The Effects of Alcohol Drinking on Oral Microbiota in the Chinese Population

Oral Microbiome: A Review of Its Impact on Oral and Systemic Health

PURPOSE OF REVIEW

This review investigates the oral microbiome's composition, functions, influencing factors, connections to oral and systemic diseases, and personalized oral care strategies.

RECENT FINDINGS

The oral microbiome is a complex ecosystem consisting of bacteria, fungi, archaea, and viruses that contribute to oral health. Various factors, such as diet, smoking, alcohol consumption, lifestyle choices, and medical conditions, can affect the balance of the oral microbiome and lead to dysbiosis, which can result in oral health issues like dental caries, gingivitis, periodontitis, oral candidiasis, and halitosis. Importantly, our review explores novel associations between the oral microbiome and systemic diseases including gastrointestinal, cardiovascular, endocrinal, and neurological conditions, autoimmune diseases, and cancer. We comprehensively review the efficacy of interventions like dental probiotics, xylitol, oral rinses, fluoride, essential oils, oil pulling, and peptides in promoting oral health by modulating the oral microbiome.

SUMMARY

This review emphasizes the critical functions of the oral microbiota in dental and overall health, providing insights into the effects of microbial imbalances on various diseases. It underlines the significant connection between the oral microbiota and general health. Furthermore, it explores the advantages of probiotics and other dental care ingredients in promoting oral health and addressing common oral issues, offering a comprehensive strategy for personalized oral care.

Effect of chronic alcohol consumption on oral microbiota in rats with periodontitis

Background

The imbalance of oral microbiota can contribute to various oral disorders and potentially impact general health. Chronic alcohol consumption beyond a certain threshold has been implicated in influencing both the onset and progression of periodontitis. However, the mechanism by which chronic alcohol consumption affects periodontitis and its association with changes in the oral microbial community remains unclear.

Objective

This study used 16S rRNA gene amplicon sequencing to examine the dynamic changes in the oral microbial community of rats with periodontitis influenced by chronic alcohol consumption.

Methods

Twenty-four male Wistar rats were randomly allocated to either a periodontitis (P) or periodontitis + alcohol (PA) group. The PA group had unrestricted access to alcohol for 10 weeks, while the P group had access to water only. Four weeks later, both groups developed periodontitis. After 10 weeks, serum levels of alanine aminotransferase and aspartate aminotransferase in the rats' serum were measured. The oral swabs were obtained from rats, and 16S rRNA gene sequencing was conducted. Alveolar bone status was assessed using hematoxylin and eosin staining and micro-computed tomography.

Results

Rats in the PA group exhibited more severe periodontal tissue damage compared to those in the periodontitis group. Although oral microbial diversity remained stable, the relative abundance of certain microbial communities differed significantly between the two groups. Actinobacteriota and Desulfobacterota were more prevalent at the phylum level in the PA group. At the genus level, Cutibacterium, Tissierella, Romboutsia, Actinomyces, Lawsonella, Anaerococcus, and Clostridium_sensu_stricto_1 were significantly more abundant in the PA group, while Haemophilus was significantly less abundant. Additionally, functional prediction using Tax4Fun revealed a significant enrichment of carbohydrate metabolism in the PA group.

Conclusion

Chronic alcohol consumption exacerbated periodontitis in rats and influenced the composition and functional characteristics of their oral microbiota, as indicated by 16S rRNA gene sequencing results. These microbial alterations may contribute to the exacerbation of periodontitis in rats due to chronic alcohol consumption.

Oral microbiome and its relationship with oral cancer

ABSTRACT

As the initial point for digestion, the balance of oral microorganisms plays an important role in maintaining local and systemic health. Oral dysbiosis, or an imbalance in the oral microbial community, may lead to the onset of various diseases. The presence or abnormal increase of microbes in the oral cavity has attracted significant attention due to its complicated relationship with oral cancer. Oral cancer can remodel microbial profiles by creating a more beneficial microenvironment for its progression. On the other hand, altered microbial profiles can promote tumorigenesis by evoking a complex inflammatory response and affecting host immunity. This review analyzes the oncogenic potential of oral microbiome alterations as a driver and biomarker. Additionally, a potentially therapeutic strategy via the reversal of the oral microbiome dysbiosis in oral cancers has been discussed.

Whole-Genome Metagenomic Analysis of the Oral Microbiota in Patients with Obstructive Sleep Apnea Comorbid with Major Depressive Disorder

Background

Obstructive sleep apnea (OSA) patients commonly experience high rates of depression. This study aims to examine the oral microbiota characteristics of OSA and those with comorbid major depressive disorder (OSA+MDD) patients.

