Fluconazole Resistance and Heteroresistance in Cryptococcus spp.: Mechanisms and Implications

Area of Science:

• Mycology
• Antimicrobial Resistance
• Clinical Microbiology

Background:

• Minimum inhibitory concentration (MIC) is standard for antifungal susceptibility testing.
• MIC data can be insufficient for heteroresistant strains, where a resistant subpopulation emerges.
• Cryptococcus spp. heteroresistance to fluconazole involves gene overexpression on chromosome 1.

Purpose of the Study:

• Review mechanisms of antifungal resistance.
• Examine evolution of antifungal susceptibility testing methods.
• Discuss clinical implications of Cryptococcus heteroresistance to fluconazole.

Main Methods:

• Literature review of antifungal resistance mechanisms.
• Analysis of studies on Cryptococcus heteroresistance.
• Evaluation of clinical outcomes associated with heteroresistance.

Main Results:

• Chromosomal disomy in Cryptococcus spp. leads to ERG11 and AFR1 gene overexpression.
• A correlation between heteroresistance and adverse clinical outcomes is suggested but not definitively confirmed.
• Current antifungal susceptibility testing methods may not adequately detect heteroresistance.

Conclusions:

• Antifungal resistance mechanisms, particularly heteroresistance, require further investigation.
• Improved methods for antifungal susceptibility and heteroresistance testing are essential.
• More efficient therapeutic strategies are needed to combat Cryptococcus infections.