Virulence profiling of Cryptococcus gattii isolates in China: insights from a multi-center study

Cryptococcus gattii (C. gattii) is emerging as a life-threatening fungus worldwide. However, few data were available in China. In this study, 27 isolates and 32 patient information were collected from several hospitals in China, together with previously reported data (80 cases), to describe the geographic distribution of C. gattii. Molecular identification and genetic diversity analysis of the isolates were conducted using multilocus sequence typing, while the microbiological and virulence characteristics were explored through in vitro phenotypic tests and in vivo animal experiments. The findings revealed that patients infected with C. gattii were mainly immunocompetent males, with most showing symptoms of central nervous system involvement. Isolated strains were predominantly distributed in tropical and subtropical regions, with VGI genotype predominance. These strains exhibited marked genetic diversity, identifying 25 distinct sequence types (STs) among the 57 isolates (available data), including three novel STs (ST565, ST567, and ST568). In vitro assays unveiled significant differences between VGI and VGII in growth capacity at 39°C, capsule diameter, melanin production, UV resistance, and antioxidative capacity, with VGII displaying greater resilience. Integrating animal experiments and clinical prognosis showed that pathogenicity did not directly correlate with in vitro virulence phenotypes or molecular genotypes, underscoring virulence's complexity. Furthermore, histopathological analysis suggested that lung tissue damage might primarily contribute to mouse mortality, particularly with more pathogenic strains causing extensive lung tissue damage. Our study has the potential to provide valuable data for a comprehensive understanding of the microbiological characteristics of C. gattii in China.IMPORTANCEOur study indicates that the molecular typing of Cryptococcus gattii is unrelated to virulence. The integration of animal experiments and clinical prognosis demonstrated that pathogenicity did not exhibit a direct correlation with in vitro virulence phenotypes or molecular genotypes, emphasizing the intricate nature of virulence. In conclusion, our research holds the potential to provide valuable insights into understanding the microbiological attributes of C. gattii in China.