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.

Enniatins from a marine-derived fungus Fusarium sp. inhibit biofilm formation by the pathogenic fungus Candida albicans

Candidemia is a life-threatening disease common in immunocompromised patients, and is generally caused by the pathogenic fungus Candida albicans. C. albicans can change morphology from yeast to hyphae, forming biofilms on medical devices. Biofilm formation contributes to the virulence and drug tolerance of C. albicans, and thus compounds that suppress this morphological change and biofilm formation are effective for treating and preventing candidemia. Marine organisms produce biologically active and structurally diverse secondary metabolites that are promising lead compounds for treating numerous diseases. In this study, we explored marine-derived fungus metabolites that can inhibit morphological change and biofilm formation by C. albicans. Enniatin B (1), B1 (2), A1 (3), D (4), and E (5), visoltricin (6), ergosterol peroxide (7), 9,11-dehydroergosterol peroxide (8), and 3β,5α,9α-trihydroxyergosta-7,22-dien-6-one (9) were isolated from the marine-derived fungus Fusarium sp. Compounds 1-5 and 8 exhibited inhibitory activity against hyphal formation by C. albicans, and compounds 1-3 and 8 inhibited biofilm formation by C. albicans. Furthermore, compounds 1-3 decreased cell surface hydrophobicity and expression of the hypha-specific gene HWP1 in C. albicans. Compound 1 was obtained in the highest yield. An in vivo evaluation system using silkworms pierced with polyurethane fibers (a medical device substrate) showed that compound 1 inhibited biofilm formation by C. albicans in vivo. These results indicate that enniatins could be lead compounds for therapeutic agents for biofilm infections by C. albicans.

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.

Antifungal effects of alantolactone on Candida albicans: An in vitro study

The human fungal pathogen Candida albicans can cause many kinds of infections, including biofilm infections on medical devices, while the available antifungal drugs are limited to only a few. In this study, alantolactone (Ala) demonstrated antifungal activities against C. albicans, as well as other Candida species, with a MIC of 72 μg/mL. Ala could also inhibit the adhesion, yeast-to-hyphal transition, biofilm formation and development of C. albicans. The exopolysaccharide of biofilm matrix and extracellular phospholipase production could also be reduced by Ala treatment. Ala could increase permeability of C. albicans cell membrane and ROS contribute to the anti-biofilm activity of Ala. Overall, the present study suggests that Ala may provide a promising candidate for developing antifungal drugs against C. albicans infections.

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.

Evaluation of Anti-Biofilm Capability of Cordycepin Against Candida albicans

Introduction

The opportunistic pathogen Candida albicans can form biofilms, resulting in drug resistance with great risk to medical treatment.

Methodology

We investigated the ability of C. albicans to form biofilms on different materials, as well as the inhibitory and eradicating effects of cordycepin on biofilm. The action mechanism of cordycepin against biofilm was studied by crystal violet staining, XTT [2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction method, phenol-sulfuric acid method, cellular superficial hydrophobicity (CSH) assay, and confocal laser scanning microscope observation. We also evaluated the acute toxicity of cordycepin in vivo.

Results

The results showed facile formation of biofilms by C. albicans on polypropylene. The 50% minimum inhibitory concentration (MIC₅₀) of cordycepin was 0.062 mg/mL. A concentration of 0.125 mg/mL significantly decreased biofilm formation, metabolic activity, secretion of extracellular polysaccharides, and relative CSH. Cordycepin could inhibit biofilm formation at low concentration without affecting fungal growth. In addition, cordycepin effectively eradicated 59.14% of mature biofilms of C. albicans at a concentration of 0.5 mg/mL. For acute toxicity, the LD₅₀ (50% of lethal dose) of cordycepin was determined as higher than 500 mg/kg for mice.

Conclusion

The results of this study show that cordycepin significantly inhibited and eradicated biofilms by decreasing metabolic activity, the ratio of living cells, the hydrophobicity, and damaging the extracellular polysaccharides of biofilm. These findings should facilitate more effective application of cordycepin and suggest a new direction for the treatment of fungal infections.

(PhSe)2 and (pCl-PhSe)2 organochalcogen compounds inhibit Candida albicans adhesion to human endocervical (HeLa) cells and show anti-biofilm activities

Adhesion capacity on biological surfaces and biofilm formation is considered an important step in the infection process by Candida albicans. The ability of (PhSe)₂ and (pCl-PhSe)₂, two synthetic organic selenium (organochalcogen) compounds, to act on C. albicans virulence factors related to adhesion to human endocervical (HeLa) cell surfaces and their anti-biofilm activities was analyzed. Both organochalcogen compounds inhibited C. albicans adhesion to HeLa cells, dependent on compound concentrations. (PhSe)₂ (at 20 µM; p = 0.0012) was significantly more effective than (pCl-PhSe)₂ (at 20 µM; p = 0.0183) compared with the control. (PhSe)₂ inhibited biofilm formation and decreased biofilm viability in both early and mature biofilms more efficiently than (pCl-PhSe)₂. Overall, the organochalcogen compounds, especially (PhSe)₂, were demonstrated to be effective antifungal drugs against C. albicans virulence factors related to epithelial cell surface adhesion and the formation and viability of biofilms.

