The potential negative impact for human health of veterinary use of antimicrobials in prophylaxis, metaphylaxis and growth promotion in animal husbandry was first established in the 1960s and 1970s. Determination of the molecular structure of antimicrobial resistance plasmids at that time explained the ability of antimicrobial resistance genes to disseminate among bacterial populations and elucidated the reasons for the negative effects of antimicrobials used in food animals for human health. In this issue of Environmental Microbiology, Liu et al.