News Scan for Jul 24, 2019

Candida auris and climate change
Australian Listeria infections

Paper suggests climate change may have aided Candida auris emergence

Could climate change have played a role in the emergence of the multidrug-resistant fungus Candida auris?

That's the hypothesis presented in a paper yesterday in mBio by researchers from Johns Hopkins Bloomberg School of Public Health, University of Texas MD Anderson Cancer Center, and Westerdijk Fungal Biodiversity Institute in the Netherlands. The experts note that the sudden, independent emergence of C auris as a human pathogen on three continents simultaneously cannot be explained solely by widespread use of antifungal drugs or recent acquisition of virulence traits, and that fungal pathogens are rare in mammals because they can't grow at human body temperature.

Hence, the researchers suggest that C auris was until recently an environmental fungus that adapted to warmer ambient temperatures caused by climate change and was able to break the mammalian thermal barrier.

To evaluate the hypothesis, they compared the thermal susceptibility of C auris to those of some of its close phylogenetic relatives, including Candida haemulonii, and found that it is capable of growing at higher temperatures than other fungal species. They present a scenario in which C auris emerged in wetlands and gained tolerance for warmer temperatures, adapted to an intermediate host—birds—was transplanted by birds to areas where humans and birds are in contact, and then acquired genetic traits that enabled transmission to humans. They say the fact that C auris typically grows on cooler skin sites, rather than the warmer human gut, supports the notion that it was, until recently, an environmental pathogen.

Although they acknowledge that climate change does not explain the whole story of how C auris emerged, the authors warn that a hotter climate could give rise to new fungal infections.

"Whether C. auris is the first example of new pathogenic fungi emerging from climate change or whether its origin into the realm of human-pathogenic fungi followed a different trajectory, its emanation stokes worries that humanity may face new diseases from fungal adaptation to hotter climates," they write.
Jul 23 mBio paper


Salmon suspected in Australian Listeria cases, including 2 deaths

Australia's Department of Health and three of the country's states are investigating three Listeria monocytogenes cases with smoked salmon as the likely source.

A statement today from the chief medical officer said the patients are from Victoria, Queensland, and New South Wales. Two people died from their infections. All three of the people are over age 70 and had significant underlying health conditions. According to an Australia Broadcasting Corporation (ABC) News report, the salmon probably came from Tasmania, which produces most of Australia's salmon.

"This is a timely reminder for people to ensure that food is handled, prepared, and stored safely, and that those most at-risk of listeriosis avoid certain foods," Brendan Murphy, Australia's chief medical officer, said in the statement.

Symptoms, which are often flulike, can begin within a few days, but sometimes they begin weeks after eating contaminated food. Certain groups are at increased risk of Listeria infection, including pregnant women, newborns, seniors, and those with weakened immune systems.
Jul 24 Australian government statement
Jul 24 ABC News story

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