Candida albicans enhances invasion of human gingival epithelial cells and gingival fibroblasts by Porphyromonas gingivalis

Candida Infections: The Role of Saliva in Oral Health-A Narrative Review

Candida species, particularly Candida albicans, are causative agents of oral infections to which immunocompromised patients are especially susceptible. Reduced saliva flow (xerostomia) can lead to Candida overgrowth, as saliva contains antibacterial components such as histatins and β-defensins that inhibit fungal growth and adhesion to the oral mucosa. Candida adheres to host tissues, forms biofilms, and secretes enzymes required for tissue invasion and immune evasion. Secretory asparaginyl proteinases (Saps) and candidalysin, a cytolytic peptide toxin, are vital to Candida virulence, and agglutinin-like sequence (Als) proteins are crucial for adhesion, invasion, and biofilm formation. C. albicans is a risk factor for dental caries and may increase periodontal disease virulence when it coexists with Porphyromonas gingivalis. Candida infections have been suggested to heighten the risk of oral cancer based on a relationship between Candida species and oral squamous cell carcinoma (OSCC) or oral potentially malignant disorder (OPMD). Meanwhile, β-glucan in the Candida cell wall has antitumor effects. In addition, Candida biofilms protect viruses such as herpesviruses and coxsackieviruses. Understanding the intricate interactions between Candida species, host immune responses, and coexisting microbial communities is essential for developing preventive and therapeutic strategies against oral Candida infections, particularly in immunocompromised individuals.

Periodontal Status and Herpesiviridae, Bacteria, and Fungi in Gingivitis and Periodontitis of Systemically Compromised Pediatric Subjects: A Systematic Review

BACKGROUND

Gingivitis and periodontitis are microbially associated diseases, with some features characteristic of pediatric age and others linked to systemic diseases. While the role of periodontal pathogenic bacteria is well recognized, the contribution of fungi and viruses, particularly Herpesviridae, remains controversial. Studies in adults have highlighted the presence of Herpesviridae, but evidence in pediatric subjects, especially systemically compromised, is limited. This systematic review aimed to assess periodontal status (e.g., health, gingivitis, periodontitis, necrotizing gingivitis, and/or periodontitis) and the subgingival and/or salivary microbial (bacterial, viral, and fungal) profile in systemically compromised pediatric (≤18 years) subjects with gingivitis and/or periodontitis compared to clinical periodontal health.

METHODS

The review protocol was registered on PROSPERO (CRD42024597695) and followed the PRISMA statement. Data from eight studies were descriptively analyzed and qualitatively assessed through ROBINS-I and JBI tools.

RESULTS

CMV was frequently detected, particularly in necrotizing gingivitis (19.40%). EBV was found in necrotizing gingivitis (20.69%) and periodontitis (10.34%); HSV was mainly associated with gingivitis and necrotizing gingivitis. Bacteria species in periodontitis included Porphyromonas gingivalis, Tannerella forsythia, Fusobacterium, and Campylobacter species. Candida albicans was detected in periodontitis, suggesting a fungal involvement in the disease's pathogenesis. Although the bacterial and fungal profile was not investigated, limited viral presence was noted in subjects with healthy periodontium, indicating a stable microbiome.

CONCLUSIONS

These findings underscore the dynamics of microbial interactions in the progression of periodontal disease in systemically compromised pediatric subjects.

Synergistic effects of Candida albicans and Porphyromonas gingivalis biofilms on epithelial barrier function in a 3D aspiration pneumonia model

Introduction

Polymicrobial infections involving Candida albicans and Porphyromonas gingivalis represent a significant challenge in maintaining epithelial barrier integrity. This study explores their synergistic effects on epithelial cells using an air-liquid interface (ALI) model.

Methods

Mixed-species biofilms were developed and analyzed for their impact on epithelial permeability and tight junction proteins. The effects of biofilm supernatants on IL-8 secretion and oxidative stress markers were also evaluated. The role of P. gingivalis proteases was assessed using a gingipain-null mutant (ΔKΔRAB) compared to the wild-type strain (W83). Survival experiments were conducted using Galleria mellonella larvae to examine the pathogenicity of dual-species biofilms.

Results

Mixed-species biofilms significantly increased epithelial permeability and disrupted tight junction proteins, as evidenced by reduced levels of ZO-1 and E-cadherin. These changes were accompanied by oxidative stress, characterized by decreased HO-1 expression and enhanced Bax/Bcl-xL ratios, indicating increased pro-apoptotic activity. Supernatants from dual-species biofilms demonstrated a pronounced effect on epithelial cells, modulating IL-8 secretion and exacerbating oxidative damage. C. albicans was identified as the dominant driver of pro-inflammatory responses, while P. gingivalis contributed through immune modulation and enzymatic activity, primarily via gingipains. The ΔKΔRAB mutant biofilms caused less epithelial disruption and oxidative stress compared to the wild-type, highlighting the critical role of gingipains in pathogenesis.

Discussion

Survival experiments using Galleria mellonella larvae supported these findings, highlighting the reduced survival associated with dual-species biofilms and the potential for high-dose antimicrobial therapies to mitigate this effect. These results emphasize the cooperative mechanisms of C. albicans and P. gingivalis in compromising epithelial barriers and underline the importance of combination therapies targeting both fungal and bacterial components in polymicrobial infections.

Candida species in periodontitis: A new villain or a new target?

OBJECTIVES

Recent research indicated that fungi might have a role in periodontitis alongside traditional periodontal pathogens. This state-of-the-art narrative review explores current concepts on the involvement of Candida species in periodontitis, and suggests the potential for ecological management of this disease.

DATA, SOURCES AND STUDY SELECTION

A literature search was conducted for a narrative review on Web of Science, PubMed, Medline and Scopus about periodontitis associated with Candida species. Published articles, including case reports, case series, observational and interventional clinical trials, and critical appraisals of the literature were retrieved and reviewed.

CONCLUSIONS

Several factors predispose individuals to periodontitis associated with Candida species. These include systemic diseases that lead to immunosuppression and oral environment changes such as cigarette smoking. While a consistent significant increase in the detection rate of Candida species in patients with periodontitis has not been universally observed, there is evidence linking Candida species to the severity of periodontitis and their potential to worsen the condition. Candida species may participate in the development of periodontitis in various ways, including cross-kingdom interactions with periodontal pathogens, changes in the local or systemic environment favoring the virulence of Candida species, and interactions between Candida-bacteria and host immunity.

CLINICAL SIGNIFICANCE

Mechanical plaque control is the most common treatment for periodontitis, but its effectiveness may be limited, particularly when dealing with systemic risk factors. Understanding the specific role of Candida in periodontitis illuminates innovative approaches for managing the ecological balance in periodontal health.

Porphyromonas gingivalis interaction with Candida albicans allows for aerobic escape, virulence and adherence

In the oral cavity Candida albicans interacts with many oral bacteria, including Porphyromonas gingivalis, both physically and metabolically. The aim of this in vitro study was to characterize these interactions and study their effects on the survival of P. gingivalis. First, metabolic interactions were evaluated by counting the colony forming units (CFU) after co-culturing. The results indicated that the anaerobic bacterium P. gingivalis survives under aerobic conditions when co-cultured with C. albicans. This is due to the oxygen consumption by C. albicans as determined by a reduction in survival upon the addition of Antimycin A. By measuring the protease activity, it was found that the presence of C. albicans induced gingipain activity by P. gingivalis, which is an important virulence factor. Adherence of P. gingivalis to hyphae of C. albicans was observed with a dynamic flow system. Using various C. albicans mutants, it was shown that the mechanism of adhesion was mediated by the cell wall adhesins, members of the agglutinin-like sequence (Als) family: Als3 and Als1. Furthermore, the two microorganisms could be co-cultured into forming a biofilm in which P. gingivalis can survive under aerobic culturing conditions, which was imaged using scanning electron microscopy. This study has further elucidated mechanisms of interaction, virulence acquisition and survival of P. gingivalis when co-cultured with C. albicans. Such survival could be essential for the pathogenicity of P. gingivalis in the oxygen-rich niches of the oral cavity. This study has emphasized the importance of interaction between different microbes in promoting survival, virulence and attachment of pathogens, which could be essential in facilitating penetration into the environment of the host.

