Patterns of human oral yeast species distribution on Hainan Island in China

Hsp90 interaction networks in fungi-tools and techniques

Heat-shock protein 90 (Hsp90) is a central regulator of cellular proteostasis. It stabilizes numerous proteins that are involved in fundamental processes of life, including cell growth, cell-cycle progression and the environmental response. In addition to stabilizing proteins, Hsp90 governs gene expression and controls the release of cryptic genetic variation. Given its central role in evolution and development, it is important to identify proteins and genes that interact with Hsp90. This requires sophisticated genetic and biochemical tools, including extensive mutant collections, suitable epitope tags, proteomics approaches and Hsp90-specific pharmacological inhibitors for chemogenomic screens. These usually only exist in model organisms, such as the yeast Saccharomyces cerevisiae. Yet, the importance of other fungal species, such as Candida albicans and Cryptococcus neoformans, as serious human pathogens accelerated the development of genetic tools to study their virulence and stress response pathways. These tools can also be exploited to map Hsp90 interaction networks. Here, we review tools and techniques for Hsp90 network mapping available in different fungi and provide a summary of existing mapping efforts. Mapping Hsp90 networks in fungal species spanning >500 million years of evolution provides a unique vantage point, allowing tracking of the evolutionary history of eukaryotic Hsp90 networks.

Species Diversity and Antifungal Susceptibilities of Oral Yeasts from Patients with Head and Neck Cancer

Purpose

To investigate the colonization and susceptibility to antifungal drugs of oral yeasts in head and neck cancer patients in Hainan, China.

Methods

Oral mucosa samples from 211 head and neck cancer patients were collected. Oral yeasts were isolated and identified to species by rDNA ITS sequencing. The susceptibilities of all yeasts to amphotericin B, fluconazole, fluorocytosine, itraconazole, and ketoconazole were determined.

Results

Yeasts were isolated from 124 of the 211 oral swabs. The 124 yeast isolates were classified into following 10 species, from the most frequent to the least frequent, Candida albicans (53.2%), Candida tropicalis (22.6%), Candida krusei (6.5%), Kodamaea ohmeri (5.6%), Candida parapsilosis (4.8%), Hanseniaspora opuntiae (2.4%), Candida metapsilosis (1.6%), Pichia terricola (1.6%), Pichia norvegensis (0.8%), and Trichosporon asahii (0.8%). The overall frequencies of resistance among the yeasts to amphotericin B, fluconazole, flucytosine, itraconazole, and ketoconazole were 4.8%, 8.1%, 16.1%, 9.7%, and 9.7%, respectively. One C. albicans strain and one C. tropicalis strain were tolerant/resistant to all five drugs.

Conclusion

Given the high prevalence of oral yeast colonization in head and neck cancer patients and the observed resistance of certain yeast isolates to the five antifungal drugs, our results suggest that rapid identification and susceptibility testing should be implemented before antifungal treatment is applied among patients with head and neck cancer in Hainan.

The impact of the Fungus-Host-Microbiota interplay upon Candida albicans infections: current knowledge and new perspectives

Candida albicans is a major fungal pathogen of humans. It exists as a commensal in the oral cavity, gut or genital tract of most individuals, constrained by the local microbiota, epithelial barriers and immune defences. Their perturbation can lead to fungal outgrowth and the development of mucosal infections such as oropharyngeal or vulvovaginal candidiasis, and patients with compromised immunity are susceptible to life-threatening systemic infections. The importance of the interplay between fungus, host and microbiota in driving the transition from C. albicans commensalism to pathogenicity is widely appreciated. However, the complexity of these interactions, and the significant impact of fungal, host and microbiota variability upon disease severity and outcome, are less well understood. Therefore, we summarise the features of the fungus that promote infection, and how genetic variation between clinical isolates influences pathogenicity. We discuss antifungal immunity, how this differs between mucosae, and how individual variation influences a person's susceptibility to infection. Also, we describe factors that influence the composition of gut, oral and vaginal microbiotas, and how these affect fungal colonisation and antifungal immunity. We argue that a detailed understanding of these variables, which underlie fungal-host-microbiota interactions, will present opportunities for directed antifungal therapies that benefit vulnerable patients.

