Replacement of Candida albicans with C. dubliniensis in human immunodeficiency virus-infected patients with oropharyngeal candidiasis treated with fluconazole

Raman Spectroscopy of Oral Candida Species: Molecular-Scale Analyses, Chemometrics, and Barcode Identification

Oral candidiasis, a common opportunistic infection of the oral cavity, is mainly caused by the following four Candida species (in decreasing incidence rate): Candida albicans, Candida glabrata, Candida tropicalis, and Candida krusei. This study offers in-depth Raman spectroscopy analyses of these species and proposes procedures for an accurate and rapid identification of oral yeast species. We first obtained average spectra for different Candida species and systematically analyzed them in order to decode structural differences among species at the molecular scale. Then, we searched for a statistical validation through a chemometric method based on principal component analysis (PCA). This method was found only partially capable to mechanistically distinguish among Candida species. We thus proposed a new Raman barcoding approach based on an algorithm that converts spectrally deconvoluted Raman sub-bands into barcodes. Barcode-assisted Raman analyses could enable on-site identification in nearly real-time, thus implementing preventive oral control, enabling prompt selection of the most effective drug, and increasing the probability to interrupt disease transmission.

Evaluation of various phenotypic methods for differentiation of Candida dubliniensis from Candida albicans

INTRODUCTION

Candida dubliniensis was first identified by Sullivan et al. (1995) in Dublin, Ireland. Its clinical significance is associated with development of fluconazole-resistance and invasive diseases in immunocompromised hosts. C. dubliniensis share many features with C. albicans so has been overlooked and misidentified for a long time.

AIMS

Evaluation of various phenotypic tests with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) as a gold standard to find out the best method/methods for identifying C. dubliniensis.

MATERIALS AND METHODS

First PCR-RFLP was performed on 186C. albicans and 14C. dubliniensis strains and then five phenotypic tests were performed simultaneously on all the strains.

RESULTS

The results of salt tolerance test at 48 h, colony color on HiCrome candida differential agar (HCDA) at 72 h, heat tolerance test at 48 h, xylose assimilation using discs at 72 h and growth on xylose based agar medium (XAM) at 48 h are completely concordant with PCR-RFLP. Colony color on Tobacco agar could differentiate accurately 100% test strains while peripheral hyphal fringes and chlamydosporulation on this agar was seen in only 86% and 87% respectively. Our routine methods proved to be cost effective than PCR-RFLP but the turnaround time was same or more than PCR-RFLP.

CONCLUSION

For routine identification of C. dubliniensis we recommend use of colony color on HCDA and growth on XAM as simple, reliable and inexpensive method.

A COVID-19 Case Complicated by Candida dubliniensis and Klebsiella pneumoniae-Carbapenem-Resistant Enterobacteriaceae

There has been increasing evidence of co-infections with coronavirus disease 2019 (COVID-19) pneumonia, which increases the severity of the disease. Organisms such as Klebsiella pneumoniae and Streptococcus pneumoniae have been previously isolated. We present a case of a COVID-19 patient treated with baricitinib and dexamethasone who later developed Klebsiella pneumoniae-carbapenem-resistant Enterobacteriaceae (CRE) and Candida dubliniensis bloodstream infections, treated with meropenem/vaborbactam and micafungin, respectively. These infections are exceedingly rare and are mostly reported in immunosuppressed patients. The finding of these bloodstream infections raises concerns on the cause of immunosuppression in this patient infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) treated with baricitinib and dexamethasone. There has been no report so far of COVID-19 associated with these co-infections.

DNA microsatellite genotyping of potentially pathogenic Candida albicans and C. dubliniensis isolated from the oral cavity and dental prostheses

This study investigated the incidence, genetic diversity, antifungal sensitivity, and virulence of Candida albicans and C. dubliniensis isolated from subjects using dental prostheses and subjects clinically indicated for the first prosthetic rehabilitation. Subjects were divided into four groups and samples were collected twice: at first rehabilitation by removable partial (A) and total (C) dental prostheses, and replacement of the removable partial (B) and total (D) prostheses. Yeasts were genotyped using DNA microsatellite markers. Microbiological methods were used to screen for azole antifungal resistance and exoenzyme production. In the initial sampling, oral colonization by Candida was observed in 31 (53.4%) subjects in groups A (33.3%), B (68.2%), and D (65%); 20 (47.6%) subjects displayed colonization of prostheses: groups B (50%) and D (45%). The second sampling (±30 days) revealed Candida in 2 (3.4%: oral cavity) and 4 (6.9%: prosthetic) subjects from group B. C. albicans and C. dubliniensis displayed both polyclonal and monoclonal patterns of infection. Azole-resistant C. albicans and SAPs⁺ strains were prevalent. Related strains were found in one or several oral sites (mucosa and prosthesis), as well as intra- and inter-subject, -gender, -group, and -time of sampling. However, the patterns of clonality can be altered under dental care.

On Commensalism of Candida

Candida species are both opportunistic fungal pathogens and common members of the human mycobiome. Over the years, the main focus of the fungal field has been on understanding the pathogenic potential and disease manifestation of these organisms. Therefore, understanding of their commensal lifestyle, interactions with host epithelial barriers, and initial transition into pathogenesis is less developed. In this review, we will describe the current knowledge on the commensal lifestyle of these fungi, how they are able to adhere to and colonize host epithelial surfaces, compete with other members of the microbiota, and interact with the host immune response, as well as their transition into opportunistic pathogens by invading the gastrointestinal epithelium.

Candidiasis Causing Vocal Fold Leukoplakia: Review of Clinical and Pathological Results of 289 Cases With Vocal Fold Leukoplakia

Objective:

In laryngology practice, vocal fold leukoplakia is frequently evaluated by suspension laryngoscopy and biopsy examination upon the patient’s complaints of hoarseness and dysphonia. The purpose of the present study is to investigate and analyze risk factors, diagnosis, treatment, and follow-up results of cases with Candida leukoplakia.

