Infectious Colitis – Causes and Treatment

What Is Infectious Colitis?

Infectious colitis refers to inflammation of the colon (the main part of the large intestine) due to infection by bacteria, viruses, parasites or fungi, usually causing sudden lower abdominal pain and diarrhea.

Infectious colitis, especially in food poisoning, is often associated with infection of the stomach (gastritis), small intestine (enteritis), and/or rectum (proctitis).

General Symptoms of Infectious Colitis

All types of infectious colitis may cause:

  • Bloody or watery diarrhea (loose bowel movements), starting several hours to several days after start of an infection
  • Lower abdominal (stomach) pain or cramps
  • Constant urgency to have a bowel movement (the symptoms is medically known as tenesmus)
  • Pain in the rectum during bowel movement
  • Bloating (stomach distension due to accumulation of gas)
  • Fever
  • Nausea or vomiting

Bacterial Colitis Due to Food Poisoning

Sudden, explosive diarrhea, appearing 12-72 hours after ingesting food contaminated with bacteria, like E.coli, shigella, salmonella, yersinia, or campylobacter is a characteristic symptom of bacterial intestinal infection.

E. coli is a common cause of traveller’s diarrhea.

Shigella in developed parts of the world usually causes a mild, self-limiting disease (shigellosis), but in poor areas it may cause a severe, often deadly infection known as bacillary dysentery.

Parasitic Colitis Due to Food Poisoning

Insidious, slowly developing diarrhea with mucus and abdominal bloating starting several days or weeks after ingesting food contaminated with parasites, is characteristic for parasitic colitis. The most often cause of parasitic colitis is a one-cell parasite Entameba hystolytica, mainly transmitted by contaminated water and resulting in a mild or severe, often fatal infection, known as amebic dysentery.

Pseudomembranous Colitis – Cl. Difficile Overgrowth After Antibiotics

Bacterium Clostridium difficile is commonly present in the colon as the part of the normal intestinal flora, but its growth is limited by growth of other “healthy” bacteria. When these healthy bacteria are destroyed by antibiotics taken by mouth (like amoxicillin and clindamycin), Clostridium difficile may overgrow and excrete toxins that cause inflammation of the colon known as pseudomembranous colitis.

Watery diarrhea, lower left abdominal pain or bloating and barnyard smell of gas and stool, and fever are main symptoms.

Viral Colitis

Viral colitis is rare.

Citomegalovirus (CMV) may cause colitis in persons with lower immunity (due to chemotherapy, AIDS, etc.).

Herpetic colitis, caused by Herpes simplex virus (HSV) mostly occurs in homosexual men and is usually acquired during anal intercourse.

Fungal Colitis

Colitis, caused by fungi, like Candida albicans is rare and, like viral hepatitis, mainly occurs in persons with lowered immunity.

Diagnosis of Infectious Colitis

Diagnosis of infectious colitis may be suspected from the history of bloody diarrhea with urgency, appearing several hours after a suspicious meal, especially if other persons that have eaten the same food were also affected.


  • Bacteria can be detected by stool culture.
  • Parasites can be detected by “Ova and Parasites” (O&P) test of the stool, which is often false negative, so sometimes several repeating tests are needed if parasites are still suspected.
  • Blood tests. Elevated white cells in the blood speak for presence of inflammation anywhere in the body but do not by themselves confirm infection of the colon. Increased eosinophils(special type of white cells) and IgE antibodies are regularly elevated in parasitic infection. Microbes, appearing in the blood (sepsis) of a patient with bloody diarrhea, speak for invasive colitis.

Other causes of left side abdominal pain, especially diverticulitis, or right side abdominal pain, like a flare of Crohn’s colitis, and causes of the blood in the stool, and acute (sudden) diarrhea have to be considered.

Treatment of Infectious Colitis

Infectious colitis is treated by antibiotics or anti-parasitic medications, prescribed on the basis of results of stool tests. Rehydration solutions are often needed to replace lost water and minerals. Pain killers and drugs to lower high fever (antipiretics) may be needed in severe infection. Iron may need to be replaced in severe or prolonged bleeding.

Related articles:

Bacterial Diarrhea Due to Food Poisoning
Human Intestinal Parasites

About Jan Modric (249 Articles)
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