Oral Fungal Microbiota: To Thrush and Beyond

The oral microbiota is complex, multikingdom, interactive, and involves extensive biofilm formation. While dominated by bacteria, Candida is a frequent member of this microbiota; however, several other potentially pathogenic fungi (among around 100 identified species) appear to reside in some individuals, including Cryptococcus, Aspergillus, and Fusarium. Oral candidiasis may manifest as a variety of disease entities in normal hosts and in the immunocompromised. These include pseudomembranous candidiasis (thrush), hyperplastic or atrophic (denture) candidiasis, linear gingival erythema, median rhomboid glossitis, and angular cheilitis. The purpose of this review is to describe the oral fungal microbiota (ie, oral mycobiota), common mouth diseases caused by its members, predisposing factors and treatment, and the potential for causing disseminated disease like their bacterial counterparts.

Adherence and Cytotoxicity of Candida spp. to HaCaT and A549 cells

Candida species are opportunistic fungal pathogens that cause superficial or invasive infections. Recently, the incidence of infection by non-Candida albicans species, especially Candida glabrata, has increased. In this study, we analyzed the adhesion and cytotoxicity of various Candida spp. that are part of the normal human microbiota. C. albicans adheres well to cell culture plates and to cultured cells. C. glabrata selectively adheres to epithelial cells rather than to cell culture plates. Candida parapsilosis insufficiently adheres to confluent monolayers of human lung epithelial A549 and keratinocyte HaCaT cells. We then analyzed the cytotoxicity of C. albicans and C. glabrata, which adhered well to epithelial cells. C. glabrata has been found to cause more damage to A549 cells than to HaCaT cells, suggesting that resident Candida spp. have distinct cytotoxic effects in different tissues. It is important to clarify the properties of Candida spp. as there is evidence that normal microbiota can cause infections. Our data suggest that it is necessary to use appropriate cell lines for characterizing the adherence and cytotoxicity of Candida spp.

Analyses of the Global Multilocus Genotypes of the Human Pathogenic Yeast Candida tropicalis

Candida tropicalis is a globally distributed human pathogenic yeast, especially prevalent in tropical and sub-tropical regions. Over the last several decades, a large number of studies have been published on the genetic diversity and molecular epidemiology of C. tropicalis from different parts of the world. However, the global pattern of genetic variation remains largely unknown. Here we analyzed the published multilocus sequence data at six loci for 876 isolates from 16 countries representing five continents. Our results showed that 280 of the 2677 (10.5%) analyzed nucleotides were polymorphic, resulting in a mean of 82 (a range of 38–150) genotypes per locus and a total of 633 combined diploid sequence types (DSTs). Among these, 93 combined DSTs were shared by 336 strains, including 10 by strains from different continents. Analysis of Molecular Variance (AMOVA) showed that 89% of the observed genetic variations were found within regional and national populations while < 10% was due to among-country separations. Pairwise geographic population analyses showed overall low but statistically significant genetic differentiation between most geographic populations, with the Singaporean and Indian populations being the most distinct from other populations. However, the Mantel test showed no significant correlation between genetic distance and geographic distance among the geographic populations. Consistent with high genetic variation within and limited variations among geographic populations, results from STRUCTURE analyses showed that the 876 isolates could be grouped into 15 genetic clusters, with each cluster having a broad geographic distribution. Together, our results suggest frequent gene flows among certain regional, national, and continental populations of C. tropicalis, resulting in abundant regional and national genetic diversities of this important human fungal pathogen.

