Emerging echinocandin-resistant Candida albicans and glabrata in Switzerland

Reassessment of the role of combination antifungal therapy in the current era

PURPOSE OF REVIEW

Given the high mortality and morbidity associated with invasive fungal diseases (IFDs), the use of combination antifungal therapies is often considered despite the dearth of data. This review aims to summarize the current state of literature of combination antifungal therapies, discussing the potential roles of newer antifungal combinations and key considerations for their clinical use.

RECENT FINDINGS

In infections other than cryptococcal meningitis or in the setting of empirical treatment for suspected azole-resistant Aspergillus infections, the utility of the combination antifungal approaches remains controversial given the paucity of well designed randomized controlled trials. Data on potential combined antifungal treatments have been primarily limited to in-vitro studies, animal models, case reports and/or observational studies. With availability of novel antifungal agents (e.g. ibrexafungerp, fosmanogepix), combination therapy to treat mould infections should be re-visited. A phase 2 clinical trial of ibrexafungerp combined with voriconazole to treat invasive pulmonary aspergillosis is on-going.

SUMMARY

There is a need to investigate the use of combination antifungal agents. This includes delineating the indication of these combined antifungal therapies and determining how to use them most appropriately in the clinical setting.

Azole Combinations and Multi-Targeting Drugs That Synergistically Inhibit Candidozyma auris

Limited antifungal treatment options and drug resistance require innovative approaches to effectively combat fungal infections. Combination therapy is a promising strategy that addresses these pressing issues by concurrently targeting multiple cellular sites. The drug targets usually selected for combination therapy are from different cellular pathways with the goals of increasing treatment options and reducing development of resistance. However, some circumstances can prevent the implementation of combination therapy in clinical practice. These could include the increased risk of adverse effects, drug interactions, and even the promotion of drug resistance. Furthermore, robust clinical evidence supporting the superiority of combination therapy over monotherapy is limited and underscores the need for further research. Despite these challenges, synergies detected with different antifungal classes, such as the azoles and echinocandins, suggest that treatment strategies can be optimized by better understanding the underlying mechanisms. This review provides an overview of multi-targeting combination strategies with a primary focus on Candidozyma auris infections.

New and emerging roles for inhalational and direct antifungal drug delivery approaches for treatment of invasive fungal infections

INTRODUCTION

The rising prevalence of difficult-to-treat, deep-seated invasive fungal diseases (IFD) has led to high mortality. Currently available antifungal treatments, administered predominantly orally or intravenously, may not sufficiently penetrate certain body sites, and/or are associated with systemic toxicity. Little is known about how to position alternative administration approaches such as inhalational and direct drug delivery routes.

AREAS COVERED

This review provides an updated overview of unconventional drug delivery strategies for managing IFD, focusing on inhalational (to target the lungs) and direct delivery methods to the central nervous system, bone/joint, and eyes. Novel compounds (e.g. opelconazole) and existing antifungals with innovative drug delivery systems currently undergoing clinical trials and/or used off-label in the clinical setting are discussed.

EXPERT OPINION

For both inhalational agents and direct delivery approaches, there are similar challenges that include the absence of: approved formulations for specific administration routes, delivery vehicles that are simple and safe to use whilst maintaining potency and efficiency of delivery, animal models suitable for investigating pharmacokinetic/pharmacodynamic profiles of inhaled antifungals, and consensus on the composite endpoints and intervals for of follow-up in clinical trials. To meet these challenges, cooperation of all stakeholders in drug development and regulation is required.

Antifungal activity of tannic acid against Candida spp. and its mechanism of action

The increase in fungal resistance is a major public health concern. In this context, Candida spp. is an important genus related to invasive diseases, especially in immunosuppressed patients. The relevance of alternative approaches to increasing fungal resistance stands out, in which products of natural origin demonstrate potential antifungal activity in vitro against Candida spp. In this sense, this work aimed to evaluate the in vitro activity of tannic acid against Candida spp. Minimum inhibitory concentration (MIC) was determined for tannic acid and the antifungals, and the checkerboard assay was performed to analyze the interactions between them. Furthermore, we evaluated the tannic acid antibiofilm activity and its possible mechanism of action. Tannic acid showed MIC ranging to 0.06 to 0.5 µg/ml and showed no loss of effectiveness when combined with antifungals. Also, is safe at the concentrations it exerts its antifungal activity in pre-formed biofilms, as demonstrated by IC50 in murine fibroblasts cells and the hemolytic assay. Additionally, its mechanisms of action can be related with induction of signals that lead to apoptosis in fungal cells.

Phytolacca tetramera berries extracts and its main constituents as potentiators of antifungal drugs against Candida spp

BACKGROUND

Extensive antifungal drug use has enhanced fungal resistance, resulting in persistent mycoses. Combining antifungal plant extracts/compounds with these drugs offers good alternatives to increase the activity of both partners, minimize side effects, and overcome drug resistance. In our previous study, Phytolacca tetramera berries extracts demonstrated activity against Candida spp., correlating with the amount of the main constituent phytolaccoside B and its genin, phytolaccagenin. The extracts and phytolaccagenin altered the fungal plasma membrane by binding to ergosterol, whereas phytolaccoside B increased chitin synthase activity. However, the presence of triterpenoid saponins in Phytolacca spp. has been linked to acute toxicity in humans.

PURPOSE

This study aimed to evaluate combinations of P. tetramera berries extracts, phytolaccoside B and phytolaccagenin, together with commercial antifungals [amphotericin B, fluconazole, itraconazole, posaconazole, and caspofungin] against Candida albicans and Candida glabrata, to find synergistic effects with multi-target actions, in which the doses of both partners are reduced, and therefore their toxicity. Additionally, we intended to explore their anti-virulence capacity, thereby hindering the development of drug-resistant strains.

METHODS

The effects of these combinations were evaluated using both the checkerboard and isobologram methods. Fractional Inhibitory Concentration Index and Dose Reduction Index were calculated to interpret the combination results. To confirm the multi-target effect, studies on mechanisms of action of synergistic mixtures were performed using ergosterol-binding and quantification assays. The ability to inhibit Candida virulence factors, including biofilm formation and eradication from inert surfaces, was also evaluated. Quantification of active markers was performed using a validated UHPLC-ESI-MS method.

RESULTS

Eight synergistic combinations of P. tetramera extracts or phytolaccagenin (but not phytolaccoside B) with itraconazole or posaconazole were obtained against C. albicans, including a resistant strain. These mixtures acted by binding to ergosterol, decreasing its whole content, and inhibiting Candida biofilm formation in 96-well microplates and feeding tubes in vitro, but were unable to eradicate preformed biofilms.

CONCLUSIONS

This study demonstrated the synergistic and anti-virulence effects of P. tetramera berries extracts and phytolaccagenin with antifungal drugs against Candida spp., providing novel treatment avenues for fungal infections with reduced doses of both natural products and commercial antifungals, thereby mitigating potential human toxicity concerns.

