The goal of this observational study is to diagnose colorectal cancer or precancerous tumors in participants over the age of 18 hospitalized with blood stream infection with anaerobic gut-associated bacteria. The main question it aims to answer is:

• How prevalent is cancer and precancerous tumors in the large intestines and rectum in patients with anaerobic bacteremia? Participants will be offered an examination using colon capsule endoscopy 4-8 weeks after discharge.

Inclusion Criteria:

• Older than 18 years
• Blood culture with growth of one or more of the following bacterial genera Bacteroides, Clostridium, Filifactor, Fusobacterium, Gemella, Granulicatella, Parvimonas, Peptostreptococcus, Prevotella, Solobacterium, Peptoniphilus, Ruminococcus, Finegoldia and Streptococcus.
• Able to provide oral and written informed consent
• Able to read and speak Danish

Exclusion Criteria:

• Prior colorectal cancer diagnosis
• History of stenosis of the gastrointestinal tract
• Previous treatment of inflammatory bowel disease
• Previous major surgery of the gastrointesinal tract (e.g. gastric bypass)
• Colostomy
• Pacemaker/ICD
• Pregnancy or breastfeeding
• Allergies to the bowel preparation regimen
• Severe kidney disease
• Focus of infection in skin and soft tissue or outside the truncus (e.g. decubitus, diabetic foot ulcer)
• Tumor in the colon or rectum at diagnostic imaging
• Transfer to other hospital outside the region

Patients admitted to Odense University Hospital with anaerobic blood stream infection.

Patients who are discharged before result of blood culture with anaerobic gut-associated bacteria, will be contacted by letter and offered participation in the study.