Conventional Antifungal Drugs Research Articles

Reviewing the Etiologic Agents, Microbe-Host Relationship, Immune Response, Diagnosis, and Treatment in Chromoblastomycosis

Chromoblastomycosis (CBM) is a neglected human disease, caused by different species of pigmented dematiaceous fungi that cause subcutaneous infections. This disease has been considered an occupational disease, occurring among people working in the field of agriculture, particularly in low-income countries. In 1914, the first case of CBM was described in Brazil, and although efforts have been made, few scientific and technological advances have been made in this area. In the field of fungi and host cell relationship, a very reduced number of antigens were characterized, but available data suggest that ectoantigens bind to the cell membrane of host cells and modulate the phagocytic, immunological, and microbicidal responses of immune cells. Furthermore, antigens cleave extracellular proteins in tissues, allowing fungi to spread. On the contrary, if phagocytic cells are able to present antigens in MHC molecules to T lymphocytes in the presence of costimulation and IL-12, a Th1 immune response will develop and a relative control of the disease will be observed. Despite knowledge of the resistance and susceptibility in CBM, up to now, no effective vaccines have been developed. In the field of chemotherapy, most patients are treated with conventional antifungal drugs, such as itraconazole and terbinafine, but these drugs exhibit limitations, considering that not all patients heal cutaneous lesions. Few advances in treatment have been made so far, but one of the most promising ones is based on the use of immunomodulators, such as imiquimod. Data about a standard treatment are missing in the medical literature; part of it is caused by the existence of a diversity of etiologic agents and clinical forms. The present review summarizes the advances made in the field of CBM related to the diversity of pathogenic species, fungi and host cell relationship, antigens, innate and acquired immunity, clinical forms of CBM, chemotherapy, and diagnosis.

Transcriptional Profiling of the Candida auris Response to Exogenous Farnesol Exposure.

ABSTRACTThe antifungal resistance threat posed by Candida auris necessitates bold and innovative therapeutic options. Farnesol is a quorum-sensing molecule with a potential antifungal and/or adjuvant effect; it may be a promising candidate in alternative treatment regimens. To gain further insights into the farnesol-related effect on C. auris, genome-wide gene transcription analysis was performed using transcriptome sequencing (RNA-Seq). Farnesol exposure resulted in 1,766 differentially expressed genes. Of these genes, 447 and 304 genes with at least 1.5-fold increase or decrease in transcription, respectively, were selected for further investigation. Genes involved in morphogenesis, biofilm events (maturation and dispersion), gluconeogenesis, iron metabolism, and regulation of RNA biosynthesis showed downregulation, whereas those related to antioxidative defense, transmembrane transport, glyoxylate cycle, fatty acid β-oxidation, and peroxisome processes were upregulated. In addition, farnesol treatment increased the transcription of certain efflux pump genes, including MDR1, CDR1, and CDR2. Growth, measured by the change in the number of CFU, was significantly inhibited within 2 h of the addition of farnesol (5.8 × 107 ± 1.1 × 107 and 1.1 × 107 ± 0.3 × 107 CFU/ml for untreated control and farnesol-exposed cells, respectively) (P < 0.001). In addition, farnesol treatment caused a significant reduction in intracellular iron (152.2 ± 21.1 versus 116.0 ± 10.0 mg/kg), manganese (67.9 ± 5.1 versus 18.6 ± 1.8 mg/kg), and zinc (787.8 ± 22.2 versus 245.8 ± 34.4 mg/kg) (P < 0.05 to 0.001) compared to untreated control cells, whereas the level of cooper was significantly increased (274.6 ± 15.7 versus 828.8 ± 106.4 mg/kg) (P < 0.001). Our data demonstrate that farnesol significantly influences the growth, intracellular metal ion contents, and gene transcription related to fatty acid metabolism, which could open new directions in developing alternative therapies against C. auris.IMPORTANCE Candida auris is a dangerous fungal pathogen that causes outbreaks in health care facilities, with infections associated with a high mortality rate. As conventional antifungal drugs have limited effects against the majority of clinical isolates, new and innovative therapies are urgently needed. Farnesol is a key regulator molecule of fungal morphogenesis, inducing phenotypic adaptations and influencing biofilm formation as well as virulence. Alongside these physiological modulations, it has a potent antifungal effect alone or in combination with traditional antifungals, especially at supraphysiological concentrations. However, our knowledge about the mechanisms underlying this antifungal effect against C. auris is limited. This study has demonstrated that farnesol enhances the oxidative stress and reduces the fungal survival strategies. Furthermore, it inhibits manganese, zinc transport, and iron metabolism as well as increases fungal intracellular copper content. In addition, metabolism was modulated toward β-oxidation. These results provide definitive explanations for the observed antifungal effects.

