Water environments: metal-tolerant and antibiotic-resistant bacteria

The potential threat of both metals and antibiotics to the environment and human health has raised significant concerns in the last decade. Metal-resistant and antibiotic-resistant bacteria are found in most environments, including water, and the risk posed to humans and animals due to the spread of antibiotic-resistant bacteria and antibiotic-resistant genes in the environment is increasing. Bacteria have developed the ability to tolerate metals even at notable concentrations. This ability tends to favor the selection of antibiotic-resistant strains, even in pristine water environments, with the potential risk of spreading this resistance to human pathogens. In this mini-review, we focus on investigations performed in marine and freshwater environments worldwide, highlighting the presence of co-resistance to metals and antibiotics.