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Candidaspp. can be found in the human microbiome. However, immunocompromised patients are likely to develop invasive Candidainfections, with mortality rates higher than 50%. The discovery of C. auris, a species that rapidly acquire antifungal resistance, increased the concern about Candidainfections. The limited number of antifungal agents and the high incidence of resistance to them make imperative the development of new antifungal drugs. β-lapachone is a biological active naphthoquinone that displays antifungal activity against C. albicansand C. glabrata. The aim of this study was to evaluate if this substance affects C. aurisgrowth and elucidate its mechanism of action. A fluconazole-resistant C. aurisisolate was used in this study. The antifungal activity of β-lapachone was determined through microbroth dilution assays, and its mechanism of action was evaluated using fluorescent probes. Interaction with fluconazole and amphotericin B was assessed by disk diffusion assay and checkerboard. β-lapachone inhibited planktonic C. auriscell growth by 92.7%, biofilm formation by 84.9%, and decrease the metabolism of preformed biofilms by 87.1% at 100 µg/ml. At 100 µg/ml, reductions of 30% and 59% of Calcofluor White and Nile red fluorescences were observed, indicating that β-lapachone affects cell wall chitin and neutral lipids content, respectively. Also, the ratio 590 nm/529 nm of JC-1 decreased 52%, showing that the compound affects mitochondria. No synergism was observed between β-lapachone and fluconazole or amphotericin B. Data show that β-lapachone may be a promising candidate to be used as monotherapy to treat C. aurisresistant infections.

Oral candidiasis can be presented in different ways due to the virulence factors of its etiology such as Candida albicansthat have developed an effective set of these factors that are able to improve its pathogenesis. The role of salivary immunological components in the development of candidiasis can provide insights for the development of new methodologies aiming to control this disease. The aim of this study was to evaluate the antifungal activity of two salivary components, histatin 5 and lactoferrin on C. albicansviability and virulence using a fluconazole resistant C. albicansclinical strain. Results showed that histatin 5 and lactoferrin decreased cell viability, and the cell surface hydrophobicity was increased by 18% in presence of 151 µg/mL of histatin 5 but was not altered by lactoferrin. It was observed the reduction of 69.3% in the expression of mannoproteins on C. albicanssurface in the presence of 151 µg/mL of histatin, but proteolytic activity of serine proteinases was not inhibited by any of the proteins. Histatin 5 altered cell ultrastructure predominantly in the cytoplasmic compartment. However, this peptide does not interfere with mitochondrial function neither in membrane permeability of the yeasts. The association index between C. albicansand epithelial cells was increased by 51% in presence of 151 µg/mL of histatin. Results suggest that histatin 5 and lactoferrin affects viability and virulence of C. albicansat physiological levels, and the maintenance of these levels may be essential in the prevention of oropharyngeal candidiasis. Exogenous administration of these proteins may become a therapeutic alternative for resistant strains of C. albicans, circumventing toxicity issues, considering their constitutive features.

Objectives: The aim of this study was to evaluate the ability of lapachones in disrupting the fungal multidrug resistance (MDR) phenotype, using a model of study which an azole-resistant Saccharomyces cerevisiaemutant strain that overexpresses the ATP-binding cassette (ABC) transporter Pdr5p. Methods: The evaluation of the antifungal activity of lapachones and their possible synergism with fluconazole against the mutant S. cerevisiaestrain was performed through broth microdilution and spot assays. Reactive oxygen species (ROS) and efflux pump activity were assessed by fluorometry. ATPase activity was evaluated by the Fiske and Subbarow method. The effect of β-lapachone on PDR5mRNA expression was assessed by RT-PCR. The release of hemoglobin was measured to evaluate the hemolytic activity of β-lapachone. Results: α-nor-Lapachone and β-lapachone inhibited S. cerevisiaegrowth at 100 μg/ml. Only β-lapachone enhanced the antifungal activity of fluconazole, and this combined action was inhibited by ascorbic acid. β-Lapachone induced the production of ROS, inhibited Pdr5p-mediated efflux, and impaired Pdr5p ATPase activity. Also, β-lapachone neither affected the expression of PDR5nor exerted hemolytic activity. Conclusions: Data obtained indicate that β-lapachone is able to inhibit the S. cerevisiaeefflux pump Pdr5p. Since this transporter is homologous to fungal ABC transporters, further studies employing clinical isolates that overexpress these proteins will be conducted to evaluate the effect of β-lapachone on pathogenic fungi.