Microplate alamarBlue assay for Paracoccidioides susceptibility testing

Peptides from Galleria mellonella against Cryptococcus spp: toxicity in three-dimensional cell cultures and G. mellonella

Aim: This work aimed to test peptides against the planktonic and biofilm form of Cryptococcus spp. and in vitro toxicity using three-dimensional (3D) cells characterized and evaluate in vivo toxicity in Galleria mellonella.Materials & methods: Susceptibility tests were conducted on the planktonic form and biofilm formation. The toxicity of the peptides was evaluated in lung and brain cells in monolayer (2D) and 3D mono- and co-culture, in addition to in vivo analysis with G. mellonella.Results: Susceptibility values ranged from 31.25 to over 250 µg/ml with a fungicidal profile. Regarding toxicity, the PepM2 peptide was not toxic in 3D culture (500 µg/ml). G. mellonella, showed a survival rate of more than 85% In assays with brain and lung cell lines, concentrations ranged from 4 × 104 to 4 × 103 cells/well for brain cells and 1 × 103 cells/well for lung cells. Cocultures used 1 × 105 brain and 1 × 103 lung cells.Conclusion: This study shows that the peptides have great potential against cryptococcosis, and all spheroids were characterized as having a spheroidal and compact structure.

Resazurin to determine the minimum inhibitory concentration on antifungal susceptibility assays for Fonsecaea sp. using a modified EUCAST protocol

Chromoblastomycosis is a fungal chronic disease, which affects humans, especially in cutaneous and subcutaneous tissues. There is no standard treatment for Chromoblastomycosis, and it is a therapeutic challenge, due natural resistance of their causative agents, inadequate response of patients and common cases of relapse. Protocols for determination of antifungal drugs susceptibility are not standardized for chromoblastomycosis agents and endpoint definition is usually based on visual inspection, which depends on the analyst, making it sometimes inaccurate. We presented a colorimetric and quantitative methodology based on resazurin reduction to resofurin to determine the metabolic status of viable cells of Fonsecaea sp. Performing antifungal susceptibility assay by a modified EUCAST protocol allied to resazurin, we validated the method to identify the minimum inhibitory concentrations of itraconazole, fluconazole, amphotericin B, and terbinafine for eight Fonsecaea clinical isolates. According to our data, resazurin is a good indicator of metabolic status of viable cells, including those exposed to antifungal drugs. This work aimed to test resazurin as an indicator of the metabolic activity of Fonsecaea species in susceptibility assays to antifungal drugs. Species of this genus are the main causative agents of Chromoblastomycosis, which affects humans.

In vitro activity of the anthelmintic drug niclosamide against Sporothrix spp. strains with distinct genetic and antifungal susceptibility backgrounds

The drugs available to treat sporotrichosis, an important yet neglected fungal infection, are limited. Some Sporothrix spp. strains present reduced susceptibility to these antifungals. Furthermore, some patients may not be indicated to use these drugs, while others may not respond to the therapy. The anthelmintic drug niclosamide is fungicidal against the Sporothrix brasiliensis type strain. This study aimed to evaluate whether niclosamide also has antifungal activity against Sporothrix globosa, Sporothrix schenckii and other S. brasiliensis strains with distinct genotypes and antifungal susceptibility status. Minimal inhibitory and fungicidal concentrations (MIC and MFC, respectively) were determined using the microdilution method according to the CLSI protocol. The checkerboard method was employed to evaluate niclosamide synergism with drugs used in sporotrichosis treatment. Metabolic activity of the strains under niclosamide treatment was evaluated using the resazurin dye. Niclosamide was active against all S. brasiliensis strains (n = 17), but it was ineffective (MIC > 20 µM) for some strains (n = 4) of other pathogenic Sporothrix species. Niclosamide MIC values for Sporothrix spp. were similar for mycelial and yeast-like forms of the strains (P = 0.6604). Niclosamide was fungicidal (MFC/MIC ratio ≤ 2) for most strains studied (89%). Niclosamide activity against S. brasiliensis is independent of the fungal genotype or non-wild-type phenotypes for amphotericin B, itraconazole, or terbinafine. These antifungal drugs presented indifferent interactions with niclosamide. Niclosamide has demonstrated potential for repurposing as a treatment for sporotrichosis, particularly in S. brasiliensis cases, instigating in vivo studies to validate the in vitro findings.

Role of paracoccin on Paracoccidioides brasiliensis virulence and susceptibility to antifungal drugs in the Galleria mellonella larvae model

Paracoccin (PCN), a Paracoccidioides brasiliensis glycoprotein, has been reported to play roles in fungal biology and paracoccidioidomycosis pathogenesis. Lectin and chitinase domains account for the PCN's dual roles as an immunomodulatory agent and virulence factor. Soluble PCN injected in P. brasiliensis infected mice, by interacting with TLRs' N-glycans, drives the host immune response toward a protective Th1 axis. Otherwise, mice infection with yeasts overexpressing PCN (ov-PCN) revealed that PCN acts as a fungal virulence factor, thanks to its chitinase activity on the cell wall, resulting in resistance to phagocytes' fungicidal activity and development of severe paracoccidioidomycosis. Because antifungal drug administration follows the disease diagnosis, we studied the PCN effect on yeast resistance or susceptibility to antifungal agents. Using a paracoccidioidomycosis model developed in Galleria mellonella larvae, we confirmed the observation, in the murine host, that ov-PCN yeasts display maximum virulence compared to wild-type (wt-PCN) or PCN-silenced (kd-PCN) yeasts. PCN overexpression accounted for the highest susceptibility of P. brasiliensis to antifungal and reduced relative mRNA expression of genes encoding proteins related to cell wall remodeling. The lowest virulence, detected in infection with kd-PCN yeasts, correlated with the lowest susceptibility to antifungals and impact on genes for cell wall remodeling. So, we defined that the grade of endogenous PCN production influences the P. brasiliensis virulence and susceptibility to antifungal drugs, as well as the expression of genes related to cell wall remodeling. We postulate that this variable gene expression is mechanistically associated with P. brasiliensis virulence changes.