Epidemiology of Candidemia in Mashhad, Northeast Iran: A Prospective Multicenter Study (2019-2021)

Candidemia is a major cause of morbidity and mortality in health care settings, and its epidemiology is changing. In the last two decades, the proportion of non-albicans Candida (NAC) yeasts in candidemia has increased. These yeasts more often display resistance to common antifungals. In many western countries, candidemia is mainly caused by susceptible C. albicans, while in resource-limited countries, including Iran, the candidemia species distribution is studied less often. Here, we investigated the species distribution, resistance levels, and characteristics of patients with candidemia in five hospitals in Mashhad (northeast Iran) for two years (2019-2021). Yeast isolates from blood were identified with MALDI-TOF MS and subjected to antifungal susceptibility testing (AFST) using the broth microdilution method, while molecular genotyping was applied to Candida parapsilosis isolates. In total, 160 yeast isolates were recovered from 160 patients, of which the majority were adults (60%). Candidemia was almost equally detected in men (48%) and women (52%). Almost half of patients (n = 67, 49%) were from intensive care units (ICUs). C. parapsilosis (n = 58, 36%) was the most common causative agent, surpassing C. albicans (n = 52, 33%). The all-cause mortality rate was 53%, with C. albicans candidemia displaying the lowest mortality with 39%, in contrast to a mortality rate of 59% for NAC candidemia. With microbroth AFST, nearly all tested isolates were found to be susceptible, except for one C. albicans isolate that was resistant to anidulafungin. By applying short tandem repeat (STR) genotyping to C. parapsilosis, multiple clusters were found. To summarize, candidemia in Mashhad, Iran, from 2019 to 2021, is characterized by common yeast species, in particular C. parapsilosis, for which STR typing indicates potential nosocomial transmission. The overall mortality is high, while resistance rates were found to be low, suggesting that the high mortality is linked to limited diagnostic options and insufficient medical care, including the restricted use of echinocandins as the first treatment option.

Fighting Emerging Caspofungin-Resistant Candida Species: Mitigating Fks1-Mediated Resistance and Enhancing Caspofungin Efficacy by Chitosan

Invasive candidiasis poses a worldwide threat because of the rising prevalence of antifungal resistance, resulting in higher rates of morbidity and mortality. Additionally, Candida species, which are opportunistic infections, have significant medical and economic consequences for immunocompromised individuals. This study explores the antifungal potential of chitosan to mitigate caspofungin resistance in caspofungin-resistant Candida albicans, C. krusei, and C. tropicalis isolates originating from human and animal sources using agar well diffusion, broth microdilution tests, and transmission electron microscope (TEM) analysis of treated Candida cells. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) was performed to assess the expression of SAGA complex genes (GCN5 and ADA2) and the caspofungin resistance gene (FKS) in Candida species isolates after chitosan treatment. The highest resistance rate was observed to ketoconazole (80%) followed by clotrimazole (62.7%), fluconazole (60%), terbinafine (58%), itraconazole (57%), miconazole (54.2%), amphotericin B (51.4%), voriconazole (34.28%), and caspofungin (25.7%). Nine unique FKS mutations were detected, including S645P (n = 3 isolates), S645F, L644F, S645Y, L688M, E663G, and F641S (one isolate in each). The caspofungin minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values before chitosan treatment ranged from 2 to 8 µg/mL and 4 to 16 µg/mL, respectively. However, the MIC and MFC values were decreased after chitosan treatment (0.0625-1 µg/mL) and (0.125-2 µg/mL), respectively. Caspofungin MIC was significantly decreased (p = 0.0007) threefold following chitosan treatment compared with the MIC values before treatment. TEM analysis revealed that 0.5% chitosan disrupted the integrity of the cell surface, causing irregular morphologies and obvious aberrant changes in cell wall thickness in caspofungin-resistant and sensitive Candida isolates. The cell wall thickness of untreated isolates was 0.145 μm in caspofungin-resistant isolate and 0.125 μm in sensitive isolate, while it was significantly lower in chitosan-treated isolates, ranging from 0.05 to 0.08 μm when compared with the cell wall thickness of sensitive isolate (0.03 to 0.06 μm). Moreover, RT-qPCR demonstrated a significant (p < 0.05) decrease in the expression levels of histone acetyltransferase genes (GCN5 and ADA2) and FKS gene of caspofungin-resistant Candida species isolates treated with 0.5% chitosan when compared with before treatment (fold change values ranged from 0.001 to 0.0473 for GCN5, 1.028 to 4.856 for ADA2, and 2.713 to 12.38 for FKS gene). A comparison of the expression levels of cell wall-related genes (ADA2 and GCN5) between caspofungin-resistant and -sensitive isolates demonstrated a significant decrease following chitosan treatment (p < 0.001). The antifungal potential of chitosan enhances the efficacy of caspofungin against various caspofungin-resistant Candida species isolates and prevents the development of further antifungal resistance. The results of this study contribute to the progress in repurposing caspofungin and inform a development strategy to enhance its efficacy, appropriate antifungal activity against Candida species, and mitigate resistance. Consequently, chitosan could be used in combination with caspofungin for the treatment of candidiasis.

Modeling of intravenous caspofungin administration using an intestine-on-chip reveals altered Candida albicans microcolonies and pathogenicity

Candida albicans is a commensal yeast of the human intestinal microbiota that, under predisposing conditions, can become pathogenic and cause life-threatening systemic infections (candidiasis). Fungal-host interactions during candidiasis are commonly studied using conventional 2D in vitro models, which have provided critical insights into the pathogenicity. However, microphysiological models with a higher biological complexity may be more suitable to mimic in vivo-like infection processes and antifungal drug efficacy. Therefore, a 3D intestine-on-chip model was used to investigate fungal-host interactions during the onset of invasive candidiasis and evaluate antifungal treatment under clinically relevant conditions. By combining microbiological and image-based analyses we quantified infection processes such as invasiveness and fungal translocation across the epithelial barrier. Additionally, we obtained novel insights into fungal microcolony morphology and association with the tissue. Our results demonstrate that C. albicans microcolonies induce injury to the epithelial tissue by disrupting apical cell-cell contacts and causing inflammation. Caspofungin treatment effectively reduced the fungal biomass and induced substantial alterations in microcolony morphology during infection with a wild-type strain. However, caspofungin showed limited effects after infection with an echinocandin-resistant clinical isolate. Collectively, this organ-on-chip model can be leveraged for in-depth characterization of pathogen-host interactions and alterations due to antimicrobial treatment.