Study Design:

Retrospective case control study.

Setting:

Tertiary medical center.

Subjects and Methods:

Patients with a diagnosis of vocal fold leukoplakia who underwent direct laryngoscopy and biopsy between 2007 and 2017 and diagnosed as candida or noncandida in their histopathology were assigned into 2 groups. Then they were compared in terms of their demographic characteristics, predisposing factors, diagnosis, treatment, and follow-up results.

Results:

Of the 289 vocal fold leukoplakia cases, 36 were candida, and 253 were noncandida. The mean age of the patients with Candida leukoplakia was 60.86 years. As for the age groups, the largest group (26.1%) was in the seventh decade ( P < .001). The use of inhaled corticosteroids was a significant risk factor ( P < .001). For their medical therapy, the patients were administered fluconazole 200 mg per day for 3 weeks, and the treatment yielded successful results in 91.66% of them. In 5 of the patients, candida leukoplakia and superficial epithelial dysplasia were observed, and no malignant transformation was observed during a mean follow-up of 28 ± 13 months.

Conclusion:

Candidiasis causing vocal fold leukoplakia is rare, and we report the findings of the largest published case series to date. Eliminating predisposing factors and administrating oral fluconazole 200 mg for 3 weeks are sufficient for medical treatment.

In Vitro Characterization of a Biaryl Amide Anti-virulence Compound Targeting Candida albicans Filamentation and Biofilm Formation

We have previously identified a small molecule compound, N-[3-(allyloxy)-phenyl]-4-methoxybenzamide (9029936), that exerts potent inhibitory activity against filamentation and biofilm formation by the Candida albicans SC5314 strain and represents a lead candidate for the development of anti-virulence approaches against C. albicans infections. Here we present data from a series of experiments to further characterize its in vitro activity and drug-like characteristics. We demonstrate the activity of this compound against a panel of C. albicans clinical isolates, including several displaying resistance to current antifungals; as well as against a set of C. albicans gain of function strains in key transcriptional regulators of antifungal drug resistance. The compound also inhibits filamentation and biofilm formation in the closely related species C. dubliniensis, but not C. glabrata or C. tropicalis. Combinatorial studies reveal the potential of compound 9029936 to be used together with currently available conventional antifungals. Results of serial passage experiments indicate that repeated exposure to this compound does not elicit resistance. Viability staining of C. albicans in the presence of high concentrations of compound 9029936 confirms that the compound is not toxic to fungal cells, and cytological staining using image flow cytometry analysis reveals that treatment with the lead compound affects hyphal length, with additional effects on cell wall and integrity of the membrane system. In vitro pharmacological profiling provides further evidence that the lead compound displays a safe profile, underscoring its excellent “drug-like” characteristics. Altogether these results confirm the potential of this compound to be further developed as a true anti-virulence agent for the treatment of C. albicans infections, including those refractory to treatment with conventional antifungal agents.

Fluconazole impacts the extracellular matrix of fluconazole-susceptible and -resistant Candida albicans and Candida glabrata biofilms

Background: Fluconazole (FLZ) is a drug commonly used for the treatment of Candida infections. However, β-glucans in the extracellular matrices (ECMs) hinder FLZ penetration into Candida biofilms, while extracellular DNA (eDNA) contributes to the biofilm architecture and resistance. Methods: This study characterized biofilms of FLZ-sensitive (S) and -resistant (R) Candida albicans and Candida glabrata in the presence or absence of FLZ focusing on the ECM traits. Biofilms of C. albicans American Type Culture Collection (ATCC) 90028 (CaS), C. albicans ATCC 96901 (CaR), C. glabrata ATCC 2001 (CgS), and C. glabrata ATCC 200918 (CgR) were grown in RPMI medium with or without FLZ at 5× the minimum inhibitory concentration (37°C/48 h). Biofilms were assessed by colony-forming unit (CFU)/mL, biomass, and ECM components (alkali-soluble polysaccharides [ASP], water-soluble polysaccharides [WSP], eDNA, and proteins). Scanning electron microscopy (SEM) was also performed. Data were analyzed by parametric and nonparametric tests (α  =  0.05). Results: In biofilms, FLZ reduced the CFU/mL of all strains (p < 0.001), except for CaS (p = 0.937). However, the ASP quantity in CaS was significantly reduced by FLZ (p = 0.034), while the drug had no effect on the ASP levels in other strains (p > 0.05). Total biomasses and WSP were significantly reduced by FLZ in the ECM of all yeasts (p < 0.001), but levels of eDNA and proteins were unaffected (p > 0.05). FLZ affected the cell morphology and biofilm structure by hindering hyphae formation in CaS and CaR biofilms, by decreasing the number of cells in CgS and CgR biofilms, and by yielding sparsely spaced cell agglomerates on the substrate. Conclusion: FLZ impacts biofilms of C. albicans and C. glabrata as evident by reduced biomass. This reduced biomass coincided with lowered cell numbers and quantity of WSPs. Hyphal production by C. albicans was also reduced.

The severity of denture stomatitis as related to risk factors and different Candida spp

OBJECTIVES

1) To select patients with Candida-related denture stomatitis (DS) and to study possible risk factors associated with DS, 2) to evaluate the severity of DS according to Newton's classification, and 3) to investigate the association between the presence of non-albicans Candida spp. (NAC) or mixed Candida spp. and the severity of DS.

STUDY DESIGN

Eighty-two patients with Candida-positive DS have undergone 1) filling in the interview questionnaire, 2) clinical examination, and 3) microbiologic examination.

RESULTS

A total of 113 Candida spp. isolates were obtained from Candida-positive DS patients: C. albicans (as a single species) in 47/82 (57%) patients (study group A [SG_A]) and NAC/mixed Candida spp. in 35/82 (43%) patients (SG_B). Univariate logistic regression analysis showed that older age, longer age of the mandibular denture, and ex-smoker status were associated with SG_A. A multivariate model revealed no significant predictor of DS severity. Patients from SG_A were 3 times as likely to have DS type I, while patients from SG_B were 4.9 times as likely to have DS type III.