Mouthwash Effects on the Oral Microbiome: Are They Good, Bad, or Balanced?

This narrative review describes the oral microbiome, and its role in oral health and disease, before considering the impact of commonly used over-the-counter (OTC) mouthwashes on oral bacteria, viruses, bacteriophages, and fungi that make up these microbial communities in different niches of the mouth. Whilst certain mouthwashes have proven antimicrobial actions and clinical effectiveness supported by robust evidence, this review reports more recent metagenomics evidence, suggesting that mouthwashes such as chlorhexidine may cause "dysbiosis," whereby certain species of bacteria are killed, leaving others, sometimes unwanted, to predominate. There is little known about the effects of mouthwashes on fungi and viruses in the context of the oral microbiome (virome) in vivo, despite evidence that they "kill" certain viral pathogens ex vivo. Evidence for mouthwashes, much like antibiotics, is also emerging with regards to antimicrobial resistance, and this should further be considered in the context of their widespread use by clinicians and patients. Therefore, considering the potential of currently available OTC mouthwashes to alter the oral microbiome, this article finally proposes that the ideal mouthwash, whilst combatting oral disease, should "balance" antimicrobial communities, especially those associated with health. Which antimicrobial mouthwash best fits this ideal remains uncertain.

The Role of Gingival Fibroblasts in the Pathogenesis of Periodontitis

Gingival fibroblasts (GFs) are essential components of the periodontium, which are responsible for the maintenance of tissue structure and integrity. However, the physiological role of GFs is not restricted to the production and remodeling of the extracellular matrix. GFs also act as sentinel cells that modulate the immune response to oral pathogens invading the gingival tissue. As an important "nonclassical" component of the innate immune system, GFs respond to bacteria and damage-related signals by producing cytokines, chemokines, and other inflammatory mediators. Although the activation of GFs supports the elimination of invading bacteria and the resolution of inflammation, their uncontrolled or excessive activation may promote inflammation and bone destruction. This occurs in periodontitis, a chronic inflammatory disease of the periodontium initiated and sustained by dysbiosis. In the inflamed gingival tissue, GFs acquire imprinted proinflammatory phenotypes that promote the growth of inflammophilic pathogens, stimulate osteoclastogenesis, and contribute to the chronicity of inflammation. In this review, we discuss the biological functions of GFs in healthy and inflamed gingival tissue, highlighting recent studies that provide insight into their role in the pathogenesis of periodontal diseases. We also draw parallels with the recently discovered fibroblast populations identified in other tissues and their roles in health and disease. This knowledge should be used in future studies to discover more about the role of GFs in periodontal diseases, especially chronic periodontitis, and to identify therapeutic strategies targeting their pathological interactions with oral pathogens and the immune system.

Cross-kingdom Microbial Interactions Within the Oral Cavity and Their Implications for Oral Disease

Purpose of Review

This review serves to highlight the cross-kingdom interactions that can occur within the human oral cavity between fungus Candida albicans and oral bacteria, and their impact on the delicate balance between oral health and disease.

Recent Findings

A growing number of physical, chemical, and metabolic networks have been identified that underpin these cross-kingdom interactions. Moreover, these partnerships are often synergistic and can modulate microbial burden or virulence. This, in turn, can drive the onset or progression of oral diseases such as dental caries, periodontitis, denture-associated stomatitis, and oral cancer.

Summary

The impact of cross-kingdom interactions on the cellular, biochemical, and communal composition of oral microbial biofilms is increasingly clear. With growing insight into these processes at the molecular level, so this knowledge can be used to better inform the development of novel strategies to manipulate the oral microbiota to promote oral health and combat oral disease.

Mechanisms of Porphyromonas gingivalis to translocate over the oral mucosa and other tissue barriers

Introduction

The oral pathogen Porphyromonas gingivalis is not only associated with periodontitis but also with systemic diseases elsewhere in the body. The mechanisms by which P. gingivalis travels from the oral cavity to other organs in the body are largely unknown. This review describes the four putative mechanisms supported by experimental evidence, which enable translocation of P. gingivalis over the oral mucosa, endothelial barriers and subsequent dissemination into the bloodstream.

Mechanisms

The first mechanism: proteolytic enzymes secreted by P. gingivalis degrade adhesion molecules between tissue cells, and the extracellular matrix. This weakens the structural integrity of the mucosa and allows P. gingivalis to penetrate the tissue. The second is transcytosis: bacteria actively enter tissue cells and transfer to the next layer or the extracellular space. By travelling from cell to cell, P. gingivalis reaches deeper structures. Thirdly, professional phagocytes take up P. gingivalis and travel to the bloodstream where P. gingivalis is released. Lastly, P. gingivalis can adhere to the hyphae forming Candida albicans. These hyphae can penetrate the mucosal tissue, which may allow P. gingivalis to reach deeper structures.

Conclusion

More research could elucidate targets to inhibit P. gingivalis dissemination and prevent the onset of various systemic diseases.

Innate immune response of human periodontal ligament fibroblasts via the Dectin-1/Syk pathway

Introduction. A diverse microbiota including fungi exists in the subgingival sites of patients with chronic periodontitis. The cell wall of Candida albicans, the most abundant fungal species, contains β-glucan. Dectin-1 binds β-glucan and participates in fungal recognition.Gap statement. Human periodontal ligament fibroblasts (PDLFs) are present in the periodontal ligament and synthesize immunomodulatory cytokines that influence the local response to infections. However, the expression and role of Dectin-1 in PDLFs have not been explored.Aim. This study aimed to determine if PDLFs express Dectin-1 and induce innate immune responses through Dectin-1 and the signalling molecule Syk.Methodology. The expression of Dectin-1 in PDLFs was determined by flow cytometry, western blotting and confocal microscopy. Real-time PCR and Western blotting were used to determine the immune response of PDLFs stimulated with β-glucan-rich zymosan and C. albicans.Results. Dectin-1 was constitutively expressed in PDLFs. Zymosan induced the expression of cytokines, including IL6, IL1B and IL17A, and the chemokine IL8. Zymosan also induced the expression of the antimicrobial peptide β-defensin-1 (DEFB1). Further, the phosphorylation of Syk and NF-κB occurred upon Dectin-1 activation. Notably, heat-killed C. albicans induced the expression of IL6, IL17A, IL8 and DEFB1, and this activation was suppressed by the Syk inhibitor, R406.Conclusion. These findings indicate that the Dectin-1/Syk pathway induces an innate immune response of PDLFs, which may facilitate the control of oral infections such as candidiasis and periodontitis.

