Molecular epidemiology and phylogenetic analyses of environmental and clinical isolates of Cryptococcus gattii sensu lato in Taiwan.

BACKGROUND

The rare occurrence of cryptococcosis caused by Cryptococcus gattii sensu lato (C. gattii s.l.) leads to the difficulties in studying the molecular epidemiology of this globally emerging disease.

OBJECTIVES

To establish the molecular epidemiological profile of C. gattii s.l. in Taiwan, and understand the genetic relationship between locally endemic and global isolates.

METHODS

A nationwide survey on environmental C. gattii s.l. in Taiwan was conducted from 2017 to 2019. The geographic distribution and molecular epidemiology based on multilocus sequence typing (MLST) data of the environmental isolates were compared with 18 previously collected clinical isolates. Phylogenetic analysis was performed to elucidate the genetic relationship between the global isolates and the isolates endemic to Taiwan.

RESULTS

From a total of 622 environmental samples, 104 (16.7%) were positive for C. gattii s.l.. Seven sequence types were identified among the environmental isolates. The genetic population structure showed that the environmental and clinical isolates were closely linked by sequence types and geographical locations. Phylogenetic analysis revealed the association between the C. gattii s.l. isolates in Taiwan and those from South America and South Asia. The recombination test suggested that, in Taiwan, the C. gattii sensu stricto (C. gattii s.s). isolates undergo clonal reproduction and sexual recombination, whereas C. deuterogattii isolates were clonal.

CONCLUSIONS

The molecular epidemiology of environmental C. gattii s.l. isolates is closely linked to the clinical isolates. Phylogenetic analysis of the environmental isolates provides an insight into the mechanisms underlying reproduction and dispersal of C. gattii s.l. in Taiwan.