Miltefosine inhibits Candida albicans and non-albicans Candida spp. biofilms and impairs the dispersion of infectious cells

Milteforan, a promising veterinary commercial product against feline sporotrichosis

Sporotrichosis, the cutaneous mycosis most commonly reported in Latin America, is caused by the Sporothrix clinical clade species, including Sporothrix brasiliensis and Sporothrix schenckii sensu stricto. Due to its zoonotic transmission in Brazil, S. brasiliensis represents a significant health threat to humans and domestic animals. Itraconazole, terbinafine, and amphotericin B are the most used antifungals for treating sporotrichosis. However, many strains of S. brasiliensis and S. schenckii have shown resistance to these agents, highlighting the importance of finding new therapeutic options. Here, we demonstrate that milteforan, a commercial veterinary product against dog leishmaniasis, whose active principle is miltefosine, is a possible therapeutic alternative for the treatment of sporotrichosis, as observed by its fungicidal activity in vitro against different strains of S. brasiliensis and S. schenckii. Fluorescent miltefosine localizes to the Sporothrix cell membrane and mitochondria and causes cell death through increased permeabilization. Milteforan decreases S. brasiliensis fungal burden in A549 pulmonary cells and bone marrow-derived macrophages and also has an immunomodulatory effect by decreasing TNF-α, IL-6, and IL-10 production. Our results suggest milteforan as a possible alternative to treat feline sporotrichosis.

IMPORTANCE

Sporotrichosis is an endemic disease in Latin America caused by different species of Sporothrix. This fungus can infect domestic animals, mainly cats and eventually dogs, as well as humans. Few drugs are available to treat this disease, such as itraconazole, terbinafine, and amphotericin B, but resistance to these agents has risen in the last few years. Alternative new therapeutic options to treat sporotrichosis are essential. Here, we propose milteforan, a commercial veterinary product against dog leishmaniasis, whose active principle is miltefosine, as a possible therapeutic alternative for treating sporotrichosis. Milteforan decreases S. brasiliensis fungal burden in human and mouse cells and has an immunomodulatory effect by decreasing several cytokine production.

Milteforan, a promising veterinary commercial product against feline sporotrichosis

Sporotrichosis, the cutaneous mycosis most commonly reported in Latin America, is caused by the Sporothrix clinical clade species, including Sporothrix brasiliensis and Sporothrix schenckii sensu stricto. In Brazil, S. brasiliensis represents a vital health threat to humans and domestic animals due to its zoonotic transmission. Itraconazole, terbinafine, and amphotericin B are the most used antifungals for treating sporotrichosis. However, many strains of S. brasiliensis and S. schenckii have shown resistance to these agents, highlighting the importance of finding new therapeutic options. Here, we demonstrate that milteforan, a commercial veterinary product against dog leishmaniasis whose active principle is miltefosine, is a possible therapeutic alternative for the treatment of sporotrichosis, as observed by its fungicidal activity in vitro against different strains of S. brasiliensis and S. schenckii, and by its antifungal activity when used to treat infected epithelial cells and macrophages. Our results suggest milteforan as a possible alternative to treat feline sporotrichosis.

The glycerophosphocholine acyltransferase Gpc1 contributes to phosphatidylcholine biosynthesis, long-term viability, and embedded hyphal growth in Candida albicans

Candida albicans is a commensal fungus, opportunistic pathogen, and the most common cause of fungal infection in humans. The biosynthesis of phosphatidylcholine (PC), a major eukaryotic glycerophospholipid, occurs through two primary pathways. In Saccharomyces cerevisiae and some plants, a third PC synthesis pathway, the PC deacylation/reacylation pathway (PC-DRP), has been characterized. PC-DRP begins with the acylation of the lipid turnover product, glycerophosphocholine (GPC), by the GPC acyltransferase, Gpc1, to form Lyso-PC. Lyso-PC is then acylated by lysolipid acyltransferase, Lpt1, to produce PC. Importantly, GPC, the substrate for Gpc1, is a ubiquitous metabolite available within the host. GPC is imported by C. albicans, and deletion of the major GPC transporter, Git3, leads to decreased virulence in a murine model. Here we report that GPC can be directly acylated in C. albicans by the protein product of orf19.988, a homolog of ScGpc1. Through lipidomic studies, we show loss of Gpc1 leads to a decrease in PC levels. This decrease occurs in the absence of exogenous GPC, indicating that the impact on PC levels may be greater in the human host where GPC is available. A gpc1Δ/Δ strain exhibits several sensitivities to antifungals that target lipid metabolism. Furthermore, loss of Gpc1 results in both a hyphal growth defect in embedded conditions and a decrease in long-term cell viability. These results demonstrate for the first time the importance of Gpc1 and this alternative PC biosynthesis route (PC-DRP) to the physiology of a pathogenic fungus.

Candida parapsilosis complex in the clinical setting

Representatives of the Candida parapsilosis complex are important yeast species causing human infections, including candidaemia as one of the leading diseases. This complex comprises C. parapsilosis, Candida orthopsilosis and Candida metapsilosis, and causes a wide range of clinical presentations from colonization to superficial and disseminated infections with a high prevalence in preterm-born infants and the potential to cause outbreaks in hospital settings. Compared with other Candida species, the C. parapsilosis complex shows high minimal inhibitory concentrations for echinocandin drugs due to a naturally occurring FKS1 polymorphism. The emergence of clonal outbreaks of strains with resistance to commonly used antifungals, such as fluconazole, is causing concern. In this Review, we present the latest medical data covering epidemiology, diagnosis, resistance and current treatment approaches for the C. parapsilosis complex. We describe its main clinical manifestations in adults and children and highlight new treatment options. We compare the three sister species, examining key elements of microbiology and clinical characteristics, including the population at risk, disease manifestation and colonization status. Finally, we provide a comprehensive resource for clinicians and researchers focusing on Candida species infections and the C. parapsilosis complex, aiming to bridge the emerging translational knowledge and future therapeutic challenges associated with this human pathogen.

