The purpose of this study was to assess the antifungal activity of a new oral amphotericin B (AmpB) lipid-based formulation following administration to rats infected with Aspergillus fumigatus. Aspergillus fumigatus inoculum (2.1-2.5 x 10(7) colony forming units [CFU]) were injected via the jugular vein; 48h later male albino Sprague-Dawley rats (350-400 g) were administered either a single oral dose of AmpB incorporated into Peceol (50 mg AmpB/kg), physiologic saline (nontreated controls) or Peceol alone (vehicle control) once daily for 4 days. To assess antifungal activity Brain, Lung, Heart, Liver, Spleen and Kidney sections were homogenized with normal saline (1 mL/g of tissue) and a 0.1-mL aliquot was spread plated onto a Sabourand dextrose agar plate. The plates were incubated for 48 hr at 37 degrees C, at which time the number of fungal CFU were determined and corrected for tissue weight. In addition, plasma galactomannan antigen concentrations were determined. Data was reported as mean +/- standard error of the mean. The AmpB-Peceol oral formulation significantly decreased total fungal CFU concentrations recovered in all the organs added together, brain CFU concentrations, spleen CFU concentrations and plasma galactomannan antigen concentrations compared to baseline. No significant differences in lung, heart, liver and kidney CFU concentrations between treatment and control groups were observed. Peceol vehicle control did not exhibit any antifungal activity. These findings suggest that a new oral lipid-based formulation of AmpB incorporated into Peceol can significantly decrease brain and spleen CFU concentrations and plasma galactomannan antigen concentrations compared to non-treated controls.