Epidemiology of oropharyngeal Candida colonization and infection in patients receiving radiation for head and neck cancer

Comparison of Candida colonization in intensive care unit patients with and without COVID-19: First prospective cohort study from Turkey

Candida species are the primary cause of fungal infections in intensive care units (ICUs). Despite the increasing prevalence of Candida-related infections, monitoring the progression of these infections from colonization in COVID-19 ICU patients lacks sufficient information. This study aims prospectively to compare 62 COVID-19 and 60 non-COVID-19 ICU patients from admission to discharge in terms of colonization development, rates, isolated Candida species, risk factors, and Candida infections during hospitalization. A total of 1464 samples were collected at specific time intervals from various body sites [mouth, skin (axilla), rectal, and urine]. All samples were inoculated onto CHROMagar Candida and CHROMagar Candida Plus media, and isolates identified using MALDI-TOF MS. COVID-19 patients exhibited significantly higher colonization rates in oral, rectal, and urine samples compared to non-COVID-19 patients, (p < 0.05). Among the Candida species, non-albicans Candida was more frequently detected in COVID-19 patients, particularly in oral (75.8%-25%; p < 0.001) and rectal regions (74.19% - 46.66%; p < 0.05). Colonization with mixed Candida species was also more prevalent in the oropharyngeal region (p < 0.05). Mechanical ventilation and corticosteroid use emerged as elevated risk factors among COVID-19 patients (p < 0.05). Despite the colonization prevalence, both COVID-19-positive and negative patients exhibited low incidences of Candida infections, with rates of 9.67% (n = 6/62) and 6.67% (n = 3/60), respectively. Consequently, although Candida colonization rates were higher in COVID-19 ICU patients, there was no significant difference in Candida infection development compared to the non-COVID-19 group. However, the elevated rate of non-albicans Candida isolates highlights potential future infections, particularly given their intrinsic resistance in prophylactic or empirical treatments if needed. Additionally, the high rate of mixed colonization emphasizes the importance of using chromogenic media for routine evaluation.

Microbial Analysis of Obturators During Maxillofacial Prosthodontic Treatment Over an 8-Year Period

The aim of the study was to investigate the microbial colonization (by Candida species, anaerobic and facultative anaerobic bacteria) of maxillary obturators used for the restoration of maxillary defects, including during radiotherapy.

Retrospective cohort study.

Fifteen patients requiring a maxillary obturator prosthesis had swabs of their obturators and adjacent tissues taken at different stages of their treatment over a period of 8 years.

Identification of microbial species from the swabs was carried out using randomly amplified polymorphic DNA polymerase chain reaction (RAPD PCR) analysis, checkerboard DNA-DNA hybridization, CHROMagar Candida chromogenic agar, and DNA sequencing.

Candida species were detected in all patients and all patients developed mucositis and candidiasis during radiotherapy which was associated with an increase in colonization of surfaces with Candida spp., particularly C albicans. Microbial colonization increased during radiotherapy and as an obturator aged, and decreased following a reline, delivery of a new prosthesis, or antifungal treatment during radiotherapy.

Microbial colonization of maxillary obturators was related to the stage of treatment, age of the obturator material, radiotherapy and antifungal medications, and antifungal treatment may be recommended if C albicans colonization of palatal tissues is greater than 105 colony-forming units per cm2 following the first week of radiotherapy.

Coexpression network analysis of human candida infection reveals key modules and hub genes responsible for host-pathogen interactions

Invasive fungal infections are a significant reason for morbidity and mortality among organ transplant recipients. Therefore, it is critical to investigate the host and candida niches to understand the epidemiology of fungal infections in transplantation. Candida albicans is an opportunistic fungal pathogen that causes fatal invasive mucosal infections, particularly in solid organ transplant patients. Therefore, identifying and characterizing these genes would play a vital role in understanding the complex regulation of host-pathogen interactions. Using 32 RNA-sequencing samples of human cells infected with C. albicans, we developed WGCNA coexpression networks and performed DESeq2 differential gene expression analysis to identify the genes that positively correlate with human candida infection. Using hierarchical clustering, we identified 5 distinct modules. We studied the inter- and intramodular gene network properties in the context of sample status traits and identified the highly enriched genes in the correlated modules. We identified 52 genes that were common in the most significant WGCNA turquoise module and differentially expressed genes in human endothelial cells (HUVEC) infection vs. control samples. As a validation step, we identified the differentially expressed genes from the independent Candida-infected human oral keratinocytes (OKF6) samples and validated 30 of the 52 common genes. We then performed the functional enrichment analysis using KEGG and GO. Finally, we performed protein-protein interaction (PPI) analysis using STRING and CytoHubba from 30 validated genes. We identified 8 hub genes (JUN, ATF3, VEGFA, SLC2A1, HK2, PTGS2, PFKFB3, and KLF6) that were enriched in response to hypoxia, angiogenesis, vasculogenesis, hypoxia-induced signaling, cancer, diabetes, and transplant-related disease pathways. The discovery of genes and functional pathways related to the immune system and gene coexpression and differential gene expression analyses may serve as novel diagnostic markers and potential therapeutic targets.

Evaluation of Candidiasis in Upper-Aerodigestive Squamous Cell Carcinoma Patients—A Clinico-Mycological Aspect

Candida is a commensal yeast. It can be infective when the host’s defense mechanism is weakened, as in the case of squamous cell carcinoma patients. We aimed to evaluate the prevalence and clinical mycological manifestation of candidiasis in 150 cancer cases comprised of preoperative and post-operative (with or without radiotherapy) upper aerodigestive squamous cell carcinoma. A total of 150 patients suffering from squamous cell carcinoma of the Upper Aero-Digestive Tract (UADT) were divided into preoperative (n = 48), post-operative without radiotherapy (n = 29) and post-operative with radiotherapy (n = 73). Samples were collected using cotton swabs and cultured. Candida species were identified according to color pigmentation on Candida Differential Agar (CDA) plate. The clinico-mycological association of patients was evaluated by the chi-square test, and 98 out of 150 patients showed the presence of various Candida species. The major species isolated was Candida albicans (53%), followed by Candida tropicalis (16%). There was a significant statistical difference between patients who showed mycological associations and patients who did not have any such association (p = 0.0008). The prevalence of oral candidiasis was found to be 65.33% among total cases of upper aero-digestive squamous cell carcinoma. Chronic erythematous cases of candidiasis were mainly seen in preoperative squamous cell carcinoma cases, whereas the acute erythematous type of candidiasis was mainly seen in post-operative cases who received radiotherapy. The clinicomycological assessment can help to correlate the signs and symptoms with the presence of candidiasis in upper aerodigestive squamous cell carcinoma patients. Meticulous testing and examination can help in the early detection of candidiasis. Future studies are needed to develop advance scientific preventive strategies for high-risk cases.

Biofilm formation of Candida isolates from xerostomic post-radiotherapy head and neck cancer patients

Oral candidiasis is a common problem in post-radiation head and neck cancer (HNC) patients. While biofilm formation is a crucial virulence factor for Candida colonization, existing information on biofilm formation capability of Candida in cancer patients is scarce.

OBJECTIVE

To evaluate biofilm formation capability of Candida spp. colonized in xerostomic post-radiotherapy HNC patients.

DESIGN

Candida albicans and non-albicans Candida species were previously isolated from xerostomic post-radiation cancer patients and healthy individuals. Biofilm mass and biofilm metabolic activity were investigated by crystal violet and MTT assays, respectively. Their relationship with clinical parameters was analyzed using Mann-Whitney U and Chi-square tests.

RESULTS

A total of 109 and 45 Candida isolates from 64 cancer patients and 34 controls, respectively, were evaluated. Both biofilm mass and metabolic activity of Candida isolates from cancer patients were higher than those from controls. The between-group differences were statistically significant in C. albicans (p < 0.001) for biofilm mass, and in C. tropicalis (p = 0.01) for biofilm metabolic activity. Overall, C. tropicalis was the best biofilm producers in both groups. Additionally, we found that higher biofilm formation among C. albicans was associated with low saliva buffering capacity.

CONCLUSIONS

C. albicans and C. tropicalis isolated from xerostomic post-radiation cancer patients had higher biofilm formation capability than those from healthy individuals. Our findings suggest that, in addition to compromised host factors, higher biofilm formation capability may also contribute to the pathogenesis of oral candidiasis in HNC patients. This novel information potentially adds to proper management for these patients.

