Caspofungin-resistance in Candida auris is cell wall-dependent phenotype and potential prevention by zinc oxide nanoparticles

Uniqueness of Candida auris cell wall in morphogenesis, virulence, resistance, and immune evasion

Candida auris has drawn global attention due to its alarming multidrug resistance and the emergence of pan resistant strains. C. auris poses a significant risk in nosocomial candidemia especially among immunocompromised patients. C. auris showed unique virulence characteristics associated with cell wall including cell polymorphism, adaptation, endurance on inanimate surfaces, tolerance to external conditions, and immune evasion. Notably, it possesses a distinctive cell wall composition, with an outer mannan layer shielding the inner 1,3-β glucan from immune recognition, thereby enabling immune evasion and drug resistance. This review aimed to comprehend the association between unique characteristics of C. auris's cell wall and virulence, resistance mechanisms, and immune evasion. This is particularly relevant since the fungal cell wall has no human homology, providing a potential therapeutic target. Understanding the complex interactions between the cell wall and the host immune system is essential for devising effective treatment strategies, such as the use of repurposed medications, novel therapeutic agents, and immunotherapy like monoclonal antibodies. This therapeutic targeting strategy of C. auris holds promise for effective eradication of this resilient pathogen.

Decoding host cell interaction- and fluconazole-induced metabolic alterations and drug resistance in Candida auris

Candida auris is an emerging drug-resistant pathogen associated with high mortality rates. This study aimed to explore the metabolic alterations and associated pathogenesis and drug resistance in fluconazole-treated Candida auris-host cell interaction. Compared with controls, secreted metabolites from fluconazole-treated C. auris and fluconazole-treated C. auris-host cell co-culture demonstrated notable anti-Candida activity. Fluconazole caused significant reductions in C. auris cell numbers and aggregated phenotype. Metabolites produced by C. auris with potential fungal colonization, invasion, and host immune evasion effects were identified. Metabolites known to enhance biofilm formation produced during C. auris-host cell interaction were inhibited by fluconazole. Fluconazole enhanced the production of metabolites with biofilm inhibition activity, including behenyl alcohol and decanoic acid. Metabolites with potential Candida growth inhibition activity such as 2-palmitoyl glycerol, 1-tetradecanol, and 1-nonadecene were activated by fluconazole. Different patterns of proinflammatory cytokine expression presented due to fluconazole concentration and host cell type (fibroblasts versus macrophages). This highlights the immune response's complexity, emphasizing the necessity for additional research to comprehend cell-type-specific responses to antifungal therapies. Both host cell interaction and fluconazole treatment increased the expression of CDR1 and ERG11 genes, both associated with drug resistance. This study provides insights into pathogenesis in C. auris due to host cell interaction and fluconazole treatment. Understanding these interactions is crucial for enhancing fluconazole sensitivity and effectively combating C. auris.

Chitinase-functionalized UiO-66 framework nanoparticles active against multidrug-resistant Candida Auris

Candida auris (C. auris) is a yeast that has caused several outbreaks in the last decade. Cell wall chitin plays a primary role in the antifungal resistance of C. auris. Herein, we investigated the potential of chitinase immobilized with UiO-66 to act as a potent antifungal agent against C. auris. Chitinase was produced from Talaromyces varians SSW3 in a yield of 8.97 U/g dry substrate (ds). The yield was statistically enhanced to 120.41 U/g ds by using Plackett-Burman and Box-Behnken design. We synthesized a UiO-66 framework that was characterized by SEM, TEM, XRD, FTIR, a particle size analyzer, and a zeta sizer. The produced framework had a size of 70.42 ± 8.43 nm with a uniform cubic shape and smooth surface. The produced chitinase was immobilized on UiO-66 with an immobilization yield of 65% achieved after a 6 h loading period. The immobilization of UiO-66 increased the enzyme activity and stability, as indicated by the obtained Kd and T1/2 values. Furthermore, the hydrolytic activity of chitinase was enhanced after immobilization on UiO-66, with an increase in the Vmax and a decrease in the Km of 2- and 38-fold, respectively. Interestingly, the antifungal activity of the produced chitinase was boosted against C. auris by loading the enzyme on UiO-66, with an MIC50 of 0.89 ± 0.056 U/mL, compared to 5.582 ± 0.57 U/mL for the free enzyme. This study offers a novel promising alternative approach to combat the new emerging pathogen C. auris.

