Inoculum standardization for antifungal susceptibility testing of filamentous fungi pathogenic for humans

Two methods of inoculum preparation for filamentous fungi were compared: co unting with a hematocytometer and spectrophotometric adjustment. One hundre d eighty-two filamentous fungi pathogenic for humans were used. Colony coun ts were done for all inoculum preparations. The agreement between the hemat ocytometer counts and the colony counts (CFU per milliliter) was 97.2%. The reproducibility between the hematocytometer counts and the colony counts b y means of an intraclass correlation coefficient was 0.70, Pearson's correl ation index for hematocytometer counts versus colony counts was 0,56, where as that for optical density versus colony counts was 0.008. Both methods ca n he used For inoculum size adjustment. However, the use of the spectrophot ometric method requires that each species be standardized separately.