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.

Known Antimicrobials Versus Nortriptyline in Candida albicans: Repositioning an Old Drug for New Targets

Candida albicans has the capacity to develop resistance to commonly used antimicrobials, and to solve this problem, drug repositioning and new drug combinations are being studied. Nortriptyline, a tricyclic antidepressant, was shown to have the capacity to inhibit biofilm and hyphae formation, along with the ability to efficiently kill cells in a mature biofilm. To use nortriptyline as a new antimicrobial, or in combination with known drugs to increase their actions, it is important to characterize in more detail the effects of this drug on the target species. In this study, the Candida albicans GRACE™ collection and a Haplo insufficiency profiling were employed to identify the potential targets of nortriptyline, and to classify, in a parallel screening with amphotericin B, caspofungin, and fluconazole, general multi-drug resistance genes. The results identified mutants that, during biofilm formation and upon treatment of a mature biofilm, are sensitive or tolerant to nortriptyline, or to general drug treatments. Gene ontology analysis recognized the categories of ribosome biogenesis and spliceosome as enriched upon treatment with the tricyclic antidepressant, while mutants in oxidative stress response and general stress response were commonly retrieved upon treatment with any other drug. The data presented suggest that nortriptyline can be considered a “new” antimicrobial drug with large potential for application to in vivo infection models.

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.

Synergistic Effects and Mechanisms of Combined Treatment With Harmine Hydrochloride and Azoles for Resistant Candida albicans

Several studies have demonstrated the significant antiviral, antimicrobial, antiplasmodial, antioxidative, antifungal, antimutagenic, and antitumor properties of harmine hydrochloride (HMH). The main objective of the present study was to investigate the antifungal effects and underlying mechanisms of HMH when combined with azoles to determine whether such combinations act in a synergistic manner. As a result, we found that HMH exhibits synergistic antifungal effects in combination with azoles against resistant Candida albicans (C. albicans) planktonic cells, as well as resistant C. albicans biofilm in the early stage. Antifungal potential of HMH with fluconazole was also explored in vivo using an invertebrate model. Our results suggest that HMH combined with azoles is synergistic against resistant C. albicans in vitro and in vivo. No synergy is seen with azole sensitive C. albicans strains nor with other Candida species. Such synergistic mechanisms on resistance C. albicans are involved in increasing intracellular azoles, inhibiting hyphal growth, disturbing cytosolic calcium concentration, and inducing apoptosis of resistant C. albicans cells.

The effect of isoflavaspidic acid PB extracted from Dryopteris fragrans (L.) Schott on planktonic and biofilm growth of dermatophytes and the possible mechanism of antibiofilm

ETHNOPHARMACOLOGICAL RELEVANCE

Dryopteris fragrans (L.) Schott (D. fragrans), a deciduous perennial herb, has been traditionally used for treatment of various skin diseases in Heilongjiang province of China for many years. Phloroglucinol derivatives extracted from D. fragrans were the most effective fraction against dermatophytes. Isoflavaspidic acid PB is a typically phloroglucinol derivative which extracted from D. fragrans and has been reported to exert anti-fungal activities against several dermatophytes.

AIM OF THE STUDY

This study aimed to evaluate anti-fungal and anti-biofilm activity of isoflavaspidic acid PB on planktonic and biofilm growth of dermatophytes and explore possible mechanisms of anti-biofilm.

MATERIALS AND METHODS

Minimal inhibitory concentrations (MIC) and minimal fungicidal concentrations (MFC) of isoflavaspidic acid PB against 25 isolates of dermatophytes were determined by the Clinical and Laboratory Standards Institute (CLSI) M38-A2 method. The effects of isoflavaspidic acid PB on dermatophytes biofilm formation and pre-formed biofilm were assessed by 2.3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[carbonyl (phenylamino)]-2H-tetrazolium hydroxide (XTT) assay. Morphology of mature biofilm were observed by Scanning Electron Microscope (SEM). Biomass, exopolysaccharide and ergosterol content of mature biofilm were analyzed by gravimetric analysis, anthranone sulfuric acid method and Ultra Performance Liquid Chromatography (UPLC) assay respectively.

RESULT

The MIC and MFC ranges of isoflavaspidic acid PB against 25 isolates of dermatophytes were 20-80 μg/mL and 40-80 μg/mL respectively. Isoflavaspidic acid PB (2 MIC) inhibited not only Trichophyton biofilm formation (54.8% ∼ 81.2%) but also the metabolic activity of mature biofilm (20.7% ∼ 44.2%). The result of SEM showed that isoflavaspidic acid PB (8 MIC) could destroy the morphology of hyphae seriously. Comparing with control group, biomass, exopolysaccharide and ergosterol content of the mature biofilm under isoflavaspidic acid PB (8 MIC) were significantly decreased (P < 0.01).

