Antimicrobial use in swine production and its effect on the swine gut microbiota and antimicrobial resistance

Abstract

Antimicrobials have been used in swine production at subtherapeutic levels since the early 1950s to increase feed efficiency and promote growth. In North America, a number of antimicrobials are available for use in swine. However, the continuous administration of subtherapeutic, low concentrations of antimicrobials to pigs also provides selective pressure for antimicrobial-resistant bacteria and resistance determinants. For this reason, subtherapeutic antimicrobial use in livestock remains a source of controversy and concern. The swine gut microbiota demonstrates a number of changes in response to antimicrobial administration depending on the dosage, duration of treatment, age of the pigs, and gut location that is sampled. Both culture-independent and -dependent studies have also shown that the swine gut microbiota contains a large number of antimicrobial resistance determinants even in the absence of antimicrobial exposure. Heavy metals, such as zinc and copper, which are often added at relatively high doses to swine feed, may also play a role in maintaining antimicrobial resistance and in the stability of the swine gut microbiota. This review focuses on the use of antimicrobials in swine production, with an emphasis on the North American regulatory context, and their effect on the swine gut microbiota and on antimicrobial resistance determinants in the gut microbiota.

Colistin in Pig Production: Chemistry, Mechanism of Antibacterial Action, Microbial Resistance Emergence, and One Health Perspectives

“…Heavy metals such as zinc are widely used in pigs, especially for the control of PWD in combination with colistin, and is incorporated into swine feed at levels of 125–3000 mg/kg of feed (Holman and Chénier, 2015). Zinc oxide fed at pharmacological levels reduces diarrhea and mortality and improves growth in pigs (Fairbrother et al, 2005).…”

“…However, there are two major concerns regarding the use of ZnO in swine. On the one hand, there is environmental pollution because of the high levels of supplementation, and on the other there is co-selection and co-resistance where antibiotic resistance genes (ARGs) are located on the same mobile genetic element as ZnO resistance genes (Holman and Chénier, 2015). To the best of our knowledge, no study has investigated whether or not resistance genes associated with colistin and heavy metals could be carried on the same mobile genetic element.…”

Antimicrobial usage and resistance in beef production

“…Copper and zinc promote growth, potentially via suppression of pathogens and alteration of microbiota [176, 177]. In other production animals, zinc and copper can select for AMR [178]. This may be due in part to MGEs such as ICE, in which AMR determinants are co-localized with heavy-metal resistance genes.…”

Supplementation of pigs diet with zinc and copper as alternative to conventional antimicrobials

“…The results of a study by Agga et al (2015) obtained on weaned pigs fed 3 weeks copper sulfate (125 mg Cu/kg feed) suggest that Cu supplementation may have significant impact on certain gens expression. The prolonged use of heavy metals such as Zn and Cu provides selective pressure on antimicrobial-resistant bacteria and this is a reason why implementation of high doses of these metals may play a role in maintaining of antimicrobial resistance (Holman and Chenier 2015).…”