Correlation between Chemical Composition and Antifungal Activity of Clausena lansium Essential Oil against Candida spp

Essential oils (EOs) have been shown to have a diversity of beneficial human health effects. Clausena is a large and highly diverse genus of plants with medicinal and cosmetic significance. The aim of this study was to analyze the composition of Clausena lansium EOs and to investigate their potential antifungal effects. The chemical compositions of Clausena lansium EOs obtained by hydrodistillation were analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 101 compounds were identified among the diverse extracts of C. lansium. EOs of leaves and pericarps from different cultivars (Hainan local wampee and chicken heart wampee) collected in Hainan (China) were classified into four clusters based on their compositions. These clusters showed different antifungal activities against five Candida species (C. albicans, C. tropicalis, C. glabrata, C. krusei and C. parapsilosis) using the disc diffusion method. Clausena lansium EOs of pericarps displayed noteworthy antifungal activitives against all the tested Candida strains with inhibition zone diameters in the range of 11.1–23.1 mm. EOs of leaves showed relatively low antifungal activities with inhibition zone diameters in the range of 6.5–22.2 mm. The rank order of antifungal activities among the four EO clusters was as follows: Cluster IV> Cluster III > Cluster I ≥ Cluster II. These results represent the first report about the correlation between chemical composition of C. lansium EOs and antifungal activity. Higher contents of β-phellandrene, β-sesquiphellandrene and β-bisabolene in EOs of pericarps were likely responsible for the high antifungal activity of Cluster IV EOs. Taken together, our results demonstrate the chemical diversity of Clausena lansium EOs and their potential as novel antifungal agents for candidiasis caused by Candida spp. Furthermore, the obtained results showing a wide spectrum of antifungal activities provide scientific evidence for the traditional use of these plants.

Prevalence of Candida Species in Endodontic Infections: Systematic Review and Meta-analysis

INTRODUCTION

Candida in endodontic infections has been investigated in a large number of studies, but its role as an endodontic pathogen is still debatable. The aim of this study was to systematically review the literature on the prevalence of Candida species in root canal infections.

METHODS

Extensive literature research was performed in the most important electronic biomedical databases, and additional studies have been identified from references from relevant articles. Studies were critically appraised using a modified version of the Joanna Briggs Institute Critical Appraisal Checklist.

RESULTS

From 2225 unique records, 2118 were excluded on the basis of title and abstract. Of the remaining 107 studies, 50 were excluded after full-text review, and 57 were included for qualitative and quantitative analysis. The overall prevalence of Candida spp. in root canal infections was 8.20% (95% confidence interval, 5.56%-11.21%). Candida albicans was the most frequently isolated species. Significant heterogeneity among studies was observed (P < .001, I² = 86.07%). Subgroup analyses revealed a higher prevalence of Candida spp. from African samples. All studies considered, a high or unclear risk of bias was prevalent regarding 6 out of the 8 items considered in the critical appraisal.

CONCLUSIONS

Candida spp. occurred in a small proportion of root canal infections. Further and better designed research is needed to investigate the real contribution of Candida spp. to the microbial ecology in infected root canals.

Chemical composition and antifungal activity of Carica papaya Linn. seed essential oil against Candida spp

In recent years, the incidence of clinical yeast infections has increased dramatically. Due to the extensive use of broad-spectrum antifungal agents, there has been a notable increase in drug resistance among infections yeast species. As one of the most popular natural antimicrobial agents, essential oils (EOs) have attracted a lot of attention from the scientific community. The aim of this study was to analyse the chemical composition and examine the antifungal activity of the EO extracted from the seeds of Carica papaya Linn. The papaya seed EO was analysed by gas chromatography-mass spectrometry. The major constituent is benzyl isothiocyanate (99·36%). The filter paper disc diffusion method and broth dilution method were employed. The EO showed inhibitory effect against all the tested Candida strains including C. albicans, C. glabrata, C. krusei, C. parapsilosis and C. tropical with inhibition zone diameters in the range of 14·2-33·2 mm, the minimal inhibitory concentrations (MICs) in the range of 4·0-16·0 μg ml^-1 and the minimum fungicidal concentrations (MFCs) in the range of 16·0-64·0 μg ml^-1 . Here, we found that the papaya seed EO has promising anticandida activity and identify C. papaya L. as a potential natural source of antifungal agents.

