Rapid Classification and Identification of Salmonellae at the Species and Subspecies Levels by Whole-Cell Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

Abstract

Variations in the mass spectral profiles of multiple housekeeping proteins of 126 strains representing Salmonella enterica subsp. enterica (subspecies I), S. enterica subsp. salamae (subspecies II), S. enterica subsp. arizonae (subspecies IIIa), S. enterica subsp. diarizonae (subspecies IIIb), S. enterica subsp. houtenae (subspecies IV), and S. enterica subsp. indica (subspecies VI), and Salmonella bongori were analyzed to obtain a phylogenetic classification of salmonellae based on whole-cell matrix-assisted laser desorption ionization-time of flight mass spectrometric bacterial typing. Sinapinic acid produced highly informative spectra containing a large number of biomarkers and covering a wide molecular mass range (2,000 to 40,000 Da). Genus-, species-, and subspecies-identifying biomarker ions were assigned on the basis of available genome sequence data for Salmonella, and more than 200 biomarker peaks, which corresponded mainly to abundant and highly basic ribosomal or nucleic acid binding proteins, were selected. A detailed comparative analysis of the biomarker profiles of Salmonella strains revealed sequence variations corresponding to single or multiple amino acid changes in multiple housekeeping proteins. The resulting mass spectrometry-based bacterial classification was very comparable to the results of DNA sequence-based methods. A rapid protocol that allowed identification of Salmonella subspecies in minutes was established.

Application of Whole-Cell Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for Rapid Identification and Clustering Analysis ofPantoeaSpecies

“…Whole-cell matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (31) is an emerging technology for identification of bacteria (26,46), fungi (17,33), viruses (29,51), insects (41), and helminths (42). MALDI-TOF MS-based identification can accurately resolve bacterial identity at the genus, species, and in some taxa subspecies levels (e.g., Salmonella enterica serovars, Listeria genotypes) (1,18). Identity is based on unique mass/charge ratio (m/z) fingerprints of proteins, which are ionized using short laser pulses directed to bacterial cells obtained from a single colony embedded in a matrix.…”

Einsatz der Matrix-Assisted Laser Desorption/ionisation-Time of Flight Massenspektrometrie (MALDI-TOF MS) in der mikrobiologischen Routinediagnostik/Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in clinical microbiological routine diagnostics

“…Anders als bei den biochemischen Testsystemen handelt es sich beim MALDI-TOF MS-System um ein offenes, bei dem die Datenbank auch vom Anwender eigenst ä ndig erweitert werden kann. Durch entsprechende Erg ä nzungen der Referenz-Spektren der Datenbanken konnte eine nahezu 100 % Identifi zierungsrate von Neisserien [11] , Clostridien [12] , Mycobakterien [13] , Salmonellen [14] , vergr ü nenden Streptokokken [15] und Helicobacter pylori [16] erreicht werden. W ä hrend das MALDI-TOF MS-System im Vergleich zu biochemischen Testsystemen im Bereich der Differenzierung von Enterobakterien, Staphylokokken und Streptokokken vergleichbar gute Ergebnisse liefert, zeigt es deutliche Vorteile bei der Differenzierung von Gram-positiven St ä bchen [17] , Anaerobiern und einigen Nonfermentern [18,19] .…”

Salmonella Türlerinin Hızlı Tanısında Kromojenik Besiyeri İle Birlikte “Matrix-Assisted Laser Desorption Ionization - Time of Flight Mass Spectrometry” Yönteminin Phoenix Otomatize Sistemi ile Kıyaslanması

“…Salmonella türleri çevrede çok fazla miktarlarda bulunmakta ve belli bazı konak faktörleri insanları enfeksiyona karşı duyarlı kılmaktadır. Tüm dünyada prevalansı, virülansı ve çevreye uyum sağlayabilirliği ile birlikte antibiyotiklere karşı direnci de artış göstermektedir 4 .…”