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Antifungal susceptibility testing: practical aspects and current challenges
J H Rex1, M A Pfaller, T J Walsh
1Division of Infectious Diseases, Department of Internal Medicine, Center for the Study of Emerging and Reemerging Pathogens, University of Texas Medical School, Houston, Texas 77030, USA. John.H.Rex@uth.tmc.edu
Abstract:
Development of standardized antifungal susceptibility testing methods has been the focus of intensive research for the last 15 years. Reference methods for yeasts (NCCLS M27-A) and molds (M38-P) are now available. The development of these methods provides researchers not only with standardized methods for testing but also with an understanding of the variables that affect interlaboratory reproducibility. With this knowledge, we have now moved into the phase of (i) demonstrating the clinical value (or lack thereof) of standardized methods, (ii) developing modifications to these reference methods that address specific problems, and (iii) developing reliable commercial test kits. Clinically relevant testing is now available for selected fungi and drugs: Candida spp. against fluconazole, itraconazole, flucytosine, and (perhaps) amphotericin B; Cryptococcus neoformans against (perhaps) fluconazole and amphotericin B; and Aspergillus spp. against (perhaps) itraconazole. Expanding the range of useful testing procedures is the current focus of research in this area.
Insights
Standardized antifungal susceptibility testing methods for yeasts and molds are now available. Research is advancing to demonstrate clinical value and develop reliable commercial test kits for various fungi and antifungal drugs.
Area of Science:
- Medical Mycology
- Clinical Microbiology
- Antimicrobial Resistance
Background:
- Standardized antifungal susceptibility testing (AFST) methods have been developed over the last 15 years.
- Reference methods for yeasts (NCCLS M27-A) and molds (M38-P) are now established.
- Understanding variables affecting interlaboratory reproducibility has been achieved.
Purpose of the Study:
- To demonstrate the clinical utility of standardized AFST methods.
- To develop modifications for reference methods addressing specific challenges.
- To create reliable commercial AFST kits.
Main Methods:
- Development and refinement of reference methods for AFST.
- Evaluation of interlaboratory reproducibility.
- Clinical validation of AFST results for specific fungal-drug combinations.
Main Results:
- Standardized methods for yeasts and molds are available.
- Clinically relevant testing is feasible for Candida spp., Cryptococcus neoformans, and Aspergillus spp. against select antifungal agents.
- Ongoing research focuses on expanding the scope of useful testing procedures.
Conclusions:
- Standardized AFST methods provide a foundation for clinical decision-making.
- Further research is crucial for validating and expanding AFST applications.
- The development of commercial test kits is a key objective for broader clinical adoption.