In vitro antifungal activities of amphotericin B and liposome-encapsulated amphotericin B

Abstract

The in vitro activities of lipsome-encapsulated amphotericin B and free amphotericin B against Candida albicans 336 were comparable. Amphotericin B concentrations 12-fold and greater than 50-fold higher were required to kill the same organism when cholesterol and ergosterol were incorporated into the liposomes. The addition of cholesterol to liposomes caused a significant increase in the minimal fungicidal concentration of amphotericin B in 7 of 19 other yeast strains tested, whereas ergosterol caused an increase in 18 of the 19 strains.Although there have been numerous reports on the use of liposome-encapsulated amphotericin B (L-AmpB) in the treatment of various infections in experimental animals (1,(4)(5)(6)8), this is the first report on the in vitro activity of LAmpB against various fungi. In the initial phase of this study, the lipid concentration of the liposomes was held constant with changing amphotericin B (AmpB) concentrations. However, later results showed that the minimal fungicidal concentrations (MFCs) were no different when both the L-AmpB and the lipid concentrations were serially diluted.(These data were presented in part at the 82nd Annual Meeting of the American Society for Microbiology, New Orleans, La., 7 March 1983 [R. L. Hopfer, K. Mills, G. Lopez-Berestein, R. Mehta, V. Fainstein, and R. L. Juliano, Abstr. Annu. Meet. Am. Soc. Microbiol. 1983, F24, p. 386].)The formulation of L-AmpB has been previously described (5). Candida albicans 336, the strain used in the infected animal model (5), was grown overnight at 37°C on Sabouraud glucose agar plates. Cells were harvested by gently flushing the surfaces of the plates with sterile saline. The cells were washed two times, suspended in saline, and adjusted to 95% transmission of light (540 nm) with a Spectronic 20 (Bausch & Lomb, Inc., Rochester, N.Y.). Determination of antifungal susceptibility was performed by using the dilution methods described by Shadomy and Espinel-Ingroff (7). A 2-ml amount of buffered yeast-nitrogen base broth was used to serially dilute the various drug preparations. The concentrations of AmpB (free and liposomal) tested ranged from 0.05 to 50.0 ,g of AmpB per ml of broth. Tubes were inoculated with 50 RI of the cell inoculum.Plate count studies indicated an initial colony count of 5 x 103 colonies per ml. MICs were not determined due to the turbidity of the liposomal preparations. The MFCs were determined after 18 h of incubation at 35°C. All tubes were subcultured (10 pul) onto Sabouraud glucose agar plates. The MFC was defined as the lowest concentration of drug that allowed no growth or fewer than four colonies on the subculture plates. Since the MICs could not be determined, the inhibitory effect of the lower concentrations of the drugs was determined after 18 h of incubation at 35°C. For these * Corresponding author. 387 data, 0.1 ml was removed from all drug concentrations tested. Serial dilutions (10-fold) were made, and 0.1 ml of each dilution (in duplicate) was plated onto Sabouraud glucose agar plates. Colo...

Eficiência terapêutica das formulações lipídicas de anfotericina B

“…Alguns investigadores relataram eficiência terapêu-tica equivalente entre AmBisome e AB-DOC (Hopfer, Mehta, Lopez-Berestein, 1987), enquanto outros encontraram significativa redução na atividade antifúngica para a formulação lipídica (Hopfer et al, 1984;. Pahls e Schaffner (1994) também compararam AmBisome com AB-DOC quanto à atividade antifúngica in vitro e em modelos de candidíase sistêmica e localizada em camundongos imunocomprometidos.…”

“…Segundo os autores, isto ocorreu devido ao fato de que 50% de AB não se apresentava encapsulada nesta formulação. Hopfer et al (1984) relataram resultados semelhantes com lipossomas preparados com DMPC:DMPG. Desta forma, os autores propuseram que a necessidade de maior tempo de incubação influenciaria a atividade antifúngica devido à liberação da AB encapsulada.…”

Effects of antibiotics and medium supplements on steroidogenesis in cultured cow luteal cells

“…Amphotericin-B acts as an ionophore, com¬ bining with sterols (predominantly ergosterol) in the fungal cytoplasmic membrane to form porous channels (Kinsky, 1962;Feingold, 1965). The ability of amphotericin-B to bind to cholesterol and ergosterol has been well documented (De Kruijff et al, 1974;Hopfer et al, 1984). Cholesterol is a major lipid component of cell membranes, interacting with phospholipids within the membrane, modulating membrane fluidity (Whetton et al, 1983).…”

Effects of free and liposomal amphotericin B and gramicidin S alone and in combination on potassium leakage from human erythrocytes and Candida albicans

“…Liposome encapsulation of AmpB has been demonstrated to enhance the therapeutic index of the drug (7,(9)(10)(11)(12) partly by decreasing toxicity to human erythrocytes (RBC) while maintaining its in vivo antifungal efficacy (10). Studies from our laboratory have shown that AmpB and liposomal AmpB (L-AmpB) have comparable antifungal activity in vitro against several strains of Candida albicans (7). Antifungal activity has also been improved by using drug combinations (1,6,11,13).…”

“…However, despite its efficacy, the drug has severe side effects that are related to its interaction with the plasma membranes of mammalian cells (1,4,5,8). Liposome encapsulation of AmpB has been demonstrated to enhance the therapeutic index of the drug (7,(9)(10)(11)(12) partly by decreasing toxicity to human erythrocytes (RBC) while maintaining its in vivo antifungal efficacy (10). Studies from our laboratory have shown that AmpB and liposomal AmpB (L-AmpB) have comparable antifungal activity in vitro against several strains of Candida albicans (7).…”