Miltefosine: A Repurposing Drug against Mucorales Pathogens

Mucorales are a group of non-septated filamentous fungi widely distributed in nature, frequently associated with human infections, and are intrinsically resistant to many antifungal drugs. For these reasons, there is an urgent need to improve the clinical management of mucormycosis. Miltefosine, which is a phospholipid analogue of alkylphosphocholine, has been considered a promising repurposing drug to be used to treat fungal infections. In the present study, miltefosine displayed antifungal activity against a variety of Mucorales species, and it was also active against biofilms formed by these fungi. Treatment with miltefosine revealed modifications of cell wall components, neutral lipids, mitochondrial membrane potential, cell morphology, and the induction of oxidative stress. Treated Mucorales cells also presented an increased susceptibility to SDS. Purified ergosterol and glucosylceramide added to the culture medium increased miltefosine MIC, suggesting its interaction with fungal lipids. These data contribute to elucidating the effect of a promising drug repurposed to act against some relevant fungal pathogens that significantly impact public health.

Miltefosine repositioning: A review of potential alternative antifungal therapy

Fungal infections are a global health problem with high mortality and morbidity rates. Available antifungal agents have high toxicity and pharmacodynamic and pharmacokinetic limitations. Moreover, the increased incidence of antifungal-resistant isolates and the emergence of intrinsically resistant species raise concerns about seeking alternatives for efficient antifungal therapy. In this context, we review literature data addressing the potential action of miltefosine (MFS), an anti-Leishmania and anticancer agent, as a repositioning drug for antifungal treatment. Here, we highlight the in vitro and in vivo data, MFS possible mechanisms of action, case reports, and nanocarrier-mediated MFS delivery, focusing on fungal infection therapy. Finally, many studies have demonstrated the promising antifungal action of MFS in vitro, but there is little or no data on antifungal activity in vertebrate animal models and clinical trials, so have a need to develop more research for the repositioning of MFS as an antifungal therapy.

Recurrent copy number variations in the human fungal pathogen Candida parapsilosis

Candida parapsilosis is an opportunistic fungal pathogen with increasing incidence in hospital settings worldwide; however, we lack a comprehensive understanding of the mechanisms promoting its virulence and drug resistance. Bergin et al. systematically quantify the frequency and effect of copy number variation (CNV) across 170 diverse clinical and environmental isolates of C. parapsilosis (Bergin SA, Zhao F, Ryan AP, Müller CA, Nieduszynski CA, Zhai B, Rolling T, Hohl TM, Morio F, Scully J, Wolfe KH, Butler G, 2022, mBio, https://doi.org/10.1128/mbio.01777-22). Using a combination of both short- and long-read whole genome sequencing techniques, they determine the structure and copy number of two CNVs that arose recurrently throughout the evolution of these isolates. Each CNV predominantly amplifies one coding sequence (ARR3 or RTA3); however, the amplitude and recombination breakpoints are variable across the isolates. Amplification of RTA3 correlates with drug resistance and deletion causes drug susceptibility. This study highlights the need for further research into the mechanisms and dynamics of CNV formation and the impact of these CNVs on virulence and drug resistance across diverse fungal pathogens.

Potential Inhibitory Effect of Miltefosine against Terbinafine-Resistant Trichophyton indotineae

Several prolonged and significant outbreaks of dermatophytosis caused by Trichophyton indotineae, a new emerging terbinafine-resistant species, have been ongoing in India in recent years, and have since spread to various countries outside Asia. Miltefosine, an alkylphosphocholine, is the most recently approved drug for the treatment of both visceral and cutaneous leishmaniasis. Miltefosine in vitro activity against terbinafine-resistant and susceptible T. mentagrophytes/T. interdigitale species complex, including T. indotineae, is limited. The current study aimed to assess miltefosine's in vitro activity against dermatophyte isolates, which are the most common causes of dermatophytosis. Miltefosine, terbinafine, butenafine, tolnaftate, and itraconazole susceptibility testing was performed using Clinical and Laboratory Standards Institute broth microdilution methods (CLSI M38-A3) against 40 terbinafine-resistant T. indotineae isolates and 40 terbinafine-susceptible T. mentagrophytes/T. interdigitale species complex isolates. Miltefosine had MIC ranges of 0.063-0.5 µg/mL and 0.125-0.25 µg/mL against both terbinafine-resistant and susceptible isolates. In terbinafine-resistant isolates, the MIC₅₀ and MIC₉₀ were 0.125 µg/mL and 0.25 µg/mL, respectively, and 0.25 µg/mL in susceptible isolates. Miltefosine had statistically significant differences in MIC results when compared to other antifungal agents (p-value 0.05) in terbinafine-resistant strains. Accordingly, the findings suggest that miltefosine has a potential activity for treating infections caused by terbinafine-resistant T. indotineae. However, further studies are needed to determine how well this in vitro activity translates into in vivo efficacy.

Systematic Analysis of Copy Number Variations in the Pathogenic Yeast Candida parapsilosis Identifies a Gene Amplification in RTA3 That is Associated with Drug Resistance