CONCLUSION

Isoflavaspidic acid PB had anti-fungal and fungicidal activities against dermatophytes. Isoflavaspidic acid PB could inhibit the biofilm of Trichophyton. The mechanism might be related to the decline of the biofilm biomass, exopolysaccharide and ergosterol content. These results showed that isoflavaspidic acid PB could be explored for promising anti-biofilm drugs.

Biofilms and vulvovaginal candidiasis

Candida species, including C. albicans, are part of the mucosal flora of most healthy women, and inhabit the gastrointestinal and genitourinary tracts. Under favourable conditions, they can colonize the vulvovaginal mucosa, giving rise to symptomatic vulvovaginal candidiasis (VVC). The mechanism by which Candida spp. produces inflammation is unknown. Both, the blastoconidia and the pseudohyphae are capable of destroying the vaginal epithelium by direct invasion. Although the symptoms are not always related to the fungal burden, in general, VVC is associated with a greater number of yeasts and pseudohyphae. Some years ago, C. albicans was the species most frequently involved in the different forms of VVC. However, infections by different species have emerged during the last two decades producing an increase in causative species of VVC such as C. glabrata, C. parapsilosis, C. krusei and C. tropicalis. Candida species are pathogenic organisms that have two forms of development: planktonic and biofilm. A biofilm is defined as a community of microorganisms attached to a surface and encompassed by an extracellular matrix. This form of presentation gives microorganisms greater resistance to antifungal agents. This review, about Candia spp. with a special emphasis on Candida albicans discusses specific areas such as biofilm structure and development, cell morphology and biofilm formation, biofilm-associated gene expression, the cell surface and adherence, the extracellular matrix, biofilm metabolism, and biofilm drug resistance in vulvovaginitis biofilms as an important virulence factor in fungi.

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.

Discovery of Janus Kinase 2 (JAK2) and Histone Deacetylase (HDAC) Dual Inhibitors as a Novel Strategy for the Combinational Treatment of Leukemia and Invasive Fungal Infections

Clinically, leukemia patients often suffer from the limited efficacy of chemotherapy and high risks of infection by invasive fungal pathogens. Herein, a novel therapeutic strategy was developed in which a small molecule can simultaneously treat leukemia and invasive fungal infections (IFIs). Novel Janus kinase 2 (JAK2) and histone deacetylase (HDAC) dual inhibitors were identified to possess potent anti-proliferative activity toward hematological cell lines and excellent synergistic effects with fluconazole to treat resistant Candida albicans infections. In particular, compound 20a, a highly active and selective JAK2/HDAC6 dual inhibitor, showed excellent in vivo antitumor efficacy in several acute myeloid leukemia (AML) models and synergized with fluconazole for the treatment of resistant C. albicans infections. This study highlights the therapeutic potential of JAK2/HDAC dual inhibitors in treating AML and IFIs and provides an efficient strategy for multitargeting drug discovery.

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.

Effects of patchouli and cinnamon essential oils on biofilm and hyphae formation by Candida species

The prevalence and fatality rates with biofilm-associated candidal infections have remained a challenge to the medical fraternity despite major advances in the field of antifungal therapy. Traditionally, essential oils (EOs) from the aromatic plants have been found to be excellent therapeutic agents to treat fungal ailments. The present study explores the antivirulent and antibiofilm effects of under explored leaf EOs of Indian patchouli EO extracted from Pogostemon heyneanus (PH), Indian cassia from Cinnamomum tamala (CT) and camphor EO from C. camphora (CC) against Candida species. The EOs were investigated for its efficacy to disrupt the young and preformed Candida spp. biofilms and to inhibit the yeast to hyphal transition, a hallmark virulent trait of C. albicans. The ability of these EOs to inhibit metabolically active cells was assessed through XTT assay. Of these three EOs, CT EO showed enhanced biofilm inhibition than others and hence it was further selected to study its biomass inhibition potential and exopolysaccharide layer disruption ability. The CT EO reduced the biomass of the preformed biofilms of all three Candida strains, which was supported by confocal microscopy. It also disrupted the exopolysaccharide layer of the Candida strains as shown by scanning electron microscopy. The present findings validate the effectiveness of EOs against the virulence of Candida spp. and emphasize the pharmaceutical potential of several native but yet unexplored wild aromatic plants in the prospect of therapeutic application.

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.

Synthesis of novel proxyphylline derivatives with dual Anti-Candida albicans and anticancer activity

Three out of 16 newly synthesized 1,3-dimethylxanthine derivatives (proxyphylline analogues) exhibited consistencies between antifungal and anticancer properties. Proxyphylline possessing 1-(10H-phenothiazin-10-yl)propan-2-yl (6) and polybrominated benzimidazole (41) or benzotriazole moiety (42) remained selectively cidal against Candida albicans (lg R ≥ 3 at conc. of 31, 36 and 20 μM, respectively) however not against normal mammalian Vero cell line in vitro (IC₅₀ ≥ 280 μM) and Galleria mellonella in vivo. These compounds also displayed moderate antineoplastic activity against human breast adenocarcinoma (MCF-7) cell line (EC₅₀ = 80 μM) and high against peripheral blood T lymphoblast (CCRF-CEM) (EC₅₀ = 6.3-6.5 μM). In addition, 6 and 42 exerted: (1) dual activity against fungal adhesion and damage mature biofilm; (2) necrosis of planktonic cells due to loss of membrane function and of structural integrity; (3) biochemical (inhibition of sessile cell respiration) and morphological changes in cell wall polysaccharide contents. Therefore, leading proxyphylline derivatives can be employed to prevent cancer-associated biofilm Candida infections.

