Antifungal Resistance: An Emerging Reality and A Global Challenge

Unravelling fungal pathogenesis: Advances in CRISPR-Cas9 for understanding virulence and adaptation

Fungi, with their billion-year evolutionary history, have adapted to diverse ecological niches, including pathogenic roles that threaten global health, agriculture, and ecosystems. Fungal pathogenicity is shaped by the dynamic evolution of genetic traits that enable fungi to infect hosts, evade immune defenses, and develop resistance to antifungal treatments. Despite their significant clinical and ecological impact, the evolutionary processes underlying fungal virulence and adaptation remain incompletely understood. This review emphasizes the transformative role of CRISPR-Cas9 genome editing in revealing these mechanisms. By allowing precise manipulation of fungal genomes, CRISPR technologies have provided key insights into virulence factors, stress response mechanisms, immune evasion, and antifungal resistance pathways. These advances demonstrate how fungi adapt to selective pressures, repurpose conserved genetic pathways, and exploit genomic plasticity to thrive in host environments. This review explores the intersection of CRISPR technology and fungal biology, shedding light on its implications for understanding fungal pathogenesis and the potential to develop innovative therapeutic strategies against fungal infections. The integration of CRISPR applications into mycology holds promise for furthering our understanding of fungal evolutionary trajectories and enhancing the development of novel therapeutic approaches.

Novel 2-Thiazolylhydrazone with Druggable Properties for Antifungal Application

Fungal infections have become a growing concern in healthcare, particularly in immunocompromised individuals, with species like Candida, Cryptococcus, and Sporothrix posing significant challenges due to rising resistance and limited treatment options. In response, novel antifungal agents are being explored, including thiazolyl hydrazones. This study focuses on the development of a novel thiazolylhydrazone derivative, RW3. RW3 was synthesized to improve its water solubility and pharmacokinetic properties. The compound demonstrated a broad antifungal spectrum, particularly effective against Cryptococcus neoformans and Candida auris, with minimal irritant potential and low cytotoxicity. RW3 showed favorable solubility and high intestinal permeability, indicating potential for oral administration. The results suggest RW3 as a promising lead for further development as a therapeutic agent for systemic fungal infections. These findings underscore the importance of optimizing drug properties to enhance efficacy and safety profiles, opening the path for the development of innovative antifungal treatments.

Antifungal properties of abnormal cannabinoid derivatives: Disruption of biofilm formation and gene expression in Candida species

Abnormal cannabinoids (including comp 3) are a class of synthetic lipid compounds with non-psychoactive properties and regioisomer configurations, but distinct from traditional cannabinoids since they do not interact with the established CB1 and CB2 receptors. Previous research showed the cardioprotective and anti-inflammatory potentials of comp 3 and more recently its antimicrobial effect on methicillin-resistant Staphylococcus aureus (MRSA). Given the escalating challenges posed by Candida infections and the rise of antifungal drug resistance, the exploration of novel therapeutic avenues is crucial. This study aimed to assess the anti-Candida properties of newly synthesized AbnCBD derivatives. AbnCBD derivatives were synthesized by acid catalysis-induced coupling and further derivatized. We evaluated the potential of the AbnCBD derivatives to inhibit the growth stages of various Candida species. By in vitro colorimetric assays and in vivo mice experiments, we have shown that AbnCBD derivatives induce differential inhibition of Candida growth. The AbnCBD derivatives, especially comp 3, comp 10, and comp 9 significantly reduced the growth of C. albicans, including FLC-resistant strains, and of C. tropicalis and C. parapsilosis but not of C auris compared to their controls (FLC and 0.5 % DMSO). Comp 3 also disrupted C. albicans biofilm formation and eradicated mature biofilms. Notably, other derivatives of AbnCBD disrupted the biofilm formation and maturation of C. albicans but did not affect yeast growth. In a murine model of VVC, comp 3 demonstrated significant fungal clearance and reduced C. albicans burden compared to vehicle and FLC controls. These findings highlight the potential of AbnCBDs as promising antifungal agents against Candida infections.

Affinity molecular assay for detecting Candida albicans using chitin affinity and RPA-CRISPR/Cas12a

Invasive fungal infections (IFIs) pose a significant threat to immunocompromised individuals, leading to considerable morbidity and mortality. Prompt and accurate diagnosis is essential for effective treatment. Here we develop a rapid molecular diagnostic method that involves three steps: fungal enrichment using affinity-magnetic separation (AMS), genomic DNA extraction with silicon hydroxyl magnetic beads, and detection through a one-pot system. This method, optimized to detect 30 CFU/mL of C. albicans in blood and bronchoalveolar lavage (BAL) samples within 2.5 h, is approximately 100 times more sensitive than microscopy-based staining. Initial validation using clinical samples showed 93.93% sensitivity, 100% specificity, and high predictive values, while simulated tests demonstrated 95% sensitivity and 100% specificity. This cost-effective, highly sensitive technique offers potential for use in resource-limited clinical settings and can be easily adapted to differentiate between fungal species and detect drug resistance.

Evaluation of resistance patterns and bioremoval efficiency of hydrocarbons and heavy metals by the mycobiome of petroleum refining wastewater in Jazan with assessment of molecular typing and cytotoxicity of Scedosporium apiospermum JAZ-20

Jazan Industrial Economic City (JIEC) is located on the Red Sea coast in the province of Jazan, southwest of Saudi Arabia anchors diverse heavy and secondary industries in the energy, water desalination, petroleum, aluminum, copper, refineries, pharmaceuticals and food manufacturing fields. These various industries generate a large quantity of industrial wastewaters containing various toxicants. The present work represents ecologically beneficial alternatives for the advancement of environmental biotechnology, which could help mitigate the adverse impacts of environmental pollution resulting from petroleum refining effluents. The mycobiome (32 fungal strains) isolated from the industrial wastewater of the refinery sector in Jazan were belonged to five fungal genera including Fusarium, Verticillium, Purpureocillium, Clavispora and Scedosporium with a distribution percentage of 31.25, 21.88, 15.63, 12.50 and 18.75 %, respectively. These isolates showed multimetals tolerance and bioremoval efficiency against a large number of heavy metals (Fe2+, Ni2+, Cr6+, Zn2+, As3+, Cu2+, Cd2+, Pb2+, Ag+ and Hg2+) along with potent bioremediation activity toward crude oil and the polycyclic aromatic hydrocarbons. Interestingly, the mycobiome resistance patterns obtained against different classes of fungal antibiotics including azole (fluconazole, itraconazole, voriconazole, posaconazole, isavuconazole and ketoconazole), echinocandin (anidulafungin, caspofungin and micafungin) and polyene (amphotericin B) drugs proved the prevalence of antibiotic resistance among the mycobiome of refinery industry in Saudi Arabia is relatively low. The fungal isolate under isolation code JAZ-20 showed the highest bioremoval efficiency against heavy metals (90.8-100.0 %), crude oil (89.50 %), naphthalene (96.7 %), phenanthrene (92.52 %), fluoranthene (100.0 %), anthracene (90.34 %), pyrene (85.60 %) and chrysene (83.4 %). It showed the highest bioremoval capacity ranging from 85.72 % to 100.0 % against numerous pollutants found in a wide array of industrial effluents, including diclofenac, ibuprofen, carbamazepine, acetaminophen, sulfamethoxazole, bisphenol, bleomycin, vincristine, dicofol, methyl parathion, atrazine, diuron, dieldrin, chlorpyrifos, profenofos and phenanthrene. The isolate JAZ-20 was chosen for molecular typing, cytotoxicity assessment, analysis of volatile compounds and optimization investigations. Based on phenotypic, biochemical and phylogenetic analysis, strain JAZ-20 identified as Scedosporium apiospermum JAZ-20. This strain is newly discovered in industrial effluents in Saudi Arabia. Fungal strain JAZ-20 consistently produced various types of saturated and unsaturated fatty acids. the main fatty acids were C14:0 (1.95 %), iso-C14:0 (2.98 %), anteiso-C14:0 (2.13 %), iso-C15:0 (9.16 %), anteiso-C15:0 (11.75 %), C15:0 (7.42 %), C15:1 (2.37 %), anteiso-C16:0 (3.4 %), C16:0 (10.3 %), iso-C16:0 (9.5 %), C17:1 (1.36 %), anteiso-C17:1 (8.64 %), iso-C18:0 (11.0 %), C18:0 (3.63 %), anteiso-C19:0 (3.78 %), anteiso-C20:0 (2.0 %), iso-C21:0 (2.44 %), C23:0 (1.15 %), and C24:0 (2.17 %). These fatty acids serve as natural and eco-friendly antifungal agents, promoting fungal resistance and inhibiting the production of mycotoxins in the environment. Despite being an environmental isolate, its cytotoxicity was assessed against both normal and cancerous human cell lines. The IC50 values of JAZ-20 extract were 8.92, 10.41, 20.0, 16.5, and 40.0 μg/mL against WI38, MRC5, MCF10A, HEK293 and HDFs normal cells and 43.26, 33.75, and 40.0 μg/mL against liver (HepG2), breast (A549) and cervix (HeLa) cancers, respectively. Based on gas chromatography-mass spectrometry (GC-MS), analysis the extract of S. apiospermum JAZ-20 showed 47 known volatile compounds (VOCs) for varied and significant biological activities. Enhancing the bioremoval efficiency of heavy metals from actual refining wastewater involves optimizing process parameters. The parameters optimized were the contact time, the fungal biomass dosage, pH, temperature and agitation rate.