Striking Back against Fungal Infections: The Utilization of Nanosystems for Antifungal Strategies.

Fungal infections have become a major health concern, given that invasive infections by Candida, Cryptococcus, and Aspergillus species have led to millions of mortalities. Conventional antifungal drugs including polyenes, echinocandins, azoles, allylamins, and antimetabolites have been used for decades, but their limitations include off-target toxicity, drug-resistance, poor water solubility, low bioavailability, and weak tissue penetration, which cannot be ignored. These drawbacks have led to the emergence of novel antifungal therapies. In this review, we discuss the nanosystems that are currently utilized for drug delivery and the application of antifungal therapies.

Do essential oils from plants occurring in the Brazilian Caatinga biome present antifungal potential against dermatophytoses? A systematic review

The Caatinga is an exclusively Brazilian biome where semiarid climatic conditions promote singularities in adaptive biodiversity. Many aromatic species are found in this region possessing antifungal properties, which are attributed to their essential oils. Thus, we questioned whether essential plant oils found in the Caatinga present anti-dermatophytic potential. Dermatophytes are keratinophilic fungi that cause one of the most prevalent mycoses globally, skin infections known as dermatophytoses (tineas). Here, we provide a comprehensive report of the available published information, analyzing the methods used to evaluate the antifungal activity, verifying the quality of the evidence and possible clinical applications, and discussing research trends in this area. The plants studied concentrated in the genera Croton (Euphorbiaceae), Lippia (Verbenaceae), Piper (Piperaceae), and Mentha (Lamiaceae). All of the studies used in vitro tests to analyze antifungal potential, and little evidence was ascertained concerning the mechanism of antifungal action. In addition, the essential oils also evidenced drug modifying activity of conventional antifungal drugs (Ketoconazole and Terbinafine). We believe that the anti-dermatophyte potential of plant essential oils occurring within the Caatinga is underestimated and that this review will encourage future chemical-pharmacological investigations into the plants within this biome.Key points• The essential oils from plants occurring in the Caatinga Biome present unknown anti-dermatophyte potential.• The studies against dermatophyte fungi concentrate on the families Lamiaceae and Verbenaceae.• In vitro assays were used to assess the anti-dermatophyte potential of the essential oils.

Antifungal Activity and Potential Mechanism of 6,7, 4'-O-Triacetylscutellarein Combined With Fluconazole Against Drug-Resistant C. albicans.

The increased resistance of Candida albicans to conventional antifungal drugs poses a huge challenge to the clinical treatment of this infection. In recent years, combination therapy, a potential treatment method to overcome C. albicans resistance, has gained traction. This study assessed the effect of 6,7,4′-O-triacetylscutellarein (TA) combined with fluconazole (FLC) on C. albicans in vitro and in vivo. TA combined with FLC showed good synergistic antifungal activity against drug-resistant C. albicans in vitro, with a partial inhibitory concentration index (FICI) of 0.0188–0.1800. In addition, the time-kill curve confirmed the synergistic effect of TA and FLC. TA combined with FLC showed a strong synergistic inhibitory effect on the biofilm formation of resistant C. albicans. The combined antifungal efficacy of TA and FLC was evaluated in vivo in a mouse systemic fungal infection model. TA combined with FLC prolonged the survival rate of mice infected with drug-resistant C. albicans and reduced tissue invasion. TA combined with FLC also significantly inhibited the yeast-hypha conversion of C. albicans and significantly reduced the expression of RAS-cAMP-PKA signaling pathway-related genes (RAS1 and EFG1) and hyphal-related genes (HWP1 and ECE1). Furthermore, the mycelium growth on TA combined with the FLC group recovered after adding exogenous db-cAMP. Collectively, these results show that TA combined with FLC inhibits the formation of hyphae and biofilms through the RAS-cAMP-PKA signaling pathway, resulting in reduced infectivity and resistance of C. albicans. Therefore, this study provides a basis for the treatment of drug-resistant C. albicans infections.

