Tongue microbiome of smokeless tobacco users.

BACKGROUND: The possibility that smokeless tobacco may contribute to oral carcinogenesis by influencing the oral microbiome has not been explored. This preliminary cross-sectional study sought to assess the effect of using shammah, a form of smokeless tobacco prevalent in Arabia, on the tongue microbiome. Tongue scarping samples were obtained from 29 shammah users (SU; 27.34 ± 6.9 years) and 23 shammah non-users (SNU; 27.7 ± 7.19 years) and analyzed with 16S rRNA gene sequencing (V1-V3). Species-level taxonomy assignment of the high-quality, merged reads was obtained using a previously described BLASTn-based algorithm. Downstream analyses were performed with QIIME, LEfSe, and R. RESULTS: A total of 178 species, belonging to 62 genera and 8 phyla were identified. Genera Streptococcus, Leptotrichia, Actinomyces, Veillonella, Haemophilus, Prevotella and Neisseria accounted for more than 60% of the average microbiome. There were no differences between the two groups in species richness and alpha-diversity, but PCoA showed significant separation (P = 0.015, ANOSIM). LEfSe analysis identified 22 species to be differentially abundant between the SU and SNU. However, only 7 species maintained a false discovery rate of ≤0.2 and could cluster the two groups separately: Rothia mucilaginosa, Streptococcus sp. oral taxon 66, Actinomyces meyeri, Streptococcus vestibularis Streptococcus sanguinis and a potentially novel Veillonella species in association with SU, and Oribacterium asaccharolyticum with SNU. CONCLUSION: These preliminary results indicate that shammah use induces tongue microbiome changes including enrichment of several species with high acetaldehyde production potential, which warrants further investigation.

N-acetyl cysteine versus chlorhexidine mouthwashes in prevention and treatment of experimental gingivitis: a randomized, triple-blind, placebo-controlled clinical trial.

OBJECTIVES: To compare the efficacy of N-acetyl cysteine (NAC) mouthwash with chlorhexidine (CHX) in prevention and treatment of experimental gingivitis MATERIALS AND METHODS: Sixty subjects were assigned randomly and blindly into one of three equal groups: NAC, CHX, or placebo group. The study was conducted in two stages: preventive and treatment substudies. Professional prophylaxis was performed ahead of starting the preventive substudy. Then, the subjects were instructed to stop oral hygiene practices and begin rinsing twice/day with 15 ml of the assigned mouthwash (1.25% NAC, 0.2% CHX, or inert base). Plaque index (PI), gingival index (GI), and papillary bleeding index (PBI) were measured at baseline, 7, 14, and 21 days. The treatment substudy started on day 21 in which the subjects in the placebo group (now with established experimental gingivitis) were assigned to NAC (n = 10) or CHX (n = 10); the abovementioned indices were measured at 28 and 35 days. Efficacy of these interventions was compared. RESULTS: All groups accumulated plaque and developed some degree of gingivitis: full-blown in the placebo group and remarkably mild in the CHX group. NAC had slight preventive properties at days 14 and 21. In the treatment substudy, CHX was associated with remarkable reduction in plaque and gingivitis while NAC resulted in insignificant reductions. CONCLUSIONS: 1.25% NAC is marginally effective in prevention and treatment of experimental gingivitis. CLINICAL RELEVANCE: When compared with the placebo, NAC showed promising preventive and treatment effects of gingivitis that deserve further development and studies. TRIAL REGISTRATION: ISRCTN31352091.

Exome sequencing of oral squamous cell carcinoma in users of Arabian snuff reveals novel candidates for driver genes.