Two promising Bacillus-derived antifungal lipopeptide leads AF4 and AF5 and their combined effect with fluconazole on the in vitro Candida glabrata biofilms

Introduction: Candida species are endowed with the ability to produce biofilms, which is one of the causes of pathogenicity, as biofilms protect yeasts from antifungal drugs. Candida glabrata (Nakaseomyces glabrata) is one of the most prevalent pathogenic yeasts in humans and a biofilm producer. Methods: The study was aimed at evaluating the combined effects of two highly promising antifungal biomolecules (AF4 and AF5) lipopeptide in nature, chromatographically purified to homogeneity from Bacillus subtilis (B. subtilis) and the standard antifungal fluconazole (at different concentrations) to demonstrate C. glabrata biofilm formation inhibition. Biofilm production and inhibition were evaluated by quantification of the biofilm biomass and metabolic activity using crystal violet (CV) staining and XTT reduction assays, respectively. Microscopic techniques such as confocal scanning laser microscopy (CSLM) and scanning electron microscopy (SEM) were employed to visualize biofilm formation and inhibition. Results and Discussion: Compared to untreated and fluconazole-treated biofilms, an enhanced in vitro anti-biofilm effect of the antifungal lipopeptides AF4/AF5 alone and their combinations with fluconazole was established. The lipopeptides AF4/AF5 alone at 8 and 16 μg/mL exhibited significant biomass and metabolic activity reductions. SEM and CSLM images provided evidence that the lipopeptide exposure results in architectural alterations and a significant reduction of C. glabrata biofilms, whereas (2', 7'-dichlorofluorescin diacetate (DCFDA) and propidium iodide (PI) analyses showed reactive oxygen species (ROS) generation along with membrane permeabilization. The estimation of exopolysaccharides (EPS) in AF4/AF5-treated biofilms indicated EPS reduction. The combinations of fluconazole (64/128 μg/mL) and AF4/AF5 lipopeptide (16 μg/mL) were found to significantly disrupt the mature (24 h) biofilms as revealed by CSLM and SEM studies. The CSLM images of biofilms were validated using COMSTAT. The FTIR-analyses indicate the antibiofilm effects of both lipopeptides on 24 h biofilms to support CSLM and SEM observations. The combinations of fluconazole (64/128 μg/mL) and AF4/AF5 lipopeptide were found to disrupt the mature biofilms; the study also showed that the lipopeptides alone have the potentials to combat C. glabrata biofilms. Taken together, it may be suggested that these lipopeptide leads can be optimized to potentially apply on various surfaces to either reduce or nearly eradicate yeast biofilms.

Stephanoascus ciferrii Complex: The Current State of Infections and Drug Resistance in Humans

In recent years, the incidence of fungal infections in humans has increased dramatically, accompanied by an expansion in the number of species implicated as etiological agents, especially environmental fungi never involved before in human infection. Among fungal pathogens, Candida species are the most common opportunistic fungi that can cause local and systemic infections, especially in immunocompromised individuals. Candida albicans (C. albicans) is the most common causative agent of mucosal and healthcare-associated systemic infections. However, during recent decades, there has been a worrying increase in the number of emerging multi-drug-resistant non-albicans Candida (NAC) species, i.e., C. glabrata, C. parapsilosis, C. tropicalis, C. krusei, C. auris, and C. ciferrii. In particular, Candida ciferrii, also known as Stephanoascus ciferrii or Trichomonascus ciferrii, is a heterothallic ascomycete yeast-like fungus that has received attention in recent decades as a cause of local and systemic fungal diseases. Today, the new definition of the S. ciferrii complex, which consists of S. ciferrii, Candida allociferrii, and Candida mucifera, was proposed after sequencing the 18S rRNA gene. Currently, the S. ciferrii complex is mostly associated with non-severe ear and eye infections, although a few cases of severe candidemia have been reported in immunocompromised individuals. Low susceptibility to currently available antifungal drugs is a rising concern, especially in NAC species. In this regard, a high rate of resistance to azoles and more recently also to echinocandins has emerged in the S. ciferrii complex. This review focuses on epidemiological, biological, and clinical aspects of the S. ciferrii complex, including its pathogenicity and drug resistance.

Time to positivity of blood cultures causing candidemia and its relation to mortality

Background and Objectives

Early diagnosis of candidemia is of vital importance in reducing mortality and morbidity. The main objective of the study was to determine the TTP (Time to Positivity) of different species of Candida causing bloodstream infection and to see whether TTP can help differentiate Candida glabrata which is frequently fluconazole resistant from Fluconazole sensitive Candida.

Materials and Methods

TTP (Time to positivity) and AAT (Appropriate Antifungal therapy) were noted for Blood cultures becoming positive for Candida. Presence of Risk factors for candidemia like prolonged ICU stay, neutropenia, Total Parenteral Nutrition (TPN), use of steroids , broad spectrum antibiotics, use of Central Venous Catheter, Foleys catheter were also analyzed.

Results

The most frequent isolates were Candida parapsilosis, Candida tropicalis and Candida albicans. The median TTP for all Candida isolates in our study was 34 hours. The diagnostic sensitivity of TTP for detecting C. glabrata and C. tropicalis in patients with candidemia was 88% and 85% respectively. TTP showed that there was no difference in survival between TTP <24 hrs. and > 24hrs. Initiation of antifungal therapy <24 hours and > 24hrs after onset of candidemia had no association with survival.

Conclusion

Longer TTP maybe predictive of C. glabrata while shorter TTP may be predictive of C. tropicalis. In our study we found that fluconazole resistant Candida causing blood stream infection is quite unlikely if the TTP of the isolate is <48hrs.

A novel model for predicting deep-seated candidiasis due to Candida glabrata among cancer patients: A 6-year study in a cancer center of China

Followed by Candida albicans, Candida glabrata ranks as the second major species contributing to invasive candidiasis. Given the higher medical burden and lower susceptibility to azoles in C. glabrata infections, identifying these infections is critical. From 2016 to 2021, patients with deep-seated candidiasis due to C. glabrata and non-glabrata Candida met the criteria to be enrolled in the study. Clinical data were randomly divided into training and validation cohorts. A predictive model and nomogram were constructed using R software based on the stepwise algorithm and logistic regression. The performance of the model was assessed by the area under the receiver operating characteristic curve and decision curve analysis (DCA). A total of 197 patients were included in the study, 134 of them infected with non-glabrata Candida and 63 with C. glabrata. The predictive model for C. glabrata infection consisted of gastrointestinal cancer, co-infected with bacteria, diabetes mellitus, and kidney dysfunction. The specificity was 84.1% and the sensitivity was 61.5% in the validation cohort when the cutoff value was set to the same as the training cohort. Based on the model, treatment for patients with a high-risk threshold was better than 'treatment for all' in DCA, while opting low-risk patients out of treatment was also better than 'treatment for none' in opt-out DCA. The predictive model provides a rapid method for judging the probability of infections due to C. glabrata and will be of benefit to clinicians making decisions about therapy strategies.

Genome-Wide DNA Changes Acquired by Candida albicans Caspofungin-Adapted Mutants

Drugs from the echinocandin (ECN) class are now recommended 'front-line' treatments of infections caused by a prevailing fungal pathogen, C. albicans. However, the increased use of ECNs is associated with a rising resistance to ECNs. As the acquisition of ECN resistance in C. albicans is viewed as a multistep evolution, determining factors that are associated with the decreased ECN susceptibility is of importance. We have recently identified two cohorts of genes that are either up- or downregulated in concert in order to control remodeling of cell wall, an organelle targeted by ECNs, in laboratory mutants with decreased ECN susceptibility. Here, we profiled the global DNA sequence of four of these adapted mutants in search of DNA changes that are associated with decreased ECN susceptibility. We find a limited number of 112 unique mutations representing two alternative mutational pathways. Approximately half of the mutations occurred as hotspots. Approximately half of mutations and hotspots were shared by ECN-adapted mutants despite the mutants arising as independent events and differing in some of their phenotypes, as well as in condition of chromosome 5. A total of 88 mutations are associated with 43 open reading frames (ORFs) and occurred inside of an ORF or within 1 kb of an ORF, predominantly as single-nucleotide substitution. Mutations occurred more often in the 5'-UTR than in the 3'-UTR by a 1.67:1 ratio. A total of 16 mutations mapped to eight genomic features that were not ORFs: Tca4-4 retrotransposon; Tca2-7 retrotransposon; lambda-4a long terminal repeat; mu-Ra long terminal repeat; MRS-7b Major Repeat Sequence; MRS-R Major Repeat Sequence; RB2-5a repeat sequence; and tL (CAA) leucine tRNA. Finally, eight mutations are not associated with any ORF or other genomic feature. Repeated occurrence of single-nucleotide substitutions in non-related drug-adapted mutants strongly indicates that these DNA changes are accompanying drug adaptation and could possibly influence ECN susceptibility, thus serving as factors facilitating evolution of ECN drug resistance due to classical mutations in FKS1.

