Abstract
Cryptococcosis, a potentially fatal mycosis in humans, is acquired via exposure to exogenous environmental sources. This study aimed to investigate the frequency, genetic diversity, and virulence of cryptococcal strains isolated from indoor dust in the Rio Negro micro-region of the Brazilian Amazon. A total of 8.9% of the studied houses were positive, recovering nine Cryptococcus neoformans VNI and 16 C. gattii VGII isolates, revealing an endemic pattern in domestic microenvironments. The International Society for Human and Animal Mycology (ISHAM) consensus multilocus sequence typing (MLST) scheme for the C. neoformans/C. gattii species complexes identified two sequence types (STs), ST93 and ST5, amongst C. neoformans isolates and six STs amongst C. gattii isolates, including the Vancouver Island Outbreak ST7 (VGIIa) and ST20 (VGIIb), the Australian ST5, and ST264, ST268 and ST445, being unique to the studied region. Virulence studies in the Galleria mellonella model showed that five C. gattii strains and one C. neoformans strain showed a similar pathogenic potential to the highly virulent Vancouver Island outbreak strain CDR265 (VGIIa). The findings of this study indicate that humans can be exposed to the agents of cryptococcosis via house dust, forming the basis for future studies to analyze the impact of early and continuous exposure to indoor dust on the development of subclinical or clinical infections.
Highlights
Cryptococcosis is a potentially fatal respiratory and neurological mycosis affecting humans and animals worldwide
In 1999, cases of cryptococcosis by C. gattii appeared in British Columbia, Canada; at first, cases appeared in the form of outbreak related strains, later becoming endemic and persisting until today
What are the means to avoid or reduce risks of infection? Humans are primarily exposed to organic indoor air inhalation, and as such, indoor dust is an important mechanism of exposure, as people spend over 86.9% of their lives in indoor environments [21]
Summary
Cryptococcosis is a potentially fatal respiratory and neurological mycosis affecting humans and animals worldwide. Cryptococcosis caused by C. neoformans is cosmopolitan, affecting mainly immunocompromised individuals, especially HIV-infected patients, with an estimation of 223,000 new cases of cryptococcal meningitis alone each year in this group of patients [2]. It is worthy of notice that endemic cryptococcosis by C. gattii shows a regional pattern in Brazil, being mostly reported in the north and northeast of the country, where it occurs usually in immunocompetent hosts, including children and young adults [4]. Until 2015, 393 cases of cryptococcosis were reported in Canada, and currently Vancouver Island has one of the highest annual incidences of C. gattii infections amongst humans and animals in the world, making this region an important temperate endemic area of cryptococcosis [5]
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