We analyzed the genomes of 170 C. parapsilosis isolates and identified multiple copy number variations (CNVs). We identified two genes, RTA3 (CPAR2_104610) and ARR3 (CPAR2_601050), each of which was the target of multiple independent amplification events. Phylogenetic analysis shows that most of these amplifications originated only once. For ARR3, which encodes a putative arsenate transporter, 8 distinct CNVs were identified, ranging in size from 2.3 kb to 10.5 kb with 3 to 23 copies. For RTA3, 16 distinct CNVs were identified, ranging in size from 0.3 kb to 4.5 kb with 2 to ~50 copies. One unusual amplification resulted in a DUP-TRP/INV-DUP structure similar to some human CNVs. RTA3 encodes a putative phosphatidylcholine (PC) floppase which is known to regulate the inward translocation of PC in Candida albicans. We found that an increased copy number of RTA3 correlated with resistance to miltefosine, an alkylphosphocholine drug that affects PC metabolism. Additionally, we conducted an adaptive laboratory evolution experiment in which two C. parapsilosis isolates were cultured in increasing concentrations of miltefosine. Two genes, CPAR2_303950 and CPAR2_102700, coding for putative PC flippases homologous to S. cerevisiae DNF1 gained homozygous protein-disrupting mutations in the evolved strains. Overall, our results show that C. parapsilosis can gain resistance to miltefosine, a drug that has recently been granted orphan drug designation approval by the United States Food and Drug Administration for the treatment of invasive candidiasis, through both CNVs or loss-of-function alleles in one of the flippase genes. IMPORTANCE Copy number variations (CNVs) are an important source of genomic diversity that have been associated with drug resistance. We identify two unusual CNVs in the human fungal pathogen Candida parapsilosis. Both target a single gene (RTA3 or ARR3), and they have occurred multiple times in multiple isolates. The copy number of RTA3, a putative floppase that controls the inward translocation of lipids in the cell membrane, correlates with resistance to miltefosine, a derivative of phosphatidylcholine (PC) that was originally developed as an anticancer drug. In 2021, miltefosine was designated an orphan drug by the United States Food and Drug Administration for the treatment of invasive candidiasis. Importantly, we find that resistance to miltefosine is also caused by mutations in flippases, which control the outward movement of lipids, and that many C. parapsilosis isolates are prone to easily acquiring an increased resistance to miltefosine.

In Vitro Antifungal Susceptibility Profile of Miltefosine against a Collection of Azole and Echinocandins Resistant Fusarium Strains

Fusarium species are filamentous fungi that cause a variety of infections in humans. Because they are commonly resistant to many antifungal drugs currently available in clinical settings, research into alternative targets in fungal cells and therapeutic approaches is required. The antifungal activity of miltefosine and four comparators, amphotericin B, voriconazole, itraconazole, and caspofungin, were tested in vitro against a collection of susceptible and resistant clinical (n = 68) and environmental (n = 42) Fusarium isolates. Amphotericin B (0.8 μg/mL) had the lowest geometric mean (GM) MICs/MECs values followed by miltefosine (1.44 μg/mL), voriconazole (2.15 μg/mL), caspofungin (7.23 μg/mL), and itraconazole (14.19 μg/mL). Miltefosine was the most effective agent against Fusarium isolates after amphotericin B indicating that miltefosine has the potential to be studied as a novel treatment for Fusarium infections.

Promising Anti-Biofilm Agents and Phagocytes Enhancers for the Treatment of Candida albicans Biofilm–Associated Infections

Little is known about the interactions among phagocytes and antifungal agents and the antifungal immunomodulatory activities on Candida species biofilms. Here, inhibition of C. albicans biofilms and the interactions among biofilms and phagocytes alone or in combination with essential oils, biological, and chemical agents, or fluconazole were investigated. Biofilm formation by a panel of 28 C. albicans clinical isolates from hospitalized patients, birds, and cattle was tested. The anti-biofilm activities of cinnamon and clove oils, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and Enterococcus faecalis cell-free supernatant (CFS) in comparison with fluconazole were investigated using crystal violet and XTT reduction assays, expression of hypha-specific and hyphal regulator genes, and scanning electron microscopy (SEM) analysis. Of the tested C. albicans isolates, 15 of 28 (53.6%) were biofilm producers. Cinnamon followed by E. faecalis–CFS, SDS, and CTAB was the most effective inhibitors of planktonic C. albicans and biofilms. Fluconazole was an ineffective inhibitor of C. albicans biofilms. Sessile minimal inhibitory concentration (SMIC₅₀) of cinnamon, SDS, CTAB, and E. faecalis–CFS downregulated the hypha-specific and regulator genes, albeit to various extents, when compared with untreated biofilms (P < 0.001). SEM analysis revealed disruption and deformity of three-dimensional structures in cinnamon oil–treated biofilms. C. albicans sessile cells within biofilm were less susceptible to phagocytosis than planktonic cells. The additive effects of phagocytes and the tested antifungals enabled phagocytes to engulf C. albicans cells rapidly in cinnamon, E. faecalis–CFS, or SDS-treated biofilms. No differences in anti-Candida or anti-biofilm eradication activities were detected among the tested isolates. Our findings reinforce the substantial anti-biofilm activity of cinnamon oil, SDS, and E. faecalis–CFS and provide new avenues for the development of novel anti-biofilm immunotherapies or antifungals that could be used prior to or during the management of cases with biofilm-associated infections.

Invasive candidiasis: Investigational drugs in the clinical development pipeline and mechanisms of action

INTRODUCTION

The epidemiology of invasive Candida infections is evolving. Infections caused by non-albicans Candida spp. are increasing; however, the antifungal pipeline is more promising than ever and is enriched with repurposed drugs and agents that have new mechanisms of action. Despite progress, unmet needs in the treatment of invasive candidiasis remain and there are still too few antifungals that can be administered orally or that have CNS penetration.

AREAS COVERED

The authors shed light on those antifungal agents active against Candida that are in late-stage clinical development. Mechanisms of action and key pharmacokinetic and pharmacodynamic properties are discussed. Insights are offered on the potential future roles of the investigational agents MAT-2203, oteseconazole, ATI-2307, VL-2397, NP-339, and the repurposed drug miltefosine.

EXPERT OPINION

Ibrexafungerp and fosmanogepix have novel mechanisms of action and will provide effective options for the treatment of Candida infections (including those caused by multiresistant Candida spp). Rezafungin, an echinocandin with an extended half-life allowing for once weekly administration, will be particularly valuable for outpatient treatment and prophylaxis. Despite this, there is an urgent need to garner clinical data on investigational drugs, especially in the current rise of azole-resistant and multi-drug resistant Candida spp.