The study sought to identify genetic aberrations driving oral squamous cell carcinoma (OSCC) development among users of shammah, an Arabian preparation of smokeless tobacco. Twenty archival OSCC samples, 15 of which with a history of shammah exposure, were whole-exome sequenced at an average depth of 127×. Somatic mutations were identified using a novel, matched controls-independent filtration algorithm. CODEX and Exomedepth coupled with a novel, Database of Genomic Variant-based filter were employed to call somatic gene-copy number variations. Significantly mutated genes were identified with Oncodrive FM and the Youn and Simon's method. Candidate driver genes were nominated based on Gene Set Enrichment Analysis. The observed mutational spectrum was similar to that reported by the TCGA project. In addition to confirming known genes of OSCC (TP53, CDKNA2, CASP8, PIK3CA, HRAS, FAT1, TP63, CCND1 and FADD) the analysis identified several candidate novel driver events including mutations of NOTCH3, CSMD3, CRB1, CLTCL1, OSMR and TRPM2, amplification of the proto-oncogenes FOSL1, RELA, TRAF6, MDM2, FRS2 and BAG1, and deletion of the recently described tumor suppressor SMARCC1. Analysis also revealed significantly altered pathways not previously implicated in OSCC including Oncostatin-M signalling pathway, AP-1 and C-MYB transcription networks and endocytosis. There was a trend for higher number of mutations, amplifications and driver events in samples with history of shammah exposure particularly those that tested EBV positive, suggesting an interaction between tobacco exposure and EBV. The work provides further evidence for the genetic heterogeneity of oral cancer and suggests shammah-associated OSCC is characterized by extensive amplification of oncogenes.

Antibiotic Prescription Knowledge of Dentists in Kingdom of Saudi Arabia: An Online, Country-wide Survey.

AIM: Dentists are probably contributing to the development of bacterial resistance to certain antibiotics. Campaigns to promote prudent use of antibiotics in dentistry are, thus, needed but require proper identification of dentists' knowledge gaps. The objective here was to comprehensively evaluate antibiotic prescription knowledge of dentists in Saudi Arabia. MATERIAL AND METHODS: A link to an online, previously validated questionnaire was emailed to 5199 dentists registered with the Saudi Dental Society. The questionnaire comprised 42 scorable items measuring antibiotics prescription knowledge in five different domains in addition to nonscorable questions regarding first-choice antibiotics and previous attendance of a course/workshop about antibiotic prescription. Each correct answer was given one mark. Mean scores were calculated as percentages and categorized as good (> 80%), intermediate (60-80%), or poor (< 60%). RESULTS: The response rate was 9.4%; however, only 373 (7.2%) fully completed the questionnaire. Around half of the participants (52%) reported prescribing amoxicillin/clavulanate as the first-choice antibiotic; 62% reported attending a course/workshop in the last 5 years. The average knowledge score was 69%, being highest for nonclinical indications (79%) and lowest for prophylactic use (56%). The worst per-item scores were noted for rheumatic heart disease (19%), trismus (28%), surgical extraction (30%), apicectomy (31%), and periodontal abscess (33%). Female dentists, dentists in governmental sector, and those with higher qualifications had significantly better knowledge. CONCLUSION: The level of knowledge was hardly intermediate and several deficits were identified, indicating an urgent need for educational campaigns and provision of guidelines promoting rational use of antibiotics by dentists. CLINICAL SIGNIFICANCE: Irrational use of antibiotics by dentists can contribute to the problem of antibacterial resistance.

Salivary Candida species carriage patterns and their relation to caries experience among yemeni children.

PURPOSE: This study was carried out to assess the carriage rates, counts and species distribution of Candida in saliva of 6- to 12-year-old Yemeni children and relate that to their caries experience. MATERIALS AND METHODS: One hundred eighty children were recruited. Oral hygiene and caries were assessed using the simplified oral hygiene index and dft/DMFT index, respectively. Detection and quantification of 4 Candida species in unstimulated saliva were performed using CHROMagar Candida medium. Data were analysed using regression analysis. RESULTS: Candida was detected in 60% of the children with a mean count of 923 ± 1875 CFU/ml. C. albicans accounted for 60% of the isolates and was the only species to be detected with more than 1000 CFU/ml. Non-albicans candida and unidentified species represented 16.3% and 23.1% of the isolates, respectively. One novel finding was that a significant proportion (38%) of the carriers harboured two or more species, which for the first time allowed the identification of four age-dependent carriage patterns (clusters). Another somewhat new observation was that carriage at ≥ 1000 CFU/ml in particular significantly correlated with caries in primary and permanent dentitions (r = 0.23 and 0.18, respectively) as well as a caries-active status (OR = 6.9). Interestingly, the C. glabrata cluster had significantly lower primary caries scores than other clusters. CONCLUSIONS: The findings substantiate claims of geographical variations in candida carriage and the relation between candida carriage and caries. The validity of carrier clusters and the use of 1000 CFU/ml as a risk marker should be further investigated.

