Infection preventionists should ensure their labs have the diagnostic capabilities to detect multidrug-resistant Candida auris, which often is misidentified as less pathogenic fungi.

“One of the challenges of C. auris is misidentification — most of the identification methods that clinical labs use cannot identify it reliably,” says Snigdha Vallabhaneni, MD, MPH, a medical epidemiologist in the mycotic diseases branch at the Centers for Disease Control and Prevention (CDC).

If misidentification is suspected, clinicians can seek confirmation from state labs and the CDC’s nationwide Antibiotic Resistance Lab Network. “We know that this can be misidentified, but all you need is confirmation with appropriate identification methods.”

The ability of the multidrug-resistant fungus to elude detection and continue spreading in the healthcare environment was dramatically underscored in a report of outbreak investigations in Colombia.¹

According to the CDC, the response to hospital outbreaks in Colombia in 2016 was hindered by misidentification of the pathogen.

An unusual 75 isolates of Candida haemulonii — a yeast that rarely causes invasive infections — were reported in ICU patients by health officials.

Looking at 45 of the isolates, the CDC and co-investigators determined, via matrix-assisted laser desorption ionization time-of-flight mass spectrometry, that all of them were C. auris.

“Clinical laboratories should be aware that automated laboratory systems might incorrectly identify C. auris, particularly as C. haemulonii, although the species reported depends on the system,” the CDC advises.

“C. auris can be misidentified as a number of different organisms when using traditional phenotypic methods for yeast identification such as VITEK 2 YST, API 20C, BD Phoenix yeast identification system, and MicroScan,” the CDC warns.¹

The type of misidentified organism varies somewhat by the diagnostic system used. The CDC lists these diagnostics systems and the Candida organisms most commonly misidentified:

• Vitek 2 YST: C. haemulonii, C. duobushaemulonii;
• API 20C: Rhodotorula glutinis (characteristic red color not present), C. sake;
• BD Phoenix: C. haemulonii, C. catenulata;
• MicroScan: C. famata, C. guilliermondii, C. lusitaniae, C. parapsilosis;
• RapID Yeast Plus: C. parapsilosis.

“As C. auris continues to gain recognition, updated versions of other yeast identification platforms may be able to identify [it],” the CDC advises.

“Please consult the instrument manufacturer for more information. When in doubt, please forward suspected C. auris specimens to CDC or state or regional public health laboratories for further characterization.”

“All confirmed isolates of C. auris should be reported to local and state public health officials and to CDC at candidaauris@cdc.gov,” the CDC says.

If C. auris is confirmed in a healthcare facility, the CDC recommends conducting a lab look-back study to see if prior cases had been missed.

“Review past microbiology records — as far back as 2015, if possible — to identify cases of confirmed or suspected C. auris,” the CDC advises.²

REFERENCES

1. Escandón P, Cáceres CH, Espinosa-Bode A, et al. CDC. Notes from the Field: Surveillance for Candida auris — Colombia, September 2016–May 2017. MMWR 2018;67(15);459–460.
2. CDC: Recommendations for Infection Prevention and Control for Candida auris. Feb. 18, 2018. Accessed June 1, 2018, at:
   https://bit.ly/2Hapm7K.