Mycobacterial identification using MALDI-ToF MS (MALDI) has been hindered by inadequate extraction methods. Adaptive Focused Acoustics™ uses concentrated ultrasonic energy to achieve cellular disruption. Using this technology, we developed a rapid mycobacterial inactivation/protein extraction method for MALDI-based identification. Agreement for identification to the species level versus conventional identification was stratified by log confidence cut-offs of ≥2.0, ≥ 1.8, or ≥1.7. A total of 182 mycobacterial isolates were tested. Complete inactivation of all species/strains was achieved after 2min. Using a log confidence cut-off of ≥2.0, overall agreement for the commercial method (CM) was 41.7% versus 66.7% for the novel method (NM). For the CM, agreement increased to 66.7% and 83.3% using log confidence cut-offs of ≥1.8 and ≥1.7, respectively; for the NM, agreement was 100% for both cut-offs with all isolates. With no alteration to the existing database, overall agreement for the NM was 83.4%, largely due to low scores for clinical isolates of M. chelonae and M. mucogenicum. Addition of spectra from a single clinical strain of each species to the existing database increased overall agreement to 93.1%.
Keywords: MALDI ToF MS; Mycobacterial identification; Ultrasonication.
Copyright © 2016. Published by Elsevier Inc.