Polypeptides Targeting Paracoccidioides brasiliensis Drk1

Considering the toxicity of conventional therapeutic approaches and the importance of precise mechanistic targets, it is important to explore signaling pathways implicated in fungal pathobiology. Moreover, treatment of paracoccidioidomycosis, a systemic mycosis caused by a dimorphic fungus, requires prolonged therapeutic regimens. Among the numerous factors underpinning the establishment of Paracoccidioides spp. infection, the capacity to transition from the mycelial to the yeast form is of pivotal importance. The Drk1 protein of Paracoccidioides brasiliensis likely plays a decisive role in this morphological shift and subsequent virulence. We identified peptides with affinity for the PbDrk1 protein using the phage-display method and assessed the effects of these peptides on P. brasiliensis. The peptides were found to inhibit the phase transition of P. brasiliensis. Furthermore, a substantial proportion of these peptides prevented adhesion to pneumocytes. Although these peptides may not possess inherent antifungal properties, they can augment the effects of certain antifungal agents. Notably, the cell wall architecture of P. brasiliensis appears to be modulated by peptide intervention, resulting in a reduced abundance of glycosylated proteins and lipids. These peptides were also evaluated for their efficacy in a Galleria mellonella model and shown to contribute to enhanced larval survival rates. The role of PbDrk1, which is notably absent in mammals, should be further investigated to improve the understanding of its functional role in P. brasiliensis, which may be helpful for designing novel therapeutic modalities.

Distribution and antifungal susceptibility profiles of Candida species isolated from people living with HIV/AIDS in a public hospital in Goiânia, GO, Brazil

Oropharyngeal candidiasis (OPC) is the most common opportunistic fungal infection of the oral cavity and is a significant clinical problem, particularly in immunocompromised individuals, such as people living with HIV/AIDS (PLWHA). Although Candida albicans is the most frequent pathogen, at least 30 species capable of causing infection have been described. Identifying the infecting organism is necessary because the species respond differently to therapy, and antifungal susceptibility testing is important to determine the appropriate treatment. This study aimed to determine the epidemiological, clinical, and mycological profiles of OPC in hospitalized PLWHA. Clinical samples were collected from 103 PLWHA with suspected candidiasis admitted to the Hospital Estadual of Doenças Tropicais/Hospital Anuar Auad of Goiania, Goias, Brazil, for 14 months. Candida species were identified using phenotypic microbiological techniques and molecular analysis performed by PCR using species-specific primers. The antifungal susceptibility pattern of the isolates against the six antifungal agents was determined using the broth microdilution method. Here, female individuals were the most affected by OPC, presenting a higher risk of oral colonization by Candida spp. The main clinical manifestation was pseudomembranous candidiasis. The number of cases of candidiasis was 87.3% (90/103), with C. albicans being the most common species, followed by C. tropicalis and C. glabrata. In the susceptibility pattern, non-albicans Candida showed higher resistance to than C. albicans. The fast and accurate identification of Candida spp. is very important to identify therapeutic agents for the treatment of oral candidiasis in PLWHA.

Evaluation of the Anti-Histoplasma capsulatum Activity of Indole and Nitrofuran Derivatives and Their Pharmacological Safety in Three-Dimensional Cell Cultures

Histoplasma capsulatum is a fungus that causes histoplasmosis. The increased evolution of microbial resistance and the adverse effects of current antifungals help new drugs to emerge. In this work, fifty-four nitrofurans and indoles were tested against the H. capsulatum EH-315 strain. Compounds with a minimum inhibitory concentration (MIC₉₀) equal to or lower than 7.81 µg/mL were selected to evaluate their MIC₉₀ on ATCC G217-B strain and their minimum fungicide concentration (MFC) on both strains. The quantification of membrane ergosterol, cell wall integrity, the production of reactive oxygen species, and the induction of death by necrosis–apoptosis was performed to investigate the mechanism of action of compounds 7, 11, and 32. These compounds could reduce the extracted sterol and induce necrotic cell death, similarly to itraconazole. Moreover, 7 and 11 damaged the cell wall, causing flaws in the contour (11), or changing the size and shape of the fungal cell wall (7). Furthermore, 7 and 32 induced reactive oxygen species (ROS) formation higher than 11 and control. Finally, the cytotoxicity was measured in two models of cell culture, i.e., monolayers (cells are flat) and a three-dimensional (3D) model, where they present a spheroidal conformation. Cytotoxicity assays in the 3D model showed a lower toxicity in the compounds than those performed on cell monolayers. Overall, these results suggest that derivatives of nitrofurans and indoles are promising compounds for the treatment of histoplasmosis.

Synthesis and Evaluation of the Antifungal and Toxicological Activity of Nitrofuran Derivatives

Fungal diseases affect more than 1 billion people worldwide. The constant global changes, the advent of new pandemics, and chronic diseases favor the diffusion of fungal pathogens such as Candida, Cryptococcus, Aspergillus, Trichophyton, Histoplasma capsulatum, and Paracoccidioides brasiliensis. In this work, a series of nitrofuran derivatives were synthesized and tested against different fungal species; most of them showed inhibitory activity, fungicide, and fungistatic profile. The minimal inhibitory concentration (MIC90) values for the most potent compounds range from 0.48 µg/mL against H. capsulatum (compound 11) and P. brasiliensis (compounds 3 and 9) to 0.98 µg/mL against Trichophyton rubrum and T. mentagrophytes (compounds 8, 9, 12, 13 and 8, 12, 13, respectively), and 3.9 µg/mL against Candida and Cryptococcus neoformans strains (compounds 1 and 5, respectively). In addition, all compounds showed low toxicity when tested in vitro on lung cell lines (A549 and MRC-5) and in vivo in Caenorhabditis elegans larvae. Many of them showed high selectivity index values. Thus, these studied nitrofuran derivatives proved to be potent against different fungal species, characterized by low toxicity and high selectivity; for these reasons, they may become promising compounds for the treatment of mycoses.

