Comparison of two Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Methods with Conventional Phenotypic Identification for Routine Bacterial Speciation

Bacterial identification relies primarily on culture-based methodologies requiring 24h for isolation and an additional 24-48h for speciation. Matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS) is an emerging technology newly applied to the problem of bacterial speciation. We evaluated two MALDI-TOF MS systems (MS) on 720 consecutively isolated bacterial colonies, in routine clinical laboratory conditions. Isolates were analyzed in parallel on both devices, using the manufacturers’ default recommendations. We compared MS with conventional biochemical test system identifications. Discordant results were resolved with “gold standard” 16S rDNA gene sequencing. The first MS (Bruker) gave high confidence identifications for 680 isolates of which 674 (99.1%) were correct; the second MS (Shimadzu) gave high confidence identifications for 639 isolates, of which 635 (99.4%) were correct. Had MS been used for initial testing, and biochemical identification used only in the absence of high confidence MS identifications, the laboratory would have saved approximately US$5 per isolate in marginal costs and reduced average turnaround time by more than an 8 hour shift, with no loss in accuracy. Our data suggest that implementation of MS as a first test strategy for one step speciation would improve timeliness and reduce isolate identification costs in clinical bacteriology laboratories now. on O cber 1, 2017 by gest ht://jcm .sm .rg/ D ow nladed fom