Metabolic profile of Candida albicans and Candida parapsilosis interactions within dual-species biofilms

Within the oral cavity, the ability of Candida species to adhere and form biofilms is well recognized, especially when C. albicans is considered. Lately, a knowledge gap has been identified regarding dual-species communication of Candida isolates, as a way to increase virulence, with evidences being collected to support the existence of interactions between C. albicans and C. parapsilosis. The present work evaluated the synergistic effect of the two Candida species, and explored chemical interactions between cells, evaluating secreted extracellular alcohols and their relation with yeasts´ growth and matrix composition. Four clinical strains of C. albicans and C. parapsilosis species, isolated from single infections of different patients or from co-infections of a same patient, were tested. It was found that dual-species biofilms negatively impacted the growth of C. parapsilosis and their biofilm matrix, in comparison with mono-species biofilms, and had minor effects on the biofilm biomass. Alcohol secretion revealed to be species- and strain-dependent. However, some dual-species cultures produced much higher amounts of some alcohols (E-nerolidol and E, E-Farnesol) than the respective single cultures, which proves the existence of a synergy between species. These results show evidence that interactions between Candida species affect the biofilm matrix, which is a key element of oral biofilms.

An underestimated pitfall of oral candidiasis in head and neck cancer patients undergoing radiotherapy: an observation study

Background

Oral candidiasis is a common problem associated with head and neck radiation therapy (RT) consequences being pain, burning sensation, taste change, and systemic infection. There are difficulties in differentiating between oral candidiasis and radiation induced oral mucositis. We conducted a prospective study to explore the incidence of clinical oral candidiasis and evaluate the accuracy of diagnosis among head and neck cancer (HNC) patients receiving RT or concurrent chemoradiotherapy (CCRT).

Methods

This study included 86 HNC patients who had no clinical signs or symptoms of oral candidiasis. Oral mucosa and tongue swabs were carried out and analyzed three times by fungal cultures at the following time points: (1) before RT, (2) at the time of clinically diagnosed candidiasis or during RT at between the 15th–17th fraction (whichever occurred first), and (3) at the end of RT. The accuracy of clinical oral candidiasis was explored and confirmed by fungal colonization techniques. The incidence and risk factors associated with fungal colonization before and throughout the treatment were analyzed.

Results

The overall incidence of clinical oral candidiasis was 53.5% throughout the course of RT. Confirmation of fungal colonization was found in 39.5%, 65.9%, and 57.7% of cases before RT, during RT, and end of RT, respectively. The accuracy of the diagnosis using only clinical presentation was demonstrated in 60%, 50%, and 52% before RT, during RT, and end of RT, respectively. Logistic regression analysis showed that age, CCRT, and using 2% viscous lidocaine solution were independent risk factors for fungal colonization.

Conclusions

The results of this study demonstrated an underestimation of clinical oral candidiasis before and throughout the course of radiotherapy from using only clinical sign and symptoms. Crucial attention to detail and testing in the oral examination could improve decision making for detection of oral candidiasis in HNC patients receiving RT or CCRT.

Molecular and genetic basis of azole antifungal resistance in the opportunistic pathogenic fungus Candida albicans

Candida albicans is an opportunistic yeast and the major human fungal pathogen in the USA, as well as in many other regions of the world. Infections with C. albicans can range from superficial mucosal and dermatological infections to life-threatening infections of the bloodstream and vital organs. The azole antifungals remain an important mainstay treatment of candidiasis and therefore the investigation and understanding of the evolution, frequency and mechanisms of azole resistance are vital to improving treatment strategies against this organism. Here the organism C. albicans and the genetic changes and molecular bases underlying the currently known resistance mechanisms to the azole antifungal class are reviewed, including up-regulated expression of efflux pumps, changes in the expression and amino acid composition of the azole target Erg11 and alterations to the organism's typical sterol biosynthesis pathways. Additionally, we update what is known about activating mutations in the zinc cluster transcription factor (ZCF) genes regulating many of these resistance mechanisms and review azole import as a potential contributor to azole resistance. Lastly, investigations of azole tolerance in C. albicans and its implicated clinical significance are reviewed.

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.

[Optimization of variables in photodynamic antifungal assays against Candida species]

Oral infections due to yeasts of the genus Candida are very common in patients with predisposing factors, such as physiological conditions or certain underlying diseases. Moreover, oral candidiasis can also evolve into disseminated forms. In this work, strains of the genus Candida were studied to establish the optimal radiation conditions for photosensitizing compounds, in a photodynamic antifungal therapy protocol. A total of 39 isolates were evaluated. The strains were exposed to twelve dyestuffs, eight radiation sources and three different exposure times. Orthotoluidine blue exhibited good photodynamic activity, in combination with exposure to a 20W reflector lamp LED (light-emitting diode) light for 60minutes. When considering the difficulties of using conventional antifungal drugs, the emergence of resistant strains, recurrences, and adverse reactions of certain commonly used drugs, the photodynamic antifungal therapy is a promising strategy for the treatment of localized infections.

Alteration in Oral Flora and Effect of Mucositis in Head and Neck Cancer Patients Undergoing Chemo-radiotherapy

The main aim of this study is to determine the various types of oral bacteria and yeast. Present in oral flora of head and neck cancer patients at different stages of chemo-radiotherapy, and compare it with the control group (patients with contralateral healthy mucosa). Seventy seven patients with proven history of squamous cell carcinoma were included in the study. The oral mucosa profile was assessed for bacterial manifestations in swab samples from both the sites of the patients. The grade of mucositis was charted out for all patients during the second and third week of radiotherapy. The study revealed that all isolated oral flora showed a non-significant increase during radiotherapy, while there was a decrease in oral flora in post RT. However, E. faecalis showed a non- significant decrease during RT, while Citrobacter showed an increase. Candida albicans showed 83% non- significant decrease post- radiotherapy. When these floras were correlated with grade of mucositis, an insignificant increase in flora was found in G2 and G3 stage of mucositis. In this study, the effect of radiation was evaluated on oral flora of head and neck cancer patients and compared with contralateral healthy mucosa of the patients. Various changes were observed during and after radiation therapy. In patients with head and neck cancer the normal oral flora are replaced by pathogenic flora during radiotherapy, and the latter is responsible for infections in post- radiation phase.

Late Oral Complications Caused by Head and Neck Radiotherapy: Clinical and Laboratory Study

Objectives

The aim of presented cross-sectional and observational study was to determine the prevalence of late oral complications of patients with head and neck cancer who underwent radiotherapy, by clinical and laboratory analyses.

Material and Methods

Fifty-five patients, 43 (78.2%) men and 12 (21.8%) women, mean age 60; range 38 to 87 years, who have completed radiotherapy for head and neck cancer for at least 6 months were enrolled. The presence of xerostomia, hyposalivation, oral candidiasis, and type of oral yeasts were correlated with post-radiotherapy period. A control group, age and gender matched, was used for comparisons. The Pearson’s Chi-square or Fischer’s exact test was used at a significance level of 5%.

Results

The mean post-radiotherapy period was 32 months. The oral complications found were xerostomia (45/55, [81.8%]), hyposalivation (44/55 [80%]) and oral candidiasis (15/55 [27.2%]). Xerostomia and hyposalivation was statistically higher in the study group when compared to the control group (P < 0.05). The presence of yeast occurred in 39 (70.9%) of the patients in the study group, and Candida albicans was the most prevalent etiological agent in 25 (64.1%) of those patients (P < 0.05).

Conclusions

Xerostomia and hyposalivation were the more prevalent late oral complications related to radiotherapy. Oral candidiasis was also observed, although its prevalence was lower. The need for long-term dental follow-up of patients who underwent radiotherapy of the head and neck cancer is mandatory.

Suppressive effects of 2-methacryloyloxyethyl phosphorylcholine (MPC)-polymer on the adherence of Candida species and MRSA to acrylic denture resin

Objectives

The effects of 2-methacryloyloxyethyl phosphorylcholine (MPC)-polymer on the adherence of microorganisms such as non-Candida albicans Candida (NCAC) and methicillin-resistant Staphylococcus aureus (MRSA), frequently detected in oral infections in immunocompromised and/or elderly people, to denture resin material, are still unclear. Here, we report the effects of MPC-polymer on the adherence of C. albicans, NCAC, and MRSA to acrylic denture resin.