Antifungal activity and toxicity of an octyl gallate-loaded nanostructured lipid system on cells and nonmammalian animals

Aim: Octyl gallate (OG) loaded into a nanostructured lipid system (NLS) was tested for antifungal activity and in vitro and in vivo toxicity. Methods & Results: The features of NLS-OG were analyzed by dynamic light scattering and showed adequate size (132.1 nm) and homogeneity (polydispersity index = 0.200). OG was active against Paraccoccidioides spp., and NLS-OG did not affect antifungal activity. NLS-OG demonstrated reduced toxicity to lung cells and zebrafish embryos compared with OG, whereas NLS was toxic to hepatic cells. OG and NLS-OG did not show toxicity in a Galleria mellonella model at 20 mg/kg. All toxic concentrations were superior to MIC (antifungal activity). Conclusion: These results indicate good anti-Paracoccidioides activity and low toxicity of NLS-OG.

Evaluation of antimicrobial susceptibility testing of Nocardia spp. isolates by broth microdilution with resazurin and spectrophotometry

BACKGROUND

Nocardia species are ubiquitous in natural environments and can cause nocardiosis. In the present study, the use of Resazurin salt and Spectrophotometry were proposed as alternative methods to reduce subjectivity in the interpretation of susceptibility results to antimicrobials by the broth microdilution method for Nocardia spp.

RESULTS

The susceptibility of Nocardia spp. isolates to Amikacin, Ciprofloxacin, Minocycline and Trimethoprim-Sulfamethoxazole was evaluated by Minimum Inhibitory Concentration (MIC) determinations by the broth microdilution method. To verify cellular growth, the colour-changing dye Resazurin was applied, the Optical Densities were measured on a spectrophotometer, and both were compared to Clinical and Laboratory Standards Institute (CLSI) Gold Standard method (visual MIC determination). Percentages of essential and categorical agreements and interpretative categorical errors were calculated within each method (intra-reading) and between them (inter-reading). The Gold Standard visual reading demonstrated 100% of essential and categorical intra-reading agreements for Amikacin, and there was no error when compared with the alternative methods. For Ciprofloxacin, the comparison between the Gold Standard and the Spectrophotometric reading showed 91.5% of essential agreement. In the categorical intra-reading analysis for Minocycline, there were 88.1 and 91.7% in the Gold Standard and in the Spectrophotometric readings, respectively, and 86.4% of concordance between them. High rates of categorical agreement were also observed on the Trimethoprim-Sulfamethoxazole analyses, with 93.7% for the Gold Standard, 84.9% for the Resazurin readings, and 80.5% between them.

CONCLUSIONS

The alternative methods with Resazurin and Spectrophotometric readings showed high agreement rates with the Gold Standard.

Drk1, a Dimorphism Histidine Kinase, Contributes to Morphology, Virulence, and Stress Adaptation in Paracoccidioides brasiliensis

P. brasiliensis is a thermally dimorphic fungus belonging to Paracoccidioides complex, causative of a systemic, endemic mycosis limited to Latin American countries. Signal transduction pathways related to important aspects as surviving, proliferation according to the biological niches are linked to the fungal pathogenicity in many species, but its elucidation in P. brasiliensis remains poorly explored. As Drk1, a hybrid histidine kinase, plays regulators functions in other dimorphic fungi species, mainly in dimorphism and virulence, here we investigated its importance in P. brasilensis. We, therefore generated the respective recombinant protein, anti-PbDrk1 polyclonal antibody and a silenced strain. The Drk1 protein shows a random distribution including cell wall location that change its pattern during osmotic stress condition; moreover the P. brasiliensis treatment with anti-PbDrk1 antibody, which does not modify the fungus's viability, resulted in decreased virulence in G. mellonella model and reduced interaction with pneumocytes. Down-regulating PbDRK1 yielded phenotypic alterations such as yeast cells with more elongated morphology, virulence attenuation in G. mellonella infection model, lower amount of chitin content, increased resistance to osmotic and cell wall stresses, and also caspofungin, and finally increased sensitivity to itraconazole. These observations highlight the importance of PbDrk1 to P. brasiliensis virulence, stress adaptation, morphology, and cell wall organization, and therefore it an interesting target that could help develop new antifungals.

In vitro antifungal activity of pelgipeptins against human pathogenic fungi and Candida albicans biofilms

Systemic mycoses have become a major cause of morbidity and mortality, particularly among immunocompromised hosts and long-term hospitalized patients. Conventional antifungal agents are limited because of not only their costs and toxicity but also the rise of resistant strains. Lipopeptides from Paenibacillus species exhibit antimicrobial activity against a wide range of human and plant bacterial pathogens. However, the antifungal potential of these compounds against important human pathogens has not yet been fully evaluated, except for Candida albicans. Paenibacillus elgii produces a family of lipopeptides named pelgipeptins, which are synthesized by a non-ribosomal pathway, such as polymyxin. The present study aimed to evaluate the activity of pelgipeptins produced by P. elgii AC13 against Cryptococcus neoformans, Paracoccidioides brasiliensis, and Candida spp. Pelgipeptins were purified from P. elgii AC13 cultures and characterized by high-performance liquid chromatography (HPLC) and mass spectrometry (MALDI-TOF MS). The in vitro antifugal activity of pelgipeptins was evaluated against C. neoformans H99, P. brasiliensis PB18, C. albicans SC 5314, Candida glabrata ATCC 90030, and C. albicans biofilms. Furthermore, the minimal inhibitory concentration (MIC) was determined according to the CLSI microdilution method. Fluconazole and amphotericin B were also used as a positive control. Pelgipeptins A to D inhibited the formation and development of C. albicans biofilms and presented activity against all tested microorganisms. The minimum inhibitory concentration values ranged from 4 to 64 µg/mL, which are in the same range as fluconazole MICs. These results highlight the potential of pelgipeptins not only as antimicrobials against pathogenic fungi that cause systemic mycoses but also as coating agents to prevent biofilm formation on medical devices.

