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  • Writer's pictureP.K. Peterson

Mounting Threat of Fungal Pandemics: the Case of Candida auris

Candida auris is the first fungal pathogen considered a global health threat."

Kamran Lankarani, M.D., professor of medicine, Shiraz University of Medical Sciences


“For healthcare systems in the Pacific Northwest, the recent outbreaks of Candida auris (C. auris) serve as a wake up call. . . . This new threat also represents a bellwether in health circles due to the clear link between the spread of C. auris and climate change.”

Stefan Wheat, MD and Thomas Kuczmarski, MD, University of Washington, Seattle

 



Candida auris is a multidrug-resistant fungal pathogen. Since it first emerged in Japan in 2009, C. auris has spread to many hospitals throughout the world, killing as many as one in three people who get it. In late January 2024, Seattle health officials confirmed the fourth case of C. auris in a local hospital.



In their article, “There’s a New Fungus in Town and It Won’t Be the Last—The arrival of C. auris in Washington is a harbinger of health systems addled by climate change,” University of Washington’s Drs. Stefan Wheat and Thomas Kuczmarski warn that C. auris’s “arrival to Washington state is not just a local issue; it is a global concern.” (See March 22, 2024 Medpage Today.) In this week’s post, I provide an update on this fungal enemy. (I first discussed this topic in my August 16, 2019, Germ Gems post  “Some Like It Hot: The Alarming Rise of Candida Auris.”)


The fungal world (a recap). Like all eukaryotes, including us, the cells of fungi possess a nucleus. This feature distinguishes them from other members of the microbial world (bacteria, archaea, protists, and viruses).


Fungi come in three forms: yeasts, molds, and non-microscopic mushrooms. It’s estimated there are more than 6 million fungal species in the world but only a meager 300 are known to be pathogenic to humans.


C. auris, like other Candida species, is a yeast. C. auris was first described in 2009 after it was isolated from the ear canal of a 70-year-old Japanese woman. (Its name comes from the Latin word for ear—auris.) It next was seen in 2011 in South Korea where it sickened three patients. From there, it spread rapidly throughout Asia and Europe, making its debut in the U.S. in  New York in 2013.



Like most of its Candida cousins, C. auris predominantly strikes people with a compromised immune system. This explains why it mainly haunts hospital intensive care units where such patients are to be found. According to a 2017-2022 survey by the National Institutes of Health, 192 C. auris-associated hospitalizations were recorded in the U.S., including 38 (20%) bloodstream infections, with an estimated overall mortality of 34%.


Clinical features. The most common symptoms and signs of a C. auris infection are fever, chills, sweats, and low blood pressure. Infections have occurred in patients of all ages, from preterm infants to the elderly. And C. auris became a regular co-pathogen in patients with the viral infection COVID-19. (See Iran Medical Journal, June 2022, Candida auris: outbreak fungal pathogen in COVID-19 pandemic: a systematic review and meta-analysis.)


Treatment. C. auris has attracted increased clinical attention because of a striking feature which greatly complicates treatment: it is resistant to multiple drugs. In vitro, more than 90% of isolates are resistant to fluconazole, a widely used antifungal agent. Even more worrisome, 13% to 35% of isolates are resistant to amphotericin B, a usually reliable, potent antifungal. But on a positive note, most isolates are susceptible to echinocandins—a class of antifungal drugs that has been termed “the penicillin of antifungals.”


Prevention. C. auris’s main route of transmission is by contaminated hands—sadly, often those of healthcare personnel. Therefore, rigorous handwashing is the first line of defense against acquiring this pathogen. No human vaccine against C. auris exists.


Connection to climate change. In the clinical microbiology laboratory, one of the clues that a fungal isolate is C. auris is that it grows at elevated temperatures. In a 2019 article, Dr. Arturo Casadevall and his colleagues at Johns Hopkins School of Public Health took note of this trait; they were the first to hypothesize that the reason several clades of C. auris emerged from different continents at about the same time is because of global warming. They predicted, “What this study suggests is this is the beginning of fungi adapting to higher temperatures, and we are going to have more and more problems as the century goes on. . . Global warming will lead to selection of fungal lineages that are more thermal tolerant.”



Dr. Casadevall’s 2019 prediction is increasingly borne out by recent reports on the impact of climate change on infectious diseases (See ABC Audio’s March 15, 2024 podcast, Start Here, “The growing threat of fungal infections” and the March 20, 2024 Journal of the American Medical Association Insights, “Infectious Diseases in a Changing Climate.”).


Because of ongoing global warming, we can now add a hand-borne fungus, C. auris, to the growing list of airborne fungi (Coccidioides immitis, Blastomyces dermatididis, and Histoplasm capsulatum), on top of vector-borne and waterborne viruses, parasites, and bacteria that welcome a warming planet. As Drs. Wheat and Kuczarski warn: “While the full impact of [C. auris’s] arrival in Seattle in not yet fully understood, one thing is certain: it will not be the last time we contend with the emergence of a new infectious threat linked to climate change.”

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Main Page images courtesy of Shuxian Hu, MD. Dr. Hu is a scientist in the Neuroimmunology Research Laboratory at the University of Minnesota.

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