Evidence of sexual recombination among Cryptococcus neoformans serotype A isolates in sub-Saharan Africa.

The most common cause of fungal meningitis in humans, Cryptococcus neoformans serotype A, is a basidiomycetous yeast with a bipolar mating system. However, the vast majority (>99.9%) of C. neoformans serotype A isolates possess only one of the two mating type alleles (MATalpha). Isolates with the other allele (MATa) were recently discovered and proven to mate in the laboratory. It has been a mystery whether and where C. neoformans strains undergo sexual reproduction. Here, we applied population genetic approaches to demonstrate that a population of C. neoformans serotype A clinical isolates from Botswana contains an unprecedented proportion of fertile MATa isolates and exhibits evidence of both clonal expansion and recombination within two partially genetically isolated subgroups. Our findings provide evidence for sexual recombination among some populations of C. neoformans serotype A from sub-Saharan Africa, which may have a direct impact on their evolution.