Deadly super yeast found in nature for the first time

Culturing a Candida auris strain in a Petri dish at a CDC laboratory.

A strain of Candida auris being cultured in a Petri dish in a CDC laboratory.
Photo: Shawn lockhart (AP)

A terrifying superbacterial yeast that is killing people in hospitals may also survive well outside of them, according to a new study published For the first time, researchers say they have discovered multi-drug resistant strains of the fungus Candida auris in a natural setting, in the remote wetlands of India. The findings indicate that these types of environments could be the native home of yeast, while providing evidence that warmer temperatures due to climate change have made the fungus dangerous to humans, as some scientists have theorized.

C. auris It was first discovered in 2009 by doctors in Japan, who isolated it from a patient’s ear infection (the earliest known cases date back to the mid-1990s, however). Since then, yeast has been found in more than a dozen countries, including the United States. It can cause life-threatening infections, especially in already weakened hospital patients. But what makes yeast especially scary is that it is often resistant to multiple antifungal medications at once, making these infections difficult to treat and frequently fatal. The fungus is also a survivor outside the human body, so once it establishes itself somewhere, it is incredibly hard to remove it from the environment. If that wasn’t enough C. auris it cannot 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. That threat has made understanding its origins and likely recent introduction to people even more important. This new study, published on mBio on Tuesday, it appears to provide the first real clues to that mystery.

Researchers in India and Canada searched Indian environmental niches largely isolated from humans that might have been habitable for yeast, based on their 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. In two of the eight sites they searched, a marsh and a sandy beach, they found the fungus. The team found strains of C. auris that were both susceptible and resistant to antifungals, and these strains bore a strong genetic resemblance to strains collected from patients in India.

In total, his work on C. auris suggests that “prior to its recognition as a human pathogen, it existed as an environmental fungus,” the authors wrote.

Compared to other species of Candida, C. auris it is known to thrive especially well in warmer temperatures. That has made some researchers wonder if climate change influenced its appearance as a human germ. The theory holds that changes in the climate in their natural environment led the yeast to adapt slightly and become even more tolerant of warmer temperatures, the exact type of temperatures that would make humans and other mammals a comfortable home. once the yeast began to come into contact regularly. with us.

The new findings seem to add more weight to that theory. In addition to showing that these fungi can and do live far from people, the team found subtle differences between the samples they found. One yeast strain found on the more remote salt march grew more slowly under warmer temperatures than strains found on the sandy beach and another strain from the salt march; this strain was also the only one susceptible to common antifungals and least related to the strains seen in people. Meanwhile, the other strains were all resistant to antifungals and warmer. The strains found on the beach, where people sometimes visit, could have been reintroduced into the environment by humans, which could explain why they were more closely related to the strains found in patients.

The researchers may have essentially collected snapshots of yeast’s evolutionary journey, before and after climate change began to alter its biology and infect people for the first time. In an accompaniment commentary 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, agreed with those conclusions.

“This historical discovery is crucial to understanding the epidemiology, ecology, and emergence of C. auris as a human pathogen, ”they wrote.

in a statement Published by the American Society for Microbiology, which publishes mBio, lead author Anuradha Chowdhary, a medical mycobiologist at the University of Delhi in India, said: “This study takes the first step towards understanding how this pathogen survives in the wetland, but this is just a niche. “

The findings are still only the value of one study, so alone they do not prove that climate change has ushered this latest nightmare into our lives, which the authors acknowledge. And there is still much to be resolved on how and from where C. auris it emerged from the wild and entered our hospitals, not to mention if there is anything that can be done to stop its spread.


Source link