Clinical utility of antifungal susceptibility testing

Abstract

Invasive fungal diseases cause significant morbidity and mortality, in particular affecting immunocompromised patients. Resistant organisms are of increasing importance, yet there are many notable differences in the ability to both perform and interpret antifungal susceptibility testing compared with bacteria. In this review, we will highlight the strengths and limitations of resistance data of pathogenic yeasts and moulds that may be used to guide treatment and predict clinical outcomes.

Figure 1.

Examples of antifungal susceptibility testing. Examples of various phenotypic susceptibility results for yeasts and moulds. (a) shows the results of broth microdilution susceptibility testing per the Clinical and Laboratory Standards Institute methodology for fluconazole against Candida albicans, voriconazole against Aspergillus fumigatus, and amphotericin B against Purpureocillium lilacinum. (b) shows susceptibility results as measured by the YeastOne colorimetric assay against Candida species. (c) shows susceptibility results as measured by gradient diffusion for amphotericin B against A. fumigatus, isavuconazole against Cryptococcus neoformans, and caspofungin against Candida glabrata. (d) shows the minimum effective concentration (MEC) results for micafungin against an Aspergillus nidulans and an unidentified mould isolate. All testing was performed in the Fungus Testing Laboratory at the University of Texas Health Science Center at San Antonio. Red boxes in (a), (b) and (d) indicate minimum inhibitory concentration (MIC)/MEC values. Figure and legend reused with permission from: Wiederhold NP. Antifungal susceptibility testing: a primer for clinicians. Open Forum Infect Dis 2021; 8: ofab444; https://doi.org/10.1093/ofid/ofab444 (CC BY-NC-ND 4.0). Part labels have been re-lettered and spellings in the legend have been changed to UK English in line with JAC-AMR style.