Biofilm Formation and Resistance to Fungicides in Clinically Relevant Members of the Fungal Genus Fusarium

Clinically relevant members of the fungal genus, Fusarium, exhibit an extraordinary genetic diversity and cause a wide spectrum of infections in both healthy individuals and immunocompromised patients. Generally, Fusarium species are intrinsically resistant to all systemic antifungals. We investigated whether the presence or absence of the ability to produce biofilms across and within Fusarium species complexes is linked to higher resistance against antifungals. A collection of 41 Fusarium strains, obtained from 38 patients with superficial and systemic infections, and three infected crops, were tested, including 25 species within the Fusarium fujikuroi species complex, 14 from the Fusarium solani species complex (FSSC), one Fusarium dimerum species complex, and one Fusarium oxysporum species complex isolate. Of all isolates tested, only seven strains from two species of FSSC, five F. petroliphilum and two F. keratoplasticum strains, recovered from blood, nail scrapings, and nasal biopsy samples, could produce biofilms under the tested conditions. In the liquid culture tested, sessile biofilm-forming Fusarium strains exhibited elevated minimum inhibitory concentrations (MICs) for amphotericin B, voriconazole, and posaconazole, compared to their planktonic counterparts, indicating that the ability to form biofilm may significantly increase resistance. Collectively, this suggests that once a surface adherent biofilm has been established, therapies designed to kill planktonic cells of Fusarium are ineffective.

Photodynamic Antimicrobial Chemotherapy (PACT), using Toluidine blue O inhibits the viability of biofilm produced by Candida albicans at different stages of development

BACKGROUND

Candida albicans is an opportunistic fungus producing both superficial and systemic infections, especially in immunocompromised individuals. It has been demonstrated that C. albicans ability to form biofilms is a crucial process for colonization and virulence. Furthermore, a correlation between the development of drug resistance and biofilm maturation at Candida biofilms has been shown. Photodynamic Antimicrobial Chemotherapy (PACT) is a potential antimicrobial therapy that combines visible light and a non-toxic dye, known as a photosensitizer, producing reactive oxygen species (ROS) that can kill the treated cells. The objective of this study was to investigate the effects of PACT, using Toluidine Blue O (TBO) on the viability of biofilms produced by C. albicans at different stages of development.

METHODS

In this study, the effects of PACT on both biofilm formation and viability of the biofilm produced by C. albicans were studied. Biofilm formation and viability were determined by a metabolic assay based on the reduction of XTT assay. In addition, the morphology of the biofilm was observed using light microscopy.

RESULTS

PACT inhibited both biofilm formation and viability of the biofilm produced by C. albicans. Furthermore, PACT was able to decrease the number of both cells and filamentous form present in the biofilm structure. This inhibitory effect was observed in both early and mature biofilms.

CONCLUSIONS

The results obtained in this study demonstrated the potential of PACT (using TBO) as an effective antifungal therapy, including against infections associated with biofilms at different stages of development.

Increasing the Fungicidal Action of Amphotericin B by Inhibiting the Nitric Oxide-Dependent Tolerance Pathway

Amphotericin B (AmB) induces oxidative and nitrosative stresses, characterized by production of reactive oxygen and nitrogen species, in fungi. Yet, how these toxic species contribute to AmB-induced fungal cell death is unclear. We investigated the role of superoxide and nitric oxide radicals in AmB's fungicidal activity in Saccharomyces cerevisiae, using a digital microfluidic platform, which enabled monitoring individual cells at a spatiotemporal resolution, and plating assays. The nitric oxide synthase inhibitor L-NAME was used to interfere with nitric oxide radical production. L-NAME increased and accelerated AmB-induced accumulation of superoxide radicals, membrane permeabilization, and loss of proliferative capacity in S. cerevisiae. In contrast, the nitric oxide donor S-nitrosoglutathione inhibited AmB's action. Hence, superoxide radicals were important for AmB's fungicidal action, whereas nitric oxide radicals mediated tolerance towards AmB. Finally, also the human pathogens Candida albicans and Candida glabrata were more susceptible to AmB in the presence of L-NAME, pointing to the potential of AmB-L-NAME combination therapy to treat fungal infections.

