbiosis and celiac disease (CD) remains poorly understood, as does the impact of CD-associated dysbiosis on disease development or exacerbation. This study aims to investigate alterations in salivary microbial composition among children with CD. In this cross-sectional study, saliva samples from 12 children with active CD (A-CD group), 14 children with CD on a gluten-free diet (GFD), and 10 healthy control (HC) children were analyzed using DNA sequencing targeting the 16S ribosomal RNA. Both patients in A-CD and GFD groups showed a significant increase (p = 0.0001) in the Bacteroidetes phylum, while the Actinobacteria phylum showed a significant decrease (p = 0.0001). Notably, the Rothia genus and R.aeria also demonstrated a significant decrease (p = 0.0001) within the both CD groups as compare to HC. Additionally, the control group displayed a significant increase (p = 0.006) in R.mucilaginosa species compared to both CD patient groups. Distinct bacterial strains were abundant in the saliva of patients with active CD, indicating a unique composition of the salivary microbiome in individuals with CD. These findings suggest that our approach to assessing salivary microbiota changes may contribute to developing noninvasive methods for diagnosing and treating CD.

Bacterial Protein Signatures Identified in Porphyromonas gingivalis Containing-Autophagic Vacuoles Reveal Co-Evolution Between Oral Red/Orange Complex Bacteria and Gut Bacteria

Modern oral bacterial species present as a concoction of commensal and opportunistic pathogens originating from their evolution in humans. Due to the intricate colonization mechanisms shared amongst oral and gut bacteria, these bacteria have likely evolved together to establish and adapt in the human oro-digestive tract, resulting in the transfer of genetic information. Our liquid chromatography-with-tandem-mass-spectrometry (LC-MS-MS) analyses have revealed protein signatures, Elongation Factor Tu, RagB/SusD nutrient uptake outer membrane protein and DnaK, specifically from Porphyromonas gingivalis -containing autophagic vacuoles isolated from the infected human primary gingival epithelial cells. Interestingly, our Mass-Spectrometry analysis reported similar proteins from closely related oral bacteria, Tannerella forsythia and Prevotella intermedia . In our phylogenetic study of these key protein signatures, we have established that pathogenic oral bacteria share extensive relatedness to each other and gut resident bacteria. We show that in the virulence factors identified from gut bacteria, Elongation Factor Tu and DnaK, there are several structural similarities and conservations with proteins from oral pathogenic bacteria. There are also major similarities in the RagB/SusD proteins of oral bacteria to prominent gut bacteria. These findings not only highlight the shared virulence mechanisms amongst oral bacterial pathogens/pathobionts but also gut bacteria and elucidate their co-evolutions in the human host.

Oral microbiota in human health and disease: A perspective

The evolution of medical knowledge about oral microbiota has increased awareness of its important role for the entire human body health. A wide range of microbial species colonizing the oral cavity interact both with each other and with their host through complex pathways. Usually, these interactions lead to a harmonious coexistence (i.e. eubiosis). However, several factors - including diet, poor oral hygiene, tobacco smoking, and certain medications, among others - can disrupt this weak homeostatic balance (i.e. dysbiosis) with potential implications on both oral (i.e. development of caries and periodontal disease) and systemic health. This article is thus aimed at providing an overview on the importance of oral microbiota in mediating several physiological and pathological conditions affecting human health. In this context, strategies based on oral hygiene and diet as well as the role of probiotics supplementation are discussed.

Incidence and prevalence of oral candidal colonization in patients with cleft lip and palate

Aims and Objectives

This study aims to assess and compare the incidence and rate of oral candidal colonization in patients with cleft lip and palate and collate it with healthy individuals. The objectives of this study were to evaluate the factors that may affect the incidence, rate, and polycolonity of colonization of oral Candida species in patients with cleft lip and palate (CLP) as compared to healthy individuals.

Materials and Methods

The current prospective study involved the collection and assessment of oral samples from 50 CLP patients and compared it with oral samples from 50 healthy individuals. Colonies of Candida albicans and other Candida species were identified by using germ tube test and differential chromogenic media. Assessment of the distribution trend of various Candida species and their variation based on age, gender, type of cleft, number of surgeries, and oral hygiene status were recorded.

Results

A highly significant (P value < 0.001) statistical difference was seen in the oral carriage rate of Candida species between the two groups with values more in the study group (60.75 ± 71.43) than in controls (1.62 ± 2.22). Individually comparing the different Candida species, significant difference in presence of C albicans (P value = 0.004), C parapsilosis (P value = 0.015), and C dubliensis (P value = 0.027) was seen as compared to other species. In the context of the type of cleft and the presence of Candida species Candida albicans was the most prevalent in patients with the cleft alveolus (60.0% n = 15), unilateral CLP (66.7% n = 8), and bilateral CLP (100.0% n = 3) respectively. Nonsignificant variation in prevalence was seen in the various fungal species based on an individual's gender and oral hygiene and the number of surgeries status was observed.

Conclusion

The anatomical alteration in the oral cavity of patients with CLP contributes to the high incidence and prevalence of Candida species.

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.