Effects of efflux pumps on antifungal activity of chitosan against Candida albicans

Background

Antifungal resistance is a major problem, commonly caused by drug-efflux pump overexpression. To evaluate if chitosan could be effective in drug-resistant Candida infections, we investigated the effects of efflux pumps on antifungal activity of chitosan.

Materials and Methods

The minimal fungicidal concentration (MFC) of oligomer (7-9 kD) and polymer (900-1,000 kD) chitosan against Saccharomyces cerevisiae and Candida albicans were evaluated by broth and agar dilution methods. The MFCs of S. cerevisiae with single deletion of efflux pump genes, with deletion of seven efflux pumps (AD∆), and AD∆ overexpressing C. albicans efflux pump genes (CDR1, CDR2 and MDR1) were determined. C. albicans with homozygous deletions of CDR1 and of CDR2 were generated using CRISPR-Cas9 system and tested for chitosan susceptibility.

Results

While deleting any individual efflux pump genes had no effect on chitosan susceptibility, simultaneous deletion of multiple pumps (in AD∆) increased sensitivity to both types of chitosan. Interestingly, the overexpression of CDR1, CDR2 or MDR1 in AD∆ barely affected its sensitivity. Moreover, C. albicans with homozygous deletions of CDR1 and/or CDR2 showed similar sensitivity to wildtype.

Conclusion

Thus, C. albicans susceptibility to chitosan was not affected by drug-efflux pumps. Chitosan may be a promising antifungal agent against pump-overexpressing azole-resistant C. albicans.

Evolutionary trends in antifungal resistance: a meta-analysis

The present paper includes a meta-analysis of literature data on 318 species of fungi belonging to 34 orders in their response to 8 antifungal agents (amphotericin B, caspofungin, fluconazole, itraconazole, ketoconazole, posaconazole, terbinafine, and voriconazole). Main trends of MIC results at the ordinal level were visualized. European Committee on Antimicrobial Susceptibility Testing and Clinical & Laboratory Standards Institute (CLSI) clinical breakpoints were used as the staff gauge to evaluate MIC values ranging from resistance to susceptibility, which were subsequently compared with a phylogenetic tree of the fungal kingdom. Several orders (Hypocreales, Microascales, and Mucorales) invariably showed resistance. Also the basidiomycetous orders Agaricales, Polyporales, Sporidiales, Tremellales, and Trichosporonales showed relatively high degrees of azole multi-resistance, while elsewhere in the fungal kingdom, including orders with numerous pathogenic and opportunistic species, that is, Onygenales, Chaetothyiales, Sordariales, and Malasseziales, in general were susceptible to azoles. In most cases, resistance vs susceptibility was consistently associated with phylogenetic distance, members of the same order showing similar behavior.

IMPORTANCE

A kingdom-wide the largest set of published wild-type antifungal data comparison were analyzed. Trends in resistance in taxonomic groups (monophyletic clades) can be compared with the phylogeny of the fungal kingdom, eventual relationships between fungus-drug interaction and evolution can be described.

The Zanthoxylum armatum fruit's oil exterminates Candida cells by inhibiting ergosterol biosynthesis without generating reactive oxygen species

Candida spp. is a significant cause of topical and fungal infections in humans. In addition to Candida albicans, many non-albicans species such as C. krusei, C. glabrata, C. parapsilosis, C. tropicalis, C. guilliermondii cause severe infections. The main antifungal agents belong to three different classes, including azoles, polyenes, and echinocandins. However, resistance to all three categories of drugs has been reported. Therefore, there is an urgent need to search for other alternatives with antifungal activity. Many herbal extracts and compounds from natural sources show excellent antifungal activity. In this study, we used an oil extract from the fruits of Zanthoxylum armatum, which showed significant antifungal activity against various Candida spp. by two different methods-minimum inhibitory concentration (MIC) and agar diffusion. In addition, we attempted to explore the possible mechanism of action in C. albicans. It was found that the antifungal activity of Z. armatum oil is fungicidal and involves a decrease in the level of ergosterol in the cell membrane. The decrease in ergosterol level resulted in increased passive diffusion of a fluorescent molecule, rhodamine6G, across the plasma membrane, indicating increased membrane fluidity. The oil-treated cells showed decreased germ tube formation, an important indicator of C. albicans' virulence. The fungal cells also exhibited decreased attachment to the buccal epithelium, the first step toward invasion, biofilm formation, and damage to oral epithelial cells. Interestingly, unlike most antifungal agents, in which the generation of reactive oxygen species is responsible for killing, no significant effect was observed in the present study.

