Carriage rate and virulence attributes of oral Candida albicans isolates from patients with oral lichen planus: a study in an ethnic Chinese cohort

Oral Mycobiota: A Narrative Review

Numerous studies have proven the important role of the oral microbiota in health and disease. The dysfunctionality of the oral microbiota, known as dysbiosis, is incriminated in dental caries, periodontal disease, oral infectious diseases, oral cancer, and systemic disease. The lesser-known component of the oral microbiota, the mycobiota, is now assiduously investigated. Recent technological developments have helped foster the identification of new fungal species based on genomic research. Next-generation sequencing has expanded our knowledge about the diversity, architecture, and relationships of oral microorganisms within the oral cavity. The mycobiome structure and relationships with the bacteriome have been studied to identify a mycobiotic signature. This review aimed to emphasize the latest knowledge of the oral mycobiome.

Oral Potentially Malignant Disorders and Candida in Oral Tongue Squamous Cell Carcinoma Patients

This retrospective study addressed the role of oral potentially malignant disorders and the presence of intraepithelial Candida hyphae in the carcinogenesis of the oral tongue squamous cell carcinoma and its association with smoking, alcohol consumption, and oral inflammatory burden. The medical records of 183 subjects diagnosed with oral tongue squamous cell carcinoma at the Helsinki University Hospital were investigated. Preceding oral lichen planus, lichenoid reaction, and leukoplakia diagnosis were recorded. Further, the data on Candida hyphae in histological samples as an indicator of oral candidiasis, oral inflammatory burden, smoking, and alcohol consumption were recorded and analyzed. The histopathological diagnosis of oral lichen planus/lichenoid reaction (p < 0.001) and the presence of Candida hyphae (p = 0.005) were associated significantly with female gender. Oral lichen planus/lichenoid reaction patients were less often smokers than patients without these lesions. Candida hyphae were more often recorded in patients without alcohol use (p = 0.012). Oral lichen planus/lichenoid reaction and Candida hyphae in histological samples were associated with female gender and lower levels of typical risk factors, such as alcohol use and smoking, in oral tongue squamous cell carcinoma patients. Therefore, these patients should be well monitored despite a potential lack of the classical risk factors of oral carcinoma.

Clinical Evaluation of Dexamethasone Plus Gentamycin Mouthwash Use in Combination with Total Glucosides of Paeony for Treatment of Oral Lichen Planus without Fungal Infection: A Comparative Study with Long-Term Follow-Up

Background: Oral lichen planus (OLP) is a common chronic inflammatory disease of the oral mucosa and considered a potential malignant disease, for which a method for complete cure is lacking. The dexamethasone and gentamicin mouthwash, combined with total glucosides of paeony (TGP), was tested in the treatment of OLP patients without fungal infection, with a view to provide evidence that may assist in resolving the dilemma. Methods: A randomized and single-blind clinical trial of 48 non-erosive and erosive OLP patients was conducted, with the patients divided into two groups. Group A was treated with dexamethasone plus gentamycin mouthwash and Group B received an additional TGP capsule together with the aforementioned mouthwash. All the patients were followed up with four times, at 2 weeks, 1 month, 3 months, and 6 months. The clinical manifestations, sign score, and VAS scale were recorded. The total effective rate (%) was defined as (cases of complete resolution + cases of partial resolution)/total cases observed × 100%. Results: A total of 43 patients completed all follow-up appointments. Among the 21 patients in Group A, the total effective rate was 61.9%. Of the 22 patients in Group B, the total effective rate was 89.66%. The clinical manifestation, sign score, and VAS of the two groups all indicated improvements, and there were significant differences between the two groups (p < 0.05). Conclusions: Dexamethasone plus gentamycin mouthwash combined with TGP treatment for OLP patients is a safe and effective treatment of OLP.

Factors influencing the presence of Candida dubliniensis and other non-albicans species in patients with oral lichen planus: a retrospective observational study

Objectives

The epidemiologic distribution of non-albicans species in the oral cavity of oral lichen planus (OLP) patients remains uncertain. Therefore, the aim of this study was to identify factors associated with the presence of C. dubliniensis and other non-albicans species. Furthermore, independent risk factors for Candida superinfection in OLP should be identified.

