| Infectious agents causing colitis and/or ileitis |
| Bacteria |
| Shigella species |
| Enterohemorrhagic Escherichia coli |
| Enteroinvasive E. coli |
| Campylobacter jejuni |
| Salmonella species (gastroenteritis and typhoid fever) |
| Yersinia enterocolitica |
| Mycobacterium tuberculosis |
| Clostridioides (formerly Clostridium) difficile |
| Vibrio parahaemolyticus |
| Chlamydia trachomatis (lymphogranuloma venereum serotypes) |
| Parasites |
| Entamoeba histolytica |
| Schistosoma species |
| Balantidium coli |
| Trichinella spiralis |
| Viruses |
| Cytomegalovirus |
| Infectious agents causing proctitis |
| Neisseria gonorrhoeae |
| Herpes simplex virus |
| C. trachomatis |
| Treponema pallidum |
| Cytomegalovirus |