Immunotherapies against human bacterial and fungal infectious diseases: A review

Nations' ongoing struggles with a number of novel and reemerging infectious diseases, including the ongoing global health issue, the SARS-Co-V2 (severe acute respiratory syndrome coronavirus 2) outbreak, serve as proof that infectious diseases constitute a serious threat to the global public health. Moreover, the fatality rate in humans is rising as a result of the development of severe infectious diseases brought about by multiple drug-tolerant pathogenic microorganisms. The widespread use of traditional antimicrobial drugs, immunosuppressive medications, and other related factors led to the establishment of such drug resistant pathogenic microbial species. To overcome the difficulties commonly encountered by current infectious disease management and control processes, like inadequate effectiveness, toxicities, and the evolution of drug tolerance, new treatment solutions are required. Fortunately, immunotherapies already hold great potential for reducing these restrictions while simultaneously expanding the boundaries of healthcare and medicine, as shown by the latest discoveries and the success of drugs including monoclonal antibodies (MAbs), vaccinations, etc. Immunotherapies comprise methods for treating diseases that specifically target or affect the body's immune system and such immunological procedures/therapies strengthen the host's defenses to fight those infections. The immunotherapy-based treatments control the host's innate and adaptive immune responses, which are effective in treating different pathogenic microbial infections. As a result, diverse immunotherapeutic strategies are being researched more and more as alternative treatments for infectious diseases, leading to substantial improvements in our comprehension of the associations between pathogens and host immune system. In this review we will explore different immunotherapies and their usage for the assistance of a broad spectrum of infectious ailments caused by various human bacterial and fungal pathogenic microbes. We will discuss about the recent developments in the therapeutics against the growing human pathogenic microbial diseases and focus on the present and future of using immunotherapies to overcome these diseases. Graphical AbstractThe graphical abstract shows the therapeutic potential of different types of immunotherapies like vaccines, monoclonal antibodies-based therapies, etc., against different kinds of human Bacterial and Fungal microbial infections.

Antifungal susceptibility of the endophytic fungus Rhinocladiella similis (URM 7800) isolated from the Caatinga dry forest in Brazil

The present study reports a new occurrence of Rhinocladiella similis isolated as an endophytic fungus in the Caatinga dry tropical forest in Brazil and describes its antifungal susceptibility. The isolate R. similis URM 7800 was obtained from leaves of the medicinal plant Myracrodruon urundeuva. Its morphological characterization was performed on potato dextrose agar medium and molecular analysis using the ITS rDNA sequence. The antifungal susceptibility profile was defined using the Clinical and Laboratory Standards Institute (CLSI) protocol M38-A2. The colony of isolate URM 7800 showed slow growth, with an olivaceous-gray color and powdery mycelium; in microculture, it showed the typical features of R. similis. In the antifungal susceptibility test, isolate URM 7800 showed high minimal inhibitory concentration (MIC) values for amphotericin B (>16 μg/mL), voriconazole (16 μg/mL), terbinafine (>0.5 μg/mL), and caspofungin (>8 μg/mL), among other antifungal drugs. Pathogenic melanized fungi are frequently isolated in environments where humans may be exposed, and these data show that it is essential to know if these isolates possess antifungal resistance.

Nanohybrids of oxides nanoparticles-chitosan and their antimicrobial properties

Growing international problem with pathogens acquiring resistance to antibiotics is the reason for the search for bactericidal substances against which microorganisms cannot become resistant. The aim of this study was to synthesize inorganic-organic nanohybrids and obtain materials with antimicrobial effects. Chitosan (CS) was deposited on nanocomposite carriers such as calcium oxide with titanium dioxide (CaO-TiO₂), magnesium oxide with titanium dioxide (MgO-TiO₂) and copper(II) oxide with titanium dioxide (CuO-TiO₂). The efficiency of the process was examined at varying concentrations of chitosan and temperature. The parameters for nanohybrids synthesis were selected based on the highest amount of nano-chitosan deposited on the nanohybrids-for each carrier, the process conditions were as follows: chitosan solution at 5 g l^-1and 20 °C. The materials were obtained using these parameters and were used for microbiological tests againstE. coliATCC 25922,S. aureusATCC 25923 andC. albicansATCC 10231. The growth inhibitory activity of the obtained materials was qualitatively defined. These results suggest that the synthesized nanohybrids and nanocomposites exhibit biostatic action. The material with the broadest effect was the CuO-TiO₂-CS hybrid, which had biostatic properties against all tested strains at a minimal concentration of 1250μg ml^-1. Further research is required to find eco-friendly, non-toxic, and more effective antimicrobials with a broad action to prevent the acquisition of resistance.

Low Incidence of Invasive Fungal Disease Following CD19 Chimeric Antigen Receptor T-Cell (CAR-T) Therapy for Non-Hodgkin Lymphoma

CAR T-cell (CAR-T) therapy has revolutionized the treatment of hematologic malignancies, though its use may be complicated by toxicities including cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), and infections. Invasive fungal disease (IFD) has been reported following CAR-T therapy, but the incidence in the absence of antifungal prophylaxis is unknown. Optimal screening, prophylaxis, and preemptive treatment strategies are widely debated. We performed a single-center retrospective study of 280 adults receiving CD19 CAR-T therapy for Non-Hodgkin's lymphoma (NHL) between December 2017 and September 2021 (n=280). Patients did not receive routine anti-yeast or mold prophylaxis. Proven and probable IFD was identified between day of cell infusion and last follow up. Cumulative Incidence Functions were calculated at 100 days and 18 months based on time to IFD using dates of IFD-free death, initiation of salvage treatment following relapse, and hematopoietic cell transplantation as competing risks. Eight patients (2.9%) developed IFD, including 3 Pneumocystis jirovecii pneumonia (PJP), 3 invasive mold infections (IMIs), and 2 invasive yeast infections (IYIs). Five infections (3 IMI; 2 IYI) occurred prior to day 100 and the 100-day cumulative incidence of IFD accounting for competing risks was 1.8% (95% CI 0.8 - 4.4%). Amongst the 280 patients, many developed early toxicity including CRS (85%) and ICANS (55%). Late toxicities after day 30 including grade 3/4 neutropenia (41%), hypogammaglobulinemia (35%), and low CD4 T-cell count (20%) were common. IFD was rare amongst patients who received CD19 CAR-T therapy for NHL in the absence of routine antifungal prophylaxis despite frequent toxicities including CRS, ICANS, and late neutropenia. This study suggests that in settings with low institutional rates of IFD, routine antifungal prophylaxis may not be indicated.

Enhancement of the Antifungal Activity of Chitinase by Palmitoylation and the Synergy of Palmitoylated Chitinase with Amphotericin B

Combinations of antifungal drugs can have synergistic antifungal activity, achieving high therapeutic efficacy while minimizing the side effects. Amphotericin B (AMB) has been used as a standard antifungal drug for fungal infections; however, because of its high toxicity, new strategies to minimize the required dose are desirable. Chitinases have recently received attention as alternative safe antifungal agents. Herein, we report the combination of palmitoylated chitinase domains with AMB to enhance the antifungal activity. The chitin-binding domain (LysM) from Pteris ryukyuensis chitinase was site-specifically palmitoylated by conjugation reaction catalyzed by microbial transglutaminase. The palmitoylated LysM (LysM-Pal) exhibited strong antifungal activity against Trichoderma viride, inhibiting the growth completely at a concentration of 2 μM. This antifungal effect of LysM-Pal was mainly due to the effect of anchoring of palmitic acid motif to the plasma membrane of fungi. A combination of AMB with LysM-Pal resulted in synergistic enhancement of the antifungal activity. Intriguingly, LysM-Pal exhibited higher level of antifungal activity enhancement than palmitoylated catalytic domain (CatD) and fusion of LysM and CatD. Addition of 0.5 μM LysM-Pal to AMB reduced the minimal inhibition concentration of AMB to 0.31 μM (2.5 μM without LysM-Pal). The possible mechanism of the synergistic effect of AMB and LysM-Pal is destabilization of the plasma membrane by anchoring of palmitic acid and ergosterol extraction by AMB and destabilization of the chitin layer by LysM binding. The combination of LysM-Pal with AMB can drastically reduce the dose of AMB and may be a useful strategy to treat fungal infections.

Invasive Yeast Infection After Haploidentical Donor Hematopoietic Cell Transplantation Associated with Cytokine Release Syndrome

BACKGROUND

Use of haploidentical donor hematopoietic cell transplantation (haploHCT) has expanded but recent reports raise concern for increased rates of infectious complications. The incidence and risk factors for invasive fungal disease (IFD) after haploHCT have not been well elucidated.

