Dating the Cryptococcus gattii Dispersal to the North American Pacific Northwest

Abstract

The recent emergence of the pathogenic fungus Cryptococcus gattii in the Pacific Northwest (PNW) resulted in numerous investigations into the epidemiological and enzootic impacts, as well as multiple genomic explorations of the three primary molecular subtypes of the fungus that were discovered. These studies lead to the general conclusion that the subtypes identified likely emerged out of Brazil. Here, we conducted genomic dating analyses to determine the ages of the various lineages seen in the PNW and propose hypothetical causes for the dispersal events. Bayesian evolutionary analysis strongly suggests that these independent fungal populations in the PNW are all 60 to 100 years old, providing a timing that is subsequent to the opening of the Panama Canal, which allowed for more direct shipping between Brazil and the western North American coastline, a possible driving event for these fungal translocation events.

Antimicrobial activity of Eucalyptus camaldulensis Dehn. plant extracts and essential oils: A review

“…Beside the antifungal activity of EOs and extracts of E. camaldulensis, it is worth noticing that this species, along with E. blakelyi M., E. gomphocephala A. DC, E. rudis Endl., and E. tereticornis Sm., is a reservoir of an emerging pathogenic fungus -Cryptococcus gattii. This fungus is usually related to tropic and subtropic regions, affecting the respiratory and nervous systems of the immunocompetent humans and domestic animals (Sorrell et al, 1996;Chakrabarti et al, 1997;Bielska and May, 2016;Roe et al, 2018). Similarily, C. neoformans var.…”

Cryptococcus deuterogattii VGIIa infection associated with travel to the Pacific Northwest outbreak region in an anti-GM-CSF autoantibody positive patient in the United States

“…More recent studies have suggested a South American origin of C. gattii where it is endemic, which makes the outbreak in the PNW exceptional given the temperate climate (33, 34). A 2018 study by Roe and colleagues estimated C. gattii was introduced to the PNW between 60 and 100 years ago, coinciding with the completion of the Panama Canal and the expansion of international shipping out of South America (35). However, C. deuterogattii VGIIb more closely aligns with isolates from Australia, suggesting multiple possible routes, sources, and introductions.…”

Timing the Origin ofCryptococcus gattiisensu stricto, Southeastern United States

“…The Pacific Northwest emergence has been hypothesized to be related to the opening of the Panama Canal, enabling more shipping from eastern ports of South America to the West Coast of North America ( 5 ). The estimated timing of emergence of C. gattii in the southeastern United States occurred long before industrial shipping.…”

“…We therefore applied the clonal mutation rate obtained from the prior Bayesian molecular clock analysis (using BEAST software [ 10 ]) of the Pacific Northwest C. gattii species complex, specifically for VGIIa and VGIIc (1.59 × 10 −8 SNPs/base/y). We determined the best-fitting clock and demographic model combination by implementing path and stepping stone sampling marginal-likelihood estimators as described previously ( 5 ). We implemented a general time-reversible nucleotide substitution model and an uncorrelated log-normal molecular clock with a Bayesian skyline model across 4 chains with 3 billion iterations and achieved across- and within-chain convergence.…”

“…Despite its occurrence in the Pacific Southwest, the emergence in the Pacific Northwest is thought to be quite recent. Recent work using Bayesian evolutionary analysis by sampling trees generated using BEAST software showed that the emergence of C. deuterogattii in the Pacific Northwest was a recent event, occurring within the last 60–100 years ( 5 ). …”