Plasmids are small circular pieces of DNA that move between neighbouring bacteria (the ‘donor’ bacteria giving the plasmid and the ‘recipient’ bacteria receiving the plasmid) in a process called conjugation. Plasmids containing antibiotic resistance genes are a major driver of antimicrobial resistance (AMR), including resistance against carbapenem- a ‘last-resort’ antibiotic. This research developed a novel method to further our understanding on the spread of AMR - where and how plasmids are shared between bacteria, particularly plasmids carrying clinically important antibiotic resistance genes. These results also break the common assumption that bacteria which are extremely resistant to antibiotics, Gram-negative bacteria, cannot readily exchange antibiotic resistance genes with Gram-positive bacteria – the latter being easier to treat with antibiotics. The study also explored the effect of environmental stressors on plasmid transfer, finding that chlorine can modify plasmid conjugation.