Pathophysiological microenvironments in oral candidiasis.

Oral candidiasis (OC), a prevalent opportunistic infection of the oral mucosa, presents a considerable health challenge, particularly in individuals with compromised immune responses, advanced age, and local predisposing conditions. A considerable part of the population carries Candida in the oral cavity, but only few develop OC. Therefore, the pathogenesis of OC may depend on factors other than the attributes of the fungus, such as host factors and other predisposing factors. Mucosal trauma and inflammation compromise epithelial integrity, fostering a conducive environment for fungal invasion. Molecular insights into the immunocompromised state reveal dysregulation in innate and adaptive immunity, creating a permissive environment for Candida proliferation. Detailed examination of Candida species (spp.) and their virulence factors uncovers a nuanced understanding beyond traditional C. albicans focus, which embrace diverse Candida spp. and their strategies, influencing adhesion, invasion, immune evasion, and biofilm formation. Understanding the pathophysiological microenvironments in OC is crucial for the development of targeted therapeutic interventions. This review aims to unravel the diverse pathophysiological microenvironments influencing OC development focusing on microbial, host, and predisposing factors, and considers Candida resistance to antifungal therapy. The comprehensive approach offers a refined perspective on OC, seeking briefly to identify potential therapeutic targets for future effective management.

Fungal diversity and drug susceptibility of the oral mycobiome of domestic dogs.

The purpose of this study was to characterize the variety and diversity of the oral mycobiome of domestic dogs and to identify the commensal and potentially pathogenic fungi present. Two hundred fifty-one buccal swabs from domestic dogs were obtained and struck onto a chromogenic fungal growth medium that distinguishes between fungal species based on colony color and morphology. After isolating and harvesting single colonies, genomic DNA was extracted from pure cultures. PCR was used to amplify a fungal-specific variable rDNA region of the genome, which was then sent for sequencing. Sequencing results were input into the NCBI BLAST database to identify individual components of the oral mycobiome of tested dogs. Of the 251 dogs swabbed, 73 had cultivable fungi present and 10 dogs had multiple fungal species isolated. Although the dogs did not show signs of oral infections at the time, we did find fungal species that cause pathogenicity in animals and humans. Among fungal isolates, Malassezia pachydermatis and species from the genus Candida were predominant. Following fungal isolate identification, antifungal drug susceptibility tests were performed on each isolate toward the medically important antifungal drugs including fluconazole, ketoconazole, and terbinafine. Drug susceptibility test results indicated that a large number of isolates had high MIC values for all three drugs. Exploring the oral mycobiome of dogs, as well as the corresponding drug susceptibility profiles, can have important implications for canine dental hygiene, health, and medical treatment. Identifying the microorganisms within the canine mouth can illustrate a common pathway for fungal pathogens of One Health concern to spread from our canine companions to humans.

Supragingival mycobiome of HIV-exposed-but-uninfected children reflects a stronger correlation with caries-free-associated taxa compared to HIV-infected or uninfected children.

IMPORTANCE: Globally, caries is among the most frequent chronic childhood disease, and the fungal component of the microbial community responsible is poorly studied despite evidence that fungi contribute to increased acid production exacerbating enamel demineralization. HIV infection is another global health crisis. Perinatal HIV exposure with infection are caries risk factors; however, the caries experience in the context of perinatal HIV exposure without infection is less clear. Using high-throughput amplicon sequencing, we find taxonomic differences that become pronounced during late-stage caries. Notably, we show a stronger correlation with health-associated taxa for HIV-exposed-but-uninfected children when compared to unexposed and uninfected children. This aligns with a lower incidence of caries in primary teeth at age 6 or less for exposed yet uninfected children. Ultimately, these findings could contribute to improved risk assessment, intervention, and prevention strategies such as biofilm disruption and the informed design of pro-, pre-, and synbiotic oral therapies.

Oral fungal profiling and risk of nasopharyngeal carcinoma: a population-based case-control study.

