Comparison of Etests and Vitek 2®with Broth Microdilution for the Susceptibility testing of Cryptococcus neoformans

Ref ID: 19267

Author:

Y. Mahabeer, C. C. Chang, D. Naidu, A. A. Dorasamy, S. Lewin, T. N’dungu, M-Y. S. Moosa, M. A. French, Y. Coovadia, K. P. Mlisana

Author address:

Univ. of Kwazulu-Natal, Durban, SOUTH AFRICA

Full conference title:

53rd Interscience Conference on Antimicrobial Agents and Chemotherapy

Date: 10 September 2014

Abstract:

BACKGROUND: Amphotericin B and fluconazole form the backbone of cryptococcal meningitis (CM) treatment. Monitoring susceptibility to these and other antifungals is essential for the future management of the disease. Broth microdilution (BMD), the reference method, is labour-intensive therefore simpler yet equally reliable alternatives are needed. Etests and Vitek 2® are promising, commercially available alternatives however data of their performance for Cryptococcus neoformans is lacking. We aimed to compare the BMD results of Cryptococcus neoformans with those of Etests and Vitek 2 against amphotericin B, fluconazole, 5 flucytosine & voriconazole.
METHODS: Broth microdilution (BMD), Etests and Vitek 2 were conducted on 102 C.neoformans isolates from CSF of
patients at a tertiary hospital in Durban. BMD was
conducted according to the CLSI M27-A3 document. Etests
and Vitek 2® were carried out according to the
manufacturer’s recommendations. Essential agreements
(EA) were defined as results within 2 dilutions. CLSI
breakpoints (CLSI document M27-S4) were used to
determine categorical agreement (CA).
RESULTS: The EA of Etests for fluconazole and
voriconazole was 95 and 91% respectively but for
amphotericin B, it was 83%. The overall CA for Etests for
these drugs was 98%. For Vitek 2® , the overall EA and CA
for fluconazole, amphotericin B and 5 flucytosine was 96
and 97% respectively. There were 5 minor Etest
fluconazole results and 3 minor 5-flucytosine and
voriconazole errors each for Vitek 2® .
CONCLUSION: The Etests and Vitek 2® correlated very
well with BMD for fluconazole, 5-flucytosine and
voriconazole and these are suitable alternatives for the
susceptibility testing of Cryptococcus neoformans.
However, amphotericin B Etests were less reliable with MIC
values lower than BMD.

Abstract Number: NULL

Conference Year: 2013

Link to conference website: NULL

New link: NULL

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