Candida glabrata: an emerging oral opportunistic pathogen

Dissection of Ire1 functions reveals stress response mechanisms uniquely evolved in Candida glabrata

Proper protein folding in the endoplasmic reticulum (ER) is vital in all eukaryotes. When misfolded proteins accumulate in the ER lumen, the transmembrane kinase/endoribonuclease Ire1 initiates splicing of HAC1 mRNA to generate the bZIP transcription factor Hac1, which subsequently activates its target genes to increase the protein-folding capacity of the ER. This cellular machinery, called the unfolded protein response (UPR), is believed to be an evolutionarily conserved mechanism in eukaryotes. In this study, we comprehensively characterized mutant phenotypes of IRE1 and other related genes in the human fungal pathogen Candida glabrata. Unexpectedly, Ire1 was required for the ER stress response independently of Hac1 in this fungus. C. glabrata Ire1 did not cleave mRNAs encoding Hac1 and other bZIP transcription factors identified in the C. glabrata genome. Microarray analysis revealed that the transcriptional response to ER stress is not mediated by Ire1, but instead is dependent largely on calcineurin signaling and partially on the Slt2 MAPK pathway. The loss of Ire1 alone did not confer increased antifungal susceptibility in C. glabrata contrary to UPR-defective mutants in other fungi. Taken together, our results suggest that the canonical Ire1-Hac1 UPR is not conserved in C. glabrata. It is known in metazoans that active Ire1 nonspecifically cleaves and degrades a subset of ER-localized mRNAs to reduce the ER load. Intriguingly, this cellular response could occur in an Ire1 nuclease-dependent fashion in C. glabrata. We also uncovered the attenuated virulence of the C. glabrata Δire1 mutant in a mouse model of disseminated candidiasis. This study has unveiled the unique evolution of ER stress response mechanisms in C. glabrata.

Pseudomembranous candidiasis in HIV/AIDS patients in Cali, Colombia

Candida albicans is the most frequently isolated yeast from the oral cavity of HIV/AIDS individuals. The use of fluconazole has increased the number of resistant or less-sensitive Candida species different than C. albicans. The purpose of this study was to identify the Candida species producing pseudomembranous candidiasis in patients suffering from AIDS, their relationship with CD4(+) counts and their sensitivity to fluconazole and itraconazole. We studied 71 patients at a hospital in the city of Cali. Samples of white plaque were seeded on CHROMagar Candida, yeast identification was done with API 20C Aux, and susceptibility testing was determined by E test. Ninety-three yeast isolates were obtained, 52 single and 41 mixed. C. albicans was the most isolated, followed by C. glabrata. An increased frequency of isolates and variety of Candida species occurred in patients with a CD4(+) cell count ≤100 cells/mm(3) without significant differences (p = 0.29). The susceptibility study showed that 8 (8.6%) isolates were resistant to fluconazole and 11 (11.8%) to itraconazole, while 6 (8.8%) C. albicans were simultaneously resistant. No association was found between the isolates of C. albicans or Candida species different than C. albicans and the use of fluconazole (p = 0.21). The results of this study indicate that in the tested population, fluconazole continues to be the best treatment option for oropharyngeal candidiasis in patients suffering from AIDS (HIV/AIDS); however, susceptibility tests are necessary in patients who present therapeutic failure.

Effects of undecylenic acid released from denture liner on Candida biofilms

Denture liners (DL) are easily colonized by Candida spp. In an attempt to prevent biofilm colonization, manufacturers have incorporated undecylenic acid (UDA) into DL. In this in vitro study, the effects of UDA released from DL on Candida biofilms were investigated. The concentrations of UDA released from commercial DL were determined by gas chromatography-mass spectrometry (GC-MS). Minimum inhibitory concentration (MIC) and minimum fungistatic concentration (MFC) tests were performed for C. albicans or C. glabrata, with UDA for comparison with the concentrations released from DL. Specimens of DL with (experimental group) and without UDA (control group) were fabricated, and Candida biofilms were developed on DL surfaces. Biofilms were evaluated by cell counts, metabolic activity, structure, and secretion of proteinase or phospholipase. The concentrations of UDA released were within the MIC and MFC ranges. In the presence of UDA, C. albicans biofilms were thinner and had lower numbers of viable and active cells, although no significant enzymatic changes were observed relative to the control group (p > 0.05). In contrast, C. glabrata biofilms exhibited higher cell counts and greater metabolic activity and also increased proteinase activity in the presence of UDA relative to the control group (p < 0.05). Overall, UDA did not prevent Candida biofilm formation.

In vitro adhesion of Candida glabrata to denture base acrylic resin modified by glow-discharge plasma treatment

This study evaluated the potential of plasma treatments to modify the surface chemistry and hydrophobicity of a denture base acrylic resin to reduce the Candida glabrata adhesion. Specimens (n = 54) with smooth surfaces were made and divided into three groups (n = 18): control - non-treated; experimental groups - submitted to plasma treatment (Ar/50 W; AAt/130 W). The effects of these treatments on chemical composition and surface topography of the acrylic resin were evaluated. Surface free energy measurements (SFE) were performed after the treatments and after 48 h of immersion in water. For each group, half (n = 9) of the specimens were preconditionated with saliva before the adhesion assay. The number of adhered C. glabrata was evaluated by cell counting after crystal violet staining. The Ar/50 W and AAt/130 W treatments altered the chemistry composition, hydrophobicity and topography of acrylic surface. The Ar/50 W group showed significantly lower C. glabrata adherence than the control group, in the absence of saliva. After preconditioning with saliva, C. glabrata adherence in experimental and control groups did not differ significantly. There were significant changes in the SFE after immersion in water. The results demonstrated that Ar/50 W treated surfaces have potential for reducing C. glabrata adhesion to denture base resins and deserve further investigation, especially to tailor the parameters to prolong the increased wettability.

