title: Identification and differentiation of food-related bacteria: A comparison of FTIR spectroscopy and MALDI-TOF mass spectrometry.
abstract: The food industry requires easy, accurate, and cost-effective techniques for microbial identification to ensure safe products and identify microbial contaminations. In this work, FTIR spectroscopy and MALDI-TOF mass spectrometry were assessed for their suitability and applicability for routine microbial diagnostics of food-related microorganisms by analyzing their robustness according to changes in incubation time and medium, identification accuracy and their ability to differentiate isolates down to the strain level. Changes in the protocol lead to a significantly impaired performance of FTIR spectroscopy, whereas they had only little effects on MALDI-TOF MS. Identification accuracy was tested using 174 food-related bacteria (93 species) from an in-house strain collection and 40 fresh isolates from routine food analyses. For MALDI-TOF MS, weaknesses in the identification of bacilli and pseudomonads were observed; FTIR spectroscopy had most difficulties in identifying pseudomonads and enterobacteria. In general, MALDI-TOF MS obtained better results (52-85% correct at species level), since the analysis of mainly ribosomal proteins is more robust and seems to be more reliable. FTIR spectroscopy suffers from the fact that it generates a whole-cell fingerprint and intraspecies diversity may lead to overlapping species borders which complicates identification. In the present study values between 56% and 67% correct species identification were obtained. On the opposite, this high sensitivity offers the opportunity of typing below the species level which was not possible using MALDI-TOF MS. Using fresh isolates from routine diagnostics, both techniques performed well with 88% (MALDI-TOF) and 75% (FTIR) correct identifications at species level, respectively.
authors.affiliation: Abteilung Mikrobiologie, Zentralinstitut für Ernährungs-und Lebensmittelforschung (ZIEL), Technische Universität München, Weihenstephaner Berg 3, 85350 Freising, Germany. Electronic address: mareike.wenning@wzw.tum.de.
authors.forename: Mareike
authors.initials: M
authors.lastname: Wenning
authors.affiliation: Abteilung Mikrobiologie, Zentralinstitut für Ernährungs-und Lebensmittelforschung (ZIEL), Technische Universität München, Weihenstephaner Berg 3, 85350 Freising, Germany; Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit (LGL), Veterinärstraße 2, 85764 Oberschleißheim, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Breitenwieser
authors.affiliation: Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit (LGL), Veterinärstraße 2, 85764 Oberschleißheim, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Konrad
authors.affiliation: Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit (LGL), Veterinärstraße 2, 85764 Oberschleißheim, Germany.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Huber
authors.affiliation: Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit (LGL), Veterinärstraße 2, 85764 Oberschleißheim, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Busch
authors.affiliation: Abteilung Mikrobiologie, Zentralinstitut für Ernährungs-und Lebensmittelforschung (ZIEL), Technische Universität München, Weihenstephaner Berg 3, 85350 Freising, Germany; Lehrstuhl für Mikrobielle Ökologie, Department of Biosciences, Technische Universität München, D-85350 Freising, Germany.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Scherer
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D015373:Bacterial Typing Techniques; D003470:Culture Media; D016208:Databases, Factual; D005516:Food Microbiology; D005798:Genes, Bacterial; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003470:Culture Media
keywords: FTIR spectroscopy; MALDI-TOF mass spectrometry; Species identification; Strain typing