1641. Susceptibility Testing of Candida glabrata Isolates Collected in a 7-year Study: Continued Need for Antifungal Susceptibility Monitoring of Bloodstream Isolates
Session: Poster Abstract Session: Mycology - There's a Fungus Among Us: Treatment
Friday, October 28, 2016
Room: Poster Hall
Posters
  • IDWeek 2016 Candida poster FINAL.pdf (357.1 kB)
  • Background:

    Azoles and echinocandins are commonly used for treatment of invasive fungal infections. Resistance by Candida glabrata to echinocandins is emerging. Availability of antifungal susceptibility testing of bloodstream isolates (especially C. glabrata) is necessary for appropriate therapy. The aim of this study was to determine antifungal susceptibilities for C. glabrata and compare results from two testing methods.

    Methods:

    A total of 429 Candida blood culture isolates were collected from unique New Orleans patients during 2009-2015. Of these, 151 (35%) were C. glabrata (146 viable for testing). Caspofungin and fluconazole MICs were determined by two FDA-approved antifungal susceptibility testing methods, the Vitek® 2 system and the Etest® method. Vitek MICs were finalized in an average time of 13h; Etest MICs were read at 24h.

    Results:

    C. glabrata Vitek 2 and Etest determined caspofungin resistance ranged from 6% to 7%, respectively; fluconazole resistance, 12% to 23%, respectively. MICs determined by Etest were frequently higher than Vitek MICs. Perhaps this was due to subjectivity when reading an endpoint at 80% inhibition when diffuse growth or trailing endpoints were present. The Vitek 2 occasionally terminated the fluconazole MIC, due to insufficient growth. Current (2012) CLSI interpretive MIC (µg/mL) guidelines for C. glabrata are: caspofungin (<0.12 S, 0.25 I, >0.5 R) and fluconazole (<32 SDD, >64 R). Voriconazole was not evaluated in this study since CLSI breakpoints are not available for C. glabrata. Caspofungin MICs (<0.25) reported by the Vitek could not be differentiated as S (<0.12) or I (0.25). Essential agreement of MICs (within 2 two-fold dilutions) between Vitek and Etest was 144/146 (99%) for caspofungin and 142/156 (91%) for fluconazole.

    Conclusion:

    The agreement between the Vitek 2 and Etest methods was high, with the Vitek 2 being easier and more rapidly performed than Etest. Antifungal susceptibility testing should be performed on Candida glabrata isolates from bloodstream infections to detect in vitro resistance and optimize antifungal therapy.

    George Pankey, MD, FIDSA1, Deborah Ashcraft, B.S.1 and Julia Garcia-Diaz, MD, FIDSA2, (1)Institute of Translational Research; Laboratory of Infectious Disease Research, Ochsner Clinic Foundation, New Orleans, LA, (2)Infectious Diseases, Ochsner Clinic Foundation, New Orleans, LA

    Disclosures:

    G. Pankey, None

    D. Ashcraft, None

    J. Garcia-Diaz, None

    Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.