Identification of Nocardia species using Autof MS 1000 and Bruker MALDI-TOF MS systems: A comparison

Abstract

Nocardia is an important cause of clinically invasive disease, but for most clinical laboratories, identification of these isolates to the species level is challenging. Recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been widely used for identification of most bacterial and fungal isolates. In this multicenter study, we evaluated the identification of Nocardia isolates using Autof MS1000 and Bruker Biotyper. A total of 86 non-duplicate Nocardia isolates from 7 hospital laboratories were evaluated. Further, we carried out sequence analysis of 16S rRNA, gyrB, secA1, hsp65, and rpoB genes as a reference method for Nocardia species identification. The 86 isolates were directly spotted on the target plate and plate protein extraction was performed. Data were analyzed by SPSS 19.0. In total, 72 (83.7%) strains (score [≥] 9.0) and 70 (81.4%) strains (score [≥] 2.0) were correctly identified by the Autof MS1000 and Bruker Biotyper systems, respectively, at the species level. There was no significant difference (P > 0.05) between the two systems using the same protein extraction method. In conclusion, the Autof MS 1000 and Bruker MALDI-TOF systems showed no difference in identification of Nocardia spp. to the species level and could meet the most important clinical requirement for species identification.