The aim of this theme is to develop more efficient methods based on genomic and meta-genomic data to improve our evolutionary understanding of infections (e.g. drivers of virulence or drug resistance), and therefore provide an evidence base for proposing and evaluating policies (e.g. antibiotic stewardship or vaccine deployment). In particular, this theme is concerned with the fact that the genetic elements associated with UKHSAnotypes of interest (e.g. resistance or virulence genes) are often able to spread across different bacterial lineage backgrounds (e.g. plasmid conjugation or recombination). This implies a need to monitor the presence and evolution of these elements across a range of lineages or species, and across a range of ecological habitats. Understanding the causative factors for the spread of these elements requires us to correlate their spread with putative drivers (e.g. comparing microbiomes of patients exposed to antibiotics or not to determine the role of antibiotic usage in the spread of resistance elements), or investigating the effect of environmental factors creating selective pressure (e.g. use and presence of antibiotics in animals and food chain).