Nonsyndromic cleft lip with or without cleft palate in arab populations: genetic analysis of 15 risk loci in a novel case-control sample recruited in Yemen.

BACKGROUND: Nonsyndromic orofacial clefting (nsOFC) is among the most common of all congenital disorders and has a genetically complex etiology. Based on embryological and epidemiological data, the phenotype can be differentiated into nonsyndromic cleft lip with or without cleft palate (nsCL/P) and nonsyndromic cleft palate only, with nsCL/P being the most frequent form. Recent genetic research, predominantly performed in populations from Europe and Asia, has identified numerous genetic susceptibility loci for nsCL/P. As only few data are available concerning genetic susceptibility to nsCL/P in Arab populations, we investigated a newly recruited nsOFC sample from Yemen. METHODS: For each of the 15 currently known nsCL/P risk loci, the top single-nucleotide polymorphism (plus nine back-up variants) were genotyped in 242 nsCL/P cases and 420 healthy controls. RESULTS: Single-marker association analysis revealed significant associations for four loci (8q24, 9q22, 10q25, 13q31). The strongest association was for the European high risk locus at 8q24 (Pcorrected = 5.09 × 10(-4) ; heterozygous odds ratio = 1.74 (1.22-2.47), homozygous odds ratio = 2.47 (1.55-3.93). Five additional loci (1q32.2, 3q12, 8q21, 17q22, 20q12) showed nominal significance that did not withstand correction for multiple testing. Although the six remaining loci (1p22, 1p36, 2p21, 3p11, 15q22, 17p13) failed to reach nominal significance, the risk alleles were in the same direction as in the discovery studies. CONCLUSION: The results suggest that four of the 15 analyzed nsCL/P risk loci which were identified in European and Asian ethnicities significantly confer risk for nsCL/P in Arab populations.

The effect of dental material type and masticatory forces on periodontitis-derived subgingival microbiomes.

Restorative dental materials can frequently extend below the gingival margin, serving as a potential haven for microbial colonization, and altering the local oral microbiome to ignite infection. However, the contribution of dental materials on driving changes of the composition of the subgingival microbiome is under-investigated. This study evaluated the microbiome-modulating properties of three biomaterials, namely resin dental composites (COM), antimicrobial piezoelectric composites (BTO), and hydroxyapatite (HA), using an optimized in vitro subgingival microbiome model derived from patients with periodontal disease. Dental materials were subjected to static or cyclic loading (mastication forces) during biofilm growth. Microbiome composition was assessed by 16S rRNA gene sequencing. Dysbiosis was measured in terms of subgingival microbial dysbiosis index (SMDI). Biomaterials subjected to cyclic masticatory loads were associated with enhanced biofilm viability except on the antibacterial composite. Biomaterials held static were associated with increased biofilm biomass, especially on HA surfaces. Overall, the microbiome richness (Chao index) was similar for all the biomaterials and loading conditions. However, the microbiome diversity (Shannon index) for the HA beams was significantly different than both composites. In addition, beta diversity analysis revealed significant differences between composites and HA biomaterials, and between both loading conditions (static and cyclic). Under static conditions, microbiomes formed over HA surfaces resulted in increased dysbiosis compared to composites through the enrichment of periopathogens, including Porphyromonas gingivalis, Porphyromonas endodontalis, and Fretibacterium spp., and depletion of commensals such as Granulicatella and Streptococcus spp. Interestingly, cyclic loading reversed the dysbiosis of microbiomes formed over HA (depletion of periopathogenes) but increased the dysbiosis of microbiomes formed over composites (enrichment of Porphyromonas gingivalis and Fusobacterim nucleatum). Comparison of species formed on both composites (control and antibacterial) showed some differences. Commercial composites enriched Selenomonas spp. and depleted Campylobacter concisus. Piezoelectric composites effectively controlled the microbiome viability without significantly impacting the species abundance. Findings of this work open new understandings of the effects of different biomaterials on the modulation of oral biofilms and the relationship with oral subgingival infections.