Intestinal Infection of Candida albicans: Preventing the Formation of Biofilm by C. albicans and Protecting the Intestinal Epithelial Barrier

The large mortality and morbidity rate of C. albicans infections is a crucial problem in medical mycology. Because the generation of biofilms and drug resistance are growing concerns, the growth of novel antifungal agents and the looking for newer objectives are necessary. In this review, inhibitors of C. albicans biofilm generation and molecular mechanisms of intestinal epithelial barrier protection are elucidated. Recent studies on various transcription elements; quorum-sensing molecules; host responses to adherence; and changes in efflux pumps, enzymes, bud to hyphal transition, and lipid profiles have increased the knowledge of the intricate mechanisms underlying biofilm resistance. In addition, the growth of novel biomaterials with anti-adhesive nature, natural products, drugs, bioactive compounds, proteins, lipids, and carbohydrates are being researched. Recently, more and more attention has been given to various metal nanoparticles that have also appeared as antibiofilm agents in C. albicans. The intestinal epithelial obstacle exerts an crucial effect on keeping intestinal homeostasis and is increasingly associated with various disorders associated with the intestine such as inflammatory bowel disease (IBD), irritable bowel syndrome, metabolic syndrome, allergies, hepatic inflammation, septic shock, etc. However, whether their involvement in the prevention of other intestinal disorders like IBD are useful in C. albicans remains unknown. Further studies must be carried out in order to validate their inhibition functions in intestinal C. albicans. This provides innovates ideas for intestinal C. albicans treatment.

Miltefosine Against Scedosporium and Lomentospora Species: Antifungal Activity and Its Effects on Fungal Cells

Scedosporium and Lomentospora species are filamentous fungi responsible for a wide range of infections in humans and are frequently associated with cystic fibrosis and immunocompromising conditions. Because they are usually resistant to many antifungal drugs available in clinical settings, studies of alternative targets in fungal cells and therapeutic approaches are necessary. In the present work, we evaluated the in vitro antifungal activity of miltefosine against Scedosporium and Lomentospora species and how this phospholipid analogue affects the fungal cell. Miltefosine inhibited different Scedosporium and Lomentospora species at 2–4 µg/ml and reduced biofilm formation. The loss of membrane integrity in Scedosporium aurantiacum caused by miltefosine was demonstrated by leakage of intracellular components and lipid raft disorganisation. The exogenous addition of glucosylceramide decreased the inhibitory activity of miltefosine. Reactive oxygen species production and mitochondrial activity were also affected by miltefosine, as well as the susceptibility to fluconazole, caspofungin and myoricin. The data obtained in the present study contribute to clarify the dynamics of the interaction between miltefosine and Scedosporium and Lomentospora cells, highlighting its potential use as new antifungal drug in the future.

Recent advances and future perspectives in the pharmacological treatment of Candida auris infections

INTRODUCTION

Candida auris is responsible for hospital outbreaks worldwide. Some C. auris isolates may show concomitant resistance to azoles, echinocandins, and polyenes, thereby possibly leaving clinicians with few therapeutic options.

AREAS COVERED

Antifungal agents both in early and in late phases of clinical development showing anti-C. auris activity.

EXPERT OPINION

The research on antifungal agents active against C. auris has made important steps forward in recent years: (i) the development of drugs with novel mechanisms of action, such as ibrexafungerp and fosmanogepix, could provide a valid option against C. auris strains resistant to one or more older antifungals, including pan-resistant strains; (ii) rezafungin could allow once weekly administration of an active drug in the case of echinocandin-susceptible isolates, providing an effective outpatient treatment, while at the same time relieving selective pressure on novel classes; (iii) the development of oral formulations could allow step-down therapy and/or early discharge, or even to avoid hospitalization in mild or noninvasive diseases; (iv) according to available data, these novel agents show a good safety profile and a low potential for drug-drug interactions.

New weapons to fight a new enemy: A systematic review of drug combinations against the drug-resistant fungus Candida auris

Candida auris is an emerging and drug-resistant pathogen. Drug combination is a promising approach against such pathogens. This study was conducted to provide an overview of all the studied drug combinations against C. auris. Relevant articles reporting results of any drug/non-drug combinations against C. auris were found by a systematic search in PubMed, Scopus and Web of Science (ISI), and in Google Scholar up to 1 October 2020. From 187 articles retrieved in the primary search, 23 met the inclusion criteria. In total, 124 different combinations including antifungal with antifungal (45), antifungal with other antimicrobials (11), antifungal with non-antimicrobials (32), antifungal with natural compounds (25) and between natural compounds (11) have been reported. Complete or partial synergistic effects have been reported for 3 out of 45 (6.67%) combinations of two antifungal agents, 8 out of 11 (72.73%) combinations involving antifungal agents and antimicrobials, 15 out of 32 (46.88%) of combinations between antifungal agents with non-antimicrobials, 16 out of 25 (64%) of combinations involving antifungal agents and natural compounds, and 3 out of 11 (22.27%) of combinations involving multiple natural compounds. Antagonistic interactions have been reported for 1 out of 32 (3.13%) and 8 out of 25 (32%) of combinations between antifungal drugs with non-antimicrobials and with natural compounds, respectively. Different drugs/compounds could potentiate the activity of antifungal drugs using this approach. However, despite the availability of this promising initial data, many more studies will be required to elucidate whether favourable interactions observed in vitro might translate into tangible clinical benefits.

Caspofungin and Polymyxin B Reduce the Cell Viability and Total Biomass of Mixed Biofilms of Carbapenem-Resistant Pseudomonas aeruginosa and Candida spp

