Sensitivity of yeasts to amphotericin B and 5-fluorocytosine.

One hundred and forty-four clinical yeast isolates were tested for antifungal susceptibility to Amphotericin B (AMB) and 5-Fluorocytosine (5FC). 61% (88 of 144) of the total yeast isolates were C. albicans. Yeasts were most frequently isolated from high vaginal swabs. High vaginal swabs constituted 64% (92 of 144) of the total number of specimens. Antifungal susceptibility testing of yeasts was conducted by employing an agar dilution technique. 76% (67 of 88) of C. albicans demonstrated MIC values of less than or equal to 1.0 ug/ml to 5FC. All yeasts tested against AMB demonstrated MICs of less than or equal to 0.25 ug/ml. Resistance to 5FC and AMB was defined as any isolate demonstrating an MIC of greater than 16 ug/ml and MIC greater than or equal to 2 ug/ml respectively. Based on this definition approximately 6% of total yeasts and 8% of C. albicans were resistant to 5FC. All yeasts tested were sensitive to AMB.

Invasive aspergillosis--a rabbit model.

An invasive aspergillosis model in rabbits was attempted using 3 concentrations of A. fumigatus conidia. Conidia concentrations of 1 x 10(6), 1 x 10(7) and 1 x 10(8) were inoculated intravenously into rabbits. The severity of infection was directly proportional to the inoculum size of the conidia. Aspergillus fumigatus was isolated from livers, kidneys, spleens, hearts and lungs of infected rabbits at a rate of 82%, 75%, 57%, 54% and 32% respectively. Cultures of urine specimens taken by bladder tap were positive for A. fumigatus in 30% of the rabbits tested. Blood cultures using the Bactec Fungal System (Becton Dickinson Corp., USA) failed to isolate A. fumigatus in 20 rabbits with biopsy-proven invasive apergillosis. Active infection with high fungal tissue burden occurred between 2-4 days after infection in rabbits inoculated with 1 x 10(7) conidia.