Abstract
To gain a more detailed picture of cryptococcosis in Thailand, a retrospective study of 498 C. neoformans and C. gattii isolates has been conducted. Among these, 386, 83 and 29 strains were from clinical, environmental and veterinary sources, respectively. A total of 485 C. neoformans and 13 C. gattii strains were studied. The majority of the strains (68.9%) were isolated from males (mean age of 37.97 years), 88.5% of C. neoformans and only 37.5% of C. gattii strains were from HIV patients. URA5-RFLP and/or M13 PCR-fingerprinting analysis revealed that the majority of the isolates were C. neoformans molecular type VNI regardless of their sources (94.8%; 94.6% of the clinical, 98.8% of the environmental and 86.2% of the veterinary isolates). In addition, the molecular types VNII (2.4%; 66.7% of the clinical and 33.3% of the veterinary isolates), VNIV (0.2%; 100% environmental isolate), VGI (0.2%; 100% clinical isolate) and VGII (2.4%; 100% clinical isolates) were found less frequently. Multilocus Sequence Type (MLST) analysis using the ISHAM consensus MLST scheme for the C. neoformans/C. gattii species complex identified a total of 20 sequence types (ST) in Thailand combining current and previous data. The Thai isolates are an integrated part of the global cryptococcal population genetic structure, with ST30 for C. gattii and ST82, ST83, ST137, ST141, ST172 and ST173 for C. neoformans being unique to Thailand. Most of the C. gattii isolates were ST7 = VGIIb, which is identical to the less virulent minor Vancouver island outbreak genotype, indicating Thailand as a stepping stone in the global spread of this outbreak strain. The current study revealed a greater genetic diversity and a wider range of major molecular types being present amongst Thai cryptococcal isolates than previously reported.
Highlights
The members of the Cryptococcus neoformans/C. gattii species complex are the causative agent of cryptococcosis, which is a systemic mycosis, in a wide range of animals and humans [1,2,3,4]
C. gattii was until recently belonged to the VNI molecular type, with only one isolate being found to be VNII [33]
Three standard molecular typing methods were performed on 498 cryptococcal strains isolated from humans, the environment and animals in Thailand
Summary
The members of the Cryptococcus neoformans/C. gattii species complex are the causative agent of cryptococcosis, which is a systemic mycosis, in a wide range of animals and humans [1,2,3,4].Inhalation of infectious propagules (basidiospores or blastoconidia) are proposed to be the source of the infection [1]. The members of the Cryptococcus neoformans/C. gattii species complex are the causative agent of cryptococcosis, which is a systemic mycosis, in a wide range of animals and humans [1,2,3,4]. C. neoformans comprises two varieties and three serotypes: C. neoformans var. Neoformans (serotype D) and a hybrid (serotype AD), whereas C. gattii comprises two serotypes, B and C [1,3]. C. neoformans has been associated worldwide with soil enriched with pigeon excreta and decaying wood [1,5,6]. C. gattii was until recently belonged to the VNI molecular type, with only one isolate being found to be VNII [33]. The genetic diversity of Thai isolates is expected to be more diverse since C. neoformans var
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