Heavy metal driven co-selection of antibiotic resistance in soil and water bodies impacted by agriculture and aquaculture

TLDR

The ban on antibiotic growth promoters in animal husbandry has reduced resistance, yet heavy metals used in farming and aquaculture can also co‑select for antibiotic resistance, making environmental background essential to consider. The study reviews heavy‑metal pollution, toxicity, tolerance, and co‑selection mechanisms to identify metals that may drive antibiotic resistance in soil and water. The authors examined available data on heavy‑metal pollution, toxicity, tolerance, and co‑selection mechanisms, and assessed the risk of metal‑driven co‑selection based on environmentally relevant concentrations. Analyses indicate that agriculture and aquaculture release moderately to highly toxic metals (Hg, Cd, Cu, Zn) that, at critical concentrations, can trigger co‑selection of antibiotic resistance, and future studies should focus on these metals.

Abstract

The use of antibiotic agents as growth promoters was banned in animal husbandry to prevent the selection and spread of antibiotic resistance. However, in addition to antibiotic agents, heavy metals used in animal farming and aquaculture might promote the spread of antibiotic resistance via co-selection. To investigate which heavy metals are likely to co-select for antibiotic resistance in soil and water, the available data on heavy metal pollution, heavy metal toxicity, heavy metal tolerance, and co-selection mechanisms was reviewed. Additionally, the risk of metal driven co-selection of antibiotic resistance in the environment was assessed based on heavy metal concentrations that potentially induce this co-selection process. Analyses of the data indicate that agricultural and aquacultural practices represent major sources of soil and water contamination with moderately to highly toxic metals such as mercury (Hg), cadmium (Cd), copper (Cu), and zinc (Zn). If those metals reach the environment and accumulate to critical concentrations they can trigger co-selection of antibiotic resistance. Furthermore, co-selection mechanisms for these heavy metals and clinically as well as veterinary relevant antibiotics have been described. Therefore, studies investigating co-selection in environments impacted by agriculture and aquaculture should focus on Hg, Cd, Cu, and Zn as selecting heavy metals. Nevertheless, the respective environmental background has to be taken into account.