Characterization of bacteriocin and chitinase producing bacterial isolates with broad-spectrum antimicrobial activities

There is a need for more efficient and eco-friendly approaches to overcome increasing microbial infections. Bacteriocins and chitinases from Bacillus spp. can be powerful alternatives to conventional antibiotics and antifungal drugs, respectively. The purpose of this study was to assess the inhibitory potential of bacteriocins and chitinase enzymes against multiple resistant bacterial and fungal pathogens. Bacterial isolates were selected by growth on minimal salts medium and after that were morphologically and biochemically characterized. The physiochemical characterization of bacteriocins was carried out. The inhibitory potential of bacteriocins towards six pathogenic bacteria was determined by the well diffusion assay while chitinase activity towards three fungal strains was determined by the dual plate culture assay. Two bacterial strains (WW2P1 and WRE4P2), out of nine showed inhibition of K. pneumonia, P. aeruginosa, E. coli and MRSA while WW4P2 was positive against S. typhimurium and E. coli and WRE10P2 against P. aeruginosa, S. pneumoniae. Two bacterial isolates (WW3P1 and WRE10P2) were chosen for further study on the basis of their antifungal activities. Of these, WW3P1 isolate was more effective against A. fumigatus as well as A. niger. The proteinaceous nature of the bacteriocins was confirmed by treatment of the crude extract with proteinase K. It was found that the inhibitory activity of strain WW3P1 against E. coli was highest at 20 °C, and against S. pneumoniae it was at 20 °C and pH 10 after treatment with EDTA. Inhibition by strain the WRE10P2 against P. aeruginosa was highest at 20 °C and pH 14. It was found that EDTA increased the inhibitory activity of strain WW2P1 against P. aeruginosa, K. pneumoniae and E. coli by 2 ± 0.235, 3.5 ± 0.288, 2.5 ± 1.040 times, respectively, of strain WRE4P2 against P. aeruginosa and E. coli by 2.5 ± 0.763, 2.7 ± 0.5 times, respectively, and of strain WRE10P2 against S. pneumoniae by 3 ± 0.6236 times. The isolates have promising inhibitory activity, which should be further analyzed for the commercial production of antimicrobials.Article highlightsThe current study aimed to isolate the microbiome from wheat plant (Triticum aestivum L.), to screen for bacteriocin production and to assess its antimicrobial activity against human pathogens.Forty-one phenotypically different bacterial colonies were subjected to bacteriocin purification from which 25 colonies showed positive reactions.These 25 bacterial isolates were screened against six different human bacterial pathogens using the well diffusion method to check the antimicrobial activity.Out of nine bacterial isolates, WW3P1 and WRE10P2 were able to degrade the chitin and utilize it as their sole energy source. Strain WRE4P2 exhibited partial inactivation in its activity against MRSA after treatment with proteinase K.

Drug Repurposing in Medical Mycology: Identification of Compounds as Potential Antifungals to Overcome the Emergence of Multidrug-Resistant Fungi.

Immunodepression, whether due to HIV infection or organ transplantation, has increased human vulnerability to fungal infections. These conditions have created an optimal environment for the emergence of opportunistic infections, which is concomitant to the increase in antifungal resistance. The use of conventional antifungal drugs as azoles and polyenes can lead to clinical failure, particularly in immunocompromised individuals. Difficulties related to treating fungal infections combined with the time required to develop new drugs, require urgent consideration of other therapeutic alternatives. Drug repurposing is one of the most promising and rapid solutions that the scientific and medical community can turn to, with low costs and safety advantages. To treat life-threatening resistant fungal infections, drug repurposing has led to the consideration of well-known and potential molecules as a last-line therapy. The aim of this review is to provide a summary of current antifungal compounds and their main resistance mechanisms, following by an overview of the antifungal activity of non-traditional antimicrobial drugs. We provide their eventual mechanisms of action and the synergistic combinations that improve the activity of current antifungal treatments. Finally, we discuss drug repurposing for the main emerging multidrug resistant (MDR) fungus, including the Candida auris, Aspergillus or Cryptococcus species.