Methods

Participants were enrolled from Aug 2022 to Apr 2023. Polysomnography, psychiatrist interviews, and scales were used to diagnose OSA and MDD. Oral samples were collected from participants by rubbing swabs on buccal mucosa, palate, and gums. Oral microbiota was analyzed via whole-genome metagenomics and bioinformatic analysis followed sequencing. Venous blood was drawn to detect plasma inflammatory factor levels.

Results

The study enrolled 33 OSA patients, 28 OSA+MDD patients, and 28 healthy controls. Significant differences were found in 8 phyla, 229 genera, and 700 species of oral microbiota among the three groups. Prevotellaceae abundance in the OSA and OSA+MDD groups was significantly lower than that in healthy controls. Linear discriminant analysis effect size (LEfSe) analysis showed that Streptococcaceae and Actinobacteria were the characteristic oral microbiota of the OSA and OSA+MDD groups, respectively. KEGG analysis indicates 30 pathways were changed in the OSA and OSA+MDD groups compared with healthy controls, and 23 pathways were changed in the OSA group compared with the OSA+MDD group. Levels of IL-6 in the OSA+MDD group were significantly higher than in the healthy group, correlating positively with the abundance of Schaalia, Campylobacter, Fusobacterium, Alloprevotella, and Candidatus Nanosynbacter in the oral, as well as with Hamilton Anxiety Rating Scale and Hamilton Depression Rating Scale scores.

Conclusion

Significant differences in oral microbiota populations and gene function were observed among the three groups. OSA patients were characterized by a decreased abundance of Prevotellaceae and an increased abundance of Streptococcaceae. OSA+MDD patients had an increased abundance of Actinobacteria. IL-6 might regulate the relationship between depression and the oral microbiota in OSA+MDD patients.

Adolescent alcohol use is associated with differences in the diversity and composition of the oral microbiome

BACKGROUND

Adolescence is a sensitive stage of oral microbial development that often coincides with the initiation and escalation of alcohol use. Thus, adolescents may be particularly susceptible to alcohol-induced alterations in the oral microbiome, though minimal research has been done in this area. Understanding the connection between the oral microbiome and alcohol use during adolescence is important to understand fully the biological consequences of alcohol use to mitigate potential adverse outcomes.

METHODS

Saliva samples were collected from adolescents aged 17-19 who used alcohol heavily (n = 21, 52.4% female) and those who did not use alcohol or any other substances (n = 18, 44.4% female). We utilized 16S rRNA sequencing to examine differences in microbial diversity and composition between the groups.

RESULTS

For alpha diversity, evenness was significantly lower in the drinking group than the control group as indicated by Pielou's evenness, Shannon, and Simpson indices. There were no statistically significant findings for beta diversity. Differential abundance analyses revealed higher abundances of Rothia and Corynebacterium in the alcohol-using group using both centered-log-ratio and relative abundance normalization. These genera are known for their high capacity to convert alcohol into acetaldehyde, a toxic metabolite reported to play a role in the neurobiological effects of alcohol. An unclassified Clostridia UCG-014, Streptobacillus, Comamonas, unclassified Lachnospiraceae, and Parvimonas were also identified as significantly different between groups when using only one of the normalization techniques.

CONCLUSIONS

This is the first study designed specifically to compare the oral microbiome of adolescents who use alcohol with that of control participants. Our findings reveal distinct alcohol-related differences in microbial composition and taxon abundance, emphasizing the importance of understanding the impact on the oral microbiome of alcohol use during adolescence. Because the oral microbiome is malleable, this study provides foundational work for future prevention and intervention studies.

Analysis of the saliva microbiome in patients with immunoglobulin G4-related disease

OBJECTIVES

This article aims to investigate the saliva microbiome in patients with immunoglobulin G4-related disease (IgG4RD) compared with primary Sjögren's syndrome (SS).

METHODS

Saliva samples were collected from 11 IgG4RD and 11 SS patients who visited IMSUT Hospital, The Institute of Medical Science, The University of Tokyo. Deoxyribonucleic acid (DNA) was extracted from the samples, and primers were used to amplify the V3-V4 regions of bacterial and archaeal 16S ribosomal RNA (rRNA) genes, which was then analysed by paired-end sequencing. Amplicon reads were processed using QIIME2 to generate representative sequences. The Greengenes database was used to identify the bacterial flora in each sample and compare them between groups.

