RESUMO
El objetivo de este trabajo fue estudiar la susceptibilidad in vitro de aislados de Cryptocococus spp con una nueva clase de antifúngicos, hidrazonas esteroidales y comparar su actividad antifúngica en combinación con ajoeno y posaconazol contra aislados de Cryptococcus spp. Se utilizaron tres aislados del género Cryptococcus 42794, 4050 y 44192 y se evaluaron su sensibilidad y efectos sinérgicos con las hidrazonas esteroidales, ajoeno y posaconazol, según el documento M27-A2 del CLSI. Se incluyeron las cepas Candida albicans (ATCC 90028) y Candida parapsilosis (ATCC 22019) como controles. Se observó con las hidrazonas (H1, H2, H3, H4) un efecto plateau a partir de 10 µM (CMI). Sin embargo, con la H4 se obtuvo bajo porcentaje de inhibición del crecimiento. Con el ajoeno, se obtuvieron valores de CMI de 25 y 50 µM. El posaconazol mostró altos valores de inhibición y un valor de CMI de 6 µM para 42794 y 44192 y un CMI de 20 µM para el aislado 4050. Se obtuvieron efectos sinérgicos al combinar posaconazol con ajoeno, ajoeno con hidrazona 3 y posaconazol con hidrazona 3. Los valores de concentración inhibitoria fraccional fueron de 0,24; 0,16 y 0,09 respectivamente, indicando un marcado efecto sinérgico. Se obtuvieron efectos sinérgicos importantes entre el posaconazol con ajoeno, ajoeno con hidrazona 3 y posaconazol con hidrazona 3, lo cual sería muy útil para futuros estudios clínicos.
The aim of this study was to assess the in vitro susceptibility to novel antifungal compounds, the steroidal hydrazones, and to compare their antifungal activity and synergistic effects with other compounds, such as ajoeno and posaconazole on Cryptocococus spp isolates. Three Cryptococcus strains were used for this study (42794, 4050 and 44192) and their antifungal sensitivity and synergistic effects with ajoeno and posaconazole were evaluated according to the CLSI protocol number M27-A2. Candida albicans (ATCC 90028) and Candida parapsilosis (ATCC 22019) were used as controls. A plateau effect with hydrazones (H1, H2, H3, H4) was observed after 10 µM (CMI). However, with H4 only a mild inhibition on the growth was obtained. Combining hydrazone and ajoeno, CMI values between 25 and 50 µM were obtained. The highest inhibitions values were obtained with posaconazole and a CMI value of 6 µM for the strains 42794 and 44192, and a CMI value of 20 µM for the strain 4050. Synergy was observed combining posaconazole with ajoeno, ajoeno with hydrazone 3 and posaconazole with hydrazone 3. Fractional inhibitory concentrations were 0.24, 0.16 and 0.09 respectively, which might indicate a synergistic effect. Important synergistic effects were obtained with posaconazole and ajoeno, ajoeno and hydrazone 3 and posaconazole with hydrazone 3, which would be very useful for clinical trials in the future.
Assuntos
Antifúngicos/farmacologia , Cryptococcus gattii/efeitos dos fármacos , Cryptococcus neoformans/efeitos dos fármacos , Dissulfetos/farmacologia , Hidrazonas/farmacologia , Técnicas In Vitro , Triazóis/farmacologia , Candida/efeitos dos fármacos , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Farmacorresistência Fúngica , Sinergismo Farmacológico , Testes de Sensibilidade MicrobianaRESUMO
Ketoconazole, a dioxolane imidazole, affects growth and sterol synthesis by Trypanosoma (Schizotryparum) cruzi epimastigotes in a time - and concentration - dependent manner. Starting with a cell density of 10 7 cells/ml, a 10 -4M concentration of the drug blocks instantaneously growth, but with 10 -5M and 10 -6M growth arrest takes place at 48 and 96 hours, respectively. A study of the sterol content of the parasites and their de novo synthesis reveals that the drug induces the accumulation of trimethyl- and, to a much lesser extent, dimethyl-sterols with a progressive decrease of ergosterol-like desmethyl-sterol pool. Sterols added to the growth medium can partially reverse the growth inhibitory effects of ketoconazole, ergosterol being much more effective that cholesterol in this action. These facts suggest an essential function performed in T cruzi by ergosterol, which cannot be replaced by cholesterol, a compound which is passively absorbed from the growth medium and remains in the drug-treated cells. At 10 -6M ketoconazole blocks completely the incorporation of 14C-acetate in desmethyl-sterols and >97% of the radioactivity appears in the trimethyl-sterol fraction at 24 hours; further incubation leads to the appearance of a slight amount of radioactivity in the dimethyl-sterol fraction (10% at 96 hours)..