A comparative in vitro study of two denture cleaning techniques as an effective strategy for inhibiting Candida albicans biofilms on denture surfaces and reducing inflammation

PURPOSE

 Candida albicans is the predominant oral yeast associated with denture-induced stomatitis, and with an increasing population of denture wearers its incidence is increasing. Maintaining good oral and denture hygiene, through chemical and/or mechanical intervention, is essential to reducing this disease. The aim of this study, using a robust adherent C. albicans cell model system, was to evaluate and compare the efficacy of a novel denture cleanser to the efficacy of a commonly used dentifrice coupled with brushing.

MATERIALS AND METHODS

Four C. albicans strains isolated from individuals diagnosed as having denture-induced stomatitis, were adhered to denture acrylic resin sections (1 cm(2) by 1 mm thickness) and after 4 hours of growth, challenged daily sequentially for 4 days with a denture cleanser (Polident) or intermittently with denture cleanser (day 1), then dentifrice (Colgate Cavity Protection Toothpaste) and brushing (days 2 and 3) and denture cleanser (day 4). Colony forming units were evaluated for each treatment, as were the levels of regrowth. Scanning electron microscopy (SEM) was also performed. Microbial susceptibility testing and time-kill studies were performed on biofilms. A coculture model was also used to assess interleukin-8 (IL-8) production from treated biofilms.

RESULTS

It was shown that sequential treatment with the denture cleanser killed and inhibited regrowth each day. Intermittent treatment showed that viable C. albicans biofilms were only retained rather than being dispersed, which could be visualized by SEM. Time-kill studies demonstrated that the novel denture cleanser was highly active and killed quickly, unlike the dentifrice. IL-8 was expressed in greater levels in 24-hour biofilms than in 4-hour biofilms, but treatment with denture cleanser reduced IL-8 output.

CONCLUSIONS

The data indicate that maintaining good oral health for denture wearers requires daily use of a denture cleanser rather than an alternating regimen. The inability of the denture cleanser to sterilize during intermittent treatments demonstrates the difficulty in controlling established biofilm. Moreover, the presence of mature biofilm may result in high levels of inflammation, but this can be controlled through denture cleansing.

Association of fixed partial denture and gingival prosthesis as alternative approach to recover esthetics and function in anterior maxillary region

Tooth replacement in the maxillary anterior region is especially difficult when the loss includes significant amounts of the residual ridge and the soft tissue. Several techniques are available, such as dental implants or fixed partial denture, and bone and gingival grafts or gingival prostheses, respectively. This article showed a clinical case of an elderly who was treated with a collarless metal-ceramic fixed partial denture and acrylic removable gingival prosthesis to recover the esthetics in the maxillary anterior region. The association of a metal-ceramic fixed denture and gingival prosthesis was an excellent alternative in cases when surgical procedures are contraindicated.

Synthesis, anti-Candida activity, and cytotoxicity of new (4-(4-iodophenyl)thiazol-2-yl)hydrazine derivatives

Novel (4-(4-iodophenyl)-thiazol-2-yl)hydrazine derivatives were assayed for their in vitro anti-Candida activity, compared to topical and systemic antifungal drugs, against twenty-seven clinical isolates. The presence of aliphatic chains or specific heteroaromatic rings on hydrazone moiety at position C2 and a 4-iodophenyl at C4 of the thiazole ring gave a promising inhibitory activity especially against Candida albicans and Candida krusei. The most active compounds have been also evaluated for their cytotoxicity and in association with clotrimazole for anti-Candida activity.

Oral colonization by yeasts in HIV-positive patients in Brazil

INTRODUCTION: In HIV-infected patients, colonization of the oral cavity by potential pathogenic yeast may lead to development of systemic fungemia. We evaluated the prevalence of yeast in the oral cavity of Brazilian HIV-positive patients and verified whether or not the species characterized were enzymatically active. Furthermore, the species identified were tested for their susceptibility to antifungal treatment. METHODS: Patient saliva and oropharyngeal candidiasis samples were collected from 60 seropositive HIV patients and identified by the API20C system. Enzymatic activity was evaluated by the production of proteinase and phospholipase. Susceptibility to antifungal treatments were determined using the broth microdilution method. RESULTS: the most commonly isolated species were C. albicans (51.56%) followed by non-albicans Candida species (43.73%), Trichosporon mucoides (3.12%) and Kodamaea ohmeri (1.56%). Oral colonization by association of different species was observed in 42% of the patients. Enzymatic activity was verified in most of species isolated, except for C. glabrata, C. lusitaniae and C. guilliermondii. Resistance to Fluconazole and Amphotericin B was observed in isolates of C. albicans, C. glabrata, C. parapsilosis, C. krusei, and K. ohmeri. CONCLUSION: HIV-positive patients are orally colonized by single or multiple species of yeast that are occasionally resistant to Fluconazole or Amphotericin B.

