C. auris Survives on Plastic
Candida auris, a naturally drug-resistant emerging fungal pathogen, is back in the news after a British hospital closed its intensive care unit as an extreme method to control the spread of the microbe. C. auris was first identified in 2009 and made headlines in 2016, when it caused several severe cases of candidiasis in the United States, in part due to misdiagnosis as the related fungus C. albicans. C. auris has continued to spread within the U.S., with most cases reported in New York or New Jersey.
A new Journal of Clinical Microbiology study reports another aspect of C. auris biology that may aid its emergence as a hospital-acquired infection: its ability to survive on plastic surfaces. Many Candida species are good at attaching to plastics, so the scientists involved hypothesized that C. auris would likewise be good at hanging around the hospital.
The scientific team, led by first author Rory Welsh and senior scientist Anastasia Litvintseva, spotted a known number of colony forming units (CFUs) onto plastic. At designated times, they rehydrated one of these spots to see how many CFUs remained. C. auris CFUs were recoverable for up to 2 weeks, with viable-but-nonculturable cells detected up to 4 weeks postinoculation by esterase enzymatic activity. This microbial ability to survive without nutrients or water suggests that the fungus may survive long enough on abiotic surfaces to be picked up by a hospital worker or patient, and emphasizes the importance for infection control to remove surviving yeast cells from surfaces.
While testing for fungal growth, the team made an another discovery: an improved enrichment broth that allows more sensitive detection from a variety of patient sample types. A chromogenic medium such as CHROMagar Candida is typically used to grow and differentiate among Candida species, but the researchers found a modified Salt Sabouraud-dextrose medium increased C. auris isolation efficiency over Chromagar, and had the added benefit of inhibiting many potentially confounding Candida species. Microbial detection is a key component to correctly diagnosing patients and mapping outbreaks, and this improved protocol may improve asymptomatic carrier or contaminated equipment identification.