Evaluation of flexural strength of bulk-fill composite resin after immersion in fruit juices: An in vitro study

Resin-based composites are increasingly employed in dental restorations due to their esthetics. Flexural strength is the characteristic feature of a substance, and it can be described as the stress present in the material just before it renders in a flexure test. The purpose of this study was to determine the flexural strength of a bulk-fill composite following immersion in fruit juices. Ten samples of bulk-fill type composite filling material were created, with four samples from Restofill (Group 1) and four samples from Ivoclar Vivadent (Group 2). Out of which, four specimens of each brand were included for immersion in fruit juices; two specimens were kept as control. The eight samples were put through a flexural strength test, with four remaining as controls, before being measured for maximum force and displacement on the Instron E3000 universal testing equipment. SPSS version 23 (IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp.) was used to examine the calculated flexural strength. The composite Ivoclar has a mean flexural strength of 20.52, whereas the composite Restofill has a mean flexural strength of 20.55. The P value for the independent sample t-test between the two groups, Ivoclar and Restofill, was 0.089 (>0.05), which is statistically insignificant. It is clear from this research that the bulk-fill composite resin Ivoclar has a low flexural strength when compared to the sample Restofill after immersion in fruit juices.

Role of Probiotics in Human Health

Certain bacteria, known as probiotics, have had a vastly beneficial effect on people's health; considering their benefits they have been mixed with a wide variety of foods for several decades now. The ability of probiotics to modify the immunological response of the host, antagonize pathogenic microbes, or compete for adhesion sites with pathogenic microorganisms is related to the action of probiotics against microorganisms. Infections of the digestive tract, irritable bowel, lactose intolerance, allergies, infections of the urogenital tract, cystic fibrosis, and various cancers can all be prevented and treated with the use of probiotics. They can reduce the side effects of various antibodies. In the field of oral health, dental caries, periodontal disease, and bad breath can be prevented and treated with the use of probiotics. The findings of several of these clinical studies indicate that probiotics may be beneficial in the treatment and prevention of various diseases and health issues. Validation of a significant number of these clinical investigations is necessary before the results can be applied to the clinical setting. Clinical studies play an important part in such investigations, and in the not-too-distant future, the outcomes of such trials will determine whether or not probiotics are effective in the treatment of disease. This article will attempt to provide a summary of the available literature on the benefits that these probiotics have with regard to health and disease. Probiotics are foods and/or supplements that contain non-pathogenic microbes such as bacteria and yeast that colonize the gut and can potentially yield a variety of health benefits. Research into the various ways in which probiotic bacteria could be used in the treatment of intestinal disorders is ongoing. Thanks to clinical studies and laboratory experiments, we now know more about how probiotics affect gut microbiome disorders. Studies can prove that probiotics can alleviate a variety of gastrointestinal ailments and improve overall health. This article concentrates on probiotics and commensal microbes, as well as their potential role in gut microbiome-related illnesses. In this section, we mark certain areas that need further work and studies so as to enhance our understanding of how probiotics help in the treatment and reduction of chances of gastrointestinal diseases.

Impact of different oral treatments on the composition of the supragingival plaque microbiome

Background

Dental plaque consists of a diverse microbial community embedded in a complex structure of exopolysaccharides. Dental biofilms form a natural barrier against pathogens but lead to oral diseases in a dysbiotic state.

Objective

Using a metaproteome approach combined with a standard plaque-regrowth study, this pilot study examined the impact of different concentrations of lactoperoxidase (LPO) on early plaque formation, and active biological processes.

Design

Sixteen orally healthy subjects received four local treatments as a randomized single-blind study based on a cross-over design. Two lozenges containing components of the LPO-system in different concentrations were compared to a placebo and Listerine®. The newly formed dental plaque was analyzed by mass spectrometry (nLC-MS/MS). 

Results

On average 1,916 metaproteins per sample were identified, which could be assigned to 116 genera and 1,316 protein functions. Listerine® reduced the number of metaproteins and their relative abundance, confirming the plaque inhibiting effect. The LPO-lozenges triggered mainly higher metaprotein abundances of early and secondary colonizers as well as bacteria associated with dental health but also periodontitis. Functional information indicated plaque biofilm growth.

Conclusion

In conclusion, the mechanisms on plaque biofilm formation of Listerine® and the LPO-system containing lozenges are different. In contrast to Listerine®, the lozenges led to a higher bacterial diversity.

Use of the Probiotic Bifidobacterium animalis subsp. lactis HN019 in Oral Diseases

The oral cavity is one of the environments on the human body with the highest concentrations of microorganisms that coexist harmoniously and maintain homeostasis related to oral health. Several local factors can shift the microbiome to a pathogenic state of dysbiosis. Existing treatments for infections caused by changes in the oral cavity aim to control biofilm dysbiosis and restore microbial balance. Studies have used probiotics as treatments for oral diseases, due to their ability to reduce the pathogenicity of the microbiota and immunoinflammatory changes. This review investigates the role of the probiotic Bifidobacterium animalis subsp. lactis (B. lactis) HN019 in oral health, and its mechanism of action in pre-clinical and clinical studies. This probiotic strain is a lactic acid bacterium that is safe for human consumption. It mediates bacterial co-aggregation with pathogens and modulates the immune response. Studies using B. lactis HN019 in periodontitis and peri-implant mucositis have shown it to be a potential adjuvant treatment with beneficial microbiological and immunological effects. Studies evaluating its oral effects and mechanism of action show that this probiotic strain has the potential to be used in several dental applications because of its benefit to the host.