Murine model of dextran sulfate sodium-induced colitis reveals Candida glabrata virulence and contribution of β-mannosyltransferases

Candida glabrata, like Candida albicans, is an opportunistic yeast pathogen that has adapted to colonize all segments of the human gastrointestinal tract and vagina. The C. albicans cell wall expresses β-1,2-linked mannosides (β-Mans), promoting its adherence to host cells and tissues. Because β-Mans are also present in C. glabrata, their role in C. glabrata colonization and virulence was investigated in a murine model of dextran sulfate sodium (DSS)-induced colitis. Five clustered genes of C. glabrata encoding β-mannosyltransferases, BMT2-BMT6, were deleted simultaneously. β-Man expression was studied by Western blotting, flow cytometry, and NMR analysis. Mortality, clinical, histologic, and colonization scores were determined in mice receiving DSS and different C. glabrata strains. The results show that C. glabrata bmt2-6 strains had a significant reduction in β-1,2-Man expression and a disappearance of β-1,2-mannobiose in the acid-stable domain. A single gavage of C. glabrata wild-type strain in mice with DSS-induced colitis caused a loss of body weight, colonic inflammation, and mortality. Mice receiving C. glabrata bmt2-6 mutant strains had normal body weight and reduced colonic inflammation. Lower numbers of colonies of C. glabrata bmt2-6 were recovered from stools and different parts of the gastrointestinal tract. Histopathologic examination revealed that the wild-type strain had a greater ability to colonize tissue and cause tissue damage. These results showed that C. glabrata has a high pathogenic potential in DSS-induced colitis, where β-Mans contribute to colonization and virulence.

Denture stomatitis treated with photodynamic therapy: five cases

OBJECTIVE

Photodynamic therapy (PDT) is an effective method for Candida spp. inactivation in vitro and in vivo, but as yet, no clinical trial has been conducted. This report describes 5 cases of denture stomatitis (DS) treated with PDT.

STUDY DESIGN

Five subjects with clinical and microbiologic diagnosis of DS were submitted to 6 sessions of PDT 3 times a week for 15 days. In each session, patients' dentures and palates were sprayed with 500 mg/L Photogem, and, after 30 minutes of incubation, irradiated by light-emitting diode light source at 455 nm (37.5 and 122 J/cm(2), respectively). Cultures of Candida spp. from dentures and palates and standard photographs of the palates were taken at baseline (day 0), at the end of the treatment (day 15), and at follow-up time intervals (days 30 and 60).

RESULTS

Four patients showed clinical resolution of DS (no inflammation) after PDT sessions, and only 1 subject demonstrated reduction in palatal inflammation. Recurrence of DS was observed in 2 patients during the follow-up period.

CONCLUSIONS

PDT appears to be an alternative treatment for DS.

Interventions for prevention and treatment of vulvovaginal candidiasis in women with HIV infection

BACKGROUND

Vulvovaginal candidiasis (VVC) is one of the most common fungal infections that recur frequently in HIV infected women. Symptoms of VVC are pruritis, discomfort, dyspareunia, and dysuria. Vulval infection presents as a morbiliform rash that may extend to the thighs. Vaginal infection is associated with white discharge, and plaques are seen on erythematous vaginal walls.Even though rarely or never resulting in systemic fungal infection or mortality, left untreated these lesions contribute considerably to the morbidity associated with HIV infection. Prevention and treatment of this condition is an essential part of maintaining the quality of life for these individuals.

OBJECTIVES

-To compare the efficacy of various antifungals given vaginally or orally for the treatment and prophylaxis of VVC in HIV-infected women and to evaluate the risks of the same.

SEARCH STRATEGY

The search strategy was comprehensive, iterative and based on that of the HIV/AIDS Cochrane Review Group. The aim was to locate all relevant trials, irrespective of publication status or language. Electronic databases :CENTRAL,Medline, EMBASE, LILACS and CINAHL were searched for randomised controlled trials for the years 1980 to 1st October 2010. WHO ICTRP site and other relevant web sites were also searched for conference abstracts.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of palliative, preventative or curative therapy were considered. Participants were HIV positive women receiving one or more of the following:treatment / prophylaxis for VVC or HAART(Highly Active Antiretroviral Therapy).

DATA COLLECTION AND ANALYSIS

Three authors independently assessed the methodological quality of the trials and extracted data. The quality of the evidence generated was graded using the GRADE PRO approach.

MAIN RESULTS

Our search did not yield any trial investigating treatment of VVC in HIV positive women.Two trials dealing with prophylaxis were eligible for inclusion.One trial (n= 323) favoured the use of weekly Fluconazole as compared to placebo (RR 0.68; 95% CI 0.47 to 0.97).The second trial with three arms of comparison;Clotrimazole,Lactobacillus and Placebo gave no definitive results in preventing an episode of VVC. Clotrimazole against placebo (RR 0.49; 95% CI 0.22 to 1.09), Clotrimazole against lactobacillus (RR 1.11; 95% CI 0.45 to 2.76) and lactobacillus against placebo (RR 0.54 ;95% CI 0.26 to 1.13).

AUTHORS' CONCLUSIONS

Implications for practiceNo trials were found addressing treatment of VVC in HIV positive women.In comparison to placebo,Fluconazole was found to be an effective preventative intervention. However, the potential for resistant Candida organisms to develop might impact the feasibility of implementation.Direction of findings suggests that Clotrimazole and Lactobacillus improved the prophylactic outcomes when compared to placebo.Implications for research There is a need to evaluate drugs and drug regimens for VVC treatment and prophylaxis in HIV positive women through randomised clinical trials. Development of resistance to azoles remains under-studied and more work must be done in this area, so as to determine whether routine prophylaxis for VVC is at all needed or whether adequate ART would be sufficient to prevent recurrent VVC. The viral load in vaginal secretions with or without treatment or prophylaxis has not been studied, this is very relevant to the spread of HIV.

