The Synergistic Antifungal Effect and Potential Mechanism of D-Penicillamine Combined With Fluconazole Against Candida albicans

Deciphering antifungal and antibiofilm mechanisms of isobavachalcone against Cryptococcus neoformans through RNA-seq and functional analyses

Cryptococcus neoformans has been designated as critical fungal pathogens by the World Health Organization, mainly due to limited treatment options and the prevalence of antifungal resistance. Consequently, the utilization of novel antifungal agents is crucial for the effective treatment of C. neoformans infections. This study exposed that the minimum inhibitory concentration (MIC) of isobavachalcone (IBC) against C. neoformans H99 was 8 µg/mL, and IBC dispersed 48-h mature biofilms by affecting cell viability at 16 µg/mL. The antifungal efficacy of IBC was further validated through microscopic observations using specific dyes and in vitro assays, which confirmed the disruption of cell wall/membrane integrity. RNA-Seq analysis was employed to decipher the effect of IBC on the C. neoformans H99 transcriptomic profiles. Real-time quantitative reverse transcription PCR (RT-qPCR) analysis was performed to validate the transcriptomic data and identify the differentially expressed genes. The results showed that IBC exhibited various mechanisms to impede the growth, biofilm formation, and virulence of C. neoformans H99 by modulating multiple dysregulated pathways related to cell wall/membrane, drug resistance, apoptosis, and mitochondrial homeostasis. The transcriptomic findings were corroborated by the antioxidant analyses, antifungal drug sensitivity, molecular docking, capsule, and melanin assays. In vivo antifungal activity analysis demonstrated that IBC extended the lifespan of C. neoformans-infected Caenorhabditis elegans. Overall, the current study unveiled that IBC targeted multiple pathways simultaneously to inhibit growth significantly, biofilm formation, and virulence, as well as to disperse mature biofilms of C. neoformans H99 and induce cell death.

Artemisinin May Disrupt Hyphae Formation by Suppressing Biofilm-Related Genes of Candida albicans: In Vitro and In Silico Approaches

This study aimed to assess the antifungal and antibiofilm efficacy of artemisinin against Candida (C.) species, analyze its impact on gene expression levels within C. albicans biofilms, and investigate the molecular interactions through molecular docking. The antifungal efficacy of artemisinin on a variety of Candida species, including fluconazole-resistant and -susceptible species, was evaluated by the microdilution method. The effect of artemisinin on C. albicans biofilm formation was investigated by MTT and FESEM. The mRNA expression of the genes related to biofilm was analyzed by qRT-PCR. In addition, molecular docking analysis was used to understand the interaction between artemisinin and C. albicans at the molecular level with RAS1-cAMP-EFG1 and EFG1-regulated genes. Artemisinin showed higher sensitivity against non-albicans Candida strains. Furthermore, artemisinin was strongly inhibitory against C. albicans biofilms at 640 µg/mL. Artemisinin downregulated adhesion-related genes ALS3, HWP1, and ECE1, hyphal development genes UME6 and HGC1, and hyphal CAMP-dependent protein kinase regulators CYR1, RAS1, and EFG1. Furthermore, molecular docking analysis revealed that artemisinin and EFG1 had the highest affinity, followed by UME6. FESEM analysis showed that the fluconazole- and artemisinin-treated groups exhibited a reduced hyphal network, unusual surface bulges, and the formation of pores on the cell surfaces. Our study suggests that artemisinin may have antifungal potential and showed a remarkable antibiofilm activity by significantly suppressing adhesion and hyphal development through interaction with key proteins involved in biofilm formation, such as EFG1.

The Effect of Dihydromyricetin on the Pharmacokinetics of Fluconazole in Sprague-Dawley Rat Plasma, Based on High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Background

The synergistic effect of dihydromyricetin (DHM) and fluconazole (FLC) can improve the killing effect of FLC-resistant Candida albicans in vitro and in vivo. However, it is not clear whether DHM affects the pharmacokinetic characteristics of FLC.