Candidiasis and Other Bacterial Infections among Patients Diagnosed with Burning Mouth Syndrome

Background and Objectives: Burning mouth syndrome (BMS) is a state in which a patient experiences intraoral burning or a dysesthetic sensation without clinically evident causative lesions in the oropharyngeal area. The disorder is linked to a variety of conditions, including dry mouth, Candida, and bacterial infections. The aim of this study was to determine the incidence of oral Candida and/or bacterial infections among patients with BMS and whether they have an effect on pain/burning and salivary flow levels. Objectives: (1) Gather patient data regarding the presence of oral infections, dry mouth, and pain levels in the morning, afternoon, and evening periods; (2) data analysis and assessment to determine medians, means, frequencies, correlations, and statistically significant differences between patient groups. Materials and Methods: Overall, 173 patients (23 males and 150 females) with BMS and 13 controls (five males and eight females) took part in the study. We measured pain/burning levels, unstimulated and stimulated salivary flow, the percentage of patients infected with Candida species and/or bacterial species, and the said species growth in Petri dishes. Results: Candida albicans was the most commonly found infection among patients with BMS (n = 28, 16.2%). Overall, 21.4% patients with BMS were diagnosed with either C. albicans or another Candida species. Enterobacter had the richest growth among patients with BMS (7.5% out of the infected 10.4% BMS patients). No statistical significance could be noted between the existence of either Candida species or bacterial species infections and changes in pain/burning and salivary flow levels. Negative correlations were noted between age and unstimulated and stimulated salivary flow, and positive correlations were noted between age and Candida andspecific bacteria species’ growth levels. Conclusions: Although patients with present bacterial or Candida infections showed a marginal increase in pain/burning levels, no direct statistically significant associations could be made between the presence of Candida species or other bacteria and the symptoms among patients with BMS.

Comparison of the Oral Microbiota Structure among People from the Same Ethnic Group Living in Different Environments

The characteristics of the oral microbiota may depend on oral health, age, diet, and geography, but the influence of the geographic setting on the oral microbiota has received limited attention. The characteristics of oral microbiota have been reported to differ between urban and rural environments. In order to minimize the influence of genetic background, we recruited 54 volunteers from the same ethnic group, living in urban and rural areas of Gansu Province, China. We collected dental plaque samples and divided them into four groups according to the participant's area of residence and dental caries status. We sequenced the 16S rRNA of these samples using the Pacific Biosciences sequencing platform and analyzed the correlation between the geographic area and the characteristics of the oral microbiota. Analysis of the alpha and beta diversity revealed that there were significant differences in diversity and composition of dental plaque microflora among the four groups. Cluster analysis revealed that geographic area played an important role in determining the oral microbiota. Network analysis of oral microorganisms showed that geographic differences had major influence on the composition characteristics and internal structure of oral microorganisms. We found that some dominant strains which may play a key role in maintaining oral health, such as Streptococcus oralis, Capnocytophaga sputigena, Porphyromonas catoniae, Corynebacterium matruchotii, Haemophilus parainfluenzae, and Prevotella loescheii, were less affected by the geographic setting. These results provide a deeper understanding of factors influencing the composition of the oral microbiota and could contribute to early diagnosis and effective prevention of dental caries in different settings.

Aloe vera mouthwashes can be a natural alternative to chemically formulated ones - A randomized-controlled trial

Objectives

To evaluate the antiplaque and antibacterial efficacy of commercially available mouthwashes containing aloe vera (AV), hydrogen peroxide (HP), and cetylpyridinium chloride (CPC) in a 4-day plaque regrowth study.

Methods

Plaque score and salivary samples were assessed (Day-0 and Day-4) in 96 participants in a randomised, double-blind prospective parallel-arm 4-day plaque regrowth study. Participants were divided into five groups who refrained from engaging in regular oral hygiene measures during the study period and used commercially available mouthwashes containing AV, HP, and CPC as test products with distilled water (DW) and chlorhexidine (CHX) mouthwash as negative and positive controls, respectively. Salivary bacterial count was expressed as colony-forming units (CFU) (culture method).

Results

There was a significant difference both in plaque score (p < 0.001) and in CFU (p < 0.001) among the study mouthwashes at Day-4. The plaque score and CFU of AV were significantly higher and lower than those of CHX and DW, respectively. The plaque score of HP was significantly higher than that of AV (p = 0.016) and CPC (p < 0.001). No significant difference was observed between AV and CPC (p = 0.70). Moreover, the CFU of HP was significantly higher than that of CPC (p = 0.04). There was no statistically significant difference between the CFU of mouthwashes containing AV and HP (p = 0.912) or AV and CPC (p = 0.280). No significant difference was seen in the inhibition of plaque and salivary bacterial count between AV, HP, and CPC.

Conclusion

The antiplaque and antibacterial efficacy of commercially available AV mouthwash was similar to that of CPC and significantly better than that of HP mouthwash and can be a natural alternative to chemically formulated mouthwashes.

Cannabigerol Effect on Streptococcus mutans Biofilms—A Computational Approach to Confocal Image Analysis

Biofilms are complex bacterial structures in which bacterial cells thrive as a community. Many bacterial species, including pathogens, form biofilms of high complexity and adaptability to a wide range of environmental conditions. One example of these is Streptococcus mutans, a gram-positive bacterium that has been associated with caries. Cannabigerol, a non-psychoactive cannabinoid, has been shown to affect S. mutans biofilms. In order to better characterize the effect of cannabigerol on biofilms of S. mutans, this paper provides a series of computational assays for biofilm analysis, applied on confocal images of S. mutans biofilms treated with cannabigerol. Confocal images are ubiquitous in biofilm analysis—they are often used to visualize the complex structure and molecular composition of biofilm macrocolonies. In this article, we demonstrate how confocal imaging data can be used to reveal more comprehensive insights into biofilm structure and measure specific anti-biofilm effects. This is accomplished by a series of computational assays, each focusing on a different aspect of biofilm structure.