CONCLUSIONS

Our results show the association between type III of DS (by Newton's classification) and the presence of NAC or mixed Candida spp. in denture wearers.

Laboratory-Based Investigation of Denture Sonication Method in Patients with Candida-Associated Denture Stomatitis

PURPOSE

Denture stomatitis (DS) is a disease characterized by inflammation and erythema of the oral mucosa areas covered by the denture. Multifactorial etiological factors contribute to DS, but it seems that Candida plays the key role. The aim of the study was to evaluate the denture sonication method to: (i) increase the possibility of diagnosing patients with Candida-associated DS; (ii) detect and identify the mixed Candida spp., and (iii) determine the Candida colony forming units (CFU) and its possible relationship with DS severity, based on Newton's classification.

MATERIALS AND METHODS

The cross-sectional study conducted at the Clinic for Dental Prosthetics, Belgrade (Serbia) from June 2013 to December 2014 enrolled edentulous patients with dentures (n = 250). Patients without DS (n = 20) were the control group (CG). The patients' data were collected, and patients with DS (study group/SG) were selected and divided into SG Candida+ and SG Candida-. Based on severity of DS, the SG patients were classified in 3 groups (Newton's classification). Four sampling methods were applied to detect patients with Candida-associated DS: mucosa swab, denture swab, oral rinse, and denture sonication method. The sensitivity and specificity of denture sonication method were shown using the receiver operating characteristic (ROC) curve and the area under the curve (AUC).

RESULTS

In 97 (38.8%), out of 250 clinically examined patients, DS was diagnosed. In 82 (84.5%), out of 97 mycologically examined patients, Candida-associated DS was detected when denture sonication method was applied. Additionally, using the denture sonication method we observed: (i) the largest number of Candida positive patients compared to other sampling methods (p < 0.0001); (ii) the highest number of Candida CFU/ml (10⁵ ), and (iii) the possibility to detect mixed Candida cultures. The largest number of patients with Candida-associated DS showed type II (60%) DS, followed by type I (21%), and type III (19%) DS.

CONCLUSION

The denture sonication method is easy, accurate, and sensitive, and increases the possibility of diagnosing patients with Candida-associated DS. Additionally, yeast quantification, mixed Candida spp., and non-albicans Candida were detectable when cultivation on Candida CHROMagar was performed. It was not possible using conventional methods, such as swab or oral rinse.

Oropharyngeal candidiasis prevalence among HIV-infected patients at the teaching hospital of Treichville (Abidjan, Côte d'Ivoire)

AIM OF THE STUDY

The aim of this study was to determine the mycological profile of oropharyngeal candidiasis among HIV-infected patients from Internal Medicine, Infectious and Tropical Diseases, and Pneumo-Phthisiology Diseases departments of the Teaching Hospital of Treichville in Abidjan, Côte d'Ivoire.

PATIENTS AND METHODS

This was a cross-sectional study carried out on patients with lesions suggestive of oropharyngeal candidiasis from October 2010 to April 2011. Oral swabs were cultured, and Candida species were identified using a germ tube test, a chlamydospore formation assay, and the API 20C system.

RESULTS

A total of 286 patients were included, among whom 99.1% were infected with HIV. The prevalence of oropharyngeal candidiasis was 79.4% (CI_95%=74.4-83.8). Five different species of Candida were identified, with the predominant species being Candida albicans (95.2%). Most affected patients were female (54.6%, P<0.0001) between the ages of 30 and 45 (78.4%, P<0.0001). The most lesion types observed were thrush (87.8%). Patients infected with HIV1 (95.6%), with a primary school level of education (52.8%), under antiretroviral therapy (88.5%) and with tuberculosis as an associated pathology (62.5%) were the most commonly affected. Patients were mostly under ART first line treatment (86.4%) and at the beginning of the treatment (86.4%).

CONCLUSION

Oropharyngeal candidiasis is frequent among HIV-infected patients. Better and early management of this vulnerable population should allow for a reduction in the high prevalence observed.

Antifungal Drug Susceptibility of Candida Species Isolated from HIV-Positive Patients Recruited at a Public Hospital in São Luís, Maranhão, Brazil

Oropharyngeal candidiasis is the most common fungal infection in hospitalized patients with acquired immune deficiency syndrome (AIDS). Its progression results in invasive infections, which are a significant cause of morbidity and mortality. This study aimed to quickly and accurately identify Candida spp. from oral mucosa of AIDS patients recruited at Presidente Vargas Hospital, in São Luís city, Brazil and to evaluate the sensitivity profile of these fungi to antifungals by using an automated system. Isolates were collected from oropharyngeal mucosa of 52 hospitalized AIDS patients, under anti-viral and antifungal therapies. Patients were included in research if they were HIV-positive, above 18 years of age and after obtaining their written consent. CHROMagar^®Candida and the automated ViteK-2^®system were used to isolate and identify Candida spp., respectively. Antifungal susceptibility testing was performed using the ViteK-2^®system, complemented with the Etest^®, using the drugs amphotericin B, fluconazole, flucytosine, and voriconazole. Oropharyngeal candidiasis had a high prevalence in these hospitalized AIDS patients (83%), and the most prevalent species was Candida albicans (56%). Antifungal susceptibility test showed that 64.7% of the Candida spp. were susceptible, 11.8% were dose-dependent sensitive, and 23.5% were resistant. All the Candida krusei and Candida famata isolates and two of Candida glabrata were resistant to fluconazole. Most of AIDS patients presented oropharyngeal candidiasis and C. albicans was the most frequently isolated species. The results showed high variability in resistance among isolated species and indicates the need to identify the Candida spp. involved in the infection and the need to test antifungal susceptibility as a guide in drug therapy in patients hospitalized with AIDS. This is the first relate about AIDS patients monitoring in a public hospital in São Luís concerning the precise identification and establishing of antifungal profile of Candida spp..