Methods

In this study, 12 Sprague-Dawley (SD) rats were randomly divided into two groups as follows: (1) an FLC group in which rats were administered FLC only (42 mg/kg orally); (2) an FLC with the combined administration of DHM group, in which rats received an equivalent FLC dose immediately following the administration of DHM (100 mg/kg). Blood samples were collected from the ocular choroid vein of rats and converted into plasma. The concentrations of FLC in the rat plasma were then determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and the related pharmacokinetic parameters were analysed. The initial mobile phase included 0.1% acetonitrile and water with gradient elution. Multiple reaction monitoring modes of m/z 307.2→220.1 for FLC, and m/z 237.1→194.2 for carbamazepine, were utilised to conduct quantitative analysis.

Results

The calibration curve of FLC in rat plasma demonstrated good linearity in the range of 0.1-30 μg/mL (r > 0.99), and the lower limit of quantification was 0.1 μg/mL. Moreover, the intra- and inter-day precision relative standard deviation of FLC was less than 9.09% and 6.51%, respectively. There were no significant differences in the pharmacokinetic parameters between the two groups.

Conclusion

The results showed that DHM administration did not significantly alter FLC pharmacokinetics in SD rat plasma.

Synergy and Mechanism of Leflunomide Plus Fluconazole Against Resistant Candida albicans: An in vitro Study

Objective

The global rise in the resistance of Candida albicans to conventional antifungals makes Candida albicans infections harder to treat. The main objective of this study was to investigate the antifungal effects and underlying mechanisms of leflunomide in combination with triazoles against resistant Candida albicans.

Methods

In this study, the microdilution method was used to determine the antifungal effects of leflunomide in combination with three triazoles on planktonic cells in vitro. The morphological transition from yeast to hyphae was observed under a microscope. The effects on ROS, metacaspase, efflux pumps, and intracellular calcium concentration were investigated, respectively.

Results

Our findings suggested that leflunomide + triazoles showed a synergistic effect against resistant Candida albicans in vitro. Further study concluded that the synergistic mechanisms were resulted from multiple factors, including the inhibited efflux of triazoles, the inhibition of yeast-to-hyphae transition, ROS increasing, metacaspase activation, and [Ca²⁺]_i disturbance.

Discussion

Leflunomide appears to be a potential enhancer of current antifungal agents for treating candidiasis caused by resistant Candida albicans. This study can also serve as an example to inspire the exploration of new approaches to treating resistant Candida albicans.

Antifungal activity and potential mechanism of action of caspofungin in combination with ribavirin against Candida albicans

The number of invasive fungal infections has increased dramatically, resulting in high morbidity and mortality among immunocompromised patients. With increasing use of caspofungin (CAS), resistant strains have emerged frequently and led to limitations in the treatment of patients with severe invasive Candida albicans infections. Combination therapy is an important method to deal with this issue. As such, this study investigated the activity of CAS in combination with ribavirin (RBV) against C. albicans. The results of this in-vitro study showed that the minimum inhibitory concentrations (MICs) of CAS and RBV when they were used as monotherapy were 0.5-1 μg/mL and 2-8 μg/mL, respectively, while the MIC of CAS decreased from 0.5-1 μg/mL to 0.0625-0.25 μg/mL when used in combination with RBV, with a fractional inhibitory concentration index (FICI) ≤0.5. In addition, the RBV + CAS combination group displayed synergistic effects against C. albicans biofilm over 4 h; the sessile MIC (sMIC) of CAS decreased from 0.5-1 µg/mL to 0.0625-0.25µg/mL and the sMIC of RBV decreased from 4-16 µg/mL to 1-2 µg/mL, with FICI <0.5. The survival of C. albicans-infected Galleria mellonella was prolonged, the fungal burden was decreased, and the area of tissue damage was reduced after combination therapy. Further study showed that the mechanisms of action of the synergistic effect were related to the inhibition of biofilm formation, the inhibition of hyphal growth, and the activation of metacaspases, but were not related to the accumulation of reactive oxygen species. It is hoped that these findings will contribute to the understanding of drug resistance in C. albicans, and provide new insights for the application of RBV.