Quantifying periodontitis-associated oral dysbiosis in tongue and saliva microbiomes-An integrated data analysis.

BACKGROUND: Periodontitis is primarily driven by subgingival biofilm dysbiosis. However, the quantification and impact of this periodontal dysbiosis on other oral microbial niches remain unclear. This study seeks to quantify the dysbiotic changes in tongue and salivary microbiomes resulting from periodontitis by applying a clinically relevant dysbiosis index to an integrated data analysis. METHODS: The National Center for Biotechnology Information (NCBI) database was searched to identify BioProjects with published studies on salivary and tongue microbiomes of healthy and periodontitis subjects. Raw sequence datasets were processed using a standardized bioinformatic pipeline and categorized by their ecological niche and periodontal status. The subgingival microbial dysbiosis index (SMDI), a dysbiosis index originally developed using the subgingival microbiome, was computed at species and genus levels and customized for each niche. Its diagnostic accuracy for periodontitis was evaluated using receiver operating characteristic curves. RESULTS: Four studies, contributing 328 microbiome samples, were included. At both species and genus levels, periodontitis samples had a higher SMDI, but the differences were only significant for subgingival biofilm and saliva (p < 0.001). However, SMDI showed good diagnostic accuracy for periodontitis status for all three niches (area under curve ranging from 0.76 to 0.90, p < 0.05). The dysbiosis index of subgingival biofilm was positively correlated with saliva consistently (p < 0.001) and with the tongue at the genus level (p = 0.036). CONCLUSIONS: While the impact on the tongue microbiome requires further investigation, periodontitis-associated dysbiosis affects the salivary microbiome and is quantifiable using the dysbiosis index. The diagnostic potential of salivary microbial dysbiosis as a convenient periodontal biomarker for assessing periodontal status has potential public health and clinical applications. PLAIN LANGUAGE SUMMARY: Periodontitis, a severe inflammation of the gums which causes bone loss, is a disease caused by an imbalance of good and bad bacteria under the gums. However, it is unclear how this bacterial imbalance in the gums affects the bacterial balance of other distinct parts of the mouth, such as the saliva and tongue. This study uses bacteria datasets of four previously published studies, contributing a total of 328 bacterial samples. The data were processed using a uniform data analysis workflow, and a bacterial score, the subgingival microbial dysbiosis index (SMDI), previously shown to capture periodontitis-associated bacteria imbalance, was calculated separately for samples from under the gums, the saliva, and the tongue. The SMDI was able to distinguish between health and periodontitis within each oral location, and in general, the scores were higher for periodontitis samples, though this difference was significant only for bacteria under the gums and in saliva. Saliva scores were also consistently correlated with bacteria under the gums. This study shows that periodontitis-associated bacterial imbalances are observed in oral locations beyond just under the gums, particularly the saliva. Thus, saliva bacteria may be used as a convenient biomarker for assessing gum disease, allowing for potential public health and clinical applications.

Global transcriptional response of oral squamous cell carcinoma cell lines to health-associated oral bacteria - an in vitro study.

Background: We have recently demonstrated that health-associated oral bacteria Streptococcus mitis, Neisseria flavescens, and Haemophilus parainfluenzae induce cytotoxicity in oral squamous cell carcinoma (OSCC) cell lines and downregulate CD36, a cancer-assocaited gene. Aim: To explore the effect of these three species on global transcriptome of OSCC cell lines. Methods: Gene expression of cell lines CAL27, SCC4 and SCC25 cocultured with the test species was assessed with Clariom-S Human microarray. Porphyromonas gingivalis was included as a pathogenic control. Data were analyzed using Ingenuity Pathway Analysis. Results: The results differed by species and cell line. Overall, the transcriptional changes by S. mitis were predominantly anti-cancer including inhibition of HOTAIR regulatory pathway, JAK/Stat signaling, cyclins/cyclin-dependent kinases, and endothelin1 signaling. H. parainfluenzae and N. flavescens resulted in a mix of pro- and anti-cancer responses including activation of acute phase response, pro-inflammatory interleukins signaling, TREM-1 signaling, and tumor microenvironment pathway; but downregulation of cell cycle by inhibition of cyclins and cyclin-dependent kinases. P. gingivalis had a predominantly pro-cancer effect limited to SCC4, including upregulation of inflammatory pathways, phospholipases and PI3K signaling. Conclusion: These findings provide a new insight into the role of commensal oral bacteria in OSCC. Animal studies are required to further explore them.

