The value of MALDI-TOF MS for the identification of clinically relevant anaerobic bacteria in routine laboratories

Abstract

Between 2010 and 2011, 283 clinically relevant non-duplicate anaerobic isolates were analysed by MALDI-TOF MS and the results were compared with conventional identification. Immediately after isolation, an ethanol precipitation was carried out on isolated colonies and the stabilized samples were anonymized and sent to the laboratory of Bruker Daltonik, Bremen, Germany, where the identification was done using the standard protocol for micro-organism identification on a Microflex LT mass spectrometer equipped with the MALDI Biotyper 3.0 software. Of 283 isolates, 218 (77 %) were identified at species level [log(score) ¢2.0], 31 isolates (10.95 %) were identified at genus level [log(score) 1.7-2.0] and 34 (12 %) gave non-reliable identification [log(score) ,1.7]. Out of the 31 isolates with log(score) 1.7-2.0, in the case of 24 isolates the species name given by the MALDI Biotyper was accepted if it was the same as for the classical identification. Of 218 isolates identified at species level, 40 results were discordant with phenotypic identification, and of the 31 isolates identified at genus level according to the manufacturer's score cut-off, four gave results discordant with the phenotypic method. For the 44 discordant results, 16S rRNA gene sequencing confirmed MALDI-TOF MS identification in 41 cases, leaving three isolates (0.7 %) that had been misidentified by MALDI-TOF MS.

Comparison of two matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry methods and API 20AN for identification of clinically relevant anaerobic bacteria

“…the Bruker MS gave the correct identification to both genus and species level, but according to the manufacturer's instructions, we can depend on their identification to the genus level only. This is in contrast to a recent report by Nagy et al (2012), who could identify 218/ 283 (77 %) isolates to species level (with score ¢2.0) and 31/ 283 of isolates (10.95 %) to genus level (with score 1.7-2.0) and 34 isolates (12 %) gave no reliable identification (score ,1.7). Another group (Schmitt et al, 2012) found that correct genus identification could be achieved for 57 % (120/ 209) of anaerobes with score .2.0, and correct species identification was achieved for 80 % (168/209) of the isolates.…”

“…Bruker MS (Microflex; Bruker Daltoniks), VITEK MS (bioMérieux) and Shimadzu MS (AXIMA; Shimadzu Corporation). They are used to identify aerobic and anaerobic bacteria (Fedorko et al, 2012;Nagy et al, 2009Nagy et al, , 2012van Veen et al, 2010;Veloo et al, 2011b), mycobacteria (Saleeb et al, 2011), Nocardia (Verroken et al, 2010) and yeasts (van Veen et al, 2010) isolated on solid media from clinical specimens. MALDI-TOF MS has also been recently used for the identification of bacteria and yeasts directly from positive blood culture bottles (Ferroni et al, 2010;Stevenson et al, 2010).…”

High-throughput discrimination of bacteria isolated fromAstacus astacusandA. leptodactylus

“…When comparing the performance of MALDI-TOF MS with conventional and API systems for clinical isolates of human material, the percentage of correct identifications is significantly higher than in this work, mainly due to the customized databases (Bizzini et al, 2010;Dupont et al, 2010;Risch et al, 2010;Martiny et al, 2011;Saffert et al, 2011;El-Bouri et al, 2012;Nagy et al, 2012;Campos Braga et al, 2013;Kierzkowska et al, 2013). For example, 97.2% of isolates had identical genus identification by both methods, while 79.9% yielded exactly the same species identification in the work of van Veen et al (2010), and conventional methods also resulted in fewer species identification (83.1% versus 92% MALDI-TOF MS).…”

Identification of Anaerobic Bacteria by Bruker Biotyper Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry with On-Plate Formic Acid Preparation

“…Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) has been used predominantly for aerobic bacterial identification and is now in use in many clinical laboratories (1)(2)(3)(4)(5). A small number of studies have preliminarily evaluated this technology for identification of anaerobic bacteria (4,(6)(7)(8)(9)(10)(11)(12), but this application is not in widespread clinical use.…”