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By Gary Evans, Medical Writer
A highly drug-resistant yeast continues to emerge in the U.S. healthcare system, spreading to 11 states and threatening frail patients with fatal bloodstream infections (BSIs).
Candida auris poses difficulties on virtually every infection control front. First and foremost, it is difficult to detect by conventional lab methods, meaning by the time you identify it, you may be looking at multiple cases and widespread environmental contamination. Standard clinical testing may misidentify C. auris as Candida haemulonii, a fungus rarely associated with invasive infections, the CDC reports.1
“Infection control personnel should first of all know what C. auris is, and then know whether their laboratory is able to identify it,” says Snigdha Vallabhaneni, MD, MPH, a medical epidemiologist in the mycotic diseases branch at the Centers for Disease Control and Prevention (CDC). “If not, they should know what the common misidentifications are so they can be looking out for them. It is important to set up a good channel of communication with the lab so infection control personnel are notified.”
For example, according to the CDC, “an increase in infections due to unidentified Candida species in a patient care unit, including increases [in detection] of Candida from urine specimens,” should raise a red flag.
Given its resistance to treatment, persistent environmental contamination, and long-term colonization of patients, some see C. auris as a “perfect storm” for “extensive, worldwide emergence” of a pathogen that was first identified in Japan in 2009.2
In addition to being difficult to identify, multidrug-resistant C. auris may not respond to commonly used antifungal drugs.
“Candida auris really has unprecedented levels of resistance compared to other types of yeast we see in healthcare settings,” she says. “Almost 90% are resistant to fluconazole, which is one of the most commonly available antifungals. Thirty percent have resistance to amphotericin. Unlike in the bacterial world, we only have three major classes of antifungals.”
By comparison, other common fungal pathogens may only have a 10% level of resistance to fluconazole, but C. auris has developed mechanisms of resistance that are still under investigation.
“We have been lucky in the U.S. in that we have not seen a pan-resistant isolate yet — resistant to all three classes of antifungals,” Vallabhaneni says. “That has definitely been seen in other parts of the world where C. auris has been around longer. It is very possible that we will see this. There are some other drugs in the pipeline that may be effective against C. auris.”
A range of mortality between 40% and 50% is seen in high-risk patients who contract C. auris bloodstream infections.
According to the CDC, risk factors include recent surgery, diabetes, broad-spectrum antibiotic and antifungal use, and central venous catheter placement. The severely infected patients are typically the “sickest of the sick,” those under long-term care with ventilators, tracheostomies, or gastrointestinal feeding tubes.
The CDC is seeing clear evidence of transmission in healthcare settings in the U.S., particularly in long-term care facilities with high-acuity residents.
“We definitely see transmission spreading from patient to patient on a single floor or even multiple floors in a healthcare facility,” Vallabhaneni says. “Most of the time this has really been in long-term care facilities.”
First reported in the U.S. in 2015, C. auris totaled 308 probable and confirmed cases as of April 30, 2018, according to the CDC. Most of the cases were in New York (169), New Jersey (89), and Illinois (31). Other states reporting at least one case include California, Connecticut, Florida, Indiana, Maryland, Massachusetts, Oklahoma, and Texas.
“In addition to these cases, it is important to note that we have about 500 more patients colonized with C. auris,” Vallabhaneni says. “It is on their skin or in their nares — sites where it is not causing them any infection or clinical problems, but they can still transmit it to others. So in total it is about 800 cases including clinical and colonized.”
Though there is hope the pathogen can be isolated and contained as cases are detected in the U.S., the numbers indicate its presence has more than doubled in the last year and it has become more widely dispersed.
Contributing to this trend is the lack of an effective decolonization protocol.
In New York, for example, only 16 of some 200 patients have been successfully decolonized, with the rest continuing to carry the bug.
“Very few patients have cleared colonization, so that means they can potentially transmit as long as they live, basically,” she says.
The CDC currently recommends3 that patients with confirmed or suspected C. auris infection should be under the following infection control precautions in acute care hospitals, long-term acute care hospitals, and nursing homes:
• In a single-patient room under standard and contact precautions. If single rooms are limited, “use them for patients who may be at highest risk of transmitting C. auris, particularly patients requiring higher levels of care (e.g., bed-bound),” the CDC says. “Patients with C. auris could be placed in rooms with other patients with C. auris,” but not with other multidrug-resistant organisms.
• “[Emphasize] adherence to hand hygiene. [Clean and disinfect] the patient care environment (daily and terminal cleaning).”
• “Minimize the number of staff who care for the C. auris patient. [With] multiple patients … consider cohorting staff who care for these patients.”
• “[Continue] contact precautions for as long as the person is colonized.”