Tongue microbiome in children with autism spectrum disorder.

Background: A few recent studies have characterized the salivary microbiome in association with Autism Spectrum Disorder (ASD). Here, we sought to assess if there is an association between the tongue microbiome and ASD. Methods: Tongue scrapping samples were obtained from 25 children with ASD and 38 neurotypical controls. The samples were sequenced for the 16S rRNA gene (V1-V3) and the resultant high-quality reads were assigned to the species-level using our previously described BLASTn-based algorithm. Downstream analyses of microbial profiles were conducted using QIIME, LEfSe, and R. Results: Independent of grouping, Prevotella, Streptococcus, Leptotrichia, Veillonella, Haemophilus and Rothia accounted for > 60% of the average microbiome. Haemophilus parainfluenzae, Rothia mucilaginosa, Prevotella melaninogenica and Neisseria flavescens/subflava were the most abundant species. Species richness and diversity did not significantly differ between the study groups. Thirteen species and three genera were differentially abundant between the two groups, e.g. enrichment of Actinomyces odontolyticus and Actinomyces lingnae and depletion of Campylobacter concisus and Streptococcus vestibularis in the ASD group. However, none of them withstood adjustment for multiple comparisons. Conclusion: The tongue microbiome of children with ASD was not significantly different from that of healthy control children, which is largely consistent with results from the literature.

Experimental gingivitis in male khat (Catha edulis) chewers.

UNLABELLED: Whether or not khat chewing is detrimental to the periodontium remains uncertain. Findings from cross-sectional studies have been contradictory and, in most cases, uncontrolled for confounders. OBJECTIVES: to experimentally test the effect of khat chewing on formation of dental plaque and development of gingivitis. METHODS: This was a split-mouth, parallel-group, 20-day experimental gingivitis study involving non-smoking, young, male khat chewers (n = 8) and non-chewers (n = 9). Measurements of plaque index (PI), gingival index (GI), and bleeding on probing (BOP), as experimental outcomes, were performed on days 0, 10, and 20. Scores were compared between the two groups (parallel-group model) and between the khat-chewing and non-chewing sides (split-mouth model). RESULTS: All experimental outcomes significantly increased over time. Results from the two models were consistent. Khat chewing was associated with lower PI scores; however, differences were only significant at day 20. Despite scoring higher in baseline gingival inflammation, the khat chewers and khat-chewing sides showed significantly lower GI and BOP scores at days 10 and 20. The effect of khat chewing was evident on both the lingual and buccal aspects. CONCLUSIONS: The observed anti-plaque and anti-gingivitis properties indicate that khat chewing is probably not detrimental to the periodontium. The validity of previous findings supporting an opposite view is undermined by lack of control for confounders, particularly smoking.

Screening of Health-Associated Oral Bacteria for Anticancer Properties in vitro.

While extensive literature exists about the role of oral bacterial pathogens like Porphyromonas gingivalis and Fusobacterium nucleatum in oral squamous cell carcinoma (OSCC), the role of health-associated species has been largely unexplored. In this study, we assessed the effect of Streptococcus mitis, Rothia mucilaginosa, Neisseria flavescens, Haemophilus parainfluenzae, Lautropia mirabilis, and Veillonella parvula on proliferation and expression of marker genes (IL-6, TNF-α, MMP3, CD36, CCD1, and NANOG) in OSCC cell lines CAL27, SCC25, and SCC4. Porphyromonas gingivalis was included as a pathogenic control. Both bacterial lysates (3 concentrations) and live cells (3 MOIs) were tested. S. mitis, H. parainfluenzae, and N. flavescens resulted in substantial, dose-dependent reduction of proliferation, which was found to be mediated by H2O2 for the former and intracellular infection in the latter two species. However, only H. parainfluenzae showed differential antiproliferative effect against the cancer cell lines vs. the normal control (TIGKs). In the gene expression assays, the health-associated species mostly downregulated CD36, a gene that plays an important role in tumor growth and metastasis, while P. gingivalis upregulated it. IL6 and TNF expression, on the other hand, was upregulated by almost all species, particularly the Gram-negatives including P. gingivalis. The effect on other genes was less evident and varied significantly by cell line. This exploratory study is the first insight into how health-associated bacteria may interact with OSCC. Further studies to explore whether the observed effects may have implications for the prevention or treatment of oral cancer are warranted.

