In vitro susceptibility testing in Aspergillus species: an update

Area of Science:

• Medical Mycology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Aspergillus species are leading causes of invasive mold infections in immunocompromised individuals.
• Emerging antifungal resistance in Aspergillus necessitates robust in vitro susceptibility testing.
• Established and novel antifungal agents require careful monitoring for efficacy.

Purpose of the Study:

• To review current in vitro antifungal susceptibility testing methods for Aspergillus species.
• To discuss the advantages and disadvantages of various testing methodologies.
• To highlight the clinical implications of in vitro susceptibility data for Aspergillus infections.

Main Methods:

• Review of proposed and standardized in vitro susceptibility testing procedures.
• Comparison of methods including macro- and micro-dilution, disk diffusion, and Etest.
• Examination of data from the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical Laboratory Standard Institute (CLSI).

Main Results:

• Intrinsic resistance to Amphotericin B is noted in Aspergillus terreus and Aspergillus nidulans.
• Acquired azole resistance is increasing, particularly in the Aspergillus fumigatus complex, with in vitro-in vivo correlation.
• Various testing methods exist, each with unique benefits and drawbacks regarding cost, ease of use, and data availability.

Conclusions:

• Standardized reference methods from EUCAST and CLSI offer reproducibility for Aspergillus susceptibility testing.
• Further data is needed to fully establish the clinical utility of disk diffusion for Aspergillus.
• Accurate in vitro susceptibility testing is essential for optimizing antifungal therapy in patients with invasive aspergillosis.