In vitro antifungal activity of Thymus vulgaris essential oil nanoemulsion

BackgroundAn essential oil derived from the evergreen plant Thymus vulgaris acts as an antifungal agent with strong antimicrobial activity, but it has low water solubility. The current study therefore aimed to enhance the solubility of thyme essential oil by formulating it into a nanoemulsion and investigating its effectiveness on a broad range of fungi. MethodThe identification of the compositions of essential oils was performed using GC–MS. Thyme essential oil nanoemulsion (TV EO-NE) was prepared by using a high-pressure homogenization method. Both viability and cytotoxicity outcomes on Human fetal foreskin fibroblast cells were gauged by different concentrations of Thymus vulgaris essential oils and TV EO-NE after 24 and 48 h. Antifungal susceptibility tests were carried out based on the modified CLSI M60 document for yeasts and CLSI M28-A3 documents for filamentous fungi. ResultsThyme essential oil was mainly composed of thymol (22.10 %), p-cymene (21.31 %), carvacrol (13.02 %), carvacrol acetate (6.72 %), and linalool (5.58 %). The TV EO-NEs were spherical with a mean diameter of 127.6 ± 62.52 nm and zeta potential of −9.82 ± 6.07 mV. The MIC90 for C. albicans and C. glabrata isolates was 0.031 μg/mL and 0.0625 μg/mL for C. parapsilosis. Also, MIC90 for both dermatophytes and Aspergillus fumigatus isolates was determined to be 0.016 μg/mL. For yeasts and filamentous fungi, a significant reduction in MIC values was observed using TV EO-NE (p < 0.05). ConclusionThe study highlighted T. vulgaris and thymol to be promising alternatives for the treatment of cutaneous mycoses especially when the etiological agents are resistant to conventional antifungal drugs.

Chemical Composition, Antioxidant and Antimicrobial Activity of Nutmeg (Myristica fragrans Houtt.) Seed Essential Oil

This work aimed to isolate the essential oil from the nutmeg (Myristica fragrans Houtt.) seed, to determine the qualitative and quantitative chemical composition of the obtained essential oil, as well as to examine its antioxidant and antimicrobial activity. The essential oil was obtained by Clevenger-type hydrodistillation from the disintegrated nutmeg seed (hydromodulus 1:15 m/V, extraction time 180 minutes). The qualitative and quantitative chemical composition of the nutmeg essential oil was determined by GC/MS and GC/FID analysis. Twenty-five compounds were identified in the nutmeg essential oil and the most abundant was monoterpene hydrocarbon sabinene (42.3 %). The antioxidant activity was spectrophotometrically examined by using DPPH assay. The nutmeg essential oil showed a good antioxidant activity after incubation (EC50 = 1.35 ± 0.003 mg/ml). The antimicrobial activity of the nutmeg essential oil was examined by using a disc diffusion method on Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, B. luteus, Listeria monocytogenes), Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris) and fungus (Candida albicans). The essential oil showed good antifungal and antibacterial activity. The anticandidal activity of the essential oil (28 mm) was comparable to the activity of conventional antifungal drug nystatin (17 mm). Of the tested Gram-positive bacteria, the most sensitive was B. luteus with the inhibition zone diameter of 23 mm, while the tested Gram-negative bacteria showed lower sensitivity. The isolated nutmeg essential oil has the potential for use in the pharmaceutical, chemical and food industry as a natural antioxidant and an antimicrobial agent.

Optimización de variables en ensayos de actividad antifúngica fotodinámica frente a especies de Candida

Oral infections due to yeasts of the genus Candida are very common in patients with predisposing factors, such as physiological conditions or certain underlying diseases. Moreover, oral candidiasis can also evolve into disseminated forms. In this work, strains of the genus Candida were studied to establish the optimal radiation conditions for photosensitizing compounds, in a photodynamic antifungal therapy protocol. A total of 39 isolates were evaluated. The strains were exposed to twelve dyestuffs, eight radiation sources and three different exposure times. Orthotoluidine blue exhibited good photodynamic activity, in combination with exposure to a 20W reflector lamp LED (light-emitting diode) light for 60minutes. When considering the difficulties of using conventional antifungal drugs, the emergence of resistant strains, recurrences, and adverse reactions of certain commonly used drugs, the photodynamic antifungal therapy is a promising strategy for the treatment of localized infections.

Base Excision Repair AP-Endonucleases-Like Genes Modulate DNA Damage Response and Virulence of the Human Pathogen Cryptococcus neoformans.