Methods

Sixteen strains of C. albicans, seven strains of C. glabrata, two strains of C. tropicalis, one strain of C. parapsilosis, and six strains of MRSA were used. We cultured the fungal/bacterial strains and examined the cell growth and adherence of fungi/bacteria to mucin-coated acrylic denture resin plates (ADRP) with or without MPC-polymer coating, by scanning electron microscopy. The cell surface hydrophobicity of the fungal/bacterial strains was measured by the adsorption to hydrocarbons.

Results

MPC-polymer did not affect the growth of all strains of Candida species and MRSA, but significantly suppressed adherence to ADRP in most strains of C. albicans and all strains of NCAC and MRSA. A significant positive correlation was found between cell hydrophobicity and the reduction rates of microbial adherence to ADRP treated with 5% of MPC-polymer.

Conclusions

MPC-polymer treatment for acrylic resin material suppresses the adherence of C. albicans, NCAC and MRSA via their hydrophilicity interaction.

Clinical significance

The application of MPC-polymer for denture hygiene is potent to prevent oral candidiasis, denture stomatitis and opportunistic infection, caused by Candida species and MRSA, via suppressing the adherence of those fungus/bacteria.

Applying the Host-Microbe Damage Response Framework to Candida Pathogenesis: Current and Prospective Strategies to Reduce Damage

Disease is a complex outcome that can occur as a result of pathogen-mediated damage, host-mediated damage or both. This has led to the revolutionary concept of the damage response framework (DRF) that defines microbial virulence as a function of host immunity. The DRF outlines six scenarios (classes) of host damage or beneficial outcomes, depending on the microbe and the strength of the immune response. Candida albicans is uniquely adapted to its human host and can exist as either a commensal, colonizing various anatomical sites without causing notable damage, or as a pathogen, with the ability to cause a diverse array of diseases, ranging from mucosal to invasive systemic infections that result in varying levels of microbe-mediated and/or host-mediated damage. We recently categorized six different forms of candidiasis (oropharyngeal, hematogenous, intra-abdominal, gastrointestinal, denture stomatitis, and vulvovaginitis) into independent DRF classes, supporting a contemporary view of unique mechanisms of pathogenesis for these Candida infections. In this review, we summarize the evidence for the pathogenesis of these various forms of candidiasis in the context of the DRF with the further intent to provide insights into strategies to achieve a level of host response or outcome otherwise, that limits host damage.

Dimethylaminododecyl methacrylate inhibits Candida albicans and oropharyngeal candidiasis in a pH-dependent manner

The prevalence of stomatitis, especially that caused by Candida albicans, has highlighted the need for new antifungal agents. We previously found that a type of quaternary ammonium salts, dimethylaminododecyl methacrylate (DMADDM), incorporated in dental materials inhibited the growth and hyphal development of C. albicans. However, how the quaternary ammonium salts inhibited the fungal pathogens and whether the oral condition, such as salivary pH variation under different diseases, can affect the antimicrobial capacity of quaternary ammonium salts is unknown. This study evaluated the antifungal effects of DMADDM at different pH in vitro and in vivo. A pH-dependent antifungal effect of DMADDM was observed in planktonic and biofilm growth. DMADDM enhanced antifungal activity at alkaline pH. Two pH-regulated genes (PHR1/PHR2) of C. albicans were correlated with the pH-dependent antifungal effects of DMADDM. The PHR1/PHR2 genes and pH values regulated the zeta potential of C. albicans, which then influenced the binding between C. albicans cells and DMADDM. The pH-dependent antifungal activity of DMADDM was then substantiated in a murine oropharyngeal candidiasis model. We directly demonstrated that the antifungal abilities of quaternary ammonium salts relied on the cell zeta potential which affected the binding between fungal cells and quaternary ammonium salts. These findings suggest a new antifungal mechanism of quaternary ammonium under different pH and that DMADDM can be a potential antifungal agent applied in dental materials and stomatitis therapy.Key Points • DMADDM has stronger antifungal activity in alkaline than in acidic pH conditions. • The pH values and pH-regulated genes can affect the zeta potential of fungal cells. • Zeta potential of fungal cells directly affect the binding between DMADDM and cells. Graphical abstract Schematic diagram of the antifungal activities of DMADDM at different pH values.

Vulvovaginal Candidiasis: A Current Understanding and Burning Questions

Candida albicans, along with other closely related Candida species, are the primary causative agents of vulvovaginal candidiasis (VVC)-a multifactorial infectious disease of the lower female reproductive tract resulting in pathologic inflammation. Unlike other forms of candidiasis, VVC is a disease of immunocompetent and otherwise healthy women, most predominant during their child-bearing years. While VVC is non-lethal, its high global incidence and profound negative impact on quality-of-life necessitates further understanding of the host and fungal factors that drive disease pathogenesis. In this review, we cover the current state of our understanding of the epidemiology, host response, fungal pathogenicity mechanisms, impact of the microbiome, and novel approaches to treatment of this most prevalent human candidal infection. We also offer insight into the latest advancements in the VVC field and identify important questions that still remain.

Oral Candidiasis: A Disease of Opportunity

Oral candidiasis, commonly referred to as “thrush,” is an opportunistic fungal infection that commonly affects the oral mucosa. The main causative agent, Candida albicans, is a highly versatile commensal organism that is well adapted to its human host; however, changes in the host microenvironment can promote the transition from one of commensalism to pathogen. This transition is heavily reliant on an impressive repertoire of virulence factors, most notably cell surface adhesins, proteolytic enzymes, morphologic switching, and the development of drug resistance. In the oral cavity, the co-adhesion of C. albicans with bacteria is crucial for its persistence, and a wide range of synergistic interactions with various oral species were described to enhance colonization in the host. As a frequent colonizer of the oral mucosa, the host immune response in the oral cavity is oriented toward a more tolerogenic state and, therefore, local innate immune defenses play a central role in maintaining Candida in its commensal state. Specifically, in addition to preventing Candida adherence to epithelial cells, saliva is enriched with anti-candidal peptides, considered to be part of the host innate immunity. The T helper 17 (Th17)-type adaptive immune response is mainly involved in mucosal host defenses, controlling initial growth of Candida and inhibiting subsequent tissue invasion. Animal models, most notably the mouse model of oropharyngeal candidiasis and the rat model of denture stomatitis, are instrumental in our understanding of Candida virulence factors and the factors leading to host susceptibility to infections. Given the continuing rise in development of resistance to the limited number of traditional antifungal agents, novel therapeutic strategies are directed toward identifying bioactive compounds that target pathogenic mechanisms to prevent C. albicans transition from harmless commensal to pathogen.

Microbial Interactions in Oral Communities Mediate Emergent Biofilm Properties

Oral microbial communities are extraordinarily complex in taxonomic composition and comprise interdependent biological systems. The bacteria, archaea, fungi, and viruses that thrive within these communities engage in extensive cell-cell interactions, which are both beneficial and antagonistic. Direct physical interactions among individual cells mediate large-scale architectural biofilm arrangements and provide spatial proximity for chemical communication and metabolic cooperation. In this review, we summarize recent work in identifying specific molecular components that mediate cell-cell interactions and describe metabolic interactions, such as cross-feeding and exchange of electron acceptors and small molecules, that modify the growth and virulence of individual species. We argue, however, that although pairwise interaction models have provided useful information, complex community-like systems are needed to study the properties of oral communities. The networks of multiple synergistic and antagonistic interactions within oral biofilms give rise to the emergent properties of persistence, stability, and long-range spatial structure, with these properties mediating the dysbiotic transitions from health to oral diseases. A better understanding of the fundamental properties of interspecies networks will lead to the development of effective strategies to manipulate oral communities.

Emerging Complexity and the Need for Advanced Drug Delivery in Targeting Candida Species

Background:

Candida species are the important etiologic agents for candidiasis, the most prevalent cause of opportunistic fungal infections. Candida invasion results in mucosal to systemic infections through immune dysfunction and helps in further invasion and proliferation at several sites in the host. The host defence system utilizes a wide array of the cells, proteins and chemical signals that are distributed in blood and tissues which further constitute the innate and adaptive immune system. The lack of antifungal agents and their limited therapeutic effects have led to high mortality and morbidity related to such infections.

Methods:

The necessary information collated on this review has been gathered from various literature published from 1995 to 2019.

Results:

This article sheds light on novel drug delivery approaches to target the immunological axis for several Candida species (C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, C. krusei, C. rugose, C. hemulonii, etc.).