Pseudomonas aeruginosa and Candida spp. are biofilm-forming pathogens commonly found colonizing medical devices, being mainly associated with pneumonia and bloodstream infections. The coinfection by these pathogens presents higher mortality rates when compared to those caused by a single microbial species. This study aimed to evaluate the antibiofilm activity of echinocandins and polymyxin B (PMB) against polymicrobial biofilms of carbapenem-resistant (CR) Pseudomonas aeruginosa and Candida spp. (C. albicans, C. parapsilosis, C. tropicalis, and C. glabrata). In addition, we tested the antimicrobial effect on their planktonic and monomicrobial biofilm counterparties. Interestingly, beyond inhibition of planktonic [minimum inhibitory concentration (MIC) = 0.5 μg/ml] and biofilm [minimum biofilm inhibitory concentration (MBIC)₅₀ ≤ 2–8 μg/ml] growth of P. aeruginosa, PMB was also effective against planktonic cells of C. tropicalis (MIC = 2 μg/ml), and polymicrobial biofilms of CR P. aeruginosa with C. tropicalis (MBIC₅₀ ≤ 2 μg/ml), C. parapsilosis (MBIC₅₀ = 4–16 μg/ml), C. glabrata (MBIC₅₀ = 8–16 μg/ml), or C. albicans (MBIC₅₀ = 8–64 μg/ml). On the other hand, while micafungin (MFG) showed highest inhibitory activity against planktonic (MIC ≤ 0.008–0.5 μg/ml) and biofilm (MBIC₅₀ ≤ 2–16 μg/ml) growth of Candida spp.; caspofungin (CAS) displays inhibitory activity against planktonic cells (MIC = 0.03–0.25 μg/ml) and monomicrobial biofilms (MBIC₅₀ ≤ 2–64 μg/ml) of Candida spp., and notably on planktonic and monomicrobial biofilms of CR P. aeruginosa (MIC or MBIC₅₀ ≥ 64 μg/ml). Particularly, for mixed biofilms, while CAS reduced significantly viable cell counts of CR P. aeruginosa and Candida spp. at ≥32 and ≥ 2 μg/ml, respectively; PMB was effective in reducing viable cells of CR P. aeruginosa at ≥2 μg/ml and Candida spp. at ≥8 μg/ml. Similar reduction of viable cells was observed for CAS (32–64 μg/ml) combined with PMB (2 μg/ml). These findings highlight the potential of PMB and CAS for the treatment of polymicrobial infections caused by Candida spp. and critical priority CR P. aeruginosa.

Virulence Factors and Antifungal Susceptibility in Candida Species Isolated from Dermatomycosis Patients

Dermatomycoses caused by Candida spp. are increasingly common, however there are few reports in the literature regarding their epidemiology, pathogenesis and antifungal susceptibility of these fungal pathogens. This study aimed to identify, characterize virulence and determine the antifungal susceptibility of Candida species isolated from patients with dermatomycoses. We studied a total of 45 yeast samples isolated from dermal scrapings from patients treated at a public hospital, Bauru, São Paulo, Brazil. After identification, the samples were analyzed for protease activity, phospholipase, biofilm formation and antifungal susceptibility. The most common species was Candida albicans (40%), followed by C. krusei (22.22%), C. parapsilosis complex (22.22%) and C. famata (6.67%). Regarding virulence mechanisms, 57.78% and 28.89% of the samples showed enzymatic activity for protease and phospholipase, respectively. A total of 13.33% of the samples showed secretion of both enzymes. All isolates were biofilm producers, and a higher production was observed in C. tropicalis isolates. Regarding the antifungal susceptibility test, 97.78% of the samples had the highest levels of the minimal inhibitory concentration (MIC) for terbinafine, and one C. krusei sample showed intermediate susceptibility to fluconazole. The correct identification of dermatomycosis-related microorganisms, as well as a better knowledge of their pathogenicity and susceptibility against the antifungals used in the clinic, is extremely important for an efficient preventive and therapeutic action.

Carrier-Mediated Drug Uptake in Fungal Pathogens

Candida, Aspergillus, and Cryptococcus species are the most frequent cause of severe human fungal infections. Clinically relevant antifungal drugs are scarce, and their effectiveness are hampered by the ability of fungal cells to develop drug resistance mechanisms. Drug effectiveness and drug resistance in human pathogens is very often affected by their “transportome”. Many studies have covered a panoply of drug resistance mechanisms that depend on drug efflux pumps belonging to the ATP-Binding Cassette and Major Facilitator Superfamily. However, the study of drug uptake mechanisms has been, to some extent, overlooked in pathogenic fungi. This review focuses on discussing current knowledge on drug uptake systems in fungal pathogens, highlighting the need for further studies on this topic of great importance. The following subjects are covered: (i) drugs imported by known transporter(s) in pathogenic fungi; and (ii) drugs imported by known transporter(s) in the model yeast Saccharomyces cerevisiae or in human parasites, aimed at the identification of their homologs in pathogenic fungi. Besides its contribution to increase the understanding of drug-pathogen interactions, the practical implications of identifying drug importers in human pathogens are discussed, particularly focusing on drug development strategies.

Alternative treatment of fungal infections: Synergy with non-antifungal agents

Fungal infections are responsible for high mortality rates in immunocompromised and high-risk surgical patients. Therapy failures during the last decades due to increasing multidrug resistance demand innovative strategies for novel and effective antifungal drugs. Synergistic combinations of antifungals with non-antifungal agents highlight a pragmatic strategy to reduce the development of drug resistance and potentially repurpose known compounds with other functions to bypass costly and time-consuming novel drug development.

Screening Repurposing Libraries for Identification of Drugs with Novel Antifungal Activity

Fungal organisms are ubiquitous in nature, and progress of modern medicine is creating an expanding number of severely compromised patients susceptible to a variety of opportunistic fungal infections. These infections are difficult to diagnose and treat, leading to high mortality rates. The limited antifungal arsenal, the toxicity of current antifungal drugs, the development of resistance, and the emergence of new multidrug-resistant fungi, all highlight the urgent need for new antifungal agents. Unfortunately, the development of a novel antifungal is a rather long and expensive proposition, and no new classes of antifungal agents have reached the market in the last 2 decades. Drug repurposing, or finding new indications for old drugs, represents a promising alternative pathway to drug development that is particularly appealing within the academic environment. In the last few years, there has been a growing interest in repurposing approaches in the antifungal arena, with multiple groups of investigators having performed screenings of different repurposing libraries against different pathogenic fungi in search for drugs with previously unrecognized antifungal effects. Overall, these repurposing efforts may lead to the fast deployment of drugs with novel antifungal activity, which can rapidly bring benefits to patients, while at the same time reducing health care costs.

