Evaluation of the Disk Diffusion Method Compared to the Microdilution Method in Susceptibility Testing of Anidulafungin against Filamentous Fungi

We compared the caspofungin (CAS) susceptibility testing results generated by the disk diffusion (DD) assaywith the results of the Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BD) referencemethod for 106 yeast isolates. The isolates represented 11 different fungal species, including Candida albicans(n 50), C. parapsilosis (n 10), C. glabrata (n 10), C. tropicalis (n 10), C. guillermondii (n 6), C. rugosa(n 5), C. krusei (n 5), C. kefyr (n 2), C. pelliculosa (n 2), Saccharomyces cerevisiae (n 3), andGeotrichum candidum (n 3). The DD assay was performed in supplemented Mueller-Hinton agar with CAS,which was tested at concentrations of 2, 10, and 25 g per disk. MICs and inhibition zone diameters wereevaluated at 24 and 48 h. In general, the results obtained by the DD assay correlated well with those obtainedby the BD method. In particular, a significant correlation between methods was observed when CAS was usedat concentration of 2 g/disk at a reading time of either 24 or 48 h.