Epidemiology, antifungal susceptibility, risk factors, and mortality of persistent candidemia in adult patients in China: a 6-year multicenter retrospective study

BACKGROUND

Data on persistent candidemia (PC), a recognized complication of candidemia, are lacking in China. This study aimed to investigate the clinical characteristics and risk factors for the mortality of PC among adults in China.

METHODS

This 6-year retrospective study analyzed the prevalence, species distribution, antifungal susceptibility, risk factors, and patient mortality of PC among adults in three regional tertiary teaching hospitals in China from 2016 to 2021. We collected electronic laboratory records data of PC and non-PC patients and used the Student test or Mann-Whitney U test for a retrospective study. Logistic regression was used to identify risk factors associated with persistent candidemia.

RESULTS

The definition of PC was fulfilled by 36 patients (13.7%, 36/263). The mean age of the patients was 59.9 years (60 years for patients with PC; 59.8 years for those with non-PC; P > 0.05) and 131 (60.1%) were men [16 with PC (44.4%), 115 with non-PC (63.2%), P < 0.05]. The mean annual incidence was 0.15/1000 admissions (including PC 0.03/1000 admissions vs. non-PC 0.12/1000 admissions, P < 0.05). Candida parapsilosis (14/36, 38.9%) and Candida albicans (81/182, 44.5%) were the predominant pathogens in patients with PC and non-PC, respectively. Most isolates were susceptible to flucytosine (99.0%) and amphotericin B (99.5%), and the activity of antifungal agents against Candida species was not statistically significantly different between patients with PC and non-PC (P > 0.05). The 30-day mortality rate was 20.2% (16.7% with PC vs. 20.9% with non-PC, P > 0.05). Multivariable regression analysis showed that use of broad-spectrum antibiotics (odds ratio (OR), 5.925; 95% confidence interval (CI), 1.886-18.616, P = 0.002), fluconazole (OR, 3.389; 95% CI, 1.302-8.820, P = 0.012) and C. parapsilosis infection (OR, 6.143; 95% CI, 2.093-18.031, P = 0.001) were independent predictors of PC, sex (male) (OR, 0.199; 95% CI, 0.077-0.518, P = 0.001) was the protective factor for PC. Respiratory dysfunction (OR, 5.763; 95% CI, 1.592-20.864, P = 0.008) and length of hospital stay(OR, 0.925; 95% CI, 0.880-0.973, P = 0.002) were independent predictors of 30-day mortality in patients with non-PC. C. tropicalis bloodstream infection (OR, 12.642; 95% CI, 1.059-150.951; P = 0.045) was an independent predictor of 30-day mortality in patients with PC.

CONCLUSIONS

The epidemiological data of patients with PC and non-PC were different in the distribution of Candida species, the mean annual incidence and independent predictors of 30-day mortality. Flucytosine and amphotericin B could be used as first-choice drugs in the presence of PC infections.

P4-ATPase subunit Cdc50 plays a role in yeast budding and cell wall integrity in Candida glabrata

BACKGROUND

As highly-conserved types of lipid flippases among fungi, P4-ATPases play a significant role in various cellular processes. Cdc50 acts as the regulatory subunit of flippases, forming heterodimers with Drs2 to translocate aminophospholipids. Cdc50 homologs have been reported to be implicated in protein trafficking, drug susceptibility, and virulence in Saccharomyces cerevisiae, Candida albicans and Cryptococcus neoformans. It is likely that Cdc50 has an extensive influence on fungal cellular processes. The present study aimed to determine the function of Cdc50 in Candida glabrata by constructing a Δcdc50 null mutant and its complemented strain.

RESULTS

In Candida glabrata, the loss of Cdc50 led to difficulty in yeast budding, probably caused by actin depolarization. The Δcdc50 mutant also showed hypersensitivity to azoles, caspofungin, and cell wall stressors. Further experiments indicated hyperactivation of the cell wall integrity pathway in the Δcdc50 mutant, which elevated the major cell wall contents. An increase in exposure of β-(1,3)-glucan and chitin on the cell surface was also observed through flow cytometry. Interestingly, we observed a decrease in the phagocytosis rate when the Δcdc50 mutant was co-incubated with THP-1 macrophages. The Δcdc50 mutant also exhibited weakened virulence in nematode survival tests.

CONCLUSION

The results suggested that the lipid flippase subunit Cdc50 is implicated in yeast budding and cell wall integrity in C. glabrata, and thus have a broad influence on drug susceptibility and virulence. This work highlights the importance of lipid flippase, and offers potential targets for new drug research.

Novel Therapeutic Approaches to Invasive Candidiasis: Considerations for the Clinician

Invasive candidiasis (IC), due to the yeast pathogen Candida, is still a major cause of in-hospital morbidity and mortality. The limited number of antifungal drug classes and the emergence of multi-resistant Candida species, such as Candida auris and some Candida glabrata isolates, is concerning. However, recent advances in antifungal drug development provide promising perspectives for the therapeutic approach of IC. Notably, three novel antifungal agents, currently in Phase II/III clinical trials, are expected to have an important place for the treatment of IC in the future. Rezafungin is a novel echinocandin with prolonged half-life. Ibrexafungerp and fosmanogepix are two first-in-class antifungal drugs with broad spectrum activity against Candida spp., including C. auris and echinocandin-resistant species. These novel antifungal agents also represent interesting alternative options because of their acceptable oral bioavailability (ibrexafungerp and fosmanogepix) or their large interdose interval (once weekly intravenous administration for rezafungin) for prolonged and/or outpatient treatment of complicated IC. This review discusses the potential place of these novel antifungal drugs for the treatment of IC considering their pharmacologic properties and their preclinical and clinical data.

