Pan-resistant C auris isolates are defined as being resistant to the triazole class, polyene class, as well as echinocandins.
Candida auris was first identified in the United States and has been particularly prevalent in New York. As of June 28, 2019, a total of 801 patients with C auris were identified in New York. Closer analysis found that 3 of these cases were pan-resistant infections that developed following treatment with antifungals, including echinocandins.
Details of the 3 cases were presented in an article in the US Center for Disease Control and Prevention’s Morbidity and Mortality Weekly Report.
“The occurrence of these cases underscores the public health importance of surveillance for C auris, the need for prudent antifungal prescribing, and the importance of conducting susceptibility testing on all clinical isolates, including serial isolates from individual patients, especially those treated with echinocandin medications,” the authors wrote.
Pan-resistant isolates are defined as being resistant to the triazole class, polyene class, as well as echinocandins. The cases were identified through testing conducted at the Wadsworth Center, the New York State public health laboratory where samples are tested to confirm C auris isolates.
Two patients were initially identified as having a pan-resistant C auris infection. Both were older than 50 years and were residents of long-term care facilities with documented co-morbid conditions and were dependent on ventilators and colonized with multidrug-resistant bacteria.
According to the authors of the report, among isolates collected from the 2 patients, all were resistant to fluconazole, 7 of 13 isolates from 1 patient and 3 of 5 isolates from the other patient were resistant to amphotericin, and 0 isolates were initially resistant to echinocandins. Both patients were treated with “prolonged” courses of echinocandins following identification of C auris. Cultures taken after therapy identified resistance to fluconazole, amphotericin B, and echinocandins. Both patients died; although the role of C auris in their deaths is not known.
No epidemiologic links were found between the 2 patients and neither had known domestic or recent travel. Additionally, no pan-resistant isolates were identified among contacts of the patients or on surfaces from the patients’ rooms.
After these cases were identified a retrospective review of all New York isolates and susceptibility testing a third patient was identified to have a pan-resistant case. This individual was also over the age of 50 years and had comorbid infections and admission at a long-term care facility.
The patient was eventually discharged to a long-term care facility and placed on contact precautions. The report notes that serial surveillance cultures from several body sites continued to be obtained and all remained negative for >6 months until the patient died from underlying medical conditions.
“The precise mechanism of resistance in these isolates is unknown, although echinocandin resistance in other species of Candida is linked to mutations in the drug target protein Fks1,” the authors wrote.
Approximately 3 years into the New York outbreak, these pan-resistant isolates still appear to be rare, but their emergence is concerning. Surveillance for additional pan-resistant isolates in New York is ongoing.
The authors of the report advise that repeat susceptibility testing should be conducted and patients who have been treated echinocandins should especially be screened.
“These findings illustrate the need to continue surveillance for C auris, encourage prudence in the use of antifungal medications, and conduct susceptibility testing on all clinical isolates, including serial isolates from a single patient, especially those treated with echinocandins,” the authors concluded.