Phytochemical Analysis, Antifungal, and Antioxidant Properties of Two Herbs (Tristemma mauritianum and Crassocephalum bougheyanum) and One Tree (Lavigeria macrocarpa) Species

Phytochemicals present in medicinal plants (herbs, shrubs, and trees) are endowed with high antimicrobial and antioxidant properties. The aim of this work was to study the chemical composition, antioxidant, and antifungal activities of Tristemma mauritianum, Crassocephalum bougheyanum, and Lavigeria macrocarpa. Chemical composition of the plant extracts was determined using standard methods. The antioxidant activities were performed using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), nitric oxide (NO), and hydroxyl (OH) scavenging assays. The antifungal activity of plant extracts and their combinations with antifungals was evaluated against eleven Candida spp. using the broth microdilution method by determining the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). The quantitative chemical analysis of the extracts of T. mauritianum, L. macrocarpa, and C. bougheyanum showed that they contain phenols, tannins, and flavonoids that vary according to the plant species and extracts. All the plant extracts presented promising antifungal (MIC = 64-2048 µg/mL) and antioxidant activities. The extract of T. mauritianum displayed the highest antifungal (MIC = 64-256 µg/mL) and antioxidant (IC₅₀ = 19.052 ± 1.11 μg/mL) activities which can be explained by its high phenolic content. Interestingly, extracts of T. mauritianum, L. macrocarpa, and C. bougheyanum displayed synergistic effects (fractional inhibitory concentration index, FICI ≤ 0.5) with ketoconazole against clinical resistant isolates. The results of the present study demonstrate promising antifungal and antioxidant activities of the tested plants that are associated to their phenol, tannin, and flavonoid contents. Hence, extracts of T. mauritianum and L. macrocarpa could be deeply investigated as antifungal alone and in combination with conventional antifungal drugs to treat infections caused by Candida spp.

Candida albicans biofilms: antifungal resistance, immune evasion, and emerging therapeutic strategies

Candida albicans is a fungal pathogen that can form biofilms on medical devices and host tissue, resulting in serious, life-threatening infections. These fungal biofilms are inherently resistant to traditional antifungal therapies and the host immune system; therefore, biofilm-associated infections are a huge clinical challenge. This review summarizes the most important insights into C. albicans biofilm-associated antifungal drug resistance mechanisms and immune evasion strategies. In addtion, this review also discusses the strategies for antifungal drug use to combat these processes, providing further evidence for novel drugs research and clinical therapies.

Antifungal Effect of Penicillamine Due to the Selective Targeting of L-Homoserine O-Acetyltransferase

Due to the apparent similarity of fungal and mammalian metabolic pathways, the number of established antifungal targets is low, and the identification of novel ones is highly desirable. The results of our studies, presented in this work, indicate that the fungal biosynthetic pathway of L-methionine, an amino acid essential for humans, seems to be an attractive perspective. The MET2 gene from Candida albicans encoding L-homoserine O-acetyltransferase (CaMet2p), an enzyme catalyzing the first step in that pathway, was cloned and expressed as the native or the oligo-His-tagged fusion protein in Escherichia coli. The recombinant enzymes were purified and characterized for their basic molecular properties and substrate specificities. The purified MET2 gene product revealed the appropriate activity, catalyzed the conversion of L-homoserine (L-Hom) to O-acetyl-L-homoserine (OALH), and exhibited differential sensitivity to several L-Hom or OALH analogues, including penicillamine. Surprisingly, both penicillamine enantiomers (L- and D-Pen) displayed comparable inhibitory effects. The results of the docking of L- and D-Pen to the model of CaMet2p confirmed that both enantiomeric forms of the inhibitor are able to bind to the catalytic site of the enzyme with similar affinities and a similar binding mode. The sensitivity of some fungal cells to L-Pen, depending on the presence or absence of L-Met in the medium, clearly indicate Met2p targeting. Moreover, C. glabrata clinical strains that are resistant to fluconazole displayed a similar susceptibility to L-Pen as the wild-type strains. Our results prove the potential usefulness of Met2p as a molecular target for antifungal chemotherapy.