The Gcn5-Ada2-Ada3 histone acetyltransferase module has divergent roles in pathogenesis of Candida glabrata

Candida glabrata is an opportunistic fungal pathogen and the second most prevalent species isolated from candidiasis patients. C. glabrata has intrinsic tolerance to antifungal drugs and oxidative stresses and the ability to adhere to mucocutaneous surfaces. However, knowledge about the regulation of its virulence traits is limited. The Spt-Ada-Gcn5 acetyltransferase (SAGA) complex modulates gene transcription by histone acetylation through the histone acetyltransferase (HAT) module comprised of Gcn5-Ada2-Ada3. Previously, we showed that the ada2 mutant was hypervirulent but displayed decreased tolerance to antifungal drugs and cell wall perturbing agents. In this study, we further characterized the functions of Ada3 and Gcn5 in C. glabrata. We found that single, double, or triple deletions of the HAT module, as expected, resulted in a decreased level of acetylation on histone H3 lysine 9 (H3K9) and defective growth. These mutants were more susceptible to antifungal drugs, oxidative stresses, and cell wall perturbing agents compared with the wild-type. In addition, HAT module mutants exhibited enhanced agar invasion and upregulation of adhesin and proteases encoding genes, whereas the biofilm formation of those mutants was impaired. Interestingly, HAT module mutants exhibited enhanced induction of catalases (CTA1) expression upon treatment with H2O2 compared with the wild-type. Lastly, although ada3 and gcn5 exhibited marginal hypervirulence, the HAT double and triple mutants were hypervirulent in a murine model of candidiasis. In conclusion, the HAT module of the SAGA complex plays unique roles in H3K9 acetylation, drug tolerance, oxidative stress response, adherence, and virulence in C. glabrata.

Expanding the therapeutic options for Candida infections using novel inhibitors of secreted aspartyl proteases

For widening the therapeutic options for Candida management, the druggability of Candida proteome was systematically investigated using an innovative pipeline of high-throughput data mining algorithms, followed by in vitro validation of the observations. Through this exercise, HIV-1 protease was found to share structural similarity with secreted aspartyl protease-3 (SAP3), a virulence protein of Candida. Using the molecular fingerprint of HIV-1 protease inhibitor GRL-09510, we performed virtual screening of peptidomimetic library followed by high-precision docking and MD simulations for discovery of SAP inhibitors. Wet-lab validation of the four shortlisted peptidomimetics revealed that two molecules, when used in combination with fluconazole, could significantly reduce the dosage of fluconazole required for 50% inhibition of Candida albicans. The SAP inhibitory activity of these peptidomimetics was confirmed through SAP assays and found to be on par with pepstatin A, a known peptidomimetic inhibitor of aspartyl proteases.

Multiple Genes of Candida albicans Influencing Echinocandin Susceptibility in Caspofungin-Adapted Mutants

Candida albicans is an opportunistic human fungal pathogen that causes invasive infections in immunocompromised individuals. Despite the high anticandidal activity among the echinocandins (ECNs), a first-line therapy, resistance remains an issue. Furthermore, many clinical isolates display decreased ECN susceptibility, a physiological state which is thought to lead to resistance. Determining the factors that can decrease susceptibility is of high importance. We searched for such factors genome-wide by comparing the transcriptional profiles of five mutants that acquired decreased caspofungin susceptibility in vitro in the absence of canonical FKS1 resistance mutations. The mutants were derived from two genetic backgrounds and arose due to independent mutational events, some with monosomic chromosome 5 (Ch5). We found that the mutants exhibit common transcriptional changes. In particular, all mutants upregulate five genes from Ch2 in concert. Knockout experiments show that all five genes positively influence caspofungin and anidulafungin susceptibility and play a role in regulating the cell wall mannan and glucan contents. The functions of three of these genes, orf19.1766, orf19.6867, and orf19.5833, were previously unknown, and our work expands the known functions of LEU42 and PR26. Importantly, orf19.1766 and LEU42 have no human orthologues. Our results provide important clues as to basic mechanisms of survival in the presence of ECNs while identifying new genes controlling ECN susceptibility and revealing new targets for the development of novel antifungal drugs.

Immunomodulatory drug fingolimod (FTY720) restricts the growth of opportunistic yeast Candida albicans in vitro and in a mouse candidiasis model

Fingolimod (FTY720) is a drug derived from the fungicidal compound myriocin. As it was unclear whether FTY720 has antifungal effects as well, we aimed to characterize its effect on Candida albicans in vitro and in a mouse candidiasis model. First, antifungal susceptibility testing was performed in vitro. Then, a randomized, six-arm, parallel, open-label trial was conducted on 48 mice receiving oral FTY720 (0.3 mg/kg/day), intraperitoneal C. albicans inoculation, or placebo with different combinations and chorological patterns. The outcome measures of the trial included serum concentrations of interleukin-10 and interferon-gamma, absolute lymphocyte counts, and fungal burden values in the mice's livers, kidneys, and vaginas. Broth microdilution assay revealed FTY720's minimum inhibitory concentration (MIC99) to be 0.25 mg/mL for C. albicans. The infected mice treated with FTY720 showed lower fungal burden values than the ones not treated with FTY720 (p<0.05). As expected, the mice treated with FTY720 showed a less-inflammatory immune profile compared to the ones not treated with FTY720. We hypothesize that FTY720 synergizes the host's innate immune functions by inducing the production of reactive oxygen species. Further studies are warranted to unveil the mechanistic explanations of our observations and clarify further aspects of repurposing FTY720 for clinical antifungal usage.

The impact of COVID-19 on antimicrobial prescription and drug resistance in fungi and bacteria

Secondary infections are one of the complications in COVID-19 patients. We aimed to analyze the antimicrobial prescriptions and their influence on drug resistance in fungi and bacteria isolated from severely ill COVID-19 patients. Seventy-nine severely ill COVID-19 hospitalized patients with secondary bacterial or fungal infections were included. We analyzed the prescribed antimicrobial regimen for these patients and the resistance profiles of bacterial and fungal isolates. In addition, the association between drug resistance and patients’ outcome was analyzed using correlation tests. The most prescribed antibacterial were ceftriaxone (90.7% of patients), vancomycin (86.0%), polymyxin B (74.4%), azithromycin (69.8%), and meropenem (67.4%). Micafungin and fluconazole were used by 22.2 and 11.1% of patients, respectively. Multidrug-resistant (MDR) infections were a common complication in severely ill COVID-19 patients in our cohort since resistant bacteria strains were isolated from 76.7% of the patients. Oxacillin resistance was observed in most Gram-positive bacteria, whereas carbapenem and cephalosporin resistance was detected in most Gram-negative strains. Azole resistance was identified among C. glabrata and C. tropicalis isolates. Patients who used more antimicrobials stayed hospitalized longer than the others. The patient’s age and the number of antibacterial agents used were associated with the resistance phenotype. The susceptibility profile of isolates obtained from severely ill COVID-19 patients highlighted the importance of taking microbial resistance into account when managing these patients. The continuous surveillance of resistant/MDR infection and the rational use of antimicrobials are of utmost importance, especially for long-term hospitalized patients with COVID-19.

The Changing Landscape of Invasive Fungal Infections in ICUs: A Need for Risk Stratification to Better Target Antifungal Drugs and the Threat of Resistance

The landscape of invasive candidiasis and invasive aspergillosis has changed dramatically in intensive care units over the past two decades. Today, we are faced with new risk factors such as the emergence of resistance, but are also equipped with new therapeutic strategies and diagnostic tools which are changing epidemiological data and diagnostic algorithms. Some common points need to be addressed: (i) the best way to use microbiological tools and to integrate their results in decisional algorithms; (ii) the need to find the optimum balance between under-diagnosis and overtreatment; (iii) and the need to decipher pathophysiology. In this short review, we will try to illustrate these points.