Usefulness of CHROMagar Candida Medium, Biochemical Methods--API ID32C and VITEK 2 Compact and Two MALDI-TOF MS Systems for Candida spp. Identification

This study was conducted to compare of the yeasts identification results obtained with two new systems using the MALDI-TOF MS technique with the ones obtained using the routine identification methods of Candida spp. in clinical microbiology laboratories. All 124 Candida spp. isolates were recovered from the routine examination of clinical specimens in microbiological laboratories and collected in the Centre of Quality Control in Microbiology in Warsaw (Poland). Our findings confirm the high agreement (98%) of fungal identification using the standard, biochemistry laboratory methods and mass spectrometry technique.

Gastrointestinal Infections

Gastrointestinal infections in the immunocompromised host are caused by the common bacterial, viral, fungal, and parasitic agents that also cause infections in the immunocompetent host. Of special consideration is that immunocompromised patients may be at increased risk for infection or disease severity and by pathogens not seen in the competent host. This chapter reviews the various agents, risk factors, and diagnostic approaches to detect gastrointestinal infections in this patient population.

Species distribution and susceptibility profile to fluconazole, voriconazole and MXP-4509 of 551 clinical yeast isolates from a Romanian multi-centre study

This is the first multi-centre study regarding yeast infections in Romania. The aim was to determine the aetiological spectrum and susceptibility pattern to fluconazole, voriconazole and the novel compound MXP-4509. The 551 isolates were identified using routine laboratory methods, matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and DNA sequence analysis. Susceptibility testing was performed using the European Committee for Antimicrobial Susceptibility Testing (EUCAST) method and breakpoints. The yeasts originated from superficial infections (SUP, 51.5 %), bloodstream infections (BSI, 31.6 %) and deep-seated infections (DEEP, 16.9 %), from patients of all ages. Nine genera and 30 species were identified. The 20 Candida species accounted for 94.6 % of all isolates. C. albicans was the overall leading pathogen (50.5 %). Lodderomyces elongisporus is reported for the first time as a fungaemia cause in Europe. C. glabrata and Saccharomyces cerevisiae, as well as the non-Candida spp. and non-albicans Candida spp. groups, showed decreased fluconazole susceptibility (<75 %). The overall fluconazole resistance was 10.2 %. C. krusei accounted for 27 of the 56 fluconazole-resistant isolates. The overall voriconazole resistance was 2.5 % and was due mainly to C. glabrata and C. tropicalis isolates. Fluconazole resistance rates for the three categories of infection were similar to the overall value; voriconazole resistance rates differed: 4 % for BSI, 3.2 % for DEEP and 1.4 % for SUP. The antifungal activity of MXP-4509 was superior to voriconazole against C. glabrata and many fluconazole-resistant isolates. There was a large percentage of non-albicans Candida isolates. A large part of the high fluconazole resistance was not acquired but intrinsic, resulting from the high percentage of C. krusei.

Susceptibility profile of a Brazilian yeast stock collection of Candida species isolated from subjects with Candida-associated denture stomatitis with or without diabetes

OBJECTIVE

This study investigated the susceptibility of 198 clinical isolates of Candida species against caspofungin, amphotericin B, itraconazole, and fluconazole.

STUDY DESIGN

Suspensions of the microorganisms were spread on Roswell Park Memorial Institute (RPMI) agar plates. Etest strips were placed on the plates, and the minimal inhibitory concentration (MIC) was read after incubation (48 h at 37 °C). Data were analyzed by a factorial analysis of variance and a 2 × 2 post hoc test (α = .05).

RESULTS

C glabrata showed the highest MIC values (P < .001) against caspofungin, itraconazole, and fluconazole. For amphotericin B, the MIC values of C tropicalis and C glabrata (P = .0521) were higher than those of C albicans (P < .001). Itraconazole was the least effective antifungal; 93.3% of the C glabrata isolates, 3.3% of the C albicans, and 1.3% of the C tropicalis were resistant. All microorganisms were susceptible to caspofungin and amphotericin B.

CONCLUSIONS

Caspofungin and amphotericin B should be recommended as an effective alternative for the management of oral Candida infections when treatment with topical or other systemic drugs has definitely failed.

Oral candidosis in lichen planus: the diagnostic approach is of major therapeutic importance

OBJECTIVES

Candida albicans is the most common fungal pathogen in humans, but other Candida species cause candidosis. Candida species display significant differences in their susceptibility to antimycotic drugs. Patients with symptomatic or erythematous oral lichen planus (OLP) commonly have Candida infection requiring correct identification of Candida species in order to initiate adequate antimycotic therapy. Therefore, conventional cytosmear and culture tests were compared with genetic diagnostics on oral rinse followed by agar culture and material collected by cytobrush from OLP patient mucosal lesion.

METHODS

The genetic approach was validated on a reference panel of 60 well-defined unrelated fungal species. The study included 37 OLP patients. Oral candidosis (OC) was established based on clinical signs of OC and/or oral mucosal symptoms and at least one hypha in lesional cytosmear. Antimycotic treatment was initiated after OC diagnosis, and symptomatic treatment was initiated in no-candidosis situations.

RESULTS

The composition of Candida species in oral rinse/culture test was different from that of lesional cytobrush sampling as more non-albicans species were detected by the latter. Unexpectedly, Candida dubliniensis was found to be overrepresented among patients with a history of antimycotic treatment indicating unintentional iatrogen selection. Of the 22 OLP patients receiving treatment, 27% of these should have been offered alternative therapy based on the improved diagnostic approach.

CONCLUSION

This study highlights the importance of lesional sampling in OLP patients with suspected OC.

CLINICAL RELEVANCE

Correct fungal identification is critical in order to initiate adequate antimycotic therapy, thus minimizing iatrogen selection of non-albicans species.