Biofilm Formation by Pseudallescheria/Scedosporium Species: A Comparative Study

Pseudallescheria/Scedosporium species are medically important fungi that are present in soil and human impacted areas and capable of causing a wide spectrum of diseases in humans. Although little is known about their pathogenesis, their growth process and infection routes are very similar to those of Aspergillus species, which grow as biofilms in invasive infections. All nine strains tested here displayed the ability to grow as biofilms in vitro and to produce a dense network of interconnected hyphae on both polystyrene and the surfaces of central venous catheters, but with different characteristics. Scedosporium boydii and S. aurantiacum clinical isolates were able to form biofilms faster than the corresponding environmental strains, as evidenced in kinetic assays for S. boydii and CLSM for S. aurantiacum. Biofilms formed by Pseudallescheria/Scedosporium species had significantly higher resistance to the class of antifungal azole than was observed in planktonic cells, indicating a protective role for this structure. In addition, the clinical S. aurantiacum isolate that formed the most robust biofilms was also more virulent in a larvae Galleria mellonella infection model, suggesting that the ability to form biofilms enhances virulence in Pseudallescheria/Scedosporium species.

Activity of Sanguinarine against Candida albicans Biofilms

Candida albicans biofilms show resistance to many clinical antifungal agents and play a considerable contributing role in the process of C. albicans infections. New antifungal agents against C. albicans biofilms are sorely needed. The aim of this study was to evaluate sanguinarine (SAN) for its activity against Candida albicans biofilms and explore the underlying mechanism. The MIC₅₀ of SAN was 3.2 μg/ml, while ≥0.8 μg/ml of SAN could suppress C. albicans biofilms. Further study revealed that ≥0.8 μg/ml of SAN could decrease cellular surface hydrophobicity (CSH) and inhibited hypha formation. Real-time reverse transcription-PCR (RT-PCR) results indicated that the exposure of C. albicans to SAN suppressed the expression of some adhesion- and hypha-specific/essential genes related to the cyclic AMP (cAMP) pathway, including ALS3, HWP1, ECE1, HGC1, and CYR1 Consistently, the endogenous cAMP level of C. albicans was downregulated after SAN treatment, and the addition of cAMP rescued the SAN-induced filamentation defect. In addition, SAN showed relatively low toxicity to human umbilical vein endothelial cells, the 50% inhibitory concentration (IC₅₀) being 7.8 μg/ml. Collectively, the results show that SAN exhibits strong activity against C. albicans biofilms, and the activity was associated with its inhibitory effect on adhesion and hypha formation due to cAMP pathway suppression.

Tackling Fungal Resistance by Biofilm Inhibitors

The high incidence and mortality of invasive fungal infections and serious drug resistance have become a global public health issue. The ability of fungal cells to form biofilms is an important reason for the emergence of severe resistance to most clinically available antifungal agents. Targeting fungal biofilm formation by small molecules represents a promising new strategy for the development of novel antifungal agents. This perspective will provide a comprehensive review of fungal biofilm inhibitors. In particular, discovery strategies, chemical structures, antibiofilm/antifungal activities, and structure-activity relationship studies will be discussed. Development of inhibitors to treat biofilm-related resistant fungal infections is a new yet clinically unexploited paradigm, and there is still a long way to go to clinical application. Better understanding of fungal biofilms in combination with systematic drug discovery efforts will pave the way for potential clinical applications.

Sensitivity of Candida albicans to essential oils: are they an alternative to antifungal agents?

AIMS

Candida albicans is an important opportunistic pathogen, responsible for the majority of yeast infections in humans. Essential oils, extracted from aromatic plants, are well-known antimicrobial agents, characterized by a broad spectrum of activities, including antifungal properties. The aim of this work was to assess the sensitivity of 30 different vaginal isolated strains of C. albicans to 12 essential oils, compared to the three main used drugs (clotrimazole, fluconazole and itraconazole).

METHODS AND RESULTS

Thirty strains of C. albicans were isolated from vaginal swab on CHROMagar^™ Candida. The agar disc diffusion method was employed to determine the sensitivity to the essential oils. The antifungal activity of the essential oils and antifungal drugs (clotrimazole, itraconazole and fluconazole) were investigated using a microdilution method. Transmission and scanning electron microscopy analyses were performed to get a deep inside on cellular damages. Mint, basil, lavender, tea tree oil, winter savory and oregano essential oils inhibited both the growth and the activity of C. albicans more efficiently than clotrimazole. Damages induced by essential oils at the cellular level were stronger than those caused by clotrimazole.

CONCLUSIONS

Candida albicans is more sensitive to different essential oils compared to the main used drugs. Moreover, the essential oil affected mainly the cell wall and the membranes of the yeast.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of this work support the research for new alternatives or complementary therapies against vaginal candidiasis.