The emerging role of neutrophil extracellular traps in fungal infection

Fungal infections are global public health problems and can lead to substantial human morbidity and mortality. Current antifungal therapy is not satisfactory, especially for invasive, life-threatening fungal infections. Modulating the antifungal capacity of the host immune system is a feasible way to combat fungal infections. Neutrophils are key components of the innate immune system that resist fungal pathogens by releasing reticular extracellular structures called neutrophil extracellular traps (NETs). When compared with phagocytosis and oxidative burst, NETs show better capability in terms of trapping large pathogens, such as fungi. This review will summarize interactions between fungal pathogens and NETs. Molecular mechanisms of fungi-induced NETs formation and defensive strategies used by fungi are also discussed.

How Yeast Antifungal Resistance Gene Analysis Is Essential to Validate Antifungal Susceptibility Testing Systems

Objectives

The antifungal susceptibility testing (AFST) of yeast pathogen alerts clinicians about the potential emergence of resistance. In this study, we compared two commercial microdilution AFST methods: Sensititre YeastOne read visually (YO) and MICRONAUT-AM read visually (MN) or spectrophotometrically (MNV), interpreted with Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing criteria, respectively.

Methods

Overall, 97 strains from 19 yeast species were measured for nine antifungal drugs including a total of 873 observations. First, the minimal inhibitory concentration (MIC) was compared between YO and MNV, and between MNV and MN, either directly or by assigning them to five susceptibility categories. Those categories were based on the number of MIC dilutions around the breakpoint or epidemiological cut-off reference values (ECOFFs or ECVs). Second, YO and MNV methods were evaluated for their ability to detect the elevation of MICs due to mutation in antifungal resistance genes, thanks to pairs or triplets of isogenic strains isolated from a single patient along a treatment previously analyzed for antifungal resistance gene mutations. Reproducibility measurement was evaluated, thanks to three quality control (QC) strains.

Results

YO and MNV direct MIC comparisons obtained a global agreement of 67%. Performing susceptibility category comparisons, only 22% and 49% of the MICs could be assigned to categories using breakpoints and ECOFFs/ECVs, respectively, and 40% could not be assigned due to the lack of criteria in both consortia. The YO and MN susceptibility categories gave accuracies as low as 50%, revealing the difficulty to implement this method of comparison. In contrast, using the antifungal resistance gene sequences as a gold standard, we demonstrated that both methods (YO and MN) were equally able to detect the acquisition of resistance in the Candida strains, even if MN showed a global lower MIC elevation than YO. Finally, no major differences in reproducibility were observed between the three AFST methods.

Conclusion

This study demonstrates the valuable use of both commercial microdilution AFST methods to detect antifungal resistance due to point mutations in antifungal resistance genes. We highlighted the difficulty to conduct conclusive analyses without antifungal gene sequence data as a gold standard. Indeed, MIC comparisons taking into account the consortia criteria of interpretation remain difficult even after the effort of harmonization.

Therapeutic Drug Monitoring of the Echinocandin Antifungal Agents: Is There a Role in Clinical Practice? A Position Statement of the Anti-Infective Drugs Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

PURPOSE

Reduced exposure to echinocandins has been reported in specific patient populations, such as critically ill patients; however, fixed dosing strategies are still used. The present review examines the accumulated evidence supporting echinocandin therapeutic drug monitoring (TDM) and summarizes available assays and sampling strategies.

METHODS

A literature search was conducted using PubMed in December 2020, with search terms such as echinocandins, anidulafungin, caspofungin, micafungin, or rezafungin with pharmacology, pharmacokinetics (PKs), pharmacodynamics (PDs), drug-drug interactions, TDM, resistance, drug susceptibility testing, toxicity, adverse drug reactions, bioanalysis, chromatography, and mass spectrometry. Data on PD/PD (PK/PD) outcome markers, drug resistance, PK variability, drug-drug interactions, assays, and TDM sampling strategies were summarized.

RESULTS

Echinocandins demonstrate drug exposure-efficacy relationships, and maximum concentration/minimal inhibitory concentration ratio (Cmax/MIC) and area under the concentration-time curve/MIC ratio (AUC/MIC) are proposed PK/PD markers for clinical response. The relationship between drug exposure and toxicity remains poorly clarified. TDM could be valuable in patients at risk of low drug exposure, such as those with critical illness and/or obesity. TDM of echinocandins may also be useful in patients with moderate liver impairment, drug-drug interactions, hypoalbuminemia, and those undergoing extracorporeal membrane oxygenation, as these conditions are associated with altered exposure to caspofungin and/or micafungin. Assays are available to measure anidulafungin, micafungin, and caspofungin concentrations. A limited-sampling strategy for anidulafungin has been reported.

CONCLUSIONS

Echinocandin TDM should be considered in patients at known risk of suboptimal drug exposure. However, for implementing TDM, clinical validation of PK/PD targets is needed.

Epidemiology and Antifungal Susceptibility Patterns of Invasive Fungal Infections (IFIs) in India: A Prospective Observational Study

The epidemiology of invasive fungal infections (IFI) is ever evolving. The aim of the present study was to analyze the clinical, microbiological, susceptibility, and outcome data of IFI in Indian patients to identify determinants of infection and 30-day mortality. Proven and probable/putative IFI (defined according to modified European Organization for Research and Treatment of Cancer/Mycoses Study Group and AspICU criteria) from April 2017 to December 2018 were evaluated in a prospective observational study. All recruited patients were antifungal naïve (n = 3300). There were 253 episodes of IFI (7.6%) with 134 (52.9%) proven and 119 (47%) probable/putative infections. There were four major clusters of infection: invasive candidiasis (IC) (n = 53, 20.9%), cryptococcosis (n = 34, 13.4%), invasive aspergillosis (IA) (n = 103, 40.7%), and mucormycosis (n = 62, 24.5%). The significant risk factors were high particulate efficiency air (HEPA) room admission, ICU admission, prolonged exposure to corticosteroids, diabetes mellitus, chronic liver disease (CLD), acquired immunodeficiency syndrome (AIDS), coronary arterial disease (CAD), trauma, and multiorgan involvement (p < 0.5; odds ratio: >1). The all-cause 30-day mortality was 43.4% (n = 110). It varied by fungal group: 52.8% (28/53) in IC, 58.8% (20/34) in cryptococcosis, 39.8% (41/103) in IA, and 33.9% (21/62) in mucormycosis. HEPA room, ICU admission for IC; HEPA rooms, diabetes mellitus for cryptococcosis; hematological malignancies, chronic kidney disease (CKD), sepsis, galactomannan antigen index value ≥1 for IA and nodules; and ground glass opacities on radiology for mucormycosis were significant predictors of death (odds ratio >1). High minimum inhibitory concentration (MIC) values for azoles were observed in C. albicans, C. parapsilosis, C. glabrata, A. fumigatus, A. flavus, R. arrhizus, R. microsporus, and M. circinelloides. For echinocandin, high MIC values were seen in C. tropicalis, C. guillermondii, C. glabrata, and A. fumigatus. This study highlights the shift in epidemiology and also raises concern of high MICs to azoles among our isolates. It warrants regular surveillance, which can provide the local clinically correlated microbiological data to clinicians and which might aid in guiding patient treatment.