Transcriptome Analysis of Human Dermal Cells Infected with Candida auris Identified Unique Pathogenesis/Defensive Mechanisms Particularly Ferroptosis

Candida auris is an emerging multi-drug resistant yeast that can cause life-threatening infections. A recent report clarified the ability of C. auris to form a biofilm with enhanced drug resistance properties in the host skin's deep layers. The formed biofilm may initiate further bloodstream spread and immune escape. Therefore, we propose that secreted chemicals from the biofilm may facilitate fungal pathogenesis. In response to this interaction, the host skin may develop potential defensive mechanisms. Comparative transcriptomics was performed on the host dermal cells in response to indirect interaction with C. auris biofilm through Transwell inserts compared to planktonic cells. Furthermore, the effect of antifungals including caspofungin and fluconazole was studied. The obtained data showed that the dermal cells exhibited different transcriptional responses. Kyoto Encyclopedia of Genes and Genomes and Reactome analyses identified potential defensive responses employed by the dermal cells and potential toxicity induced by C. auris. Additionally, our data indicated that the dominating toxic effect was mediated by ferroptosis; which was validated by qRT-PCR, cytotoxicity assay, and flow cytometry. On the other hand, the viability of C. auris biofilm was enhanced and accompanied by upregulation of MDR1, and KRE6 upon interaction with dermal cells; both genes play significant roles in drug resistance and biofilm maturation, respectively. This study for the first-time shed light on the dominating defensive responses of human dermal cells, microbe colonization site, to C. auris biofilm and its toxic effects. Further, it demonstrates how C. auris biofilm responds to the defensive mechanisms developed by the human dermal cells.

Current Perspectives of Antifungal Therapy: A Special Focus on Candida auris

Candida auris is an emerging Candida sp. that has rapidly spread all over the world. The evidence regarding its origin and emerging resistance is still unclear. The severe infection caused by this species results in significant mortality and morbidity among the elderly and immunocompromised individuals. The development of drug resistance is the major factor associated with the therapeutic failure of existing antifungal agents. Previous studies have addressed the antifungal resistance profile and drug discovery for C. auris. However, complete coverage of this information in a single investigation is not yet available. In this review, we have mainly focused on recent developments in therapeutic strategies against C. auris. Based on the available information, several different approaches were discussed, including existing antifungal drugs, chemical compounds, essential oils, natural products, antifungal peptides, immunotherapy, antimicrobial photodynamic therapy, drug repurposing, and drug delivery systems. Among them, synthetic chemicals, natural products, and antifungal peptides are the prime contributors. However, a limited number of resources are available to prove the efficiency of these potential therapies in clinical usage. Therefore, we anticipate that the findings gathered in this review will encourage further in vivo studies and clinical trials.

The many faces of Candida auris: Phenotypic and strain variation in an emerging pathogen

Candida auris is an emerging fungal pathogen with unusual evolutionary history-there are multiple distinct phylogeographic clades showing a near simultaneous transition from a currently unknown reservoir to nosocomial pathogen. Each of these clades has experienced different selective pressures over time, likely resulting in selection for genotypes with differential fitness or phenotypic consequences when introduced to new environments. We also observe diversification within clades, providing additional opportunities for phenotypic differences. These differences can have large impacts on pathogenic potential, drug resistance profile, evolutionary trajectory, and transmissibility. In recent years, there have been significant advances in our understanding of strain-specific behavior in other microbes, including bacterial and fungal pathogens, and we have an opportunity to take this strain variation into account when describing aspects of C. auris biology. Here, we critically review the literature to gain insight into differences at both the strain and clade levels in C. auris, focusing on phenotypes associated with clinical disease or transmission. Our goal is to integrate clinical and epidemiological perspectives with molecular perspectives in a way that would be valuable for both audiences. Identifying differences between strains and understanding which phenotypes are strain specific will be crucial for understanding this emerging pathogen, and an important caveat when describing the analysis of a singular isolate.

Enhanced antimicrobial efficacy of biogenic ZnO nanoparticles through UV-B activation: A novel approach for textile garment

Zinc oxide nanoparticles (ZnO NP) are characterized by novel properties which have been attracting the attention of different lines of research due to their wide applicability. Obtaining this nanomaterial is strongly linked to biogenic synthesis methods, which have also been developed in this research, using Coriandrum sativum extract as a reducing agent. ZnO NPs have been properly characterized by techniques to evaluate their morphology by transmission electron microscopy (TEM) and elemental analysis by EDX. The evaluation of the antimicrobial and antifungal effects is linked to the use of a system provided by "locker sanitizer" equipment, which has been designed and built as part of this research, and is intended to treat textile garments by nebulizing the ZnO NP colloid (99.08 μg/mL) + UV-B, water + UV-B, and UV-B only, and also to evaluate the influence of the treatment time for 1, 2 and 3 min. In this sense, it is known that the nanomaterial used shows a better response to UV light because more hydroxyl radicals are produced, leading to a higher reaction rate, which results in greater efficiency in inhibitory processes. The results show that the use of the locker sanitizer is more efficient when using ZnO NP + UV-B light since it achieved 100 % growth inhibition against E. coli, C. albicans, and A. brasiliensis, and >99 % against S. aureus, after 3 min of treatment.

