Related Experiment Video
Updated: Aug 3, 2026
Automated Measurement of Cryptococcal Species Polysaccharide Capsule and Cell Body
Published on: January 11, 2018
Comparative analyses of clinical and environmental populations of Cryptococcus neoformans in Botswana
Yuan Chen1,2, Anastasia P Litvintseva2, Aubrey E Frazzitta1
1Division of Infectious Diseases, Department of Medicine, Duke University Medical Center, 163 Hanes House, Trent Drive, Durham, NC, 27710, USA.
Abstract:
Cryptococcus neoformans var. grubii (Cng) is the most common cause of fungal meningitis, and its prevalence is highest in sub-Saharan Africa. Patients become infected by inhaling airborne spores or desiccated yeast cells from the environment, where the fungus thrives in avian droppings, trees and soil. To investigate the prevalence and population structure of Cng in southern Africa, we analysed isolates from 77 environmental samples and 64 patients. We detected significant genetic diversity among isolates and strong evidence of geographic structure at the local level. High proportions of isolates with the rare MATa allele were observed in both clinical and environmental isolates; however, the mating-type alleles were unevenly distributed among different subpopulations. Nearly equal proportions of the MATa and MATα mating types were observed among all clinical isolates and in one environmental subpopulation from the eastern part of Botswana. As previously reported, there was evidence of both clonality and recombination in different geographic areas. These results provide a foundation for subsequent genomewide association studies to identify genes and genotypes linked to pathogenicity in humans.
Insights
Cryptococcus neoformans var. grubii causes fungal meningitis, especially in sub-Saharan Africa. This study reveals significant genetic diversity and geographic structure in southern African Cryptococcus neoformans var. grubii populations.
Area of Science:
- Medical Mycology
- Population Genetics
- Infectious Diseases
Background:
- Cryptococcus neoformans var. grubii (Cng) is a leading cause of fungal meningitis, particularly in sub-Saharan Africa.
- Infection occurs via inhalation of airborne Cng spores or yeast cells from environmental sources like avian droppings, trees, and soil.
Purpose of the Study:
- To investigate the prevalence and population structure of Cng in southern Africa.
- To analyze genetic diversity and geographic distribution of Cng isolates from clinical and environmental sources.
Main Methods:
- Analysis of 77 environmental samples and 64 patient isolates of Cng from southern Africa.
- Assessment of genetic diversity, geographic structure, and mating-type allele distribution (MATa and MATα).
- Evaluation of clonality and recombination patterns within different geographic areas.
Main Results:
- Significant genetic diversity and local-level geographic structure were detected among Cng isolates.
- High proportions of the rare MATa allele were found in both clinical and environmental isolates.
- Mating-type alleles showed uneven distribution, with nearly equal MATa and MATα proportions in clinical isolates and one Botswana environmental subpopulation.
Conclusions:
- Cng populations in southern Africa exhibit considerable genetic diversity and geographic structuring.
- The distribution of mating-type alleles suggests complex population dynamics.
- These findings lay the groundwork for future genomewide association studies to identify Cng pathogenicity factors.