Cross-kingdom interaction between Candida albicans and oral bacteria

Candida albicans is a symbiotic fungus that commonly colonizes on oral mucosal surfaces and mainly affects immuno-compromised individuals. Polymicrobial interactions between C. albicans and oral microbes influence the cellular and biochemical composition of the biofilm, contributing to change clinically relevant outcomes of biofilm-related oral diseases, such as pathogenesis, virulence, and drug-resistance. Notably, the symbiotic relationships between C. albicans and oral bacteria have been well-documented in dental caries, oral mucositis, endodontic and periodontal diseases, implant-related infections, and oral cancer. C. albicans interacts with co-existing oral bacteria through physical attachment, extracellular signals, and metabolic cross-feeding. This review discusses the bacterial-fungal interactions between C. albicans and different oral bacteria, with a particular focus on the underlying mechanism and its relevance to the development and clinical management of oral diseases.

Can polyphenolic surface modifications prevent fungal colonization of titanium dental implants?

Oral biofilms can be a major health problem causing infections and chronic inflammation of mucosal tissue. While much effort is put in the investigation of bacteria in biofilms, the role of fungi is often neglected, despite Candida albicans playing a key role in the formation of multispecies oral biofilms. With the rise of antibiotic resistance, new strategies to reduce microbial growth need to be found. Therefore, plant derived polyphenolic molecules have been suggested to reduce both adhesion and growth of pathogenic bacteria and fungi. In this study, we investigated the use of polyphenolic coatings to reduce adhesion and biofilm formation of C. albicans BWP17 on titanium implants. Tannic acid and pyrogallol coatings altered the hydrophobic and charge properties of titanium surfaces, and both compounds were gradually released as active molecules over time. Despite such effects, we found no significant inhibition on growth and biofilm formation of C. Albicans, indicating that the release of active molecules from the coatings did not reach relevant inhibitory concentrations. However, a potential antibiofilm effect was observed by the pH-dependent disassembly of the polyphenolic layer, which caused the biofilm to detach. Hence, further efforts are required to create tailored implant surfaces, which sustainably reduce microbial growth and adhesion.

Patients with obstructive sleep apnea can favor the predisposing factors of periodontitis by the presence of P. melaninogenica and C. albicans, increasing the severity of the periodontal disease

Objective

The aim of this study was to analyze the cultivable oral microbiota of patients with obstructive sleep apnea (OSA) and its association with the periodontal condition.

Methods

The epidemiology profile of patients and their clinical oral characteristics were determined. The microbiota was collected from saliva, subgingival plaque, and gingival sulcus of 93 patients classified into four groups according to the periodontal and clinical diagnosis: Group 1 (n = 25), healthy patients; Group 2 (n = 17), patients with periodontitis and without OSA; Group 3 (n = 19), patients with OSA and without periodontitis; and Group 4 (n = 32), patients with periodontitis and OSA. Microbiological samples were cultured, classified, characterized macroscopically and microscopically, and identified by MALDI-TOF-MS. The distribution of complexes and categories of microorganisms and correlations were established for inter- and intra-group of patients and statistically evaluated using the Spearman r test (p-value <0.5) and a multidimensional grouping analysis.

Result

There was no evidence between the severity of OSA and periodontitis (p = 0.2813). However, there is a relationship between the stage of periodontitis and OSA (p = 0.0157), with stage III periodontitis being the one with the highest presence in patients with severe OSA (prevalence of 75%; p = 0.0157), with more cases in men. The greatest distribution of the complexes and categories was found in oral samples of patients with periodontitis and OSA (Group 4 P-OSA); even Candida spp. were more prevalent in these patients. Periodontitis and OSA are associated with comorbidities and oral conditions, and the microorganisms of the orange and red complexes participate in this association. The formation of the dysbiotic biofilm was mainly related to the presence of these complexes in association with Candida spp.

Conclusion

Periodontopathogenic bacteria of the orange complex, such as Prevotella melaninogenica, and the yeast Candida albicans, altered the cultivable oral microbiota of patients with periodontitis and OSA in terms of diversity, possibly increasing the severity of periodontal disease. The link between yeasts and periodontopathogenic bacteria could help explain why people with severe OSA have such a high risk of stage III periodontitis. Antimicrobial approaches for treating periodontitis in individuals with OSA could be investigated in vitro using polymicrobial biofilms, according to our findings.

Co-Infection of Oral Candida albicans and Porphyromonas gingivalis Is Associated with Active Periodontitis in Middle-Aged and Older Japanese People

Background and Objectives: Candida albicans can be detected in subgingival sites of patients with periodontitis. However, the association between oral Candida albicans and periodontitis has not been fully elucidated in Japanese adults. The aim of this study is to clarify the relationship between oral Candida albicans infection/co-infection of oral C. albicans and Porphyromonas gingivalis and periodontitis among middle-aged and older Japanese people. Materials and Methods: Eighty-six patients (mean age 70.4 years) who visited the Hiroshima University Hospital from April to September 2021 were investigated in this study. Oral swab samples were collected from the tongue surface. C. albicans and P. gingivalis DNA was detected by real-time PCR using specific DNA primer sets. C. albicans-positive participants were classified into two groups according to the presence or absence of intron insertion of C. albicans DNA by PCR analysis. Results: C. albicans was detected in 22 (25.6%) of the 86 patients. Patients in their 80s recorded a higher C. albicans-positive rate (35.3%) compared with other participants. However, there was no significant association between the C. albicans positivity rate and clinical parameters such as sex, age, systemic disease, denture use, or oral health status. Of the 22 C. albicans-positive participants, 10 participants (45.5%) had C. albicans with intron insertion; 70% of participants who had C. albicans with intron insertion exhibited ≥6 mm probing depth. C. albicans/P. gingivalis co-infection was found in 12 patients (14%). Importantly, binomial logistic regression analysis revealed that C. albicans/P. gingivalis co-infection was significantly associated with ≥6 mm periodontal pockets with bleeding on probing (p = 0.02). Conclusions: Co-infection of C. albicans and P. gingivalis is involved in active periodontitis in middle-aged and older people.

In it together: Candida-bacterial oral biofilms and therapeutic strategies

Under natural environmental settings or in the human body, the majority of microorganisms exist in complex polymicrobial biofilms adhered to abiotic and biotic surfaces. These microorganisms exhibit symbiotic, mutualistic, synergistic, or antagonistic relationships with other species during biofilm colonization and development. These polymicrobial interactions are heterogeneous, complex and hard to control, thereby often yielding worse outcomes than monospecies infections. Concerning fungi, Candida spp., in particular, Candida albicans is often detected with various bacterial species in oral biofilms. These Candida-bacterial interactions may induce the transition of C. albicans from commensal to pathobiont or dysbiotic organism. Consequently, Candida-bacterial interactions are largely associated with various oral diseases, including dental caries, denture stomatitis, periodontitis, peri-implantitis, and oral cancer. Given the severity of oral diseases caused by cross-kingdom consortia that develop hard-to-remove and highly drug-resistant biofilms, fundamental research is warranted to strategically develop cost-effective and safe therapies to prevent and treat cross-kingdom interactions and subsequent biofilm development. While studies have shed some light, targeting fungal-involved polymicrobial biofilms has been limited. This mini-review outlines the key features of Candida-bacterial interactions and their impact on various oral diseases. In addition, current knowledge on therapeutic strategies to target Candida-bacterial polymicrobial biofilms is discussed.

Cross-kingdom microbial interactions in dental implant-related infections: is Candida albicans a new villain?

Candida albicans, an oral fungal opportunistic pathogen, has shown the ability to colonize implant surfaces and has been frequently isolated from biofilms associated with dental implant-related infections, possibly due to its synergistic interactions with certain oral bacteria. Moreover, evidence suggests that this cross-kingdom interaction on implant can encourage bacterial growth, leading to increased fungal virulence and mucosal damage. However, the role of Candida in implant-related infections has been overlooked and not widely explored or even considered by most microbiological analyses and therapeutic approaches. Thus, we summarized the scientific evidence regarding the ability of C. albicans to colonize implant surfaces, interact in implant-related polymicrobial biofilms, and its possible role in peri-implant infections as far as biologic plausibility. Next, a systematic review of preclinical and clinical studies was conducted to identify the relevance and the gap in the existing literature regarding the role of C. albicans in the pathogenesis of peri-implant infections.

