Promising activity of etomidate against mixed biofilms of fluconazole-resistant Candida albicans and methicillin-resistant Staphylococcus aureus.

Introduction. Candida albicans and Staphylococcus aureus are recognized for their development of resistance and biofilm formation. New therapeutic alternatives are necessary in this context.Hypothesis. Etomidate shows potential application in catheters against mixed biofilms of fluconazole-resistant C. albicans and methicillin-resistant S. aureus (MRSA).Aim. The present study aimed to evaluate the activity of etomidate against mixed biofilms of fluconazole-resistant C. albicans and MRSA.Methodology. The action of etomidate against mature biofilms was verified through the evaluation of biomass and cell viability, and its ability to prevent biofilm formation in peripheral venous catheters was determined based on counts of colony forming units (c.f.u.) and confirmed by morphological analysis through scanning electron microscopy (SEM).Results. Etomidate generated a reduction (P<0.05) in biomass and cell viability starting from a concentration of 250 µg ml-1. In addition, it showed significant ability to prevent the formation of mixed biofilms in a peripheral venous catheter, as shown by a reduction in c.f.u. SEM revealed that treatment with etomidate caused substantial damage to the fungal cells.Conclusion. The results showed the potential of etomidate against polymicrobial biofilms of fluconazole-resistant C. albicans and MRSA.

Analysis of possible pathways on the mechanism of action of minocycline and doxycycline against strains of Candida spp. resistant to fluconazole.

Species of the genus Candida, characterized as commensals of the human microbiota, are opportunistic pathogens capable of generating various types of infections with high associated costs. Considering the limited pharmacological arsenal and the emergence of antifungal-resistant strains, the repositioning of drugs is a strategy used to search for new therapeutic alternatives, in which minocycline and doxycycline have been evaluated as potential candidates. Thus, the objective was to evaluate the in vitro antifungal activity of two tetracyclines, minocycline and doxycycline, and their possible mechanism of action against fluconazole-resistant strains of Candida spp. The sensitivity test for antimicrobials was performed using the broth microdilution technique, and the pharmacological interaction with fluconazole was also analysed using the checkerboard method. To analyse the possible mechanisms of action, flow cytometry assays were performed. The minimum inhibitory concentration obtained was 4-427 µg ml-1 for minocycline and 128-512 µg ml-1 for doxycycline, and mostly indifferent and additive interactions with fluconazole were observed. These tetracyclines were found to promote cellular alterations that generated death by apoptosis, with concentration-dependent reactive oxygen species production and reduced cell viability. Therefore, minocycline and doxycycline present themselves as promising study molecules against Candida spp.

Antifungal activity of selective serotonin reuptake inhibitors against Cryptococcus spp. and their possible mechanism of action.

Fungal infections caused by Cryptococcus spp. pose a threat to health, especially in immunocompromised individuals. The available arsenal of drugs against cryptococcosis is limited, due to their toxicity and/or lack of accessibility in low-income countries, requiring more therapeutic alternatives. Selective serotonin reuptake inhibitors (SSRIs), through drug repositioning, are a promising alternative to broaden the range of new antifungals against Cryptococcus spp. This study evaluates the antifungal activity of three SSRIs, sertraline, paroxetine, and fluoxetine, against Cryptococcus spp. strains, as well as assesses their possible mechanism of action. Seven strains of Cryptococcus spp. were used. Sensitivity to SSRIs, fluconazole, and itraconazole was evaluated using the broth microdilution assay. The interactions resulting from combinations of SSRIs and azoles were investigated using the checkerboard assay. The possible action mechanism of SSRIs against Cryptococcus spp. was evaluated through flow cytometry assays. The SSRIs exhibited in vitro antifungal activity against Cryptococcus spp. strains, with minimum inhibitory concentrations ranging from 2 to 32 µg/mL, and had synergistic and additive interactions with azoles. The mechanism of action of SSRIs against Cryptococcus spp. involved damage to the mitochondrial membrane and increasing the production of reactive oxygen species, resulting in loss of cellular viability and apoptotic cell death. Fluoxetine also was able to cause significant damage to yeast DNA. These findings demonstrate the in vitro antifungal potential of SSRIs against Cryptococcus spp. strains.

Antibacterial activity of menadione alone and in combination with oxacillin against methicillin-resistant Staphylococcus aureus and its impact on biofilms.

