title: The broader context of antibiotic resistance: zinc feed supplementation of piglets increases the proportion of multi-resistant Escherichia coli in vivo.
abstract: Following the Europe-wide ban of antimicrobial growth promoters, feed supplementation with zinc has increased in livestock breeding. In addition to possible beneficial effects on animal health, feed supplementation with heavy metals is known to influence the gut microbiota and might promote the spread of antimicrobial resistance via co-selection or other mechanisms. As Escherichia coli is among the most important pathogens in pig production and often displays multi-resistant phenotypes, we set out to investigate the influence of zinc feed additives on the composition of the E. coli populations in vivo focusing on phylogenetic diversity and antimicrobial resistance. In a piglet feeding trial, E. coli were isolated from ileum and colon digesta of high dose zinc-supplemented (2500ppm) and background dose (50ppm) piglets (control group). The E. coli population was characterized via pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) for the determination of the phylogenetic background. Phenotypic resistance screening via agar disk diffusion and minimum inhibitory concentration testing was followed by detection of resistance genes for selected clones. We observed a higher diversity of E. coli clones in animals supplemented with zinc compared to the background control group. The proportion of multi-resistant E. coli was significantly increased in the zinc group compared to the control group (18.6% vs. 0%). For several subclones present both in the feeding and the control group we detected up to three additional phenotypic and genotypic resistances in the subclones from the zinc feeding group. Characterization of these subclones suggests an increase in antimicrobial resistance due to influences on plasmid uptake by zinc supplementation, questioning the reasonability of zinc feed additives as a result of the ban of antimicrobial growth promoters.
authors.affiliation: Institute of Microbiology and Epizootics, Freie Universität Berlin, Robert-von-Ostertag-Str. 7-13, 14163 Berlin, Germany. carmen.bednorz@fu-berlin.de
authors.forename: Carmen
authors.initials: C
authors.lastname: Bednorz
authors.forename: Kathrin
authors.initials: K
authors.lastname: Oelgeschläger
authors.forename: Bianca
authors.initials: B
authors.lastname: Kinnemann
authors.forename: Susanne
authors.initials: S
authors.lastname: Hartmann
authors.forename: Konrad
authors.initials: K
authors.lastname: Neumann
authors.forename: Robert
authors.initials: R
authors.lastname: Pieper
authors.forename: Astrid
authors.initials: A
authors.lastname: Bethe
authors.forename: Torsten
authors.initials: T
authors.lastname: Semmler
authors.forename: Karsten
authors.initials: K
authors.lastname: Tedin
authors.forename: Peter
authors.initials: P
authors.lastname: Schierack
authors.forename: Lothar H
authors.initials: LH
authors.lastname: Wieler
authors.forename: Sebastian
authors.initials: S
authors.lastname: Guenther
mesh_terms: D000821:Animal Feed; D000818:Animals; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004032:Diet / Q000379:methods*; D019587:Dietary Supplements; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D041981:Gastrointestinal Tract / Q000382:microbiology*; D005838:Genotype; D005858:Germany; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D013552:Swine; D015032:Zinc / Q000008:administration & dosage*
chemical_list: D015032:Zinc
keywords: Antimicrobial resistance; Co-selection; E. coli; Feed supplementation; Pigs; Zinc