Fungistatic Action of N-Acetylcysteine on Candida albicans Biofilms and Its Interaction with Antifungal Agents

Therapies targeted to fungal biofilms, mainly against the matrix, and therapies that do not induce microbial resistance are relevant. N-acetylcysteine (NAC), a mucolytic agent, has shown antimicrobial action. This study evaluated the effect of NAC against fluconazole-susceptible (CaS) and -resistant (CaR) Candida albicans. The susceptibility of planktonic cultures to NAC, the effect of NAC on biofilms and their matrix, the interaction of NAC with antifungal agents, and confocal microscopy were evaluated. Data were analyzed descriptively and by the ANOVA/Welch and Tukey/Gomes-Howell tests. The minimum inhibitory concentration (MIC) of NAC was 25 mg/mL for both strains. NAC significantly reduced the viability of both fungal strains. Concentrations higher than the MIC (100 and 50 mg/mL) reduced the viability and the biomass. NAC at 12.5 mg/mL increased the fungal viability. NAC also reduced the soluble components of the biofilm matrix, and showed synergism with caspofungin against planktonic cultures of CaS, but not against biofilms. Confocal images demonstrated that NAC reduced the biofilm thickness and the fluorescence intensity of most fluorochromes used. High concentrations of NAC had similar fungistatic effects against both strains, while a low concentration showed the opposite result. The antibiofilm action of NAC was due to its fungistatic action.

Potassium iodide and miltefosine inhibit biofilms of Sporothrix schenckii species complex in yeast and filamentous forms

This study aimed to evaluate the yeast biofilm growth kinetics and ultrastructure of Sporothrix schenckii complex and assess their mature biofilm susceptibility in filamentous and yeast forms to potassium iodide (KI) and miltefosine (MIL). Yeast biofilms were evaluated by crystal violet staining, XTT reduction assay and microscopic techniques. Susceptibility of planktonic and sessile cells was analyzed by broth microdilution. S. schenckii complex in yeast form produced biofilms, with an optimum maturation at 96 h, showing multilayered blastoconidia embedded in extracellular matrix. KI and MIL minimum inhibitory concentration (MIC) ranges against planktonic cells were 62,500-250,000 μg/ml and 0.125-4 μg/ml, respectively. KI and MIL reduced biofilm metabolic activity by 75.4% and 67.7% for filamentous form and 55.1% and 51.6% for yeast form, respectively. This study demonstrated that S. schenckii complex forms biofilms in vitro, and potassium iodide and miltefosine inhibit Sporothrix spp. biofilms in both filamentous and yeast forms.

Miltefosine as an alternative strategy in the treatment of the emerging fungus Candida auris

OBJECTIVES

Candida auris (C. auris) is an emerging fungal species that is able to develop multidrug resistance and outbreaks of invasive infections worldwide with high mortality rates. To increase the treatment options for C. auris infection this study assessed the efficacy of miltefosine (MFS), that has demonstrated a broad-spectrum antifungal action in vitro. This study aimed to: (i) evaluate the in vitro antifungal activity of MFS against C. auris clinical isolates in the planktonic and biofilm lifestyles; and (ii) compare the activity of MFS in its free form and encapsulated in alginate nanoparticles (MFS-AN) in Galleria mellonella larvae infected by C. auris.

METHODS

The antifungal susceptibility test was performed using broth microdilution method and the in vivo treatment in Galleria mellonella larval infection model.

RESULTS

MFS exhibited in vitro inhibitory effects at MICs ranging 1-4 µg/mL and fungicidal activity against planktonic cells of C. auris clinical isolates. MFS antibiofilm activity was observed during biofilm formation (0.25-4 µg/mL) and on pre-formed biofilms (16-32 µg/mL). Moreover, the dispersed cells from C. auris biofilms had a similar susceptibility to those obtained for planktonic cells. Treatment with free MFS or MFS-AN resulted in significant improvements in the survival and morbidity rates of Galleria mellonella larvae infected by C. auris. In addition, reduction of fungal burden (0.5-1 log CFU/g) and granuloma formation were observed when compared with the untreated group.

CONCLUSIONS

The findings suggest that both the free MFS and MFS-AN have potential for the treatment of fungal infections caused by the emerging C. auris.

Antifungal Activity and Mode of Action of Miltefosine Against Clinical Isolates of Candida krusei

Candida krusei attracts attention from medical professionals mainly for its intrinsic resistance to fluconazole and the limited number of drugs available to treat C. krusei vulvovaginal candidiasis. Miltefosine was demonstrated to have good antifungal activity both in vitro and in vivo. Here, we determined the susceptibility profiles of 57 clinical C. krusei isolates from vulvovaginal candidiasis patients and assessed the antifungal activity of miltefosine against C. krusei. All isolates were susceptible to voriconazole and itraconazole, whereas 1.8% of the isolates were of non-wild-type phenotype to amphotericin B. In contrast, miltefosine showed low MICs against all C. krusei isolates with fungicidal activity. The checkerboard assay showed that the synergistic effect of miltefosine in combination with amphotericin B was observed in 25% of the tested planktonic C. krusei isolates and 18.8% of the tested preformed biofilms, whereas miltefosine in combination with fluconazole showed indifferent interaction for all tested planktonic isolates. The presence of sorbitol in the broth microdilution assay did not influence the MIC values of miltefosine against C. krusei, but the presence of ergosterol increased the MIC values. Visible changes in cell content in cells treated with miltefosine were observed. We found that cells treated with miltefosine showed decreased cell viability and chromatin condensation under PI staining, which indicates that miltefosine may induce apoptosis-like cell death in C. krusei. In conclusion, we found miltefosine has a good activity against C. krusei isolates and exerts its fungicidal effect by binding to ergosterol in the cell membrane and inducing apoptosis.