Candidiasis by Candida glabrata, Candida nivariensis and Candida bracarensis in Galleria mellonella: Virulence and Therapeutic Responses to Echinocandins

Candida albicans is the major etiological agent of invasive candidiasis but the increasing prevalence of emerging species of Candida, such as Candida glabrata and phylogenetically closely related species, Candida nivariensis and Candida bracarensis, requires special attention. Differences in virulence among these species and their therapeutic responses using in vivo non-mammalian models are scarcely analysed. The aim of this study was analyse the survival of G. mellonella and host-pathogen interactions during infection by C. glabrata, C. nivariensis and C. bracarensis. Moreover, therapeutic responses to echinocandins were also assessed in the G. mellonella model of candidiasis. These three species produced lethal infection in G. mellonella; C. glabrata was the most virulent species and C. bracarensis the less. Haemocytes of G. mellonella phagocytised C. bracarensis cells more effectively than those of the other two species. Treatment with caspofungin and micafungin was most effective to protect larvae during C. glabrata and C. nivariensis infections while anidulafungin was during C. bracarensis infection. The model of candidiasis in G. mellonella is simple and appropriate to assess the virulence and therapeutic response of these emerging Candida species. Moreover, it successfully allows for detecting differences in the immune system of the host depending on the virulence of pathogens.

Trends of the Epidemiology of Candidemia in Switzerland: A 15-Year FUNGINOS Survey

Background

The increasing incidence of candidemia and emergence of drug-resistant Candida species are major concerns worldwide. Long-term surveillance studies are needed.

Methods

The Fungal Infection Network of Switzerland (FUNGINOS) conducted a 15-year (2004–2018), nationwide, epidemiological study of candidemia. Hospital-based incidence of candidemia, Candida species distribution, antifungal susceptibility, and consumption were stratified in 3 periods (2004–2008, 2009–2013, 2014–2018). Population-based incidence over the period 2009–2018 derived from the Swiss Antibiotic Resistance Surveillance System (ANRESIS).

Results

A total of 2273 Candida blood isolates were studied. Population and hospital-based annual incidence of candidemia increased from 2.96 to 4.20/100 000 inhabitants (P = .022) and 0.86 to 0.99/10 000 patient-days (P = .124), respectively. The proportion of Candida albicans decreased significantly from 60% to 53% (P = .0023), whereas Candida glabrata increased from 18% to 27% (P < .0001). Other non-albicans Candida species remained stable. Candida glabrata bloodstream infections occurred predominantly in the age group 18–40 and above 65 years. A higher proportional increase of C glabrata was recorded in wards (18% to 29%, P < .0001) versus intensive care units (19% to 24%, P = .22). According to Clinical and Laboratory Standards Institute, nonsusceptibility to fluconazole in C albicans was observed in 1% of isolates, and anidulafungin and micafungin nonsusceptibility was observed in 2% of C albicans and C glabrata. Fluconazole consumption, the most frequently used antifungal, remained stable, whereas use of mold-active triazoles and echinocandins increased significantly in the last decade (P < .0001).

Conclusions

Over the 15-year period, the incidence of candidemia increased. A species shift toward C glabrata was recently observed, concurring with increased consumption of mold-active triazoles.

Weekly high-dose liposomal amphotericin B prevents invasive aspergillosis after heart transplantation

BACKGROUND

Preventive strategies for invasive aspergillosis (IA) have still not been determined in heart transplant recipients whereas IA leads to a high mortality rate at 12 months posttransplantation. The use of voriconazole or echinocandins was proposed but can favor emergence of Aspergillus or Candida sp. resistant strains or promote neurological and liver disorders in some patients.

OBJECTIVES

To assess whether universal prophylaxis with weekly high-dose of liposomal amphotericin-B (L-AmB) can safely prevent IA in heart transplant recipients.

PATIENTS/METHODS

Retrospective before/after study that included 142 patients who received heart transplantation between 2010 and 2019 at the University Hospital of Toulouse (France). Weekly high dose of L-AmB (7.5 mg/kg/week) was used as universal prophylaxis from 2016 because of high environmental exposure to Aspergillus sp. and high incidence of IA.

RESULTS

Cumulative 1-year incidence of IA decreased from 23% to 5% after introduction of L-Amb prophylaxis. Multivariate analysis (Cox model) identified L-AmB prophylaxis as a protective factor against IA (hazard ratio [HR] 0.21 [95% confidence interval 0; 0.92], p = .04), whereas postoperative renal replacement therapy was associated with IA (HR 3.6 [95% confidence interval 1.38; 9.3], p = .001), after correction for confounding effects (induction regimen, methylprednisolone pulses and history of hematological malignancy). The incidence of acute kidney injury requiring renal replacement therapy was similar in the two groups, suggesting a low risk of kidney toxicity when L-AmB is used weekly. No patient developed severe kidney electrolyte loss nor L-AmB-related anaphylaxis.

CONCLUSIONS

Once-weekly high-dose L-AmB is safe and may prevent the development of IA after heart transplantation.

Candida glabrata Antifungal Resistance and Virulence Factors, a Perfect Pathogenic Combination

In recent years, a progressive increase in the incidence of invasive fungal infections (IFIs) caused by Candida glabrata has been observed. The objective of this literature review was to study the epidemiology, drug resistance, and virulence factors associated with the C. glabrata complex. For this purpose, a systematic review (January 2001-February 2021) was conducted on the PubMed, Scielo, and Cochrane search engines with the following terms: "C. glabrata complex (C. glabrata sensu stricto, C. nivariensis, C. bracarensis)" associated with "pathogenicity" or "epidemiology" or "antibiotics resistance" or "virulence factors" with language restrictions of English and Spanish. One hundred and ninety-nine articles were found during the search. Various mechanisms of drug resistance to azoles, polyenes, and echinocandins were found for the C. glabrata complex, depending on the geographical region. Among the mechanisms found are the overexpression of drug transporters, gene mutations that alter thermotolerance, the generation of hypervirulence due to increased adhesion factors, and modifications in vital enzymes that produce cell wall proteins that prevent the activity of drugs designed for its inhibition. In addition, it was observed that the C. glabrata complex has virulence factors such as the production of proteases, phospholipases, and hemolysins, and the formation of biofilms that allows the complex to evade the host immune response and generate fungal resistance. Because of this, the C. glabrata complex possesses a perfect pathogenetic combination for the invasion of the immunocompromised host.