Competitiveness during Dual-Species Biofilm Formation of Fusarium oxysporum and Candida albicans and a Novel Treatment Strategy

During an infection, a single or multispecies biofilm can develop. Infections caused by non-dermatophyte molds, such as Fusarium spp. and yeasts, such as Candida spp., are particularly difficult to treat due to the formation of a mixed biofilm of the two species. Fusarium oxysporum is responsible for approximately 20% of human fusariosis, while Candida albicans is responsible for superficial mucosal and dermal infections and for disseminated bloodstream infections with a mortality rate above 40%. This study aims to investigate the interactions between C. albicans and F. oxysporum dual-species biofilm, considering variable formation conditions. Further, the ability of the WMR peptide, a modified version of myxinidin, to eradicate the mixed biofilm when used alone or in combination with fluconazole (FLC) was tested, and the efficacy of the combination of WMR and FLC at low doses was assessed, as well as its effect on the expression of some biofilm-related adhesin and hyphal regulatory genes. Finally, in order to confirm our findings in vivo and explore the synergistic effect of the two drugs, we utilized the Galleria mellonella infection model. We concluded that C. albicans negatively affects F. oxysporum growth in mixed biofilms. Combinatorial treatment by WMR and FLC significantly reduced the biomass and viability of both species in mature mixed biofilms, and these effects coincided with the reduced expression of biofilm-related genes in both fungi. Our results were confirmed in vivo since the synergistic antifungal activity of WMR and FLC increased the survival of infected larvae and reduced tissue invasion. These findings highlight the importance of drug combinations as an alternative treatment for C. albicans and F. oxysporum mixed biofilms.

Augmenting Azoles with Drug Synergy to Expand the Antifungal Toolbox

Fungal infections impact the lives of at least 12 million people every year, killing over 1.5 million. Wide-spread use of fungicides and prophylactic antifungal therapy have driven resistance in many serious fungal pathogens, and there is an urgent need to expand the current antifungal arsenal. Recent research has focused on improving azoles, our most successful class of antifungals, by looking for synergistic interactions with secondary compounds. Synergists can co-operate with azoles by targeting steps in related pathways, or they may act on mechanisms related to resistance such as active efflux or on totally disparate pathways or processes. A variety of sources of potential synergists have been explored, including pre-existing antimicrobials, pharmaceuticals approved for other uses, bioactive natural compounds and phytochemicals, and novel synthetic compounds. Synergy can successfully widen the antifungal spectrum, decrease inhibitory dosages, reduce toxicity, and prevent the development of resistance. This review highlights the diversity of mechanisms that have been exploited for the purposes of azole synergy and demonstrates that synergy remains a promising approach for meeting the urgent need for novel antifungal strategies.

Antifungal Activity of Human Cathelicidin LL-37, a Membrane Disrupting Peptide, by Triggering Oxidative Stress and Cell Cycle Arrest in Candida auris

Candida auris, an evolving multidrug-resistant pathogenic yeast, is known for causing severe invasive infections associated with high mortality rates in hospitalized individuals. Distinct from other Candida species, C. auris can persist for longer periods on different surfaces and is resistant to all of the major classes of antifungal drugs. Therefore, there is an urgent need for new antimycotic drugs with improved efficacy and reduced toxicity. The development of new antifungals based on antimicrobial peptides from various sources is considered a promising alternative. In this study, we examined the in vitro anti-yeast activity of the human cathelicidin peptides LL-37 against clinical strains of C. auris alone and in combination with different antifungal drugs by broth microdilution assay. To understand the antifungal mechanism of action, cell envelopes, cell cycle arrest, and effect on oxidative stress enzymes were studied using standard protocols. The minimum inhibitory and fungicidal concentrations of cathelicidin LL-37 ranged from 25–100 and 50–200 µg/mL, respectively. A combination interaction in a 1:1 ratio (cathelicidin LL-37: antifungal drug) resulted in 70% synergy with fluconazole and 100% synergy with amphotericin B and caspofungin. Assessment of the C. auris membrane by using propidium iodide assay after exposure to cathelicidin LL-37 linked membrane permeabilization with inhibition of C. auris cell growth and viability. These results were backed up by scanning electron microscopy studies demonstrating that exposure with cathelicidin LL-37 caused C. auris cells to undergo extensive surface changes. Spectrophotometric analysis revealed that cathelicidin LL-37 caused oxidative stress in C. auris, as is evident from the significant increase in the activity of primary antioxidant enzymes. In addition, cathelicidin LL-37 inhibited the cell cycle and accumulated cells in the S phase. Therefore, these results specify the potential of cathelicidin LL-37 for developing a new and effective anti-Candida agent.