Candida albicans and Candida dubliniensis in Periodontitis in Adolescents and Young Adults

Aim

This study aims to evaluate the association of Candida albicans and Candida dubliniensis with periodontitis in adolescents and young adults in a Moroccan population.

Methods

426 subjects aged between 12 and 25 years were recruited for the study. A pool of plaque sample was taken. Samples were cultured on Sabouraud Chloramphenicol medium at 37°C for 24–48 hours and then identified by the Vitek 2 YST system. Clinical data and presence of Candida albicans and Candida dubliniensis were analyzed using Jamovi (Version 1.8).

Results

Candida albicans was observed in 25 subjects among 68 diseased patients (37%) and in 60 subjects among 358 healthy patients (17%). It can be reported that under normal yeast conditions, there is a statistically significant difference between these two groups (P < 0.001). Candida dubliniensis was more prevalent in periodontitis than in healthy subjects (P=0.026). Regarding clinical variables, subgroups of periodontitis subjects showed significant statistical differences for periodontal probing depth, clinical attachment loss, and number of decayed teeth in advanced periodontitis in comparison with initial or mild periodontitis. The results also indicate that the presence of the two species of Candida is not related to gender or age (P > 0.05) nor related to the severity of the periodontal disease in this population.

Conclusion

Within the limits of our study, Candida albicans is more frequently associated with periodontitis. The potential role of C. albicans in periodontitis pathogenesis is very complex. More studies on biofilm associated with different forms of periodontitis are necessary. It is also important to assess the coexistence of periodontitis and caries and the associated biofilms.

Expression of anti-fungal peptide, β-defensin 118 in oral fibroblasts induced by C. albicans β-glucan-containing particles

Objective:

Methodology:

Results:

Conclusion:

Analysis of Salivary Mycobiome in a Cohort of Oral Squamous Cell Carcinoma Patients From Sudan Identifies Higher Salivary Carriage of Malassezia as an Independent and Favorable Predictor of Overall Survival

Background

Microbial dysbiosis and microbiome-induced inflammation have emerged as important factors in oral squamous cell carcinoma (OSCC) tumorigenesis during the last two decades. However, the “rare biosphere” of the oral microbiome, including fungi, has been sparsely investigated. This study aimed to characterize the salivary mycobiome in a prospective Sudanese cohort of OSCC patients and to explore patterns of diversities associated with overall survival (OS).

Materials and Methods

Unstimulated saliva samples (n = 72) were collected from patients diagnosed with OSCC (n = 59) and from non-OSCC control volunteers (n = 13). DNA was extracted using a combined enzymatic–mechanical extraction protocol. The salivary mycobiome was assessed using a next-generation sequencing (NGS)-based methodology by amplifying the ITS2 region. The impact of the abundance of different fungal genera on the survival of OSCC patients was analyzed using Kaplan–Meier and Cox regression survival analyses (SPPS).

Results

Sixteen genera were identified exclusively in the saliva of OSCC patients. Candida, Malassezia, Saccharomyces, Aspergillus, and Cyberlindnera were the most relatively abundant fungal genera in both groups and showed higher abundance in OSCC patients. Kaplan–Meier survival analysis showed higher salivary carriage of the Candida genus significantly associated with poor OS of OSCC patients (Breslow test: p = 0.043). In contrast, the higher salivary carriage of Malassezia showed a significant association with favorable OS in OSCC patients (Breslow test: p = 0.039). The Cox proportional hazards multiple regression model was applied to adjust the salivary carriage of both Candida and Malassezia according to age (p = 0.029) and identified the genus Malassezia as an independent predictor of OS (hazard ratio = 0.383, 95% CI = 0.16–0.93, p = 0.03).

Conclusion

The fungal compositional patterns in saliva from OSCC patients were different from those of individuals without OSCC. The fungal genus Malassezia was identified as a putative prognostic biomarker and therapeutic target for OSCC.

Counter-Acting Candida albicans-Staphylococcus aureus Mixed Biofilm on Titanium Implants Using Microbial Biosurfactants

This study aimed to grow a fungal-bacterial mixed biofilm on medical-grade titanium and assess the ability of the biosurfactant R89 (R89BS) coating to inhibit biofilm formation. Coated titanium discs (TDs) were obtained by physical absorption of R89BS. Candida albicans-Staphylococcus aureus biofilm on TDs was grown in Yeast Nitrogen Base, supplemented with dextrose and fetal bovine serum, renewing growth medium every 24 h and incubating at 37 °C under agitation. The anti-biofilm activity was evaluated by quantifying total biomass, microbial metabolic activity and microbial viability at 24, 48, and 72 h on coated and uncoated TDs. Scanning electron microscopy was used to evaluate biofilm architecture. R89BS cytotoxicity on human primary osteoblasts was assayed on solutions at concentrations from 0 to 200 μg/mL and using eluates from coated TDs. Mixed biofilm was significantly inhibited by R89BS coating, with similar effects on biofilm biomass, cell metabolic activity and cell viability. A biofilm inhibition >90% was observed at 24 h. A lower but significant inhibition was still present at 48 h of incubation. Viability tests on primary osteoblasts showed no cytotoxicity of coated TDs. R89BS coating was effective in reducing C. albicans-S. aureus mixed biofilm on titanium surfaces and is a promising strategy to prevent dental implants microbial colonization.

Occurrence of Candida albicans in Periodontitis

Background

Periodontal diseases are the result of an imbalance between the microbiota and immune defense. The role of yeast in the pathogenesis of these diseases has been studied. This study aims to assess the occurrence of Candida albicans in periodontitis.

Materials and Methods

Fifty subjects were recruited for the study (15 healthy individuals and 35 periodontitis subjects). The periodontal examination and plaque sampling were carried out for all patients. Candida albicans identification was based on culture, direct examination, and polymerase chain reaction. The statistical analysis was performed by SPSS 20 (SPSS Inc., Chicago, IL, USA).

Results

Twenty percent of the diseased group harbored Candida albicans which was slightly higher than in the healthy group (7%), suggesting that, under normal conditions, yeast does not grow easily in subgingival sites. However, no significant difference between the healthy and periodontitis groups (p=0.23) was found. Our results also indicated that the presence of Candida albicans was neither gender nor age related in the studied groups.

Conclusion

The results of this study suggest that Candida albicans occurs in periodontitis. More studies are needed to clarify the potential role of this yeast in different stages and forms of the disease.

The oralome and its dysbiosis: New insights into oral microbiome-host interactions

The oralome is the summary of the dynamic interactions orchestrated between the ecological community of oral microorganisms (comprised of up to approximately 1000 species of bacteria, fungi, viruses, archaea and protozoa - the oral microbiome) that live in the oral cavity and the host. These microorganisms form a complex ecosystem that thrive in the dynamic oral environment in a symbiotic relationship with the human host. However, the microbial composition is significantly affected by interspecies and host-microbial interactions, which in turn, can impact the health and disease status of the host. In this review, we discuss the composition of the oralome and inter-species and host-microbial interactions that take place in the oral cavity and examine how these interactions change from healthy (eubiotic) to disease (dysbiotic) states. We further discuss the dysbiotic signatures associated with periodontitis and caries and their sequalae, (e.g., tooth/bone loss and pulpitis), and the systemic diseases associated with these oral diseases, such as infective endocarditis, atherosclerosis, diabetes, Alzheimer's disease and head and neck/oral cancer. We then discuss current computational techniques to assess dysbiotic oral microbiome changes. Lastly, we discuss current and novel techniques for modulation of the dysbiotic oral microbiome that may help in disease prevention and treatment, including standard hygiene methods, prebiotics, probiotics, use of nano-sized drug delivery systems (nano-DDS), extracellular polymeric matrix (EPM) disruption, and host response modulators.

