Disk Diffusion Method for Determining Susceptibilities of Candida spp. to MK-0991

We have developed an agar-based methodology for testing susceptibilities of Candida spp. to the new antifungal agent MK-0991, a glucan synthase inhibitor. Results obtained with this method correlated well with the results obtained by the National Committee for Clinical Laboratory Standards M27-A broth microdilution reference method. However, as noted with prior comparisons of broth- and agar-based systems, some isolates yielded inhibition zones which were not consistent with the MICs obtained for them. Understanding the implications of these differences will require testing in an in vivo system.