Antifungal Effects and Potential Mechanisms of Benserazide Hydrochloride Alone and in Combination with Fluconazole Against Candida albicans

Purpose

The resistance of C. albicans to traditional antifungal drugs brings a great challenge to clinical treatment. To overcome the resistance, developing antifungal agent sensitizers has attracted considerable attention. This study aimed to determine the anti-Candida activity of BEH alone or BEH–FLC combination and to explore the underlying mechanisms.

Materials and Methods

In vitro antifungal effects were performed by broth microdilution assay and XTT reduction assay. Infected Galleria mellonella larvae model was used to determine the antifungal effects in vivo. Probes Fluo-3/AM, FITC-VAD-FMK and rhodamine 6G were used to study the influence of BEH and FLC on intracellular calcium concentration, metacaspase activity and drug efflux of C. albicans.

Results

BEH alone exhibited obvious antifungal activities against C. albicans. BEH plus FLC not only showed synergistic effects against planktonic cells and preformed biofilms within 8 h but also enhanced the antifungal activity in infected G. mellonella larvae. Mechanistic studies indicated that antifungal effects of drugs might be associated with the increasement of calcium concentration, activation of metacaspase activity to reduce virulence and anti-biofilms, but were not related to drug efflux.

Conclusion

BEH alone or combined with FLC displayed potent antifungal activity both in vitro and in vivo, and the underlying mechanisms were related to reduced virulence factors.

Catechol thwarts virulent dimorphism in Candida albicans and potentiates the antifungal efficacy of azoles and polyenes

The present study was deliberately focused to explore the antivirulence efficacy of a plant allelochemical-catechol against Candida albicans, and attempts were made to elucidate the underlying mechanisms as well. Catechol at its sub-MIC concentrations (2-256 μg/mL) exhibited a dose dependent biofilm as well as hyphal inhibitory efficacies, which were ascertained through both light and fluorescence microscopic analyses. Further, sub-MICs of catechol displayed remarkable antivirulence efficacy, as it substantially inhibited C. albicans' virulence enzymes i.e. secreted hydrolases. Notably, FTIR analysis divulged the potency of catechol in effective loosening of C. albicans' exopolymeric matrix, which was further reinforced using EPS quantification assay. Although, catechol at BIC (256 μg/mL) did not disrupt the mature biofilms of C. albicans, their initial adherence was significantly impeded by reducing their hydrophobic nature. Besides, FTIR analysis also unveiled the ability of catechol in enhancing the production of farnesol-a metabolite of C. albicans, whose accumulation naturally blocks yeast-hyphal transition. The qPCR data showed significant down-regulation of candidate genes viz., RAS1, HWP1 and ALS3 which are the key targets of Ras-cAMP-PKA pathway -the pathway that contribute for C. albicans' pathogenesis. Interestingly, the up-regulation of TUP1 (a gene responsible for farnesol-mediated hyphal inhibition) during catechol exposure strengthen the speculation of catechol triggered farnesol-mediated hyphal inhibition. Furthermore, catechol profusely enhanced the fungicidal efficacy of certain known antifungal agent's viz., azoles (ketoconazole and miconazole) and polyenes (amphotericin-B and nystatin).

Tobacco Hornworm (Manduca sexta) caterpillars as a novel host model for the study of fungal virulence and drug efficacy

The two leading yeast pathogens of humans, Candida albicans and Cryptococcus neoformans, cause systemic infections in >1.4 million patients worldwide with mortality rates approaching 75%. It is thus imperative to study fungal virulence mechanisms, efficacy of antifungal drugs, and host response pathways. While this is commonly done in mammalian models, which are afflicted by ethical and practical concerns, invertebrate models, such as wax moth larvae and nematodes have been introduced over the last two decades. To complement existing invertebrate host models, we developed fifth instar caterpillars of the Tobacco Hornworm moth Manduca sexta as a novel host model. These caterpillars can be maintained at 37°C, are suitable for injections with defined amounts of yeast cells, and are susceptible to the most threatening yeast pathogens, including C. albicans, C. neoformans, C. auris, and C. glabrata. Importantly, fungal burden can be assessed daily throughout the course of infection in a single caterpillar’s feces and hemolymph. Infected caterpillars can be rescued by treatment with antifungal drugs. Notably, these animals are large enough for weight to provide a reliable and reproducible measure of fungal disease and to facilitate host tissue-specific expression analyses. M. sexta caterpillars combine a suite of parameters that make them suitable for the study of fungal virulence.