Conclusion:

It is clear that the novel drug delivery approaches include vaccines, adoptive transfer of primed immune cells, recombinant cytokines, therapeutic antibodies, and nanoparticles, which have immunomodulatory effects. Such advancements in targeting various underpinning mechanisms using the concept of novel drug delivery will provide a new dimension to the fungal infection clinic particularly due to Candida species with improved patient compliance and lesser side effects. This advancement in knowledge can also be extended to target various other similar microbial species and infections.

The association between oral candidiasis and severity of chemoradiotherapy-induced dysphagia in head and neck cancer patients: A retrospective cohort study

•

Oral candidiasis (OC) aggravated dysphagia in chemoradiation for HNC.

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OC patients required higher doses of opioids.

•

Early diagnosis of chemoradiation-associated OC seems difficult.

•

Antifungal prophylaxis may reduce the severity of mucositis and dysphagia.

Background and purpose

Concurrent chemoradiotherapy (CCRT) for head and neck cancer (HNC) is a risk factor for oral candidiasis (OC). As Candida spp. are highly virulent, we conducted a retrospective study to determine whether OC increases the severity of dysphagia related to mucositis in HNC patients.

Patients and methods

We retrospectively analyzed the cases of consecutive patients with carcinomas of the oral cavity, pharynx, and larynx who underwent CCRT containing cisplatin (CDDP) at our hospital. The diagnosis of OC was based on gross mucosal appearance. We performed a multivariate analysis to determine whether OC was associated with the development of grade 3 dysphagia in the Radiation Therapy Oncology Group (RTOG) Acute Toxicity Criteria. The maximum of the daily opioid doses was compared between the patients with and without OC.

Results

We identified 138 HNC patients. OC was observed in 51 patients (37%). By the time of their OC diagnosis, 19 (37%) had already developed grade 3 dysphagia. Among the 30 patients receiving antifungal therapy, 12 (40%) showed clinical deterioration. In the multivariate analysis, OC was independently associated with grade 3 dysphagia (OR 2.75; 95%CI 1.22–6.23; p = 0.015). The patients with OC required significantly higher morphine-equivalent doses of opioids (45 vs. 30 mg/day; p = 0.029).

Conclusion

Candida infection causes refractory dysphagia. It is worth investigating whether antifungal prophylaxis reduces severe dysphagia related to candidiasis.

Regulatory mechanisms controlling morphology and pathogenesis in Candida albicans

Candida albicans, a major human fungal pathogen, can cause a wide variety of both mucosal and systemic infections, particularly in immunocompromised individuals. Multiple lines of evidence suggest a strong association between virulence and the ability of C. albicans to undergo a reversible morphological transition from yeast to filamentous cells in response to host environmental cues. Most previous studies on mechanisms important for controlling the C. albicans morphological transition have focused on signaling pathways and sequence-specific transcription factors. However, in recent years a variety of novel mechanisms have been reported, including those involving global transcriptional regulation and translational control. A large-scale functional genomics screen has also revealed new roles in filamentation for certain key biosynthesis pathways. This review article will highlight several of these exciting recent discoveries and discuss how they are relevant to the development of novel antifungal strategies. Ultimately, components of mechanisms that control C. albicans morphogenesis and pathogenicity could potentially serve as viable antifungal targets.

Contribution of Clinically Derived Mutations in the Gene Encoding the Zinc Cluster Transcription Factor Mrr2 to Fluconazole Antifungal Resistance and CDR1 Expression in Candida albicans

Mutations in genes encoding zinc cluster transcription factors (ZCFs) such as TAC1, MRR1, and UPC2 play a key role in Candida albicans azole antifungal resistance. Artificial activation of the ZCF Mrr2 has shown increased expression of the gene encoding the Cdr1 efflux pump and resistance to fluconazole. Amino acid substitutions in Mrr2 have recently been reported to contribute to fluconazole resistance in clinical isolates. In the present study, 57 C. albicans clinical isolates with elevated fluconazole MICs were examined for mutations in MRR2 and expression of CDR1 Mutations in MRR2 resulting in 15 amino acid substitutions were uniquely identified among resistant isolates, including 4 substitutions (S466L, A468G, S469T, T470N) previously reported to reduce fluconazole susceptibility. Three additional, novel amino acid substitutions (R45Q, A459T, V486M) were also discovered in fluconazole-resistant isolates. When introduced into a fluconazole-susceptible background, no change in fluconazole MIC or CDR1 expression was observed for any of the mutations found in this collection. However, introduction of an allele leading to artificial activation of Mrr2 increased resistance to fluconazole as well as CDR1 expression. Moreover, Mrr2 amino acid changes reported previously to have the strongest effect on fluconazole susceptibility and CDR1 expression also exhibited no differences in fluconazole susceptibility or CDR1 expression relative to the parent strain. While all known fluconazole resistance mechanisms are represented within this collection of clinical isolates and contribute to fluconazole resistance to different extents, mutations in MRR2 do not appear to alter CDR1 expression or contribute to resistance in any of these isolates.

Candida glabrata Has No Enhancing Role in the Pathogenesis of Candida-Associated Denture Stomatitis in a Rat Model

Many denture wearers suffer from Candida-associated denture stomatitis (DS), a fungal infection of the hard palate in contact with dentures. Biofilm formation by Candida albicans on denture/palate surfaces is considered a central process in the infection onset. Although Candida glabrata is frequently coisolated with C. albicans, its role in DS pathogenesis is unknown. We show here, using a contemporary rat model that employed a patented intraoral denture system, that C. glabrata established stable colonization on the denture/palate. However, in contrast to C. albicans inoculated rats, rats inoculated with C. glabrata exhibited minimal changes in weight gain or palatal tissue damage. Likewise, coinoculation with the two Candida species resulted in no exacerbation of C. albicans-induced DS pathology. Together, our findings indicate that C. glabrata has no inducing/enhancing role in DS pathogenesis.

Denture stomatitis (DS) is a condition characterized by inflammation of the oral mucosa in direct contact with dentures and affects a significant number of otherwise healthy denture wearers. Candida-associated DS is predominantly caused by Candida albicans, a dimorphic fungus that readily colonizes and forms biofilms on denture materials. Previous studies showed a requirement for Candida biofilm formation on both palate and dentures in infection and identified fungal morphogenic transcription factors, Efg1 and Bcr1, as key players in DS pathogenesis. While both C. albicans and Candida glabrata are frequently coisolated in mucosal candidiasis, a pathogenic role for C. glabrata in DS remains unknown. Using an established rat model of DS, we sought to determine whether C. glabrata alone or coinoculation with C. albicans establishes colonization and causes palatal tissue damage and inflammation. Rats fitted with custom dentures were inoculated with C. albicans and/or C. glabrata and monitored over a 4-week period for fungal burden (denture/palate), changes in body weight, and tissue damage via lactate dehydrogenase (LDH) release as well as palatal staining by hematoxylin and eosin (H&E) and immunohistochemistry for myeloperoxidase (MPO) as measures of inflammation. C. glabrata colonized the denture/palate similarly to C. albicans. In contrast to C. albicans, colonization by C. glabrata resulted in minimal changes in body weight, palatal LDH release, and MPO expression. Coinoculation with both species had no obvious modulation of C. albicans-mediated pathogenic effects. These data suggest that C. glabrata readily establishes colonization on denture and palate but has no apparent role for inducing/enhancing C. albicans pathogenesis in DS.

IMPORTANCE Many denture wearers suffer from Candida-associated denture stomatitis (DS), a fungal infection of the hard palate in contact with dentures. Biofilm formation by Candida albicans on denture/palate surfaces is considered a central process in the infection onset. Although Candida glabrata is frequently coisolated with C. albicans, its role in DS pathogenesis is unknown. We show here, using a contemporary rat model that employed a patented intraoral denture system, that C. glabrata established stable colonization on the denture/palate. However, in contrast to C. albicans inoculated rats, rats inoculated with C. glabrata exhibited minimal changes in weight gain or palatal tissue damage. Likewise, coinoculation with the two Candida species resulted in no exacerbation of C. albicans-induced DS pathology. Together, our findings indicate that C. glabrata has no inducing/enhancing role in DS pathogenesis.