BACKGROUND: Dysbiosis of the oral mycobiome has been linked to some diseases, including cancers. However, the role of oral fungal communities in nasopharyngeal carcinoma (NPC) carcinogenesis has not previously been investigated. METHODS: We characterized the oral salivary fungal mycobiome in 476 untreated incident NPC patients and 537 population-based controls using fungal internal transcribed spacer (ITS)-2 sequencing. The relationship between oral fungal mycobiome and the risk of NPC was assessed through bioinformatic and biostatistical analyses. FINDINGS: We found that lower fungal alpha diversity was associated with an increased odds of NPC [lower vs. higher: observed features (adjusted odds ratio [OR] = 5.81, 95% confidence interval [CI] = 3.60-9.38); Simpson diversity (1.53, 1.03-2.29); Shannon diversity (2.03, 1.35-3.04)]. We also observed a significant difference in global fungal community patterns between cases and controls based on Bray-Curtis dissimilarity (P < 0.001). Carriage of oral fungal species, specifically, Saccharomyces cerevisiae, Candida tropicalis, Lodderomyces elongisporus, Candida albicans, and Fusarium poae, was associated with significantly higher odds of NPC, with ORs ranging from 1.56 to 4.66. Individuals with both low fungal and low bacterial alpha diversity had a profoundly elevated risk of NPC. INTERPRETATION: Our results suggest that dysbiosis in the oral mycobiome, characterized by a loss of fungal community diversity and overgrowth of several fungal organisms, is associated with a substantially increased risk of NPC. FUNDING: This work was funded by the US National Institutes of Health, the Swedish Research Council, the High-level Talents Research Start-up Project of Fujian Medical University, and the China Scholarship Council.

Mapping the human oral and gut fungal microbiota in patients with metabolic dysfunction-associated fatty liver disease.

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a phenotype of liver diseases associated with metabolic syndrome. The pathogenesis MAFLD remains unclear. The liver maintains is located near the intestine and is physiologically interdependent with the intestine via metabolic exchange and microbial transmission, underpinning the recently proposed "oral-gut-liver axis" concept. However, little is known about the roles of commensal fungi in the disease development. This study aimed to characterize the alterations of oral and gut mycobiota and their roles in MAFLD. Twenty-one MAFLD participants and 20 healthy controls were enrolled. Metagenomics analyses of saliva, supragingival plaques, and feces revealed significant alterations in the gut fungal composition of MAFLD patients. Although no statistical difference was evident in the oral mycobiome diversity within MAFLD and healthy group, significantly decreased diversities were observed in fecal samples of MAFLD patients. The relative abundance of one salivary species, five supragingival species, and seven fecal species was significantly altered in MAFLD patients. Twenty-two salivary, 23 supragingival, and 22 fecal species were associated with clinical parameters. Concerning the different functions of fungal species, pathways involved in metabolic pathways, biosynthesis of secondary metabolites, microbial metabolism in diverse environments, and carbon metabolism were abundant both in the oral and gut mycobiomes. Moreover, different fungal contributions in core functions were observed between MAFLD patients and the healthy controls, especially in the supragingival plaque and fecal samples. Finally, correlation analysis between oral/gut mycobiome and clinical parameters identified correlations of certain fungal species in both oral and gut niches. Particularly, Mucor ambiguus, which was abundant both in saliva and feces, was positively correlated with body mass index, total cholesterol, low-density lipoprotein, alanine aminotransferase, and aspartate aminotransferase, providing evidence of a possible "oral-gut-liver" axis. The findings illustrate the potential correlation between core mycobiome and the development of MAFLD and could propose potential therapeutic strategies.

The Human Mycobiome: Colonization, Composition and the Role in Health and Disease.

The mycobiome is the fungal component of the human microbial ecosystem that represents only a small part of this environment but plays an essential role in maintaining homeostasis. Colonization by fungi begins immediately after birth. The initial mycobiome is influenced by the gestational age of a newborn, birth weight, delivery method and feeding method. During a human's life, the composition of the mycobiome is further influenced by a large number of endogenous and exogenous factors. The most important factors are diet, body weight, age, sex and antibiotic and antifungal therapy. The human mycobiome inhabits the oral cavity, gastrointestinal tract, respiratory tract, urogenital tract and skin. Its composition can influence the gut-brain axis through immune and non-immune mediated crosstalk systems. It also interacts with other commensals of the ecosystem through synergistic and antagonistic relationships. Moreover, colonization of the gut by opportunistic fungal pathogens in immunocompromised individuals can lead to clinically relevant disease states. Thus, the mycobiome represents an essential part of the microbiome associated with a variety of physiological and pathological processes. This review summarizes the current knowledge on the composition of the mycobiome in specific sites of the human body and its role in health and disease.

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 ß-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.

Oral microbial diversity analysis among atrophic glossitis patients and healthy individuals.

