Search

Summary: Background: The sister yeast species Cryptococcus neoformans (serotype A) and Cryptococcus deneoformans (serotype D) are causative agents of deadly cryptococcosis and fungal meningoencephalitis. These haploid yeasts can hybridise in nature, giving rise to AD hybrids that are predominantly diploid or aneuploid. Despite their increasing prevalence in clinical settings, much remains unknown about the allelic distribution patterns in AD hybrid strains. Objectives: This study aims to characterise allele distributions in AD hybrids derived from the same basidium as well as from multiple basidia in a laboratory‐derived C neoformans × C deneoformans hybrid cross. Methods: We dissected a total of 1625 basidiospores from 31 basidia. The 297 basidiospores that successfully germinated were genotyped by molecular characterisation of 33 markers using PCR‐RFLP, with at least two markers on each of the 14 chromosomes in the genome. Results: Of the 297 strains, 294 contained at least one heterozygous locus, with a mean heterozygosity of ~30% per strain. Most hybrid genomes and chromosomes displayed significantly distorted allele distributions, with offspring originating from the same basidium tended to have alleles at different loci from the same parent. More basidia were skewed in favour of C deneoformans alleles, the mitochondria‐donor parent, than the C neoformans alleles. Conclusions: The divergence between C neoformans and C deneoformans genomes has likely created co‐adapted allelic combinations, with their co‐segregation in hybrid offspring imparting a significant fitness benefit. However, the diversity of genotypes recovered here in a single hybridisation event indicates the enormous capacity of AD hybrids for adaptation and diversification. [ABSTRACT FROM AUTHOR]

Cryptococcosis is a life‐threatening mycosis primarily occurring in adult patients particularly those with immunosuppression such as HIV infection/AIDS. The number of reported cases of paediatric cryptococcosis has increased in the last decade around the world, including China. However, current information on the characteristics of cryptococcosis in children, particularly the genotypic diversity and antifungal susceptibility of the isolates, is limited. In the present study, a total of 25 paediatric isolates of Cryptococcus neoformans were genotyped using the ISHAM‐MLST scheme. In vitro susceptibility to antifungal agents of the 22 isolates was tested using the CLSI M27‐A3 method. Our analyses revealed that the genotypic diversity of C. neoformans isolates from Chinese paediatric patients was low, with ST 5 (80%) and ST 31 (12%) being the two major sequence types. Reduced susceptibility to fluconazole (FLU), 5‐flucytosine (5‐FC) and itraconazole (ITR) was observed among C. neoformans isolates from Chinese paediatric patients, particularly among the ST5 isolates, which was similar to observations made on C. neoformans isolates from Chinese adult patients. In addition, the majority of isolates (3/4, 75%) obtained from deceased patients showed decreased antifungal susceptibility, which indicates that further monitoring of antifungal susceptibility of Cryptococcus isolates is warranted in management of paediatric cryptococcosis. [ABSTRACT FROM AUTHOR]