CDC outbreak investigators have described C. auris as resembling more of a bacterial “superbug” than a typical yeast fungus. A characteristic of this is its ability to spread throughout the healthcare environment and persist on surfaces.
“We have found it in patient rooms, on all surfaces, and on the shared equipment and things that go in and out of a patient room — blood pressure cuffs, oximeter, crash carts, computers,” she says. “There is a real added emphasis on environmental disinfection, as well as all of your usual infection control measures like hand hygiene, contact precautions, gowns, and gloves.”
C. auris appears to be impervious to standard hospital-grade quaternary compound disinfectants, leading the CDC to recommend sporicidals indicated to kill Clostridium difficile. A new report4 on hospital outbreaks in Colombia underscores how the emerging pathogen can contaminate the healthcare environment well beyond the patient bedside. Of more than 300 environmental samples collected, 11% were positive for C. auris.
“We knew beforehand it could be in the patient’s immediate vicinity, such as the bed, mattress, and the handrails,” says lead author Nancy A. Chow, PhD, an investigator in the CDC mycotic diseases branch. “But we found it on floors, in mop buckets, alcohol gel dispensers, and various pieces of equipment.”
To reiterate the severity of that finding, a pathogen capable of causing 50% mortality rate in BSIs was found on hospital surfaces and objects far and wide.
“Candida auris is capable of extensive contamination,” Chow says. “This is all the more reason to promote aggressive infection control practices and proper disinfection strategies in the U.S.”
Another troubling finding in Colombia was that two nurses were colonized with C. auris. The two were identified among six healthcare workers screened for the pathogen.
“We found it on their hands and one healthcare provider also had a positive groin specimen as well,” Chow says.
Both healthcare workers cared for the same patient with C. auris, and the strain for all three was genetically identical. Given the difficulty of decolonizing patients, the obvious concern is that healthcare workers could become persistent carriers of the fungus.
Fortunately, that has not been the trend in global investigations, Chow says.
“Even though we found C. auris in two of six healthcare workers, there have been other studies in the U.K. and Spain looking at healthcare providers and they have not found colonization,” she says. “We still don’t know the role of healthcare providers, and that is something we are currently investigating.”
Testing also revealed colonization among contacts, family members, and noninfected patients.
The investigations in Colombia revealed how distinct clones of C. auris could establish in different regions, as genetic distinctions were observed in outbreaks separated by some 700 kilometers.
“We are seeing that there are some strains in the U.S. that look genetically related to strains from South America as well as South Asia,” she says.
“C. auris likely came in from other countries.”
In the U.S., the CDC is hoping to contain the fungus through its Antibiotic Resistance Lab Network (ARLN), a nationwide group of labs that rapidly identify pathogens and perform whole genome sequencing to shed light on transmission patterns.
Though originally designed to detect emerging gram-negative bacteria, the ARLN now is assisting in the identification of the emerging fungus.
“Early detection is the key to containment, so the ARLN can be a resource both for identifying and confirming the presence of C. auris,” Vallabhaneni says.
This is particularly critical in states where the pathogen has not gained a foothold. Rapid detection and infection control response to single cases has been successful in some states.
In places with more established C. auris, including New York, New Jersey, and Illinois, “a modified containment strategy” is implemented, she says.
“You’re not going to be able to stamp it out, but we want to change the epi curve of transmission,” she adds.
“We are still going to see cases, but can we reduce the number of cases and reduce transmission? That is our goal in those states.”
Though that suggests a response to a pathogen that has essentially become endemic, Vallabhaneni is reluctant to concede as much at this stage. “We do think it is becoming more of a problem, but I wouldn’t use the word ‘endemic’ yet,” she says.
“In the big scheme of things, it is still only a few hundred cases and there are millions of people in New York and Chicago.”
Similar to what has been seen with the emerging gram negatives such as CRE, C. auris threatens to establish a reservoir in long-term care facilities from which it may then spread across the healthcare continuum.
“These seem to be places where transmission is amplified,” she says.
“Patients are in contact with each other longer, there are long lengths of stay, and resources for infection control are less than [in] hospitals. That doesn’t mean that other places can sit back and relax. There is a lot of transfer of patients between long-term and acute care.”
Financial Disclosure: Peer Reviewer Patrick Joseph, MD, reports that he is a consultant for Genomic Health Reference Laboratory, Siemens Clinical Laboratory, and CareDx Clinical Laboratory. Senior Writer Gary Evans, Editor Jesse Saffron, Editor Jill Drachenberg, Nurse Planner Patti Grant, RN, BSN, MS, CIC, and Editorial Group Manager Terrey L. Hatcher report no consultant, stockholder, speaker’s bureau, research, or other financial relationships with companies having ties to this field of study.