Proctitis may be a manifestation of Sexually transmitted infections (eg, Neisseria gonorrhoeae, Chlamydia species) Certain enteric infections (eg, Campylobacter, Shigella, Salmonella —see Introduction to Gram-Negative Bacilli) Inflammatory bowel disease Radiation treatments Proctitis associated with prior antibiotic use may be due to Clostridioides difficile (formerly Clostridium difficile).