Impact of added copper, alone or in combination with chlortetracycline, on growth performance and antimicrobial resistance of fecal enterococci of weaned piglets

Abstract

Studies suggest a link between added copper (Cu) and co-selection of antimicrobial resistance (AMR) in Enterococcus spp., but data are inconsistent. This study aimed to assess the impact of added Cu, alone or with a feed-grade antimicrobial, on growth performance, transferable Cu resistance gene (tcrB) prevalence, abundance of tcrB in fecal community DNA, and AMR in fecal enterococci in weaned piglets. A total of 320 barrows (DNA 200 × 400, DNA Genetics) weaned at approximately 21 d of age with 7.4 kg (7.4 ± 0.06 kg) BW were used in a 28-d study. Piglets were fed a common non-medicated diet for 7 d of acclimation. Treatments were arranged in a 2 × 2 factorial design with main effects of added Cu (0 vs. 200 mg/kg Cu from Cu sulfate) and chlortetracycline (0 vs. 440 mg/kg CTC). Growth performance and fecal samples were obtained on days 0, 14, and 28. There was no evidence (P > 0.05) for Cu and CTC interaction in growth performance. Pigs fed diets with added Cu had increased (P < 0.05) ADG and ADFI from days 0 to 14, with no evidence for differences (P > 0.05) from days 15 to 28 and 0 to 28. Pigs fed diets with CTC had improved (P < 0.01) ADG, ADFI, and G:F from days 0 to 28. Prevalence of tcrB-positive enterococci was not affected by the addition of Cu and/or CTC (P > 0.05). Prevalence of tcrB-positive enterococci was higher on day 14 than other sampling days (P = 0.002). Prevalence of tetracycline resistance gene [tet(M)]-positive enterococci was not affected by treatments or day (P > 0.05). Prevalence of macrolide resistance gene [erm(B)]-positive enterococci had a significant treatment and sampling day interaction (P = 0.021). The abundance of the tcrB gene in feces, quantified by PCR, was not affected by Cu treatment. The median Cu minimum inhibitory concentrations (MIC) of tcrB-negative and -positive isolates were 3 and 20 mM, respectively (P < 0.001). For day 0 and day 28, all Enterococcus isolates were susceptible to gentamicin, kanamycin, streptomycin, daptomycin, and tigecycline, with a majority of isolates resistant to chloramphenicol, erythromycin, lincomycin, linezolid, tetracycline, tylosin tartrate, and Synercid. In conclusion, 200 mg/kg added Cu or 440 mg/kg CTC in nursery diets improved growth performance of nursery pigs. Added Cu, with or without a selection pressure of CTC, did not increase Cu-resistant enterococci and did not co-select resistance to antibiotics.

Effects of chlortetracycline on growth performance and intestinal functions in weaned piglets

“…Our results are consistent with the study of Wang et al (2019) who investigated that administration with 75 mg/kg CTC did not affect average daily gain and feed efficiency in weaned piglets. However, a high concentration of CTC, such as 400 and 440 mg/kg CTC, could improve average daily gain, feed intake, and body weight in weaned piglets (Capps et al, 2020; Williams et al, 2018). Thus, we speculated that these different effects of CTC might be partially due to the dosage of CTC.…”

Genomic Insights of Enterococcus faecium UC7251, a Multi-Drug Resistant Strain From Ready-to-Eat Food, Highlight the Risk of Antimicrobial Resistance in the Food Chain

“…Susceptibility toward copper (Cu), zinc (Zn), cadmium (Cd), and mercury (Hg) was tested, as previously described (Sharifi et al, 2015 ; Capps et al, 2020 ). Briefly, overnight cultures were spotted onto Mueller–Hinton agar (Oxoid) supplemented with different concentrations (0.05 to 40 mM) of ZnCl 2 (Carlo Erba), HgCl 2 (Sigma Aldrich), and CdSO 4 (Sigma Aldrich) resuspended in distilled water, and CuSO4 (Merck Millipore) adjusted to pH 7.2 with 1 M NaOH.…”

Trace metals and animal health: Interplay of the gut microbiota with iron, manganese, zinc, and copper

“…Although copper can prevent bacterial growth, some bacterial species can tolerate high levels of copper by acquiring copper-resistance genes via horizontal gene transfer ( Davison, 1999 ). However, the link between antimicrobial resistance development and increased copper supplementation has been inconsistent, as other studies reported that copper did not increase copper-resistant bacteria in pigs ( Agga et al., 2014 ; Capps et al., 2020 ).…”