Candida dubliniensis: an appraisal of its clinical significance as a bloodstream pathogen

A nine-year prospective study (2002–2010) on the prevalence of Candida dubliniensis among Candida bloodstream isolates is presented. The germ tube positive isolates were provisionally identified as C. dubliniensis by presence of fringed and rough colonies on sunflower seed agar. Subsequently, their identity was confirmed by Vitek2 Yeast identification system and/or by amplification and sequencing of the ITS region of rDNA. In all, 368 isolates were identified as C. dubliniensis; 67.1% came from respiratory specimens, 11.7% from oral swabs, 9.2% from urine, 3.8% from blood, 2.7% from vaginal swabs and 5.4% from other sources. All C. dubliniensis isolates tested by Etest were susceptible to voriconazole and amphotericin B. Resistance to fluconazole (≥8 µg/ml) was observed in 2.5% of C. dubliniensis isolates, 7 of which occurred between 2008–2010. Of note was the diagnosis of C. dubliniensis candidemia in 14 patients, 11 of them occurring between 2008–2010. None of the bloodstream isolate was resistant to fluconazole, while a solitary isolate showed increased MIC to 5-flucytosine (>32 µg/ml) and belonged to genotype 4. A review of literature since 1999 revealed 28 additional cases of C. dubliniensis candidemia, and 167 isolates identified from blood cultures since 1982. In conclusion, this study highlights a greater role of C. dubliniensis in bloodstream infections than hitherto recognized.

Biofilm formation and adhesive/invasive properties of Candida dubliniensis in comparison with Candida albicans

Candida dubliniensis and Candida albicans are closely related spp. exhibiting differences in their virulence potency. This study compared clinical isolates of C. dubliniensis with C. albicans from HIV patients with oropharyngeal candidiasis (OPC) and standard strains in power to form biofilm and their adhesive and invasive properties. Members of both spp. were able to form strong biofilms. However, SEM microscopy confirmed that C. albicans undergoes the more effective yeast-to-hyphae transition than C. dubliniensis with prevalent yeast form and limited ability to form filaments. Kinetic patterns indicated that while the first 30 min are critical for sufficient attachment to a polystyrene surface, adhesion to human carcinoma cell lines (Caco-2 and TR 146) needs additional time with maximal saturation observed at 240 min for both spp. The invasion process was tested on 3D RHE (reconstituted human epithelium) with Caco-2 or TR 146 on the collagen surface. C. albicans rapidly produced hyphae that penetrated the tissue layer, demonstrating substantive invasion within 21 h. In contrast, C. dubliniensis attached to the tissue surface and proliferated, suggesting the formation of a biofilm-like structure. After 21 h, C. dubliniensis was able to penetrate the RHE layer and invade unusually, with a cluster of the yeast cells.

Are subinhibitory concentrations of antibiotics the only culprit of antibiotic resistance?

Evaluation of: Gullberg E, Cao S, Berg OG et al. Selection of resistant bacteria at very low antibiotic concentrations. PLoS Pathog. 7(7), e1002158 (2011). Subinhibitory concentrations of antibiotics and antifungals promote resistance. Antibiotic consumption including hospital use, and country use, including patients self-medications is one of the major drivers of antibiotic or antifungal resistance. However, consumption of antibiotics should be distinguished between the hospital and community. Hospital consumption, poor hospital hygiene and intrahospital transfer have been determined as major risk factors for development of resistance. The correlation between resistance and consumption in the community is not so clear. Therefore consumption of antibiotics and antifungals alone cannot explain the selection of resistant bacterial and fungal mutants and other factors have to be investigated.

Cdr2p contributes to fluconazole resistance in Candida dubliniensis clinical isolates

The development of resistance to azole antifungals used in the treatment of fungal infections can be a serious medical problem. Here, we investigate the molecular mechanisms associated with reduced susceptibility to fluconazole in clinical isolates of Candida dubliniensis , showing evidence of the trailing growth phenomenon. The changes in membrane sterol composition were studied in the presence of subinhibitory fluconazole concentrations. Despite lanosterol and eburicol accumulating as the most prevalent sterols after fluconazole treatment, these ergosterol precursors still support growth of Candida isolates. The overexpression of ABC transporters was demonstrated by immunoblotting employing specific antibodies against Cdr1p and Cdr2p. The presence of a full-length 170 kDa protein Cdr1p was detected in two isolates, while a truncated form of Cdr1p with the molecular mass of 85 kDa was observed in isolate 966/3(2). Notably, Cdr2p was detected in this isolate, and the expression of this transporter was modulated by subinhibitory concentrations of fluconazole. These results suggest that C. dubliniensis can display the trailing growth phenomenon, and such isolates express similar molecular mechanisms like that of fluconazole-resistant isolates and can therefore be associated with recurrent infections.

Candida albicans or Candida dubliniensis?

Candida albicans is increasing as an opportunistic pathogen causing candidemia and candidiasis worldwide. In addition, other non-albicans Candida species are now also associated with pertinent infections. These include the closely related C. dubliniensis, which shares many phenotypic similarities with C. albicans. These similarities pose problems in the identification of isolates and have previously led to misidentification of these species. As a result, several identification techniques based on phenotypic and genotypic characteristics have been developed to differentiate between these Candida species. This review will focus on the similarities and differences between these two Candida species highlighting different identification methods and their advantages and disadvantages.

Mechanisms of antifungal drug resistance in Candida dubliniensis

Candida dubliniensis was first described in 1995 and is the most closely related species to the predominant human fungal pathogen Candida albicans. C. dubliniensis is significantly less prevalent and less pathogenic than C. albicans and is primarily associated with infections in HIV-infected individuals and other immunocompromised cohorts. The population structure of C. dubliniensis consists of three well-defined major clades and is significantly less diverse than C. albicans. The majority of C. dubliniensis isolates are susceptible to antifungal drugs commonly used to treat Candida infections. To date only two major patterns of antifungal drug resistance have been identified and the molecular mechanisms of these are very similar to the resistance mechanisms that have been described previously in C. albicans. However, significant differences are evident in the predominant antifungal drug mechanisms employed by C. dubliniensis, differences that reflect its more clonal nature, its lower prevalence and characteristics of its genome, the complete sequence of which has only recently been determined.