Chemotherapy-induced oral mucositis and associated infections in a novel organotypic model

Oral mucositis is a common side effect of cancer chemotherapy, with significant adverse impact on the delivery of anti-neoplastic treatment. There is a lack of consensus regarding the role of oral commensal microorganisms in the initiation or progression of mucositis because relevant experimental models are non-existent. The goal of this study was to develop an in vitro mucosal injury model that mimics chemotherapy-induced mucositis, where the effect of oral commensals can be studied. A novel organotypic model of chemotherapy-induced mucositis was developed based on a human oral epithelial cell line and a fibroblast-embedded collagen matrix. Treatment of organotypic constructs with 5-fluorouracil (5-FU) reproduced major histopathologic characteristics of oral mucositis, such as DNA synthesis inhibition, apoptosis and cytoplasmic vacuolation, without compromising the three-dimensional structure of the multilayer organotypic mucosa. Although structural integrity of the model was preserved, 5-FU treatment resulted in a widening of epithelial intercellular spaces, characterized by E-cadherin dissolution from adherens junctions. In a neutrophil transmigration assay we discovered that this treatment facilitated transport of neutrophils through epithelial layers. Moreover, 5-FU treatment stimulated key proinflammatory cytokines that are associated with the pathogenesis of oral mucositis. 5-FU treatment of mucosal constructs did not significantly affect fungal or bacterial biofilm growth under the conditions tested in this study; however, it exacerbated the inflammatory response to certain bacterial and fungal commensals. These findings suggest that commensals may play a role in the pathogenesis of oral mucositis by amplifying the proinflammatory signals to mucosa that is injured by cytotoxic chemotherapy.

A study of changes in the oral fungal flora of patients on radiotherapy for head and neck malignancies and their correlation with funguria and fungemia

BACKGROUND

Patients of head and neck malignancies often develop oral mucositis and invite various pathogens to colonize over it.

OBJECTIVES

The objective of this study is to identify the fungi isolated from patients undergoing radiotherapy (RT) for head and neck cancer, to determine the antifungal susceptibility of these isolates and to determine the time and week of fungal colonization.

PATIENTS AND METHODS

Three specimens (throat, urine, and blood) were collected from each of the head and neck cancer patients, who were advised RT. These specimens, which were collected before the start of RT, during RT (2nd and 6th week), and post-RT (8th week) were inoculated into fungal culture media. Candida species were identified by standard methods and antifungal susceptibility of the candidal isolates was done.

RESULTS

Candida infection was found in 24/42 patients (57.14%) out of which Candida albicans was isolated in 14.28%, Candida tropicalis (28.57%) and Candida parapsilosis (14.28%). Maximum isolation of yeast was in the 6th week of RT. Fungemia was found in 3/42 patients. All the yeast isolates were sensitive to fluconazole except two.

CONCLUSION

Prophylactic antifungal therapy in patients undergoing RT for head and neck malignancy is particularly important to prevent intraoral colonization and infection by Candida. Screening of such patients on RT for fungal infections can prevent fatal mold infections.

Opportunistic Microorganisms in Oral Cavity According to Treatment Status in Head and Neck Cancer Patients

Introduction

Cancer patients receiving chemotherapy and/or radiation therapy are prone to many predisposing factors like immunosuppression, imbalance in the oral flora, hypo-salivation and local tissue damage. Therefore, considered to be at higher risk for oral bacterial and fungal infection than the general population.

Aim

To study oropharyngeal flora in head and neck cancer patients under treatment and to correlate their incidence according with Chemotherapy cycles and Radiochemotherapy.

Materials and Methods

Total 110 patients were selected for study, those were further divided into two groups, group I under Chemotherapy (CT) - 55 patients and group II under Radiochemotherapy (RCT) - 55 patients and 50 healthy individuals were taken as control. Saliva sample was collected from control and study group and inoculated on Blood agar, MacConkey agar and Sabouraud's Dextrose Agar (SDA). The identification of bacterial and fungal isolates was done by standard microbiological methods and result was calculated according to cycles of Chemotherapy and Radiochemotherapy combined. Significant differences between patients were tested using the Chi-square test or Fisher's exact test. A p-value less than 0.05 was considered as statistically significant.

Result

There were 149 culture isolates from 110 patient in which Gram Negative Bacilli (GNB) found in 63.6%, Candida spp. in 50%, Staphylococcus aureus in 8% and Normal commensal of oral cavity in 13.6% patients in study group and this was higher than control group and this difference was statistically significant in relation to all isolates individually. Relatively more microorganism were isolated during RCT (56%) in compare to CT alone (44%), among GNB- Pseudomonas (27.7%,32.3%) and Klebsiella (25%,29.4%) were most frequently isolated during CT, RCT respectively. Candida spp. were more commonly isolated from patient on RCT (63.6%) than CT (36.3%) when compared to control group (20%) among which C. tropicalis was more prevalent species. Both GNB & Candida spp. were more commonly isolated in later chemotherapy cycles (CT4, CT5 CT6).

Conclusion

Colonisation of Gram negative bacilli & Candida spp. is directly related to number of chemotherapy cycles and combined cancer therapy. Hence, prophylactic medication for these two organisms should be incorporated along with cancer therapy.

Dynamics of Mixed- Candida Species Biofilms in Response to Antifungals

Oral infections caused by Candida species, the most commonly isolated human fungal pathogen, are frequently associated with biofilms. Although Candida albicans is the predominant organism found in patients with oral thrush, a biofilm infection, there is an increasing incidence of oral colonization and infections caused by non- albicans Candida species, including C. glabrata, C. dubliniensis, and C. tropicalis, which are frequently more resistant to antifungal treatment. While single-species Candida biofilms have been well studied, considerably less is known about the dynamics of mixed- Candida species biofilms and how these dynamics are altered by antifungal treatment. To address these questions, we developed a quantitative polymerase chain reaction-based approach to determine the precise species composition of mixed- Candida species biofilms formed by clinical isolates and laboratory strains in the presence and absence of clinically relevant concentrations of 3 commonly used antifungals: fluconazole, caspofungin, and amphotericin B. In monospecies biofilms, fluconazole exposure favored growth of C. glabrata and C. tropicalis, while caspofungin generally favored significant growth of all species to a varying degree. Fluconazole was not effective against preformed mixed- Candida species biofilms while amphotericin B was potent. As a general trend, in mixed- Candida species biofilms, C. albicans lost dominance in the presence of antifungals. Interestingly, presence in mixed versus monospecies biofilms reduced susceptibility to amphotericin B for C. tropicalis and C. glabrata. Overall, our data suggest that antifungal treatment favors the growth of specific non- albicans Candida species in mixed- Candida species biofilms.

A retrospective study of 606 cases of nasopharyngeal carcinoma with or without oropharyngeal candidiasis during radiotherapy

Background

To evaluate the clinical characteristics, treatment-related toxicities and survival in patients with nasopharyngeal carcinoma (NPC) with or without oropharyngealcandidiasis (OPC) during radiotherapy.

Methods

The current study was conducted with NPC patients undergoing radiotherapy at Sun Yat-Sen University Cancer Center between June 2011 and May 2012. A clinical diagnosis of candidiasis was determined on the basis of a positive potassium hydroxide (KOH) test and the presence of pseudomembranous (white) form of candidal overgrowth. The Cox proportional hazard regression model was used to test the association of OPC and related survival rates.

Results

Compared with the non-OPC group, the OPC group had significantly increased occurrence rates of grade 3–4 mucositis (14.5% vs. 7.4%, P = 0.049), anaemia (11.3% vs. 4.4%, P = 0.020), hepatotoxicity (4.8% vs. 1.1%, P = 0.021) and critical weight loss (85.5% vs. 56.6%, P<0.001) during radiotherapy. The OPC group had a significantly lower disease-free survival (DFS) (70.9% vs. 82.6%, P = 0.012), mainly as a result of a reduction in locoregional relapse-free survival (LRFS) (87.0%vs. 94.9%, P = 0.025). After stratification by T stage, the 5-year DFS in T3-4 patients were 82.0% and 68.8% in non-OPC and OPC groups, respectively (P = 0.022). Multivariate analyses indicated that OPC was a prognostic factor for LRFS and DFS.

Conclusions

OPC during radiotherapy may worsen the nutritional status of NPC patients according to weight loss and anaemia, leading to a negative impact on 5-year locoregional relapse-free survival and disease-specific survival. Further investigations are needed to explore whether prevention and treatment of OPC during radiotherapy will be useful.