RESULTS

The IgG4RD and SS groups exhibited differences in bacterial diversity. Cluster analyses of attributed classification groups by species and disease showed that IgG4RD and SS cases formed individual clusters. Significant differences in relative abundance between IgG4RD and SS were observed for the following organisms: Mogibacterium (P = .0051), Solobacterium moorei (P = .0195), Slackia (P = .0356), and Moryella (P = .0455).

CONCLUSIONS

Salivary microbiome analysis of IgG4RD and SS patients revealed significantly higher relative proportions of Mogibacterium, S. moorei, Slackia, and Moryella bacteria in IgG4RD compared with SS.

Preliminary exploratory research on the application value of oral and intestinal meta-genomics in predicting subjects' occupations-A case study of the distinction between students and migrant workers

Background

In the field of forensic science, accurately determining occupation of an individual can greatly assist in resolving cases such as criminal investigations or disaster victim identifications. However, estimating occupation can be challenging due to the intricate relationship between occupation and various factors, including gender, age, living environment, health status, medication use, and lifestyle habits such as alcohol consumption and smoking. All of these factors can impact the composition of oral or gut microbial community of an individual.

Methods and results

In this study, we collected saliva and feces samples from individuals representing different occupational sectors, specifically students and manual laborers. We then performed metagenomic sequencing on the DNA extracted from these samples to obtain data that could be analyzed for taxonomic and functional annotations in five different databases. The correlation between occupation with microbial information was assisted from the perspective of α and β diversity, showing that individuals belonging to the two occupations hold significantly different oral and gut microbial communities, and that this correlation is basically not affected by gender, drinking, and smoking in our datasets. Finally, random forest (RF) models were built with recursive feature elimination (RFE) processes. Models with 100% accuracy in both training and testing sets were constructed based on three species in saliva samples or on a single pathway annotated by the KEGG database in fecal samples, namely, "ko04145" or Phagosome.

Conclusion

Although this study may have limited representativeness due to its small sample size, it provides preliminary evidence of the potential of using microbiome information for occupational inference.

The adolescent and young adult microbiome and its association with substance use: a scoping review

AIMS

The microbiome is a critical factor in health throughout human development. The aims of this scoping review are to (i) elucidate the differences between the youth (post-natal day 21-65 for rodents, 2-7 years for non-human primates, and 10-25 years for humans) microbiome with other life stages and (ii) identify youth-specific microbial changes associated with substance use.

METHODS

Peer-reviewed studies published up to May 2023 were identified in PubMed and SCOPUS and included gut and oral microbiome studies from rodents, non-human primates, and humans (N = 1733). Twenty-six articles were determined eligible based on inclusion criteria (aim 1: n = 19, aim 2: n = 7).

RESULTS

The adolescent and young adult oral and gut microbiomes are distinct compared to other life stages, within both non-human and human models. While there is limited research in this area, the microbiome appears to be vulnerable to substance use exposure earlier in life, including substances commonly initiated and escalated during adolescence and young adulthood (i.e. alcohol, cannabis, and tobacco).

CONCLUSIONS

Studies across the lifespan indicate that adolescence and young adulthood are distinct periods of development, where the microbiome is sensitive to exposures, including substance use. There is a need for more studies focused on the adolescent and young adult microbiome and substance use, as well as focused on the oral microbiome during this developmental period. Understanding the gut and oral microbiome during adolescence and young adulthood may provide insight into the pathophysiology of substance use disorders.

Alcohol drinking alters oral microbiota to modulate the progression of alcohol-related liver disease

Alcohol-related liver disease (ALD) is one of the leading causes of liver-related death worldwide. However, roles of oral microbiota in regulating the progression of ALD remain unknown. Here, we fed mice with control or ethanol diet to establish chronic-plus-binge ALD model. 16S ribosomal DNA sequencing was performed on oral and cecum samples. We demonstrated that alcohol drinking influenced bacterial richness, microbial structure, and composition in oral samples of ethanol-fed mice compared with control mice. Alcohol consumption also remodeled relationships among oral microbes and altered functions of oral microbiota. Furthermore, oral microbiota, such as Streptococcus, Helicobacter, Alloprevotella, and Psychrobacter were closely associated with ALD parameters. Finally, we observed Sutterellaceae_uncultured, Dyella, and Gemmatimonas possibly translocated along with oral-gut axis and positively correlated with the severity of ALD. Altogether, alcohol consumption reprogramed composition and functions of oral microbiota to promote ALD progression, suggesting that oral microbes might become a new target for ALD therapy.

