title: Multidrug-Resistant Candida auris Misidentified as Candida haemulonii: Characterization by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry and DNA Sequencing and Its Antifungal Susceptibility Profile Variability by Vitek 2, CLSI Broth Microdilution, and Etest Method.
abstract: Candida auris is a multidrug-resistant yeast that causes a wide spectrum of infections, especially in intensive care settings. We investigated C. auris prevalence among 102 clinical isolates previously identified as Candida haemulonii or Candida famata by the Vitek 2 system. Internal transcribed spacer region (ITS) sequencing confirmed 88.2% of the isolates as C. auris, and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) easily separated all related species, viz., C. auris (n = 90), C. haemulonii (n = 6), C. haemulonii var. vulnera (n = 1), and Candida duobushaemulonii (n = 5). The in vitro antifungal susceptibility was determined using CLSI broth microdilution (CLSI-BMD), the Vitek 2 antifungal susceptibility test, and the Etest method. C. auris isolates revealed uniformly elevated fluconazole MICs (MIC50, 64 μg/ml), and an alarming percentage of isolates (37%) exhibited elevated caspofungin MICs by CLSI-BMD. Notably, 34% of C. auris isolates had coexisting elevated MICs (≥2 μg/ml) for both fluconazole and voriconazole, and 10% of the isolates had elevated coexisting MICs (≥2 μg/ml) to two additional azoles, i.e., posaconazole and isavuconazole. In contrast to reduced amphotericin B MICs by CLSI-BMD (MIC50, 1 μg/ml) for C. auris, elevated MICs were noted by Vitek 2 (MIC50, 8 μg/ml), which were statistically significant. Candida auris remains an unnoticed pathogen in routine microbiology laboratories, as 90% of the isolates characterized by commercial identification systems are misidentified as C. haemulonii. MALDI-TOF MS proved to be a more robust diagnostic technique for rapid identification of C. auris. Considering that misleading elevated MICs of amphotericin B by the Vitek AST-YS07 card may lead to the selection of inappropriate therapy, a cautionary approach is recommended for laboratories relying on commercial systems for identification and antifungal susceptibility testing of rare yeasts.
authors: Department of Medical Mycology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India.
authors: Shallu
authors: S
authors: Kathuria
authors: Department of Medical Mycology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India.
authors: Pradeep K
authors: PK
authors: Singh
authors: Department of Medical Mycology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India.
authors: Cheshta
authors: C
authors: Sharma
authors: Department of Medical Mycology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India.
authors: Anupam
authors: A
authors: Prakash
authors: Department of Medical Mycology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India.
authors: Aradhana
authors: A
authors: Masih
authors: Department of Microbiology, Amrita Institute of Medical Sciences & Research Centre, Kochi, Kerala, India.
authors: Anil
authors: A
authors: Kumar
authors: Department of Medical Microbiology and Infectious Diseases, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands Department of Medical Microbiology, Radboudumc, Nijmegen, The Netherlands.
authors: Jacques F
authors: http://orcid.org/0000-0003-3253-6080
authors: JF
authors: Meis
authors: Department of Medical Mycology, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India dranuradha@hotmail.com.
authors: Anuradha
authors: A
authors: Chowdhary
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology; D002175:Candida / Q000187:drug effects* / Q000235:genetics*; D002177:Candidiasis / Q000175:diagnosis* / Q000382:microbiology*; D004271:DNA, Fungal / Q000032:analysis / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D016533:Mycological Typing Techniques / Q000379:methods*; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D000935:Antifungal Agents; D004271:DNA, Fungal