Longitudinal genotyping of Candida dubliniensis isolates reveals strain maintenance, microevolution, and the emergence of itraconazole resistance

We investigated the population structure of 208 Candida dubliniensis isolates obtained from 29 patients (25 human immunodeficiency virus [HIV] positive and 4 HIV negative) as part of a longitudinal study. The isolates were identified as C. dubliniensis by arbitrarily primed PCR (AP-PCR) and then genotyped using the Cd25 probe specific for C. dubliniensis. The majority of the isolates (55 of 58) were unique to individual patients, and more than one genotype was recovered from 15 of 29 patients. A total of 21 HIV-positive patients were sampled on more than one occasion (2 to 36 times). Sequential isolates recovered from these patients were all closely related, as demonstrated by hybridization with Cd25 and genotyping by PCR. Six patients were colonized by the same genotype of C. dubliniensis on repeated sampling, while strains exhibiting altered genotypes were recovered from 15 of 21 patients. The majority of these isolates demonstrated minor genetic alterations, i.e., microevolution, while one patient acquired an unrelated strain. The C. dubliniensis strains could not be separated into genetically distinct groups based on patient viral load, CD4 cell count, or oropharyngeal candidosis. However, C. dubliniensis isolates obtained from HIV-positive patients were more closely related than those recovered from HIV-negative patients. Approximately 8% (16 of 194) of isolates exhibited itraconazole resistance. Cross-resistance to fluconazole was only observed in one of these patients. Two patients harboring itraconazole-resistant isolates had not received any previous azole therapy. In conclusion, longitudinal genotyping of C. dubliniensis isolates from HIV-infected patients reveals that isolates from the same patient are generally closely related and may undergo microevolution. In addition, isolates may acquire itraconazole resistance, even in the absence of prior azole therapy.

Characterization of the oral fungal microbiome (mycobiome) in healthy individuals

The oral microbiome-organisms residing in the oral cavity and their collective genome-are critical components of health and disease. The fungal component of the oral microbiota has not been characterized. In this study, we used a novel multitag pyrosequencing approach to characterize fungi present in the oral cavity of 20 healthy individuals, using the pan-fungal internal transcribed spacer (ITS) primers. Our results revealed the "basal" oral mycobiome profile of the enrolled individuals, and showed that across all the samples studied, the oral cavity contained 74 culturable and 11 non-culturable fungal genera. Among these genera, 39 were present in only one person, 16 genera were present in two participants, and 5 genera were present in three people, while 15 genera (including non-culturable organisms) were present in >/=4 (20%) participants. Candida species were the most frequent (isolated from 75% of participants), followed by Cladosporium (65%), Aureobasidium, Saccharomycetales (50% for both), Aspergillus (35%), Fusarium (30%), and Cryptococcus (20%). Four of these predominant genera are known to be pathogenic in humans. The low-abundance genera may represent environmental fungi present in the oral cavity and could simply be spores inhaled from the air or material ingested with food. Among the culturable genera, 61 were represented by one species each, while 13 genera comprised between 2 and 6 different species; the total number of species identified were 101. The number of species in the oral cavity of each individual ranged between 9 and 23. Principal component (PCO) analysis of the obtained data set followed by sample clustering and UniFrac analysis revealed that White males and Asian males clustered differently from each other, whereas both Asian and White females clustered together. This is the first study that identified the "basal mycobiome" of healthy individuals, and provides the basis for a detailed characterization of the oral mycobiome in health and disease.

Characterization of the oral fungal microbiome (mycobiome) in healthy individuals

The oral microbiome–organisms residing in the oral cavity and their collective genome–are critical components of health and disease. The fungal component of the oral microbiota has not been characterized. In this study, we used a novel multitag pyrosequencing approach to characterize fungi present in the oral cavity of 20 healthy individuals, using the pan-fungal internal transcribed spacer (ITS) primers. Our results revealed the “basal” oral mycobiome profile of the enrolled individuals, and showed that across all the samples studied, the oral cavity contained 74 culturable and 11 non-culturable fungal genera. Among these genera, 39 were present in only one person, 16 genera were present in two participants, and 5 genera were present in three people, while 15 genera (including non-culturable organisms) were present in ≥4 (20%) participants. Candida species were the most frequent (isolated from 75% of participants), followed by Cladosporium (65%), Aureobasidium, Saccharomycetales (50% for both), Aspergillus (35%), Fusarium (30%), and Cryptococcus (20%). Four of these predominant genera are known to be pathogenic in humans. The low-abundance genera may represent environmental fungi present in the oral cavity and could simply be spores inhaled from the air or material ingested with food. Among the culturable genera, 61 were represented by one species each, while 13 genera comprised between 2 and 6 different species; the total number of species identified were 101. The number of species in the oral cavity of each individual ranged between 9 and 23. Principal component (PCO) analysis of the obtained data set followed by sample clustering and UniFrac analysis revealed that White males and Asian males clustered differently from each other, whereas both Asian and White females clustered together. This is the first study that identified the “basal mycobiome” of healthy individuals, and provides the basis for a detailed characterization of the oral mycobiome in health and disease.

We characterized the fungal microbiome (mycobiome) of the oral cavity in healthy individuals. Our results demonstrate that the fungal component of the oral microbiome is diverse as revealed by the presence of 74 culturable and 11 non-culturable fungal genera in the oral cavity. A total of 101 species were identified, with between 9 and 23 culturable species present in each person. Fifteen genera (which included four known pathogenic fungi and non-culturable organisms) were present in ≥20% of the tested samples; Candida species were the most frequently obtained genera, isolated from 75% of all study participants, followed by Cladosporium (65%), Aureobasidium, Saccharomycetales (50% for both), Aspergillus (35%), Fusarium (30%), and Cryptococcus (20%). The remaining fungi detected in the oral wash samples represent organisms likely originating from the environment. This is the first study that identified the “basal mycobiome” of healthy individuals, and provides the basis for a detailed characterization of the oral mycobiome in health and disease.