The association between oral and gut microbiota in male patients with alcohol dependence

Introduction

The relationship between oral and gut microbiota in alcohol dependence (AD) is not well understood, particularly the effects of oral microbiota on the intestinal microbiota. The current study aimed to explore the association between oral and gut microbiota in AD to clarify whether oral microbiota could ectopically colonize into the gut.

Methods

16S rRNA sequence libraries were used to compare oral and gut microbial profiles in persons with AD and healthy controls (HC). Source Tracker and NetShift were used to identify bacteria responsible for ectopic colonization and indicate the driver function of ectopic colonization bacteria.

Results

The α-diversity of oral microbiota and intestinal microbiota was significantly decreased in persons with AD (all p < 0.05). Principal coordinate analysis indicated greater similarity between oral and gut microbiota in persons with AD than that in HC, and oral-gut overlaps in microbiota were found for 9 genera in persons with AD relative to only 3 genera in HC. The contribution ratio of oral microbiota to intestinal microbiota composition in AD is 5.26% based on Source Tracker，and the AD with ectopic colonization showed the daily maximum standard drinks, red blood cell counts, hemoglobin content, and PACS scores decreasing (all p < 0.05).

Discussion

Results highlight the connection between oral-gut microbiota in AD and suggest novel potential mechanistic possibilities.

Alteration of oral bacteriome of smokeless tobacco users and their association with oral cancer

Smokeless tobacco (SLT) is certainly one of the major risk factors associated with oral cancer. Disruption of oral microbiota-host homeostasis contributes to the progression of oral cancer. Here, we profiled SLT users' oral bacterial composition and inferred their functions by sequencing 16S rDNA V₃-V₄ region and PICRUSt2, respectively. Oral bacteriome of SLT users (with or without oral premalignant lesions), SLT with alcohol co-users, and non-SLT consumers were compared. Oral bacteriome is shaped primarily by SLT use and the incidence of oral premalignant lesions (OPL). A significantly increased bacterial α-diversity was monitored in SLT users with OPL compared to in SLT users without OPL and non-users, whereas β-diversity was significantly explained by OPL status. Overrepresented genera were Prevotella, Fusobacterium, Veillonella, Haemophilus, Capnocytophaga, and Leptotrichia in SLT users having OPL. LEfSe analysis identified 16 genera as a biomarker that were differentially abundant in SLT users having OPL. The functional prediction of genes significantly increased for several metabolic pathways, more importantly, were nitrogen metabolism, nucleotide metabolism, energy metabolism, and biosynthesis/biodegradation of secondary metabolites in SLT users having OPL. Furthermore, HPV-16 and EBV, but not HPV-18, were considerably connected with the SLT users having OPL. Overall, this study provides evidence that SLT utilization and OPL development are associated with oral bacteriome dysbiosis indicating the enrichment of bacterial species known for their contribution to oral carcinogenesis. Therefore, delineating the cancer-inducing bacterial population in SLT users will facilitate the future development of microbiome-targeted therapies. KEY POINTS: • SLT consumption significantly elevates oral bacterial diversity. • Prevalent significant genera are Prevotella, Veillonella, and Haemophilus in SLT users with OPL. • SLT promotes the occurrence of the cancer-inducing bacterial population.

From Mouth to Muscle: Exploring the Potential Relationship between the Oral Microbiome and Cancer-Related Cachexia

Cancer cachexia is a multifactorial wasting syndrome associated with skeletal muscle and adipose tissue loss, as well as decreased appetite. It affects approximately half of all cancer patients and leads to a decrease in treatment efficacy, quality of life, and survival. The human microbiota has been implicated in the onset and propagation of cancer cachexia. Dysbiosis, or the imbalance of the microbial communities, may lead to chronic systemic inflammation and contribute to the clinical phenotype of cachexia. Though the relationship between the gut microbiome, inflammation, and cachexia has been previously studied, the oral microbiome remains largely unexplored. As the initial point of digestion, the oral microbiome plays an important role in regulating systemic health. Oral dysbiosis leads to the upregulation of pro-inflammatory cytokines and an imbalance in natural flora, which in turn may contribute to muscle wasting associated with cachexia. Reinstating this equilibrium with the use of prebiotics and probiotics has the potential to improve the quality of life for patients suffering from cancer-related cachexia.

