Molecular epidemiology of Cryptococcus neoformans variety grubii

Abstract

<p>The basidiomycete yeast<em> Cryptococcus neoformans</em> is a cause of significant morbidity and mortality in immunocompromised hosts throughout the world. The sporadic nature of the infection and the limited empirical evidence for direct human-tohuman transmission have led to the belief that infections in humans are predominantly caused by the inhalation of basidiospores from environmental sources. Therefore, analyzing the structure of environmental populations of <em>C. neoformans</em> can significantly increase our understanding of its ecology, evolution, and epidemiology. Decaying wood is a rich source of organic and inorganic compounds and is known to be a suitable ecological niche for many microorganisms, including <em>C. neoformans.</em> However, relatively little is known about the population structure of <em>C. neoformans</em> sampled from decaying wood. In this study, we analyzed samples of <em>C. neoformans</em> var. <em>grubii</em> colonizing decaying wood in tree hollows of nine tree species in five geographical locations (Delhi, Bulandshahar, Hathras, Amritsar and Arnrouli) in northwestern India. Multilocus sequence typing was conducted using five gene fragments for each of seventy-eight isolates. All isolates belonged to mating type a. Population genetic analyses identified no evidence for significant differentiation among populations belonging to either different geographic areas or different host tree species. Interestingly, despite the lack of mating type a strains in our survey, we found unambiguous evidence for recombination in our population analyses. Our results are consistent with the hypotheses of long distance dispersal and recombination in environmental populations of this species in India.</p>