Co-administration of amoxicillin-loaded chitosan nanoparticles and inulin: A novel strategy for mitigating antibiotic resistance and preserving microbiota balance in Helicobacter pylori treatment

Helicobacter pylori (H. pylori) is a causative agent of various gastrointestinal diseases and eradication mainly relies on antibiotic treatment, with (AMX) being a key component. However, rising antibiotic resistance in H. pylori necessitates the use of antibiotics combination therapy, often disrupting gut microbiota equilibrium leading to further health complications. This study investigates a novel strategy utilizing AMX-loaded chitosan nanoparticles (AMX-CS NPs), co-administered with prebiotic inulin to counteract H. pylori infection while preserving microbiota health. Following microbroth dilution method, AMX displayed efficacy against H. pylori, with a MIC50 of 48.34 ± 3.3 ng/mL, albeit with a detrimental impact on Lactobacillus casei (L. casei). The co-administration of inulin (500 μg/mL) with AMX restored L. casei viability while retaining the lethal effect on H. pylori. Encapsulation of AMX in CS-NPs via ionic gelation method, resulted in particles of 157.8 ± 3.85 nm in size and an entrapment efficiency (EE) of 86.44 ± 2.19 %. Moreover, AMX-CS NPs showed a sustained drug release pattern over 72 h with no detectable toxicity on human dermal fibroblasts cell lines. Encapsulation of AMX into CS NPs also reduced its MIC50 against H. pylori, while its co-administration with inulin maintained L. casei viability. Interestingly, treatment with AMX-CS NPs also reduced the expression of the efflux pump gene hefA in H. pylori. This dual treatment strategy offers a promising approach for more selective antimicrobial treatment, minimizing disruption to healthy microbial communities while effectively addressing pathogenic threats.

Global characteristics and trends in research on Candida auris

Introduction

Candida auris, a fungal pathogen first reported in 2009, has shown strong resistance to azole antifungal drugs and has caused severe nosocomial outbreaks. It can also form biofilms, which can colonize patients' skin and transmit to others. Despite numerous reports of C. auris isolation in various countries, many studies have reported contradictory results.

Method

A bibliometric analysis was conducted using VOSviewer to summarize research trends and provide guidance for future research on controlling C. auris infection. The analysis revealed that the United States and the US CDC were the most influential countries and research institutions, respectively. For the researchers, Jacques F. Meis published the highest amount of related articles, and Anastasia P. Litvintseva's articles with the highest average citation rate. The most cited publications focused on clade classification, accurate identification technologies, nosocomial outbreaks, drug resistance, and biofilm formation. Keyword co-occurrence analysis revealed that the top five highest frequencies were for 'drug resistance,' 'antifungal susceptibility test,' 'infection,' 'Candida auris,' and 'identification.' The high-frequency keywords clustered into four groups: rapid and precise identification, drug resistance research, pathogenicity, and nosocomial transmission epidemiology studies. These clusters represent different study fields and current research hotspots of C. auris.

Conclusion

The bibliometric analysis identified the most influential country, research institution, and researcher, indicating current research trends and hotspots for controlling C. auris.

Identification of Molecular and Genetic Resistance Mechanisms in a Candida auris Isolate in a Tertiary Care Center in Türkiye

BACKGROUND

Candida auris is a multidrug-resistant pathogen that causes nosocomial outbreaks and high mortality. We conducted this study to investigate the molecular mechanisms of antifungal resistance in our clinical isolate of C. auris with a high level of resistance to three main classes of antifungals.

MATERIAL AND METHODS

A clinical C. auris isolate was identified by MALDI-TOF MS and antifungal susceptibilities were determined by the Sensititre YeastOne YO10 panel. After sequencing the whole genome of the microorganism with Oxford Nanopore NGS Technologies, a phylogenetic tree was drawn as a cladogram to detect where the C. auris clade to this study's assembly belongs.

RESULTS

The C. auris isolate in this study (MaCa01) was determined to be a part of the clade I (South Asian). The resistance-related genes indicated that MaCa01 would most likely be highly resistant to fluconazole (CDR1, TAC1b, and ERG11), none or little resistant to amphotericin B (AmpB) and echinocandins, and sensitive to flucytosine. The mutations found in the above-mentioned genes in the Türkiye C. auris isolate reveals an antifungal resistance pattern. This molecular resistance pattern was found consistent with the interpretation of MIC values of the antifungals according to CDC tentative breakpoints.