Gut-lung cross talk in COVID-19 pathology and fatality rate

Coronavirus disease 2019 (COVID-19) is the leading pandemic facing the world in 2019/2020; it is caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which necessitates clear understanding of the infectious agent. The virus manifests aggressive behavior with severe clinical presentation and high mortality rate, especially among the elderly and patients living with chronic diseases. In the recent years, the role of gut microbiota, in health and disease, has been progressively studied and highlighted. It is through gut microbiota-organ bidirectional pathways, such as gut-brain axis, gut-liver axis, and gut-lung axis, that the role of gut microbiota in prompting lung disease, among other diseases, has been proposed and accepted. It is also known that respiratory viral infections, such as COVID-19, induce alterations in the gut microbiota, which can influence immunity. Based on the fact that gut microbiota diversity is decreased in old age and in patients with certain chronic diseases, which constitute two of the primary fatality groups in COVID-19 infections, it can be assumed that the gut microbiota may play a role in COVID-19 pathology and fatality rate. Improving gut microbiota diversity through personalized nutrition and supplementation with prebiotics/probiotics will mend the immunity of the body and hence could be one of the prophylactic strategies by which the impact of COVID-19 can be minimized in the elderly and immunocompromised patients. In this chapter, the role of dysbiosis in COVID-19 will be clarified and the possibility of using co-supplementation of personalized prebiotics/probiotics with current therapies will be discussed.

The Use of a Diode Laser for Removal of Microorganisms from the Surfaces of Zirconia and Porcelain Applied to Superstructure Dental Implants

The aim of this paper was to study the effectiveness of a diode laser (LD) for removal of microorganisms isolated from porcelain and zirconia crown surfaces used in implantoprosthetics in order to minimize infections around dental implants. In order to optimize biocidal efficacy of the process (at the same time, avoiding increasing the surface roughness during decontamination) the effects of diode laser doses were investigated. The irradiation was performed with a diode laser at the wavelength of λ = 810 nm in three variants with a different number of repetitions (1 × 15 s, 2 × 15 s, 3 × 15 s). The quantitative microbial contamination of the surface of teeth, porcelain and zirconia crowns assessment was made using the culture-dependent method. The identification of microorganisms took place using the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and next-generation sequencing (NGS) methods. The studies of the surface morphology and roughness were carried out by means of the optical profilometry, scanning electron microscopy (SEM) and optical microscopy with the C1 confocal attachment. The most important conclusion from the research is the fact that the laser operation, regardless of the exposure time, effectively eliminates the microorganisms from the surfaces used for dental implant rebuilding and does not have a destructive effect on the tested material.

Cationic Antimicrobial Peptides Are Leading the Way to Combat Oropathogenic Infections

Oral dental infections are one of the most common diseases affecting humans, with caries and periodontal disease having the highest incidence. Caries and periodontal disease arise from infections caused by oral bacterial pathogens. Current misuse and overuse of antibiotic treatments have led to the development of antimicrobial resistance. However, recent studies have shown that cationic antimicrobial peptides are a promising family of antibacterial agents that are active against oral pathogenic bacteria and also possess less propensity for development of antimicrobial resistance. This timely Review has a focus on two primary subjects: (i) the oral bacterial pathogens associated with dental infections and (ii) the current development of antimicrobial peptides targeting oral pathogens.

Progress in Oral Microbiome Related to Oral and Systemic Diseases: An Update

The human oral microbiome refers to an ecological community of symbiotic and pathogenic microorganisms found in the oral cavity. The oral cavity is an environment that provides various biological niches, such as the teeth, tongue, and oral mucosa. The oral cavity is the gateway between the external environment and the human body, maintaining oral homeostasis, protecting the mouth, and preventing disease. On the flip side, the oral microbiome also plays an important role in the triggering, development, and progression of oral and systemic diseases. In recent years, disease diagnosis through the analysis of the human oral microbiome has been realized with the recent development of innovative detection technology and is overwhelmingly promising compared to the previous era. It has been found that patients with oral and systemic diseases have variations in their oral microbiome compared to normal subjects. This narrative review provides insight into the pathophysiological role that the oral microbiome plays in influencing oral and systemic diseases and furthers the knowledge related to the oral microbiome produced over the past 30 years. A wide range of updates were provided with the latest knowledge of the oral microbiome to help researchers and clinicians in both academic and clinical aspects. The microbial community information can be utilized in non-invasive diagnosis and can help to develop a new paradigm in precision medicine, which will benefit human health in the era of post-metagenomics.

Piper betle (L): Recent Review of Antibacterial and Antifungal Properties, Safety Profiles, and Commercial Applications

Piper betle (L) is a popular medicinal plant in Asia. Plant leaves have been used as a traditional medicine to treat various health conditions. It is highly abundant and inexpensive, therefore promoting further research and industrialization development, including in the food and pharmaceutical industries. Articles published from 2010 to 2020 were reviewed in detail to show recent updates on the antibacterial and antifungal properties of betel leaves. This current review showed that betel leaves extract, essential oil, preparations, and isolates could inhibit microbial growth and kill various Gram-negative and Gram-positive bacteria as well as fungal species, including those that are multidrug-resistant and cause serious infectious diseases. P. betle leaves displayed high efficiency on Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa, Gram-positive bacteria such as Staphylococcus aureus, and Candida albicans. The ratio of MBC/MIC indicated bactericidal and bacteriostatic effects of P. betle leaves, while MFC/MIC values showed fungicidal and fungistatic effects. This review also provides a list of phytochemical compounds in betel leaves extracts and essential oils, safety profiles, and value-added products of betel leaves. Some studies also showed that the combination of betel leaves extract and essential oil with antibiotics (streptomycin, chloramphenicol and gentamicin) could provide potentiating antibacterial properties. Moreover, this review delivers a scientific resume for researchers in respected areas and manufacturers who want to develop betel leaves-based products.

Identification of Fusobacterium nucleatum in primary and secondary endodontic infections and its association with clinical features by using two different methods

OBJECTIVE

Fusobacterium nucleatum is an important oral pathogen involved in endodontic infections. This study aimed to assess the frequency of Fusobacterium nucleatum in primary and secondary endodontic infections and its associations with the clinical features in a Brazilian population by using both culture and nested PCR methods.