The small molecular mass antifungal protein of Penicillium chrysogenum--a mechanism of action oriented review

The β-lactam producing filamentous fungus Penicillium chrysogenum secretes a 6.25 kDa small molecular mass antifungal protein, PAF, which has a highly stable, compact 3D structure and is effective against a wide spectrum of plant and zoo pathogenic fungi. Its precise physiological functions and mode of action need to be elucidated before considering possible biomedical, agricultural or food technological applications. According to some more recent experimental data, PAF plays an important role in the fine-tuning of conidiogenesis in Penicillium chrysogenum. PAF triggers apoptotic cell death in sensitive fungi, and cell death signaling may be transmitted through two-component systems, heterotrimeric G protein coupled signal transduction and regulatory networks as well as via alteration of the Ca(2+) -homeostasis of the cells. Possible biotechnological applications of PAF are also outlined in the review.

Rapid discrimination between Candida glabrata, Candida nivariensis, and Candida bracarensis by use of a singleplex PCR

We report here a PCR-based assay using a single primer pair targeting the RPL31 gene that allows discrimination between Candida glabrata, Candida bracarensis, and Candida nivariensis according to the size of the generated amplicon.

Fungicidal effect of photodynamic therapy against fluconazole-resistant Candida albicans and Candida glabrata

Although photodynamic therapy (PDT) has shown great promise for the inactivation of Candida species, its effectiveness against azole-resistant pathogens remains poorly documented. This in vitro study describes the association of Photogem® (Photogem, Moscow, Russia) with LED (light emitting diode) light for the photoinactivation of fluconazole-resistant (FR) and American Type Culture Collection (ATCC) strains of Candida albicans and Candida glabrata. Suspensions of each Candida strain were treated with five Photogem® concentrations and exposed to four LED light fluences (14, 24, 34 or 50 min of illumination). After incubation (48 h at 37 °C), colonies were counted (CFU ml(-1)). Single-species biofilms were generated on cellulose membrane filters, treated with 25.0 mg l(-1) of Photogem® and illuminated at 37.5 J cm(-2). The biofilms were then disrupted and the viable yeast cells present were determined. Planktonic suspensions of FR strains were effectively killed after PDT. It was observed that the fungicidal effect of PDT was strain-dependent. Significant decreases in biofilm viability were observed for three strains of C. albicans and for two strains of C. glabrata. The results of this investigation demonstrated that although PDT was effective against Candida species, fluconazole-resistant strains showed reduced sensitivity to PDT. Moreover, single-species biofilms were less susceptible to PDT than their planktonic counterparts.

Bioactivity and cellular structure of Candida albicans and Candida glabrata biofilms grown in the presence of fluconazole

OBJECTIVE

The aim of this study was to evaluate whether fluconazole (FLZ) could affect the bioactivity and cellular structure of Candida albicans or Candida glabrata biofilms grown in the presence of FLZ.

MATERIALS AND METHODS

Tokens were fabricated using poly(methylmethacrylate) resin (PMMA) in a hot water bath. Salivary pellicles were formed on the PMMA surface, and biofilms of a reference strain and two clinical isolates of C. albicans (ATCC 90028, P01 and P34) and C. glabrata (ATCC 2001, P11 and P31) were developed for a period of 48 h. Control and experimental groups were formed. FLZ at the bioavailable concentration in saliva (2.56 μg/mL) was added to the medium of the experimental group. The culture mediums of the control and experimental groups were changed after 24h. The bioactivities of the biofilms were evaluated using an XTT reduction colorimetric assay. The cellular structure was analysed by confocal scanning laser microscopy and by transmission electron microscopy. The data were analysed by the independent sample Student's t-test, with the significance level set at 5%.

RESULTS

The presence of FLZ decreased the bioactivity of all C. albicans biofilms (p<0.001), however, it did not change the cellular structure of C. albicans P34. Regarding the C. glabrata biofilm bioactivity and structure, no statistically significant differences were found between the control and experimental groups.

CONCLUSION

FLZ, at the bioavailable concentration present in saliva, interferes with the development of C. albicans biofilms, but does not interfere with the development of C. glabrata biofilms.

Genotypic, phenotypic, and proteomic characterization of Candida glabrata during sequential fluconazole exposure

AIM

Candida glabrata is a major pathogen in humans known to be intrinsically resistant to fluconazole. However, genotypic, phenotypic, and proteomic changes associated with reduced susceptibility to fluconazole are not properly understood. The aim of this study was to observe specific phenotypic, chromosomal, and proteomic alterations in a Candida glabrata strain sequentially exposed to fluconazole.

METHODS

Candida glabrata was exposed to increased concentrations of fluconazole in RPMI for 55 days. Phenotypic changes were evaluated using standard assays. Molecular/proteomic changes in C. glabrata were analyzed by contour-clamped homogeneous electric field electrophoresis, reverse transcription-polymerase chain reaction, and mass spectrometry.

RESULTS

  Candida glabrata demonstrated increased fluconazole resistance (>256 μg/mL), with extensive cross-resistance to ketoconazole (0.38-3.0 μg), itraconazole (8 to >32 μg), and voriconazole (0.125-1.5 μg). Morphologically dissimilar colonies on RPMI/fluconazole agar demonstrated variable chromosomal profiles compared with the control isolate. Stable chromosomal changes were associated with a significantly higher (P<0.05) mRNA level of the hemolysin gene compared with the control. Phenotypic switching on CuSO4 agar was associated with variable metallothionein mRNA transcription levels. The proteome analysis of a fluconazole-resistant offshoot demonstrated a total of 98 protein spots, 25 showing a twofold upregulation.