Atrophic glossitis is a common disease in oral mucosal diseases. The Current studies have found the human oral cavity contains numerous and diverse microorganisms, their composition and diversity can be changed by various oral diseases. To understand the composition and diversity of oral microbiome in atrophic glossitis is better to explore the cause and mechanism of atrophic glossitis. The salivary microbiome is comprised of indigenous oral microorganisms that are specific to each person, exhibits long-term stability. We used llumina MiSeq high-throughput sequencing based on the V3-V4 region of the bacterial 16S rRNA gene and the internal transcribed spacer (ITS) region of fungal rRNA genes from saliva in atrophic glossitis patients and healthy individuals to explore the composition and diversity of oral microbiome. In our reports, it showed a lower diversity of bacteria and fungi in atrophic glossitis patients than in healthy individuals. The data further suggests that Lactobacillus and Saccharomycetales were potential indicators for the initiation and development of atrophic glossitis. Moreover, we also discuss the relationship between the oral microbial ecology and atrophic glossitis.

Citizen-science based study of the oral microbiome in Cystic fibrosis and matched controls reveals major differences in diversity and abundance of bacterial and fungal species.

Introduction: Cystic fibrosis (CF) is an autosomal genetic disease, associated with the production of excessively thick mucosa and with life-threatening chronic lung infections. The microbiota of the oral cavity can act as a reservoir or as a barrier for infectious microorganisms that can colonize the lungs. However, the specific composition of the oral microbiome in CF is poorly understood.Methods: In collaboration with CF associations in Spain, we collected oral rinse samples from 31 CF persons (age range 7-47) and matched controls, and then performed 16S rRNA metabarcoding and high-throughput sequencing, combined with culture and proteomics-based identification of fungi to survey the bacterial and fungal oral microbiome.Results: We found that CF is associated with less diverse oral microbiomes, which were characterized by higher prevalence of Candida albicans and differential abundances of a number of bacterial taxa that have implications in both the connection to lung infections in CF, as well as potential oral health concerns, particularly periodontitis and dental caries.Conclusion: Overall, our study provides a first global snapshot of the oral microbiome in CF. Future studies are required to establish the relationships between the composition of the oral and lung microbiomes in CF.

The Salivary Mycobiome Contains 2 Ecologically Distinct Mycotypes.

A broad range of fungi has been detected in molecular surveys of the oral mycobiome. However, knowledge is still lacking on interindividual variability of these communities and the ecologic and clinical significance of oral fungal commensals. In this cross-sectional study, we use internal transcribed spacer 1 amplicon sequencing to evaluate the salivary mycobiome in 59 subjects, 36 of whom were scheduled to receive cancer chemotherapy. Analysis of the broad population structure of fungal communities in the whole cohort identified 2 well-demarcated genus-level community types (mycotypes), with Candida and Malassezia as the main taxa driving cluster partitioning. The Candida mycotype had lower diversity than the Malassezia mycotype and was positively correlated with cancer and steroid use in these subjects, smoking, caries, utilizing a removable prosthesis, and plaque index. Mycotypes were also associated with metabolically distinct bacteria indicative of divergent oral environments, with aciduric species enriched in the Candida mycotype and inflammophilic bacteria increased in the Malassezia mycotype. Similar to their fungal counterparts, coexisting bacterial communities associated with the Candida mycotype showed lower diversity than those associated with the Malassezia mycotype, suggesting that common environmental pressures affected bacteria and fungi. Mycotypes were also seen in an independent cohort of 24 subjects, in which cultivation revealed Malassezia as viable oral mycobiome members, although the low-abundance Malassezia sympodialis was the only Malassezia species recovered. There was a high degree of concordance between the molecular detection and cultivability of Candida, while cultivation showed low sensitivity for detection of the Malassezia mycotype. Overall, our work provides insights into the oral mycobiome landscape, revealing 2 community classes with apparently distinct ecologic constraints and specific associations with coexisting bacteria and clinical parameters. The utility of mycotypes as biomarkers for oral diseases warrants further study.

Oral microbiome in down syndrome and its implications on oral health.