Rational Design of an Antifungal Polyacrylamide Library with Reduced Host-Cell Toxicity

Life-threatening invasive fungal infections represent an urgent threat to human health worldwide. The limited set of antifungal drugs has critical constraints such as resistance development and/or adverse side effects. One approach to overcome these limitations is to mimic naturally occurring antifungal peptides called defensins. Inspired by their advantageous amphiphilic properties, a library of 35 synthetic, linear, ternary polyacrylamides was prepared by controlled/living radical polymerization. The effect of the degree of polymerization (20, 40, and 100) and varying hydrophobic functionalities (branched, linear, cyclic, or aromatic differing in their number of carbons) on their antifungal activity was investigated. Short copolymers with a calculated log P of ∼1.5 revealed optimal activity against the major human fungal pathogen Candida albicans and other pathogenic fungal species with limited toxicity to mammalian host cells (red blood cells and fibroblasts). Remarkably, selected copolymers outperformed the commercial antifungal drug amphotericin B, with respect to the therapeutic index, highlighting their potential as novel antifungal compounds.

Combination Therapy to Treat Fungal Biofilm-Based Infections

An increasing number of people is affected by fungal biofilm-based infections, which are resistant to the majority of currently-used antifungal drugs. Such infections are often caused by species from the genera Candida, Aspergillus or Cryptococcus. Only a few antifungal drugs, including echinocandins and liposomal formulations of amphotericin B, are available to treat such biofilm-based fungal infections. This review discusses combination therapy as a novel antibiofilm strategy. More specifically, in vitro methods to discover new antibiofilm combinations will be discussed. Furthermore, an overview of the main modes of action of promising antibiofilm combination treatments will be provided as this knowledge may facilitate the optimization of existing antibiofilm combinations or the development of new ones with a similar mode of action.

Antifungal effects and potential mechanisms of lonidamine in combination with fluconazole against Candida albicans

OBJECTIVES

The resistance of Candida albicans (C. albicans) to classical antifungals has been increasing significantly and poses great challenges to clinical treatment. The objective of this research is to evaluate whether the combination of lonidamine (LND) and fluconazole (FLC) have synergistic antifungal activity against C. albicans and to explore the underlying synergistic mechanisms against FLC-resistant C. albicans.

METHODS

The antifungal effect on resistant planktonic C. albicans and preformed biofilms were performed by broth microdilution assay and XTT reduction assay. The influence on hyphal growth, cellular ROS level, metacaspase activity and drug transporters were investigated by morphogenesis observation, DCFH-DA, FITC-VAD-FMK and rhodamine6G assay, respectively.

RESULTS

LND in combination with FLC exhibited synergistic antifungal effects against resistant planktonic C. albicans and preformed biofilms of C. albicans in the early stages (performed at 4 h and 8 h). The synergistic mechanisms associated with the inhibition of the hyphal growth and the activation of metacaspase, but were not related to mediate cellular ROS level or drug uptake and efflux in resistant C. albicans.

CONCLUSION

LND combined with FLC exhibited synergistic antifungal activity against resistant C. albicans, and the synergistic mechanisms were related to anti-biofilms and reduce virulence factors.

EXPERT OPINION

The emergence of fluconazole-resistant Candida albicans strains poses great challenges to clinical treatment. Drug combination of non-antifungals and fluconazole has attracted a lot of attention to overcome Candida albicans drug resistance.

