title: Evaluation of the post-antifungal effect (PAFE) of amphotericin B and nystatin against 30 zygomycetes using two different media.
abstract: The post-antifungal effect (PAFE) of amphotericin B and nystatin against 30 clinical zygomycetes was evaluated using two different media. PAFE is a suppression of fungal growth after limited drug exposure. The MICs of both drugs were determined using NCCLS M38-P guidelines. A spectrophotometric method was used to determine PAFE in vitro. Spores were exposed to amphotericin B and nystatin in RPMI-1640 or AM3 at concentrations of 4 x and 1 x MIC for 4 h for Absidia sp. and at 1 x and 0.5 x MIC for 1 h for the other strains. Drugs were eliminated by washing. Exposed and control spores were cultured in microtitre wells and incubated for 48 h. PAFE was calculated as T - C (Delta t) between the control and the exposure fungi. The first increase in optical density (OD0) was used to calculate PAFE and was considered significant when the value of the lower 95%CI of the exposed strain was greater than the upper 95%CI of the control. MIC ranges in RPMI-1640 were: 0.06-4 mg/L for amphotericin B and 0.5-8 mg/L for nystatin; MIC ranges in AM3 were: 0.06-2 mg/L for amphotericin B and 0.5-4 mg/L for nystatin. Killing was not observed at the concentration and exposure time used. In RPMI-1640, for amphotericin B the rank order for PAFE was Absidia corymbifera (5.6 h) > Rhizopus oryzae (5.2 h) > Mucor spp. (3.5 h) > Rhizopus microsporus (3 h), and for nystatin the rank order was Mucor spp. (5.8 h) > R. oryzae (3.3 h) > A. corymbifera (2.9 h) > R. microsporus (1.7 h). PAFE was not induced in Rhizomucor spp. PAFE was dependent on drug concentration.
authors.affiliation: Department of Medical Microbiology, University Medical Center Nijmegen, and Nijmegen University Center for Infectious Diseases, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Roxana G
authors.initials: RG
authors.lastname: Vitale
authors.forename: Jacques F G M
authors.initials: JF
authors.lastname: Meis
authors.forename: Johan W
authors.initials: JW
authors.lastname: Mouton
authors.forename: Paul E
authors.initials: PE
authors.lastname: Verweij
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D003470:Culture Media; D005658:Fungi / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D009181:Mycoses / Q000382:microbiology; D009761:Nystatin / Q000494:pharmacology*; D013172:Spores, Fungal
chemical_list: D000935:Antifungal Agents; D003470:Culture Media; D009761:Nystatin; D000666:Amphotericin B