Heteroresistance to Itraconazole Alters the Morphology and Increases the Virulence of Cryptococcus gattii.

Abstract

Cryptococcus gattii is the main etiological agent of cryptococcosis in immunocompetent individuals. The triazole drug itraconazole is one of the antifungals used to treat patients with cryptococcosis. Heteroresistance is an adaptive mechanism to counteract the stress of increasing drug concentrations, and it can enhance the ability of a microorganism to survive under antifungal pressure. In this study, we evaluated the ability of 11 C. gattii strains to develop itraconazole heteroresistance. Heteroresistant clones were analyzed for drug susceptibility, alterations in cell diameter, capsule properties, and virulence in a murine model. Heteroresistance to itraconazole was intrinsic in all of the strains analyzed, reduced both the capsule size and the cell diameter, induced molecular heterogeneity at the chromosomal level, changed the negatively charged cells, reduced ergosterol content, and improved the antioxidant system. A positive correlation between surface/volume ratio of original cells and the level of heteroresistance to itraconazole (LHI) was observed in addition to a negative correlation between capsule size of heteroresistant clones and LHI. Moreover, heteroresistance to itraconazole increased the engulfment of C. gattii by macrophages and augmented fungal proliferation inside these cells, which probably accounted for the reduced survival of the mice infected with the heteroresistant clones and the higher fungal burden in lungs and brain. Our results indicate that heteroresistance to itraconazole is intrinsic and increases the virulence of C. gattii. This phenomenon may represent an additional mechanism that contributes to relapses of cryptococcosis in patients during itraconazole therapy.

• Authors: Gabriella Freitas Ferreira, Julliana Ribeiro Alves Santos, Marliete Carvalho da Costa, Rodrigo Assunção de Holanda, Ângelo Márcio Leite Denadai, Gustavo José Cota de Freitas, Áquila Rodrigues Costa Santos, Priscila Batista Tavares, Tatiane Alves Paixão, Daniel Assis Santos
• Journal: Antimicrobial agents and chemotherapy (Antimicrob Agents Chemother) Vol. 59 Issue 8 Pg. 4600-9 (Aug 2015) ISSN: 1098-6596 [Electronic] United States
• PMID: 26014951 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Chemical References

• Antifungal Agents
• Itraconazole

Topics

• Animals
• Antifungal Agents (therapeutic use)
• Brain (microbiology)
• Cell Proliferation (drug effects)
• Cryptococcosis (drug therapy, microbiology)
• Cryptococcus gattii (drug effects, physiology)
• Drug Resistance, Fungal (drug effects, physiology)
• Itraconazole (pharmacology)
• Lung (microbiology)
• Macrophages (microbiology)
• Male
• Mice
• Mice, Inbred C57BL
• Microbial Sensitivity Tests (methods)
• Virulence (drug effects, physiology)