[Controversies in the standardization of susceptibility testing on yeasts to azole antimycotics]

Area of Science:

• Medical Mycology
• Antimicrobial Susceptibility Testing
• Pharmaceutical Chemistry

Background:

• Therapeutic azoles exhibit diverse physical-chemical properties, impacting their antifungal efficacy and testing methodologies.
• Fluconazole, being hydrophilic, allows for straightforward susceptibility testing.
• Itraconazole's extreme hydrophobicity necessitates different testing conditions compared to fluconazole.

Purpose of the Study:

• To highlight the necessity of tailored susceptibility testing procedures for azole antifungals.
• To address the challenges posed by the varying hydrophilicity/hydrophobicity of azoles in testing.
• To advocate for the standardization of antifungal susceptibility testing across all azoles.

Main Methods:

• Review of current azole antifungal properties and their implications for in vitro testing.
• Analysis of existing susceptibility testing guidelines (e.g., NCCLS) in the context of azole variability.
• Identification of discrepancies in testing procedures for different azoles.

Main Results:

• Fluconazole susceptibility testing is relatively simple due to its hydrophilic nature.
• Itraconazole requires distinct testing conditions owing to its high hydrophobicity.
• Current recommendations may not adequately account for these critical differences.

Conclusions:

• Adequate testing procedures must be chosen based on the specific physical-chemical properties of each therapeutic azole.
• Standardization of susceptibility testing for all azoles is essential for reliable clinical and research outcomes.
• Further refinement of guidelines is needed to accommodate the diverse characteristics of azole antifungals.