Dynamic and heterogeneous mutations to fluconazole resistance in Cryptococcus neoformans

Area of Science:

• Mycology
• Antimicrobial Resistance
• Medical Mycology

Background:

• Cryptococcus neoformans is a human pathogen causing serious infections.
• Fluconazole is a primary antifungal treatment for C. neoformans.
• Emerging fluconazole resistance necessitates understanding resistance mechanisms.

Purpose of the Study:

• To investigate in vitro mutation patterns leading to fluconazole resistance in Cryptococcus neoformans.
• To determine the mutation rates of fluconazole resistance in various C. neoformans strains.
• To explore potential correlations between baseline fluconazole MIC and mutation rates.

Main Methods:

• Determined Minimum Inhibitory Concentrations (MICs) of fluconazole for 21 C. neoformans strains.
• Cultured six independent cultures per strain on fluconazole-containing agar to assess mutation rates.
• Subcultured and re-tested MICs for putative fluconazole-resistant mutants.

Main Results:

• Significant heterogeneity in mutation rates for fluconazole resistance was observed across the 21 strains.
• Mutant MICs varied widely, from original strain MICs up to 64 microg/ml.
• No significant correlation was found between a strain's original fluconazole MIC and its mutation rate.

Conclusions:

• Fluconazole resistance in C. neoformans arises from dynamic and heterogeneous mutational processes.
• The development of resistance is complex and not solely dependent on initial susceptibility levels.
• Further research into the genetic underpinnings of C. neoformans fluconazole resistance is warranted.