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Bacterial Infections of the Colon - Types and Treatment

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Bacterial colitis is caused by ingesting contaminated food and water and is characterized by inflammatory-type diarrhea. Read the article to know in detail.

Medically reviewed by

Dr. Ghulam Fareed

Published At May 5, 2023
Reviewed AtAugust 10, 2023


An inflammatory type of diarrhea characterized by purulent, bloody, and mucoid stool is called bacterial colitis or bacterial colon infection. The bacteria causing the infection are salmonella, shigella, campylobacter, escherichia, and yersinia. The common symptoms include fever, severe abdominal pain, and tenesmus. Diagnostic tests include rectal swabs and stool culture. These infections are self-limiting; hence antibiotics are used for the treatment.

What Are the Bacterial Infections of the Colon?

Bacterial infections of the colon are known as bacterial colitis and are also referred to as acute infectious bacterial diarrhea. It is a common problem globally and in general practice. These infections occur in children, elderly people, and immunocompromised individuals. The transmission mode of infection is the fecal-oral route, ingestion of contaminated water and food, animal hosts, and close contact with an infected person.

Bacterial diarrhea is of two types - inflammatory and non-inflammatory.

  • Inflammatory Diarrhea: It is caused by salmonella, shigella, campylobacter, yersinia, chlamydia tuberculosis, Neisseria, and escherichia coli. It is characterized by bloody, mucopurulent stool associated with fever, abdominal pain, and tenesmus.

  • Non-inflammatory Diarrhea: It is caused by escherichia coli and staphylococcus pathogens that cause an alteration in the absorption and secretion process of the bowel, resulting in watery diarrhea without illness.

What Are the Bacteria Involved in Causing Infection and Its Symptoms?

  • Campylobacter: They are gram-positive, microaerophilic, curved bacteria. The common species is Campylobacter jejuni. The transmission occurs through contamination and ingestion of undercooked chicken.

    • Symptoms: Dysentery, asymptomatic or watery diarrhea, fever, abdominal pain, and bloody stool. It resolves within a week or two. Chronic and recurrent diarrhea occurs in immunocompromised patients.
    • Complications: Pancreatitis, gastrointestinal hemorrhage, hemolytic uremic syndrome, toxic megacolon, meningitis, and purulent arthritis.
  • Salmonella: Salmonella is a rod-shaped, gram-negative bacterium. These bacteria are associated with enterocolitis, gastroenteritis, and focal infections such as meningitis, cholangitis, pneumonia, and septic arthritis. In addition, salmonella typhi and paratyphi are involved in typhoid fever. The infection through salmonella bacteria is usually food-borne, and the modes of transmission are flies, fingers, feces, food, and fomites. Salmonella enteritidis and salmonella typhimurium are the common species causing enterocolitis. The carriers of the bacteria are mostly poultry, household pets, and lizards. S.typhi causes typhoid fever, which is very common.

    • Symptoms: Vomiting, nausea, diarrhea, and abdominal cramps. The symptoms appear after 8 to 48 hours of ingesting contaminated food and last for three to five days in the case of gastroenteritis and two to three weeks in the case of enterocolitis.
    • Bacteremia is a salmonella infection complication resulting in meningitis, endocarditis, osteomyelitis, focal abscess, and arteritis.
    • Predisposing factors: Hemolytic anemia, sickle cell anemia, and immunosuppression (chemotherapy, corticosteroids, acquired immunodeficiency syndrome).
    • Clinical manifestations of S. typhi are typhoid fever, abdominal pain, delirium, splenomegaly, skin rashes, and bacteremia.
  • Shigella: Shigella is a gram-negative enteric group of organisms that causes gastrointestinal illnesses ranging from mild diarrhea to severe dysentery. It is an endemic disease affecting more than six lakh people yearly. Although shigella is contagious and needs a small number of inocula to yield its symptoms, it spreads rapidly from person to person with oral-anal and fecal-oral contacts. It is commonly seen in nursery schools, male homosexuals, and daycare centers.

    • Symptoms: Dysentery with crampy abdominal pain, fever, rectal burning, and bloody mucoid stools.
    • Severe complications include intestinal proliferation, septic shock, hypoglycemia, seizures, profound dehydration, and encephalopathy. If left untreated, shigellosis is confused with ulcerative colitis.
  • Escherichia Coli: These are normal microflora of the human intestine. They are harmless in the bowel. Five species cause infections, which are the primary reservoir of infection in cattle. The infection is caused by consuming contaminated food and undercooked beef.

