Population diversity and virulence characteristics of < i > Cryptococcus neoformans/C < /i > . < i > gattii < /i > species complexes isolated during the pre-HIV-pandemic era

by Sujiraphong Pharkjaksu, Kyung J. Kwon-Chung, John E. Bennett, Popchai Ngamskulrungroj Cryptococcosis has become a major global health problem since the advent of the HIV pandemic in 1980s. Although its molecular epidemiology is well-defined, using isolates recovered since then, no pre-HIV-pandemic era epidemiological data exist. We conducted a molecular epidemiological study using 228 isolates of theC.neoformans/C.gattii species complexes isolated before 1975. Genotypes were determined byURA5 restriction fragment length polymorphism analysis and multi-locus sequence typing. Population genetics were defined by nucleotide diversity measurements, neutrality tests, and recombination analysis. Growth at 37 °C, melanin synthesis, capsule production, and urease activity as virulence factors were quantified. The pre-HIV-pandemic isolates consisted of 186 (81.5%) clinical, 35 (15.4%) environmental, and 7 (3.1%) veterinary isolates. Of those, 204 (89.5%) belonged toC.neoformans VNI (64.0%), VNII (14.9%) and VNIV (10.5%) while 24 (10.5%) belonged toC.gattii VGIII (7.5%), VGI (2.6%) and VGII (0.5%). Among the 47 sequence types (STs) identified, one of VNII and 8 of VNIV were novel. ST5/VNI (23.0%) inC.neoformans and ST75/VGIII (25.0%) inC.gattii were the most common STs in both species complexes. AmongC.neoformans, VNIV had the highest genetic diversity (Hd = 0.926) and the minimum recombination events (Rm = 10), and clinical isolates had less genetic diversity (Hd = 0.866) than env...
Source: PLoS Neglected Tropical Diseases - Category: Tropical Medicine Authors: Source Type: research