Determination of Echinocandin MICs for Candida species in less than 8 hours: comparison of the rapid susceptibility assay with the Clinical and Laboratory Standards Institute's broth microdilution assay.


Journal Article

The echinocandins prevent fungal cell wall synthesis by inhibiting beta-1,3-glucan synthesis, a significant glucose-consuming process. Previous studies suggested that echinocandin inhibitory activity is evident within 1 h of exposure. We hypothesized that a susceptibility assay based on glucose consumption may provide clinically useful MICs rapidly. The rapid susceptibility assay (RSA), which provides MICs in less than 8 h, was compared with the standard broth microdilution susceptibility assay (Clinical and Laboratory Standards Institute, document M27-A3, 2008) for 56 Candida species strains. Variables which are known to influence MICs determined by the M27-A3 method were also assessed for their effects on the RSA results. Excellent agreement (>90%) between the results of the RSA and M27-A3 methods was achieved for all three FDA-approved echinocandins (micafungin, caspofungin, and anidulafungin). Candida lusitaniae strains were responsible for most of the discordant results. Assay variables such as the test medium, the age of the inoculum culture, and the presence of human serum affected MIC results from the RSA and the M27-A3 method similarly. The RSA is equivalent to the standard M27-A3 method for determining echinocandin MICs for Candida species. The RSA provides MIC results in less than 8 h and can be applied to old and young yeast colonies. The assay could potentially provide clinically useful MICs on the same day that yeast growth from a specimen is first detected on solid medium.

Full Text

Cited Authors

  • Hazen, KC; Dirks, D; Masuoka, J

Published Date

  • December 2009

Published In

Volume / Issue

  • 47 / 12

Start / End Page

  • 4043 - 4048

PubMed ID

  • 19846655

Pubmed Central ID

  • 19846655

Electronic International Standard Serial Number (EISSN)

  • 1098-660X

International Standard Serial Number (ISSN)

  • 0095-1137

Digital Object Identifier (DOI)

  • 10.1128/JCM.01306-09


  • eng