'Superbug' Clusters: Multidrug-Resistant Fungus Spreads In 2 US Cities

Health officials have found evidence of the spread of an untreatable "superbug" at facilities in two U.S. cities. The "emerging" fungus poses a "serious global health threat."

The cases were reported at a nursing home and at two hospitals in Washington D.C., reported AP News. Specifically, among the 101 clinical cases of Candida auris (C. auris) in D.C. and the 22 simultaneous cases in Dallas, Texas, from January to April this year, a handful of them had isolates that proved to be resistant to all the antifungal medications currently used against such infections.

C. auris is an "emerging, often multidrug-resistant yeast" that's highly transmissible and has been linked to healthcare-associated outbreaks, the Centers for Disease Control and Prevention (CDC) said in its Morbidity and Mortality Weekly Report (MMWR) this week.

So far, there are three major classes of antifungal antibiotics used to treat invasive infections: azoles, polyenes and echinocandins.

"Approximately 85% of C. auris isolates in the United States are resistant to azoles, 33% to amphotericin B, and 1% to echinocandins, based on tentative susceptibility breakpoints," the CDC said. "Echinocandin resistance is a concerning clinical and public health threat, particularly when coupled with resistance to azole and amphotericin B (pan-resistance)."

According to the CDC, pan-resistant C. auris were previously reported in the U.S. and other countries, albeit "rarely." For instance, three cases of pan-resistant C. auris were reported in New York in 2019 after the isolates were found to be resistant to echinocandins, which are considered to be the "last line of defense," AP News noted.

The cases didn't have evidence that the infections spread from one patient to another. Instead, it's likely the resistance formed following treatment with echinocandins.

However, the new cases had no evidence of prior echinocandin use.

"Each cluster involved common health care encounters and no known previous echinocandin exposure, suggesting transmission of pan- and echinocandin-resistant strains for the first time in the United States," the CDC explained.

"This is really the first time we've started seeing clustering of resistance" in which patients seemed to be getting the infections from each other, CDC's Dr. Meghan Lyman said as per AP News.

There are "no known epidemiologic links" between the Texas and D.C. clusters, the CDC noted. Among the five cases who were fully resistant to the available treatments, three died.

Both outbreaks are still ongoing, Lyman said further, adding that even more cases have been identified since April.

According to the CDC, most C. auris strains in the U.S. are "susceptible" to echinocandins, but reports of echinocandin or pan-resistant incidents have been increasing. This suggests that the organism has the ability to "develop resistance quickly."

"Antifungal medicines commonly used to treat Candida infections often don't work for Candida auris. Some C. auris infections have been resistant to all three types of antifungal medicines," the CDC said. "Although C. auris was just discovered in 2009, it has spread quickly and caused infections in more than a dozen countries."