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SAN DIEGO -- A pathogenic fungus that only recently attracted the attention of researchers has multidrug-resistant (MDR) strains that can cause untreatable bloodstream infections, a CDC investigator said here.

"I never thought I'd be talking about a fungal superbug," said Tom Chiller, MD, chief of the agency's mycotic diseases branch.

Even when the fungus, Candida auris, is not completely resistant to the available antifungal drugs, it can be a challenge, Chiller told a symposium here at the annual IDWeek meeting, sponsored jointly by the (IDSA), the (PIDS), the (SHEA), and the (HIVMA).

The fungus, first reported in 2009 and since seen around the world, is readily transmitted since it colonizes both the skin and the environment, but is not easily identified or treated. And like other Candida species, it can cause severe invasive disease and death.

Candidemia is already the most common bloodstream infection in the U.S., Chiller said, with a 30% mortality rate. But it has usually been thought of as an "autoinfection" -- something that arises in sick people because they are colonized by a Candida species that opportunistically becomes an infection.

Resistant strains of the new kid on the block, especially since it appears to be easily transmitted in healthcare facilities, are a worrisome challenge, he said.

Indeed, the MDR strains of C. auris "meet the definition of a superbug," commented Andy Pavia, MD, of the University of Utah, who moderated the session at which Chiller spoke, adding those strains are "very scary."

So far, the number of cases in the U.S. appears to be "quite modest," he told 番茄社区app, but he and others are concerned that MDR C. auris might gain a foothold if physicians aren't vigilant and aggressive about controlling the fungus.

"It's like VRE and CRE (vancomycin-resistant enterococci and carbapenem-resistant enterobacteriaceae)," he said. "Once it colonizes a hospital your changes of getting rid of it are pretty poor."

The good news is that so far C. auris appears to be relatively rare in the U.S., Chiller told 番茄社区app. The CDC put out an alert last year, asking for reports of the fungus; retrospective review of hospital microbiology records showed very few cases before 2016 and fewer than 150 all told.

So far, complete resistance to all three main classes of anti-fungal medications has not been seen here.

"I think these are recent introductions," Chiller said. "I'm still optimistic, but it's going to be a challenge."

Physicians should be vigilant and treat suspected cases of C. auris disease aggressively, he said. They should:

• Place patients in single rooms and use standard contact precautions
• Emphasize hand hygiene, including use of alcohol-based hand rubs
• Clean the patient care environment with disinfectants
• Screen patients to identify C. auris colonization, and report suspected cases to local public health authorities and to CDC

If those steps sound like what is usually done in cases of drug-resistant bacteria, that's exactly right, Chiller said.

Importantly, he said, C. auris can be misidentified using traditional methods; what's needed for certainty is and not all labs have that technology available.

In "one-off" cases, Chiller told 番茄社区app, aggressive decolonization and decontamination measures can probably stop the fungus from getting established in a health care facility.

But in his talk he cited the losing battle fought by a British hospital, which had nine cases of bloodstream infections, more than 40 colonized patients, a myriad of contaminated surfaces, and what they thought was clear patient-to-patient transmission.

Nothing the British doctors could do worked -- contact precautions, screening, chlorhexidine baths, cleaning with bleach -- and they eventually closed the ICU. "I hadn't heard of an ICU being shut down for a fungus before," Chiller said, "so that really got our attention."

The organism got its name in 2009, when it was isolated from the ear canal of a woman in Japan, Chiller said. By 2016, it had been identified in several other countries in various regions of the world.

Whole genome sequencing of isolates showed, surprisingly, that isolates fell into four distinct groups along geographic lines. In other words, C. auris was not a single strain spreading around the world.

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