In Vitro and In Vivo Effect of Peptides Derived from 14-3-3 Paracoccidioides spp. Protein

Background: Paracoccidioidomycosis (PCM) is a chronic disease that causes sequelae and requires prolonged treatment; therefore, new therapeutic approaches are necessary. In view of this, three peptides from Paracoccidioides brasiliensis 14-3-3 protein were selected based on its immunogenicity and therapeutic potential. Methods: The in vitro antifungal activity and cytotoxicity of the 14-3-3 peptides were evaluated. The influence of the peptides in immunological and survival aspects was evaluated in vivo, using Galleria mellonella and the expression of antimicrobial peptide genes in Caenorhabditis elegans. Results: None of the peptides were toxic to HaCaT (skin keratinocyte), MRC-5 (lung fibroblast), and A549 (pneumocyte) cell lines, and only P1 exhibited antifungal activity against Paracoccidioides spp. The peptides could induce an immune response in G. mellonella. Moreover, the peptides caused a delay in the death of Paracoccidioides spp. infected larvae. Regarding C. elegans, the three peptides were able to increase the expression of the antimicrobial peptides. These peptides had essential effects on different aspects of Paracoccidioides spp. infection showing potential for a therapeutic vaccine. Future studies using mammalian methods are necessary to validate our findings.

Overview of Antifungal Drugs against Paracoccidioidomycosis: How Do We Start, Where Are We, and Where Are We Going?

Paracoccidioidomycosis is a neglected disease that causes economic and social impacts, mainly affecting people of certain social segments, such as rural workers. The limitations of antifungals, such as toxicity, drug interactions, restricted routes of administration, and the reduced bioavailability in target tissues, have become evident in clinical settings. These factors, added to the fact that Paracoccidioidomycosis (PCM) therapy is a long process, lasting from months to years, emphasize the need for the research and development of new molecules. Researchers have concentrated efforts on the identification of new compounds using numerous tools and targeting important proteins from Paracoccidioides, with the emphasis on enzymatic pathways absent in humans. This review aims to discuss the aspects related to the identification of compounds, methodologies, and perspectives when proposing new antifungal agents against PCM.

Antifungal Drug Repurposing

Control of fungal pathogens is increasingly problematic due to the limited number of effective drugs available for antifungal therapy. Conventional antifungal drugs could also trigger human cytotoxicity associated with the kidneys and liver, including the generation of reactive oxygen species. Moreover, increased incidences of fungal resistance to the classes of azoles, such as fluconazole, itraconazole, voriconazole, or posaconazole, or echinocandins, including caspofungin, anidulafungin, or micafungin, have been documented. Of note, certain azole fungicides such as propiconazole or tebuconazole that are applied to agricultural fields have the same mechanism of antifungal action as clinical azole drugs. Such long-term application of azole fungicides to crop fields provides environmental selection pressure for the emergence of pan-azole-resistant fungal strains such as Aspergillus fumigatus having TR34/L98H mutations, specifically, a 34 bp insertion into the cytochrome P450 51A (CYP51A) gene promoter region and a leucine-to-histidine substitution at codon 98 of CYP51A. Altogether, the emerging resistance of pathogens to currently available antifungal drugs and insufficiency in the discovery of new therapeutics engender the urgent need for the development of new antifungals and/or alternative therapies for effective control of fungal pathogens. We discuss the current needs for the discovery of new clinical antifungal drugs and the recent drug repurposing endeavors as alternative methods for fungal pathogen control.

Antifungal activity of liriodenine on agents of systemic mycoses, with emphasis on the genus Paracoccidioides

BACKGROUND

Endemic systemic mycoses remain a health challenge, since these opportunistic diseases are increasingly infecting immunosuppressed patients. The simultaneous use of antifungal compounds and other drugs to treat infectious or non-infectious diseases has led to several interactions and undesirable effects. Thus, new antifungal compounds should be investigated. The present study aimed to evaluate the activity of liriodenine extracted from Annona macroprophyllata on agents of systemic mycoses, with emphasis on the genus Paracoccidioides.

METHODS

The minimum inhibitory concentration (MIC) and minimum fungicide concentration (MFC) were determined by the microdilution method. The cellular alterations caused by liriodenine on a standard P. brasiliensis (Pb18) strain were evaluated by transmission and scanning electron microscopy.

RESULTS

Liriodenine was effective only in 3 of the 8 strains of the genus Paracoccidioides and in the Histoplasma capsulatum strain, in a very low concentration (MIC of 1.95 μg.mL-1); on yeasts of Candida spp. (MIC of 125 to 250 μg.mL-1), including C. krusei (250 μg.mL-1), which has intrinsic resistance to fluconazole; and in Cryptococcus neoformans and Cryptococcus gattii (MIC of 62.5 μg.mL-1). However, liriodenine was not effective against Aspergillus fumigatus at the studied concentrations. Liriodenine exhibited fungicidal activity against all standard strains and clinical isolates that showed to be susceptible by in vitro tests. Electron microscopy revealed cytoplasmic alterations and damage to the cell wall of P. brasiliensis (Pb18).

CONCLUSION

Our results indicate that liriodenine is a promising fungicidal compound that should undergo further investigation with some chemical modifications.