Pathogenic microbes are exposed to a number of potential DNA-damaging stimuli during interaction with the host immune system. Microbial survival in this situation depends on a fine balance between the maintenance of DNA integrity and the adaptability provided by mutations. In this study, we investigated the association of the DNA repair response with the virulence of Cryptococcus neoformans, a basidiomycete that causes life-threatening meningoencephalitis in immunocompromised individuals. We focused on the characterization of C. neoformans APN1 and APN2 putative genes, aiming to evaluate a possible role of the predicted Apurinic/apyrimidinic (AP) endonucleases 1 and 2 of the base excision repair (BER) pathway on C. neoformans response to stress conditions and virulence. Our results demonstrated the involvement of the putative AP-endonucleases Apn1 and Apn2 in the cellular response to DNA damage induced by alkylation and by UV radiation, in melanin production, in tolerance to drugs and in virulence of C. neoformans in vivo. We also pointed out the potential use of DNA repair inhibitor methoxy-amine in combination with conventional antifungal drugs, for the development of new therapeutic approaches against this human fungal pathogen. This work provides new information about the DNA damage response of the highly important pathogenic fungus C. neoformans.

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

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

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 Photodynamic Activity of Hexyl-Aminolevulinate Ethosomes Against Candida albicans Biofilm.

Biofilm formation is responsible for the development of chronic and recurrent Candida albicans infections. The generation of biofilms is commonly accompanied by high resistance to conventional antifungal drugs, which can increase up to 1,000-fold. Fortunately, antimicrobial photodynamic therapy (aPDT) has shown excellent potential to treat biofilm infections. However, the current most commonly used photosensitizer (PS), aminolevulinic acid (ALA), is hydrophilic, unstable, and has low permeability, leading to unsatisfactory effects on biofilm eradication. To solve these problems, more stable lipophilic PSs and more effective permeability carriers could be considered as two effective solutions. Hexyl-aminolevulinate (HAL) has good bioavailability as a PS, and we proved in a previous study that ethosomes (ES), lipid-based nanocarriers, promote percutaneous drug penetration. In our previous study, a HAL-ES system presented superior photodynamic effects compared to those of ALA or HAL alone. Therefore, here, we aim to evaluate the biological effects of HAL-ES-mediated aPDT on C. albicans biofilm. An XTT sodium salt assay showed that aPDT using 0.5% HAL decreased C. albicans biofilm activity by 69.71 ± 0.43%. Moreover, aPDT with 0.5% HAL-ES further decreased biofilm activity by 92.95 ± 0.16% and inhibited growth of 25.71 ± 1.61% within 48 h, mostly via its effect on the hyphae growth, which correlated with a three-fold increase in C. albicans plasma membrane permeabilization. Notably, HAL-ES-mediated aPDT significantly reduced the sessile minimum inhibitory concentration 50 (SMIC50) of fluconazole to <2.0 μg/ml, and the 21-day survival rate of C. albicans biofilm-infected mice increased from 6.7 to 73.3%. It also significantly reduced the drug resistance and in vivo pathogenicity of C. albicans biofilm. These results demonstrate that HAL-ES-mediated aPDT could be an effective therapy for C. albicans biofilm infections; while also serving as a particularly promising effective treatment for cutaneous or mucocutaneous candidiasis and the prevention of progression to systemic candidiasis.

Oxidation of Isodrimeninol with PCC Yields Drimane Derivatives with Activity against Candida Yeast by Inhibition of Lanosterol 14-Alpha Demethylase.

Candida species cause an opportunistic yeast infection called Candidiasis, which is responsible for more than 50,000 deaths every year around the world. Effective treatments against candidiasis caused by non-albicans Candida species such as C. glabrata, C. parapsilosis, C. aureus, and C. krusei are limited due to severe resistance to conventional antifungal drugs. Natural drimane sesquiterpenoids have shown promising antifungal properties against Candida yeast and have emerged as valuable candidates for developing new candidiasis therapies. In this work, we isolated isodrimeninol (C1) from barks of Drimys winteri and used it as starting material for the hemi-synthesis of four sesquiterpenoids by oxidation with pyridinium chlorochromate (PCC). The structure of the products (C2, C3, C4, and C5) was elucidated by 1D and 2D NMR spectroscopy resulting in C4 being a novel compound. Antifungal activity assays against C. albicans, C. glabrata, and C. krusei revealed that C4 exhibited an increased activity (IC50 of 75 μg/mL) compared to C1 (IC50 of 125 μg/mL) in all yeast strains. The antifungal activity of C1 and C4 was rationalized in terms of their capability to inhibit lanosterol 14-alpha demethylase using molecular docking, molecular dynamics simulations, and MM/GBSA binding free energy calculations. In silico analysis revealed that C1 and C4 bind to the outermost region of the catalytic site of 14-alpha demethylase and block the entrance of lanosterol (LAN) to the catalytic pocket. Binding free energy estimates suggested that C4 forms a more stable complex with the enzyme than C1, in agreement with the experimental evidence. Based on this new approach it is possible to design new drimane-type sesquiterpenoids for the control of Candida species as inhibitors of 14-alpha demethylase.