CONCLUSION

Fluconazole exposure initiates the chance evolution of a new colonizing population with specific virulence traits.

Human pathogenic fungi in China--emerging trends from ongoing national survey for 1986, 1996, and 2006

This epidemiological survey was a retrospective study on three nodes during the past three decades on fungal infections representing the China, including Taiwan. Owing to rare publications reporting on dynamic epidemiological trends in the pathogen epidemiology in China, we surveyed the isolation rates and pathogenic fungi from 8 representative districts in China using uniform identification with uniform methodology. The pathogenic fungi isolation rates and species obtained from 1986 (n=9,096), 1996 (n=19,009), and 2006 (n=33,022) suggested that Trichophyton rubrum was the commonest organism cultured in 1980s (45.4%) and 1990s (34.5%), but Candida albicans increased significantly and reaching to its peak (26.9%) in 2006s' survey, and has become the most common isolate of fungal infections in China currently. In addition, Candida glabrata became the most common non-albicans species of Candida in 2006s' survey. At the same time, the incidence of molds also gradually increased. According to comparative analysis of the results of these three surveys, we found apparent differences in the isolation rates of different pathogenic fungi and the forefront 10 species in China varied significantly, and the dermatophytes decreased markedly, while yeasts, especially the Candida species and the molds, increased gradually during the past three decades. Less dermatophytic infections may suggest better access to healthcare or increase in Candida species indicated higher incidence of hospital acquired infections.

Differences in proteolytic activity and gene profiles of fungal strains isolated from the total parenteral nutrition patients

Fungal infections constitute a serious clinical problem in the group of patients receiving total parenteral nutrition. The majority of species isolated from infections of the total parenteral nutrition patients belong to Candida genus. The most important factors of Candida spp. virulence are the phenomenon of “phenotypic switching,” adhesins, dimorphism of fungal cells and the secretion of hydrolytic enzymes such as proteinases and lipases, including aspartyl proteinases. We determined the proteolytic activity of yeast-like fungal strains cultured from the clinical materials of patients receiving total parenteral nutrition and detected genes encoding aspartyl proteinases in predominant species Candida glabrata—YPS2, YPS4, and YPS6, and Candida albicans—SAP1–3, SAP4, SAP5, and SAP6. C. albicans released proteinases on the various activity levels. All C. glabrata strains obtained from the clinical materials of examined and control groups exhibited secretion of the proteinases. All 13 isolates of C. albicans possessed genes SAP1–3. Gene SAP4 was detected in genome of 11 C. albicans strains, SAP5 in 6, and SAP6 in 11. Twenty-six among 31 of C. glabrata isolates contained YPS2 gene, 21 the YPS4 gene, and 28 the YPS6 gene. We observed that clinical isolates of C. albicans and C. glabrata differed in SAPs and YPSs gene profiles, respectively, and displayed differentiated proteolytic activity. We suppose that different sets of aspartyl proteinases genes as well as various proteinase-activity levels would have the influence on strains virulence.

Oxidative stress response and virulence factors in Candida glabrata clinical isolates

We determined the susceptibility to oxidative stress and assessed the four virulence factors of the 38 Candida glabrata clinical isolates originating from two teaching hospitals in Slovakia. All the isolates were susceptible to hydrogen peroxide, diamide, and 7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine (CTBT) inducing an increased formation of reactive oxygen species in fungal cells. The mean relative cell surface hydrophobicity (CSH) of isolates was 21.9, ranging from 1.92 to 56.96. All isolates showed biofilm formation. A high biofilm formation was observed among 60.5% of isolates. Positive correlations were observed between biofilm formation and moderate values of CSHs. The 76.3% and 84.2% of isolates displayed varying degrees of proteinase and phospholipase activity, respectively. These results demonstrate a differential distribution of factors contributing to virulence of C. glabrata clinical isolates and point to their significance in pathogenesis that would be targeted by novel antifungals.

Detection and identification of non-Candida albicans species in human oral lichen planus

Candida species were detected and identified in samples from the buccal mucosa, dorsal surface of the tongue and supragingival plaque of subjects with oral lichen planus (OLP). The Candida in the samples were cultured on selection agars, and identified by sequence analyses of 18S, 5.8S and 25/28S rRNA. The isolation frequency of Candida was higher in subjects with OLP than in those with healthy oral mucosa. Non-C. albicans were only isolated from people with OLP. These results support the notion that subjects with OLP are more likely to have oral colonization with Candida, and that non-C. albicans are specifically present in subjects with this condition.

Candida glabrata and Candida albicans co-infection of an in vitro oral epithelium

BACKGROUND

Candida albicans is regarded as the leading of candidosis. However, Candida glabrata has emerged as an important pathogen of oral mucosa, occurring both singly or in mixed species infections, often with C. albicans. Compared with C. albicans, little is known about the role of C. glabrata in oral infection. The aim of this study was to examine single and mixed species infection of oral epithelium involving C. glabrata and establish its ability to invade and damage tissue.

METHODS

A reconstituted human oral epithelium (RHOE) was infected only with C. glabrata, or simultaneously with C. glabrata and C. albicans. The ability of both species to invade the tissue was examined using species specific peptide nucleic acid (PNA) probe hybridization and confocal laser scanning microscopy. Epithelial damage was assessed by measuring lactate dehydrogenase (LDH) activity.