METHODS

A total of 100 microbial samples from patients with primary (n=50) and secondary endodontic infections (n=50) were analyzed by using culture and nested PCR methods. Strict anaerobic techniques were used for culture and identification of F. nucleatum. The DNA extracted from the samples was analyzed for the presence of target species by using species-specific primers.

RESULTS

Culture and nested PCR methods detected F. nucleatum, respectively, in 11/100 and 82/100 root canals. F. nucleatum was isolated by culture from 10/50 (20%) root canals with primary infections and from 1/50 (2%) root canal with secondary/persistent infections. Nested PCR detected F. nucleatum in 42/50 (84%) root canals with primary infections and in 40/50 (80%) root canals with secondary/persistent endodontic infections. F. nucleatum was associated with spontaneous pain, tenderness to percussion, pain on palpation, swelling, tooth mobility, wet root canals, hemorrhagic exudate, tooth decay, inadequate restoration, and poor endodontic filling.

CONCLUSION

F. nucleatum was found in more cases of primary endodontic infections than in cases of secondary/persistent ones. A higher prevalence of F. nucleatum was detected by using the nested PCR method than by using culture. The presence of F. nucleatum in the root canals was associated with several clinical features.

CLINICAL RELEVANCE

The high prevalence of F. nucleatum in the root canals detected by molecular methods, and its association with several clinical features reveals the importance of these species in the development of apical pathologies and reinforces the need of an endodontic treatment directed to bacterial elimination.

Salivary Microbiome in Pediatric and Adult Celiac Disease

The human salivary microbiota includes hundreds of bacterial species. Alterations in gut microbiota have been explored in Celiac Disease (CD), but fewer studies investigated the characteristics of salivary microbiome in these patients, despite the potential implications in its pathogenesis. Indeed, some recent studies suggested that the partial digestion of gluten proteins by some bacteria may affect the array of gluten peptides reaching the gut and the way by which those are presented to the intestinal immune system. The available clinical studies investigating the salivary microbiota in children and adults, are insufficient to make any reliable conclusion, even though some bacterial species/phyla differences have been reported between celiac patients and controls. However, the salivary microbiome could correlate better with the duodenal microbiota, than the fecal one. Therefore, further clinical studies on salivary microbiome by different and independent research groups and including different populations, are advisable in order to explore the usefulness of the salivary microbiome analysis and understand some aspects of CD pathogenesis with potential clinical and practical implications.

Implication of Surface Properties, Bacterial Motility, and Hydrodynamic Conditions on Bacterial Surface Sensing and Their Initial Adhesion

Biofilms are structured microbial communities attached to surfaces, which play a significant role in the persistence of biofoulings in both medical and industrial settings. Bacteria in biofilms are mostly embedded in a complex matrix comprised of extracellular polymeric substances that provide mechanical stability and protection against environmental adversities. Once the biofilm is matured, it becomes extremely difficult to kill bacteria or mechanically remove biofilms from solid surfaces. Therefore, interrupting the bacterial surface sensing mechanism and subsequent initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Noting that the process of bacterial adhesion is influenced by many factors, including material surface properties, this review summarizes recent works dedicated to understanding the influences of surface charge, surface wettability, roughness, topography, stiffness, and combination of properties on bacterial adhesion. This review also highlights other factors that are often neglected in bacterial adhesion studies such as bacterial motility and the effect of hydrodynamic flow. Lastly, the present review features recent innovations in nanotechnology-based antifouling systems to engineer new concepts of antibiofilm surfaces.

Antimicrobial Effects of Essential Oils on Oral Microbiota Biofilms: The Toothbrush In Vitro Model

The present investigation intended to evaluate the bacteriostatic and bactericidal abilities of clove, oregano and thyme essential oils against oral bacteria in planktonic and biofilm states. Furthermore, aiming to mimic everyday conditions, a toothbrush in vitro model was developed. Determination of the minimum inhibitory concentration, minimum bactericidal concentration, minimum biofilm inhibitory concentration and minimum biofilm eradication concentration were achieved using the microdilution procedure. To simulate the toothbrush environment, nylon fibers were inoculated with oral bacteria, which, after incubation to allow biofilm development, were submitted to contact with the essential oils under study. Thyme and oregano essential oils revealed promising antimicrobial effects, both in growth inhibition and the destruction of cells in planktonic and biofilm states, while clove essential oil showed a weaker potential. Regarding the toothbrush in vitro model, observation of the nylon fibers under a magnifying glass proved the essential oil anti-biofilm properties. Considering the effects observed using the in vitro toothbrush model, a realistic approximation to oral biofilm establishment in an everyday use object, a putative application of essential oils as toothbrush sanitizers to help prevent the establishment of bacterial biofilm can be verified.

Probiotics-A complete oral healthcare package

Probiotics are living bacterial cells that have significant therapeutic potential for treating human infectious diseases. There is a huge market for probiotics in the pharmaceutical sector. They have been frequently used to treat the gastrointestinal diseases and improve gut immunity. In this review, the strains currently in use for manufacturing oral probiotic formulations are discussed. The review further recommends the use of probiotics for the control of various oral health disorders, like dental caries, periodontitis, gingivitis, halitosis, burning mouth syndrome, and oral cancer. Finally, this review also explores the use of various commercial probiotic products in maintaining oral health, their market values, and government acts and regulations that are relevant to the production and marketing of probiotics. Probiotics have tremendous therapeutic potential and more in-depth research must be done on these beneficial bacteria to make them one of the leading drugs in treating oral disorders.

