Publikationsdatenbank

The influence of high dietary zinc feeding on antimicrobial resistance of intestinal Escherichia coli (2018)

Art

Hochschulschrift

Autor

Ciesinski, Lisa (WE 7)

Quelle

Berlin: Mensch und Buch Verlag Berlin, 2018 — VI, 104 Seiten

ISBN: 978-3-86387-938-9

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/23557

Kontakt

Institut für Mikrobiologie und Tierseuchen

Robert-von-Ostertag-Str. 7-13
14163 Berlin
+49 30 838 51843 / 66949
mikrobiologie@vetmed.fu-berlin.de

Abstract / Zusammenfassung

The usage of feed additives to increase growth performance and health in livestock is very common. For pigs, zinc oxide in concentrations ranging from 2000 – 3000 mg zinc/kg diet is often used after weaning. However, more and more evidence exists that high dietary zinc feeding is associated with the emergence of antimicrobial resistant bacteria in the pigs. As antimicrobial resistant bacteria represent a worldwide problem for human and veterinary medicine, it was necessary to shed further light into this highly important area. This study focuses on E. coli, a highly variable bacterial species which is ubiquitously distributed, colonizes the intestine of warm-blooded animals, birds, and reptiles and is of clinical relevance as beside commensal strains also pathogenic ones of intestinal and extraintestinal pathogenicity exist. For pigs E. coli represent an important infectious agent for diarrhea of suckling and weaned piglets which lead to large economic losses in the pig industry. In the first part of this study, a zinc pig feeding trial was performed, focusing on in-depth analysis of antimicrobial resistant E. coli. For three different habitats (feces, digesta, and mucosa), absolute E. coli numbers were investigated at different time points around weaning for the zinc and the control group. For 2665 isolates, phenotypic antimicrobial resistance was determined and confirmed by minimum inhibitory concentration testing for random samples. Finally, whole genome sequencing and multi-locus sequence typing were performed for random samples of porcine isolates. In piglets of the zinc group, a substantial increase of multi-resistant E. coli was detected in all gut habitats tested, ranging from 28.9-30.2% multi-resistant E. coli compared to 5.8-14.0% in the control group. This zinc effect was independent of the total number of E. coli, for which a general decrease over time was determined for both groups. The higher resistance rates of the zinc group, therefore, seem to be linked with persistence of the resistant population under the influence of high dietary zinc feeding. Interestingly, mainly isolates of two different phylogenetic clusters namely ST10 and ST34 are involved in the increased resistance of the zinc group. In the second part of this study, conjugation experiments were performed to investigate if bacterial conjugation is influenced by zinc and therefore, plays a role for the detected increased resistance under high dietary zinc feeding. Values for colony forming units and conjugation rates were investigated for two different recipient/donor combinations. For in vivo experiments with gnotobiotic mice, feces were investigated daily over 20 days, and caecum digesta and small intestine digesta were examined to complement the analysis. In addition four different zinc concentrations were tested in vitro. Overall, some results indicate that zinc decreases the bacterial conjugation. However, results were very versatile and not all results support this suggestion. Therefore, an increasing effect of high dietary zinc feeding on plasmid exchange is unlikely. In conclusion, results of this study further corroborate recent reports on the association of high dietary zinc feeding with antimicrobial resistance. Both parts of this study point toward a situation where mainly the phylogenetic background of the plasmid host bacteria is of importance for the increased resistance and an increased plasmid exchange plays only a minor role. Although the mechanism by which high dietary zinc feeding leads to the increased resistance is still not clear, this study with the clear focus on resistance confirms the hypothesis that high dietary zinc feeding is no acceptable alternative to antimicrobial growth promoters. The usage of high dietary zinc feeding should therefore be stopped.