Microbial interactions and immunity response in oral Candida species

Oral candidiasis are among the most common noncommunicable diseases, related with serious local and systemic illnesses. Although these infections can occur in all kinds of patients, they are more recurrent in immunosuppressed ones such as patients with HIV, hepatitis, cancer or under long antimicrobial treatments. Candida albicans continues to be the most frequently identified Candida spp. in these disorders, but other non-C. albicans Candida are rising. Understanding the immune responses involved in oral Candida spp. infections is a key feature to a successful treatment and to the design of novel therapies. In this review, we performed a literature search in PubMed and WoS, in order to examine and analyze common oral Candida spp.-bacteria/Candida-Candida interactions and the host immunity response in oral candidiasis.

Subgingival fungi, Archaea, and viruses under the omics loupe

The microbial communities that inhabit the gingival crevice are responsible for the pathological processes that affect the periodontium. The changes in composition and function of subgingival bacteria as disease develops have been extensively studied. Subgingival communities, however, also contain fungi, Archaea, and viruses, which could contribute to the dysbiotic processes associated with periodontal diseases. High-throughput DNA sequencing has facilitated a better understanding of the mycobiome, archaeome, and virome. However, the number of studies available on the nonbacterial components of the subgingival microbiome remains limited in comparison with publications focusing on bacteria. Difficulties in characterizing fungal, archaeal, and viral populations arise from the small portion of the total metagenome mass they occupy and lack of comprehensive reference genome databases. In addition, specialized approaches potentially introducing bias are required to enrich for viral particles, while harsh methods of cell lysis are needed to recover nuclei acids from certain fungi. While the characterization of the subgingival diversity of fungi, Archaea and viruses is incomplete, emerging evidence suggests that they could contribute in different ways to subgingival dysbiosis. Certain fungi, such as Candida albicans are suggested to facilitate colonization of bacterial pathogens. Methanogenic Archaea are associated with periodontitis severity and are thought to partner synergistically with bacterial fermenters, while viruses may affect immune responses or shape microbial communities in ways incompletely understood. This review describes the manner in which omics approaches have improved our understanding of the diversity of fungi, Archaea, and viruses within subgingival communities. Further characterization of these understudied components of the subgingival microbiome is required, together with mechanistic studies to unravel their ecological role and potential contributions to dysbiosis.

Critically Appraising the Significance of the Oral Mycobiome

Recent efforts to understand the oral microbiome have focused on its fungal component. Since fungi occupy a low proportion of the oral microbiome biomass, mycobiome studies rely on sequencing of internal transcribed spacer (ITS) amplicons. ITS-based studies usually detect hundreds of fungi in oral samples. Here, we review the oral mycobiome, critically appraising the significance of such large fungal diversity. When harsh lysis methods are used to extract DNA, 2 oral mycobiome community types (mycotypes) are evident, each dominated by only 1 genus, either Candida or Malassezia. The rest of the diversity in ITS surveys represents low-abundance fungi possibly acquired from the environment and ingested food. So far, Candida is the only genus demonstrated to reach a significant biomass in the oral cavity and clearly shown to be associated with a distinct oral ecology. Candida thrives in the presence of lower oral pH and is enriched in caries, with mechanistic studies in animal models suggesting it participates in the disease process by synergistically interacting with acidogenic bacteria. Candida serves as the main etiological agent of oral mucosal candidiasis, in which a Candida-bacteriome partnership plays a key role. The function of other potential oral colonizers, such as lipid-dependent Malassezia, is still unclear, with further studies needed to establish whether Malassezia are metabolically active oral commensals. Low-abundance oral mycobiome members acquired from the environment may be viable in the oral cavity, and although they may not play a significant role in microbiome communities, they could serve as opportunistic pathogens in immunocompromised hosts. We suggest that further work is needed to ascertain the significance of oral mycobiome members beyond Candida. ITS-based surveys should be complemented with other methods to determine the in situ biomass and metabolic state of fungi thought to play a role in the oral environment.

RANK-RANKL signaling upregulates Il-10 mRNA expression in mucosal Candida infection in vivo

Osteoprotegerin (OPG) prevents binding of receptor activator of nuclear factor-kappa B ligand (RANKL) to RANK. Recent studies have reported that immune cell RANK-RANKL interactions are critical to the infection process. Candida albicans is an opportunistic pathogenic fungus and a common cause of candidiasis. This study utilized an orally inoculated mouse model of C. albicans infection to determine whether superficial or systemic candidiasis was associated with alterations in RANK/RANKL/OPG expression. Invasive systemic C. albicans infection increased serum OPG levels in mice. In addition, tongue Opg, Rankl, and Rank mRNA expression were upregulated in mice with superficial oral cavity C. albicans infection. Moreover, administration of exogenous soluble RANKL upregulated Rank and interleukin-10 (Il-10) mRNA in superficially infected tissue, suggesting suppression of localized inflammation. Taken together, these findings suggested that RANK/RANKL/OPG signaling contributes to the pathogenesis of candidiasis. This is the first in vivo study to identify a relationship between this opportunistic infection and the RANK/RANKL/OPG axis.

Peptidylarginine Deiminase of Porphyromonas gingivalis Modulates the Interactions between Candida albicans Biofilm and Human Plasminogen and High-Molecular-Mass Kininogen

Microorganisms that create mixed-species biofilms in the human oral cavity include, among others, the opportunistic fungus Candida albicans and the key bacterial pathogen in periodontitis, Porphyromonas gingivalis. Both species use arsenals of virulence factors to invade the host organism and evade its immune system including peptidylarginine deiminase that citrullinates microbial and host proteins, altering their function. We assessed the effects of this modification on the interactions between the C. albicans cell surface and human plasminogen and kininogen, key components of plasma proteolytic cascades related to the maintenance of hemostasis and innate immunity. Mass spectrometry was used to identify protein citrullination, and microplate tests to quantify the binding of modified plasminogen and kininogen to C. albicans cells. Competitive radioreceptor assays tested the affinity of citrullinated kinins to their specific cellular receptors. The citrullination of surface-exposed fungal proteins reduced the level of unmodified plasminogen binding but did not affect unmodified kininogen binding. However, the modification of human proteins did not disrupt their adsorption to the unmodified fungal cells. In contrast, the citrullination of kinins exerted a significant impact on their interactions with cellular receptors reducing their affinity and thus affecting the role of kinin peptides in the development of inflammation.

Fungal-Bacterial Interactions in Health and Disease

Fungi and bacteria encounter each other in various niches of the human body. There, they interact directly with one another or indirectly via the host response. In both cases, interactions can affect host health and disease. In the present review, we summarized current knowledge on fungal-bacterial interactions during their commensal and pathogenic lifestyle. We focus on distinct mucosal niches: the oral cavity, lung, gut, and vagina. In addition, we describe interactions during bloodstream and wound infections and the possible consequences for the human host.