OBJECTIVE

The objective of this study is to evaluate the incidence and risk factors for IFD after haploHCT. The identification of key risk factors will permit targeted prevention measures and may explain elevated risk for other infectious complications after haploHCT.

STUDY DESIGN

We performed a single-center retrospective study of all adults undergoing haploHCT between May 2011 and May 2021 (n=205). The 30-day and one-year cumulative incidence of proven or probable IFD and one-year non-relapse mortality (NRM) were assessed. Secondary analysis evaluated risk factors for invasive yeast infection (IYI) using univariate and multivariable Cox regression models.

RESULTS

Twenty-nine patients (14%) developed IFD following haploHCT. Nineteen (9.3%) developed IYI in the first year, 13 of which occurred early with a 30-day cumulative incidence of 6.3% (95% CI 2.9 - 9.6%) and increased NRM in patients with IYI (53.9% versus 10.9%). The majority of yeast isolates (17/20; 85%) were fluconazole susceptible. The incidence of IYI in the first 30 days after haploHCT was 10% among the 110 (54%) patients who developed cytokine release syndrome (CRS) and 21% among the 29 (14%) who received tocilizumab. On multivariable analysis, AML (HR 6.24; 1.66 - 23.37; p=0.007) and CRS (HR 4.65; 1.00 - 21.58; p=0.049) were associated with an increased risk of early IYI after haploHCT.

CONCLUSION

CRS after haploHCT is common and is associated with increased risk of early IYI. The identification of CRS as a risk factor for IYI raises questions about its potential association with other infections after haploHCT. Recognition of key risk factors for infection may permit individualized strategies for prevention and intervention and minimize potential side effects.

Synergistic Effects Between Metal Nanoparticles and Commercial Antimicrobial Agents: A Review

Nanotechnology has expanded into a broad range of clinical applications. In particular, metal nanoparticles (MNPs) display unique antimicrobial properties, a fundamental function of novel medical devices. The combination of MNPs with commercial antimicrobial drugs (e.g., antibiotics, antifungals, and antivirals) may offer several opportunities to overcome some disadvantages of their individual use and enhance effectiveness. MNP conjugates display multiple advantages. As drug delivery systems, the conjugates can extend the circulation of the drugs in the body, facilitate intercellular targeting, improve drug stabilization, and possess superior delivery. Concomitantly, they reduce the required drug dose, minimize toxicity, and broaden the antimicrobial spectrum. In this work, the common strategies to combine MNPs with clinically used antimicrobial agents are underscored. Furthermore, a comprehensive survey about synergistic antimicrobial effects, the mechanism of action, and cytotoxicity is depicted.

Genetic Manipulation in Mucorales and New Developments to Study Mucormycosis

The study of the Mucoralean fungi physiology is a neglected field that the lack of effective genetic tools has hampered in the past. However, the emerging fungal infection caused by these fungi, known as mucormycosis, has prompted many researchers to study the pathogenic potential of Mucorales. The main reasons for this current attraction to study mucormycosis are its high lethality, the lack of effective antifungal drugs, and its recent increased incidence. The most contemporary example of the emergence character of mucormycosis is the epidemics declared in several Asian countries as a direct consequence of the COVID-19 pandemic. Fortunately, this pressure to understand mucormycosis and develop new treatment strategies has encouraged the blossoming of new genetic techniques and methodologies. This review describes the history of genetic manipulation in Mucorales, highlighting the development of methods and how they allowed the main genetic studies in these fungi. Moreover, we have emphasized the recent development of new genetic models to study mucormycosis, a landmark in the field that will configure future research related to this disease.

Special Issue: Alternative Therapeutic Approaches of Candida Infections

In recent decades, the prevalence of resistant fungal isolates has been steadily increasing both in veterinary and human medicine as well as in agriculture [...]

Stable and reproducible homologous recombination enables CRISPR-based engineering in the fungus Rhizopus microsporus

Mucormycosis is a lethal and emerging disease that has lacked a genetic model fulfilling both high virulence and the possibility of performing stable and reproducible gene manipulation by homologous recombination (HR). Here, we developed a new methodology to successfully perform HR in Rhizopus microsporus. We isolated an uracil auxotrophic recipient strain and optimized the critical steps in the genetic transformation of this fungus. This was followed by an adaptation of a plasmid-free CRISPR-Cas9 system coupled with microhomology repair templates. We reproducibly generated stable mutants in the genes leuA and crgA, encoding a 3-isopropylmalate dehydratase and an ubiquitin ligase, respectively. Our new genetic model showed that mutations in the gene pyrF, a key virulence gene in several bacterial and fungal pathogens, correlated with an avirulent phenotype in an immunocompetent murine host. This was reverted by gene complementation, showing the broad possibilities of our methodology.

Antimicrobial activity of manogepix, a first-in-class antifungal, and comparator agents tested against contemporary invasive fungal isolates from an international surveillance programme (2018-2019)

OBJECTIVES

Manogepix, the active moiety of the prodrug fosmanogepix, is a novel antifungal with activity against major fungal pathogens including Candida (except Candida krusei), Aspergillus and difficult-to-treat/rare moulds. We tested manogepix and comparators against 2669 contemporary (2018-2019) fungal isolates collected from 82 medical centres in North America (42.3%), Europe (37.9%), Asia-Pacific (12.3%) and Latin America (7.6%). Of these, 70.7% were Candida spp., 3.6% were non-Candida yeasts including 49 Cryptococcus neoformans var. grubii, 21.7% were Aspergillus spp. and 4.1% were other moulds.

METHODS

Isolates were tested for antifungal susceptibility by the CLSI reference broth microdilution method.

RESULTS

Manogepix (MIC_50/90, 0.008/0.06 mg/L) was the most active agent tested against Candida spp. isolates; corresponding anidulafungin, micafungin and fluconazole MIC₉₀ values were 16- to 64-fold higher. Similarly, manogepix (MIC_50/90, 0.5/2 mg/L) was ≥4-fold more active than anidulafungin, micafungin and fluconazole against C. neoformans var. grubii. Against Aspergillus spp., manogepix (MEC_50/90, 0.015/0.03 mg/L) had comparable activity to anidulafungin and micafungin. Low manogepix concentrations inhibited uncommon species of Candida, non-Candida yeasts, and rare moulds including Scedosporium spp. and Lomentospora (Scedosporium) prolificans.

CONCLUSION

Manogepix exhibited potent activity against contemporary fungal isolates, including echinocandin- and azole-resistant strains of Candida and Aspergillus spp., respectively. Although rare, Candida strains that were non-wild type for manogepix demonstrated resistance to fluconazole. However, the clinical relevance of this finding is unknown. The extended spectrum of manogepix is noteworthy for its activity against many less-common yet antifungal-resistant strains. Clinical studies are underway to evaluate the utility of fosmanogepix against difficult-to-treat resistant fungal infections.