Association of general health and lifestyle factors with the salivary microbiota - Lessons learned from the ADDITION-PRO cohort

INTRODUCTION

Previous research indicates that the salivary microbiota may be a biomarker of oral as well as systemic disease. However, clarifying the potential bias from general health status and lifestyle-associated factors is a prerequisite of using the salivary microbiota for screening.

MATERIALS & METHODS

ADDDITION-PRO is a nationwide Danish cohort, nested within the Danish arm of the Anglo-Danish-Dutch Study of Intensive treatment in People with Screen-Detected Diabetes in Primary Care. Saliva samples from n=746 individuals from the ADDITION-PRO cohort were characterized using 16s rRNA sequencing. Alpha- and beta diversity as well as relative abundance of genera was examined in relation to general health and lifestyle-associated variables. Permutational multivariate analysis of variance (PERMANOVA) was performed on individual variables and all variables together. Classification models were created using sparse partial-least squares discriminant analysis (sPLSDA) for variables that showed statistically significant differences based on PERMANOVA analysis (p < 0.05).

RESULTS

Glycemic status, hemoglobin-A_1c (HbA_1c) level, sex, smoking and weekly alcohol intake were found to be significantly associated with salivary microbial composition (individual variables PERMANOVA, p < 0.05). Collectively, these variables were associated with approximately 5.8% of the observed differences in the composition of the salivary microbiota. Smoking status was associated with 3.3% of observed difference, and smoking could be detected with good accuracy based on salivary microbial composition (AUC 0.95, correct classification rate 79.6%).

CONCLUSIONS

Glycemic status, HbA_1c level, sex, smoking and weekly alcohol intake were significantly associated with the composition of the salivary microbiota. Despite smoking only being associated with 3.3% of the difference in overall salivary microbial composition, it was possible to create a model for detection of smoking status with a high correct classification rate. However, the lack of information on the oral health status of participants serves as a limitation in the present study. Further studies in other cohorts are needed to validate the external validity of these findings.

Oral Health Behaviors and Oral Health-Related Quality of Life Among Dental Patients in China: A Cross-Sectional Study

Background and Purpose

Oral health plays an important role in overall health. But little is known about the problems with oral health behaviors and oral health-related quality of life (OHRQoL) among dental patients in China. This study aimed to investigate oral health behaviors and OHRQoL, as well as to examine the effects of oral health behaviors and associated factors on OHRQoL among dental patients.

Methods

This cross-sectional study was conducted from June 2022 to July 2022 in the Department of Stomatology of the First Mobile General Hospital of Armed Police, Hebei, China. The five-item short form of the Oral Health Impact Profile (OHIP-5) was used to evaluate OHRQoL. Oral health behaviors were assessed by a 16-items oral health behavior questionnaire, and socio-demographic data were collected by a socio-demographic questionnaire. The t-test, one-way ANOVA, and multiple linear regression analysis were used to investigate the associations between the study variables.

Results

186 participants were included in the study. The average age of the participants was 24.62 years (SD = 10.67). The mean OHIP-5 score was 4.31 (SD =3.35). Oral health-related quality of life differed significantly by smoking history, history of alcohol consumption, work status, economic pressure, self-rated oral health status, daily brushing frequency, dental caries condition, and whether they take the initiative to learn about oral health. Multivariate analysis found that the self-rated oral health status and work status were significantly associated with the OHIP scores. The retired people and those with poor self-rated oral health displayed poor OHRQoL.

Conclusion

In general, dental patients' oral health needs to be improved, the majority of patients reported practicing poor oral health behaviors, among which the retired population and hose with poor self-rated oral health showed poor OHRQoL. OHRQoL in dental patients is a complex issue associated with social and behavioral factors.

The Intratumor Bacterial and Fungal Microbiome Is Characterized by HPV, Smoking, and Alcohol Consumption in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) tumor phenotypes and clinical outcomes are significantly influenced by etiological agents, such as HPV infection, smoking, and alcohol consumption. Accordingly, the intratumor microbiome has been increasingly implicated in cancer progression and metastasis. However, few studies characterize the intratumor microbial landscape of HNSCC with respect to these etiological agents. In this study, we aimed to investigate the bacterial and fungal landscape of HNSCC in association with HPV infection, smoking, and alcohol consumption. RNA-sequencing data were extracted from The Cancer Genome Atlas (TCGA) regarding 449 tissue samples and 44 normal samples. Pathoscope 2.0 was used to extract the microbial reads. Microbe abundance was compared to clinical variables, oncogenic signatures, and immune-associated pathways. Our results demonstrated that a similar number of dysregulated microbes was overabundant in smokers and nonsmokers, while heavy drinkers were characterized by an underabundance of dysregulated microbes. Conversely, the majority of dysregulated microbes were overabundant in HPV+ tumor samples when compared to HPV- tumor samples. Moreover, we observed that many dysregulated microbes were associated with oncogenic and metastatic pathways, suggesting their roles in influencing carcinogenesis. These microbes provide insights regarding potential mechanisms for tumor pathogenesis and progression with respect to the three etiological agents.