Voriconazole-natural latex dressings for treating infected Candida spp. skin ulcers

Aim: This work aimed to develop a membrane based on voriconazole (VCZ)-loaded natural rubber latex (NRL) for treating infected ulcers with Candida spp. and study their interaction, drug release, antifungal activity against Candida parapsilosis and biological characterization. Materials & methods: VCZ-loaded NRL membrane was produced by casting method. Results: Infrared spectrum showed that the incorporation of VCZ into the NRL membrane maintained its characteristics. Its mechanical properties were considered suitable for dermal application. The VCZ was able to release from NRL membrane, maintaining its antifungal activity against C. parapsilosis, besides did not present hemolytic effects. Conclusion: The VCZ-NRL membrane showed good results in mechanical, antifungal and biological assays, representing an interesting alternative to treatment of infected wound with Candida spp.

Antifungal activity of 2'-hydroxychalcone loaded in nanoemulsion against Paracoccidioides spp

Aim: This study aimed to evaluate the activity of 2'-hydroxychalcone-loaded in nanoemulsion (NLS + 2'chalc), the cytotoxic effect and toxicity against Paracoccidioides brasiliensis and Paracoccidioides lutzii using a zebrafish model. Materials & methods: Preparation and physical-chemical characterization of nanoemulsion (NLS) and NLS + 2'chalc were performed. MIC and minimum fungicide concentration, cytotoxicity and toxicity were also evaluated in the Danio rerio model. Results: NLS + 2'chalc showed fungicidal activity against Paracoccidioides spp. without cytotoxicity in MRC5 and HepG2 lines. It also had high selectivity index values and no toxicity in the zebrafish model based on MIC values. Conclusion: NLS + 2'chalc is a potential new alternative treatment for paracoccidioidomycosis.

Antifungal Activity, Toxicity, and Membranolytic Action of a Mastoparan Analog Peptide

Invasive fungal infections, such as cryptococcosis and paracoccidioidomycosis are associated with significant rates of morbidity and mortality. Cryptococcosis, caused by Cryptococcus neoformans, is distributed worldwide and has received much attention as a common complication in patients with HIV. Invasive fungal infections are usually treated with a combination of amphotericin B and azoles. In addition, 5-fluorocytosine (5-FC) is applied in cryptococcosis, specifically to treat central nervous system infection. However, host toxicity, high cost, emerging number of resistant strains, and difficulty in developing new selective antifungals pose challenges. The need for new antifungals has therefore prompted a screen for inhibitory peptides, which have multiple mechanisms of action. The honeycomb moth Galleria mellonella has been widely used as a model system for evaluating efficacy of antifungal agents. In this study, a peptide analog from the mastoparan class of wasps (MK58911) was tested against Cryptococcus spp. and Paracoccidioides spp. In addition, peptide toxicity tests on lung fibroblasts (MRC5) and glioblastoma cells (U87) were performed. Subsequent tests related to drug interaction and mechanism of action were also performed, and efficacy and toxicity of the peptide were evaluated in vivo using the G. mellonella model. Our results reveal promising activity of the peptide, with an MIC in the range of 7.8-31.2 μg/mL, and low toxicity in MRC and U87 cells (IC₅₀ > 500 μg/mL). Taken together, these results demonstrate that MK58911 is highly toxic in fungal cells, but not mammalian cells (SI > 16). The mechanism of toxicity involved disruption of the plasma membrane, leading to death of the fungus mainly by necrosis. In addition, no interaction with the drugs amphotericin B and fluconazole was found either in vitro or in vivo. Finally, the peptide showed no toxic effects on G. mellonella, and significantly enhanced survival rates of larvae infected with C. neoformans. Although not statistically significant, treatment of larvae with all doses of MK58911 showed a similar trend in decreasing the fungal burden of larvae. These effects were independent of any immunomodulatory activity. Overall, these results present a peptide with potential for use as a new antifungal drug to treat systemic mycoses.

Evaluation of crystal violet decolorization assay and resazurin microplate assay for antimycobacterial screening

The main obstacle in antimycobacterial discovery is the extremely slow growth rates of pathogenic mycobacteria that lead to the long incubation times needed in antimycobacterial screening. Some in vitro testings has been developed and are currently available for antimycobacterial screening. The aim of the study was to compare Resazurin Microplate Assay (REMA) and Crystal Violet Decolorization Assay (CVDA) for testing mycobacteria susceptibility to isoniazid and rifampicin as well as for antimycobacterial screening of natural products (NP). Mycobacterium tuberculosis strain H37Rv and Mycobacterium smegmatis strain mc2 155 were used as tested mycobacteria. Serial two-fold dilutions from 0.0625 to 1.0 μg/mL for the isoniazid and rifampicin and from 6.25 to 100.0 μg/mL for the NP A and B were prepared. Tested mycobacteria were then incubated with tested drugs or NPs in each growth medium at 37 °C for 7 days for M. tuberculosis and 3 days for M. smegmatis. MIC values against M. tuberculosis were interpreted 24-48 h after adding resazurin or at least 72 h after adding crystal violet, whereas MIC values against M. smegmatis were interpreted 1 h after adding resazurin or 24 h after adding crystal violet. The MIC values against M. tuberculosis interpreted by REMA were 0.0625, 0.0625, 6.25, and >100 μg/mL for rifampicin, isoniazid, NP A, and NP B, respectively, and those interpreted by CVDA were 0.0625, 0.0625, 6.25, and >100 μg/mL for rifampicin, isoniazid, NP A, and NP B, respectively. Moreover, the MIC values against M. smegmatis interpreted by REMA were 0.0625, >1, 6.25, and 100 μg/mL for rifampicin, isoniazid, NP A, and NP B, respectively, and those interpreted by CVDA were 0.125, >1, 6.25, and >100 μg/mL for rifampicin, isoniazid, NP A, NP B respectively. In conclusion, REMA is faster and easier than CVDA to interpret MIC values, however CVDA produces higher MIC values than REMA for rifampicin and NP B in M. smegmatis susceptibility testing. Therefore, REMA and CVDA can be used for antimycobacterial screening.