The Aryl Hydrocarbon Receptor Governs Epithelial Cell Invasion during Oropharyngeal Candidiasis

Oropharyngeal candidiasis (OPC), caused predominantly by Candida albicans, is a prevalent infection in patients with advanced AIDS, defects in Th17 immunity, and head and neck cancer. A characteristic feature of OPC is fungal invasion of the oral epithelial cells. One mechanism by which C. albicans hyphae can invade oral epithelial cells is by expressing the Als3 and Ssa1 invasins that interact with the epidermal growth factor receptor (EGFR) on epithelial cells and stimulate endocytosis of the organism. However, the signaling pathways that function downstream of EGFR and mediate C. albicans endocytosis are poorly defined. Here, we report that C. albicans infection activates the aryl hydrocarbon receptor (AhR), leading to activation of Src family kinases (SFKs), which in turn phosphorylate EGFR and induce endocytosis of the fungus. Furthermore, treatment of oral epithelial cells with interferon gamma inhibits fungal endocytosis by inducing the synthesis of kynurenines, which cause prolonged activation of AhR and SFKs, thereby interfering with C. albicans-induced EGFR signaling. Treatment of both immunosuppressed and immunocompetent mice with an AhR inhibitor decreases phosphorylation of SFKs and EGFR in the oral mucosa, reduces fungal invasion, and lessens the severity of OPC. Thus, our data indicate that AhR plays a central role in governing the pathogenic interactions of C. albicans with oral epithelial cells during OPC and suggest that this receptor is a potential therapeutic target.

OPC is caused predominantly by the fungus C. albicans, which can invade the oral epithelium by several mechanisms. One of these mechanisms is induced endocytosis, which is stimulated when fungal invasins bind to epithelial cell receptors such as EGFR. Receptor binding causes rearrangement of epithelial cell microfilaments, leading to the formation of pseudopods that engulf the fungus and pull it into the epithelial cell. We discovered AhR acts via SFKs to phosphorylate EGFR and induce the endocytosis of C. albicans. Our finding that a small molecule inhibitor of AhR ameliorates OPC in mice suggests that a strategy of targeting host cell signaling pathways that govern epithelial cell endocytosis of C. albicans holds promise as a new approach to preventing or treating OPC.

Spectrum of fungal infection in head and neck cancer patients on chemoradiotherapy

BACKGROUND

Radiotherapy for head and neck cancers (HNC) causes alteration of oral mucosal barrier predisposing it to colonization and infection. Such infections often result in pain and burning sensation thus contributing to major morbidity.

OBJECTIVE

MATERIALS AND METHODS: Study was done on 50 patients of HNC treated with concurrent chemoradiotherapy. Three samples (throat, urine, blood) were collected for fungal culture and sensitivity. These samples were collected before the start of radiotherapy, during radiotherapy (2nd and 6th week) and post radiotherapy (10th week).

RESULTS

Only 49 patients were available for analysis. Fungal infection was found in 27/49 patients (55.10%) out of which Non-albicans Candida was isolated in 18/49 (36.73%) and Candida albicans in 9/49 (18.36%) cases. About 66.66% (18/27) isolates were sensitive to fluconazole. Maximum isolation of yeast was during 6th week of radiotherapy. All grade 4 and 71.42% of grade 3 oral mucositis were found in patients who were positive for fungal infection.

CONCLUSION

The spectrum of fungal species in throat swab was: Non-albicans Candida and Candida albicans observed in 36.73% and 18.36% of patients respectively. Higher rate of fungal colonization and infection was found in patients with grade 3/4 oral mucositis. Prophylactic fluconazole in HNC patients on concurrent chemoradiotherapy has the potential to reduce emerging invasive fungal infection and its associated morbidity.

Pathogenesis of Candida albicans biofilm

Candida albicans is the most common human fungal pathogen causing diseases ranging from mucosal to systemic infections. As a commensal, C. albicans asymptomatically colonizes mucosal surfaces; however, any disruption in the host environment or under conditions of immune dysfunction, C. albicans can proliferate and invade virtually any site in the host. The ability of this highly adaptable fungal species to transition from commensal to pathogen is due to a repertoire of virulence factors. Specifically, the ability to switch morphology and form biofilms are properties central to C. albicans pathogenesis. In fact, the majority of C. albicans infections are associated with biofilm formation on host or abiotic surfaces such as indwelling medical devices, which carry high morbidity and mortality. Significantly, biofilms formed by C. albicans are inherently tolerant to antimicrobial therapy and therefore, the susceptibility of Candida biofilms to the current therapeutic agents remains low. The aim of this review is to provide an overview of C. albicans highlighting some of the diverse biofilm-associated diseases caused by this opportunistic pathogen and the animal models available to study them. Further, the classes of antifungal agents used to combat these resilient infections are discussed along with mechanisms of drug resistance.

The Host Cytokine Responses and Protective Immunity in Oropharyngeal Candidiasis

Over the last three decades, the prevalence of oropharyngeal fungal infections has increased enormously, mainly due to an increasing population of immunocompromised patients, including individuals with HIV infection, transplant recipients, and patients receiving cancer therapy. The vast majority of these infections are caused by Candida species. The presence of cytokines in infected tissues ultimately dictates the host defense processes that are specific to each pathogenic organism. During oral infection with Candida, a large number of pro-inflammatory and immunoregulatory cytokines are generated in the oral mucosa. The main sources of these cytokines are oral epithelial cells, which maintain a central role in the protection against fungal organisms. These cytokines may drive the chemotaxis and effector functions of innate and/or adaptive effector cells, such as infiltrating neutrophils and T-cells in immunocompetent hosts, and CD8+ T-cells in HIV+ hosts. Epithelial cells also have direct anti- Candida activity. Several studies have provided a potential link between lower levels of certain pro-inflammatory cytokines and susceptibility to oral C. albicans infection, suggesting that such cytokines may be involved in immune protection. The exact role of these cytokines in immune protection against oropharyngeal candidiasis is still incompletely understood and requires further investigation. Identification of such cytokines with the ability to enhance anti-fungal activities of immune effector cells may have therapeutic implications in the treatment of this oral infection in the severely immunocompromised host.

Total-Body Irradiation Exacerbates Dissemination of Cutaneous Candida Albicans Infection

Exposure to radiation, particularly a large or total-body dose, weakens the immune system through loss of bone marrow precursor cells, as well as diminished populations of circulating and tissue-resident immune cells. One such population is the skin-resident immune cells. Changes in the skin environment can be of particular importance as the skin is also host to a number of commensal organisms, including Candida albicans , a species of fungus that causes opportunistic infections in immunocompromised patients. In a previous study, we found that a 6 Gy sublethal dose of radiation in mice caused a reduction of cutaneous dendritic cells, indicating that the skin may have a poorer response to infection after irradiation. In this study, the same 6 Gy sublethal radiation dose led to a weakened response to a C. ablicans cutaneous infection, which resulted in systemic dissemination from the ear skin to the kidneys. However, this impaired response was mitigated through the use of interleukin-12 (IL-12) administered to the skin after irradiation. Concomitantly with this loss of local control of infection, we also observed a reduction of CD4⁺ and CD8⁺ T cells in the skin, as well as the reduced expression of IFN-γ, CXCL9 and IL-9, which influence T-cell infiltration and function in infected skin. These changes suggest a mechanism by which an impaired immune environment in the skin after a sublethal dose of radiation increases susceptibility to an opportunistic fungal infection. Thus, in the event of radiation exposure, it is important to include antifungal agents, or possibly IL-12, in the treatment regimen, particularly if wounds are involved that result in loss of the skin's physical barrier function.

Candida albicans Pathogenesis: Fitting within the Host-Microbe Damage Response Framework

Historically, the nature and extent of host damage by a microbe were considered highly dependent on virulence attributes of the microbe. However, it has become clear that disease is a complex outcome which can arise because of pathogen-mediated damage, host-mediated damage, or both, with active participation from the host microbiota. This awareness led to the formulation of the damage response framework (DRF), a revolutionary concept that defined microbial virulence as a function of host immunity. The DRF outlines six classifications of host damage outcomes based on the microbe and the strength of the immune response. In this review, we revisit this concept from the perspective of Candida albicans, a microbial pathogen uniquely adapted to its human host. This fungus commonly colonizes various anatomical sites without causing notable damage. However, depending on environmental conditions, a diverse array of diseases may occur, ranging from mucosal to invasive systemic infections resulting in microbe-mediated and/or host-mediated damage. Remarkably, C. albicans infections can fit into all six DRF classifications, depending on the anatomical site and associated host immune response. Here, we highlight some of these diverse and site-specific diseases and how they fit the DRF classifications, and we describe the animal models available to uncover pathogenic mechanisms and related host immune responses.

