title: Discrimination of multilocus sequence typing-based Campylobacter jejuni subgroups by MALDI-TOF mass spectrometry.
abstract: BACKGROUND
  Campylobacter jejuni, the most common bacterial pathogen causing gastroenteritis, shows a wide genetic diversity. Previously, we demonstrated by the combination of multi locus sequence typing (MLST)-based UPGMA-clustering and analysis of 16 genetic markers that twelve different C. jejuni subgroups can be distinguished. Among these are two prominent subgroups. The first subgroup contains the majority of hyperinvasive strains and is characterized by a dimeric form of the chemotaxis-receptor Tlp7(m+c). The second has an extended amino acid metabolism and is characterized by the presence of a periplasmic asparaginase (ansB) and gamma-glutamyl-transpeptidase (ggt).
  
  
  RESULTS
  Phyloproteomic principal component analysis (PCA) hierarchical clustering of MALDI-TOF based intact cell mass spectrometry (ICMS) spectra was able to group particular C. jejuni subgroups of phylogenetic related isolates in distinct clusters. Especially the aforementioned Tlp7(m+c)(+) and ansB+/ ggt+ subgroups could be discriminated by PCA. Overlay of ICMS spectra of all isolates led to the identification of characteristic biomarker ions for these specific C. jejuni subgroups. Thus, mass peak shifts can be used to identify the C. jejuni subgroup with an extended amino acid metabolism.
  
  
  CONCLUSIONS
  Although the PCA hierarchical clustering of ICMS-spectra groups the tested isolates into a different order as compared to MLST-based UPGMA-clustering, the isolates of the indicator-groups form predominantly coherent clusters. These clusters reflect phenotypic aspects better than phylogenetic clustering, indicating that the genes corresponding to the biomarker ions are phylogenetically coupled to the tested marker genes. Thus, PCA clustering could be an additional tool for analyzing the relatedness of bacterial isolates.
authors.affiliation: UMG-Labor/Institut für Medizinische Mikrobiologie, Universitätsmedizin Göttingen, Kreuzbergring 57, 37075, Göttingen, Germany. azautne@gwdg.de.
authors.forename: Andreas Erich
authors.initials: AE
authors.lastname: Zautner
authors.forename: Wycliffe Omurwa
authors.initials: WO
authors.lastname: Masanta
authors.forename: Abdul Malik
authors.initials: AM
authors.lastname: Tareen
authors.forename: Michael
authors.initials: M
authors.lastname: Weig
authors.forename: Raimond
authors.initials: R
authors.lastname: Lugert
authors.forename: Uwe
authors.initials: U
authors.lastname: Groß
authors.forename: Oliver
authors.initials: O
authors.lastname: Bader
mesh_terms: D015373:Bacterial Typing Techniques / Q000379:methods*; D016123:Campylobacter jejuni / Q000737:chemistry* / Q000145:classification* / Q000235:genetics; D016000:Cluster Analysis; D005838:Genotype; D058885:Multilocus Sequence Typing; D010641:Phenotype; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*