Nanocarriers Provide Sustained Antifungal Activity for Amphotericin B and Miltefosine in the Topical Treatment of Murine Vaginal Candidiasis

Topical drug administration is frequently used for the treatment of vaginal candidiasis; however, most formulations using this route do not provide prolonged drug release. Our aim was to evaluate the antifungal efficacy of amphotericin B (AMB) and miltefosine (MFS) incorporated in nanocarriers for sustained drug release, in a murine model of vaginal candidiasis. AMB and MFS were incorporated in different topical formulations, namely: conventional vaginal cream (daily dose for 6 days; MFS-CR and AMB-CR groups), microemulsion that transforms into a liquid crystalline gel in situ (single dose, or in three doses, every 48 h; AMB-ME and MFS-ME groups) and alginate nanoparticles (single dose; MFS-AN group). Formulations were administered intravaginally in BALB/c female mice 24 h post-infection by Candida albicans yeasts. On the 7th day post-infection the animals were euthanized for mycological and histological analyses. Formulation persistence in the vaginal canal was assessed for 7 days by in vivo imaging, using nanocarriers labeled with Alexa-Fluor 647. AMB-ME(3×), MFS-ME(3×), and MFS-AN(1×) formulations were able to control fungal infection at comparable levels to those vaginal cream formulations. Notably, a single dose of MFS-AN was sufficient to reduce the fungal burden as effectively as MFS-ME(3×) and MFS-CR(6×). In vivo imaging showed that nanocarriers allowed prolonged antifungal activity by intravaginal administration reducing drug administration frequency. Therefore, AMB and MFS incorporated into a microemulsion and MFS encapsulated in alginate nanoparticles could be effective therapeutic alternatives for vaginal candidiasis, likely due to the sustained antifungal activity provided by these nanocarriers.

G-protein-coupled Receptors in Fungi

G-protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors in fungi. These receptors have an important role in the transduction of extracellular signals into intracellular sites in response to diverse stimuli. They enable fungi to coordinate cell function and metabolism, thereby promoting their survival and propagation, and sense certain fundamentally conserved elements, such as nutrients, pheromones, and stress, for adaptation to their niches, environmental stresses, and host environment, causing disease and pathogen virulence. This chapter highlights the role of GPCRs in fungi in coordinating cell function and metabolism. Fungal cells sense the molecular interactions between extracellular signals. Their respective sensory systems are described here in detail.

Alginate nanoparticles as non-toxic delivery system for miltefosine in the treatment of candidiasis and cryptococcosis

Introduction and objective

Previous studies indicate that miltefosine (MFS) may be an alternative as an antifungal agent; however, it presents several adverse effects. Thus, the aim of this study was to produce miltefosine-loaded alginate nanoparticles (MFS.Alg) for toxicity reduction to be used as an alternative for the treatment of cryptococcosis and candidiasis.

Methods

Alginate nanoparticles were produced using the external emulsification/gelation method, and their physicochemical and morphological characteristics were analyzed. MFS encapsulation efficiency, release assay and toxicity on red blood cells and on Galleria mellonella larvae were assessed. The antifungal activity was evaluated using in vitro and in vivo larval models of G. mellonella infected with Candida albicans (SC5314 and IAL-40), Cryptococcus neoformans H99 and Cryptococcus gattii ATCC 56990. The treatment efficacy was evaluated by survival curve, colony forming unit (CFU) counting and histopathological analysis.

Results

MFS.Alg nanoparticles presented a mean size of 279.1±56.7 nm, a polydispersity index of 0.42±0.15 and a zeta potential of -39.7±5.2 mV. The encapsulation efficiency of MFS was 81.70±6.64%, and its release from the nanoparticles occurred in a sustained manner. MFS in alginate nanoparticles presented no hemolytic effect and no toxicity in G. mellonella larvae. Treatment with MFS.Alg extended the survival time of larvae infected with C. albicans and C. gattii. In addition, the fungal burden reduction was confirmed by CFU and histopathological data for all groups treated with 200 mg/Kg of MFS.Alg.

Conclusion

These results support the use of alginate-based drug delivery systems as carriers for MFS for drug toxicity reduction and control of the fungal infection in the in vivo model of G. mellonella.

A Practical Guide to Curing Onychomycosis: How to Maximize Cure at the Patient, Organism, Treatment, and Environmental Level

Onychomycosis is a fungal nail infection caused by dermatophytes, non-dermatophyte molds, and yeasts. Treatment of this infection can be difficult, with relapse likely to occur within 2.5 years of cure. The objective of this article is to review factors that can impact cure and to suggest practical techniques that physicians can use to maximize cure rates. Co-morbidities, as well as disease severity and duration, are among the many patient factors that could influence the efficacy of antifungal therapies. Furthermore, organism, treatment, and environmental factors that may hinder cure include point mutations, biofilms, affinity for non-target enzymes, and exposure to fungal reservoirs. To address patient-related factors, physicians are encouraged to conduct confirmatory testing and treat co-morbidities such as tinea pedis early and completely. To combat organism-focused factors, it is recommended that disruption of biofilms is considered, and drugs with multiple routes of delivery and unique mechanisms of action are prescribed when traditional agents are not effective. Extending follow-up periods, using combination treatments, and considering pulse regimens may also be of benefit. Through these practical techniques, physicians can maximize cure and limit the risk of relapse and re-infection.

New N-(oxazolylmethyl)-thiazolidinedione Active against Candida albicans Biofilm: Potential Als Proteins Inhibitors

C. albicans is the most frequently occurring fungal pathogen, and is becoming an increasing public health problem, especially in the context of increased microbial resistance. This opportunistic pathogen is characterized by a versatility explained mainly by its ability to form complex biofilm structures that lead to enhanced virulence and antibiotic resistance. In this context, a review of the known C. albicans biofilm formation inhibitors were performed and a new N-(oxazolylmethyl)-thiazolidinedione scaffold was constructed. 16 new compounds were synthesized and characterized in order to confirm their proposed structures. A general antimicrobial screening against Gram-positive and Gram-negative bacteria, as well as fungi, was performed and revealed that the compounds do not have direct antimicrobial activity. The anti-biofilm activity evaluation confirmed the compounds act as selective inhibitors of C. albicans biofilm formation. In an effort to substantiate this biologic profile, we used in silico investigations which suggest that the compounds could act by binding, and thus obstructing the functions of, the C. albicans Als surface proteins, especially Als1, Als3, Als5 and Als6. Considering the well documented role of Als1 and Als3 in biofilm formation, our new class of compounds that target these proteins could represent a new approach in C. albicans infection prevention and management.

