Determination of the minimal inhibitory concentration of amphotericin B and miconazole for 21 strains of Aspergillus.

The susceptibility of 21 strains of Aspergillus (11 of A. fumigatus, 8 of A, niger, and 2 of A. flavus) isolated from human pathologic specimens to Amphotericin B and Miconazole has been comparatively studied. Determination of the minimal inhibitory concentration of both drugs in a liquid medium showed a noticeably variability for the different strains. The values obtained for Amphotericin B varied between 0.25 microgram/ml (2 strains) and 1.25 microgram/ml (5 strains) after 48 hours, and between 1,25 microgram/ml (1 strain) and 50 microgram/ml (1 strain) after 10 days. For Miconazole the results varied between 0.1 microgram/ml (1 strain) and 25 microgram/ml (1 strain) after 48 hours of incubation, and between 0.5 microgram/ml (5 strains) and greater than 100 microgram/ml after 10 days. The variability of these results indicates the usefulness of carrying our in vitro sensitivity studies whenever it is possible.