Cytotoxicity of fluconazole on canine dental pulp-derived stem cells

Objective

In order to use fluconazole as an antifungal in cell cultures, we evaluated its possible cytotoxic effects and its influence on the proliferation and viability of canine dental pulp-derived stem cells (cDPSCs).

Methods

Samples from permanent canine teeth were placed in a sterile tube with IMDM, penicillin-streptomycin, sodium heparin, and different concentrations of fluconazole. Dental pulp was digested (collagenase type II) and expanded in vitro. After 12 days of culture, enzymatic dissociation of the cDPSCs was performed to quantify, differentiate, and characterize the cells. Cytotoxicity was evaluated based on cell viability in response to fluconazole treatment using the 7-AAD dye.

Results

Characterization of the cDPSCs revealed that fluconazole had no influence on the immunophenotypic characteristics and differentiation of these cells. Cell proliferation assay revealed that fluconazole did not significantly interfere with the replication capacity of the cDPSCs. Cytotoxicity analysis revealed a loss of cell viability as the fluconazole concentration increased. Although there was an increase in cell mortality, the number of dead cells remained low. Though the higher concentration of fluconazole (240 μg/mL) resulted in a higher number of non-viable cells, it remained safe for use.

Conclusion

To prevent fungal contamination that causes a loss of samples during expansion of cDPSCs and to maintain minimal cell toxicity, we suggest adding 120 μg/mL of fluconazole to the teeth collection medium and cDPSCs culture.

The role of salivary contents and modern technologies in the remineralization of dental enamel: a narrative review

Human enamel once formed cannot be biologically repaired or replaced. Saliva has a significant role in remineralization of dental enamel. It not only has a buffering capacity to neutralize the oral cavity's low pH generated after acidic encounters, but also acts as a carrier of essential ions, such as fluoride, calcium and phosphate, which have a positive role in enamel's remineralization. This review discusses how salivary contents, like proteins and enzymes, have a natural role in enamel's mineralization. In addition, the presence of ions, such as fluoride, calcium and phosphate, in saliva further enhances its capability to remineralize the demineralized enamel surface. The review further examines modern innovative technologies, based on biomimetic regeneration systems, including dentin phosphoproteins, aspartate-serine-serine, recombinant porcine amelogenin, leucine-rich amelogenin peptide and nano-hydroxyapatite, that promote enamel remineralization. Fluoride boosters like calcium phosphates, polyphosphates, and certain natural products can also play an important role in enamel remineralization.

The role of salivary contents and modern technologies in the remineralization of dental enamel: a narrative review

Human enamel once formed cannot be biologically repaired or replaced. Saliva has a significant role in remineralization of dental enamel. It not only has a buffering capacity to neutralize the oral cavity’s low pH generated after acidic encounters, but also acts as a carrier of essential ions, such as fluoride, calcium and phosphate, which have a positive role in enamel’s remineralization. This review discusses how salivary contents, like proteins and enzymes, have a natural role in enamel’s mineralization. In addition, the presence of ions, such as fluoride, calcium and phosphate, in saliva further enhances its capability to remineralize the demineralized enamel surface. The review further examines modern innovative technologies, based on biomimetic regeneration systems, including dentin phosphoproteins, aspartate-serine-serine, recombinant porcine amelogenin, leucine-rich amelogenin peptide and nano-hydroxyapatite, that promote enamel remineralization. Fluoride boosters like calcium phosphates, polyphosphates, and certain natural products can also play an important role in enamel remineralization.

The role of salivary contents and modern technologies in the remineralization of dental enamel: a narrative review

Human enamel once formed cannot be biologically repaired or replaced. Saliva has a significant role in remineralization of dental enamel. It not only has a buffering capacity to neutralize the oral cavity's low pH generated after acidic encounters, but also acts as a carrier of essential ions, such as fluoride, calcium and phosphate, which have a positive role in enamel's remineralization. This review discusses how salivary contents, like proteins and enzymes, have a natural role in enamel's mineralization. In addition, the presence of ions, such as fluoride, calcium and phosphate, in saliva further enhances its capability to remineralize the demineralized enamel surface. The review further examines modern innovative technologies, based on biomimetic regeneration systems, including dentin phosphoproteins, aspartate-serine-serine, recombinant porcine amelogenin, leucine-rich amelogenin peptide and nano-hydroxyapatite, that promote enamel remineralization. Fluoride boosters like calcium phosphates, polyphosphates, and certain natural products can also play an important role in enamel remineralization.

Comparative inhibitory effects of 4-allylpyrocatechol isolated from Piper betle on Streptococcus intermedius, Streptococcus mutans, and Candida albicans

Streptococcus intermedius, Streptococcus mutans, and Candida albicans are harmful oral pathogens and prone to resist chemical antimicrobial agents. Active ingredients from plants are of increasing interest as an alternative. This study aims to compare antimicrobial effects of 4-allylpyrocatechol (APC) extracted from Piper betle on these oral pathogens. Minimum concentration of APC against the tested pathogens was determined using a broth microdilution assay. Killing kinetic study of APC was carried out within 24 h. Morphology of the pathogenic cells was assessed using scanning electron microscopy (SEM). Anti-biofilm was investigated using crystal violet assay and confocal laser scanning microscopy (CLSM). The results showed that the mechanism of inhibition of APC was bactericidal and fungicidal effects. APC at minimum concentration of 400 μg/mL could completely kill Streptococcus and Candida spp., however, the killing rate on S. intermedius and C. albicans was significantly faster than on S. mutans. APC inhibited biofilm formation of C. albicans more efficiently than that of the bacterial cells. Cell morphology from SEM indicated that APC caused bacterial cell membrane destruction and inhibited fungal budding or tubing formation. CLSM images confirmed the killing potential of APC and suggested that bacterial dead cells could be easier washed out than the fungal dead cells. It is concluded that APC potentially inhibits growth and biofilms of oral Streptococcus and Candida spp. in different mechanism of action and killing rate. APC can be considered as a promising agent for preventing and treating dental disorders caused by S. intermedius, S. mutans, and C. albicans.