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

Candida spp. can adhere to and form biofilms over different surfaces, becoming less susceptible to antifungal treatment. Resistance of biofilms to antifungal agents is multifactorial and the extracellular matrix (ECM) appears to play an important role. Among the few available antifungals for treatment of candidaemia, only the lipid formulations of amphotericin B (AmB) and the echinocandins are effective against biofilms. Our group has previously demonstrated that miltefosine has an important effect against Candida albicans biofilms. Thus, the aim of this work was to expand the analyses of the in vitro antibiofilm activity of miltefosine to non-albicans Candida spp. Miltefosine had significant antifungal activity against planktonic cells and the development of biofilms of C. albicans, Candida parapsilosis, Candida tropicalis and Candida glabrata. The activity profile in biofilms was superior to fluconazole and was similar to that of AmB and caspofungin. Biofilm-derived cells with their ECM extracted became as susceptible to miltefosine as planktonic cells, confirming the importance of the ECM in the biofilm resistant behaviour. Miltefosine also inhibited biofilm dispersion of cells at the same concentration needed to inhibit planktonic cell growth. The data obtained in this work reinforce the potent inhibitory activity of miltefosine on biofilms of the four most pathogenic Candida spp. and encourage further studies for the utilisation of this drug and/or structural analogues on biofilm-related infections.

Functional characterization of the Aspergillus nidulans glucosylceramide pathway reveals that LCB Δ8-desaturation and C9-methylation are relevant to filamentous growth, lipid raft localization and Psd1 defensin activity

C8-desaturated and C9-methylated glucosylceramide (GlcCer) is a fungal-specific sphingolipid that plays an important role in the growth and virulence of many species. In this work, we investigated the contribution of Aspergillus nidulans sphingolipid Δ8-desaturase (SdeA), sphingolipid C9-methyltransferases (SmtA/SmtB) and glucosylceramide synthase (GcsA) to fungal phenotypes, sensitivity to Psd1 defensin and Galleria mellonella virulence. We showed that ΔsdeA accumulated C8-saturated and unmethylated GlcCer, while gcsA deletion impaired GlcCer synthesis. Although increased levels of unmethylated GlcCer were observed in smtA and smtB mutants, ΔsmtA and wild-type cells showed a similar 9,Me-GlcCer content, reduced by 50% in the smtB disruptant. The compromised 9,Me-GlcCer production in the ΔsmtB strain was not accompanied by reduced filamentation or defects in cell polarity. When combined with the smtA deletion, smtB repression significantly increased unmethylated GlcCer levels and compromised filamentous growth. Furthermore, sdeA and gcsA mutants displayed growth defects and raft mislocalization, which were accompanied by reduced neutral lipids levels and attenuated G. mellonella virulence in the ΔgcsA strain. Finally, ΔsdeA and ΔgcsA showed increased resistance to Psd1, suggesting that GlcCer synthesis and fungal sphingoid base structure specificities are relevant not only to differentiation but also to proper recognition by this antifungal defensin.

Terpinen-4-ol, tyrosol, and β-lapachone as potential antifungals against dimorphic fungi

This study aimed to evaluate the in vitro antifungal activity of terpinen-4-ol, tyrosol, and β-lapachone against strains of Coccidioides posadasii in filamentous phase (n=22) and Histoplasma capsulatum in both filamentous (n=40) and yeast phases (n=13), using the broth dilution methods as described by the Clinical and Laboratory Standards Institute, to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of these compounds. The mechanisms of action of these compounds were also investigated by analyzing their effect on cell membrane permeability and ergosterol synthesis. The MIC and MFCf these compounds against C. posadasii, mycelial H. capsulatum, and yeast-like H. capsulatum, were in the following ranges: 350-5720μg/mL, 20-2860μg/mL, and 40-1420μg/mL, respectively for terpinen-4-ol; 250-4000μg/mL, 30-2000μg/mL, and 10-1000μg/mL, respectively, for tyrosol; and 0.48-7.8μg/mL, 0.25-16μg/mL, and 0.125-4μg/mL, respectively for β-lapachone. These compounds showed a decrease in MIC when the samples were subjected to osmotic stress, suggesting that the compounds acted on the fungal membrane. All the compounds were able to reduce the ergosterol content of the fungal strains. Finally, tyrosol was able to cause a leakage of intracellular molecules.

Adamantylidene-substituted alkylphosphocholine TCAN26 is more active against Sporothrix schenckii than miltefosine

Sporotrichosis is the most frequent subcutaneous mycosis in the world and its increasing incidence has led to the search for new therapeutic options for its treatment. In this study, we demonstrated that three structural analogues of miltefosine (TCAN26, TC19, and TC70) showed inhibitory activity against Sporothrix schenckii sensu stricto and that TCAN26 was more active in vitro than miltefosine against several isolates. Scanning electron microscopy showed that S. schenckii exposure to TCAN26 resulted in cells that were slightly more elongated than untreated cells. Transmission electron microscopy showed that TCAN26 treatment induced loss of the regular cytoplasmic electron-density and altered the cell envelope (disruption of the cell membrane and cell wall, and increased cell wall thickness). Additionally, TCAN26 concentrations required to kill S. schenckii cells were lower than concentrations that were cytotoxic in mammalian cells, and TCAN26 was more selective than miltefosine. Thus, the adamantylidene-substituted alkylphosphocholine TCAN26 is a promising molecule for the development of novel antifungal compounds, although further investigations are required to elucidate the mode of action of TCAN26 in S. schenckii cells.