Supragingival mycobiome and inter-kingdom interactions in dental caries.

Background: Recent studies have reveled the presence of a complex fungal community (mycobiome) in the oral cavity. However, the role of oral mycobiome in dental caries and its interaction with caries-associated bacteria is not yet clear. Methods: Whole-mouth supragingival plaque samples from 30 children (6-10 years old) with no caries, early caries, or advanced caries were sequenced for internal transcribed spacer 2 (ITS-2). The mycobiome profiles were correlated with previously published bacteriome counterparts. Interaction among selected fungal and bacterial species was assessed by co-culture or spent media experiments. Results: Fungal load was extremely low. Candida, Malassezia, Cryptococcus, and Trichoderma spp. were the most prevalent/abundant taxa. Advanced caries was associated with significantly higher fungal load and prevalence/abundance of Candida albicans. Cryptococcus neoformans and Candida sake were significantly over-abundant in early caries, while Malassezia globosa was significantly enriched in caries-free subjects. C. albicans correlated with Streptococcus mutans and Scardovia wiggsiae among other caries-associated bacteria, while M. globosa inversely correlated with caries-associated bacteria. In-vitro, M. globosa demonstrated inhibitory properties against S. mutans. Conclusions: the results substantiate the potential role of the oral mycobiome, primarily Candida species, in dental caries. Inter-kingdom correlations and inhibition of S. mutans by M. globosa are worth further investigation.

Salivary Oral Microbiome of Children With Juvenile Idiopathic Arthritis: A Norwegian Cross-Sectional Study.

Background: The oral microbiota has been connected to the pathogenesis of rheumatoid arthritis through activation of mucosal immunity. The objective of this study was to characterize the salivary oral microbiome associated with juvenile idiopathic arthritis (JIA), and correlate it with the disease activity including gingival inflammation. Methods: Fifty-nine patients with JIA (mean age, 12.6 ± 2.7 years) and 34 healthy controls (HC; mean age 12.3 ± 3.0 years) were consecutively recruited in this Norwegian cross-sectional study. Information about demographics, disease activity, medication history, frequency of tooth brushing and a modified version of the gingival bleeding index (GBI) and the simplified oral hygiene index (OHI-S) was obtained. Microbiome profiling of saliva samples was performed by sequencing of the V1-V3 region of the 16S rRNA gene, coupled with a species-level taxonomy assignment algorithm; QIIME, LEfSe and R-package for Spearman correlation matrix were used for downstream analysis. Results: There were no significant differences between JIA and HC in alpha- and beta-diversity. However, differential abundance analysis revealed several taxa to be associated with JIA: TM7-G1, Solobacterium and Mogibacterium at the genus level; and Leptotrichia oral taxon 417, TM7-G1 oral taxon 352 and Capnocytophaga oral taxon 864 among others, at the species level. Haemophilus species, Leptotrichia oral taxon 223, and Bacillus subtilis, were associated with healthy controls. Gemella morbillorum, Leptotrichia sp. oral taxon 498 and Alloprevotella oral taxon 914 correlated positively with the composite juvenile arthritis 10-joint disease activity score (JADAS10), while Campylobacter oral taxon 44 among others, correlated with the number of active joints. Of all microbial markers identified, only Bacillus subtilis and Campylobacter oral taxon 44 maintained false discovery rate (FDR) < 0.1. Conclusions: In this exploratory study of salivary oral microbiome we found similar alpha- and beta-diversity among children with JIA and healthy. Several taxa associated with chronic inflammation were found to be associated with JIA and disease activity, which warrants further investigation.

Subgingival microbiome of experimental gingivitis: shifts associated with the use of chlorhexidine and N-acetyl cysteine mouthwashes.