Drug Repurposing for Paracoccidioidomycosis Through a Computational Chemogenomics Framework

Paracoccidioidomycosis (PCM) is the most prevalent endemic mycosis in Latin America. The disease is caused by fungi of the genus Paracoccidioides and mainly affects low-income rural workers after inhalation of fungal conidia suspended in the air. The current arsenal of chemotherapeutic agents requires long-term administration protocols. In addition, chemotherapy is related to a significantly increased frequency of disease relapse, high toxicity, and incomplete elimination of the fungus. Due to the limitations of current anti-PCM drugs, we developed a computational drug repurposing-chemogenomics approach to identify approved drugs or drug candidates in clinical trials with anti-PCM activity. In contrast to the one-drug-one-target paradigm, our chemogenomics approach attempts to predict interactions between drugs, and Paracoccidioides protein targets. To achieve this goal, we designed a workflow with the following steps: (a) compilation and preparation of Paracoccidioides spp. genome data; (b) identification of orthologous proteins among the isolates; (c) identification of homologous proteins in publicly available drug-target databases; (d) selection of Paracoccidioides essential targets using validated genes from Saccharomyces cerevisiae; (e) homology modeling and molecular docking studies; and (f) experimental validation of selected candidates. We prioritized 14 compounds. Two antineoplastic drug candidates (vistusertib and BGT-226) predicted to be inhibitors of phosphatidylinositol 3-kinase TOR2 showed antifungal activity at low micromolar concentrations (<10 μM). Four antifungal azole drugs (bifonazole, luliconazole, butoconazole, and sertaconazole) showed antifungal activity at low nanomolar concentrations, validating our methodology. The results suggest our strategy for predicting new anti-PCM drugs is useful. Finally, we could recommend hit-to-lead optimization studies to improve potency and selectivity, as well as pharmaceutical formulations to improve oral bioavailability of the antifungal azoles identified.

Argentilactone Molecular Targets in Paracoccidioides brasiliensis Identified by Chemoproteomics

Paracoccidioidomycosis (PCM) is the cause of many deaths from systemic mycoses. The etiological agents of PCM belong to the Paracoccidioides genus, which is restricted to Latin America. The infection is acquired through the inhalation of conidia that primarily lodge in the lungs and may disseminate to other organs and tissues. The treatment for PCM is commonly performed via the administration of antifungals such as amphotericin B, co-trimoxazole, and itraconazole. The antifungal toxicity and side effects, in addition to their long treatment times, have stimulated research for new bioactive compounds. Argentilactone is a compound that was isolated from the Brazilian savanna plant Hyptis ovalifolia, and it has been suggested to be a potent antifungal, inhibiting the dimorphism of P. brasiliensis and the enzymatic activity of isocitrate lyase, a key enzyme of the glyoxylate cycle. This work was developed due to the importance of elucidating the putative mode of action of argentilactone. The chemoproteomics approach via affinity chromatography was the methodology used to explore the interactions between P. brasiliensis proteins and argentilactone. A total of 109 proteins were identified and classified functionally. The most representative functional categories were related to amino acid metabolism, energy, and detoxification. Argentilactone inhibited the enzymatic activity of malate dehydrogenase, citrate synthase, and pyruvate dehydrogenase. Furthermore, argentilactone induces the production of reactive oxygen species and inhibits the biosynthesis of cell wall polymers.

Computer-aided identification of novel anti-paracoccidioidomycosis compounds

Aim: The shape-based virtual screening was used for the identification of new compounds anti-paracoccidioidomycosis (PCM). Materials & methods: The study was performed according to the following steps: collection and curation of a dataset of quinolinyl N-oxide chalcones with anti-PCM activity, development and validation of shape-based models, application of the best model for virtual screening, and experimental validation. Results & Conclusion: Among 31 computational hits, eight compounds showed potent antifungal activity and low cytotoxicity for mammalian cells. The checkerboard assay showed that most promising hit (compound 3) displayed additive effects with the antifungal cotrimoxazole and amphotericin B. Therefore, the shape-based virtual screening allowed us to discover promising compounds in prospective hit-to-lead optimization studies for tackling PCM.

Potential of the association of dodecyl gallate with nanostructured lipid system as a treatment for paracoccidioidomycosis: In vitro and in vivo efficacy and toxicity

Paracoccidioidomycosis (PCM) is a systemic mycosis endemic in Latin America, caused by Paracoccidioides spp. A limited number of antifungal agents are available and the search for new compounds has increased. Additionally, nanostructured lipid system (NLS) has emmerged as an interesting strategy to carrier compounds for the treatment of mycosis. In this work, the antifungal efficacy and toxicity of dodecyl gallate (DOD) associated with a NLS was evaluated through in vitro and in vivo tests. DOD showed good in vitro antifungal activity and low toxicity in lung fibroblasts and zebrafish embryos, but no antifungal efficacy in infected mice, which may have been a result of low bioavailability. On the other hand, the association of DOD + NLS was beneficial and resulted in lower toxicity in lung fibroblasts and zebrafish embryos. In addition, NLS + DOD promoted a significant reduction in the fungal burden of mice lungs and could be a potential therapeutic option against PCM.

Antifungal Susceptibility of Emerging Dimorphic Pathogens in the Family Ajellomycetaceae

The in vitro susceptibilities of 24 molecularly identified dimorphic fungi belonging to the genera Adiaspiromyces, Blastomyces, and Emergomyces within the family Ajellomycetaceae were tested against 8 standard antifungal agents using CLSI document M38-A2. Amphotericin B and posaconazole had the lowest geometric mean MICs (<0.05 μg/ml) followed by itraconazole (<0.07 μg/ml), voriconazole (<0.15 μg/ml), and isavuconazole (<0.42 μg/ml) while fluconazole was not active. Micafungin demonstrated good in vitro antifungal activity against Emergomyces (geometric mean minimum effective concentration [GM MEC] 0.1 μg/ml) and Blastomyces (GM MEC <0.017 μg/ml).