Managing xerostomia and salivary gland hypofunction: executive summary of a report from the American Dental Association Council on Scientific Affairs

BACKGROUND AND OVERVIEW

Xerostomia, also known as "dry mouth," is a common but frequently overlooked condition that is typically associated with salivary gland hypofunction, which is the objective measurement of reduced salivary flow. Patients with dry mouth exhibit symptoms of variable severity that are commonly attributed to medication use, chronic disease and medical treatment, such as radiotherapy to the head and neck region. Chronic xerostomia significantly increases the risk of experiencing dental caries, demineralization, tooth sensitivity, candidiasis and other oral diseases that may affect quality of life negatively. This article presents a multidisciplinary approach to the clinical management of xerostomia, consistent with the findings of published systematic reviews on this key clinical issue.

CONCLUSIONS AND PRACTICE IMPLICATIONS

Initial evaluation of patients with dry mouth should include a detailed health history to facilitate early detection and identify underlying causes. Comprehensive evaluation, diagnostic testing and periodic assessment of salivary flow, followed by corrective actions, may help prevent significant oral disease. A systematic approach to xerostomia management can facilitate interdisciplinary patient care, including collaboration with physicians regarding systemic conditions and medication use. Comprehensive management of xerostomia and hyposalivation should emphasize patient education and lifestyle modifications. It also should focus on various palliative and preventive measures, including pharmacological treatment with salivary stimulants, topical fluoride interventions and the use of sugar-free chewing gum to relieve dry-mouth symptoms and improve the patient's quality of life.

Oral Candidiasis among Cancer Patients Attending a Tertiary Care Hospital in Chennai, South India: An Evaluation of Clinicomycological Association and Antifungal Susceptibility Pattern

Oropharyngeal candidiasis is one of the common manifestations seen in cancer patients on cytotoxic therapy and invasion into deeper tissues can occur if not treated promptly. Emergence of antifungal drug resistance is of serious concern owing to the associated morbidity and mortality. The present study aims at evaluation of clinicomycological association and antifungal drug susceptibility among the 180 recruited patients with cancer on chemotherapy and/or radiotherapy with signs or symptoms suggestive of oral candidiasis. Speciation and antifungal susceptibility was done by Microbroth dilution method for fluconazole, Itraconazole, and Amphotericin B as per standard microbiological techniques. Chi-square test was used for statistical analysis (p < 0.05 was considered statistically significant). Candida albicans was the predominant species isolated (94) (58%) followed by Candida tropicalis (34) (20.9%). Fluconazole and Itraconazole showed an overall resistance rate of 14% and 14.8%, respectively. All the isolates were susceptible to Amphotericin B. There was a significant association between the presence of dry mouth and isolation of Candida (p < 0.001). Such clinicomicrobiological associations can help in associating certain symptoms with the isolation of Candida. Species level identification with in vitro antifungal susceptibility pattern is essential to choose the appropriate drug and to predict the outcome of therapy.

Targeting Candida albicans filamentation for antifungal drug development

Candida albicans remains the main etiological agent of candidiasis, as this otherwise normal commensal of humans is capable of causing active infection in immune- and medically-compromised patients. The high morbidity and mortality rates associated with candidiasis, coupled with the emergence of drug resistance demand the development of novel therapeutic strategies. However, there is a paucity of selective targets that can be exploited in the development of new antifungals. Contrary to conventional antibiotics that kill or curtail growth, specifically targeting virulence mechanisms represents an attractive option for antifungal drug development. In C. albicans, a growing body of research over the last few decades has provided important insights into its virulence factors and their contribution to the pathogenesis of candidiasis. Of these, filamentation is the one that has received the most attention and perhaps shows the most promise as a target for new anti-virulence strategies to combat C. albicans infections.

Candida glabrata Binding to Candida albicans Hyphae Enables Its Development in Oropharyngeal Candidiasis

Pathogenic mechanisms of Candida glabrata in oral candidiasis, especially because of its inability to form hyphae, are understudied. Since both Candida albicans and C. glabrata are frequently co-isolated in oropharyngeal candidiasis (OPC), we examined their co-adhesion in vitro and observed adhesion of C. glabrata only to C. albicans hyphae microscopically. Mice were infected sublingually with C. albicans or C. glabrata individually, or with both species concurrently, to study their ability to cause OPC. Infection with C. glabrata alone resulted in negligible infection of tongues; however, colonization by C. glabrata was increased by co-infection or a pre-established infection with C. albicans. Furthermore, C. glabrata required C. albicans for colonization of tongues, since decreasing C. albicans burden with fluconazole also reduced C. glabrata. C. albicans hyphal wall adhesins Als1 and Als3 were important for in vitro adhesion of C. glabrata and to establish OPC. C. glabrata cell wall protein coding genes EPA8, EPA19, AWP2, AWP7, and CAGL0F00181 were implicated in mediating adhesion to C. albicans hyphae and remarkably, their expression was induced by incubation with germinated C. albicans. Thus, we found a near essential requirement for the presence of C. albicans for both initial colonization and establishment of OPC infection by C. glabrata.

Spectrum and the In Vitro Antifungal Susceptibility Pattern of Yeast Isolates in Ethiopian HIV Patients with Oropharyngeal Candidiasis

Background. In Ethiopia, little is known regarding the distribution and the in vitro antifungal susceptibility profile of yeasts. Objective. This study was undertaken to determine the spectrum and the in vitro antifungal susceptibility pattern of yeasts isolated from HIV infected patients with OPC. Method. Oral pharyngeal swabs taken from oral lesions of study subjects were inoculated onto Sabouraud Dextrose Agar. Yeasts were identified by employing conventional test procedures and the susceptibility of yeasts to antifungal agents was evaluated by disk diffusion assay method. Result. One hundred and fifty-five yeast isolates were recovered of which 91 isolates were from patients that were not under HAART and 64 were from patients that were under HAART. C. albicans was the most frequently isolated species followed by C. glabrata, C. tropicalis, C. krusei, C. kefyr, Cryptococcus laurentii, and Rhodotorula species. Irrespective of yeasts isolated and identified, 5.8%, 5.8%, 12.3%, 8.4%, 0.6%, and 1.3% of the isolates were resistant to amphotericin B, clotrimazole, fluconazole, ketoconazole, miconazole, and nystatin, respectively. Conclusion. Yeast colonization rate of 69.2% and 31% resistance to six antifungal agents was documented. These highlight the need for nationwide study on the epidemiology of OPC and resistance to antifungal drugs.

Influence of cancer treatment on the Candida albicans isolated from the oral cavities of cancer patients

PURPOSE

Cancer treatment causes mucositis and the manifestation of oral candidiasis. This study investigated the virulence properties and antifungal susceptibilities of Candida albicans isolated from cancer patients undergoing therapy.

METHODS

C. albicans were isolated from 49 patients on cancer treatment and 21 healthy individuals and their virulence attributes measured. A correlation was determined between the length of treatment and the fungal counts and their virulence factors.

RESULTS

Although Candida carriage was similar in all the study groups, high quantities of C. albicans and variety of Candida were found in cancer patients. Germ tubes were produced by all the strains. Significantly high number of yeast isolated from radiotherapy and chemotherapy produced large quantities of phospholipase compared to healthy individuals (p < 0.01). The length of chemotherapy was associated with an increase in the phospholipase production (p = 0.03) by the C. albicans. Proteinase production was seen in a significant number of isolates from the radiotherapy group (p < 0.01). Type of cancer treatment had no effect. Resistance to antifungal agents was low.

CONCLUSIONS

High quantities of phospholipase were produced by C. albicans in cancer patients on therapy which also increased with the length of chemotherapy suggesting enhanced risk of oral and systemic infection. Therefore, during treatment, prophylactic topical antifungal therapy may be considered.

Occurrence of oral Candida colonization and its risk factors among patients with malignancies in China

OBJECTIVES

Oral colonization of Candida could lead to later development of oropharyngeal candidiasis or candidemia among the immunocompromised patients. This study aims to describe the occurrence and risk factors of oral Candida colonization in patients with malignancies.

MATERIALS AND METHODS

From October 2012 to March 2013, 78 patients with pulmonary cancer (group I), 101 patients with gastrointestinal tract tumor (group II), 79 patients with hematopoietic system malignant tumor (group III), and 101 healthy controls were consecutively recruited in a hospital in Beijing, China. The oral rinse samples were taken and Candida species were identified; the enzymes activities were tested.