Novel strategies against Candida biofilms: interest of synthetic compounds

A biofilm is a consortium of microbial cells that are attached to a substratum or an interface. It should be considered a reservoir that may induce serious infections. Indeed, Candidaspp. biofilms may be involved in the persistence or worsening of some chronic inflammatory diseases as well as in systemic infections, which may lead to high morbidity and mortality rates. New strategies are currently being explored, utilizing several synthetic compounds to prevent or fight these Candida biofilms. This article focuses on active synthetic compounds classified with regards to their modes of action: inhibition of early adherence phase, inhibition or control of biofilm maturation and finally elimination of already formed biofilms. Some of them show promise in fighting biofilm.

In Vitro Activity of Miltefosine against Candida albicans under Planktonic and Biofilm Growth Conditions and In Vivo Efficacy in a Murine Model of Oral Candidiasis

The generation of a new antifungal against Candida albicans biofilms has become a major priority, since biofilm formation by this opportunistic pathogenic fungus is usually associated with an increased resistance to azole antifungal drugs and treatment failures. Miltefosine is an alkyl phospholipid with promising antifungal activity. Here, we report that, when tested under planktonic conditions, miltefosine displays potent in vitro activity against multiple fluconazole-susceptible and -resistant C. albicans clinical isolates, including isolates overexpressing efflux pumps and/or with well-characterized Erg11 mutations. Moreover, miltefosine inhibits C. albicans biofilm formation and displays activity against preformed biofilms. Serial passage experiments confirmed that miltefosine has a reduced potential to elicit resistance, and screening of a library of C. albicans transcription factor mutants provided additional insight into the activity of miltefosine against C. albicans growing under planktonic and biofilm conditions. Finally, we demonstrate the in vivo efficacy of topical treatment with miltefosine in the murine model of oropharyngeal candidiasis. Overall, our results confirm the potential of miltefosine as a promising antifungal drug candidate, in particular for the treatment of azole-resistant and biofilm-associated superficial candidiasis.

Trichosporon inkin biofilms produce extracellular proteases and exhibit resistance to antifungals

The aim of this study was to determine experimental conditions for in vitro biofilm formation of clinical isolates of Trichosporon inkin, an important opportunistic pathogen in immunocompromised patients. Biofilms were formed in microtitre plates in three different media (RPMI, Sabouraud and CLED), with inocula of 104, 105 or 106 cells ml- 1, at pH 5.5 and 7.0, and at 35 and 28 °C, under static and shaking conditions for 72 h. Growth kinetics of biofilms were evaluated at 6, 24, 48 and 72 h. Biofilm milieu analysis were assessed by counting viable cells and quantification of nucleic acids released into biofilm supernatants. Biofilms were also analysed for proteolytic activity and antifungal resistance against amphotericin B, caspofungin, fluconazole, itraconazole and voriconazole. Finally, ultrastructural characterization of biofilms formed in microtitre plates and catheter disks was performed by scanning electron microscopy. Greater biofilm formation was observed with a starter inoculum of 106 cells ml- 1, at pH 7.0 at 35 °C and 80 r.p.m., in both RPMI and Sabouraud media. Growth kinetics showed an increase in both viable cells and biomass with increasing incubation time, with maximum production at 48 h. Biofilms were able to disperse viable cells and nucleic acids into the supernatant throughout the developmental cycle. T. inkin biofilms produced more protease than planktonic cells and showed high tolerance to amphotericin B, caspofungin and azole derivatives. Mature biofilms were formed by different morphotypes, such as blastoconidia, arthroconidia and hyphae, in a strain-specific manner. The present article details the multicellular lifestyle of T. inkin and provides perspectives for further research.

In vitro antifungal activity of miltefosine and levamisole: their impact on ergosterol biosynthesis and cell permeability of dimorphic fungi

AIMS

This study aimed to evaluate the in vitro activity of miltefosine and levamisole against strains of Coccidioides posadasii in the filamentous phase and strains of Histoplasma capsulatum in filamentous and yeast phases.

METHODS AND RESULTS

Strains of C. posadasii in the filamentous phase (n = 22) and strains of H. capsulatum in filamentous (n = 40) and yeast phases (n = 13) were, respectively, submitted to broth macrodilution and broth microdilution methods, as described by the Clinical and Laboratory Standards Institute, to determine the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) of miltefosine and levamisole. The effect of the drugs on cell membrane permeability under osmotic stress conditions and total ergosterol production were also assessed, along with quantification of extravasated molecules. The results show the inhibitory effect of levamisole and miltefosine against C. posadasii and H. capsulatum and the effect of these drugs on ergosterol synthesis and the permeability of the plasma membrane using subinhibitory concentrations against strains subjected to osmotic stress. Levamisole was also able to cause the release of nucleic acids.

CONCLUSIONS

Miltefosine and levamisole are capable of inhibiting the in vitro growth of C. posadasii and H. capsulatum, probably by altering the permeability of the cellular membrane.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work presents alternatives for the treatment of histoplasmosis and coccidioidomycosis, raising the possibility of the use of miltefosine and levamisole as adjuvants in antifungal therapy, providing perspectives for the design of in vivo studies.

