A fungus described by the Centers for Disease Control and Protection (CDC) as a "serious global health threat" has been found in several locations out in the wild.
Candida auris was first described in 2009 in Japan, before spreading to South Korea, Asia, Europe, and across the US. The main challenges posed by the fungus – more specifically, a type of yeast – is that it is often resistant to multiple antifungal drugs that are used to treat Candida infections. As well as that, it's difficult to identify, can remain in the host for several months, and can easily spread within hospital settings – especially where it hasn't been identified correctly.
In a new study, medical mycologist Anuradha Chowdhary, PhD, led a team analyzing soil, sand, and water samples collected from beaches, marshes, and mangrove swamps in the tropical Andaman Islands. Even in the samples taken from salt marshes, where human activity is low, the researchers found Candida auris – with one of the two samples proving to be susceptible to multiple antifungal drugs.
Of more concern were samples taken from areas such as the beach, where 22 samples were found to contain the fungus – all of which were resistant to multiple antifungals.
"The isolates found in the area where there was human activity were more related to strains we see in the clinical setting," Chowdhary said in a statement. Future studies, she said, may be able to explain that connection. "It might be coming from plants, or might be shed from human skin, which we know C. auris can colonize. We need to explore more environmental niches for the pathogen."
The findings, the authors write in their study published in the journal mBio, represent the first time that the fungus has been discovered outside of a hospital setting. From genetic testing of the samples, they believe that the fungus can survive well in certain conditions outside of human hosts.
"The high genetic diversity of C. albicans from old oaks shows that they can live in this environment for extended periods of time," the team write of the separate pathogenic yeast Candida albicans. "Similarly, isolation of C. auris from the marine environment suggests wetlands as a niche for C. auris outside its human host."
A previous hypothesis suggested that the fungus could be native to wetlands, and went unnoticed to humans before it became pathonogenic to humans when adaptations to higher temperatures caused by climate change made it thrive within us and other mammals.
"The observation that one environmental isolate grew slower at mammalian temperatures than clinical strains is consistent with the notion that their ancestor recently adapted to higher temperatures," Dr. Arturo Casadevall, chair of the Department of Molecular Microbiology and Immunology at Johns Hopkins Bloomberg School of Public Health in Baltimore in a commentary piece about the study.
"The knowledge that C. auris can be recovered from the environment should prompt additional searches to define its ecological niches, and the analysis of future environmental isolates will provide evidence for validating or refuting the global warming emergence hypothesis."