Antifungal Combination of Ethyl Acetate Extract of Poincianella pluviosa (DC.) L. P. Queiros Stem Bark With Amphotericin B in Cryptococcus neoformans

Abstract

Cryptococcus neoformans is the leading cause of cryptococcosis, an invasive and potentially fatal infectious disease. Therapeutic failures are due to the increase in antifungal resistance, the adverse effects of drugs, and the unavailability of therapeutic regimens in low-income countries, which limit the treatment of cryptococcosis, increasing the morbidity and mortality associated with these infections. Thus, new antifungal drugs and innovative strategies for the cryptococcosis treatment are urgently needed. The aim of the present study was to evaluate the effect of ethyl acetate fraction (EAF) of Poincianella pluviosa stem bark on planktonic and biofilm mode of growth of C. neoformans. Furthermore, the interaction between the EAF and amphotericin B (AmB) was evaluated in vitro and in Galleria mellonella infection model. Minimal inhibitory concentrations (MICs) of EAF ranged from 125.0 to >1,000.0 μg/ml and >1,000.0 μg/ml for planktonic and sessile cells, respectively. The combination between EAF and AmB exhibited a synergistic fungicidal activity toward C. neoformans, with a fractional inhibitory concentration index (FICI) ranging from 0.03 to 0.06 and 0.08 to 0.28 for planktonic and sessile cells, respectively. Microscopy analyses of planktonic C. neoformans cells treated with EAF, alone or combined with AmB, revealed morphological and ultrastructural alterations, including loss of integrity of the cell wall and cell membrane detachment, suggesting leakage of intracellular content, reduction of capsule size, and presence of vacuoles. Moreover, EAF alone or combined with AmB prolonged the survival rate of C. neoformans-infected G. mellonella larvae. These findings indicate that P. pluviosa may be an important source of new compounds that can be used as a fungus-specific adjuvant for the treatment of cryptococcosis.

Synergistic antifungal interaction of N-(butylcarbamothioyl) benzamide and amphotericin B against Cryptococcus neoformans

“…Actually, AmB combined with flucytosine is considered the standard fungicidal treatment for cryptococcal meningitis ( WHO, 2018 ), and is associated with improved survival of patients with cryptococcal meningitis compared to treatment with AmB monotherapy ( Molloy et al, 2018 ; Loyse et al, 2019 ; Vidal et al, 2021 ). In vitro experiments also suggest that combinations of natural and/or synthetic compounds with available antifungals can improve the effectiveness of treatments and extend the efficacy of currently used antifungal agents ( Andriani et al, 2021 ; Benelli et al, 2021 ; Iyer et al, 2021 ). The synergistic fungicidal interaction between BTU-01 and AmB may contribute to developing new strategies for controlling cryptococcosis meningitis.…”