Material and methods

Epidemiologic data and microbiological findings from 268 symptomatic OLP patients who underwent continuous oral swab culture over a 5-year period (2015–2019) were retrospectively reviewed. Candida species identification and semi-quantification were obtained by culture on CHROMagar Candida, followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Results

C. albicans was the most frequently isolated species (72.3%), followed by C. glabrata (7.3%), C. dubliniensis (5.8%), C. krusei and C. parapsilosis (both 2.6%). The presence of C. dubliniensis was significantly associated with tobacco smoking. Other non-albicans spp. were significantly more often detected in patients using removable dentures. Increasing age and the intake of psychotropic drugs were identified as independent risk factors of Candida superinfection in OLP.

Conclusion

In OLP patients, certain local and systemic factors increase the risk of carrying potentially drug-resistant Candida species and the development of Candida superinfection of OLP lesions.

Clinical relevance

Due to the frequent detection of non-albicans species in OLP, resistance or at least reduced sensitivity to azole antifungals should be expected, especially in smokers and patients using removable dentures. In the case of oral complaints, a superinfection with Candida should be considered, whereby older patients and patients taking psychotropic drugs have an increased risk for oral infection with Candida.

A pilot study: a possible implication of Candida as an etiologically endogenous pathogen for oral lichen planus

Background

The aim of this study was to investigate the prevalence and genotypic profiles of Candida albicans in patients with oral lichen planus (OLP).

Materials and methods

Positive rates and genotypic profiles of Candida albicans strains from OLP patients and healthy controls were analyzed. Random amplified polymorphic DNA and internal transcribed spacer of ribosome DNA polymerase chain reactions were used to sequence the DNA of these strains, and then their genetic similarity was measured using BLAST, UIV Band, and Vector NTI Suite Sequence Analyses Software.

Results

The prevalence of C. albicans strains detected from erosive-OLP, non-erosive OLP, and normal individuals was 18.87, 18.75, and 7.92%, respectively. Four different genotypes were revealed by the two methods. To be specific, type I was found only in the healthy subjects; type II a and II b were found in non-erosive OLP, and type III was identified in erosive OLP. Intragroup similarity coefficients, i.e. S_AB were 100%, and inter-groups similarity coefficients, i.e. S_AB were less than 30%.

Conclusions

The genotypic results of C. albicans in OLP revealed an endogenous rather than exogenous infection of C. albicans. In addition, a possible pathogenic role of C. albicans in OLP, with the etiologic sense contributing to a more proper recognition on the pathogenesis, development, and progression of OLP, as well as some strategies for its diagnosis and treatment were identified.

Salivary mycobiome dysbiosis and its potential impact on bacteriome shifts and host immunity in oral lichen planus

The biodiversity of the mycobiome, an important component of the oral microbial community, and the roles of fungal–bacterial and fungal–immune system interactions in the pathogenesis of oral lichen planus (OLP) remain largely uncharacterized. In this study, we sequenced the salivary mycobiome and bacteriome associated with OLP. First, we described the dysbiosis of the microbiome in OLP patients, which exhibits lower levels of fungi and higher levels of bacteria. Significantly higher abundances of the fungi Candida and Aspergillus in patients with reticular OLP and of Alternaria and Sclerotiniaceae_unidentified in patients with erosive OLP were observed compared to the healthy controls. Aspergillus was identified as an “OLP-associated” fungus because of its detection at a higher frequency than in the healthy controls. Second, the co-occurrence patterns of the salivary mycobiome–bacteriome demonstrated negative associations between specific fungal and bacterial taxa identified in the healthy controls, which diminished in the reticular OLP group and even became positive in the erosive OLP group. Moreover, the oral cavities of OLP patients were colonized by dysbiotic oral flora with lower ecological network complexity and decreased fungal–Firmicutes and increased fungal–Bacteroidetes sub-networks. Third, several keystone fungal genera (Bovista, Erysiphe, Psathyrella, etc.) demonstrated significant correlations with clinical scores and IL-17 levels. Thus, we established that fungal dysbiosis is associated with the aggravation of OLP. Fungal dysbiosis could alter the salivary bacteriome or may reflect a direct effect of host immunity, which participates in OLP pathogenesis.

Imbalance in the oral fungal community could lead to the development of oral lichen planus (OLP), a chronic inflammatory disease that affects the mucous membranes in the mouth. The exact cause of OLP is uncertain, which is a major obstacle to therapeutic development. Using salivary samples, a team headed by Xuedong Zhou at Sichuan University in China investigated the composition and diversity of the fungal community in OLP patients and healthy individuals. The authors found that the oral fungal community was less diverse and that there were higher levels of bacteria in OLP patients. The team concluded that fungal community imbalance could affect the bacterial community in the saliva and the host immunity in the mucous membrane, thereby constituting a direct or indirect cause of the development of OLP.

