Comparison of Etests and Vitek 2 ® to broth microdilution for the susceptibility testing of Cryptococcus neoformans

Yesholata Mahabeer; Christina C Chang; Dianithi Naidu; Afton Dorasamy; Sharon Lewin; Thumbi Ndung'u; Mohammed-Yunus Moosa; Martyn French; Koleka Mlisana; Yacoob Coovadia

doi:10.1016/j.diagmicrobio.2014.09.006

Comparison of Etests and Vitek 2 ® to broth microdilution for the susceptibility testing of Cryptococcus neoformans

Diagn Microbiol Infect Dis. 2014 Dec;80(4):294-8. doi: 10.1016/j.diagmicrobio.2014.09.006. Epub 2014 Sep 16.

Authors

Affiliations

¹ Department of Medical Microbiology, National Health Laboratory Services, Durban, South Africa; School of Laboratory Medicine and Medical Sciences, Nelson R. Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa. Electronic address: mahab@ukzn.ac.za.
² Department of Infectious Diseases, Alfred Hospital, Monash University, Melbourne, Australia; Centre of Biomedical Research, Burnet Institute, Melbourne, Australia; HIV Pathogenesis Programme, University of KwaZulu-Natal, Durban, South Africa.
³ Department of Medical Microbiology, National Health Laboratory Services, Durban, South Africa.
⁴ KwaZulu-Natal Research Institute for Tuberculosis and HIV, Durban, South Africa.
⁵ Department of Infectious Diseases, Alfred Hospital, Monash University, Melbourne, Australia; Centre of Biomedical Research, Burnet Institute, Melbourne, Australia.
⁶ School of Laboratory Medicine and Medical Sciences, Nelson R. Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa; HIV Pathogenesis Programme, University of KwaZulu-Natal, Durban, South Africa; KwaZulu-Natal Research Institute for Tuberculosis and HIV, Durban, South Africa.
⁷ Department of Infectious Diseases, Nelson R. Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa.
⁸ School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia; Department of Clinical Immunology, Royal Perth Hospital and PathWest Laboratory Medicine, Perth, Australia.
⁹ Department of Medical Microbiology, National Health Laboratory Services, Durban, South Africa; School of Laboratory Medicine and Medical Sciences, Nelson R. Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa.

PMID: 25277745
DOI: 10.1016/j.diagmicrobio.2014.09.006

Abstract

We determined the susceptibility of 102 clinical isolates Cryptococcus neoformans from Durban, South Africa, to amphotericin B, fluconazole, flucytosine, and voriconazole using broth microdilution (BMD) according to the Clinical and Laboratory Standards Institute M27-A3 document and compared these results with Etest and Vitek 2(®). Essential agreement (EA) of Etest and Vitek 2(®) compared to BMD was determined. Low MICs that were below the epidemiological cutoff values of the 4 antifungal agents tested were demonstrated by all isolates. The EA of Etests for fluconazole, amphotericin, and voriconazole was 95.1%, 83.3%, and 91.2%, respectively, and for Vitek 2(®) EA for fluconazole, amphotericin, and flucytosine was 97.1%, 95.1%, and 97.1%, respectively. The Vitek 2(®) showed good agreement with BMD and is a suitable alternative. Etests demonstrated good EA for azoles only. Clinical cryptococcal isolates from Durban remain susceptible to current recommended antifungal therapy.

Keywords: Antifungal susceptibility tests; Broth microdilution; Cryptococcus neoformans; Etest; Vitek(®).

Publication types

Comparative Study

MeSH terms

AIDS-Related Opportunistic Infections / microbiology
Amphotericin B / pharmacology
Antifungal Agents / pharmacology*
Cryptococcosis / microbiology*
Cryptococcosis / virology
Cryptococcus neoformans / drug effects*
Cryptococcus neoformans / isolation & purification
Disk Diffusion Antimicrobial Tests / methods*
Fluconazole / pharmacology
Flucytosine / pharmacology
Humans
South Africa
Voriconazole / pharmacology

Substances

Antifungal Agents
Amphotericin B
Fluconazole
Flucytosine
Voriconazole