| Congresso Brasileiro de Microbiologia 2023 | Resumo: 1197-1 | ||||
Resumo:Biofilm formation is one of the most important virulence factors of C. albicans. These yeasts are capable of adhering to biotic and abiotic surfaces, in addition to acquiring resistance to most conventional antifungals. As a result, the search for compounds of natural origin with more effective and less toxic antifungal activity to host cells has increased. Recent research demonstrates that essential oil of Lippia origanoides Kunth (syn. Lippia sidoides Cham.) (OELO) has antimicrobial properties, in addition to low toxicity and low cost. These characteristics make OELO a promising alternative for the treatment of infections. In the quest to increase the physical-chemical stability and antimicrobial activity of this volatile compound, nanoemulsions (NEs) were developed. NEs represent a carrier system based on two miscible liquids and a surfactant. Therefore, we analyzed here the antimicrobial potential of OELO and two oil-based nanoemulsions against planktonic cells and biofilm of C. albicans. The OELO was extracted by hydrodistillation and tested against a standard strain (ATCC 90028) and a clinical isolate (LABMIC 0102) of C. albicans. To determine the minimum inhibitory concentration (MIC), the broth microdilution method was used, in accordance with the CLSI M27-A3 standard. The oil and nanoemulsions were tested at range concentrations of 2.4-2,500 μg/mL and amphotericin B (0.01-16 μg/mL). To determine the minimum fungicidal concentration (MFC), 100μL of wells without visual growth were subcultured in Sabouraud Dextrose Agar (SDA). The CFM was the lowest concentration that did not grow in the subculture after 48h at 37°C. For biofilm adhesion inhibition tests, inoculum was added at a concentration of 106 CFU/mL in RPMI medium supplemented with 2% glucose in 96-well plates flat bottom polystyrene. After that, treatments were performed with 2x the MIC of the compounds. Plates were incubated for 48 hours at 37°C. After incubation, the biofilm was washed with saline solution to remove planktonic cells and the metabolic activity was evaluated by adding the XTT-menadione solution. For this, 100 μL of this solution were added to the wells and incubated in the dark for 2 hours at 37ºC. The supernatant was transferred to a new plate and the reading was performed (490nm). The OELO showed the same MIC of 0.078 mg/mL for both strains, while the CFM was 0.312 mg/mL for ATCC 90028 and 0.156 mg/mL for the clinical isolate (LABMIC 0102). For AMB the MIC was 1µg/mL for both strains. Nanoemulsion II showed the same MIC value for strain ATCC90028, while for the clinical isolate the MIC was 0.156 mg/mL. The nanoemulsion IV presented a MIC equal to the CFM, with 0.156 mg/mL. In biofilm quantification assays, ATCC 90028 and LABMIC 0102 biofilms showed a reduction of 78.4% and 72.6% when treated with 2xMIC from OELO. Nanoemulsion II showed a similar effect to the essential oil against the biofilm of the clinical isolate with a 75% reduction, while it showed a smaller reduction against the standard strain. On the other hand, nanoemulsion IV was more effective with a reduction of 89.7% and 81.7% for ATCC 90028 and LABMIC 0102, respectively. The compounds showed an important anti-Candida activity against planktonic cells and biofilm, showing the importance of exploring the potential application in therapy against infections caused by C. albicans. Palavras-chave: antifungal, biofilm, microdilution, virulence, yeast Agência de fomento:Cearense Foundation for Scientific and Technological Development (FUNCAP) and National Council for Scientific and Technological Development (CNPq) | |||||