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Skin shedding may contribute to spread of C. auris
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SAN FRANCISCO — Patients colonized with Candida auris carry a high burden of the emerging and often multidrug-resistant fungal pathogen on their skin, suggesting that the natural process of skin shedding among these patients leads to contamination of the heath care environment and contributes to transmission, according to findings presented at ASM Microbe.
C. auris presents a public health concern because of its ability to cause large and persistent outbreaks, such as the outbreak in New York City hospitals. The specific mechanisms of transmission are not clear, which makes controlling these outbreaks difficult, according to Joe Sexton, PhD, a postdoctoral fellow in the CDC’s Mycotic Diseases Branch, and colleagues.
It is known that patients with C. auris can remain colonized for months, and the researchers underscored the pathogen’s ability to colonize a patient’s skin and survive on dry surfaces for weeks. C. auris has been found on many surfaces in the health care environment, including beds, windowsills, doorknobs and mobile equipment, but it is unclear how they are becoming contaminated, Sexton and colleagues noted.
“We’re trying to learn how Candida auris spreads because what I think makes Candida auris so concerning compared with other pathogenic yeast is that it’s transmissible,” Sexton told Infectious Disease News. “We’re still trying to learn how it spreads from person to person. This study is the first in that it looks into that mechanistically.”
According to Sexton and colleagues, an unnamed ventilator-capable skilled nursing facility is currently experiencing an outbreak of C. auris that started with a single case in March 2017. Although the facility implemented contact precautions, bleach disinfection of surfaces and chlorhexidine decolonization, the proportion of patients testing positive for C. auris increased to 71% since the first case was identified, the researchers reported.
They investigated the relationship between C. auris concentrations in composite swab samples of bilateral axilla or groin skin collected from 28 patients and two environmental samples collected from surfaces associated with each patient., resulting in 56 total environmental samples.
Sexton and colleagues reported high C. auris concentrations in the skin swabs of colonized patients that “often exceeded” 106 to 107 cells/mL. They observed a “strong, positive and statistically significant” relationship between C. auris concentrations in the skin swabs with their associated environmental samples.
“This provides an answer, mechanistically, of how those surfaces get contaminated. I hope this can help guide infection control efforts, focusing on decontaminating surfaces that are high touch for the patients, especially the bed,” Sexton said.
“The idea is that we can use mechanistic insights to improve the way we approach infection control to help focus on the most important things to decontaminate.” – by Marley Ghizzone
Reference:
Sexton J, et al. Mechanisms of Candida auris transmission within the health care environment; Presented at: ASM Microbe; June 20-24, 2019; San Francisco.
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Cornelius (Neil) J. Clancy, MD
The previously unrecognized yeast C. auris has emerged globally in recent years as a cause of health care-associated infections, often occurring as outbreaks of multiple infections. Outbreaks of C. auris infections have been characterized by patient-to-patient spread and extensive environmental contamination by causative strains. In this regard, C. auris differs from most Candida species that are pathogenic to humans. Invasive infections by these other species generally are caused by a strain that is colonizing the patient's own gastrointestinal tract or other body site. Each patient is usually infected with his or her "own strain," and patient-to-patient transmission, environmental contamination and outbreaks of invasive candidiasis are uncommon. For these reasons, infection control measures, prior to the appearance of C. auris, have not played a prominent role in how clinicians combat Candida infections at their facilities. Understanding the mechanisms by which C. auris is able to persist in health care environments and pass between patients, even in the face of rigorous decontamination efforts, is crucial to devising rational infection control and prevention strategies. The take-home message from this study is that C. auris colonization of the skin of patients is common, often associated with very high concentrations of C. auris, and correlates closely with the amount of C. auris recovered from inanimate surfaces in the nearby environment. Immediate questions stemming from this study are how generalizable the findings are to other facilities; if surveillance for skin and environmental colonization, coupled with targeted decontamination strategies can arrest transmission of C. auris within health care facilities; what the directionality of transmission is; and what roles health care providers or others play in this dynamic.
The data extend our understanding of relationships between colonization of patients and the health care facility environment. We have known that C. auris can colonize patients' skin and numerous sites within patients' rooms and health care facilities. This study and others are now trying to define the patterns of transmission between patients, staff, visitors and health care environments.
Ongoing research on the environmental niches from which C. auris has emerged, and the environmental factors that have led to its emergence are important compliments to research of this sort at the level of the patient and his or her immediately surrounding health care environment. The central enigma of the recent and explosive emergence of C. auris is why has it arisen seemingly out of nowhere, independently and simultaneously on different continents?
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