The main topic of our research is multidrug- and extensively drug-resistant gram-negative bacilli, mainly resistance conferred by extended-spectrum beta-lactamases and carbapenemases. Contributions of the group to this field in the past include the identification of epidemic clones of Klebsiella pneumoniae and Pseudomonas aeruginosa that are responsible for a large part of the dissemination of antimicrobial resistance in these species. The group has also worked extensively with Escherichia coli, most notably with the epidemic clone ST131 and its subclone H30-Rx. Gradually the focus has shifted towards pursuing explanations for the successfulness of these epidemic clones and to understand how they interact with the human microbiota. The focus has also shifted towards more experimental research, and more interventional and translational research.