Microbiome Dependent Regulation of Tregs and Th17 Cells in Mucosa

Mammals co-exist with resident microbial ecosystem that is composed of an incredible number and diversity of bacteria, viruses and fungi. Owing to direct contact between resident microbes and mucosal surfaces, both parties are in continuous and complex interactions resulting in important functional consequences. These interactions govern immune homeostasis, host response to infection, vaccination and cancer, as well as predisposition to metabolic, inflammatory and neurological disorders. Here, we discuss recent studies on direct and indirect effects of resident microbiota on regulatory T cells (T_regs) and Th17 cells at the cellular and molecular level. We review mechanisms by which commensal microbes influence mucosa in the context of bioactive molecules derived from resident bacteria, immune senescence, chronic inflammation and cancer. Lastly, we discuss potential therapeutic applications of microbiota alterations and microbial derivatives, for improving resilience of mucosal immunity and combating immunopathology.

Heat-killed Candida albicans augments synthetic bacterial component-induced proinflammatory cytokine production

Candida albicans can enhance the invasion of oral epithelial cells by Porphyromonas gingivalis, although the fungus is not a periodontal pathogen. In this study, we investigated whether C. albicans augments proinflammatory cytokine production by mouse macrophage-like J774.1 cells incubated with synthetic bacterial components. Mouse macrophage-like J774.1 cells, mouse primary splenocytes, human THP-1 cells, and A549 cells were pretreated with or without heat-killed C. albicans (HKCA) or substitutes for C. albicans cell wall components in 96-well flat-bottomed plates. Cells were then washed and incubated with Pam₃CSK₄, a Toll-like receptor (TLR) 2 ligand, or lipid A, a TLR4 ligand. Culture supernatants were analyzed by ELISA for secreted IL-6, MCP-1, TNF-α, and IL-8. HKCA augmented TLR ligand-induced proinflammatory cytokine production by J774.1 cells, mouse splenocytes, and THP-1 cells, but not A549 cells. However, IL-6, MCP-1, and TNF-α production induced by Pam₃CSK₄ or lipid A was not augmented when cells were pretreated with curdlan, a dectin-1 ligand, or mannan, a dectin-2 ligand. In contrast, pretreatment of cells with TLR ligands upregulated the production of IL-6 and TNF-α, but not MCP-1, induced by Pam₃CSK₄ or lipid A. The results suggest that C. albicans augments synthetic bacterial component-induced cytokine production by J774.1 cells via the TLR pathway, but not the dectin-1 or dectin-2 pathway.

Comparative analysis of expression of microbial sensing molecules in mucosal tissues with periodontal disease

Host-derived pattern recognition receptors (PRRs) are necessary for effective innate immune engagement of pathogens that express microbial-associated molecular patterns (MAMP) ligands for these PRRs. This study used a nonhuman primate model to evaluate the expression of these sensing molecules in gingival tissues. Macaca mulatta aged 12-24 with a healthy periodontium (n = 13) or periodontitis (n = 11) provided gingival tissues for assessment of naturally-occurring periodontitis. An additional group of animals (12-23 years; n = 18) was subjected to a 5 month longitudinal study examining the initiation and progression of periodontitis, RNA was isolated and microarray analysis conducted for gene expression of the sensing PRRs. The results demonstrated increased expression of various PRRs in naturally-occurring established periodontitis. Selected PRRs also correlated with both bleeding on probing (BOP) and pocket depth (PD) in the animals. The longitudinal model demonstrated multiple TLRs, as well as selected other PRRs that were significantly increased by 2 weeks during initiation of the lesion. While gene expression levels of various PRRs correlated with BOP and PD at baseline and resolution of disease, few correlated with these clinical parameters during initiation and progression of the lesion. These findings suggest that the levels of various PRRs are affected in established periodontitis lesions, and that PRR expression increased most dramatically during the initiation of the disease process, presumably in response to the juxtaposed microbial challenge to the tissues and goal of reestablishing homeostasis.

Candida Interactions with the Oral Bacterial Microbiota

The human oral cavity is normally colonized by a wide range of microorganisms, including bacteria, fungi, Archaea, viruses, and protozoa. Within the different oral microenvironments these organisms are often found as part of highly organized microbial communities termed biofilms, which display consortial behavior. Formation and maintenance of these biofilms are highly dependent on the direct interactions between the different members of the microbiota, as well as on the released factors that influence the surrounding microbial populations. These complex biofilm dynamics influence oral health and disease. In the latest years there has been an increased recognition of the important role that interkingdom interactions, in particular those between fungi and bacteria, play within the oral cavity. Candida spp., and in particular C. albicans, are among the most important fungi colonizing the oral cavity of humans and have been found to participate in these complex microbial oral biofilms. C. albicans has been reported to interact with individual members of the oral bacterial microbiota, leading to either synergistic or antagonistic relationships. In this review we describe some of the better characterized interactions between Candida spp. and oral bacteria.

Fungal-Host Interaction: Curcumin Modulates Proteolytic Enzyme Activity of Candida albicans and Inflammatory Host Response In Vitro

Current treatments for Candida albicans infection are limited due to the limited number of antifungal drugs available and the increase in antifungal resistance. Curcumin is used as a spice, food preservative, flavoring, and coloring agent that has been shown to have many pharmacological activities. Thus, this study evaluated the modulatory effects of curcumin on major virulence factors associated with the pathogenicity of C. albicans. The minimum inhibitory concentration (MIC) of curcumin against C. albicans (SC5314) was determined. Biofilm formation was quantified and the proteinase and phospholipase secretion was measured. The cytotoxicity was tested in oral fibroblast cells. A cocultured model was used to analyze the gene expression of proinflammatory cytokines (IL-1β, IL-1α, and IL-6) from host cells, as well SAP-1 and PLB-1 by RT-PCR. The MIC was between 6.25 and 12.5 µM, and the activity of proteinase enzyme was significantly decreased in biofilms treated with curcumin. However, proteinase gene expression was not downregulated after curcumin treatment. Furthermore, gene expressions of host inflammatory response, IL-1β and IL-1α, were significantly downregulated after exposure to curcumin. In conclusion, curcumin exhibited antifungal activity against C. albicans and modulated the proteolytic enzyme activities without downregulating the gene expression. In host inflammatory response, curcumin downregulated IL-1β and IL-1α gene expression.

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.

The activity of bacterial peptidylarginine deiminase is important during formation of dual-species biofilm by periodontal pathogen Porphyromonas gingivalis and opportunistic fungus Candida albicans

Porphyromonas gingivalis, an anaerobic Gram-negative bacterium critically involved in the development of human periodontitis, belongs to the late colonizers of the oral cavity. The success of this pathogen in the host colonization and infection results from the presence of several virulence factors, including extracellular peptidylarginine deiminase (PPAD), an enzyme that converts protein arginine residues to citrullines. A common opportunistic fungal pathogen of humans, Candida albicans, is also frequently identified among microorganisms that reside at subgingival sites. The aim of the current work was to verify if protein citrullination can influence the formation of mixed biofilms by both microorganisms under hypoxic and normoxic conditions. Quantitative estimations of the bacterial adhesion to fungal cells demonstrated the importance of PPAD activity in this process, since the level of binding of P. gingivalis mutant strain deprived of PPAD was significantly lower than that observed for the wild-type strain. These results were consistent with mass spectrometric detection of the citrullination of selected surface-exposed C. albicans proteins. Furthermore, a viability of P. gingivalis cells under normoxia increased in the presence of fungal biofilm compared with the bacteria that formed single-species biofilm. These findings suggest a possible protection of these strict anaerobes under unfavorable aerobic conditions by C. albicans during mixed biofilm formation.