RESULTS

In total, 110 and 27 Candida strains were isolated from 91 patients and 26 controls, respectively. The oral colonization rate with Candida albicans in group III (12.7 %) was significant lower than that in group I (30.8 %), group II (33.7 %), and control group (25.7 %). The oral colonization rates with non-albicans Candida species in group I, group II, and group III were 15.4, 10.9, and 12.7 %, respectively, while only one non-albicans Candida strain was identified in control group. The non-albicans Candida species exhibited a lower virulence than C. albicans. Age was an independent risk factor for Candida colonization in patients with pulmonary cancer and digestive tract malignant tumor, "Teeth brush <1 time/day" was an independent risk factor for Candida colonization in patients with hematopoietic system tumor.

CONCLUSIONS

The differences of risk factors for oral Candida colonization in patients with different cancers require different strategies for the prevention and control of Candida infection.

CLINICAL RELEVANCE

Old aged patients with pulmonary cancer and digestive tract malignant tumor are high-risk population for Candida colonization. Increasing frequency of teeth brush might be helpful for preventing Candida colonization.

Transcriptomic analysis of vulvovaginal candidiasis identifies a role for the NLRP3 inflammasome

Treatment of vulvovaginal candidiasis (VVC), caused most frequently by Candida albicans, represents a significant unmet clinical need. C. albicans, as both a commensal and a pathogenic organism, has a complex and poorly understood interaction with the vaginal environment. Understanding the complex nature of this relationship is necessary for the development of desperately needed therapies to treat symptomatic infection. Using transcriptome sequencing (RNA-seq), we characterized the early murine vaginal and fungal transcriptomes of the organism during VVC. Network analysis of host genes that were differentially expressed between infected and naive mice predicted the activation or repression of several signaling pathways that have not been previously associated with VVC, including NLRP3 inflammasome activation. Intravaginal challenge of Nlrp3(-/-) mice with C. albicans demonstrated severely reduced levels of polymorphonuclear leukocytes (PMNs), alarmins, and inflammatory cytokines, including interleukin-1β (IL-1β) (the hallmarks of VVC immunopathogenesis) in vaginal lavage fluid. Intravaginal administration of wild-type (WT) mice with glyburide, a potent inhibitor of the NLRP3 inflammasome, reduced PMN infiltration and IL-1β to levels comparable to those observed in Nlrp3(-/-) mice. Furthermore, RNA-seq analysis of C. albicans genes indicated robust expression of hypha-associated secreted aspartyl proteinases 4, 5, and 6 (SAP4-6), which are known inflammasome activators. Despite colonization similar to that of the WT strain, ΔSAP4-6 triple and ΔSAP5 single mutants induced significantly less PMN influx and IL-1β during intravaginal challenge. Our findings demonstrate a novel role for the inflammasome in the immunopathogenesis of VVC and implicate the hypha-associated SAPs as major C. albicans virulence determinants during vulvovaginal candidiasis.

IMPORTANCE

Vaginitis, most commonly caused by the fungus Candida albicans, results in significant quality-of-life issues for all women of reproductive age. Recent efforts have suggested that vaginitis results from an immunopathological response governed by host innate immunity, although an explanatory mechanism has remained undefined. Using comprehensive genomic, immunological, and pharmacological approaches, we have elucidated the NLRP3 inflammasome as a crucial molecular mechanism contributing to host immunopathology. We have also demonstrated that C. albicans hypha-associated secreted aspartyl proteinases (SAP4-6 and SAP5, more specifically) contribute to disease immunopathology. Ultimately, this study enhances our understanding of the complex interplay between host and fungus at the vaginal mucosa and provides proof-of-principle evidence for therapeutic targeting of inflammasomes for symptomatic vulvovaginal candidiasis.

New signaling pathways govern the host response to C. albicans infection in various niches

Candida albicans, the major invasive fungal pathogen of humans, can cause both debilitating mucosal infections and fatal invasive infections. Understanding the complex nature of the host-pathogen interaction in each of these contexts is essential to developing desperately needed therapies to treat fungal infections. RNA-seq enables a systems-level understanding of infection by facilitating comprehensive analysis of transcriptomes from multiple species (e.g., host and pathogen) simultaneously. We used RNA-seq to characterize the transcriptomes of both C. albicans and human endothelial cells or oral epithelial cells during in vitro infection. Network analysis of the differentially expressed genes identified the activation of several signaling pathways that have not previously been associated with the host response to fungal pathogens. Using an siRNA knockdown approach, we demonstrate that two of these pathways-platelet-derived growth factor BB (PDGF BB) and neural precursor-cell-expressed developmentally down-regulated protein 9 (NEDD9)-govern the host-pathogen interaction by regulating the uptake of C. albicans by host cells. Using RNA-seq analysis of a mouse model of hematogenously disseminated candidiasis (HDC) and episodes of vulvovaginal candidiasis (VVC) in humans, we found evidence that many of the same signaling pathways are activated during mucosal (VVC) and/or disseminated (HDC) infections in vivo. Our analyses have uncovered several signaling pathways at the interface between C. albicans and host cells in various contexts of infection, and suggest that PDGF BB and NEDD9 play important roles in this interaction. In addition, these data provide a valuable community resource for better understanding host-fungal pathogen interactions.

Effects of bovine lactoferrin to oral Candida albicans and Candida glabrata isolates recovered from the saliva in elderly people

The effects of bovine lactoferrin (bLF) on the growth of Candida species and on inflammatory cytokine production in gingival keratinocytes, NDUSD-1 co-cultured with Candida strains were investigated. The results showed that bLF at 10 and 100 lg/mL significantly inhibits the growth of two C. albicans strains and two C. glabrata strains isolated from the saliva of elderly people requiring nursing care, respectively. The levels of inflammatory cytokines, interleukin (IL)-6, and IL-8 in NDUSD-1 cocultured with each of these four Candida strains were measured. C. albicans tend to have a more potent capacity than C. glabrata to induce the production of the inflammatory cytokines in NDUSD-1. The levels of IL-6 and IL-8 in NDUSD-1 co-cultured with each of Candida species were measured after addition of bLF. bLF at concentrations from 1 to 100 lg/mL significantly inhibited the production of these cytokines in NDUSD-1 co-cultured with Candida species. These findings suggest that bLF may be useful in reducing the risk of aspiration pneumonia among elderly people requiring care for whom oral care is difficult.

Radiation exposure induces inflammasome pathway activation in immune cells

Radiation exposure induces cell and tissue damage, causing local and systemic inflammatory responses. Because the inflammasome pathway is triggered by cell death and danger-associated molecular patterns, we hypothesized that the inflammasome may signal acute and chronic immune responses to radiation. Using a mouse radiation model, we show that radiation induces a dose-dependent increase in inflammasome activation in macrophages, dendritic cells, NK cells, T cells, and B cells as judged by cleaved caspase-1 detection in cells. Time course analysis showed the appearance of cleaved caspase-1 in cells by day 1 and sustained expression until day 7 after radiation. Also, cells showing inflammasome activation coexpressed the cell surface apoptosis marker annexin V. The role of caspase-1 as a trigger for hematopoietic cell losses after radiation was studied in caspase-1(-/-) mice. We found less radiation-induced cell apoptosis and immune cell loss in caspase-1(-/-) mice than in control mice. Next, we tested whether uric acid might mediate inflammasome activation in cells by treating mice with allopurinol and discovered that allopurinol treatment completely blocked caspase-1 activation in cells. Finally, we demonstrate that radiation-induced caspase-1 activation occurs by a Nod-like receptor family protein 3-independent mechanism because radiation-exposed Nlrp3(-/-) mice showed caspase-1 activation profiles that were indistinguishable from those of wild-type mice. In summary, our data demonstrate that inflammasome activation occurs in many immune cell types following radiation exposure and that allopurinol prevented radiation-induced inflammasome activation. These results suggest that targeting the inflammasome may help control radiation-induced inflammation.

Host cell invasion by medically important fungi

To infect the host and cause disease, many medically important fungi invade normally nonphagocytic host cells, such as endothelial cells and epithelial cells. Host cell invasion is a two-step process consisting of adherence followed by invasion. There are two general mechanisms of host cell invasion, induced endocytosis and active penetration. Furthermore, fungi can traverse epithelial or endothelial cell barriers either by proteolytic degradation of intercellular tight junctions or via a Trojan horse mechanism in which they are transported by leukocytes. Although these mechanisms of host cell invasion have been best studied using Candida albicans and Cryptococcus neoformans, it is probable that other invasive fungi also use one or more of these mechanisms to invade host cells. Identification of these invasion mechanisms holds promise to facilitate the development of new approaches to inhibit fungal invasion and thereby prevent disease.