Proanthocyanidins polymeric tannin from Stryphnodendron adstringens are active against Candida albicans biofilms

Background

Biofilm formation is important in Candida albicans pathogenesis and constitutes a mechanism of antifungal resistance. Thus, we evaluated the effect of proanthocyanidins polymer-rich fractions from Stryphnodendron adstringens (fraction F2 and subfraction F2.4) against C. albicans biofilms.

Methods

Firstly, the antifungal activity of F2 and F2.4 against planktonic cells of Candida albicans (ATCC 10231) was determined using broth microdilution method. Anti-biofilm effect of F2 and F2.4 was evaluated during biofilm formation or on mature biofilm of C. albicans and compared with standard antifungals amphotericin B and fluconazole. Metabolic activity of sessile and dispersion cells from biofilms after antifungal treatments were measured using a tetrazolium reduction assay and the biofilm total biomass was quantified by crystal violet-based assay. Morphological alterations after treatments were observed using scanning electron microscopy.

Results

The anti-biofilm effect of F2 and F2.4 were comparable to standard antifungals (amphotericin B and fluconazole). F2 and F2.4 treatments reduced biofilm metabolic activity (in sessile and in dispersion cells) during biofilm formation, and in mature biofilms, unlike fluconazole, which only prevents the biofilm formation. Treatments with F2, F2.4 or fluconazole reduced biofilm biomass during biofilm formation, but not in mature biofilm. Amphotericin B presented higher inhibitory effect on biofilm formation and on mature biofilm of C. albicans. F2 and F2.4 treatments led to the appearance of dumbbell-shaped blastoconidia and of blastoconidia clusters in biofilms.

Conclusion

Proanthocyanidins polymer-rich fractions from S. adstringens successfully inhibited C. albicans planktonic growth and biofilm development, and they represent a potential new agent for the treatment of biofilm-associated candidiasis.

Miltefosine is active against Sporothrix brasiliensis isolates with in vitro low susceptibility to amphotericin B or itraconazole

Sporotrichosis is a common mycosis caused by dimorphic fungi from the Sporothrix schenckii complex. In recent years, sporotrichosis incidence rates have increased in the Brazilian state of Rio de Janeiro, where Sporothrix brasiliensis is the species more frequently isolated from patients. The standard antifungals itraconazole and amphotericin B are recommended as first-line therapy for cutaneous/lymphocutaneous and disseminated sporotrichosis, respectively, although decreased sensitivity to these drugs in vitro was reported for clinical isolates of S. brasiliensis. Here, we evaluated the activity of the phospholipid analogue miltefosine - already in clinical use against leishmaniasis - towards the pathogenic yeast form of S. brasiliensis isolates with low sensitivity to itraconazole or amphotericin B in vitro. Miltefosine had fungicidal activity, with minimum inhibitory concentration (MIC) values of 1-2 µg ml(-1). Miltefosine exposure led to loss of plasma membrane integrity, and transmission electron microscopy (TEM) analysis revealed a decrease in cytoplasmic electron density, alterations in the thickness of cell wall layers and accumulation of an electron-dense material in the cell wall. Flow cytometry analysis using an anti-melanin antibody revealed an increase in cell wall melanin in yeasts treated with miltefosine, when compared with control cells. The cytotoxicity of miltefosine was comparable to those of amphotericin B, but miltefosine showed a higher selectivity index towards the fungus. Our results suggest that miltefosine could be an effective alternative for the treatment of S. brasiliensis sporotrichosis, when standard treatment fails. Nevertheless, in vivo studies are required to confirm the antifungal potential of miltefosine for the treatment of sporotrichosis.

The discovery of novel antifungal scaffolds by structural simplification of the natural product sampangine

Structural simplification of the natural product sampangine led to the discovery of two novel antifungal compounds with excellent activity and low toxicity.

Effect of 2, 4-di-tert-butylphenol on growth and biofilm formation by an opportunistic fungus Candida albicans

Candida albicans, an opportunistic pathogen, has been known to form hypoxic biofilms on medical devices which in turn confers resistance towards antifungals, resulting in subsequent therapeutic failures. Inclusion of anti-biofilm agents in the control of infections is a topic of current interest in developing potential anti-infectives. The in vitro anti-fungal and anti-biofilm efficacy of 2,4-di-tert-butyl phenol [DTBP] was evaluated in this study, which revealed the potential fungicidal action of DTBP at higher concentrations where fluconazole failed to act completely. DTBP also inhibited the production of hemolysins, phospholipases and secreted aspartyl proteinase which are the crucial virulence factors required for the invasion of C. albicans. Various anti-biofilm assays and morphological observations revealed the efficacy of DTBP in both inhibiting and disrupting biofilms of C. albicans. Inhibition of hyphal development, a key process that aids in initial adhesion of C. albicans, was observed, and this could be a mechanism for the anti-biofilm activity of DTBP.