Rapid and reliable discrimination between Shigella species and Escherichia coli using MALDI-TOF mass spectrometry.
E. coli-Shigella species are a cryptic group of bacteria in which the Shigella species are distributed within the phylogenetic tree of E. coli. The nomenclature is historically based and the discrimination of these genera developed as a result of the epidemiological need to identify the cause of shigellosis, a severe disease caused by Shigella species. For these reasons, this incorrect classification of shigellae persists to date, and the ability to rapidly characterize E. coli and Shigella species remains highly desirable. Until recently, existing matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) assays used to identify bacteria could not discriminate between E. coli and Shigella species. Here we present a rapid classification method for the E. coli-Shigella phylogroup based on MALDI-TOF MS which is supported by genetic analysis. E. coli and Shigella isolates were collected and genetically characterized by MLVA. A custom reference library for MALDI-TOF MS that represents the genetic diversity of E. coli and Shigella strains was developed. Characterization of E. coli and Shigella species is based on an approach with Biotyper software. Using this reference library it was possible to distinguish between Shigella species and E. coli. Of the 180 isolates tested, 94.4% were correctly classified as E. coli or shigellae. The results of four (2.2%) isolates could not be interpreted and six (3.3%) isolates were classified incorrectly. The custom library extends the existing MALDI-TOF MS method for species determination by enabling rapid and accurate discrimination between Shigella species and E. coli.
Department of CBRN Protection, TNO, PO Box 45, 2280 AA Rijswijk, The Netherlands. Electronic address: armand.paauw@tno.nl.
Armand
A
Paauw
Cluster of Infectious Diseases, Public Health Service Amsterdam, PO Box 2200, 1000 CE Amsterdam, The Netherlands.
Debby
D
Jonker
Department of CBRN Protection, TNO, PO Box 45, 2280 AA Rijswijk, The Netherlands.
Guus
G
Roeselers
Department of CBRN Protection, TNO, PO Box 45, 2280 AA Rijswijk, The Netherlands.
Jonathan M E
JM
Heng
Department of CBRN Protection, TNO, PO Box 45, 2280 AA Rijswijk, The Netherlands.
Roos H
RH
Mars-Groenendijk
Department of CBRN Protection, TNO, PO Box 45, 2280 AA Rijswijk, The Netherlands.
Hein
H
Trip
Department of CBRN Protection, TNO, PO Box 45, 2280 AA Rijswijk, The Netherlands.
E Margo
EM
Molhoek
Expert Centre Force Health Protection, Ministry of Defence, PO Box 185, MPC 56A, 3940 AD, Doorn, The Netherlands.
Hugo-Jan
HJ
Jansen
Expert Centre Force Health Protection, Ministry of Defence, PO Box 185, MPC 56A, 3940 AD, Doorn, The Netherlands.
Jan
J
van der Plas
Department of CBRN Protection, TNO, PO Box 45, 2280 AA Rijswijk, The Netherlands.
Ad L
AL
de Jong
Department of CBRN Protection, TNO, PO Box 45, 2280 AA Rijswijk, The Netherlands.
Joanna A
JA
Majchrzykiewicz-Koehorst
Cluster of Infectious Diseases, Public Health Service Amsterdam, PO Box 2200, 1000 CE Amsterdam, The Netherlands; Naturalis Biodiversity Centre, Sylviusweg 72, 2333 BE Leiden, The Netherlands.
Arjen G C L
AG
Speksnijder
D001431:Bacteriological Techniques / Q000379:methods*; D004926:Escherichia coli / Q000737:chemistry* / Q000145:classification*; D006801:Humans; D058889:Molecular Typing; D012760:Shigella / Q000737:chemistry* / Q000145:classification* / Q000235:genetics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013997:Time Factors
Bruker; Discrimination; Escherichia coli; MALDI-TOF; Mass spectrometry; Shigella species