RESULTS

Candida glabrata strains were able to colonize the RHOE, in a strain dependent manner. Candida glabrata single infection after 12 h, generally revealed no invasion of the RHOE, which contrasted with extensive tissue invasion demonstrated by C. albicans. Mixed infection showed that C. albicans enhanced the invasiveness of C. glabrata, and led to increased LDH release by the RHOE, which paralleled the observed histological damage.

CONCLUSIONS

The results obtained demonstrating enhanced invasion and increased tissue damage caused by mixed C. glabrata and C. albicans infections have important clinical significance and highlight the need to identify Candida species involved in oral candidosis.

Regulation of Candida glabrata oxidative stress resistance is adapted to host environment

The human fungal pathogen Candida glabrata is related to Saccharomyces cerevisiae but has developed high resistance against reactive oxygen species. We find that induction of conserved genes encoding antioxidant functions is dependent on the transcription factors CgYap1 and CgSkn7 which cooperate for promoter recognition. Superoxide stress resistance of C. glabrata is provided by superoxide dismutase CgSod1, which is not dependent on CgYap1/Skn7. Only double mutants lacking both CgSod1 and CgYap1 were efficiently killed by primary mouse macrophages. Our results suggest that in C. glabrata the regulation of key genes providing stress protection is adopted to meet a host-pathogen situation.

Recovery of Candida dubliniensis and other Candida species from the oral cavity of subjects with periodontitis who had well-controlled and poorly controlled type 2 diabetes: a pilot study

The goal of this study was to determine the prevalence of Candida dubliniensis and other Candida species from saliva samples and from subgingival plaque samples at periodontally healthy and periodontally diseased sites in subjects who had type 2 diabetes and periodontitis. Saliva and subgingival samples were obtained from 30 subjects with periodontitis: 15 with poorly controlled and 15 with well-controlled type 2 diabetes. Samples were analyzed for the presence of C. dubliniensis and other Candida species. Among subjects with poorly controlled diabetes, 53% were positive for C. albicans, 20% for C. glabrata, 6% for C. tropicalis, and 6% for C. parapsilosis. Among well-controlled subjects, 33% were positive for C. albicans and 13% for C. glabrata; none had C. tropicalis or C. parapsilosis. No samples were positive for C. dubliniensis in either group of subjects.

Mutational analysis of flucytosine resistance in Candida glabrata

The antifungal flucytosine (5-fluorocytosine [5FC]) is a prodrug metabolized to its toxic form, 5-fluorouracil (5FU), only by organisms expressing cytosine deaminase. One such organism is Candida glabrata, which has emerged as the second most common agent of bloodstream and mucosal candidiasis. This emergence has been attributed to the high rate at which C. glabrata develops resistance to azole antifungals. As an oral agent, 5FC represents an attractive alternative or complement to azoles; however, the frequency of 5FC resistance mutations and the mechanisms by which these mutations confer resistance have been explored only minimally. On RPMI 1640 medium containing 1 μg/ml 5FC (32-fold above the MIC, but less than 1/10 of typical serum levels), resistant mutants occurred at a relatively low frequency (2 × 10⁻⁷). Three of six mutants characterized were 5FU cross-resistant, suggesting a mutation downstream of the Fcy1 gene (cytosine deaminase), which was confirmed by sequence analysis of the Fur1 gene (uracil phosphoribosyl transferase). The remaining three mutants had Fcy1 mutations. To ascertain the effects of 5FC resistance mutations on enzyme function, mutants were isolated in ura3 strains. Three of seven mutants harbored Fcy1 mutations and failed to grow in uridine-free, cytosine-supplemented medium, consistent with inactive Fcy1. The remainder grew in this medium and had wild-type Fcy1; further analysis revealed these to be mutated in the Fcy2L homolog of S. cerevisiae Fcy2 (purine-cytosine transporter). Based on this analysis, we characterized three 5FC-resistant clinical isolates, and mutations were identified in Fur1 and Fcy1. These data provide a framework for understanding 5FC resistance in C. glabrata and potentially in other fungal pathogens.

Epithelial cells and innate antifungal defense

The human pathogenic fungus Candida albicans is the predominant cause of both superficial and invasive forms of candidiasis. Clinical observations indicate that mucocutaneous Candida infections are commonly associated with defective cell-mediated immune responses. The importance of the innate immune system as a first-line defense against pathogenic challenge has long been recognized. Over the last decade, many key molecules mediating innate host defense have been identified. Central to these developments is the discovery of pattern recognition receptors such as Toll-like receptors and C-type lectin-receptors that induce innate immune responses and also modulate cellular and humoral adaptive immunity during Candida infections. Although a large amount of information is now available in systemic infections, little is known about localized infections. We address the most relevant pattern recognition receptors and their signaling mechanisms in oral epithelial cells, to gain a better understanding of their contributions to antifungal innate immunity.

Inhibition of electron transport chain assembly and function promotes photodynamic killing of Candida