Chitosan Ameliorates Candida auris Virulence in a Galleria mellonella Infection Model.

Candida auris has emerged as a multidrug-resistant nosocomial pathogen over the last decade. Outbreaks of the organism in health care facilities have resulted in life-threatening invasive candidiasis in over 40 countries worldwide. Resistance by C. auris to conventional antifungal drugs such as fluconazole and amphotericin B means that alternative therapeutics must be explored. As such, this study served to investigate the efficacy of a naturally derived polysaccharide called chitosan against aggregative (Agg) and nonaggregative (non-Agg) isolates of C. aurisin vitro and in vivo. In vitro results indicated that chitosan was effective against planktonic and sessile forms of Agg and non-Agg C. auris In a Galleria mellonella model to assess C. auris virulence, chitosan treatment was shown to ameliorate killing effects of both C. auris phenotypes (NCPF 8973 and NCPF 8978, respectively) in vivo Specifically, chitosan reduced the fungal load and increased survival rates of infected Galleria, while treatment alone was nontoxic to the larvae. Finally, chitosan treatment appeared to induce a stress-like gene expression response in NCPF 8973 in the larvae likely arising from a protective response by the organism to resist antifungal activity of the compound. Taken together, results from this study demonstrate that naturally derived compounds such as chitosan may be useful alternatives to conventional antifungals against C. auris.

BSA nanoparticles loaded-methylene blue for photodynamic antimicrobial chemotherapy (PACT): effect on both growth and biofilm formation by Candida albicans

It has been demonstrated an increase in resistance of Candida albicans to conventional therapies, probably, due the indiscriminate use of the conventional antifungal drugs. In this aspect, the nanotechnology generates the possibility of creating new therapeutic agents. Thus, the objective of this paper was to produce and characterize a bovine serum albumin (BSA) nanoparticle encapsulated with Methylene Blue (MB). In addition, the effect of BSA nanoparticles encapsulated with MB (BSA-MB) was evaluated on both growth and biofilm formation by C. albicans by Photodynamic Antimicrobial Chemotherapy (PACT) protocols. The BSA-MB nanoparticles were prepared by the desolvation process. The nanoparticulate system was studied by steady-state techniques, scanning electron microscopy and their biological activity was evaluated in vitro both growth and biofilm formation by C. albicans. The synthetized BSA-MB nanoparticles were spherical in shape exhibiting a 100–200 nm diameter with a low tendency to aggregate (PDI values < 0.2). MB photophysical properties were shown to be preserved after BSA encapsulation. A significant reduction in C. albicans growth, after PACT was observed, in a dependent manner on MB-loaded in BSA nanoparticles concentration used. It was observed an inhibition of 23, 65 and 83% in the presence of MB-loaded in BSA nanoparticles 0.1, 0.5 and 1.0 µg.mL−1, respectively. In addition, MB-loaded BSA nanoparticles 0.5 µg.mL−1 were able to reduce both biofilm formation (80%) and the transition from yeast to filamentous form by C. albicans. The results presented here demonstrated a potentiation of the phototoxic effect of MB after BSA encapsulation, since the concentrations of MB-loaded BSA nanoparticles necessary to inhibits ∼50% of C. albicans development was 10 times minor than that observed for free MB. Taken together, these results suggest the potential of PACT, using MB-loaded BSA nanoparticles in inhibiting C. albicans development. The synthesis and design of BSA nanoparticles can be successfully applied for MB encapsulation and offer the possibility to drive the toxicity effect to a specific target, as an evaluation on both growth and biofilm formation by Candida albicans.

Anticandidal activity of synthetic peptides: Mechanism of action revealed by scanning electron and fluorescence microscopies and synergism effect with nystatin.

