Deciphering Candida auris Paradoxical Growth Effect (Eagle Effect) in Response to Echinocandins

Area of Science:

• Mycology
• Antifungal Drug Discovery
• Clinical Microbiology

Background:

• The paradoxical growth effect (PGE), or Eagle effect, is an in vitro phenomenon in antifungal susceptibility testing (AFST).
• PGE involves fungal isolates growing at echinocandin concentrations above the minimal inhibitory concentration (MIC), despite susceptibility at lower concentrations.
• This effect complicates resistance determination, particularly for emerging pathogens like Candida auris with undefined susceptibility breakpoints.

Purpose of the Study:

• To describe a protocol for differentiating echinocandin resistance from paradoxical growth in Candida auris isolates.
• To aid in accurate antifungal susceptibility testing for challenging fungal pathogens.

Main Methods:

• Development and description of a specific laboratory protocol.
• Application of the protocol to Candida auris isolates.
• Comparative analysis of growth patterns at varying echinocandin concentrations.

Main Results:

• The protocol effectively distinguishes between true echinocandin resistance and the paradoxical growth effect in Candida auris.
• Provides a clear method for classifying isolates that exhibit PGE.

Conclusions:

• Accurate identification of echinocandin resistance versus PGE is crucial for effective treatment of Candida auris infections.
• The described protocol offers a reliable solution for this diagnostic challenge in clinical settings.