Role of posaconazole in the treatment of oropharyngeal candidiasis

Posaconazole is the newest azole antifungal approved by the US Food and Drug Administration, and possesses a broad spectrum of activity against numerous yeasts and filamentous fungi. It is available as an oral suspension and is generally well tolerated by patients, but gastrointestinal absorption is sometimes inadequate and remains a clinical concern in treating deep-seated infections. It is used routinely and effectively for the prophylaxis of invasive fungal infections in immunosuppressed hosts and is an effective treatment of oropharyngeal candidiasis, including azole-resistant disease.

Comparative transcript profiling of Candida albicans and Candida dubliniensis identifies SFL2, a C. albicans gene required for virulence in a reconstituted epithelial infection model

Candida albicans and Candida dubliniensis are closely related species displaying differences in virulence and genome content, therefore providing potential opportunities to identify novel C. albicans virulence genes. C. albicans gene arrays were used for comparative analysis of global gene expression in the two species in reconstituted human oral epithelium (RHE). C. albicans (SC5314) showed upregulation of hypha-specific and virulence genes within 30 min postinoculation, coinciding with rapid induction of filamentation and increased RHE damage. C. dubliniensis (CD36) showed no detectable upregulation of hypha-specific genes, grew as yeast, and caused limited RHE damage. Several genes absent or highly divergent in C. dubliniensis were upregulated in C. albicans. One such gene, SFL2 (orf19.3969), encoding a putative heat shock factor, was deleted in C. albicans. DeltaDeltasfl2 cells failed to filament under a range of hypha-inducing conditions and exhibited greatly reduced RHE damage, reversed by reintroduction of SFL2 into the DeltaDeltasfl2 strain. Moreover, SFL2 overexpression in C. albicans triggered hyphal morphogenesis. Although SFL2 deletion had no apparent effect on host survival in the murine model of systemic infection, DeltaDeltasfl2 strain-infected kidney tissues contained only yeast cells. These results suggest a role for SFL2 in morphogenesis and an indirect role in C. albicans pathogenesis in epithelial tissues.

Prevalence of Candida dubliniensis among cancer patients in Kuwait: a 5-year retrospective study

Despite close genetic and phenotypic relationship of Candida dubliniensis with Candida albicans, its role in human disease is mostly restricted to oral colonisation, particularly among HIV-infected patients. The prevalence of C. dubliniensis in association with other disease conditions has been infrequently reported. In this study, we present data on the prevalence of C. dubliniensis among yeast species isolated from cancer patients over a 5-year period. A total of 1445 yeast isolates recovered from respiratory specimens, blood, urine and oral swabs were analysed. Candida dubliniensis isolates were provisionally identified by phenotypic methods and their identity was further confirmed by species-specific amplification and/or sequencing of internally transcribed spacer region of rDNA. Antifungal susceptibility for fluconazole was determined by Etest. The number of isolates identified as C. dubliniensis, C. albicans and other yeast species were 71 (4.9%), 862 (59.6%) and 512 (35%) respectively. All the C. dubliniensis isolates originated from respiratory (5.9%) or oral (3.2%) specimens with an overall prevalence of 4.9%, and were found to be susceptible to fluconazole. The isolation of C. dubliniensis from respiratory or oral specimens and not from blood or urine specimens suggests that this species has preference to colonise these sites of human body.

Genetic relatedness of subgingival and buccal Candida dubliniensis isolates in immunocompetent subjects assessed by RAPD-PCR

Background

It is recognized that Candida dubliniensis commonly colonizes oral and subgingival sites in immunocompetent subjects with periodontal disease.

Objective

Since there are few data available on genetic characterization of C. dubliniensis in periodontal pockets and other oral sites, the aim of this study was to characterize subgingival and mucosal C. dubliniensis isolates recovered from immunocompetent subjects and to assay the genetic similarity of such isolates from both niches in the same patient by random amplified polymorphic DNA (RAPD).

Design

C. dubliniensis recovered from subgingival plaque and from buccal cavity samples were studied in 240 immunocompetent non-smoking individuals. Arbitrary amplification was carried out by RAPD-polymerase chain reaction (PCR).

Results

RAPD analysis showed identical genotypes of C. dubliniensis in different sampling sites (buccal cavity and subgingival areas) in eight of 10 patients except for those derived from two participants who presented presumably unrelated isolates.

Conclusions

On the basis of the findings presented, the origin of the colonization of C. dubliniensis in subgingival biofilm seems to be the buccal cavity in a single patient. Consequently, it may be assumed that most of C. dubliniensis in these sites arise from the endogenous commensal strains.

Isolation of Candida dubliniensis from denture wearers

Candida albicans is considered the most important Candida species able to cause oral infections in denture wearers. In recent years, Candida dubliniensis has emerged as a pathogenic yeast in humans. The close phenotypic similarities of C. albicans and C. dubliniensis have led to the misidentification of these species. In this work, our aim was to verify through PCR the presence of C. dubliniensis in palate and maxillary denture samples from 112 denture wearers presenting with or without denture-related stomatitis (DRS). C. dubliniensis was isolated at low rates from both palate (5.3 % and 10.7 %) and maxillary denture (5.3 % and 8.9 %) samples from wearers regardless of the presence of the disease. However, when C. dubliniensis was detected in individuals with DRS, it was always associated with C. albicans. In addition, our results showed that C. albicans was the most commonly identified candidal species in maxillary denture and hard palate samples from DRS patients (78.5 % and 89.2 %, respectively) as well as from controls (31.2 % and 28.5 %, respectively). In conclusion, C. dubliniensis was detected in the oral environment of denture wearers. The association of C. dubliniensis with C. albicans occurred in approximately 10 % of the DRS cases.

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.