Community Development between Porphyromonas gingivalis and Candida albicans Mediated by InlJ and Als3

The pleiomorphic yeast Candida albicans is a significant pathogen in immunocompromised individuals. In the oral cavity, C. albicans is an inhabitant of polymicrobial communities, and interspecies interactions promote hyphal formation and biofilm formation. C. albicans colonizes the subgingival area, and the frequency of colonization increases in periodontal disease. In this study, we investigated the interactions between C. albicans and the periodontal pathogen Porphyromonas gingivalisC. albicans and P. gingivalis were found to coadhere in both the planktonic and sessile phases. Loss of the internalin-family protein InlJ abrogated adhesion of P. gingivalis to C. albicans, and recombinant InlJ protein competitively inhibited interspecies binding. A mutant of C. albicans deficient in expression of major hyphal protein Als3 showed diminished binding to P. gingivalis, and InlJ interacted with Als3 heterologously expressed in Saccharomyces cerevisiae Transcriptional profiling by RNA sequencing (RNA-Seq) established that 57 genes were uniquely upregulated in an InlJ-dependent manner in P. gingivalis-C. albicans communities, with overrepresentation of those corresponding to 31 gene ontology terms, including those associated with growth and division. Of potential relevance to the disease process, C. albicans induced upregulation of components of the type IX secretion apparatus. Collectively, these findings indicate that InlJ-Als3-dependent binding facilitates interdomain community development between C. albicans and P. gingivalis and that P. gingivalis has the potential for increased virulence within such communities.IMPORTANCE Many diseases involve the concerted actions of microorganisms assembled in polymicrobial communities. Inflammatory periodontal diseases are among the most common infections of humans and result in destruction of gum tissue and, ultimately, in loss of teeth. In periodontal disease, pathogenic communities can include the fungus Candida albicans; however, the contribution of C. albicans to the synergistic virulence of the community is poorly understood. Here we characterize the interactions between C. albicans and the keystone bacterial pathogen Porphyromonas gingivalis and show that coadhesion mediated by specific proteins results in major changes in gene expression by P. gingivalis, which could serve to increase pathogenic potential. The work provides significant insights into interdomain interactions that can enhance our understanding of diseases involving a multiplicity of microbial pathogens.

Extracellular galectin-1 enhances adhesion to and invasion of oral epithelial cells by Porphyromonas gingivalis

Galectin-1 and galectin-3 are C-type lectin receptors that bind to lipopolysaccharide in the cell wall of gram-negative bacteria. In this study, we investigated the effects of galectin-1 and galectin-3 on adhesion to and invasion of the human gingival epithelial cell line Ca9-22 by Porphyromonas gingivalis, a periodontal pathogenic gram-negative bacterium. Recombinant galectin-1, but not galectin-3, enhanced P. gingivalis adhesion and invasion, although both galectins bound similarly to P. gingivalis. Flow cytometry also revealed that Ca9-22 cells express low levels of galectin-1 and moderate levels of galectin-3. Ca9-22 cells in which galectin-3 was knocked-down did not exhibit enhanced P. gingivalis adhesion and invasion. Similarly, specific antibodies to galectin-1 and galectin-3 did not inhibit P. gingivalis adhesion and invasion. These results suggest that soluble galectin-1, but not galectin-3, may exacerbate periodontal disease by enhancing the adhesion to and invasion of host cells by periodontal pathogenic bacteria.

Gastrointestinal colonisation and systemic spread of Candida albicans in mice treated with antibiotics and prednisolone

Normally, Candida albicans is a commensal microbe that resides in the human oral cavity, gut and vagina. However, the fungus can cause mucosal and systemic infections in immunocompromised individuals. The mechanism by which local mucosal infections progress to systemic candidiasis is poorly understood. Here, a murine model of gastrointestinal (GI) candidiasis was developed by inoculation of the oral cavity, followed by treatment with tetracycline (TC) and prednisolone (PSL). Temporal progression from a local infection of the oral cavity to a systemic infection was then monitored. Histological analysis of tissues from mice treated with both TC and PSL revealed massive infiltration of the tongue and stomach by hyphae. PSL increased the fungal burden in the tongue, stomach and small intestine, and facilitated dissemination to the spleen, kidney and liver within 3 days post-infection. Treatment with both TC and PSL supressed interferon (IFN)-γ and interleukin (IL)-17 (cytokines that play key roles in host defence against fungal infection) levels in the tongue, which were induced by C. albicans infection. In addition, the mucosal layer of the small intestine of mice treated with both TC and PSL was almost destroyed by the fungal infection; this may be a critical event that allows passage of the fungus across the mucosa and into the systemic circulation. Thus, this mouse model is useful for studying mechanisms underlying progression of C. albicans from a local infection of the oral cavity to a systemic infection in immunocompromised individuals.

The oral fungal mycobiome: characteristics and relation to periodontitis in a pilot study

Background

The oral fungal microbiome (mycobiome) is not well characterized, particularly in relation to oral diseases such as periodontal disease. We aimed to describe and compare the oral mycobiome of subjects with and without periodontal disease.

Results

We characterized the oral mycobiome in 30 adult subjects (15 with periodontal disease, 15 with good oral health) by sequencing the taxonomically informative pan-fungal internal transcribed spacer (ITS) gene in DNA extracted from oral wash samples. We observed at least 81 genera and 154 fungal species across all samples. Candida and Aspergillus were the most frequently observed genera (isolated from 100% of participants), followed by Penicillium (97%), Schizophyllum (93%), Rhodotorula (90%), and Gibberella (83%). Candida and Aspergillus were also the most highly abundant genera in the samples (median relative abundance = 21% and 44%, respectively). Aspergillus niger was the most highly abundant species in the samples (median relative abundance = 44%). We did not observe significant differences in overall oral mycobiome diversity or composition between participants with periodontal disease and participants with good oral health, nor did we observe significant differences in phylum through species level taxon relative abundance or carriage between the two groups. Genus Candida, previously associated with periodontal disease in culture-based studies, had higher median relative abundance in participants with periodontal disease (33.2%) compared to participants with oral health (2.2%), though the difference was not significant (p = 0.52). Additionally, within the periodontal disease group, median relative abundance of Candida increased with increasing number of permanent teeth lost (1–2 teeth lost: 3.2%; 3–4 teeth lost: 16.6%; ≥5 teeth lost: 73.9%; p = 0.11), though sample size was small for this analysis.

Conclusions

In this first study comprehensively characterizing the oral mycobiome of adults with periodontal disease or good oral health, we observed trends of higher Candida abundance in participants with periodontal disease, and participants with greater tooth loss. Small sample size may have limited the power to detect significant associations. Larger studies including subgingival samples may further establish the core oral mycobiome in health, and relate it to periodontal disease.

Candida-Bacteria Interactions: Their Impact on Human Disease

Candida species are the most common infectious fungal species in humans; out of the approximately 150 known species, Candida albicans is the leading pathogenic species, largely affecting immunocompromised individuals. Apart from its role as the primary etiology for various types of candidiasis, C. albicans is known to contribute to polymicrobial infections. Polymicrobial interactions, particularly between C. albicans and bacterial species, have gained recent interest in which polymicrobial biofilm virulence mechanisms have been studied including adhesion, invasion, quorum sensing, and development of antimicrobial resistance. These trans-kingdom interactions, either synergistic or antagonistic, may help modulate the virulence and pathogenicity of both Candida and bacteria while uniquely impacting the pathogen-host immune response. As antibiotic and antifungal resistance increases, there is a great need to explore the intermicrobial cross-talk with a focus on the treatment of Candida-associated polymicrobial infections. This article explores the current literature on the interactions between Candida and clinically important bacteria and evaluates these interactions in the context of pathogenesis, diagnosis, and disease management.