CONCLUSION

We detected the well-known antifungal resistance mutations, responsible for azole resistance in C. auris. Despite no ERG2, ERG6, and FKS mutation identified, the isolate was found to be resistant to AmpB and caspofungin based on the CDC tentative breakpoints which could be related to unidentified mutations.

Nanotechnology-Based Strategies to Combat Multidrug-Resistant Candida auris Infections

An emerging multidrug-resistant pathogenic yeast called Candida auris has a high potential to spread quickly among hospitalized patients and immunodeficient patients causing nosocomial outbreaks. It has the potential to cause pandemic outbreaks in about 45 nations with high mortality rates. Additionally, the fungus has become resistant to decontamination techniques and can survive for weeks in a hospital environment. Nanoparticles might be a good substitute to treat illnesses brought on by this newly discovered pathogen. Nanoparticles have become a trend and hot topic in recent years to combat this fatal fungus. This review gives a general insight into the epidemiology of C. auris and infection. It discusses the current conventional therapy and mechanism of resistance development. Furthermore, it focuses on nanoparticles, their different types, and up-to-date trials to evaluate the promising efficacy of nanoparticles with respect to C. auris.

Intra-clade Heterogeneity in Candida auris: Risk of Management

Candida auris has emerged as a significant nosocomial fungal pathogen with a high risk of pathogenicity. Since the initial detection of C. auris in 2009, it gained lots of attention with a recent alert by the Centers for Disease Control and Prevention (CDC) due to its high infectivity and drug resistance. Several studies showed the capability of C. auris to secrete lytic enzymes, germinate, and form a biofilm that eventually results in interactions with the host cells, leading to serious infections. Other studies demonstrated a decrease in susceptibility of C. auris strains to available antifungals, which may be caused by mutations within the target genes, or the drug efflux pumps. However, the contribution of C. auris heterogeneity in pathogenicity and drug resistance is not well studied. Here, we shed light on the factors contributing to the development of heterogeneity in C. auris. These include phenotypic changes, biofilm formation, mechanisms of drug resistance, host invasion, mode of transmission, and expression of virulence factors. C. auris exhibits different phenotypes, particularly aggregative, and non-aggregative forms that play an important role in fungal heterogeneity, which significantly affects drug resistance and pathogenicity. Collectively, heterogeneity in C. auris significantly contributes to ineffective treatment, which in turn affects the fungal pathogenicity and drug resistance. Therefore, understanding the underlying reasons for C. auris heterogeneity and applying effective antifungal stewardship could play a major role in controlling this pathogen.

Peptide-functionalized zinc oxide nanoparticles for the selective targeting of breast cancer expressing placenta-specific protein 1

Functionalized metal oxide nanoparticles (NPs) have demonstrated specific binding affinity to antigens or receptors presented on the cancer cell surface, favouring selective targeting and minimizing side effects during the chemotherapy. Placenta-specific protein 1 (PLAC-1) is a small cell surface protein overexpressed in certain types of breast cancer (BC); therefore, it can be used as a therapeutic target. The objective of this study is to develop NPs that can bind PLAC-1 and hence can inhibit the progression and metastatic potential of BC cells. Zinc oxide (ZnO) NPs were coated with a peptide (GILGFVFTL), which possesses a strong binding ability to PLAC-1. The physical attachment of the peptide to ZnO NPs was verified through various physicochemical and morphological characterization techniques. The selective cytotoxicity of the designed NPs was investigated using PLAC-1-bearing MDA-MB 231 human BC cell line and compared to LS-180 cells that do not express PLAC-1. The anti-metastatic and pro-apoptotic effects of the functionalized NPs on MDA-MB 231 cells were examined. Confocal microscopy was used to investigate the mechanism of NPs uptake by MDA-MB 231 cells. Compared to non-functionalized NPs, peptide functionalization significantly improved the targeting and uptake of the designed NPs by PLAC-1-expressing cancer cells with significant pro-apoptotic and anti-metastatic effects. The uptake of peptide functionalized ZnO NPs (ZnO-P NPs) occurred via peptide-PLAC1 interaction-assisted clathrin-mediated endocytosis. These findings highlight the potential targeted therapy of ZnO-P NPs against PLAC-1-expressing breast cancer cells.