Two Functionally Redundant FK506-Binding Proteins Regulate Multidrug Resistance Gene Expression and Govern Azole Antifungal Resistance

Increasing resistance to antifungal therapy is an impediment to the effective treatment of fungal infections. Candida glabrata is an opportunistic human fungal pathogen that is inherently less susceptible to cost-effective azole antifungals. Gain-of-function mutations in the Zn-finger pleiotropic drug resistance transcriptional activator-encoding gene CgPDR1 are the most prevalent causes of azole resistance in clinical settings. CgPDR1 is also transcriptionally activated upon azole exposure; however, factors governing CgPDR1 gene expression are not yet fully understood. Here, we have uncovered a novel role for two FK506-binding proteins, CgFpr3 and CgFpr4, in the regulation of the CgPDR1 regulon. We show that CgFpr3 and CgFpr4 possess a peptidyl-prolyl isomerase domain and act redundantly to control CgPDR1 expression, as a Cgfpr3Δ4Δ mutant displayed elevated expression of the CgPDR1 gene along with overexpression of its target genes, CgCDR1, CgCDR2, and CgSNQ2, which code for ATP-binding cassette multidrug transporters. Furthermore, CgFpr3 and CgFpr4 are required for the maintenance of histone H3 and H4 protein levels, and fluconazole exposure leads to elevated H3 and H4 protein levels. Consistent with the role of histone proteins in azole resistance, disruption of genes coding for the histone demethylase CgRph1 and the histone H3K36-specific methyltransferase CgSet2 leads to increased and decreased susceptibility to fluconazole, respectively, with the Cgrph1Δ mutant displaying significantly lower basal expression levels of the CgPDR1 and CgCDR1 genes. These data underscore a hitherto unknown role of histone methylation in modulating the most common azole antifungal resistance mechanism. Altogether, our findings establish a link between CgFpr-mediated histone homeostasis and CgPDR1 gene expression and implicate CgFpr in the virulence of C. glabrata.

Mechanisms of Candida Resistance to Antimycotics and Promising Ways to Overcome It: The Role of Probiotics

Pathogenic Candida and infections caused by those species are now considered as a serious threat to public health. The treatment of candidiasis is significantly complicated by the increasing resistance of pathogenic strains to current treatments and the stagnant development of new antimycotic drugs. Many species, such as Candida auris, have a wide range of resistance mechanisms. Among the currently used synthetic and semi-synthetic antifungal drugs, the most effective are azoles, echinocandins, polyenes, nucleotide analogs, and their combinations. However, the use of probiotic microorganisms and/or the compounds they produce is quite promising, although underestimated by modern pharmacology, to control the spread of pathogenic Candida species.

Glucose - The X factor for the survival of human fungal pathogens and disease progression in the host

The incidence of human fungal infections is increasing due to the expansion of the immunocompromised patient population. The continuous use of different antifungal agents has eventually resulted in the establishment of resistant fungal species. The fungal pathogens unfold multiple resistance strategies to successfully tackle the effect of different antifungal agents. For the successful colonization and establishment of infection inside the host, the pathogenic fungi switch to the process of metabolic flexibility to regulate distinct nutrient uptake systems as well as to modulate their metabolism accordingly. Glucose the most favourable carbon source helps carry out the important survival and niche colonization processes. Adopting glucose as the center, this review has been put forward to provide an outline of the important processes like growth, the progression of infection, and the metabolism regulated by glucose, affecting the pathogenicity and virulence traits in the human pathogenic fungi. This could help in the identification of better treatment options and appropriate target-oriented antifungal drugs based on the glucose-regulated pathways and processes. In the article, we have also presented a summary of the novel studies and findings pointing to glucose-based potential therapeutic avenues to be explored to tackle the problem of globally increasing multidrug-resistant human fungal infections.

Host defence peptides identified in human apolipoprotein B as promising antifungal agents

Abstract

Therapeutic options to treat invasive fungal infections are still limited. This makes the development of novel antifungal agents highly desirable. Naturally occurring antifungal peptides represent valid candidates, since they are not harmful for human cells and are endowed with a wide range of activities and their mechanism of action is different from that of conventional antifungal drugs. Here, we characterized for the first time the antifungal properties of novel peptides identified in human apolipoprotein B. ApoB-derived peptides, here named r(P)ApoB_L^Pro, r(P)ApoB_L^Ala and r(P)ApoB_S^Pro, were found to have significant fungicidal activity towards Candida albicans (C. albicans) cells. Peptides were also found to be able to slow down metabolic activity of Aspergillus niger (A. niger) spores. In addition, experiments were carried out to clarify the mechanism of fungicidal activity of ApoB-derived peptides. Peptides immediately interacted with C. albicans cell surfaces, as indicated by fluorescence live cell imaging analyses, and induced severe membrane damage, as indicated by propidium iodide uptake induced upon treatment of C. albicans cells with ApoB-derived peptides. ApoB-derived peptides were also tested on A. niger swollen spores, initial hyphae and branched mycelium. The effects of peptides were found to be more severe on swollen spores and initial hyphae compared to mycelium. Fluorescence live cell imaging analyses confirmed peptide internalization into swollen spores with a consequent accumulation into hyphae. Altogether, these findings open interesting perspectives to the application of ApoB-derived peptides as effective antifungal agents.

Key points

Human cryptides identified in ApoB are effective antifungal agents.

ApoB-derived cryptides exert fungicidal effects towards C. albicans cells.

ApoB-derived cryptides affect different stages of growth of A. niger.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-021-11114-3.

Interaction Between Dendritic Cells and Candida krusei β-Glucan Partially Depends on Dectin-1 and It Promotes High IL-10 Production by T Cells

Host-Candida interaction has been broadly studied during Candida albicans infection, with a progressive shift in focus toward non-albicans Candida species. C. krusei is an emerging multidrug resistant pathogen causing rising morbidity and mortality worldwide. Therefore, understanding the interplay between the host immune system and C. krusei is critically important. Candia cell wall β-glucans play significant roles in the induction of host protective immune responses. However, it remains unclear how C. krusei β-glucan impacts dendritic cell (DC) responses. In this study, we investigated DC maturation and function in response to β-glucans isolated from the cell walls of C. albicans, C. tropicalis, and C. krusei. These three distinct Candida β-glucans had differential effects on expression of the DC marker, CD11c, and on DC maturation. Furthermore, bone-marrow derived DCs (BMDCs) showed enhanced cytokine responses characterized by substantial interleukin (IL)-10 production following C. krusei β-glucan stimulation. BMDCs stimulated with C. krusei β-glucan augmented IL-10 production by T cells in tandem with increased IL-10 production by BMDCs. Inhibition of dectin-1 ligation demonstrated that the interactions between dectin-1 on DCs and cell wall β-glucans varied depending on the Candida species. The effects of C. krusei β-glucan were partially dependent on dectin-1, and this dependence, in part, led to distinct DC responses. Our study provides new insights into immune regulation by C. krusei cell wall components. These data may be of use in the development of new clinical approaches for treatment of patients with C. krusei infection.

Fungal Quorum-Sensing Molecules: A Review of Their Antifungal Effect against Candida Biofilms

The number of effective therapeutic strategies against biofilms is limited; development of novel therapies is urgently needed to treat a variety of biofilm-associated infections. Quorum sensing is a special form of microbial cell-to-cell communication that is responsible for the release of numerous extracellular molecules, whose concentration is proportional with cell density. Candida-secreted quorum-sensing molecules (i.e., farnesol and tyrosol) have a pivotal role in morphogenesis, biofilm formation, and virulence. Farnesol can mediate the hyphae-to-yeast transition, while tyrosol has the opposite effect of inducing transition from the yeast to hyphal form. A number of questions regarding Candida quorum sensing remain to be addressed; nevertheless, the literature shows that farnesol and tyrosol possess remarkable antifungal and anti-biofilm effect at supraphysiological concentration. Furthermore, previous in vitro and in vivo data suggest that they may have a potent adjuvant effect in combination with certain traditional antifungal agents. This review discusses the most promising farnesol- and tyrosol-based in vitro and in vivo results, which may be a foundation for future development of novel therapeutic strategies to combat Candida biofilms.

