In Vitro Susceptibility of Fusarium to Isavuconazole

Area of Science:

• Mycology
• Antimicrobial Susceptibility Testing
• Medical Mycology

Background:

• Fusarium species are emerging fungal pathogens causing invasive infections.
• Isavuconazole is a broad-spectrum triazole antifungal agent.
• Evaluating antifungal susceptibility is crucial for guiding clinical treatment decisions.

Purpose of the Study:

• To determine the in vitro susceptibility of clinical Fusarium isolates to isavuconazole.
• To compare the performance of the gradient concentration strip (GCS) technique with the EUCAST broth microdilution method.

Main Methods:

• Seventy-five clinical Fusarium isolates were identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS).
• In vitro susceptibility testing was performed using the EUCAST broth microdilution method and the gradient concentration strip (GCS) technique.
• Minimum Inhibitory Concentrations (MICs) were determined for isavuconazole.

Main Results:

• Isavuconazole demonstrated limited in vitro activity against Fusarium isolates, with a MIC50 of >16 μg/ml.
• No significant differences in susceptibility were observed among different Fusarium species complexes.
• High categorical agreement (97.4%–100%) was found between the GCS and EUCAST methods.

Conclusions:

• Isavuconazole exhibits restricted antifungal activity against the tested Fusarium clinical isolates.
• The gradient concentration strip (GCS) technique is a valuable and accurate alternative for Fusarium susceptibility testing.
• Further research may be needed to explore alternative treatment options for Fusarium infections.