Aspergillus fumigatus susceptibility testing by colorimetric microdilution

Purpose. This study is a preliminary evaluation of the Sensititre Plates Co lorimetric Method (SPCM), compared with the Standard Microdilution Method ( SMM), for antifungal susceptibilities determination on Aspergillus fumigatu s in chronically colonised cystic fibrosis patient. Material. Methods. Seventeen A. fumigatus strains obtained from 17 differen t cystic fibrosis patient were studied by SPCM and SMM. Results. Conclusion. The colorimetric method (read at 48 h or 72 h) gave co mparable minimum inhibitory concentration (MICs) to the standard method for amphotericin B (48 h); in the case of ketoconazole and itraconazole, the n ew method (read at 24 h) also offered similar results to the standard metho d at 48 h. In general, at all periods of observation, the colorimetric test tended to increase or decrease the MIC by only one dilution when compared with the conventional test. The determination of the MIC with the colorimet ric method is easy to read and adaptable to everyday practice in the microb iological laboratory.