Infectious colitis occurs following invasion of colonic mucosa or attachment to the colonic mucosa by a micro-organism causing inflammation. Enteric pathogens that cause colitis are usually transmitted through fecal-oral route especially in children. Infectious colitis may also occur following antibiotics use, especially broad spectrum antibiotics. Infectious colitis may also be acquired as a sexually transmitted infection (STI) among individuals who practice unsafe anal sex especially among men who have sex with men (MSM).

Infectious colitis occurs following invasion of colonic mucosa or attachment to the colonic mucosa by a micro-organism causing inflammation

• Enteric organisms that cause colitis are usually transmitted through fecal-oral route especially in children. As few as 100 bacterial cells can be enough to cause an infection.^[1]
• May also occur following antibiotic use, especially broad spectrum antibiotics.
• Can also be acquired as a sexually transmitted infection (STI) among individuals who practice unsafe anal sex especially among men who have sex with men (MSM)

• In MSM the pathogens are transmitted directly through overt or microabrasions in the rectal mucosa or indirectly during oral-anal contact.^[2]

The pathogenesis, gross and microscopic pathology of infectious colitis will depend on the causative organism as follows:

• Shigella spp.
• Campylobacter jejuni
• Clostridium difficile
• Escherichia coli
• Nontyphoidal Salmonella
• Entameoba histolytica
• Chlamydia trachomatis
• Cytomegalovirus
• Yersinia enterocolitica