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Volume 31, Number 10—October 2025

Dispatch

Genetic Cluster of Extended-Spectrum β-lactamase–Producing Klebsiella pneumoniae in Humans and Food, Switzerland, 2018–2019

Lisandra Aguilar-Bultet1, Elena Gómez-Sanz1, Isabelle Vock, Monica Alt, Ruth Schindler, Laura Maurer Pekerman, Reto Furger, Lucas Eichenberger, Ingrid Steffen, Ana B. García-Martín, Tanja Stadler, Claudia Bagutti, and Sarah Tschudin-SutterComments to Author 
Author affiliation: University Hospital Basel, University of Basel, Basel, Switzerland (L. Aguilar-Bultet, E. Gómez-Sanz, I. Vock, R. Schindler, L. Maurer Pekerman, A.B. García-Martín, S. Tschudin-Sutter); Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland (E. Gómez-Sanz); State Laboratory Basel-City, Basel (M. Alt, R. Furger, L. Eichenberger, C. Bagutti); Rothen Laboratory, Basel (I. Steffen); ETH Zurich, Basel (T. Stadler); Swiss Institute of Bioinformatics, Basel (T. Stadler)

Main Article

Figure 2

Phylogeny and related plasmids detected in ESBL–producing Klebsiella pneumoniae in human and food samples, Switzerland, 2018–2019. A) MST of 972 Klebsiella pneumoniae sequence type 14 international samples based on core-genome multilocus sequence typing (cgMLST) profiles (K. pneumoniae sensu lato cgMLST version 1.0 in SeqSphere+ version 9.0.0 [Ridom, https://www.ridom.de]). Inset image shows detail the mixed MST cluster 22. Color-filled circles denote the different geographic origin. Isolates of the same cluster (<15 allelic differences) are surrounded by a colored shadow. Numbers in connecting lines represent allelic distance values. B) Circular BLAST Ring Image Generator (BRIG, https://github.com/happykhan/BRIG) comparison of the ESBL plasmids from isolates in this study. Plasmid pWP2-W18-ESBL-06_2 (accession no. NZ_AP021931; blue ring) was identified as the closest hit in the PLSDB database version 2023_11_03_v2 (Universität des Saarlands, https://ccb-microbe.cs.uni-saarland.de/plsdb2025). Plasmid of the food isolate (F0067) ESBL-producing K. pneumoniae shown in green. Patient A isolate (P0745) shown in pink ring; patient B isolate (P1134) shown in orange ring. Brown-gray rings show short-read assembly from isolates GCA_21938715 and GCA_021820535 from the University Hospital Jena, Jena, Germany. Color intensity of concentric rings represents percent identity to the reference plasmid, pWP2-W18-ESBL-06_2. GC content and plasmid length are displayed as inner rings. Outer rings show antimicrobial resistance genes (red font), replicons (black font), and IS and Tn (blue font) sequences. ESBL, extended-spectrum β-lactamase; IS, insertion sequence; MST, minimum spanning tree; Tn, transposon.

Figure 2. Phylogeny and related plasmids detected in ESBL–producing Klebsiella pneumoniae in human and food samples, Switzerland, 2018–2019. A) MST of 972 Klebsiella pneumoniae sequence type 14 international samples based on core-genome multilocus sequence typing (cgMLST) profiles (K. pneumoniae sensu lato cgMLST version 1.0 in SeqSphere+ version 9.0.0 [Ridom, https://www.ridom.de]). Inset image shows detail the mixed MST cluster 22. Color-filled circles denote the different geographic origin. Isolates of the same cluster (<15 allelic differences) are surrounded by a colored shadow. Numbers in connecting lines represent allelic distance values. B) Circular BLAST Ring Image Generator (BRIG, https://github.com/happykhan/BRIG) comparison of the ESBL plasmids from isolates in this study. Plasmid pWP2-W18-ESBL-06_2 (accession no. NZ_AP021931; blue ring) was identified as the closest hit in the PLSDB database version 2023_11_03_v2 (Universität des Saarlands, https://ccb-microbe.cs.uni-saarland.de/plsdb2025). Plasmid of the food isolate (F0067) ESBL-producing K. pneumoniae shown in green. Patient A isolate (P0745) shown in pink ring; patient B isolate (P1134) shown in orange ring. Brown-gray rings show short-read assembly from isolates GCA_21938715 and GCA_021820535 from the University Hospital Jena, Jena, Germany. Color intensity of concentric rings represents percent identity to the reference plasmid, pWP2-W18-ESBL-06_2. GC content and plasmid length are displayed as inner rings. Outer rings show antimicrobial resistance genes (red font), replicons (black font), and IS and Tn (blue font) sequences. ESBL, extended-spectrum β-lactamase; IS, insertion sequence; MST, minimum spanning tree; Tn, transposon.

Main Article

1These first authors contributed equally to this article.

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