Clostridioides difficile is a toxigenic, anaerobic spore-forming bacterium. C. difficile infection (CDI) is the leading cause of healthcare-associated diarrhea and pseudomembranous colitis, particularly in elderly, hospitalized patients that have received antibiotic treatment.

The aims of this thesis were to investigate the molecular epidemiology, transmission and virulence of CDI in Region Jönköping County, including a local outbreak of C. difficile ribotype (RT) 046. Additionally, the thesis aimed to assess the impact of fecal microbiota transplantation (FMT) on the health related quality of life (HRQoL) in patients with recurrent CDI (rCDI).

In paper I we collected and ribotyped C. difficile isolates from patients in the county during one year. Two different RTs, RT 001 and RT 012, were associated with nosocomial transmission. In paper II we analyzed a large local outbreak dominated by RT 046 using ribotyping and whole genome sequencing to explore epidemiological links. Furthermore the virulence of RT 046 was assessed, and interventions implemented to stop the outbreak were evaluated. RT 046 was widely spread throughout Högland Hospital, and was associated with a higher mortality compared to other strains. In paper III, toxin production and sporulation capacity in epidemic RT 046 were compared to other less prominent RTs. RT 046 produced higher levels of toxin and exhibited a higher degree of antibiotic resistance compared to the other strains from the outbreak. Finally, in paper IV we evaluated the HRQoL in patients with rCDI before and after treatment with FMT. We found that patients with rCDI had low HRQoL which increased significantly after treatment with FMT.