Multicenter Evaluation of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectroscopy-Based...

Fourier transform infrared (FTIR) spectroscopy has demonstrated applicability as a reagent-free whole-organism fingerprinting technique for both microbial identification and strain typing. For routine application of this technique in microbiology laboratories, acquisition of FTIR spectra in the attenuated total reflectance (ATR) mode simplifies the FTIR spectroscopy workflow, providing results within minutes after initial culture without prior sample preparation. In our previous central work, 99.7% correct species identification of clinically relevant yeasts was achieved by employing an ATR-FTIR-based method and spectral database developed by our group. In this study, ATR-FTIR spectrometers were placed in 6 clinical microbiology laboratories over a 16-month period and were used to collect spectra of routine yeast isolates for on-site identification to the species level. The identification results were compared to those obtained from conventional biochemical tests and/or matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Isolates producing discordant results were reanalyzed by routine identification methods, ATR-FTIR spectroscopy, and PCR gene sequencing of the D1/D2 and internal transcribed spacer (ITS) regions. Among the 573 routine clinical yeast isolates collected and identified by the ATR-FTIR-based method, 564 isolates (98.4%) were correctly identified at the species level, while the remaining isolates were inconclusive with no misidentifications. Due to the low prevalence of Candida auris in routine isolates, additional randomly selected C. auris (n = 24) isolates were obtained for evaluation and resulted in 100% correct identification. Overall, the data obtained in our multicenter evaluation study using multiple spectrometers and system operators indicate that ATR-FTIR spectroscopy is a reliable, cost-effective yeast identification technique that provides accurate and timely (∼3 min/sample) species identification promptly after the initial culture.