Candida albicans has emerged as a major public health problem in recent decades. The most important contributing factor is the rapid increase in resistance to conventional drugs worldwide. Synthetic antimicrobial peptides (SAMPs) have attracted substantial attention as alternatives and/or adjuvants in therapeutic treatments due to their strong activity at low concentrations without apparent toxicity. Here, two SAMPs, named Mo-CBP3 -PepI (CPAIQRCC) and Mo-CBP3 -PepII (NIQPPCRCC), are described, bioinspired by Mo-CBP3 , which is an antifungal chitin-binding protein from Moringa oleifera seeds. Furthermore, the mechanism of anticandidal activity was evaluated as well as their synergistic effects with nystatin. Both peptides induced the production of reactive oxygen species (ROS), cell wall degradation, and large pores in the C. albicans cell membrane. In addition, the peptides exhibited high potential as adjuvants because of their synergistic effects, by increasing almost 50-fold the anticandidal activity of the conventional antifungal drug nystatin. These peptides have excellent potential as new drugs and/or adjuvants to conventional drugs for treatment of clinical infections caused by C. albicans.

Anticandidal and synergistic effect of essential oil fractions from three aromatic plants used in Cameroon

Despite the use of conventional antifungal drugs, Candida spp resistance, especially mediated by biofilms formation remains recurrent. Therefore, new drugs to treat fungal infections are urgently needed. In this line, our study aimed to determine the anticandidal activity and the synergistic effect of essential oil fractions from Syzygium aromaticum, Cymbopogon citratus and Aeollanthus heliotropioides harvested in Cameroon using a combination approach. Essential oils have been obtained by hydrodistillation and their chemical composition was analysed by GC/MS. Antifungal activity was evaluated by the determination of minimum inhibitory concentration (MIC) using a micro-dilution method. The sorbitol and ergosterol binding ability and anti-biofilm activity were also assessed in order to evaluate the mode of action. The crude essential oils showed a good anticandidal activity, most probably due to the eugenol, linalool and citral content. The combination of two fractions F7 and F10 showed an improved growth inhibition of Candida spp compared to the crude essential oils. The inhibitory effect could be related with the presence of γ-dodecalactone and citronellol as main compounds. The best synergistic combination F7F10 inhibited biofilm formation at ten time reduced combination MIC. The active fractions targeted different fungal cell structures, including cell wall and membrane. Our study showed that the combination of selected essential oils fractions exhibited an increased antifungal activity against Candida spp compared to the crude essential oils. The combination approach of inner compound groups may be used as a promising strategy for the development of efficient recombined micro-essential oils as antifungal agents to face Candida resistance.

Antimicrobial Activity of Essential Oils against Staphylococcus and Malassezia Strains Isolated from Canine Dermatitis.

Staphylococcus spp. bacteria are the most frequently involved agents in canine cutaneous infections. Treatment of these infections is based on antibiotic therapy, that often is not effective because of the antibiotic-resistance of the bacterial strains. Cutaneous staphylococcal infections are often complicated by Malassezia yeasts, that may be resistant to the conventional antifungal drugs. The present investigation was aimed to evaluate the in vitro antimicrobial activity of some essential oils (EOs) in view of a potential cutaneous application. In detail, EOs obtained from lemon verbena (Aloysia triphylla L’Hèr. Britton), cinnamon (Cinnamomum zeylanicum J. Presl), myrrh (Commiphora myrrha (Nees) Engl. var. molmol), lemongrass (Cymbopogon citratus (DC.) Stapf), litsea (Litsea cubeba (Lour.) Pers.), lemon balm (Melissa officinalis L.), oregano (Origanum vulgare L.), savory (Satureja montana L.), and thyme (Thymus vulgaris L.) were assayed against Staphylococcus spp. and Malassezia pachydermatis strains previously isolated from dogs with dermatitis. All EOs were tested by agar disk diffusion and minimum inhibitory concentration methods to verify the antistaphylococcal activity, and by a microdilution method to evaluate the activity against M. pachydermatis. O. vulgare, T. vulgaris, and S. montana showed the best antibacterial activity against all the selected strains, with MICs ranging from 0.29 to 0.58 mg/mL, from 0.58 to 1.16 mg/mL, and from 0.56 to 1.12 mg/mL, respectively, whereas A. triphylla (1.03 mg/mL) and S. montana (1.8 mg/mL) were the most active against M. pachydermatis. After a proper in vivo evaluation, O. vulgare, T. vulgaris, and S. montana EOs could be a promising treatment to combat canine cutaneous mixed infections.