In-Feed Use of Heavy Metal Micronutrients in U.S. Swine Production Systems and Its Role in Persistence of Multidrug-Resistant Salmonellae

Abstract

The study aimed to characterize the role of heavy metal micronutrients in swine feed in emergence of heavy-metal-tolerant and multidrug-resistant Salmonella organisms. We conducted a longitudinal study in 36 swine barns over a 2-year period. The feed and fecal levels of Cu 2؉ and Zn 2؉ were measured. Salmonella was isolated at early and late finishing. MICs of copper sulfate and zinc chloride were measured using agar dilution. Antimicrobial susceptibility was tested using the Kirby-Bauer method, and 283 isolates were serotyped. We amplified pcoA and czcD genes that encode Cu 2؉

Microevolution of MonophasicSalmonellaTyphimurium during Epidemic, United Kingdom, 2005–2010

“…Concentration of heavy metals in pig intestines may represent substantial selective pressure contributing to the success of this clone. Indeed, a recent study reported that an enhanced MIC (20–24 mmol/L) compared with the baseline MIC (16 mmol/L) for copper sulfate was significantly more likely to be found in isolates from pig feces ( 30 ). …”

Alternatives to the use of antimicrobial agents in pig production: A multi-country expert-ranking of perceived effectiveness, feasibility and return on investment

“…Switzerland). It should also be taken into account that some negative characteristics due to the burden on the environment by excretion and to potential selection for specific antimicrobial resistance have been described in literature as well (Mavromichalis, 2011;Medardus et al, 2014) and might have influenced the opinion of the respondents. Furthermore some authors describe only partial effect of zinc oxide or only for a short period, leading to a less positive evaluation (Janczyk et al, 2013).…”

Co‐selection for antibiotic resistance genes is induced in a soil amended with zinc

“…The mechanisms employed by bacteria to protect against Zn include reducing absorption, increasing efficiency of efflux, transformation of toxic forms to low toxicity and internal isolation, some of which might cause resistance to antibiotics. There is compelling support for the notion that exposure to heavy metals can act as an indirect selective pressure for maintaining antibiotic resistance (Cesare, Eckert, & Corno, ; Hu, Wang, Li, Li, et al., ; Medardus et al., ). The co‐selection of heavy metal and ARGs in various ecological conditions, such as waters, sediments and soils, which increase the complexity of the ecological role of ARGs, and debases the effectiveness of prevention and control actions, has also been postulated to be an important element for the spread and persistence of ARGs (Hu, Wang, Li, Li, et al., ; Hu, Wang, Li, Shi, et al., ; Peltier et al., ; Seiler & Berendonk, ).…”