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Published on: October 20, 2010
Disk diffusion-based methods for determining Candida parapsilosis susceptibility to anidulafungin
Zekaver Odabasi1, Victor Paetznick, Beth P Goldstein
1Division of Infectious Diseases, University of Texas-Houston Medical School, Houston, Texas 77030, USA. zekaver.odabasi@uth.tmc.edu
Abstract:
Zone diameters for anidulafungin by disk diffusion for 139 isolates of C. parapsilosis were compared with MICs by NCCLS M27-A2 broth microdilution. The comparison was poor unless the disks were prepared by dissolving anidulafungin in 1% dimethyl sulfoxide plus 0.1% Tween 80 and testing on Mueller-Hinton agar flooded with glucose and methylene blue.
Insights
Disk diffusion testing for anidulafungin against C. parapsilosis requires specific disk preparation. Optimized methods improve correlation between zone diameters and minimum inhibitory concentrations (MICs).
Area of Science:
- Mycology
- Antifungal Susceptibility Testing
- Clinical Microbiology
Background:
- Candida parapsilosis is a significant fungal pathogen.
- Accurate antifungal susceptibility testing is crucial for effective treatment.
- Disk diffusion is a common method for antimicrobial susceptibility testing.
Purpose of the Study:
- To evaluate the disk diffusion method for anidulafungin against Candida parapsilosis.
- To determine optimal conditions for disk diffusion testing of anidulafungin.
- To compare disk diffusion results with broth microdilution minimum inhibitory concentrations (MICs).
Main Methods:
- 139 isolates of Candida parapsilosis were tested.
- Disk diffusion assays were performed using anidulafungin disks.
- MICs were determined using NCCLS M27-A2 broth microdilution.
- Disk preparation involved dissolving anidulafungin in dimethyl sulfoxide and Tween 80.
- Testing was conducted on Mueller-Hinton agar supplemented with glucose and methylene blue.
Main Results:
- A poor correlation was observed between zone diameters and MICs with standard disk preparation.
- Optimized disk preparation (1% dimethyl sulfoxide, 0.1% Tween 80) significantly improved the correlation.
- Testing on supplemented Mueller-Hinton agar enhanced the reliability of the disk diffusion method.
Conclusions:
- Disk diffusion can be a reliable method for anidulafungin susceptibility testing of C. parapsilosis with optimized conditions.
- Specific disk formulation and agar supplementation are critical for accurate results.
- This optimized method facilitates rapid susceptibility assessment in clinical settings.