Risk factors for isolation of fluconazole and echinocandin non-susceptible Candida species in critically ill patients

Introduction. Resistance rates to azoles and echinocandins of Candida spp. increased over the last decade.Hypothesis/Gap Statement. Widespread use of antifungals could lead to development and dissemination of resistant Candida spp.Aim. To identify risk factors for isolation of Candida spp. non-susceptible to either fluconazole or echinocandins.Methodology. All patients hospitalized in the Intensive Care Unit (ICU) of the University General Hospital of Patras, Greece with Candida spp. isolated from clinical specimens during a ten-year period (2010-19) were included. Candida isolates were identified using Vitek-2 YST card. Consumption of antifungals was calculated.Results. During the study period, 253 isolates were included. C. non-albicans predominated (64.4 %) with C. parapsilosis being the most commonly isolated (42.3 %) followed by C. glabrata (nomenclatural change to Nakaseomyces glabrataa; 8.7 %) and C. tropicalis (11.9 %). Among all isolates, 45.8 and 28.5 % were non-susceptible and resistant to fluconazole, respectively. Concerning echinocandins, 8.7 % of isolates were non-susceptible to at least one echinocandin (anidulafungin or micafungin) and 3.1 % resistant. Multivariate analysis revealed that hospitalization during 2015-19, as compared to 2010-14, isolate being non-albicans or non-susceptible to at least one echinocandin was associated with isolation of fluconazole non-susceptible isolate. Administration of echinocandin, isolate being C. glabrata or C. tropicalis, or Candida spp. non-susceptible to fluconazole were independently associated with isolation of Candida spp. non-susceptible to at least one echinocandin. Fluconazole's administration decreased during the study period, whereas liposomal-amphotericin B's and echinoncandins' administration remained stable.Conclusion. Fluconazole's non-susceptibility increased during the study period, despite the decrease of its administration. Although echinocandins' administration remained stable, non-susceptibility among Candida spp. increased.

Host Age and Denture Wearing Jointly Contribute to Oral Colonization with Intrinsically Azole-Resistant Yeasts in the Elderly

In elderly patients, several morbidities or medical treatments predisposing for fungal infections occur at a higher frequency, leading to high mortality and morbidity in this vulnerable patient group. Often, this is linked to an innately azole-resistant yeast species such as Candida glabrata or C. krusei. Additionally, host age per se and the wearing of dentures have been determined to influence the mix of colonizing species and, consequently, the species distribution of invasive fungal infections. Since both old age and the wearing of dentures are two tightly connected parameters, it is still unclear which of them is the main contributor. Here, we performed a cross-sectional study on a cohort (N = 274) derived from three groups of healthy elderly, diseased elderly, and healthy young controls. With increasing host age, the frequency of oral colonization by a non-albicans Candida species, mainly by C. glabrata, also increased, and the wearing of dentures predisposed for colonization by C. glabrata irrespectively of host age. Physically diseased hosts, on the other hand, were more frequently orally colonized by C. albicans than by other yeasts. For both C. albicans and C. glabrata, isolates from the oral cavity did not generally display an elevated biofilm formation capacity. In conclusion, intrinsically azole-drug-resistant, non-albicans Candida yeasts are more frequent in the oral cavities of the elderly, and fungal cells not contained in biofilms may predispose for subsequent systemic infection with these organisms. This warrants further exploration of diagnostic procedures, e.g., before undergoing elective abdominal surgery or when using indwelling devices on this patient group.

Deciphering the epidemiology of invasive candidiasis in the intensive care unit: is it possible?

Invasive candidiasis (IC) has emerged in the last decades as an important cause of morbidity, mortality, and economic load in the intensive care unit (ICU). The epidemiology of IC is still a difficult and unsolved enigma for the literature. Accurate estimation of the true burden of IC is difficult due to variation in definitions and limitations inherent to available case-finding methodologies. Candidemia and intra-abdominal candidiasis (IAC) are the two predominant types of IC in ICU. During the last two decades, an increase in the incidence of candidemia has been constantly reported particularly in the expanding populations of elderly or immunosuppressed patents, with a parallel change in Candida species (spp.) distribution worldwide. Epidemiological shift in non-albicans spp. has reached worrisome trends. Recently, a novel, multidrug-resistant Candida spp., Candida auris, has globally emerged as a nosocomial pathogen causing a broad range of healthcare-associated invasive infections. Epidemiological profile of IAC remains imprecise. Though antifungal drugs are available for Candida infections, mortality rates continue to be high, estimated to be up to 50%. Increased use of fluconazole and echinocandins has been associated with the emergence of resistance to these drugs, which affects particularly C. albicans and C. glabrata. Crucial priorities for clinicians are to recognize the epidemiological trends of IC as well as the emergence of resistance to antifungal agents to improve diagnostic techniques and strategies, develop international surveillance networks and antifungal stewardship programmes for a better epidemiological control of IC.

Proteomic Analysis of Caspofungin-Induced Responses in Planktonic Cells and Biofilms of Candida albicans

Candida albicans biofilms display markedly increased antifungal resistance, and the underlying mechanisms remain unclear. This study investigated the signature profiles of C. albicans planktonic cells and biofilms in response to caspofungin (CAS) by mass spectrometry-based shotgun proteomics. We found that C. albicans biofilms were twofold more resistant to CAS with reference to planktonic cells. Notably, 9.6% of C. albicans biofilm cells survived the lethal treatment of CAS (128 μg/ml), confirmed by LIVE/DEAD staining, confocal laser scanning microscopy (CLSM) and scanning electron microscopy analyses. The responses of C. albicans planktonic cells and biofilms to CAS treatment at respective minimum inhibitory concentrations (MICs) were assessed by high-throughput proteomics and bioinformatics approaches. There were 148 and 224 proteins with >twofold difference identified from the planktonic cells and biofilms, respectively. CAS treatment downregulated several cell wall- and oxidative stress-related proteins. Whereas, CAS-induced action was compensated by markedly increased expression of many other proteins involved in cell wall integrity and stress response (e.g., heat shock proteins). Moreover, considerable expression changes were identified in metabolism-associated proteins like glycolysis, tricarboxylic acid (TCA) cycle and ATP biosynthesis. Importantly, various key proteins for cell wall integrity, stress response and metabolic regulation (e.g., PIL1, LSP1, HSP90, ICL1, and MLS1) were exclusively enriched and implicated in C. albicans biofilms. This study demonstrates that C. albicans biofilms undergo highly complicated yet complex regulation of multiple cellular pathways in response to CAS. Signature proteins essential for modulating cell wall integrity, stress response and metabolic activities may account for the antifungal resistance of C. albicans biofilms.

Role and Interpretation of Antifungal Susceptibility Testing for the Management of Invasive Fungal Infections

Invasive fungal infections (IFIs) are associated with high mortality rates and timely appropriate antifungal therapy is essential for good outcomes. Emerging antifungal resistance among Candida and Aspergillus spp., the major causes of IFI, is concerning and has led to the increasing incorporation of in vitro antifungal susceptibility testing (AST) to guide clinical decisions. However, the interpretation of AST results and their contribution to management of IFIs remains a matter of debate. Specifically, the utility of AST is limited by the delay in obtaining results and the lack of pharmacodynamic correlation between minimal inhibitory concentration (MIC) values and clinical outcome, particularly for molds. Clinical breakpoints for Candida spp. have been substantially revised over time and appear to be reliable for the detection of azole and echinocandin resistance and for outcome prediction, especially for non-neutropenic patients with candidemia. However, data are lacking for neutropenic patients with invasive candidiasis and some non-albicans Candida spp. (notably emerging Candida auris). For Aspergillus spp., AST is not routinely performed, but may be indicated according to the epidemiological context in the setting of emerging azole resistance among A. fumigatus. For non-Aspergillus molds (e.g., Mucorales, Fusarium or Scedosporium spp.), AST is not routinely recommended as interpretive criteria are lacking and many confounders, mainly host factors, seem to play a predominant role in responses to antifungal therapy. This review provides an overview of the pre-clinical and clinical pharmacodynamic data, which constitute the rationale for the use and interpretation of AST testing of yeasts and molds in clinical practice.