jejuni isolate subgroups with differences in host adaptation and pathogenic potential, we used well-characterized C. jejuni isolates [18, 19] representing different phylogenetic groups. Especially the discrimination XAV-939 manufacturer of these isolates positive for the periplasmic gamma-glutamyl-transpeptidase (ggt) but negative for the PD-1/PD-L1 inhibitor fucose permease (fucP) associated with a higher rate of hospitalizations and bloody diarrhea [27] stood in the focus of this approach as compared to MLST and the estimated marker gene profiles in this
study. Results Classification results A total of 104 C. jejuni previously characterized and MLST-typed isolates of either human, bovine, chicken or turkey origin were re-identified using standard procedure ICMS. All isolates were identified as C. jejuni with MALDI Biotyper score values ≥2.000. PCA analysis of Campylobacter jejuni isolates In order to determine whether the C. jejuni isolate groups as defined by similar marker gene profiles could also be discriminated by their ICMS-spectra, the spectra obtained were clustered by PCA and their phyloproteomic relatedness analyzed. In all four biologically independent analyses we obtained comparable phylogenetic distances of the different isolates by PCA considering the existing degrees of freedom at particular dendrogram nodes (Figure 1).
Figure 1 Dendrogram based on relationships obtained from PCA analysis of the ICMS spectra. (A) Global cluster analysis of C. jejuni isolates. B1-3: Enlargement of major clusters, the overall majority of isolates is positive for the marker genes cj1365c, cj1585c, cj1321-6, fucP, cj0178, and cj0755 positive but dmsA-, ansB- and ggt-negative (different LY2835219 in vitro shades of yellow); B1: one cluster of dmsA +, ansB + but ggt – C. jejuni isolates in subtree Ia and a second
cluster of dmsA+, ansB+ but ggt- C. jejuni isolates in subtree Ib (blue & violet); cluster of CC 53 & CC 61 isolates with the dimeric form of the formic acid specific chemotaxis receptor Tlp7m+c (beige); cluster of Tlp7m+c + CC 21 isolates C-X-C chemokine receptor type 7 (CXCR-7) – all of bovine origin (orange); B2: small cluster of dmsA + and cstII + isolates belonging to MLST-CC 1034 (teal) B3: The cluster of ggt + isolates splits in two subclusters, which differ in cj1365c and cstII (dark and light blue). The relatedness of C. jejuni isolates in the ICMS spectra-based PCA-tree reflects the isolates subgroup affiliation & MLST CC/ST. With only four singular outliners, isolates positive for dmsA and ansB formed distinct groups within the subclusters Ia, Ib1, and IIb (Figure 1). The corresponding marker gene profiles revealed that nearly all dmsA and ansB positive isolates in subclusters Ia and Ib1 were ggt-negative, whereas nearly all ggt-positive isolates formed a combined subcluster IIb2 + IIb3 (Additional file 1: Table S1). Isolates in cluster IIb2 were typically cstII and cj1365c negative, whereas IIb3 isolates were typically positive for these two genetic markers.