Candida Auris: An Enigmatic and Difficult-to-Treat Fungal Pathogen

With the unpredictability of when it will appear, and its propensity to be multidrug-resistant, this particular pathogen is challenging to diagnose and treat.

The emergence of Candida auris (C auris) was first identified in a single case in Japan where a man had it appear in his ear. According to the Centers for Disease Control and Prevention (CDC), a retrospective review of Candida strain collections found that the earliest known strain of the fungus dated back further to 1996 in South Korea.

In the ensuing years, the fungal pathogen has been mysterious in appearing very quickly in places and then disappearing almost as quickly. Earlier this year, two outbreaks were made public with one happening at a nursing home in Washington, DC, and the other at 2 hospitals in the Dallas area.

During this outbreak, a cluster of 101 cases was detected in the Washington, DC, nursing home and a cluster of 22 cases was detected in 2 Dallas areas hospitals from January to April.

According to reports, some of these patients infected with C auris did not show any clinical improvement after being treated with all 3 major classes of the antifungals. In fact, in 5 patients who were fully resistant to treatment, 3 of them died.

While C auris does not appear to have a high incidence rate, the infection presents some serious challenges to clinicians. It is especially troublesome as the CDC has outlined 3 main concerns about it, including:

  • It is often multidrug-resistant;
  • It being a newer, emerging fungus, it can be challenging for labs to diagnose with standard laboratory methods, which can lead to misidentification and in turn lead to the incorrect treatment and management;
  • And lastly, it can quickly lead to outbreaks in health care facilities.

Although C auris fungal infection is still relatively rare, when it occurs in the health care setting, it can quickly take hold and become an outbreak if infection prevention measures are not taken.

“The overwhelming majority of Candida auris clinical isolates are resistant to one of the 3 classes of antifungals that we have to treat invasive infections,” Jeffrey Rybak, PharmD, PhD, instructor, Department of Pharmaceutical Sciences, St. Jude Children’s Research Hospital, said. Rybak has been conducting research on C auris in trying to identify novel targets for therapy, apply next-generation sequencing technologies, and develop molecular tools to advance the study of the fungus.

Rybak also points out that isolates might become resistant while someone is on therapy. “Even while it might be susceptible upfront, after a week or two of therapy, we may find that the patient has an infection now caused by an isolate of the same Candida auris that has become resistant to the echinocandins and we are really left with nothing else.”

New antifungal agents such as Ibrexafungerp (Brexafemme) are being studied for C auris treatment. Rybak says these investigational agents show promise against the infection, but that they need to see more clinical trials to see their full treatment utility.

Contagion spoke to Rybak about the challenges of multidrug resistance with C auris, how diagnosing it is evolving, the merits of monotherapy over combination therapy, what to consider in seeing resolution of symptoms, and some of the big picture public health concerns associated with this infection.