Exploratory studies of oral and fecal microbiome in healthy human aging

Growing evidence has linked an altered host fecal microbiome composition with health status, common chronic diseases, and institutionalization in vulnerable older adults. However, fewer studies have described microbiome changes in healthy older adults without major confounding diseases or conditions, and the impact of aging on the microbiome across different body sites remains unknown. Using 16S ribosomal RNA gene sequencing, we reconstructed the composition of oral and fecal microbiomes in young (23-32; mean = 25 years old) and older (69-94; mean = 77 years old) healthy community-dwelling research subjects. In both body sites, we identified changes in minor bacterial operational taxonomic units (OTUs) between young and older subjects. However, the composition of the predominant bacterial species of the healthy older group in both microbiomes was not significantly different from that of the young cohort, which suggests that dominant bacterial species are relatively stable with healthy aging. In addition, the relative abundance of potentially pathogenic genera, such as Rothia and Mycoplasma, was enriched in the oral microbiome of the healthy older group relative to the young cohort. We also identified several OTUs with a prevalence above 40% and some were more common in young and others in healthy older adults. Differences with aging varied for oral and fecal samples, which suggests that members of the microbiome may be differentially affected by aging in a tissue-specific fashion. This is the first study to investigate both oral and fecal microbiomes in the context of human aging, and provides new insights into interactions between aging and the microbiome within two different clinically relevant sites.

Nutritional factors influencing microbiota-mediated colonization resistance of the oral cavity: A literature review

The oral cavity is a key biocenosis for many distinct microbial communities that interact with both the external environment and internal body systems. The oral microbiota is a vital part of the human microbiome. It has been developed through mutual interactions among the environment, host physiological state, and microbial community composition. Indigenious microbiota of the oral cavity is one of the factors that prevent adhesion and invasion of pathogens on the mucous membrane, i.e., the development of the infectious process and thereby participating in the implementation of one of the mechanisms of local immunity-colonization resistance. The balance between bacterial symbiosis, microbial virulence, and host resistance ensures the integrity of the oral cavity. In this review we have tried to address how nutritional factors influence integrity of the oral indigenous microbiota and its involvement in colonization resistance.

Smokeless tobacco consumption induces dysbiosis of oral mycobiome: a pilot study

Smokeless tobacco (SLT) alters the oral microbiome of smokeless tobacco users. Dysbiosis of oral bacteriome has been determined; however, the mycobiome of SLT users has not been characterized. The oral mycobiome was assayed by amplification and sequencing of the fungal internal transcribed spacer (ITS1) region from oral swab samples of non-SLT users, SLT users (with or without oral lesions), and SLT with alcohol users. We observed that the richness and diversity of oral mycobiome were significantly decreased in SLT with oral lesions users than in non-users. The β-diversity analysis showed significant dissimilarity of oral mycobiome between non-users and SLT with oral lesions users. Linear discriminant analysis effect size and random forest analysis of oral mycobiome affirm that the genus Pichia was typical for SLT with oral lesions users. Prevalence of the fungal genus Pichia correlates positively with Starmerella, Mortierella, Fusarium, Calonectria, and Madurella, but is negatively correlated with Pyrenochaeta, Botryosporium, and Alternaria. Further, the determination of oral mycobiome functionality showed a high abundance of pathotroph-saprotroph-symbiotroph and animal pathogen-endophyte-epiphyte-undefined saprotroph at trophic and guild levels, respectively, indicating possibly major changes in normal growth repression of types of fungi. The oral mycobiome in SLT users was identified and comprehensively analyzed for the first time. SLT intake is associated with oral mycobiome dysbiosis and such alterations of the oral mycobiome may contribute to oral carcinogenesis in SLT users. This study will provide a basis for further large-scale investigations on the potential role of the mycobiome in SLT-induced oral cancer. KEY POINTS: • SLT induces dysbiosis of the oral microbiome that can contribute to oral cancer. • Oral mycobiome diversity is noticeably reduced in SLT users having oral lesions. • Occurrence of Pichia can be used as a biomarker for SLT users having oral lesions.