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A 96 Well Microtiter Plate-based Method for Monitoring Formation and Antifungal Susceptibility Testing of Candida albicans Biofilms
Published on: October 21, 2010
Development of anidulafungin for disk diffusion susceptibility testing against Candida spp
Ronald N Jones1, Jeffrey T Kirby, Shawn A Messer
1JMI Laboratories, North Liberty, IA 52317, USA. ronald-jones@jmilabs.com
Diagnostic Microbiology and Infectious Disease
|March 23, 2007
Summary
A standardized disk diffusion method was developed to test anidulafungin susceptibility in Candida species. The optimal 2-microg disk formulation showed good correlation with MIC results for accurate yeast susceptibility testing.
Area of Science:
- Medical Microbiology
- Antifungal Susceptibility Testing
- Clinical Mycology
Background:
- The Clinical and Laboratory Standards Institute (CLSI) has standardized disk diffusion (DD) methods for azole antifungal susceptibility testing in Candida species.
- Anidulafungin is a new echinocandin antifungal agent with a growing clinical role.
- Standardized methods for testing anidulafungin susceptibility using disk diffusion are needed.
Purpose of the Study:
- To develop and standardize a disk diffusion (DD) method for determining anidulafungin susceptibility in clinical isolates of Candida species.
- To evaluate the correlation between the proposed DD method and reference broth microdilution Minimum Inhibitory Concentration (MIC) testing.
- To determine the optimal anidulafungin disk concentration and formulation for reliable susceptibility testing.
Main Methods:
- Seventy-five strains of Candida species were tested using a disk diffusion assay.
- Candidate anidulafungin disk concentrations (1, 2, 5, and 10 microg) were evaluated with varying concentrations of dimethyl sulfoxide (DMSO) and polysorbate 80 (P-80).
- Results were compared against reference Minimum Inhibitory Concentration (MIC) values.
Main Results:
- A 2-microg anidulafungin disk formulation containing 1% DMSO and 0.1% P-80 demonstrated acceptable correlation (r = 0.84-0.85) with reference MIC results.
- This optimized disk formulation was effective for testing all tested Candida species.
- The method achieved good separation between less susceptible Candida parapsilosis and other more susceptible yeast species, with a potential breakpoint near a zone diameter of >= 15 mm.
Conclusions:
- A disk diffusion method using 2-microg anidulafungin disks (with 1% DMSO and 0.1% P-80) is a reliable and standardized approach for testing Candida susceptibility.
- This method provides accurate and reproducible results, aiding in the clinical management of Candida infections.
- The developed DD method facilitates efficient antifungal susceptibility testing for anidulafungin in clinical laboratories.
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