Strategies to Prevent Transmission of Candida auris in Healthcare Settings

Purpose of Review

Candida auris, a recently recognized yeast pathogen, has become a major public health threat due to the problems associated with its accurate identification, intrinsic and acquired resistance to antifungal drugs, and its potential to easily contaminate the environment causing clonal outbreaks in healthcare facilities. These outbreaks are associated with high mortality rates particularly among older patients with multiple comorbidities under intensive care settings. The purpose of this review is to highlight strategies that are being adapted to prevent transmission of C. auris in healthcare settings.

Recent Findings

Colonized patients shed C. auris into their environment which contaminates surrounding equipment. It resists elimination even by robust decontamination procedures and is easily transmitted to new patients during close contact resulting in outbreaks. Efforts are being made to rapidly identify C. auris-infected/C. auris-colonized patients, to determine its susceptibility to antifungals, and to perform effective cleaning and decontamination of the environment and isolation of colonized patients to prevent further transmission.

Summary

Rapid and accurate identification of hospitalized patients infected/colonized with C. auris, rapid detection of its susceptibility patterns, and appropriate use of infection control measures can help to contain the spread of this highly pathogenic yeast in healthcare settings and prevent/control outbreaks.

Transcriptomics and Phenotyping Define Genetic Signatures Associated with Echinocandin Resistance in Candida auris

Candida auris emerged as a human fungal pathogen only during the past decade. Remarkably, C. auris displays high degrees of genomic diversity and phenotypic plasticity, with four major clades causing hospital outbreaks with high mortality and morbidity rates. C. auris can show clinical resistance to all classes of antifungal drugs, including echinocandins that are usually recommended as first-line therapies for invasive candidiasis. Here, we exploit transcriptomics coupled with phenotypic profiling to characterize a set of clinical C. auris isolates displaying pronounced echinocandin resistance (ECN-R). A hot spot mutation in the echinocandin FKS1 target gene is present in all resistant isolates. Moreover, ECN-R strains share a core signature set of 362 genes differentially expressed in ECN-R isolates. Among others, mitochondrial gene expression and genes affecting cell wall function appear to be the most prominent, with the latter correlating well with enhanced adhesive traits, increased cell wall mannan content, and altered sensitivity to cell wall stress of ECN-R isolates. Moreover, ECN-R phenotypic signatures were also linked to pathogen recognition and interaction with immune cells. Hence, transcriptomics paired with phenotyping is a suitable tool to predict resistance and fitness traits as well as treatment outcomes in pathogen populations with complex phenotypic diversity. IMPORTANCE The surge in antimicrobial drug resistance in some bacterial and fungal pathogens constitutes a significant challenge to health care facilities. The emerging human fungal pathogen Candida auris has been particularly concerning, as isolates can display pan-antifungal resistance traits against all drugs, including echinocandins. However, the mechanisms underlying this phenotypic diversity remain poorly understood. We identify transcriptomic signatures in C. auris isolates resistant to otherwise fungicidal echinocandins. We identify a set of differentially expressed genes shared by resistant strains compared to unrelated susceptible isolates. Moreover, phenotyping demonstrates that resistant strains show distinct behaviors, with implications for host-pathogen interactions. Hence, this work provides a solid basis to identify the mechanistic links between antifungal multidrug resistance and fitness costs that affect the interaction of C. auris with host immune defenses.

Farnesol Boosts the Antifungal Effect of Fluconazole and Modulates Resistance in Candida auris through Regulation of the CDR1 and ERG11 Genes

Candida auris is considered a serious fungal pathogen frequently exhibiting a high resistance to a wide range of antifungals. In this study, a combination of the quorum-sensing molecule farnesol (FAR) and fluconazole (FLU) was tested on FLU-resistant C. auris isolates (C. auris S and C. auris R) compared to the susceptible C. auris H261. The aim was to assess the possible synergy between FAR and FLU, by reducing the FLU minimal inhibitory concentration, and to determine the mechanism underlying the conjunct effect. The results confirmed a synergic effect between FAR and FLU with a calculated FIC index of 0.75 and 0.4 for C. auris S and C. auris R, respectively. FAR modulates genes involved in azole resistance. When FAR was added to the cells in combination with FLU, a significant decrease in the expression of the CDR1 gene was observed in the resistant C. auris isolates. FAR seems to block the Cdr1 efflux pump triggering a restoration of the intracellular content of FLU. These results were supported by observed increasing accumulation of rhodamine 6G by C. auris cells. Moreover, C. auris treated with FAR showed an ERG11 gene down-regulation. Overall, these results suggest that FAR is an effective modulator of the Cdr1 efflux pump in C. auris and, in combination with FLU, enhances the activity of this azole, which might be a promising strategy to control infections caused by azole-resistant C. auris.