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The superbug Candida auris is giving rise to warnings – and big questions



W hat's known about the fungus Candida auris confounds the scientists who study it, the doctors who struggle to treat the persistent infections it causes, and the infection control teams that seek to clear it from hospital rooms after infected patients leave

But the list of what's not known about this highly unusual fungus is longer still – and fascinating.

Candida auris was first spotted a decade ago in Japan, and more recently has been popping up in far-flung parts of the globe. The fungus does not behave like a fungus. It causes outbreaks like a bacterium and is generally highly resistant to available antifungal drugs.

Recently, STAT has asked a number of scientists to describe what they see as the most pressing research questions facing the field. Here are their thoughts:

Where does the darn thing come from?

Most fungi ̵

1; and there are multitudes – are found in a variety of places. In soil, in insects, in plants. But the only place of C. auris has been found to date is in people

It has to be somewhere else in nature, said Tom Chiller, chief of mycotic (ie fungal) diseases at Centers for Disease Control and Prevention. 19659003] "They did not just 'poof!' Appear, 'Chiller insisted. "They've been here for a while. And I wonder where they were hiding. "

Tejas Bouklas, an assistant professor in the Department of Biomedical Sciences at Long Island University, Post, campus, would like to know what other species of C. auris can infect. (19659003) Why and how did different clones of the fungus pop up across the world in a very short time span?

A few years after its 2009 discovery, a number of countries around the globe have started reporting C. auris cases. Initially the thinking was that travel or medical tourists were responsible for the movement. But when the genetic sequences were compared, it was clear that it was not the case.

Samples of C. auris circulating in South Africa all looked very alike. So did the samples from Asia and from South America. But none of them looked like each other.

Chiller noted that C. auris cases reported in Japan seemed to be mainly ear infections – the original finding of the fungus was from an ear infection, hence the "auris" of the name. In Japan, the fungus does not seem to cause an invasive disease; it does not get into the bloodstream. But in South Korea, the same clone (think strain) of C. auris does.

"Would not it be fascinating to know what changes in that organism that makes it go from an external ear infection to an invader?" Chiller mused . "Is there something that changes in the genome? … I wish people would just jump on that and study it. "

Knowing how and why they are crucial, said Dr. Luis Ostrosky, Professor of Infectious Diseases at McGovern Medical School at the University of Texas Health Science Center in Houston.

That's the only way we're going to control it. Because we do not know the source, we're kind of fighting the fire a bit at a time, "said Ostrosky, who is the director of his hospital's mycology research laboratory. "If you do not know the source of an infection, you're never going to control it completely. And it's going to happen. "

Why now?

The almost simultaneous emergence of a highly drug resistant fungus that acts like a bacteria seems … well, kind of unsettling. What happened to this species of Candida to act in ways

A related concern: If this fungal species learned this trick, can others? Is this what the future holds?

A just-published study in the journal mBio theorizes that climate change may have contributed in part to the emergence of C. auris. The authors say that human body temperature has historically acted as protection against invasive fungal infections – in effect, we are too hot for them to grow well in us.

If the theory is correct, other fungi may follow C. auris' path, posed by Arturo Casadevall, of the Johns Hopkins Bloomberg School of Public Health, and his co-authors

"Whether C. auris is the first example of new pathogenic fungi emerging from climate change … its emanation stokes worries that humanity may face new diseases from fungal adaptation to hotter climates," they write

Chiller said uncovering C auris' backstory is important. "These things are going to continue to emerge. And understanding how they emerge and where they emerge might lead us to prevention strategies or reactive strategies or preparation strategies for the next big thing. "

Could C. auris help other fungi adapt to be greater threats to humans?

That's a question Bouklas is wondering about. "The more ubiquitous it becomes, the more problematic. Because now it could potentially transmit DNA to other Candida species. And maybe even bacteria, "she said.

That idea is not far-fetched. Fungi can mate sexually, Chiller pointed out, allowing them to swap large amounts of DNA.

Where did it get its "Ironman suit"

That's the way Johanna Rhodes describes the drug-resistant superpowers of C. auris. Rhodes is an epidemiologist at Imperial College London, who has been working on C. auris since a 2016 outbreak at London's Royal Brompton Hospital.

Some of the patients in that outbreak developed resistance to a whole class of antifungal drugs within a month – is just unheard of, "she said.

Bouklas also has resistance questions. "Why does it have such a strong resistance to every known anti-fungal?" She asked. "All of them use a different mechanism of killing …. That's the biggest question. "

Often pathogens that develop drug resistance pay for it in other ways – it's called" fitness cost. "Yes, Bacterium X can escape Drug Y, but in acquiring that skill becomes less transmissible or weaker

Not C. auris

"It seems that it has resistance at no fitness cost. It is still able to form biofilms. It's still able to persist [in an environment]. It is still able to infect, "Rhodes said.

Biofilms are a layer of pathogens – in this case, fungi – that attach to the surface and effectively lay in wait there. Sometimes biofilms form in the drains or pipes leading from sinks in hospitals. Many such wet surfaces, but C. auris can form dry biofilms, lurking on surfaces like bed railing in a contaminated hospital room. These infectious residues can transmit C. auris from one patient to the next in a hospital room.

This fungus is really hard to get rid of. That's something Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, thinks it needs to be explored

"Why is it so different from others that you could easily, by wiping it with whatever it is you wipe it with, it goes away?

What is the best way to treat this disease? patients who develop C. auris infections

That's a question Ostrosky, who has treated patients with C. auris infections, would very much like to answer

Chiller has a related question: How often is C. auris causing death

Between 30% and 60% of patients who develop C. auris infections die, the CDC estimates. But in the United States, anyway, C. auris infections occur in the sickest of patients: those whose immune systems have been compromised, who have spent prolonged periods on ventilators – machines that breathe for people whose lungs are not up to the task.

Are these people dying from their C. auris infections? Or are their other medical problems the cause of death? "Are they dying of C. auris or with C. auris? I still want to know that, "said Chiller, though he acknowledged that" these are really hard studies to do. "

– An earlier version of this article misspelled Luis Ostrosky's name.


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