Introduction. Antibiotic resistance is a major threat to public health, particularly with methicillin-resistant Staphylococcus aureus (MRSA) being a leading cause of antimicrobial resistance. To combat this problem, drug repurposing offers a promising solution for the discovery of new antibacterial agents.Hypothesis. Menadione exhibits antibacterial activity against methicillin-sensitive and methicillin-resistant S. aureus strains, both alone and in combination with oxacillin. Its primary mechanism of action involves inducing oxidative stress.Methodology. Sensitivity assays were performed using broth microdilution. The interaction between menadione, oxacillin, and antioxidants was assessed using checkerboard technique. Mechanism of action was evaluated using flow cytometry, fluorescence microscopy, and in silico analysis.Aim. The aim of this study was to evaluate the in vitro antibacterial potential of menadione against planktonic and biofilm forms of methicillin-sensitive and resistant S. aureus strains. It also examined its role as a modulator of oxacillin activity and investigated the mechanism of action involved in its activity.Results. Menadione showed antibacterial activity against planktonic cells at concentrations ranging from 2 to 32 µg ml-1, with bacteriostatic action. When combined with oxacillin, it exhibited an additive and synergistic effect against the tested strains. Menadione also demonstrated antibiofilm activity at subinhibitory concentrations and effectively combated biofilms with reduced sensitivity to oxacillin alone. Its mechanism of action involves the production of reactive oxygen species (ROS) and DNA damage. It also showed interactions with important targets, such as DNA gyrase and dehydroesqualene synthase. The presence of ascorbic acid reversed its effects.Conclusion. Menadione exhibited antibacterial and antibiofilm activity against MRSA strains, suggesting its potential as an adjunct in the treatment of S. aureus infections. The main mechanism of action involves the production of ROS, which subsequently leads to DNA damage. Additionally, the activity of menadione can be complemented by its interaction with important virulence targets.

Sertraline has in vitro activity against both mature and forming biofilms of different Candida species.

Candida spp. infections are a serious health problem, especially in patients with risk factors. The acquisition of resistance, often associated with biofilm production, makes treatment more difficult due to the reduced effectiveness of available antifungals. Drug repurposing is a good alternative for the treatment of infections by Candida spp. biofilms. The present study evaluated the in vitro antibiofilm activity of sertraline in reducing the cell viability of forming and matured biofilms, in addition to elucidating whether effective concentrations are safe. Sertraline reduced biofilm cell viability by more than 80 % for all Candida species tested, acting at low and safe concentrations, both on mature biofilm and in preventing its formation, even the one with highest virulence. Its preventive mechanism seemed to be related to binding with ALS3. These data indicate that sertraline is a promising drug with anticandidal biofilm potential in safe doses. However, further studies are needed to elucidate the antibiofilm mechanism and possible application of pharmaceutical forms.

Evaluation of the antifungal effect of chlorogenic acid against strains of Candida spp. resistant to fluconazole: apoptosis induction and in silico analysis of the possible mechanisms of action.

Introduction. Candida spp. are commensal fungal pathogens of humans, but when there is an imbalance in the microbiota, or weak host immunity, these yeasts can become pathogenic, generating high medical costs.Gap Statement. With the increase in resistance to conventional antifungals, the development of new therapeutic strategies is necessary. This study evaluated the in vitro antifungal activity of chlorogenic acid against fluconazole-resistant strains of Candida spp. Mechanism of action through flow cytometry and in silico analyses, as well as molecular docking assays with ALS3 and SAP5, important proteins in the pathogenesis of Candida albicans associated with the adhesion process and biofilm formation.Results. The chlorogenic acid showed in vitro antifungal activity against the strains tested, causing reduced cell viability, increased potential for mitochondrial depolarization and production of reactive oxygen species, DNA fragmentation and phosphatidylserine externalization, indicating an apoptotic process. Concerning the analysis through docking, the complexes formed between chlorogenic acid and the targets Thymidylate Kinase, CYP51, 1Yeast Cytochrome BC1 Complex e Exo-B-(1,3)-glucanase demonstrated more favourable binding energy. In addition, chlorogenic acid presented significant interactions with the ALS3 active site residues of C. albicans, important in the adhesion process and resistance to fluconazole. Regarding molecular docking with SAP5, no significant interactions were found between chlorogenic acid and the active site of the enzyme.Conclusion. We concluded that chlorogenic acid has potential use as an adjuvant in antifungal therapies, due to its anti-Candida activity and ability to interact with important drug targets.