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Antifungal susceptibility testing of yeasts: a brief overview
D J Sheehan1, A Espinel-Ingroff, L S Moore
1Roerig Division, Pfizer Inc., New York, New York 10017-5755.
Abstract:
Antifungal susceptibility testing of yeasts has lacked reproducibility because of the absence of universally accepted guidelines. The major sources of variation in susceptibility testing have been attributed to the choice of medium and pH, inoculum preparation and size, incubation temperature and time, and end-point criteria. These parameters have been addressed by the National Committee for Clinical Laboratory Standards (NCCLS) Subcommittee on Antifungal Susceptibility Testing, and proposed guidelines have recently been published. Although major advances in antifungal susceptibility testing have been achieved, particularly through the efforts of the NCCLS subcommittee, the results of studies to date do not support a correlation between the results of in vitro susceptibility testing and in vivo response. Routine antifungal susceptibility testing of yeasts should therefore be discouraged until the methodology is standardized such that it predicts clinical outcome.
Insights
Reproducibility in antifungal susceptibility testing for yeasts is improving with new guidelines, but results do not yet predict patient outcomes. Routine testing is discouraged until standardized methods correlate with clinical efficacy.
Area of Science:
- Medical Mycology
- Clinical Microbiology
Background:
- Antifungal susceptibility testing (AST) for yeasts lacks reproducibility due to inconsistent methodologies.
- Variability stems from differences in media, pH, inoculum preparation, incubation conditions, and interpretation criteria.
Purpose of the Study:
- To address the lack of standardization in yeast antifungal susceptibility testing.
- To evaluate the current state of antifungal susceptibility testing guidelines and their clinical relevance.
Main Methods:
- Review of factors contributing to variability in yeast AST.
- Consideration of proposed guidelines from the National Committee for Clinical Laboratory Standards (NCCLS) Subcommittee on Antifungal Susceptibility Testing.
Main Results:
- Significant advances in standardizing AST methodology have been made.
- Current in vitro susceptibility testing results do not reliably correlate with in vivo clinical responses.
Conclusions:
- Routine antifungal susceptibility testing for yeasts is not recommended at this time.
- Standardization efforts must ensure that AST methods accurately predict clinical outcomes before routine implementation.