Misidentification of Candida guilliermondii as C. famata among Strains Isolated from Blood Cultures by the VITEK 2 System

Abstract EN

Introduction.

The aim of this study was to differentiate between Candida famata and Candida guilliermondii correctly by using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and gene sequencing.

Methods.

Twenty-eight Candida strains from blood cultures that had been identified as C.

famata (N=25), C.

famata/C.

guilliermondii (N=2), and C.

guilliermondii (N=1) by the VITEK 2 system using the YST ID card were included.

We identified these strains by MALDI-TOF MS and gene sequencing using the 28S rRNA and ITS genes and compared the results with those obtained by the VITEK 2 system.

Results.

All 28 isolates were finally identified as C.

guilliermondii.

Sequencing analysis of the 28S rRNA gene showed 99.80%–100% similarity with C.

guilliermondii for all 28 strains.

The ITS gene sequencing of the strains showed 98.34%–100% homology with C.

guilliermondii.

By MALDI-TOF, we could correctly identify 21 (75%) of 28 C.

guilliermondii isolates.

Conclusion.

We should suspect misidentification when C.

famata is reported by the VITEK 2 system, and we always should keep in mind the possibility of misidentification of any organism when an uncommon species is reported.