Respiratory deficiency increases the sensitivity of the pathogenic fungi Candida albicans and Candida glabrata to oxidative stress induced by photodynamic therapy (PDT) sensitized by the cationic porphyrin meso-tetra (N-methyl-4-pyridyl) porphine tetra tosylate (TMP-1363). Since disruption of electron transport chain (ETC) function increases intracellular levels of reactive oxygen species in yeast, we determined whether interference with ETC assembly or function increased sensitivity to TMP-1363-PDT in C. albicans, C. glabrata and the non-pathogenic yeast Saccharomyces cerevisiae. Metabolic inhibitor antimycin A and defined genetic mutants were used to identify ETC components that contribute to the sensitivity to PDT. Inhibition of cytochrome bc(1) (Complex III) with antimycin A increases mitochondrial levels of reactive oxygen species. PDT performed following pre-treatment with antimycin A reduced colony forming units (CFU) of C. albicans and C. glabrata by approximately two orders of magnitude relative to PDT alone. A S. cerevisiae mitochondrial glutaredoxin grx5 mutant, defective in assembly of Fe-S clusters critical for Complex III function, displayed increased sensitivity to PDT. Furthermore, C. glabrata and S.cerevisiae mutants in cytochrome c oxidase (Complex IV) synthesis and assembly were also significantly more sensitive to PDT. These included suv3, encoding an ATP-dependent RNA helicase critical for maturation of cytochrome c oxidase subunit transcripts, and pet117, encoding an essential cytochrome c oxidase assembly factor. Following PDT, the reduction in CFU of these mutants was one to two orders of magnitude greater than in their respective parental strains. The data demonstrate that selective inhibition of ETC Complexes III and IV significantly increases the sensitivity of C. albicans, C. glabrata and S. cerevisiae to PDT sensitized with TMP-1363.

Treatment strategies for oropharyngeal candidiasis

BACKGROUND

Oropharyngeal candidiasis (OPC) is a common oral disease that may cause oral symptoms, lead to regional infection (e.g., esophageal candidiasis) and increase the risk of systemic fungal infection in the compromised host.

OBJECTIVE

Critical review of the literature of prevention and therapy.

METHODS

The literature was reviewed using PubMed, and specific keywords from the MeSH Database were used.

RESULTS/CONCLUSION

Management of OPC requires that the underlying risk factors of infection be diagnosed and managed whenever possible. Antimicrobials may be provided as topical or systemic therapy. Topical therapies may provide effective management for candidiasis in the non-compromised host and increase the control of colonization in the compromised host. Advances in prevention and management include new agents and improved mechanisms of topical drug delivery.

Effect of amine fluoride-stannous fluoride preparations on oral yeasts in the elderly: a randomised placebo-controlled trial

OBJECTIVES

Oral yeast infections are an emerging problem among medically compromised and frail elderly. Antifungal drug resistance is also increasing because of an increase in non-albicans Candida strains in these populations. We therefore set out to study, in the randomised-controlled trial setting if the use of a topical amine fluoride-stannous fluoride combination (AmF-SnF2) could control oral Candida growth in the elderly. The hypothesis was based on earlier findings showing that in vitro this combination had antifungal efficacy.

METHODS

A total of 194 nursing home residents were randomised to receive either the test mouth rinse and toothpaste or a placebo twice daily for 8 months. Of these, 136 completed the trial. Saliva samples were taken using the oral rinse method, cultivated and the strain level identified with routine microbial methods. Compliance and use of preparations was assessed by a nurse.

RESULTS

Significantly at the end of the trial, less mucosal lesions were observed in the test group in comparison to controls. Total bacterial count decreased in both the groups during the trial. Candida albicans was the most prevalent strain detected both at baseline and 8 months later. Only a few subjects carried non-albicans strains. The AmF-SnF2 did not significantly affect mean oral Candida counts, but median Candida counts were reduced in the AmF-SnF2 group while an increase was seen in the placebo group. However, the differences observed were not statistically significant. Compliance among the regular elderly users slightly increased during the trial for both the groups.

CONCLUSION

The number of subjects with high Candida counts decreased in the AmF-SnF2 group. Hence, the fluoride combination might be useful as a support therapy for oral candidiasis. Prevalence of non-albicans Candida strains was low in this population.

Autophagy supports Candida glabrata survival during phagocytosis

The opportunistic human fungal pathogen Candida glabrata is confronted with phagocytic cells of the host defence system. Survival of internalized cells is thought to contribute to successful dissemination. We investigated the reaction of engulfed C. glabrata cells using fluorescent protein fusions of the transcription factors CgYap1 and CgMig1 and catalase CgCta1. The expression level and peroxisomal localization of catalase was used to monitor the metabolic and stress status of internalized C. glabrata cells. These reporters revealed that the phagocytosed C. glabrata cells were exposed to transient oxidative stress and starved for carbon source. Cells trapped within macrophages increased their peroxisome numbers indicating a metabolic switch. Prolonged phagocytosis caused a pexophagy-mediated decline in peroxisome numbers. Autophagy, and in particular pexophagy, contributed to survival of C. glabrata during engulfment. Mutants lacking CgATG11 or CgATG17, genes required for pexophagy and non-selective autophagy, respectively, displayed reduced survival rates. Furthermore, both CgAtg11 and CgAtg17 contribute to survival, since the double mutant was highly sensitive to engulfment. Inhibition of peroxisome formation by deletion of CgPEX3 partially restored viability of CgATG11 deletion mutants during engulfment. This suggests that peroxisome formation and maintenance might sequester resources required for optimal survival. Mobilization of intracellular resources via autophagy is an important virulence factor that supports the viability of C. glabrata in the phagosomal compartment of infected innate immune cells.

Variation in susceptibility of bloodstream isolates of Candida glabrata to fluconazole according to patient age and geographic location in the United States in 2001 to 2007

We examined the susceptibilities to fluconazole of 642 bloodstream infection (BSI) isolates of Candida glabrata and grouped the isolates by patient age and geographic location within the United States. Susceptibility of C. glabrata to fluconazole was lowest in the northeast region (46%) and was highest in the west (76%). The frequencies of isolation and of fluconazole resistance among C. glabrata BSI isolates were higher in the present study (years 2001 to 2007) than in a previous study conducted from 1992 to 2001. Whereas the frequency of C. glabrata increased with patient age, the rate of fluconazole resistance declined. The oldest age group (> or = 80 years) had the highest proportion of BSI isolates that were C. glabrata (32%) and the lowest rate of fluconazole resistance (5%).

