In Vitro Synergy of Caspofungin and Amphotericin B against Aspergillus and Fusarium spp

Abstract

We investigated the in vitro interaction of caspofungin and amphotericin B for clinical isolates of Aspergillus and Fusarium. Synergy tests were performed using the checkerboard method and following the NCCLS M38-P guidelines in Antibiotic Medium 3 broth supplemented to 2% glucose. Antagonism was not observed for any of the isolates tested. Caspofungin and amphotericin B were synergistic or synergistic to additive for at least half of the isolates.Echinocandins, amphophilic cyclic hexapeptides with an Nlinked acyl side chain, exhibit selective antifungal activity via inhibition of ␤-glucan synthesis. Although caspofungin has proven to be active in vivo against Aspergillus spp. (1, 2; J. Maertens, I. Raad, C. A. Sable, A. Ngai, and R. Berman, Abstr. 40th Intersci. Conf. Antimicrob. Agents Chemother., abstr. 1103Chemother., abstr. , 2000, it has limited in vitro activity when measured using a conventional MIC-0 (complete inhibition of growth) endpoint. Minimum effective concentration (MEC, in micrograms per milliliter) is a microscopic endpoint that may correlate better with the in vivo activity of the echinocandins. The MEC refers to the lowest concentration of the drug that results in the formation of aberrantly growing, unusual hyphal tips (7). We previously demonstrated that the MEC correlates well with the macroscopic MIC-2 (Ϸ50% reduction in turbidity, prominent decrease in growth visually) endpoint (3).While the distinctive mechanisms of action of caspofungin on Aspergillus hyphae make it a good candidate for use in combination with other antifungal agents (C. M. Douglas, J. C. Bowman, G. K. Abruzzo, A. M. Flattery, C. J. Gill, L. Kong, C. Leighton, J. G. Smith, V. B. Pikounis, K. Bartizal, M. B. Kurtz, and H. Rosen, Abstr. 40th Intersci. Conf. Antimicrob. Agents Chemother., abstr. J-1683, 2000), its behavior in combination has been little studied. In an effort to clarify whether enhanced activity against Aspergillus and Fusarium is achieved when caspofungin is combined with another antifungal agent acting via a different mechanism, we performed in vitro synergy studies for caspofungin combined with amphotericin B. The individual caspofungin and amphotericin B MICs (in micrograms per milliliter) were determined initially by using the NCCLS M38-P microdilution methodology (8) in Antibiotic Medium 3 and after 24 and 48 h of incubation. Antibiotic Medium 3 (BBL lot JD4ZSG; Becton Dickinson) was buffered by addition of 1 g of Na 2 HPO 4 and 1 g of NaH 2 PO 4 to each liter of medium (pH ϭ 7) and then supplemented to 20-g/liter glucose (AM3). It was previously shown that AM3 provided good growth and generated slightly lower amphotericin B MICs than did RPMI medium, particularly for some Aspergillus isolates (4). Consistent with data obtained with Candida and amphotericin B (9), this lowering effect might help to differentiate caspofungin-susceptible Aspergillus isolates from caspofungin-resistant ones, and we thus performed the susceptibility tests with AM3. Also, based on the observations that reading at earl...

Novel antifungal agents as salvage therapy for invasive aspergillosis in patients with hematologic malignancies: posaconazole compared with high-dose lipid formulations of amphotericin B alone or in combination with caspofungin

“…[11][12][13][14][15][16] Anecdotal experience at our institution supported these studies' findings and this led to the widespread use of HD-LPD/AMB as salvage treatment for invasive aspergillosis in hematologic malignancy patients. 17 In addition, in vitro studies suggesting that the echinocandin caspofungin has synergistic activity with amphotericin B for at least half of the Aspergillus isolates tested 18 and clinical studies showing that this combination had a response rate exceeding 55% in patients with invasive aspergillosis 19,20 led to our use of HD-LPD/AMB plus caspofungin. From 1999 to 2005, hematologic malignancy patients with invasive aspergillosis at our tertiary-care cancer center were included in compassionate-use trials of posaconazole as salvage therapy.…”

Equinocandinas

“…En cuanto a Aspergillus, son fungistáticas debido a que el -(1,3) d-glucano es sólo incorporado en el crecimiento apical de ramas e hifas, por lo cual sólo se lisan en fase activa de crecimiento 12 . La Tabla 1 resume las concentraciones inhibitorias mínimas (CIM) para algunas especies frecuentes de Aspergillus, en las que presentan un efecto sinérgico con anfotericina y fl uconazol que está aún en estudio, especialmente en lo que se refi ere a caspofugina 13 .…”

Recomendaciones para el tratamiento de la infección por Aspergillus spp.

“…Las combinaciones entre azoles (voriconazol, posaconazol, ravuconazol) o polienos y equinocandinas (caspofungina, micafungina) son por lo general sinérgicas o aditivas. No se observa antagonismo [16][17][18] .…”

“…Otra posibilidad sería el tratamiento combinado, que demuestra sinergia in vitro, entre ambisome o voriconazol y caspofungina 16,17 (BIII). La eficacia de estas dos aproximaciones terapéuticas debe ser confirmada en estudios clínicos futuros.…”

“…Cuando existe fracaso terapéutico, entendiendo como tal la progresión de la enfermedad al final de la primera semana o la estabilidad de las lesiones tras un mes de tratamiento correcto, estaría indicado realizar un tratamiento combinado con anfotericina B liposomal en dosis de 5 mg/kg/día asociada a caspofungina 17 (BIII) o aumentar la dosis de anfotericina liposomal a 10 mg/kg/día (CIII) o el cambio de anfotericina B por caspofungina (BII) sola o asociada a voriconazol 5 (BIII). Sin embargo, en el modelo experimental, esta combinación parece no mejorar de forma ostensible los resultados 21 .…”