Indiana University researchers have measured the accuracy of four commercial tests to determine how they perform in the detection the pathogenic yeast Candida auris (C. auris), a rapidly emerging public health threat.
They presented their findings at ASM Microbe 2023, the annual meeting of the American Society for Microbiology, held June 15 to June 19 in Houston.
C. auris carries a high mortality rate, killing more than one in three infected people. The most common symptoms of invasive Candida infection are fever and chills that fail to improve after antibiotic treatment. Infections often emerge in healthcare settings, where people are particularly vulnerable, and infection rates are rising rapidly.
Although C. auris is commonly multidrug- and antifungal-resistant, levels of antifungal resistance can vary widely across isolates — i.e., pure samples obtained from infected individuals, rather than grown in a laboratory. According to Clinical & Laboratory Standards Institute guidelines, all Candida auris isolates should undergo antifungal susceptibility testing. Therefore, clinicians often analyze individual samples for their susceptibility to treatments. Hospital labs often send samples to larger specialty laboratories for analysis.
Matching a C. auris infection with an effective antifungal is a critical clinical decision which relies on susceptibility testing. However, according to the researchers, most commercially available antifungal tests perform poorly for many treatments, and no U.S. Food and Drug Administration (FDA)-approved tests are commercially available for C. auris. However, since tests are available for other pathogenic yeast infections, the researchers investigated those tests for use with C. auris.
The researchers used four commercially available tests for pathogenic yeasts to analyze 50 C. auris isolates, collected from the Centers for Disease Control and Prevention (CDC) and the Indiana University Health Hospital, for their susceptibility to available antifungals. The results were mixed. Two of the tests correctly characterized echinocandins, antifungal drugs administered intravenously and often used to treat C. auris.However, those two tests performed poorly for fluconazole, which is part of a group of treatments known as triazoles, and the only C. auris treatment available orally.
Other results revealed that some available tests incorrectly reported resistance to a drug when a strain was actually susceptible, and susceptibility when a strain was resistant.
Although though some tests performed well for some drugs, the researchers found that, as of now, no single method accurately reports the susceptibility of C. auris to antifungal treatments.
New FDA-cleared tests would aid clinical decisions and improve care for patients infected with this potentially lethal, often drug-resistant pathogen, the researchers noted.
The rising threat of C. auris to health systems has prompted at least one test developer to begin developing a test to detect it in U.S. hospitals. In June, T2 Biosystems said that it applied to the FDA for breakthrough device designation for its C. auris test.