This study aimed to demonstrate subgingival microbial changes associated with development, prevention, and treatment of experimental gingivitis using chlorhexidine (CHX) and N-acetylcysteine (NAC) mouthwashes. This randomized clinical trial comprised two parts: a 3-week prevention sub-study in which 30 study subjects were equally assigned to either mouthwash or placebo while developing experimental gingivitis; followed by a 2-week treatment sub-study in which 20 subjects with experimental gingivitis were assigned to either mouthwash. Subgingival samples were collected at the beginning and end of each sub-study for microbial profiling with 16S rRNA gene sequencing. As expected, CHX was effective in both preventing and reversing experimental gingivitis; NAC had a modest effect. Gingivitis was associated with enrichment of TM7 HOT-346/349, Tannerella HOT-286, Cardiobacterium valvarum, Campylobacter gracilis, Porphyromonas catoniae, Leptotrichia HOT-219, and Selen o monas spp. At the phylum/genus level, TM7 showed the strongest association. Gingival health was associated with increased abundance of Haemophilus parainfluenzae, Lautropia mirabilis, Rothia spp., Streptococcus spp., and Kingella oralis. CHX demonstrated largely indiscriminate antimicrobial action, resulting in significant drop in biomass and diversity. Our results substantiate the role of specific oral bacterial species in the development of gingivitis. They also indicate that NAC is not a promising mouthwash at the concentration tested.

Metagenome sequencing-based strain-level and functional characterization of supragingival microbiome associated with dental caries in children.

Studies of the microbiome associated with dental caries have largely relied on 16S rRNA sequence analysis, which is associated with PCR biases, low taxonomic resolution, and inability to accurately study functions. Here, we employed whole metagenome shotgun sequencing, coupled with high-resolution analysis algorithm, to analyze supragingival microbiomes from 30 children with or without dental caries. A total of 726 bacterial strains belonging to 406 species, in addition to 34 bacteriophages were identified. A core bacteriome was identified at the species and strain levels. Species of Prevotella, Veillonella, as yet unnamed Actinomyces, and Atopobium showed strongest association with caries; Streptococcus sp. AS14 and Leptotrichia sp. Oral taxon 225, among others, were overabundant in caries-free. For several species, the association was strain-specific. Furthermore, for some species, e.g. Streptococcus mitis and Streptococcus sanguinis, sister strains showed differential associations. Noteworthy, associations were also identified for phages: Streptococcus phage M102 with caries and Haemophilus phage HP1 with caries-free. Functionally, potentially relevant features were identified including urate, vitamin K2, and polyamine biosynthesis in association with caries; and three deiminases and lactate dehydrogenase with health. The results demonstrate new associations between the microbiome and dental caries at the strain and functional levels that need further investigation.

Differences in the Bacteriome of Smokeless Tobacco Products with Different Oral Carcinogenicity: Compositional and Predicted Functional Analysis.

Smokeless tobacco (ST) products vary significantly in their oral carcinogenicity. Much is known about the differences in the chemical, but not the bacterial, constituents of these products. In this study, we explored the composition and function of the bacteriome in ST products from four countries using quantitative polymerase chain reaction (qPCR) and 16S rRNA-based next generation sequencing. The bacterial load (16S rRNA copies/gram) was lowest in Swedish snus (3.4 × 106) and highest in Yemeni shammah (6.6 × 1011). A total of 491 species-level taxa, many of which are potentially novel, belonging to 178 genera and 11 phyla were identified. Species richness and diversity were highest for Swedish snus and lowest for Yemeni shammah. Bacillus, Paenibacillus, and Oceanobacillus spp. were the most abundant in American snuff; species of Pseudomonas, Massilia, Propionibacterium, Puniceispirillum, and Gloeothece predominated in Swedish snus. In Sudanese toombak, Facklamia, Desemzia, Atopostipes, and Lysinibacillus spp. accounted for the majority of the bacteriome. Yemeni shammah exclusively contained Bacillus spp. Functional prediction by phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) showed that genes encoding cadmium/zinc and nickel transport systems were enriched in the presumptively "high carcinogenicity" products. The bacteriome of ST products thus differed qualitatively, quantitatively, and functionally. The relevance of these differences, particularly with respect to nickel and cadmium, to oral carcinogenesis warrants further investigation.