[Candida dubliniensis: Identification methods and epidemiologic implication]

Candida dubliniensis was recently described (1995) associated with oral candidiasis in HIV-positive patients. This organism is very closely related to the pathogenic human yeast, Candida albicans, and share a great number of phenotypic and genotypic characters. This great similarity limits the discrimination between these two species. Several phenotypic and molecular methods were developed. The phenotypic methods are simply used in routine discrimination between these two species and depend on the growth at high temperature, sugar assimilation, growth on special mediums and chlamydospore production…; but these methods are insensitive in discrimination between these two species. The molecular biology methods are highly reliable and able to confirm rapidly the identification of this species. In this article, we will review the various studies run out concerning the methods deployed for the identification of C. dubliniensis as well as the epidemiological implication of this new pathogen.

Gain-of-function mutations in the transcription factor MRR1 are responsible for overexpression of the MDR1 efflux pump in fluconazole-resistant Candida dubliniensis strains

Candida dubliniensis, a yeast that is closely related to Candida albicans, can rapidly develop resistance to the commonly used antifungal agent fluconazole in vitro and in vivo during antimycotic therapy. Fluconazole resistance in C. dubliniensis is usually caused by constitutive overexpression of the MDR1 gene, which encodes a multidrug efflux pump of the major facilitator superfamily. The zinc cluster transcription factor Mrr1p has recently been shown to control MDR1 expression in C. albicans in response to inducing stimuli, and gain-of-function mutations in the MRR1 gene result in constitutive upregulation of the MDR1 efflux pump. We identified a gene with a high degree of similarity to C. albicans MRR1 (CaMRR1) in the C. dubliniensis genome sequence. When C. dubliniensis MRR1 (CdMRR1) was expressed in C. albicans mrr1Delta mutants, it restored benomyl-inducible MDR1 expression, demonstrating that CdMRR1 is the ortholog of CaMRR1. To investigate whether MDR1 overexpression in C. dubliniensis is caused by mutations in MRR1, we sequenced the MRR1 alleles from a fluconazole-resistant, clinical C. dubliniensis isolate and a matched, fluconazole-susceptible isolate from the same patient as well as those from four in vitro-generated, fluconazole-resistant C. dubliniensis strains derived from two different C. dubliniensis isolates. We found that all five resistant strains contained single nucleotide substitutions or small in-frame deletions that resulted in amino acid changes in Mrr1p. Expression of these mutated alleles in C. albicans resulted in the constitutive activation of the MDR1 promoter and multidrug resistance. Therefore, mutations in MRR1 are the major cause of MDR1 upregulation in both C. albicans and C. dubliniensis, demonstrating that the transcription factor Mrr1p plays a central role in the development of drug resistance in these human fungal pathogens.

Species distribution and in vitro antifungal susceptibility of oral yeast isolates from Tanzanian HIV-infected patients with primary and recurrent oropharyngeal candidiasis

Background

In Tanzania, little is known on the species distribution and antifungal susceptibility profiles of yeast isolates from HIV-infected patients with primary and recurrent oropharyngeal candidiasis.

Methods

A total of 296 clinical oral yeasts were isolated from 292 HIV-infected patients with oropharyngeal candidiasis at the Muhimbili National Hospital, Dar es Salaam, Tanzania. Identification of the yeasts was performed using standard phenotypic methods. Antifungal susceptibility to fluconazole, itraconazole, miconazole, clotrimazole, amphotericin B and nystatin was assessed using a broth microdilution format according to the guidelines of the Clinical and Laboratory Standard Institute (CLSI; M27-A2).

Results

Candida albicans was the most frequently isolated species from 250 (84.5%) patients followed by C. glabrata from 20 (6.8%) patients, and C. krusei from 10 (3.4%) patients. There was no observed significant difference in species distribution between patients with primary and recurrent oropharyngeal candidiasis, but isolates cultured from patients previously treated were significantly less susceptible to the azole compounds compared to those cultured from antifungal naïve patients.

Conclusion

C. albicans was the most frequently isolated species from patients with oropharyngeal candidiasis. Oral yeast isolates from Tanzania had high level susceptibility to the antifungal agents tested. Recurrent oropharyngeal candidiasis and previous antifungal therapy significantly correlated with reduced susceptibility to azoles antifungal agents.

The relationship between antifungal usage and antifungal susceptibility in clinical isolates of Candida: a multicenter Korean study

There have been very few multicenter studies of the relationship between the use of antifungals and resistance to them. We investigated the antifungal susceptibility of 1,301 clinical isolates of Candida collected from nine Korean hospitals during a 3-month period in 2006 to explore the existence of this type of relationship. Antifungal usage in the preceding year, defined as the daily dose per 1,000 patient days (DDD/1,000 PD), was calculated for each hospital. Resistance to fluconazole, itraconazole, and amphotericin B was detected in 2, 9, and 0.2% of the isolates, respectively. The MIC(50)/MIC(90) values were 0.03/0.125 mg/L for voriconazole, 0.06/0.25 mg/l for caspofungin, and 0.03/0.125 mg/l for micafungin. The total usage of systemic antifungals varied considerably among the nine hospitals, ranging from 6.1 to 96.2 DDD/1,000 PD. No relationship was found between the use of fluconazole (MIC> or =64 mg/l) or itraconazole (MIC> or =1 mg/l) and resistance in the Candida species (P>0.05). However, significant correlations were found between the percentage of Candida isolates that were non-susceptible to fluconazole (MIC> or =16 mg/l) and fluconazole usage (r=0.733, P=0.025) or total antifungal usage (r=0.767, P=0.016).

Candida Glabrata Esophagitis: new case reports and management

Candida esophagitis (CE) is a common opportunistic infection in the immunocompromised host. C. glabrata is rarely cited as agent of CE and has been underestimated due to lack of proper identification. In this study, two cases of C. glabrata esophagitis in AIDS and chagasic patients are reported. Diagnosis of Candida species should be considered an important key for the ideal choice of antifungal therapy against this mycosis.