Targeting adhesion in fungal pathogen Candida albicans

Fungal infections with increasing resistance to conventional therapies are a growing concern. Candida albicans is a major opportunistic yeast responsible for mucosal and invasive infections. Targeting the initial step of the infection process (i.e., C. albicans adhesion to the host cell) is a promising strategy. A wide variety of molecules can interfere with adhesion processes via an assortment of mechanisms. Herein, we focus on how small molecules disrupt biosynthesis of fungal cell wall components and membrane structure, prevent the localization of GPI-anchor proteins, inhibit production of enzymes involved in adhesion, downregulate genes encoding adhesins and competitively inhibit receptor interactions. As a result, adhesion of C. albicans to host cells is reduced, paving the way to new classes of antifungal agents.

Difficult to Treat Infections in the Burn Patient

Background: Unusual infections can lead to complications in more severely burned patients and pose major challenges in treatment. Methods: The published literature of retrospective reviews and case series of the uncommon infections of osteomyelitis, polymicrobial bacteremia, recurrent bacteremia, endocarditis, central nervous system (CNS), and rare fungal infections in burned patients have been summarized and presented. Results: When compared with infections occurring in the non-burn population, these infections in burn patients are more likely to be because of gram-negative bacteria or fungi. Because of hyperdynamic physiology and changes in immunomodulatory response secondary to burns, the clinical presentation of these infections in a patient with major burns differs from that of the non-burn patient and may not be identified until the post-mortem examination. Some of these infections (osteomyelitis, endocarditis, CNS, rare fungal infections) may necessitate surgical intervention in addition to antimicrobial therapy to achieve cure. The presence of the burn and allograft can also present unique challenges for surgical management. Conclusions: These difficult and unusual infections in the severely burned patient necessitate an index of suspicion, appropriate diagnosis, identification and sensitivities of the putative pathogen, effective systemic antimicrobial therapy, and appropriate surgical intervention if recovery is to be achieved.

Diversity, Virulence Factors, and Antifungal Susceptibility Patterns of Pathogenic and Opportunistic Yeast Species in Rock Pigeon (Columba livia) Fecal Droppings in Western Saudi Arabia

Bird fecal matter is considered a potential source of pathogenic microbes such as yeast species that contaminate the environment. Therefore, it needs to be scrutinized to assess potential environmental health risks. The aim of this study was to investigate the diversity of the yeasts in pigeon fecal droppings, their antifungal susceptibility patterns, and virulence factors. We used culturing techniques to detect the yeasts in pigeon fecal droppings. The isolates were then characterized based on colony morphologies, microscopic examinations, and biochemical reactions. The molecular identification of all yeast isolates was performed by sequencing of the amplified ITS gene. Genes encoding virulence factors CAP1, CAP59, and PLB were also detected. Antifungal susceptibility patterns were examined by the disk diffusion method. A total of 46 yeast-like isolates were recovered, and they belonged to nine different genera, namely, Cryptococcus, Saccharomyces, Rhodotorula, Candida, Meyerozyma, Cyberlindnera, Rhodosporidium, Millerozyma, and Lodderomyces. The prevalence of two genera Cryptococcus and Rhodotorula was high. None of the yeast isolates exhibited any resistance to the antifungal drugs tested; however, all pathogenic Cryptococcus species were positive for virulence determinants like urease activity, growth at 37°C, melanin production, the PLB and CAP genes. This is the first report on the molecular diversity of yeast species, particularly, Cryptococcus species and their virulence attributes in pigeon fecal droppings in Saudi Arabia.

Bird fecal matter is considered a potential source of pathogenic microbes such as yeast species that contaminate the environment. Therefore, it needs to be scrutinized to assess potential environmental health risks. The aim of this study was to investigate the diversity of the yeasts in pigeon fecal droppings, their antifungal susceptibility patterns, and virulence factors. We used culturing techniques to detect the yeasts in pigeon fecal droppings. The isolates were then characterized based on colony morphologies, microscopic examinations, and biochemical reactions. The molecular identification of all yeast isolates was performed by sequencing of the amplified ITS gene. Genes encoding virulence factors CAP1, CAP59, and PLB were also detected. Antifungal susceptibility patterns were examined by the disk diffusion method. A total of 46 yeast-like isolates were recovered, and they belonged to nine different genera, namely, Cryptococcus, Saccharomyces, Rhodotorula, Candida, Meyerozyma, Cyberlindnera, Rhodosporidium, Millerozyma, and Lodderomyces. The prevalence of two genera Cryptococcus and Rhodotorula was high. None of the yeast isolates exhibited any resistance to the antifungal drugs tested; however, all pathogenic Cryptococcus species were positive for virulence determinants like urease activity, growth at 37°C, melanin production, the PLB and CAP genes. This is the first report on the molecular diversity of yeast species, particularly, Cryptococcus species and their virulence attributes in pigeon fecal droppings in Saudi Arabia.

Genetic diversity and antifungal susceptibility patterns of Aspergillus nidulans complex obtained from clinical and environmental sources

The molecular epidemiology and antifungal susceptibility of Aspergillus nidulans species complex has not been well studied. To evaluate the genetic diversity and antifungal susceptibility patterns of clinical and environmental isolates of A. nidulans complex. Sixty clinical and environmental isolates of Aspergillus section Nidulantes were collected from five countries (Iran, The Netherlands, Spain, Portugal and Greece). The species were molecularly identified by sequencing of β-tubulin gene. The genetic diversity of A nidulans complex isolates (n = 54) was determined with a microsatellite genotyping assay. Antifungal susceptibility profile was determined using EUCAST method. The isolates were classified as A nidulans (46.7%), A spinulosporus (26.6%), A quadrilineatus (10%), A pachycristatus (3.3%), A rugulosus (3.3%), A unguis (5%), A creber, (1.7%), A olivicola (1.7%) and A sydowii (1.7%). Thirty-four sequence types (STs) were identified among the 54 A nidulans complex isolates. A high level of genetic diversity was found among A nidulans sensu stricto strains but low diversity was found among A spinulosporus strains. Amphotericin B showed high MICs to all species. The most active azole was posaconazole (GM = 0.64 mg/L), while itraconazole showed the highest MICs among azoles (GM = 2.95 mg/L). A spinulosporus showed higher MICs than A nidulans sensu stricto for all antifungals except for micafungin and anidulafungin. Interspecies variations may result in differences in antifungal susceptibility patterns and challenge antifungal therapy in infections caused by A nidulans. Differences in the distribution of STs or persistence of multiple STs might be related to the sources of isolation and niche specialisation.