Introduction: The oral cavity harbors an abundant and diverse microbial community (i.e. the microbiome), whose composition and roles in health and disease have been the focus of intense research. Down syndrome (DS) is associated with particular characteristics in the oral cavity, and with a lower incidence of caries and higher incidence of periodontitis and gingivitis compared to control populations. However, the overall composition of the oral microbiome in DS and how it varies with diverse factors like host age or the pH within the mouth are still poorly understood. Methods: Using a Citizen-Science approach in collaboration with DS associations in Spain, we performed 16S rRNA metabarcoding and high-throughput sequencing, combined with culture and proteomics-based identification of fungi to survey the bacterial and fungal oral microbiome in 27 DS persons (age range 7-55) and control samples matched by geographical distribution, age range, and gender. Results: We found that DS is associated with low salivary pH and less diverse oral microbiomes, which were characterized by lower levels of Alloprevotella, Atopobium, Candidatus Saccharimonas, and higher amounts of Kingella, Staphylococcus, Gemella, Cardiobacterium, Rothia, Actinobacillus, and greater prevalence of Candida. Conclusion: Altogether, our study provides a first global snapshot of the oral microbiome in DS. Future studies are required to establish whether the observed differences are related to differential pathology in the oral cavity in DS.

Biodiversity of the human oral mycobiome in health and disease.

The organisms that colonize the human body over a lifetime are diverse, extensive and gargantuan. A fair proportion of the microbiota that constitutes this human microbiome live within our oral cavities mostly as harmonious associates causing only sporadic disease. An important core constituent of the microbiome is the mycobiome, representing various fungal genera. Up until recently, only a few species of fungi, mainly Candida species, were thought to constitute the human oral mycobiome. The reasons for this are manifold, although the uncultivable nature of many fungi in conventional laboratory media, and their complex genetic composition seem to be the major factors which eluded their detection over the years. Nevertheless, recent advances in computing and high-throughput sequencing such as next-generation sequencing (NGS) platforms have provided us a panoramic view of a totally new world of fungi that are human oral cohabitués. Their diversity is perplexing, and functionality yet to be deciphered. Here, we provide a glimpse of what is currently known of the oral mycobiome, in health and disease, with some future perspectives.

Microbial and inflammatory-based salivary biomarkers of head and neck squamous cell carcinoma.

Head and neck squamous cell carcinoma (HNSCC) patients often present with poor oral health, making it difficult to assess the relationship between oral microbes, inflammation, and carcinoma. This study investigates salivary microbes and inflammatory cytokines as biomarkers for HNSCC, with consideration of oral health. Saliva was collected from 30 participants, including 14 HNSCC patients and 16 participants representing both dentally compromised and healthy individuals. Bacterial and fungal communities were analyzed based on 16S rRNA gene and ITS1 amplicon sequencing, respectively, and concentrations of inflammatory cytokines were quantified using a cytometric bead array, with flow cytometry. Diversity-based analyses revealed that the bacterial communities of HNSCC patients were significantly different to those of the healthy control group but not the dentally compromised patients. Fungal communities were dominated by Candida, irrespective of cohort, with Candida albicans comprising ≥96% of fungal sequences in most HNSCC patients. Significantly higher concentrations of interleukin (IL)-1ß and IL-8 were detected in HNSCC and dentally compromised patients, when independently compared with healthy controls. IL-1ß and IL-8 concentrations were significantly positively correlated with the abundance of C. albicans. Our findings suggest that salivary microbial and inflammatory biomarkers of HNSCC are influenced by oral health.

Oral mycobiome in community-dwelling elderly and its relation to oral and general health conditions.

OBJECTIVE: Oral fungal infection is generally associated with dysbiosis related to antibiotic use, immunodeficiency, or frailty. However, fungal colonization in a typical population without apparent symptoms and its associated conditions are poorly understood. In this study, oral fungal colonization in community-dwelling and independently living elderly populations was evaluated and factors affecting fungal colonization were analyzed. SUBJECTS AND METHODS: The subjects (410; 181 males and 229 females) were 75-99 years of age; those under prior antibiotic use were excluded. Fungal populations in the saliva were evaluated by PCR-based molecular techniques. Body mass index (BMI), smoking habits, and oral health conditions were examined. RESULTS: Salivary fungal amounts exceeded 104  CFU/ml in 63 (15.4%) of 410 subjects. Candida albicans was most frequently detected (98.4%), followed by Candida glabrata (54.0%), and Candida dubliniensis (38.1%) in those subjects with fungi at 104  CFU/ml or over. Fungi at 104  CFU/ml or over in the presence of C. glabrata or C. dubliniensis was significantly associated with low BMI. CONCLUSIONS: Candida albicans, C. glabrata, and C. dubliniensis dominated the oral mycobiome in Japanese community-dwelling elderly. Lower BMI might signify compromised health status and thus could result in susceptibility to specific candidiasis by C. glabrata and C. dubliniensis.