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Fluconazole disk diffusion susceptibility testing of Candida species
W R Kirkpatrick1, T M Turner, A W Fothergill
1Departments of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284, USA.
Journal of Clinical Microbiology
|October 17, 1998
Summary
A simple disk diffusion method can effectively detect fluconazole-resistant yeasts. This screening tool accurately identifies resistant Candida species in clinical microbiology labs, aiding in antifungal treatment decisions.
Area of Science:
- Medical Mycology
- Antimicrobial Resistance
- Clinical Microbiology
Background:
- Fluconazole is a key antifungal medication.
- Emerging resistance in yeasts like Candida poses a clinical challenge.
- Accurate and rapid detection of resistance is crucial for effective patient management.
Purpose of the Study:
- To evaluate a simple disk diffusion method for detecting fluconazole resistance in clinical yeast isolates.
- To determine the efficacy of different fluconazole disk concentrations (25- and 50-microgram) for identifying resistant strains.
Main Methods:
- Disk diffusion assay performed on RPMI-glucose agar using 40 clinical Candida sp. isolates.
- Testing with both 25-microgram and 50-microgram fluconazole disks.
- Comparison of disk diffusion results with established Minimum Inhibitory Concentration (MIC) values.
Main Results:
- Zones of inhibition correlated well with MICs.
- 25-microgram disks with zones >=20 mm at 24h identified susceptible isolates (MIC <=8 µg/ml).
- 50-microgram disks with zones >=27 mm also accurately identified susceptible isolates, and both disk types correctly identified all resistant isolates (MIC >8 µg/ml).
Conclusions:
- Disk diffusion offers a straightforward and reliable method for screening fluconazole resistance in yeasts.
- This technique can be a valuable addition to clinical microbiology laboratories for rapid identification of resistant Candida species.
- Facilitates timely adjustments in antifungal therapy, improving patient outcomes.