Etidronate down-regulates Toll-like receptor (TLR) 2 ligand-induced proinflammatory cytokine production by inhibiting NF-κB activation

BACKGROUND

Etidronate is a non-nitrogen-containing bisphosphonate (non-NBP) used for anti-bone resorptive therapy as well as having inhibitory effects on atherosclerotic plaques. The present study examined the effects of etidronate on the production of proinflammatory cytokines and chemokines by the macrophage-like cell line, J774.1, incubated with Pam₃Cys-Ser-(Lys)₄ (Pam₃CSK₄, a Toll-like receptor (TLR) 2 agonist) and lipid A (a TLR4 agonist).

METHODS

J774.1 cells and human monocytic THP-1 cells were pretreated with or without etidronate for 5min, and then incubated with or without Pam₃CSK₄ or lipid A for 24h. Levels of secreted interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-1α (MIP-1α) in culture supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Cytotoxicity was determined by LDH activity in the supernatants. We also examined the effects of etidronate on the activation of nuclear factor-κB (NF-κB) and p38 mitogen-activated protein kinase (MAPK) in J774.1 cells by ELISA and Western blotting.

RESULTS

Treatment of J774.1 cells with etidronate down-regulated TLR2 ligand-induced production of IL-6, TNF-α, MCP-1, and MIP-1α. Etidronate also inhibited Pam₃CSK₄-induced MCP-1 and TNF-α production by THP-1 cells. However, etidronate did not induce cytotoxicity and reduced lipid A-induced cytotoxicity in J774.1 cells. In addition, this agent did not down-regulate TLR4 ligand-induced proinflammatory cytokine production. Furthermore, etidronate inhibited the translocation of NF-κB but not p38 MAPK in J774.1 cells stimulated with Pam₃CSK₄ or lipid A.

CONCLUSION

Etidronate likely inhibits proinflammatory cytokine production in J774.1 cells by suppressing NF-κB activation in the TLR2 and not the TLR4 pathway.

Porphyromonas gingivalis can invade periodontal ligament stem cells

Background

Porphyromonas gingivalis is strongly associated with the development, progression, severity and recurrence of periodontitis. Periodontal ligament stem cells (PDLSCs) play an important role in the maintenance of periodontal tissue self-renewal and repair. The purpose of this study was to investigate the ability of P. gingivalis to infect PDLSCs using an in vitro monolayer model.

Methods

We separated and cultured primary PDLSCs using the tissue block with limiting dilution method. The efficiency of P. gingivalis (ATCC 33277) infection of PDLSCs was measured using agar plate culture and quantitative polymerase chain reaction (q-PCR) methods. PDLSCs infected with P. gingivalis were also observed by transmission electron microscopy.

Results

We assessed stem cell properties including cell morphology, clone formation, growth activity, cell surface antigens and multiple differentiation capacity. The infection rates of P. gingivalis in PDLSC at MOIs of 50, 100, 200, and 500 were 5.83%, 8.12%, 7.77% and 7.53% according to the agar plate culture method. By q-PCR, the efficiencies of P. gingivalis infection of PDLSCs at MOIs of 50, 100, 200, and 500 were 6.74%, 10.56%, 10.36% and 9.78%, respectively. Overall, the infection efficiency based on q-PCR was higher than that according to agar plate culture. Using transmission electron microscopy, we verified that P. gingivalis (ATCC 33277) could infect and invade PDLSCs after 2 h of incubation, and endocytic vacuoles were not found surrounding the internalized bacteria.

Conclusions

In conclusion, our data demonstrate that P. gingivalis can invade PDLSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-0950-5) contains supplementary material, which is available to authorized users.

Prevalence of periodontopathogens and Candida spp. in smokers after nonsurgical periodontal therapy - a pilot study

This pilot study aimed to evaluate the influence of smoking on clinical and microbiological parameters after nonsurgical periodontal therapy. Forty-eight subjects were grouped into smokers (SM, n = 24) and nonsmokers (NS, n = 24) and paired according to gender, age, ethnicity, and periodontal status. Both groups received oral hygiene education and scaling and root planing. Clinical evaluation was performed using plaque index (PI), bleeding on probing (BOP), pocket probing depth (PPD), gingival recession (GR), and clinical attachment level (CAL) before instrumentation (baseline) and at 3 and 6 months. The prevalence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Candida albicans, Candida glabrata, Candida tropicalis, and Candida dubliniensis in subgingival biofilm was determined by polymerase chain reaction. The data were statistically analyzed considering p < 0.05. Clinical conditions improved between baseline and 3 months after periodontal treatment. However, NS had a better clinical response, presenting greater PPD reduction and CAL increase in comparison to SM. Periodontal treatment reduced the levels of P. gingivalis, A. actinomycetemcomitans, and T. forsythia individually after 3 months for the NS group and after 6 months for both groups. The prevalence of Candida species was markedly higher in SM than in NS at all time points evaluated. Periodontopathogens associated or not with C. albicans or C. dubliniensis were more prevalent in SM than in NS at baseline and after 3 months. It was concluded that smoking impairs clinical and microbiological responses to periodontal therapy. Periodontopathogens combined or not with some Candida species are resistant to short-term periodontal therapy in SM.

Innate Immunity and Saliva in Candida albicans-mediated Oral Diseases

The oral cavity is a unique niche where Candida albicans infections occur in immunocompetent as well as immunosuppressed individuals. Here we critically review the significance of human innate immune response in preventing oral candidiasis. One important line of defense against oropharyngeal candidiasis is the oral microbiota that prevents infection by competing for space and nutrients as well as by secreting antagonistic molecules and triggering local inflammatory responses. C. albicans is able to induce mucosal defenses through activation of immune cells and production of cytokines. Also, saliva contains various proteins that affect C. albicans growth positively by promoting mucosal adherence and negatively through immune exclusion and direct fungicidal activity. We further discuss the role of saliva in unifying host innate immune defenses against C. albicans as a communicating medium and how C. albicans overgrowth in the oral cavity may be a result of aberrations ranging from microbial dysbiosis and salivary dysfunction to epithelial damage. Last we underscore select oral diseases in which C. albicans is a contributory microorganism in immune-competent individuals.

Modulation of Candida albicans virulence by bacterial biofilms on titanium surfaces

Whilst Candida albicans occurs in peri-implant biofilms, its role in peri-implantitis remains unclear. This study therefore examined the virulence of C. albicans in mixed-species biofilms on titanium surfaces. Biofilms of C. albicans (Ca), C. albicans with streptococci (Streptococcus sanguinis, S. mutans) (Ca-Ss-Sm) and those incorporating Porphyromonas gingivalis (Ca-Pg and Ca-Ss-Sm-Pg) were developed. Expression of C. albicans genes associated with adhesion (ALS1, ALS3, HWP1) and hydrolytic enzymes (SAP2, SAP4, SAP6, PLD1) was measured and hyphal production by C. albicans quantified. Compared with Ca biofilms, significant (p<0.05) up-regulation of ALS3, HWP1, SAP2 and SAP6, and hyphal production occurred in biofilms containing streptococci (Ca-Ss-Sm). In Ca-Pg biofilms, down-regulation of HWP1 and SAP4 expression, with reduced hyphal production occurred. Ca-Ss-Sm-Pg biofilms had increased hyphal proportions and up-regulation of ALS3, SAP2 and SAP6. In conclusion, C. albicans expressed virulence factors in biofilms that could contribute to peri-implantitis, but this was dependent on associated bacterial species.