Oral Candida infection and colonization in solid organ transplant recipients

INTRODUCTION

Oral Candida carriage and infection have been reported to be associated with a greater risk for systemic infection in transplant recipients; however, a systematic analysis of the oral Candida titers and species has not been previously conducted. The objectives of this study were to determine the prevalence of oropharyngeal candidiasis, the oral carrier status, Candida titers and species in this population.

METHODS

Ninety kidney and heart transplant subjects and 72 age-matched healthy controls were included. Swabs from the oral mucosa and a standardized amount of unstimulated saliva were plated on Chromagar Candida, and colony-forming units per millilitre were calculated. Initial speciation was based on colony color and was confirmed by standard germ tube, biotyping, or polymerase chain reaction assays.

RESULTS

Infection with C. albicans was detected in seven transplant subjects and none of the controls. The transplant group had significantly higher oral Candida titers than the control group. There were no statistically significant relationships between the dose or type of immunosuppressants and oral Candida titers or infection. A significantly higher percentage of transplant subjects were colonized by more than one species, compared with control subjects. The most frequent species combination in transplant subjects was C. albicans and C. glabrata. C. glabrata was isolated from 13.5% of transplant carriers and none of the controls.

CONCLUSIONS

Increased oral Candida infection and carriage titers were found in the transplant population. Although the majority of transplant patients were colonized by C. albicans, C. glabrata appears to emerge as the second most prevalent species.

Molecular and phenotypic analysis of mutations causing anionic phospholipid deficiency in closely related yeast species

The pel1 mutation in Saccharomyces cerevisiae and the Cgpgs1Delta mutation in Candida glabrata result in deficiency of mitochondrial phosphatidylglycerolphosphate synthase and lack of two anionic phospholipids, phosphatidylglycerol and cardiolipin. DNA sequence analysis of the PCR-amplified pel1 mutant allele revealed that the pel1 mutation resulted from a single amino-acid substitution (Glu(463)Lys) in the C-terminal part of encoded enzyme. The CgPGS1 gene cloned in a centromeric pFL38 vector functionally complemented the pel1 mutation in S. cerevisiae. Likewise, the ScPGS1 gene cloned in pCgACU5 plasmid fully complemented the Cgpgs1Delta mutation in C. glabrata. This mutation increased the cell surface hydrophobicity and decreased biofilm formation. These results support a close evolutionary relatedness of S. cerevisiae and C. glabrata and point to the relationship between expression of virulence factors and anionic phospholipid deficiency in pathogenic C. glabrata.

Molecular and Cellular Mechanisms That Lead to Candida Biofilm Formation

Fungal infections in the oral cavity are mainly caused by C. albicans, but other Candida species are also frequently identified. They are increasing in prevalence, especially in denture-wearers and aging people, and may lead to invasive infections, which have a high mortality rate. Attachment to mucosal tissues and to abiotic surfaces and the formation of biofilms are crucial steps for Candida survival and proliferation in the oral cavity. Candida species possess a wide arsenal of glycoproteins located at the exterior side of the cell wall, many of which play a determining role in these steps. In addition, C. albicans secretes signaling molecules that inhibit the yeast-to-hypha transition and biofilm formation. In vivo, Candida species are members of mixed biofilms, and subject to various antagonistic and synergistic interactions, which are beginning to be explored. We believe that these new insights will allow for more efficacious treatments of fungal oral infections. For example, the use of signaling molecules that inhibit biofilm formation should be considered. In addition, cell-wall biosynthetic enzymes, wall cross-linking enzymes, and wall proteins, which include adhesins, proteins involved in biofilm formation, fungal-bacterial interactions, and competition for surface colonization sites, offer a wide range of potential targets for therapeutic intervention.

Development of Candida-associated denture stomatitis: new insights

Despite therapeutic progress, opportunistic oral fungal infectious diseases have increased in prevalence, especially in denture wearers. The combination of entrapment of yeast cells in irregularities in denture-base and denture-relining materials, poor oral hygiene and several systemic factors is the most probable cause for the onset of this infectious disease. Hence colonization and growth on prostheses by Candida species are of clinical importance. The purpose of this review is to critically discuss several key factors controlling the adhesion of Candida species which are relevant to denture-associated stomatitis. Although there is some consensus on the role of surface properties, studies on several other factors, as the use of denture liners, salivary properties and yeast-bacterial interactions, have shown contradictory findings. A comprehensive fundamental understanding is hampered by conflicting findings due to the large variations in experimental protocols, while other factors have never been thoroughly studied. Surface free energy and surface roughness control the initial adherence, but temporal changes have not been reported. Neither have in vivo studies shown if the substratum type is critical in dictating biofilm accumulation during longer periods in the oral environment. The contribution of saliva is unclear due to factors like variations in its collection and handling. Initial findings have disclosed that also bacteria are crucial for the successful establishment of Candida in biofilms, but the clinical significance of this observation is yet to be confirmed. In conclusion, there is a need to standardize experimental procedures, to bridge the gap between laboratory and in vivo methodologies and findings and – in general – to thoroughly investigate the factors that modulate the initial attachment and subsequent colonization of denture-base materials and the oral mucosa of patients subjected to Candida infections. Information on how these factors can be controlled is required and this may help to prevent the disease. The societal impact of such information is significant given the magnitude of the candidosis problem worldwide.