Metaproteomics analysis of microbial diversity of human saliva and tongue dorsum in young healthy individuals

Background: The human oral microbiome influences initiation or progression of diseases like caries or periodontitis. Metaproteomics approaches enable the simultaneous investigation of microbial and host proteins and their interactions to improve understanding of oral diseases.

Objective: In this study, we provide a detailed metaproteomics perspective of the composition of salivary and tongue microbial communities of young healthy subjects.

Design: Stimulated saliva and tongue samples were collected from 24 healthy volunteers, subjected to shotgun nLC-MS/MS and analyzed by the Trans-Proteomic Pipeline and the Prophane tool.

Results: 3,969 bacterial and 1,857 human proteins could be identified from saliva and tongue, respectively. In total, 1,971 bacterial metaproteins and 1,154 human proteins were shared in both sample types. Twice the amount of bacterial metaproteins were uniquely identified for the tongue dorsum compared to saliva. Overall, 107 bacterial genera of seven phyla formed the microbiome. Comparative analysis identified significant functional differences between the microbial biofilm on the tongue and the microbiome of saliva.

Conclusion: Even if the microbial communities of saliva and tongue dorsum showed a strong similarity based on identified protein functions and deduced bacterial composition, certain specific characteristics were observed. Both microbiomes exhibit a great diversity with seven genera being most abundant.

Failure Probability, Stress Distribution and Fracture Analysis of Experimental Screw for Micro Conical Abutment

The aim of this study was to evaluate the failure probability of two types of abutment screws after compressive load and to analyze the stress distribution with finite element method. Sixty (60) single-tooth implant restorations were assembled on titanium implants (e-fix, A.S. Technology - Titanium Fix). The groups were divided into Conventional screw (Screw neck 1.5 ø mm) and Experimental screw (Screw neck constricted with 1.2 ø mm). Specimens were subjected to single load to failure with compressive test according ISO 14801. The fractured specimens were subjected to stereomicroscopy for measurement of remaining screws inside the implant and characterization of fracture origin. Representative specimens were analyzed by scanning electronic microscopy. For finite element method (FEM), an identical 3D model of the two in vitro test groups were used with similar conditions (30º, 100 N load). The stress in the abutment screw was analyzed by von-Mises criteria. The results of strength means were 4132.5 ± 76 MPa and 4528.2 ± 127.2 for conventional and experimental groups, respectively. During microscopy, the mean (mm) of the remaining screw piece inside the implants were 0.97 ± 0.23 and 1.32 ± 0.12 for conventional and experimental groups, respectively. In FEM, the conventional group showed stress concentered in an unfavorable region (peak of 39.23 MPa), while the experimental group showed more stress areas but less concentration than the conventional group (36.6 MPa). In using the tested experimental geometry, the abutment screw can have its strength improved, and the origin of failure can be more favorable to clinical resolution.

Salivary Microbial Dysbiosis is Associated with Systemic Inflammatory Markers and Predicted Oral Metabolites in Non-Small Cell Lung Cancer Patients

An increasing number of studies have suggested the dysbiosis of salivary microbiome has been linked to the advancement of multiple diseases and proved to be helpful for the diagnosis of them. Although epidemiological studies of salivary microbiota in carcinogenesis are mounting, no systemic study exists regarding the oral microbiota of non-small cell lung cancer (NSCLC) patients. In this study, we presented the characteristics of the salivary microbiota in patients from NSCLC and healthy controls by sequencing of the 16S rRNA microbial genes. Our result revealed distinct salivary microbiota composition in patients from NSCLC compared to the healthy controls. As principal co-ordinates analysis (PCoA) showed, saliva samples clearly differed between the two groups, considering the weighted (p = 0.001, R² = 0.17), and unweighted (p = 0.001, R² = 0.25) UniFrac distance. Phylum Firmicutes (31.69% vs 24.25%, p < 0.05) and its two genera Veillonella (15.51%% vs 9.35%, p < 0.05) and Streptococcus (9.96% vs 6.83%, p < 0.05) were strongly increased in NSCLC group compared to the controls. Additionally, the relative abundances of Fusobacterium (3.06% vs 4.92%, p = 0.08), Prevotella (1.45% vs 3.52%, p < 0.001), Bacteroides (0.56% vs 2.24%, p < 0.001), and Faecalibacterium (0.21% vs 1.00%, p < 0.001) in NSCLC group were generally decreased. Furthermore, we investigated the correlations between systemic inflammation markers and salivary microbiota. Neutrophil-lymphocyte ratio (NLR) positively correlated with the Veillonella (r =0.350, p = 0.007) and lymphocyte-monocyte ratio (LMR) negatively correlated with Streptococcus (r =-0.340, p = 0.008). Additionally, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways inferred by phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) showed that pathways related to xenobiotics biodegradation and metabolism (p < 0.05) and amino acid metabolism (p < 0.05) were enriched in the NSCLC group. Folate biosynthesis (p < 0.05) significantly decreased in NSCLC group. The specific correlations of clinical systemic inflammation markers and predicted KEGG pathways also could pronounce a broad understanding of salivary microbiota in patients with NSCLC. Moreover, our study extended the new sight into salivary microbiota-targeted interventions to clinically improve the therapeutic strategies for salivary dysbiosis in NSCLC patients. Further investigations of the potential mechanism of salivary microbiota in the progression of NSCLC are still in demand.