The immunopathogenesis of oral lichen planus-Is there a role for mucosal associated invariant T cells?

Oral lichen planus (OLP) is a chronic, T-cell-mediated, immune condition of unknown cause. OLP may present with painful symptoms requiring treatment, as well as lesions outside the oral cavity. It is likely that what initiates the OLP disease process is a complex interaction of host susceptibility and environmental triggers. While it is possible that OLP represents a true autoimmune condition against an epithelial autoantigen, the mechanisms that lead to this immune dysregulation are still poorly understood. In this review article, we discuss current concepts relating to the immunopathogenesis of OLP, as well as the potential contributory roles the oral microbiota and mucosal-associated invariant T (MAIT) cells.

Microenvironmental regulation of the progression of oral potentially malignant disorders towards malignancy

Oral potentially malignant disorders (OPMD) develop in a complex tissue microenvironment where they grow sustainably, acquiring oral squamous cell carcinoma (OSCC) characteristics. The malignant tumor depends on interactions with the surrounding microenvironment to achieve loco-regional invasion and distant metastases. Unlike abnormal cells, the multiple cell types in the tissue microenvironment are relatively stable at the genomic level and, thus, become therapeutic targets with lower risk of resistance, decreasing the risk of OPMD acquiring cancer characteristics and carcinoma recurrence. However, deciding how to disrupt the OPMD and OSCC microenvironments is itself a daunting challenge, since their microenvironments present opposite capacities, resulting in diverse consequences. Furthermore, recent studies revealed that tumor-associated immune cells also participate in the process of differentiation from OPMD to OSCC, suggesting that reeducating stromal cells may be a new strategy to prevent OPMD from acquiring OSCC characteristics and to treat OSCC. In this review, we discuss the characteristics of the microenvironment of OPMD and OSCC as well as new therapeutic strategies.

Inhibitory effects of oral Actinomyces on the proliferation, virulence and biofilm formation of Candida albicans

OBJECTIVE

The pathogenesis of Candida-associated stomatitis involves the dysfunction of flora antagonistic to Candida. Oral Actinomyces species play an important role in regulating the oral microecological balance. The objective of this study was to investigate the antagonism of three oral Actinomyces against Candida albicans.

DESIGN

Suspensions, culture supernatants and bacterial lysates of Actinomyces viscosus, Actinomyces naeslundii and Actinomyces odontolyticus were investigated for their actions upon C. albicans. In addition to a commercial strain, six clinical strains of C. albicans were also tested. The proliferation of C. albicans was assessed using a liquid co-cultivation assay. The adhesion, acid protease and extracellular phospholipase activity, hyphae growth, and biofilm formation of C. albicans were measured.

RESULTS

The results showed that the suspensions, culture supernatants and cell lysates of 10(8) colony forming units/ml oral Actinomyces significantly inhibited the proliferation of C. albicans (all P<0.001). The culture supernatants exhibited significant antagonistic interactions in terms of adhesion (A. viscosus P<0.001, A. naeslundii P=0.016 and A. odontolyticus P=0.009), acid protease (A. viscosus P=0.035, A. naeslundii P=0.022, A. odontolyticus P<0.001) and phospholipase activities (A. viscosus P=0.011, A. naeslundii P=0.042, A. odontolyticus P=0.021) of Candida, as well as its hyphae growth (A. viscosus P=0.002, A. naeslundii P=0.008, A. odontolyticus P=0.006). Inhibition of C. albicans biofilm formation was also observed.

CONCLUSIONS

This study provides preliminary evidence that oral Actinomyces have inhibitory effects on the proliferation, adhesion, metabolic enzyme activity, hyphae formation and biofilm development of C. albicans.

Prevalence of Candida spp., xerostomia, and hyposalivation in oral lichen planus--a controlled study

OBJECTIVE

To determine the frequency of Candida spp., xerostomia, and salivary flow rate (SFR) in three different groups: patients with OLP (OLP group), patients with oral mucosal lesions other than OLP (non-OLP group), and subjects without oral mucosal lesions (control group).