Antifungal Activity of Essential Oils Against Candida Species Isolated from Clinical Samples

We evaluated the in vitro antifungal activity of essential oils obtained from the aromatic plants Laurus nobilis, Thymus vulgaris, Mentha piperita, Cymbopogon citratus and Lippia junelliana against the following Candida species isolated from clinical samples: C. krusei (n = 10); C. albicans (n = 50); C. glabrata (n = 70) and C. parapsilosis (n = 80). The minimal inhibitory concentration (MIC) was determined according to EDef 7.3.1 document from EUCAST. Amphotericin B and fluconazole were the antifungal drugs used as inhibition control. The concentration ranges evaluated were 0.4-800 and 0.03-128 mg l^-1 for essential oils and antifungal drugs, respectively. MIC₅₀ and MIC₉₀, mode and ranges were calculated. All the Candida spp. evaluated were susceptible to amphotericin B (MIC ≤ 1 mg l^-1), while fluconazole was inactive for C. krusei (MIC ≥ 32 mg l^-1) and intermediate for C. glabrata (MIC≤ 32 mg l^-1). The essential oils showed antifungal activity on Candida spp. tested with MIC₉₀ values ranging from 0.8 to 800 mg l^-1. In general, the most active essential oils were L. nobilis and T. vulgaris (MIC₉₀ 0.8-0.16 mg l^-1), and the least active was C. officinalis (MIC₉₀ 400-800 mg l^-1). C. krusei was inhibited by 5/6 of the essential oils evaluated, and C. glabrata was the least susceptible one. This in vitro study confirms the antifungal activity of these six essential oils assayed which could be a potential source of new molecules useful to control fungal infections caused by some Candida species, including those resistant to antifungal drugs.

In Vitro Activity of APX001A (Manogepix) and Comparator Agents against 1,706 Fungal Isolates Collected during an International Surveillance Program in 2017

Current antifungal agents cover a majority of opportunistic fungal pathogens; however, breakthrough invasive fungal infections continue to occur and increasingly involve relatively uncommon yeasts and molds, which often exhibit decreased susceptibility. APX001A (manogepix) is a first-in-class small-molecule inhibitor of the conserved fungal Gwt1 protein. This enzyme is required for acylation of inositol during glycosylphosphatidylinositol anchor biosynthesis. APX001A is active against the major fungal pathogens, i.e., Candida (except Candida krusei), Aspergillus, and hard-to-treat molds, including Fusarium and Scedosporium In this study, we tested APX001A and comparators against 1,706 contemporary clinical fungal isolates collected in 2017 from 68 medical centers in North America (37.3%), Europe (43.4%), the Asia-Pacific region (12.7%), or Latin America (6.6%). Among the isolates tested, 78.5% were Candida spp., 3.9% were non-Candida yeasts, including 30 (1.8%) Cryptococcus neoformans var. grubii isolates, 14.7% were Aspergillus spp., and 2.9% were other molds. All isolates were tested by CLSI reference broth microdilution. APX001A (MIC₅₀, 0.008 μg/ml; MIC₉₀, 0.06 μg/ml) was the most active agent tested against Candida sp. isolates; corresponding anidulafungin, micafungin, and fluconazole MIC₉₀ values were 16- to 64-fold higher. Similarly, APX001A (MIC₅₀, 0.25 μg/ml; MIC₉₀, 0.5 μg/ml) was ≥8-fold more active than anidulafungin, micafungin, and fluconazole against C. neoformans var. grubii Against Aspergillus spp., AXP001A (50% minimal effective concentration [MEC₅₀], 0.015 μg/ml; MEC₉₀, 0.03 μg/ml) was comparable in activity to anidulafungin and micafungin. Aspergillus isolates (>98%) exhibited a wild-type phenotype for the mold-active triazoles (itraconazole, posaconazole, and voriconazole). APX001A was highly active against uncommon species of Candida, non-Candida yeasts, and rare molds, including 11 isolates of Scedosporium spp. (MEC values, 0.015 to 0.06 μg/ml). APX001A demonstrated potent in vitro activity against recent fungal isolates, including echinocandin- and fluconazole-resistant strains. The extended spectrum of APX001A was also notable for its potency against many less common but antifungal-resistant strains. Further studies are in progress to evaluate the clinical utility of the methyl phosphate prodrug, APX001, in difficult-to-treat resistant fungal infections.

In Vitro Activities of the Novel Investigational Tetrazoles VT-1161 and VT-1598 Compared to the Triazole Antifungals against Azole-Resistant Strains and Clinical Isolates of Candida albicans

The fungal Cyp51-specific inhibitors VT-1161 and VT-1598 have emerged as promising new therapies to combat fungal infections, including Candida spp. To evaluate their in vitro activities compared to other azoles, MICs were determined by Clinical and Laboratory Standards Institute (CLSI) method for VT-1161, VT-1598, fluconazole, voriconazole, itraconazole, and posaconazole against 68 C. albicans clinical isolates well characterized for azole resistance mechanisms and mutant strains representing individual azole resistance mechanisms. VT-1161 and VT-1598 demonstrated potent activity (geometric mean MICs ≤0.15 μg/ml) against predominantly fluconazole-resistant (≥8 μg/ml) isolates. However, five of 68 isolates exhibited MICs greater than six dilutions (>2 μg/ml) to both tetrazoles compared to fluconazole-susceptible isolates. Four of these isolates likewise exhibited high MICs beyond the upper limit of the assay for all triazoles tested. A premature stop codon in ERG3 likely explained the high-level resistance in one isolate. VT-1598 was effective against strains with hyperactive Tac1, Mrr1, and Upc2 transcription factors and against most ERG11 mutant strains. VT-1161 MICs were elevated compared to the control strain SC5314 for hyperactive Tac1 strains and two strains with Erg11 substitutions (Y132F and Y132F&K143R) but showed activity against hyperactive Mrr1 and Upc2 strains. While mutations affecting Erg3 activity appear to greatly reduce susceptibility to VT-1161 and VT-1598, the elevated MICs of both tetrazoles for four isolates could not be explained by known azole resistance mechanisms, suggesting the presence of undescribed resistance mechanisms to triazole- and tetrazole-based sterol demethylase inhibitors.

Twenty Years of the SENTRY Antifungal Surveillance Program: Results for Candida Species From 1997-2016

Background

The emergence of antifungal resistance threatens effective treatment of invasive fungal infection (IFI). Invasive candidiasis is the most common health care–associated IFI. We evaluated the activity of fluconazole (FLU) against 20 788 invasive isolates of Candida (37 species) collected from 135 medical centers in 39 countries (1997–2016). The activity of anidulafungin, caspofungin, and micafungin (MCF) was evaluated against 15 308 isolates worldwide (2006–2016).

Methods

Species identification was accomplished using phenotypic (1997–2001), genotypic, and proteomic methods (2006–2016). All isolates were tested using reference methods and clinical breakpoints published in the Clinical and Laboratory Standards Institute documents.

Results

A decrease in the isolation of Candida albicans and an increase in the isolation of Candida glabrata and Candida parapsilosis were observed over time. Candida glabrata was the most common non–C. albicans species detected in all geographic regions except for Latin America, where C. parapsilosis and Candida tropicalis were more common. Six Candida auris isolates were detected: 1 each in 2009, 2013, 2014, and 2015 and 2 in 2016; all were from nosocomial bloodstream infections and were FLU-resistant (R). The highest rates of FLU-R isolates were seen in C. glabrata from North America (NA; 10.6%) and in C. tropicalis from the Asia-Pacific region (9.2%). A steady increase in isolation of C. glabrata and resistance to FLU was detected over 20 years in the United States. Echinocandin-R (EC-R) ranged from 3.5% for C. glabrata to 0.1% for C. albicans and C. parapsilosis. Resistance to MCF was highest among C. glabrata (2.8%) and C. tropicalis (1.3%) from NA. Mutations on FKS hot spot (HS) regions were detected among 70 EC-R isolates (51/70 were C. glabrata). Most isolates harboring FKS HS mutations were resistant to 2 or more ECs.

Conclusions

EC-R and FLU-R remain uncommon among contemporary Candida isolates; however, a slow and steady emergence of resistance to both antifungal classes was observed in C. glabrata and C. tropicalis isolates.