Inflammatory bacteriome featuring Fusobacterium nucleatum and Pseudomonas aeruginosa identified in association with oral squamous cell carcinoma.

Studies on the possible association between bacteria and oral squamous cell carcinoma (OSCC) remain inconclusive, largely due to methodological variations/limitations. The objective of this study was to characterize the species composition as well as functional potential of the bacteriome associated with OSCC. DNA obtained from 20 fresh OSCC biopsies (cases) and 20 deep-epithelium swabs (matched control subjects) was sequenced for the V1-V3 region using Illumina's 2 × 300 bp chemistry. High quality, non-chimeric merged reads were classified to species level using a prioritized BLASTN-algorithm. Downstream analyses were performed using QIIME, PICRUSt, and LEfSe. Fusobacterium nucleatum subsp. polymorphum was the most significantly overrepresented species in the tumors followed by Pseudomonas aeruginosa and Campylobacter sp. Oral taxon 44, while Streptococcus mitis, Rothia mucilaginosa and Haemophilus parainfluenzae were the most significantly abundant in the controls. Functional prediction showed that genes involved in bacterial mobility, flagellar assembly, bacterial chemotaxis and LPS synthesis were enriched in the tumors while those responsible for DNA repair and combination, purine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, ribosome biogenesis and glycolysis/gluconeogenesis were significantly associated with the controls. This is the first epidemiological evidence for association of F. nucleatum and P. aeruginosa with OSCC. Functionally, an "inflammatory bacteriome" is enriched in OSSC.

A dysbiotic mycobiome dominated by Candida albicans is identified within oral squamous-cell carcinomas.

The aim of this study was to characterize the mycobiome associated with oral squamous-cell carcinoma (OSCC). DNA was extracted from 52 tissue biopsies (cases: 25 OSCC; controls: 27 intra-oral fibro-epithelial polyps [FEP]) and sequenced for the fungal internal transcribed spacer 2 region using Illumina™ 2 x300bp chemistry. Merged reads were classified to species level using a BLASTN-algorithm with UNITE's named species sequences as reference. Downstream analyses were performed using QIIME™ and linear discriminant analysis effect size. A total of 364 species representing 160 genera and two phyla (Ascomycota and Basidiomycota) were identified, with Candida and Malassezia making up 48% and 11% of the average mycobiome, respectively. However, only five species and four genera were detected in ≥50% of the samples. The species richness and diversity were significantly lower in OSCC. Genera Candida, Hannaella, and Gibberella were overrepresented in OSCC; Alternaria and  Trametes  were more abundant in FEP. Species-wise, Candida albicans, Candida etchellsii, and a Hannaella luteola-like species were enriched in OSCC, while aHanseniaspora uvarum-like species, Malassezia restricta, and Aspergillus tamarii were the most significantly abundant in FEP. In conclusion, a dysbiotic mycobiome dominated by C. albicans was found in association with OSCC, a finding worth further investigation.

Emerging role of bacteria in oral carcinogenesis: a review with special reference to perio-pathogenic bacteria.

Oral cancer, primarily oral squamous cell carcinoma (OSCC), continues to be a major global health problem with high incidence and low survival rates. While the major risk factors for this malignancy, mostly lifestyle related, have been identified, around 15% of oral cancer cases remain unexplained. In light of evidence implicating bacteria in the aetiology of some cancer types, several epidemiological studies have been conducted in the last decade, employing methodologies ranging from traditional culture techniques to 16S rRNA metagenomics, to assess the possible role of bacteria in OSCC. While these studies have demonstrated differences in microbial composition between cancerous and healthy tissues, they have failed to agree on specific bacteria or patterns of oral microbial dysbiosis to implicate in OSCC. On the contrary, some oral taxa, particularly Porphyromonas gingivalis and Fusobacterium nucleatum, show strong oral carcinogenic potential in vitro and in animal studies. Bacteria are thought to contribute to oral carcinogenesis via inhibition of apoptosis, activation of cell proliferation, promotion of cellular invasion, induction of chronic inflammation, and production of carcinogens. This narrative review provides a critical analysis of and an update on the association between bacteria and oral carcinogenesis and the possible mechanisms underlying it.