Miltefosine Has a Postantifungal Effect and Induces Apoptosis in Cryptococcus Yeasts

Cryptococcus spp. are common opportunistic fungal pathogens, particularly in HIV patients. The approved drug miltefosine (MFS) has potential as an alternative antifungal against cryptococcosis; however, the mechanism of action of MFS in Cryptococcus is poorly understood. Here, we examined the effects of MFS on C. neoformans and C. gattii yeasts (planktonic and biofilm lifestyles) to clarify its mechanism of action. MFS presented inhibitory and fungicidal effects against planktonic Cryptococcus cells, with similar activities against dispersion biofilm cells, while sessile biofilm cells were less sensitive to MFS. Interestingly, MFS had postantifungal effect on Cryptococcus, with a proliferation delay of up to 8.15 h after a short exposure to fungicidal doses. MFS at fungicidal concentrations increased the plasma membrane permeability, likely due to a direct interaction with ergosterol, as suggested by competition assays with exogenous ergosterol. Moreover, MFS reduced the mitochondrial membrane potential, increased reactive oxygen species (ROS) production, and induced DNA fragmentation and condensation, all of which are hallmarks of apoptosis. Transmission electron microscopy analysis showed that MFS-treated yeasts had a reduced mucopolysaccharide capsule (confirmed by morphometry with light microscopy), plasma membrane irregularities, mitochondrial swelling, and a less conspicuous cell wall. Our results suggest that MFS increases the plasma membrane permeability in Cryptococcus via an interaction with ergosterol and also affects the mitochondrial membrane, eventually leading to apoptosis, in line with its fungicidal activity. These findings confirm the potential of MFS as an antifungal against C. neoformans and C. gattii and warrant further studies to establish clinical protocols for MFS use against cryptococcosis.

Evidence for biofilms in onychomycosis

Onychomycosis is a difficult to treat fungal infection of the nails. The chronic nature of onychomycosis contributes to high recurrence rates and the difficulty in treating both dermatophyte and non-dermatophyte infections. It has been hypothesized that the formation of biofilms, sessile, multicellular communities of fungi surrounded by a protective extracellular matrix, allow for fungi to evade current antifungal therapies and contribute to observed antifungal resistance. This review presents the experimental evidence that has accumulated in recent years implicating biofilms in the pathogenesis of onychomycosis. Dermatophytes, non-dermatophyte molds, and yeasts form biofilms in vitro and a model using ex vivo healthy nail fragments has demonstrated biofilm formation on nails for dermatophyte, Candida, and Fusarium species. Implications for disease management are discussed with further research required to incorporate biofilm formation into future drug/device evaluation and treatment protocols.

In Vitro Activities of Miltefosine and Antibacterial Agents from the Macrolide, Oxazolidinone, and Pleuromutilin Classes against Pythium insidiosum and Pythium aphanidermatum

We tested 29 isolates of Pythium insidiosum and one isolate of Pythium aphanidermatum to investigate their susceptibility to miltefosine and antibacterial drugs from the macrolide, oxazolidinone, and pleuromutilin classes. We found that miltefosine, azithromycin, clarithromycin, josamycin, linezolid, sutezolid, retapamulin, tiamulin, and valnemulin had inhibitory and cidal activity against the pathogens at concentrations ranging from 0.25 to 64 μg/ml. Our results suggest that these antimicrobials are promising candidates for future studies on pythiosis in animals and humans.

Chemogenomic Profiling of the Fungal Pathogen Candida albicans

There is currently a small number of classes of antifungal drugs, and these drugs are known to target a very limited set of cellular functions. We derived a set of approximately 900 nonessential, transactivator-defective disruption strains from the tetracycline-regulated GRACE collection of strains of the fungal pathogen Candida albicans This strain set was screened against classic antifungal drugs to identify gene inactivations that conferred either enhanced sensitivity or increased resistance to the compounds. We examined two azoles, fluconazole and posaconazole; two echinocandins, caspofungin and anidulafungin; and a polyene, amphotericin B. Overall, the chemogenomic profiles within drug classes were highly similar, but there was little overlap between classes, suggesting that the different drug classes interacted with discrete networks of genes in C. albicans We also tested two pyridine amides, designated GPI-LY7 and GPI-C107; these drugs gave very similar profiles that were distinct from those of the echinocandins, azoles, or polyenes, supporting the idea that they target a distinct cellular function. Intriguingly, in cases where these gene sets can be compared to genetic disruptions conferring drug sensitivity in other fungi, we find very little correspondence in genes. Thus, even though the drug targets are the same in the different species, the specific genetic profiles that can lead to drug sensitivity are distinct. This implies that chemogenomic screens of one organism may be poorly predictive of the profiles found in other organisms and that drug sensitivity and resistance profiles can differ significantly among organisms even when the apparent target of the drug is the same.

Distinct roles of the 7-transmembrane receptor protein Rta3 in regulating the asymmetric distribution of phosphatidylcholine across the plasma membrane and biofilm formation in Candida albicans

Fungal pathogens such as Candida albicans exhibit several survival mechanisms to evade attack by antifungals and colonise host tissues. Rta3, a member of the Rta1-like family of lipid-translocating exporters has a 7-transmembrane domain topology, similar to the G-protein-coupled receptors and is unique to the fungal kingdom. Our findings point towards a role for the plasma membrane localised Rta3 in providing tolerance to miltefosine, an analogue of alkylphosphocholine, by maintaining mitochondrial energetics. Concurrent with miltefosine susceptibility, the rta3Δ/Δ strain displays increased inward translocation (flip) of fluorophore-labelled phosphatidylcholine (PC) across the plasma membrane attributed to enhanced PC-specific flippase activity. We also assign a novel role to Rta3 in the Bcr1-regulated pathway for in vivo biofilm development. Transcriptome analysis reveals that Rta3 regulates expression of Bcr1 target genes involved in cell surface properties, adhesion, and hyphal growth. We show that rta3Δ/Δ mutant is biofilm-defective in a rat venous catheter model of infection and that BCR1 overexpression rescues this defect, indicating that Bcr1 functions downstream of Rta3 to mediate biofilm formation in C. albicans. The identification of this novel Rta3-dependent regulatory network that governs biofilm formation and PC asymmetry across the plasma membrane will provide important insights into C. albicans pathogenesis.