Microbial Degradation of Forensic Samples of Biological Origin: Potential Threat to Human DNA Typing

Forensic biology is a sub-discipline of biological science with an amalgam of other branches of science used in the criminal justice system. Any nucleated cell/tissue harbouring DNA, either live or dead, can be used as forensic exhibits, a source of investigation through DNA typing. These biological materials of human origin are rich source of proteins, carbohydrates, lipids, trace elements as well as water and, thus, provide a virtuous milieu for the growth of microbes. The obstinate microbial growth augments the degradation process and is amplified with the passage of time and improper storage of the biological materials. Degradation of these biological materials carriages a huge challenge in the downstream processes of forensic DNA typing technique, such as short tandem repeats (STR) DNA typing. Microbial degradation yields improper or no PCR amplification, heterozygous peak imbalance, DNA contamination from non-human sources, degradation of DNA by microbial by-products, etc. Consequently, the most precise STR DNA typing technique is nullified and definite opinion can be hardly given with degraded forensic exhibits. Thus, suitable precautionary measures should be taken for proper storage and processing of the biological exhibits to minimize their decaying process by micro-organisms.

Quantification of carious pathogens in the interdental microbiota of young caries-free adults

Background

The majority of caries lesions in adults occur on the proximal tooth surfaces of the posterior teeth. A comprehensive study of the composition of the oral microbiota is fundamental for a better understanding of the etiology of interdental caries.

Methods

Twenty-five caries-free subjects (20–35 years old) were enrolled in the study. The interdental biofilm of four interdental sites were collected. The real-time polymerase chain reaction (PCR) methodology were used to quantify (i) the following bacteria: Streptococcus spp., Streptococcus mutans, Lactobacillus spp., Enterococcus spp., and Enterococcus faecalis; (ii) the fungus Candida albicans; and (iii) total bacteria.

Results

Streptococcus spp. was the most abundant species, followed by Lactobacillus spp. and Enterococcus spp. Streptococcus spp. and Lactobacillus spp. were detected at all tested sites and Enterococcus spp. at 99% of sites. S. mutans was detected at only 28% of the tested sites and C. albicans was detected at 11% of sites. E. faecalis was never detected. In 54.5% of the biofilm inhabited by C. albicans, S. mutans was present. Moreover, 28% of the ID sites co-expressed S. mutans and Lactobacillus spp. The studied pathogens were organized into two correlated groups of species. Strikingly, the fungus C. albicans and the bacteria Enterococcus spp. cluster together, whereas Streptococcus spp., S. mutans and Lactobacillus spp. form one distinct cluster.

Conclusion

The interdental biofilm of young caries-free adults is comprised of pathogens that are able to induce interproximal caries. That several of these pathogens are implicated in heart disease or other systemic diseases is an argument for the disruption of interdental biofilms using daily oral hygiene.

Probiotics and oral health: A systematic review

Background

Probiotics are microorganisms, mainly bacteria, which benefit the host’s health. Many studies support the role of probiotics as a contributor to gastrointestinal health, and nowadays many authors are trying to prove its influence in oral health maintenance.

Objectives

To review the published literature with the purpose of knowing the importance of using probiotics as a preventive and therapeutic method for oral infectious diseases management.

Material and Methods

An electronic search in PubMed database with the keywords “oral health AND probiotics AND dentistry” was conducted. The inclusion criteria were: randomized clinical trials (RCTs) that assess the action of any probiotic strain in the treatment and / or prevention of an infectious oral disease, RCTs that assess the action of any probiotic strain on counting colony forming units (CFU) of oral pathogens, systematic reviews and meta-analysis. The Jadad scale was used to assess the high quality of RCTs.

Results

Fifteen articles were considered for this review. Of which, 12 were RCTs of good / high quality (Jadad scale), two meta-analysis and one systematic review.

Conclusions

The literature reviewed suggests probiotics usage could be beneficial for the maintenance of oral health, due to its ability to decrease the colony forming units (CFU) counts of the oral pathogens. However, randomized clinical trials with long-term follow-up periods are needed to confirm their efficacy in reducing the prevalence/incidence of oral infectious diseases. Furthermore, the recognition of specific strains with probiotic activity for each infectious oral disease is required, in order to determine exact dose, treatment time and ideal vehicles.

Key words:Probiotics, periodontal diseases, dental caries, oral health.

Microbial profiling of dental plaque from mechanically ventilated patients

Micro-organisms isolated from the oral cavity may translocate to the lower airways during mechanical ventilation (MV) leading to ventilator-associated pneumonia (VAP). Changes within the dental plaque microbiome during MV have been documented previously, primarily using culture-based techniques. The aim of this study was to use community profiling by high throughput sequencing to comprehensively analyse suggested microbial changes within dental plaque during MV. Bacterial 16S rDNA gene sequences were obtained from 38 samples of dental plaque sampled from 13 mechanically ventilated patients and sequenced using the Illumina platform. Sequences were processed using Mothur, applying a 97 % gene similarity cut-off for bacterial species level identifications. A significant ‘microbial shift’ occurred in the microbial community of dental plaque during MV for nine out of 13 patients. Following extubation, or removal of the endotracheal tube that facilitates ventilation, sampling revealed a decrease in the relative abundance of potential respiratory pathogens and a compositional change towards a more predominantly (in terms of abundance) oral microbiota including Prevotella spp., and streptococci. The results highlight the need to better understand microbial shifts in the oral microbiome in the development of strategies to reduce VAP, and may have implications for the development of other forms of pneumonia such as community-acquired infection.