Alkyl Protocatechuate-Loaded Nanostructured Lipid Systems as a Treatment Strategy for Paracoccidioides brasiliensis and Paracoccidioides lutzii In Vitro

Dodecyl protocatechuate (dodecyl) is a derivative of protocatechuic acid (3,4-dihydroxybenzoic acid) that possesses anti-oxidant and antifungal properties. Nanostructured lipid systems (NLS) can potentiate the action of many antifungal agents, reducing the required dose and side effects by improving their activity. This work aimed to evaluate dodecyl protocatechuate loaded into a NLS (NLS+dodecyl) as a strategy for the treatment of Paracoccidioides brasiliensis and P. lutzii in vitro. Antifungal activity against P. brasiliensis and P. lutzii was evaluated using the microdilution technique. NLS+dodecyl showed high antifungal activity with a minimum inhibitory concentration ranging from 0.06 to 0.03 μg/mL; 4- to 16-fold higher than that of free dodecyl. NLS+dodecyl was able to inhibit fungal adhesion of the extracellular artificial matrix proteins (laminin and fibronectin), resulting in 82.4 and 81% inhibition, respectively, an increase of 8–17% compared with free dodecyl. These findings corroborate previous results demonstrating 65 and 74% inhibition of fungal adhesion in pulmonary fibroblast cells by dodecyl and NLS+dodecyl, respectively, representing a 9% increase in inhibition for NLS+dodecyl. Subsequently, cytotoxicity was evaluated using the 0.4% sulforhodamine B assay. NLS+dodecyl did not exhibit cytotoxicity in MRC5 (human pneumocyte) and HepG2 (human hepatic carcinoma) cells, thus increasing the selectivity index for NLS+dodecyl. In addition, cytotoxicity was evaluated in vivo using the Caenorhabditis elegans model; neither dodecyl nor NLS+dodecyl exhibited any toxic effects. Taken together, these results suggest that NLS can be used as a strategy to improve the activity of dodecyl against P. brasiliensis and P. lutzii because it improves antifungal activity, increases the inhibition of fungal adhesion in lung cells and the extracellular matrix in vitro, and does not exhibit any toxicity both in vitro and in vivo.

Anti-inflammatory activity of Vismia guianensis (Aubl.) Pers. extracts and antifungal activity against Sporothrix schenckii

ETHNOPHARMACOLOGICAL RELEVANCE

Vismia guianensis (Aubl.) Pers. is traditionally used in North and Northeast of Brazil for the treatment of dermatomycoses. Since the strategy associating immunomodulators with antifungal drugs seems to be promissory to improve the treatment efficacy in fungal infections, we aimed to investigate the antifungal activity of V. guianensis ethanolic extract of leaves (VGL) and bark (VGB) against Sporothrix schenckii ATCC 16345 and their antinflammatory activities.

MATERIAL AND METHODS

The extracts were analyzed by HPLC-DAD-IT MS/MS for in situ identification of major compounds. Antifungal activity was evaluated in vitro (microdilution test) and in vivo using a murine model of S. schenckii infection. The production of TNF-α, IFN-γ, IL-4, IL-10 and IL-12 by measured by ELISA, as well as measured the production and inhibition of the NO after treatment with the plant extracts or itraconazole (ITR).

RESULTS

Two O-glucosyl-flavonoids and 16 prenylated benzophenone derivatives already described for Vismia were detected. Both VGL and VGB showed significant antifungal activity either in in vitro assay of microdilution (MIC=3.9µg/mL) and in vivo model of infection with reduction of S. schenckii load in spleen. It was also observed a predominance of reduction in the production of NO and the proinflammatory cytokines evaluated except TNFα, but with stimulation of IL-10, as evidence of a potential anti-inflammatory effect associated.

CONCLUSION

The results showed that both VGL and VGB have a significant antifungal against S. schenckii and an anti-inflammatory activity. These results can support the use of these extracts for alternative treatment of sporotrichosis.

Peptides Derived from a Phage Display Library Inhibit Adhesion and Protect the Host against Infection by Paracoccidioides brasiliensis and Paracoccidioides lutzii

Paracoccidioides brasiliensis and Paracoccidioides lutzii are dimorphic fungi and are the etiological agents of paracoccidioidomycosis (PCM). Adhesion is one of the most important steps in infections with Paracoccidioides and is responsible for the differences in the virulence of isolates of these fungi. Because of the importance of adhesion to the establishment of an infection, this study focused on the preliminary development of a new therapeutic strategy to inhibit adhesion by Paracoccidioides, thus inhibiting infection and preventing the disease. We used two phage display libraries to select peptides that strongly bind to the Paracoccidioides cell wall to inhibit adhesion to host cells and extracellular matrix (ECM) components (laminin, fibronectin, and type I and type IV collagen). This approach allowed us to identify four peptides that inhibited up to 64% of the adhesion of Paracoccidioides to pneumocytes in vitro and inhibited the adhesion to the ECM components by up to 57%. Encouraged by these results, we evaluated the ability of these peptides to protect Galleria mellonella from Paracoccidioides infection by treating G. mellonella larvae with the different peptides prior to infection with Paracoccidioides and observing larval survival. The results show that all of the peptides tested increased the survival of the larvae infected with P. brasiliensis by up to 64% and by up to 60% in those infected with P. lutzii. These data may open new horizons for therapeutic strategies to prevent PCM, and anti-adhesion therapy could be an important strategy.