Do Antimicrobial Proteins Contribute to Overcoming the Hidden Antifungal Crisis at the Dawn of a Post-Antibiotic Era?

The incidence of fungal infections has been grossly underestimated in the past decades as a consequence of poor identification techniques and a lack of regular epidemiologic surveys in low- and middle-income countries [...].

Cell wall mannan of Candida krusei mediates dendritic cell apoptosis and orchestrates Th17 polarization via TLR-2/MyD88-dependent pathway

Dendritic cells (DCs) abundantly express diverse receptors to recognize mannans in the outer surface of Candida cell wall, and these interactions dictate the host immune responses that determine disease outcomes. C. krusei prevalence in candidiasis worldwide has increased since this pathogen has developed multidrug resistance. However, little is known how the immune system responds to C. krusei. Particularly, the molecular mechanisms of the interplay between C. krusei mannan and DCs remain to be elucidated. We investigated how C. krusei mannan affected DC responses in comparison to C. albicans, C. tropicalis and C. glabrata mannan. Our results showed that only C. krusei mannan induced massive cytokine responses in DCs, and led to apoptosis. Although C. krusei mannan-activated DCs underwent apoptosis, they were still capable of initiating Th17 response. C. krusei mannan-mediated DC apoptosis was obligated to the TLR2 and MyD88 pathway. These pathways also controlled Th1/Th17 switching possibly by virtue of the production of the polarizing cytokines IL-12 and IL-6 by the C. krusei mannan activated-DCs. Our study suggests that TLR2 and MyD88 pathway in DCs are dominant for C. krusei mannan recognition, which differs from the previous reports showing a crucial role of C-type lectin receptors in Candida mannan sensing.

In Vitro Activity of Isavuconazole against Opportunistic Fungal Pathogens from Two Mycology Reference Laboratories

Monitoring antifungal susceptibility patterns for new and established antifungal agents seems prudent given the increasing prevalence of uncommon species associated with higher antifungal resistance. We evaluated the activity of isavuconazole against 4,856 invasive yeasts and molds collected worldwide. The 4,856 clinical fungal isolates, including 2,351 Candida species isolates, 97 non-Candida yeasts, 1,972 Aspergillus species isolates, and 361 non-Aspergillus molds, including 292 Mucorales isolates collected in 2015 to 2016, were tested using CLSI methods. The MIC values for isavuconazole versus Aspergillus ranged from 0.06 to ≥16 μg/ml. The modal MIC for isavuconazole was 0.5 μg/ml (range, 0.25 [A. nidulans and A. terreus species complex] to 4 μg/ml [A. calidoustus and A. tubingensis]). Eight A. fumigatus isolates had elevated isavuconazole MIC values at ≥8 μg/ml (non-wild type). Isavuconazole showed comparable activity to itraconazole against the Mucorales The lowest modal isavuconazole MIC values were seen for Rhizopus spp., R. arrhizus var. arrhizus, and R. microsporus (all 1 μg/ml). Candida species isolates were inhibited by ≤0.25 μg/ml of isavuconazole (range, 96.1% [C. lusitaniae] to 100.0% [C. albicans, C. dubliniensis, C. kefyr, and C. orthopsilosis]). MIC values were ≤1 μg/ml for 95.5% of C. glabrata isolates and 100.0% of C. krusei isolates. Isavuconazole was active against the non-Candida yeasts, including Cryptococcus neoformans (100.0% at ≤0.5 μg/ml). Isavuconazole exhibited excellent activity against most species of Candida and Aspergillus Isavuconazole was comparable to posaconazole and voriconazole against the less common yeasts and molds. Isavuconazole was generally less active than posaconazole and more active than voriconazole against the 292 Mucorales isolates. We confirm the potentially useful activity of isavuconazole against species of Rhizopus as determined by CLSI methods.

Susceptibility Testing of Fungi to Antifungal Drugs

Susceptibility testing of fungi against antifungal drugs commonly used for therapy is a key component of the care of patients with invasive fungal infections. Antifungal susceptibility testing (AFST) has progressed in recent decades to finally become standardized and available as both Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) reference methods and in commercial manual/automated phenotypic methods. In clinical practice, the Sensititre YeastOne and Etest methods are widely used for AFST, particularly for sterile site isolates of Candida. Nevertheless, AFST is moving toward new phenotypic methods, such as matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), that are capable of providing rapid, and potentially more actionable, results for the treating clinician. Our objective is to summarize updated data on phenotypic methods for AFST of Candida and Aspergillus species and to assess their significance in view of opposing, but emerging, molecular genotypic methods.

Future perspectives for cryptococcosis treatment

INTRODUCTION

Cryptococcosis is one of the most devastating human fungal infections. Despite its impact, none of the standard antifungals were developed after 1990. New, improved, less toxic, affordable and widely available treatment is, therefore, imperative.

AREAS COVERED

This review offers an insight into technological developments for cryptococcosis disclosed in patent literature. From a broad search of patent documents claiming cryptococcosis treatment and having earliest priority between 1995 and 2015, we selected and summarized compounds/molecules (i) revealed in documents disclosing in vivo activity against Cryptococcus spp. or (ii) found in the pipeline of companies that appeared as assignees in our patent search. This information was complemented with data on compounds under development for this indication from the database Integrity (Clarivate Analytics).

EXPERT OPINION

This review demonstrates that drug development against cryptococcosis is discrete. However, it also shows that the existing development is not focused on a single class of molecules, but on different types of molecules with distinct fungal targets, reflecting the complexity of generating novel anti-cryptococcal tools. Given the intrinsic difficulties and high costs of drug development and the evident market failure in this field, we consider drug repurposing the most promising avenue for cryptococcosis treatment.

Invasive Fungal Infections in Patients with Hematological Malignancies: Emergence of Resistant Pathogens and New Antifungal Therapies

Invasive fungal infections caused by drug-resistant organisms are an emerging threat to heavily immunosuppressed patients with hematological malignancies. Modern early antifungal treatment strategies, such as prophylaxis and empirical and preemptive therapy, result in long-term exposure to antifungal agents, which is a major driving force for the development of resistance. The extended use of central venous catheters, the nonlinear pharmacokinetics of certain antifungal agents, neutropenia, other forms of intense immunosuppression, and drug toxicities are other contributing factors. The widespread use of agricultural and industrial fungicides with similar chemical structures and mechanisms of action has resulted in the development of environmental reservoirs for some drug-resistant fungi, especially azole-resistant Aspergillus species, which have been reported from four continents. The majority of resistant strains have the mutation TR34/L98H, a finding suggesting that the source of resistance is the environment. The global emergence of new fungal pathogens with inherent resistance, such as Candida auris, is a new public health threat. The most common mechanism of antifungal drug resistance is the induction of efflux pumps, which decrease intracellular drug concentrations. Overexpression, depletion, and alteration of the drug target are other mechanisms of resistance. Mutations in the ERG11 gene alter the protein structure of C-demethylase, reducing the efficacy of antifungal triazoles. Candida species become echinocandin-resistant by mutations in FKS genes. A shift in the epidemiology of Candida towards resistant non-albicans Candida spp. has emerged among patients with hematological malignancies. There is no definite association between antifungal resistance, as defined by elevated minimum inhibitory concentrations, and clinical outcomes in this population. Detection of genes or mutations conferring resistance with the use of molecular methods may offer better predictive values in certain cases. Treatment options for resistant fungal infections are limited and new drugs with novel mechanisms of actions are needed. Prevention of resistance through antifungal stewardship programs is of paramount importance.