IntroductionCryptococcus neoformans is one of the leading causes of invasive fungal infections worldwide. Cryptococcal meningoencephalitis is the main challenge of antifungal therapy due to high morbidity and mortality rates, especially in low- and middle-income countries. This can be partly attributed to the lack of specific diagnosis difficulty accessing treatment, antifungal resistance and antifungal toxicity.MethodsIn the present study, the effect of the synthetic thiourea derivative N-(butylcarbamothioyl) benzamide (BTU-01), alone and combined with amphotericin B (AmB), was evaluated in planktonic and sessile (biofilm) cells of C. neoformans.ResultsBTU-01 alone exhibited a fungistatic activity with minimal inhibitory concentrations (MICs) ranging from 31.25 to 62.5 μg/mL for planktonic cells; and sessile MICs ranging from 125.0 to 1000.0 μg/mL. BTU-01 caused a concentration-dependent inhibitory activity on cryptococcal urease and did not interfere with plasma membrane fluidity. Molecular docking was performed on Canavalia ensiformis urease, and BTU-01 showed relevant interactions with the enzyme. The combination of BTU-01 and AmB exhibited synergistic fungicidal activity against planktonic and sessile cells of C. neoformans. Microscopic analysis of C. neoformans treated with BTU-01, alone or combined with AmB, revealed a reduction in cell and capsule sizes, changes in the morphology of planktonic cells; a significant decrease in the number of cells within the biofilm; and absence of exopolymeric matrix surrounding the sessile cells. Neither hemolytic activity nor cytotoxicity to mammalian cells was detected for BTU-01, alone or combined with AmB, at concentrations that exhibited antifungal activity. BTU-01 also displayed drug-likeness properties.ConclusionThese results indicate the potential of BTU-01, for the development of new strategies for controlling C. neoformans infections.

This study aimed to evaluate the antibacterial activity of the dichloromethane/ethyl acetate fraction (named F4a), obtained from the culture of Pseudomonas aeruginosa LV strain in presence of copper chloride, against planktonic and sessile cells of Staphylococcus aureus, including those presenting multidrug resistance. First, the minimal inhibitory concentrations (MIC) of F4a for twenty-six clinical isolates were determined and the values ranged from 1.56 to 6.25 µg/mL. Minimal bactericidal concentration (MBC) of 3.13 µg/mL was detected in 84.6% of the isolates. The time-kill curve analysis revealed a significant decreased in colony-forming unit counts after 4 h of treatment with the MIC/MBC of F4a. Moreover, the MIC/MBC of the fluopsin C, a copper-containing compound present in F4a, were 1.56/3.13 µg/mL, indicating that this compound seems to be one of the active components related to the antibacterial activity against S. aureus. Images of transmission electron microscopy showed significant ultrastructural alterations in planktonic cells treated with the MIC/MBC of F4a. A significant reduction in the metabolic activity of established biofilms of all S. aureus isolates was observed after treatment with F4a. No hemolytic activity to human erythrocytes was detected for F4a, and the cytotoxic concentration to LLC-MK2 cells was 3.44 µg/mL. In conclusion, F4a exhibited a bactericidal activity against planktonic cells and inhibited the metabolic activity of biofilms of S. aureus. F4a can be promising for the development of new strategies for the treatment of infections caused by S. aureus.