A terrifying super-yeast that kills people in hospitals could also survive well outside of them, according to a new study on Tuesday.day. For the first time, researchers say, they have discovered the versatile ingredients of the fungus Candida auris in a natural environment, in the remote wetlands of India. The findings suggest that these types of environments may be home to the yeast, while also providing evidence that global warming due to climate change has recently made the fungus dangerous to humans, as some scientists theorize.
C. auris was first discovered in 2009 by doctors in Japan, who isolated it from the ear infection of a patient (the first known cases date from the mid-nineties). Since then, the yeast has been found in more than a dozen countries, including the US. It can cause life-threatening infections, especially in patients who are already debilitated in the hospital. But what makes the yeast particularly frightening is that it is often resistant to multiple antifungal drugs, making it difficult to treat and often fatal. The fungus is also a survivor outside the human body, so once it is established somewhere, it is incredibly difficult to remove it from the environment. If that was not enough, C. auris can not be easily identified by conventional tests, which can delay care and increase the risk of death.
Only about 1,600 cases of the yeast have been identified in the US since 2009, but it is considered one of the most serious emerging germ threats we face today. This threat has the importance of understanding its origins and probably the recent introduction to humans. This new study, published in mBio on Tuesday, seems to offer the first true clues for that mystery.
Researchers in India and Canada went on to search for environmental niches of India that were largely isolated from humans that could have been habitable for the yeast, based on the known biology and that of related species. They collected soil and water samples from the coastal wetlands of the Andaman Islands, an archipelago not far from the mainland. At two of the eight sites they searched – a salt marsh and a sandy beach – they found the fungus. The team found strains of C. auris which are susceptible and resistant to antifungals, and these strains have a close resemblance to strains collected from patients in India.
Altogether their work on C. auris suggests that “prior to its recognition as a human pathogen, it existed as an environmental fungus,” the authors wrote.
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Compared to other types Candida, C. auris is known to thrive especially in warmer temperatures. This has led some researchers to wonder whether climate change has played a role in its emergence as a human germ. The theory goes that climate change in their natural environment has led to the yeast adapting slightly and warmer temperatures being tolerated – the exact kind of temperatures that would make humans and other mammals a comfortable home once the yeast came in regular contact . with us.
The new findings seem to add more weight to the theory. Besides the fact that the fungi can and do live far away from humans, the team found subtle differences between the samples they found. One yeast strain found in the more remote salt march was slower to grow under warmer temperatures than the strains found on the sandy beach, and another salt march; this strain was also the only one susceptible to common antifungal drugs and less related to the strains seen in humans. Meanwhile, the other strains were resistant to antifungals and more hot. The strains found on the beach, which people sometimes visit, can be reintroduced into the area by humans, which may explain why it is more closely related to the strains found in patients.
It is possible that the researchers actually collected snapshots of the evolutionary journey of the yeast before and after climate change began to change their biology and infect humans first. In an accompanying comment written by some of the researchers who first proposed this theory – Arturo Casadevall of Johns Hopkins, Dimitrios Kontoyiannis of the University of Texas MD Anderson Cancer Center and Vincent Robert of the Westerdijk Fungal Biodiversity Institute in the Netherlands – agree with the conclusions.
‘This landmark discovery is crucial for understanding the epidemiology, ecology and emergence of C. auris as a human pathogen, ‘they wrote.
In a statement released by the American Society For Microbiology, which publishes mBio, said lead author Anuradha Chowdhary, a medical microbiologist at the University of Delhi in India: ‘This study takes the first step towards understanding how this pathogen in the wetland survives, but it’s just one niche. ”
The findings are still worth just one study, and so it not only proves that climate change has brought this latest nightmare into our lives, the authors acknowledge. And much remains to be done on how and where to go C. auris came from nature and in our hospitals, not to mention if there is anything that can be done to stop its spread.