Living within a viral pandemic has brought home the importance of our relationship with microbes. Yet we are in the midst of another microbial risk that threatens to have a much larger impact on our lives. Microbes (bacteria, viruses, fungi or protists) that cause disease in humans, animals or plants are normally treated with antimicrobial drugs to control their numbers. Drug use has become routine since Alexander Fleming’s famous discovery of penicillin, in public health, veterinary practice and crop protection.