Antifungal Activity and Potential Mechanism of Panobinostat in Combination With Fluconazole Against Candida albicans

Invasive fungal infections are an emerging problem worldwide, which bring huge health challenges. Candida albicans, the most common opportunistic fungal pathogen, can cause bloodstream infections with high mortality in susceptible hosts. At present, available antifungal agents used in clinical practice are limited, and most of them also have some serious adverse effects. The emergence of drug resistance because of the wide use of antifungal agents is a new limitation to successful patient therapy. Drug combination therapy is increasingly becoming a way to enhance antifungal efficacy, and reduce drug resistance and potential toxicity. Panobinostat, as a pan-histone deacetylase inhibitor, has been approved by the United States Food and Drug Administration as novel antitumor agents. In this study, the antifungal effects and mechanisms of panobinostat combined with fluconazole (FLC) against C. albicans were explored for the first time. The results indicated that panobinostat could work synergistically with FLC against resistant C. albicans, the minimal inhibitory concentration (MIC) of panobinostat could decrease from 128 to 0.5–2 μg/ml and the MIC of FLC could decrease from >512 to 0.25–0.5 μg/ml, and the fractional inhibitory concentration index (FICI) value ranged from 0.0024 to 0.0166. It was not only synergized against planktonic cells but also against C. albicans biofilms performed ≤8 h when panobinostat is combined with fluconazole; the sessile MIC (sMIC) of panobinostat could decrease from >128 to 0.5–8 μg/ml and the sMIC of FLC from >1024 to 0.5–2 μg/ml, and the FICI value was <0.5. The Galleria mellonella infection model was used to evaluate the in vivo effect of the drug combination, and the result showed that the survival rate could be improved obviously. Finally, we explored the synergistic mechanisms of the drug combination. The hyphal growth, which plays roles in drug resistance, was found to be inhibited, and metacaspase which is related to cell apoptosis was activated (p < 0.01), whereas the synergistic effects were proven not to be related to the efflux pumps (p > 0.05). These findings might provide novel insights into the antifungal drug discovery and the treatment of candidiasis caused by C. albicans.

Galleria mellonella for the Evaluation of Antifungal Efficacy against Medically Important Fungi, a Narrative Review

The treatment of invasive fungal infections remains challenging and the emergence of new fungal pathogens as well as the development of resistance to the main antifungal drugs highlight the need for novel therapeutic strategies. Although in vitro antifungal susceptibility testing has come of age, the proper evaluation of therapeutic efficacy of current or new antifungals is dependent on the use of animal models. Mammalian models, particularly using rodents, are the cornerstone for evaluation of antifungal efficacy, but are limited by increased costs and ethical considerations. To circumvent these limitations, alternative invertebrate models, such as Galleria mellonella, have been developed. Larvae of G. mellonella have been widely used for testing virulence of fungi and more recently have proven useful for evaluation of antifungal efficacy. This model is suitable for infection by different fungal pathogens including yeasts (Candida, Cryptococcus, Trichosporon) and filamentous fungi (Aspergillus, Mucorales). Antifungal efficacy may be easily estimated by fungal burden or mortality rate in infected and treated larvae. The aim of the present review is to summarize the actual data about the use of G. mellonella for testing the in vivo efficacy of licensed antifungal drugs, new drugs, and combination therapies.

Galleria mellonella for the Evaluation of Antifungal Efficacy against Medically Important Fungi, a Narrative Review

The treatment of invasive fungal infections remains challenging and the emergence of new fungal pathogens as well as the development of resistance to the main antifungal drugs highlight the need for novel therapeutic strategies. Although in vitro antifungal susceptibility testing has come of age, the proper evaluation of therapeutic efficacy of current or new antifungals is dependent on the use of animal models. Mammalian models, particularly using rodents, are the cornerstone for evaluation of antifungal efficacy, but are limited by increased costs and ethical considerations. To circumvent these limitations, alternative invertebrate models, such as Galleria mellonella, have been developed. Larvae of G. mellonella have been widely used for testing virulence of fungi and more recently have proven useful for evaluation of antifungal efficacy. This model is suitable for infection by different fungal pathogens including yeasts (Candida, Cryptococcus, Trichosporon) and filamentous fungi (Aspergillus, Mucorales). Antifungal efficacy may be easily estimated by fungal burden or mortality rate in infected and treated larvae. The aim of the present review is to summarize the actual data about the use of G. mellonella for testing the in vivo efficacy of licensed antifungal drugs, new drugs, and combination therapies.