Terpinen-4-ol, tyrosol, and ß-lapachone as potential antifungals against dimorphic fungi

Abstract This study aimed to evaluate the in vitro antifungal activity of terpinen-4-ol, tyrosol, and β-lapachone against strains of Coccidioides posadasii in filamentous phase (n = 22) and Histoplasma capsulatum in both filamentous (n = 40) and yeast phases (n = 13), using the broth dilution methods as described by the Clinical and Laboratory Standards Institute, to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of these compounds. The mechanisms of action of these compounds were also investigated by analyzing their effect on cell membrane permeability and ergosterol synthesis. The MIC and MFCf these compounds against C. posadasii, mycelial H. capsulatum, and yeast-like H. capsulatum, were in the following ranges: 350-5720 µg/mL, 20-2860 µg/mL, and 40-1420 µg/mL, respectively for terpinen-4-ol; 250-4000 µg/mL, 30-2000 µg/mL, and 10-1000 µg/mL, respectively, for tyrosol; and 0.48-7.8 µg/mL, 0.25-16 µg/mL, and 0.125-4 µg/mL, respectively for β-lapachone. These compounds showed a decrease in MIC when the samples were subjected to osmotic stress, suggesting that the compounds acted on the fungal membrane. All the compounds were able to reduce the ergosterol content of the fungal strains. Finally, tyrosol was able to cause a leakage of intracellular molecules.

A non-polyene antifungal antibiotic from Streptomyces albidoflavus PU 23.

In all 312 actinomycete strains were isolated from water and soil samples from different regions. All these isolates were purified and screened for their antifungal activity against pathogenic fungi. Out of these, 22% of the isolates exhibited activity against fungi. One promising strain, Streptomyces albidoflavus PU 23 with strong antifungal activity against pathogenic fungi was selected for further studies. Antibiotic was extracted and purified from the isolate. Aspergillus spp. was most sensitive to the antibiotic followed by other molds and yeasts. The antibiotic was stable at different temperatures and pH tested and there was no significant loss of the antifungal activity after treatment with various detergents and enzymes. Synergistic effect was observed when the antibiotic was used in combination with hamycin. The antibiotic was fairly stable for a period of 12 months at 4 degree C. The mode of action of the antibiotic seems to be by binding to the ergosterol present in the fungal cell membrane resulting in the leakage of intracellular material and eventually death of the cell. The structure of the antibiotic was determined by elemental analysis and by ultraviolet (UV), Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and liquid chromatography mass spectra (LCMS). The antibiotic was found to be a straight chain polyhydroxy, polyether, non-proteinic compound with a single double bond, indicating a nonpolyene antifungal antibiotic.

Las cepas de Candida resistentes a la nistatina se vuelven sensibles al cultivarlas con ergosterol / Candida resistant to mystatin becomes sensitive upon culture with ergosterol

Se aislaron de pacientes dos mutantes de Candida resistentes a la nistatina que se identificaron como C. albicans y C. krusei. Al aislarse requirieron dosis de nistalina 8 a 16 veces mayores que las empleadas para inhibir el crecimiento en la cepa salvaje. Su resistencia bajó en 50 a 75 por ciento durante los siguientes 10 meses, cuando se estabilizaron. El análisis de los esteroles en dichas células mostró ausencia de ergosterol y aumento de un posible precusor. Las células resistentes de C. albicans conservaron su ultraestructuras y no perdieron K+ cuando se trataron con nistatina. Sin embargo, si las mismas células se cultivaban previamente con ergosterol, el tratamiento con nistatina producía cambios drásticos en sus membranas celulares así como pérdida del K+ intracelular. Esto sugiere la incorporación de ergosterol a las membranas de las células resistentes con la consecuente pérdida de la resistencia a la nistatina. La recuperación de la resistencia a la nistatina se obtuvo después de cultivar las células durante cinco días en ausencia de ergosterol