    • Its symptoms are similar to inflammatory bowel disease, ischemic colitis, or pseudomembranous colitis, such as diarrhea with or without blood, vomiting, fever, and thrombocytopenia.
  • Yersinia: Y. enterocolitica and Y. pseudotuberculosis are anaerobic gram-negative bacilli similar to E.coli. Yersinia enterocolitis resembles enteritis and appendicitis because of its prevalence, and it is essential to understand the infection. This infection occurs through hand-to-mouth transfer, fecal-oral route, or contaminated food or water.
    • Symptoms: Fever, diarrhea, abdominal pain, nausea, and vomiting.
  • Chlamydia: Chlamydia species are intracellular, obligate organisms and asymptomatic infected persons are the reservoir for infection transmission.

    • Symptoms: Bloody diarrhea, mucopurulent anal discharge, tenesmus, and rectal pain. Mild to severe ulcerative proctocolitis. Perianal fistula formation and stricture formation.

How to Diagnose the Infection of the Colon?

Diagnosis of bacterial infection:

  • Campylobacter infection in colitis is diagnosed by stool examination showing erythrocytes and leukocytes. Colonoscopy examination shows loss of vascular pattern with ulceration, segmental edema, and patchy colonic mucosa. In addition, the stool culture of C. jejuni shows the growth of enteric bacteria.

  • The isolation of bacteria detects salmonella infection. Blood cultures are positive for salmonella. Stool culture and rectal swabs, and endoscopic biopsies are influential in salmonellosis. Nontyphoidal infections show friability of mucosa, hyperemia, ulcerations, aphthous erosions, and deep fissures of the colon involved.

  • Shigella is diagnosed based on a history of symptoms like abdominal pain, rectal burning, and diarrhea. Stool culture shows red blood cells and leukocytes. A colonoscopy shows edema, erythema, hemorrhagic spots, mucosal friability, erosions, and ulcers.

  • Stool cultures confirm E.coli infection. A colonoscopy shows shallow ulcerations, marked edema, mucosal hyperemia, erosions, hemorrhage, and ulcer-like lesions throughout the colon. CT scan reveals a target sign of diffuse colon wall thickening.

  • Yersinia infection is diagnosed by stool examination. Hemagglutination is a specific test to diagnose Yersinia infection. Colonoscopy shows oval yellow aphthae of the colon, round or oval elevations with or without ulcerations in the ileum, similar to Crohn’s disease.

  • Diagnosis of chlamydia infection includes the culture of stool or rectal swabs onto McCoy cells. A colonoscopy shows inflammatory changes with mucosal friability and minor erosions in the distal rectum.

What Is the Treatment?

  • Campylobacter Infection: Treatment involves antibiotic therapy, although the disease is self-limiting. Quinolone is the drug of choice for campylobacter infection. In case of resistance to fluoroquinolones, Azithromycin is effective.

  • Salmonella Infection: Treatment includes using Amoxicillin, Quinolones, or Trimethoprim-Sulfamethoxazole as first-line antibiotics. For severe infection, cases of third-generation cephalosporins or quinolones are prescribed.

  • Shigella Infection: Treatment is started with resuscitation and therapy for severe complications such as encephalopathy, seizures, and intestinal perforation. Quinolones are the drug of choice to treat shigella infection in adults and Azithromycin in children.

  • E. Coli Infection: Treatment depends on the severity of hemorrhagic colitis and the frequency of complications. Antibiotics such as Ciprofloxacin are used to treat infections.

  • Yersinia Infection: This infection is self-limiting. In prolonged cases, it is treated using antibiotics such as Doxycycline, aminoglycosides, or fluoroquinolones.

  • Chlamydia Infection: Treatment with Tetracycline or Doxycycline is the choice of treatment. For patients intolerant to Tetracycline; fluoroquinolones are used.

How to Prevent the Infection?

The bacterial infections are prevented by:

  • Safe handling of food.

  • Boiling and proper cooking of poultry, egg, beef, and pork.

  • Washing of hands after toilet use or diaper change.


Salmonella, E.coli, shigella, yersinia, and campylobacter species cause bacterial infection of the colon. The infection is transmitted from one person to another, the fecal-oral route, and hand to mouth. The leading carriers are animals like cattle, pets, poultry, and humans. These are usually self-limiting infections that are treated with antibiotic therapy after proper examination and diagnosis. If not treated, they cause severe complications.

Dr. Ghulam Fareed
Dr. Ghulam Fareed

Medical Gastroenterology


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