Evaluation of the efficacy of antifungal drugs against Paracoccidioides brasiliensis and Paracoccidioides lutzii in a Galleria mellonella model

Paracoccidioides brasiliensis and P. lutzii belong to a group of thermodimorphic fungi and cause paracoccidioidomycosis (PCM), which is a human systemic mycosis endemic in South and Central America. Patients with this mycosis are commonly treated with amphotericin B (AmB) and azoles. The study of fungal virulence and the efficacy and toxicity of antifungal drugs has been successfully performed in a Galleria mellonella infection model. In this work, G. mellonella larvae were infected with two Paracoccidioides spp. and the efficacy and toxicity of AmB and itraconazole were evaluated in this model for the first time. AmB and itraconazole treatments were effective in increasing larval survival and reducing the fungal burden. The fungicidal and fungistatic effects of AmB and itraconazole, respectively, were observed in the model. Furthermore, these effects were independent of changes in haemocyte number. G. mellonella can serve as a rapid model for the screening of new antifungal compounds against Paracoccidioides and can contribute to a reduction in experimental animal numbers in the study of PCM.

Paracoccidioides brasiliensis PS2: First Autochthonous Paracoccidioidomycosis Case Report in Rio de Janeiro, Brazil, and Literature Review

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by pathogenic dimorphic fungi of the Paracoccidioides brasiliensis complex. It is the most important systemic mycosis in Latin America, mainly in Brazil. Despite its severity and high mortality rates, it is considered a neglected disease. Species within the genus Paracoccidioides present genetics and morphological variations with probable clinical, diagnostic and therapeutic consequences. In fact, there are a very small number of detailed case reports with molecular identification of these fungal agents. Here, it is reported a case of PCM due to Paracoccidioides brasiliensis PS2. Molecular identification of the isolate was performed by amplification and sequencing of the arf and gp43 genes. Clinical cases and strain reports with molecular identification in the literature are also reviewed. The case herein presented is the first autochthonous report of PCM due to Paracoccidioides brasiliensis PS2 species in the state of Rio de Janeiro, Brazil, an important endemic area. The patient presented a chronic pulmonary form of PCM and had a satisfactory response to sulfamethoxazole/trimethoprim although sequelae such as adrenal insufficiency and dysphonia were observed. This study may contribute to improve the knowledge about this severe disease, its causative cryptic species and their consequences to patients.

Alkaloids as inhibitors of malate synthase from Paracoccidioides spp.: receptor-ligand interaction-based virtual screening and molecular docking studies, antifungal activity, and the adhesion process

Paracoccidioides is the agent of paracoccidioidomycosis. Malate synthase plays a crucial role in the pathogenicity and virulence of various fungi, such as those that are human pathogens. Thus, an inhibitor of this enzyme may be used as a powerful antifungal without side effects in patients once these enzymes are absent in humans. Here, we searched for compounds with inhibitory capacity against the malate synthase of Paracoccidioides species (PbMLS). The three-dimensional (3D) structure of PbMLS was determined using the I-TASSER server. Compounds were selected from the ZINC database. Based on the mechanism underlying the interaction of the compounds with PbMLS, it was possible to identify β-carboline moiety as a standard key structure. The compounds with β-carboline moiety that are available in our laboratories were investigated. A total of nine alkaloid compounds were selected. The primary mechanisms of interaction of the alkaloid compounds in the binding pocket of PbMLS were identified and compared with the mechanism of interaction of acetyl coenzyme A (acetyl-CoA). We discovered that the amphipathic nature of the compounds, concomitant with the presence of β-carboline moiety, was crucial for their stability in the binding pocket of PbMLS. In addition, the importance of a critical balance of the polar and nonpolar contacts of the compounds in this region was observed. Four β-carboline alkaloid compounds showed the ability to inhibit recombinant PbMLS (PbMLSr) activity, Paracoccidioides species growth, and adhesion of the fungus and PbMLSr to the extracellular matrix components. The cytotoxicity of the alkaloids was also evaluated.

Transcriptome Profile of the Response of Paracoccidioides spp. to a Camphene Thiosemicarbazide Derivative

Paracoccidioidomycosis (PCM) is a systemic granulomatous human mycosis caused by fungi of the genus Paracoccidioides, which is geographically restricted to Latin America. Inhalation of spores, the infectious particles of the fungus, is a common route of infection. The PCM treatment of choice is azoles such as itraconazole, but sulfonamides and amphotericin B are used in some cases despite their toxicity to mammalian cells. The current availability of treatments highlights the need to identify and characterize novel targets for antifungal treatment of PCM as well as the need to search for new antifungal compounds obtained from natural sources or by chemical synthesis. To this end, we evaluated the antifungal activity of a camphene thiosemicarbazide derivative (TSC-C) compound on Paracoccidioides yeast. To determine the response of Paracoccidioides spp. to TSC-C, we analyzed the transcriptional profile of the fungus after 8 h of contact with the compound. The results demonstrate that Paracoccidioides lutzii induced the expression of genes related to metabolism; cell cycle and DNA processing; biogenesis of cellular components; cell transduction/signal; cell rescue, defense and virulence; cellular transport, transport facilities and transport routes; energy; protein synthesis; protein fate; transcription; and other proteins without classification. Additionally, we observed intensely inhibited genes related to protein synthesis. Analysis by fluorescence microscopy and flow cytometry revealed that the compound induced the production of reactive oxygen species. Using an isolate with down-regulated SOD1 gene expression (SOD1-aRNA), we sought to determine the function of this gene in the defense of Paracoccidioides yeast cells against the compound. Mutant cells were more susceptible to TSC-C, demonstrating the importance of this gene in response to the compound. The results presented herein suggest that TSC-C is a promising candidate for PCM treatment.

Antifungal Activity of Decyl Gallate against Several Species of Pathogenic Fungi

This work aims to demonstrate that the gallic acid structure modification to the decyl gallate (G14) compound contributed to increase the antifungal activity against several species of pathogenic fungi, mainly, Candida spp., Cryptococcus spp., Paracoccidioides spp., and Histoplasma capsulatum, according to standardized microdilution method described by Clinical Laboratory Standard Institute (CLSI) documents. Moreover this compound has a particularly good selectivity index value, which makes it an excellent candidate for broad-spectrum antifungal prototype and encourages the continuation of subsequent studies for the discovery of its mechanism of action.