MATERIAL AND METHODS

Xerostomia as well as SFR was investigated in the three groups. Samples for isolation of Candida spp. were collected from OLP lesions (38 patients), non-OLP lesions (28 patients), and healthy subjects (32 subjects).

RESULTS

There was no statistically significant difference regarding the frequency of xerostomia and hyposalivation among the three groups (P > 0.05). A higher prevalence for colonization by Candida spp. was found in the healthy subject as compared to that of patients with OLP (P = 0.03) and non-OLP (P = 0.02) groups. Low SFR was not a factor for colonization by Candida spp.

CONCLUSIONS

Xerostomia and hyposalivation occur with similar frequency in subjects with and without oral lesions; also, the presence of oral lesions does not increase the susceptibility to colonization by Candida spp. It seems that any study implicating Candida spp. in the malignant transformation of oral lesions should be carried out mostly on a biochemical basis, that is, by testing the capability of Candida spp. to produce carcinogenic enzyme.

Candidiasis and other oral mucosal lesions during and after interferon therapy for HCV-related chronic liver diseases

Background

Oral lichen planus (OLP) is seen frequently in patients with hepatitis C virus (HCV) infection. The aim of this study was to evaluate the occurrence of oral candidiasis, other mucosal lesions, and xerostomia during interferon (IFN) therapy for HCV infection.

Methods

Of 124 patients with HCV-infected liver diseases treated with IFN therapy in our hospital, 14 (mean age 56.00 ± 12.94 years) who attended to receive administration of IFN once a week were identified and examined for Candida infection and other oral lesions and for the measurement of salivary flow. Serological assays also were carried out.

Results

Cultures of Candida from the tongue surfaces were positive in 7 (50.0%) of the 14 patients with HCV infection at least once during IFN therapy. C. albicans was the most common species isolated. The incidence of Candida during treatment with IFN did not increase above that before treatment. Additional oral mucosal lesions were observed in 50.0% (7/14) of patients: OLP in three (21.4%), angular cheilitis in three (21.4%) and recurrent aphthous stomatitis in one (7.1%). OLP occurred in one patient before treatment with IFN, in one during treatment and in one at the end of treatment. 85.7% of the oral lesions were treated with topical steroids. We compared the characteristics of the 7 patients in whom Candida was detected at least once during IFN therapy (group 1) and the 7 patients in whom Candida was not detected during IFN therapy (group 2). The prevalence of oral mucosal lesions (P=0.0075) and incidence of external use of steroids (P=0.0308) in group 1 were significantly higher than in group 2. The average body weight of group 1 decreased significantly compared to group 2 (P=0.0088). Salivary flow decreased in all subjects throughout the course of IFN treatment and returned at 6^th months after the end of treatment. In group 1, the level of albumin at the beginning of the 6^th month of IFN administration was lower than in group 2 (P=0.0550). According to multivariate analysis, one factor, the presence of oral mucosal lesions, was associated with the detection of Candida. The adjusted odds ratio for the factor was 36.00 (95% confidence interval 2.68-1485.94).

Conclusion

We should pay more attention to oral candidiasis as well as other oral mucosal lesions, in patients with weight loss during IFN treatment.

Differential expression of TLR-2 and TLR-4 in the epithelial cells in oral lichen planus

OBJECTIVE

Oral lichen planus (OLP) is a chronic inflammatory condition of the mucosa mediated by a complex signalling network between the keratinocytes and the sub-epithelial lymphocytes. Since OLP occurs in constantly renewing epithelium continuously exposed to commensals, we hypothesised that the epithelial cell microflora interactions may mediate the persistent inflammation. By virtue of their ability to respond to most oral commensal microorganisms, the toll like receptor-2 (TLR-2) and TLR-4 are the most widely investigated receptors in oral diseases. The overall objective of this study was to investigate the role of TLR-2 and TLR-4 in OLP.

DESIGN

Systemically healthy OLP and control subjects were recruited after obtaining the institutional review board approval. Expression of TLR-2 and TLR-4 proteins and transcripts in the tissue epithelium and in the epithelial cells isolated from saliva were determined by immunohistochemistry and quantitative real-time polymerase chain reaction respectively.