SIGNIFICANCE AND IMPACT OF THE STUDY

The chemical composition and antifungal activity of essential oil of Carica papaya seeds were studied. The oil of papaya seeds could inhibit the growth of Candida spp. for the first report. Carica Papaya may be recognized as a possible new source of natural antifungal agents.

Multilocus sequence analyses reveal extensive diversity and multiple origins of fluconazole resistance in Candida tropicalis from tropical China

Candida tropicalis is among the most prevalent human pathogenic yeast species, second only to C. albicans in certain geographic regions such as East Asia and Brazil. However, compared to C. albicans, relatively little is known about the patterns of genetic variation in C. tropicalis. This study analyzed the genetic diversity and relationships among isolates of C. tropicalis from the southern Chinese island of Hainan. A total of 116 isolates were obtained from seven geographic regions located across the Island. For each isolate, a total of 2677 bp from six gene loci were sequenced and 79 (2.96%) polymorphic nucleotide sites were found in our sample. Comparisons with strains reported from other parts of the world identified significant novel diversities in Hainan, including an average of six novel sequences (with a range 1 to 14) per locus and 80 novel diploid sequence types. Most of the genetic variation was found within individual strains and there was abundant evidence for gene flow among the seven geographic locations within Hainan. Interestingly, our analyses identified no significant correlation between the diploid sequence types at the six loci and fluconazole susceptibility, consistent with multiple origins of fluconazole resistance in the Hainan population of C. tropicalis.

Dysbiosis of fungal microbiota in the intestinal mucosa of patients with colorectal adenomas

The fungal microbiota is an important component of the human gut microbiome and may be linked to gastrointestinal disease. In this study, the fungal microbiota of biopsy samples from adenomas and adjacent tissues was characterized by deep sequencing. Ascomycota, Glomeromycota and Basidiomycota were identified as the dominant phyla in both adenomas and adjacent tissues from all subjects. Among the 60 genera identified, the opportunist pathogens Phoma and Candida represented an average of 45% of the fungal microbiota. When analyzed at the operational taxonomic unit (OTU) level, however, a decreased diversity in adenomas was observed, and three OTUs differed significantly from the adjacent tissues. Principal Component Analysis (PCA) revealed that the core OTUs formed separate clusters for advanced and non-advanced adenomas for which the abundance of four OTUs differed significantly. Moreover, the size of adenomas and the disease stage were closely related to changes in the fungal microbiota in subjects with adenomas. This study characterized the fungal microbiota profile of subjects with adenomas and identified potential diagnostic biomarkers closely related to different stages of adenomas.

Prevalent drug resistance among oral yeasts from asymptomatic patients in Hainan, China

The oral cavity is a significant niche of the human microbiome and a gateway for the microbiota in many other human body sites. As a result, understanding the oral microbiota has broad implications for the prevention and management of human infectious diseases. Opportunistic yeast infections are among the most prevalent fungal infections of humans, and most opportunistic yeast pathogens are common residents of the oral mucosa. However, relatively little is known about the drug susceptibility profiles of oral yeasts. Here, we report the species distribution and patterns of antifungal susceptibility profiles among 313 yeasts isolated from the oral cavities of 301 asymptomatic hospitalized patients in Hainan Province in southern China. These yeasts were tested for their susceptibilities to the following five drugs: amphotericin B, fluconazole, itraconazole, ketoconazole, and fluorocytosine. Since none of the sampled hosts had taken any antifungal drugs at least 3 months before samples were taken, we hypothesized that little or no drug resistance should be observed. Contrary to our expectations, our analyses identified that 29 % (91/313) of the isolates were resistant to at least one drug and 14.3 % (45/313) were resistant to two or more of the five common drugs. The potential sources of the observed resistance were discussed.