Bacteria are remarkable at adapting to numerous challenges in their environment, and this evolutionary potential of bacterial pathogens can lead to a dire negative impact on health care. Notably, bacteria’s ability to rapidly become resistant to the antibiotic therapy administered to treat the infection is a pressing problem worldwide. I am interested in understanding the fine-scale evolutionary dynamics of bacterial populations over the course of infections, with the ultimate goal of improving therapeutic strategies. For this purpose, I am part of a team that studies within-host Pseudomonas aeruginosa infections in Intensive Care Unit patients across Europe at a high-resolution. I focus on the characterization of the genotypic diversity at the whole-genome level in search for evolutionary, population or genetic patterns, potentially associated with P. aeruginosa’s ability to develop antimicrobial resistance.