The Molecular Epidemiology and Ecology of Cryptococcal Fungi in the Environment, Air and in Clinical Cases

Airborne fungal infections present an increasing risk to plant, animal and human health. Warmer and wetter climates provide ideal growth conditions while overuse of fungicides in agriculture and healthcare has created increased pressure for development of fungicide resistance. Cryptococcus fungi are a diverse genus of single-celled yeasts of which two species complexes, Cryptococcus gattii and Cryptococcus neoformans, can cause a highly fatal meningitis when cells or spores are inhaled by a susceptible individual. Genomic sequencing of these fungi has revealed high diversity of lineages, as well as relationships between genotype with ecology, virulence and clinical outcome. However, it remains largely unknown when and where people become infected and why some lineages cause disease more frequently than others. This is in part due to the limited availability of sequences from the environment including a sparsity of isolates from the air. Many studies have attempted air sampling using agar plates and have had zero-to-poor isolation rates. A recent study in Canada used a higher quality air sampler and managed to isolate C. gattii in the air as well as relate it to forest-cutting activities[1]. My study has already isolated environmental Cryptococcus samples from trees and soil in Zambia, a country known to have high diversity and clinical burden of Cryptococcus, and will next attempt to isolate Cryptococcus from the air. Use of a dry air sampler will enable shotgun sequencing to be conducted that may have greater sensitivity in identifying any fungi. This will hopefully increase what we know about risk of exposure as well as act as proof-of-concept for better isolation of the fungus in future studies.

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