RESULTS

The tissue epithelium and the salivary epithelial cells expressed reduced TLR-2 and increased TLR-4 proteins and transcripts in OLP. The salivary epithelial cells from OLP subjects secreted elevated IL-12. However, upon stimulation with bacterial lipopolysaccharide the epithelial cells from OLP exhibited a mixed Th1 (IL-12) and Th2 (IL-4) response. Presence of dexamethasone significantly reduced inflammatory cytokines in the in vitro stimulated cultures of salivary epithelial cells from OLP subjects.

CONCLUSION

Collectively, our data support a critical role for the host-microbial interactions in the OLP pathogenesis. The potential use of exfoliated oral epithelial cells in saliva for functional analysis exponentially increases its value as biological specimen for clinical research.

Evaluation of saliva flow rates, Candida colonization and susceptibility of Candida strains after head and neck radiation

Hyposalivation is a long-term effect in patients receiving head and neck radiation. Radiotherapy can predispose oral colonization by Candida species of the mucosa. This study aims to evaluate the correlation between hyposalivation, measured by unstimulated saliva flow rates (SFR) and fungal colonization of the oral cavity, and also the resistance of isolated Candida strains to antimicrobial therapy. Fifty-three consecutive patients with radiotherapy were examined for late radiation damage on dental hard tissue and the salivary glands (SFR over a period of 5 min). The SFR were divided into three different values of hyposalivation: grade I (SFR 0.1-0.25 ml/min), grade II (SFR ≤0.1 ml/min), and grade III (SFR = 0.0 ml/min). Candidal colonization was defined using Sabouraud agar and identified using API 20C AUX (biomerieux) in the patients' rinsing water. Susceptibility was tested with Etest (amphotericin B, ketoconacole, voriconacole, and fluconacole). Hyposalivation grade I was detected in 23% (9.1 × 10(1) colony forming units (cfu); range, 200-5,900 cfu), hyposalivation grade II in 26% (4.3 × 10(1) cfu; range, 110-3,300 cfu), and hyposalivation grade III in 51% (2.0 × 10(3) cfu; range, 300-19,475 cfu) of patients. A significant correlation between the SFR and candidal colonization and clinical presentation (European Organization for Research and Treatment of Cancer (EORTC) score) was detected (Mann-Whitney test, p = 0.031). Twenty Candida albicans and 27 non-albicans species were identified. The resistance of C. albicans was higher than that of non-albicans strains against antimicrobial agents. By comparison, amphotericin B showed the greatest and fluconazole the least effect. A higher value of hyposalivation correlates with a higher risk of candidal colonization in patients who have received radiotherapy and also with a higher EORTC score. The spectrum of Candida is wide and susceptibility against antifungal therapy differs. In long-term examinations of patients with xerostomia after radiotherapy, the EORTC score can be used to measure hyposalivation. Reduced susceptibility of C. albicans might introduce complications to therapy. Findings of more non-albicans strains show a change in colonization which should be examined in further studies.

Effect of oral care gel on the quality of life for oral lichen planus in patients with chronic HCV infection

BACKGROUND

Oral lichen planus (OLP) decreases the quality of life because it can cause spontaneous pain during eating and tooth-brushing and an uncomfortable feeling in the mouth. In addition, OLP may be associated with HCV-related liver disease.We investigated the visual analogue scale (VAS) and effects of oral care gel, REFRECARE-H®, on patients with OLP associated with HCV infection.

RESULTS

Nine OLP patients (mean age 67.9 ± 7.6 years) with HCV-related liver diseases were recruited and their VAS score determined along with a biochemical examination of the blood. Types of OLP included erosive (6 patients) and reticular (3). REFRECARE-H®, an oral care gel (therapeutic dentifrice) containing hinokitiol, was applied by each patient as a thin layer on the oral membrane, after each meal and at bedtime for 30 days. Application of REFRECARE-H® improved the quality of life in all terms of dry mouth, breath odor, oral freshness, oral pain during rest, oral pain at a mealtimes, taste disorder, loss of appetite, sleep disorder, depressive mood and jitteriness. VAS scores of dry mouth, breath odor, oral freshness, and sleep disorder were significantly increased 30 days after application of REFRECARE-H® (P = 0.01, P = 0.05, P = 0.03, P = 0.04). VAS scores of oral pain at a mealtimes and taste disorder were increased 30 days after application of REFRECARE-H® (P = 0.06). There was an absence of side effects.

CONCLUSIONS

REFRECARE-H® improved the quality of life for OLP. It is necessary for the hepatologist to educate patients regarding oral hygiene, as well as provide treatment of liver disease.