Blood poisoning is a major health burden in the world, with an estimated 1,200,000 people living in Europe each year, leading to 157,000 deaths. The burden and challenge this causes for health care is further exacerbated by the growing resistance problem. Most bacteraemia in Sweden is caused by Escherichia coli. The prevalence of extended spectrum beta-lactamase (ESBL) producing E. coli (ESBL-EC) has increased in Sweden for several years: from 2.3% in 2007 to 7% in 2017 (3, 4). The aim of this project is to investigate the duration of ESBL-EC faecal carriers in patients with recurrent UVI caused by ESBL-EC. The study is a continuation of a retrospective study in which virulence and resistance genes, clinical resistance patterns and host factors were compared with EC without ESBL, and will provide the basis for future intervention studies. Specific research questions of the project are: Do the length of faecal carriers differ between patients colonized with the H30-Rx subclone compared to other clones? Do these carriers alter the diversity and composition of their fecal microbiome? What virulence factors predispose to extended carrier?