Shigella Infections, Bacillary Dysentery, Gastroenteritis

What is Shigellosis?

Shigellosis is an infection of the intestines caused by several different species of Shigella bacteria. Also known as bacillary dysentery, this infection causes diarrhea and abdominal pain. Shigellosis infection may be spread person to person if organisms in feces contaminate food or water. Direct contamination happens if food is handled by a person who has not washed his or her hands after using the toilet. Infections can also be spread indirectly in areas of inadequate sanitation when flies settle on feces and then on food.

Shigellosis is the most communicable of all bacterial diarrheas. Up to 15,000 cases are reported annually in the US.

How is it diagnosed?

History: Shigellosis starts suddenly with symptoms including painful abdominal cramps, frequent, urgent episodes of watery diarrhea, fever, chills, headache, loss of appetite (anorexia), and malaise (a vague feeling of discomfort or illness). After a few days, diarrhea may become mixed with blood and mucus. The individual becomes progressively weaker. Persistent diarrhea may cause dehydration.

Physical exam is nonspecific (symptoms could apply to any number of conditions). There may be evidence of fever, abdominal tenderness, or hyperactive bowel sounds. Individual may have signs of dehydration including orthostatic blood pressure (blood pressure that changes with body position changes), dry mucous membranes, sunken eyes, and decreased skin tension (turgor). The rectal exam may be painful due to inflammation caused by constant diarrhea.

Tests: Direct microscopic examination of stained smears may reveal many leukocytes and red cells in the stool, but diagnosis is confirmed by identifying the infectious organisms in a stool culture. If septicemia is suspected, a complete blood count (CBC) may be done to detect the presence of bacterial toxins in the blood.

Colonoscopy (examination of the inside of the colon using a lighted, magnification instrument) may reveal areas of congested rectal mucosa, small flat irregular blue or purple spots (ecchymoses), and sometimes large areas of ulceration.

How is Shigellosis treated?

Shigellosis and its symptoms usually subsides after a week or so, but severe cases may last several weeks. Dehydration is treated by replacing fluids and electrolytes. Antibiotic therapy may be prescribed in severe cases. Antispasmodic drugs are helpful when cramps are severe.


Information Brand Generic Label Rating Bactrim Co-trimoxazole On-Label Cipro Ciprofloxacin On-Label
Minocycline Minocin Minocycline Off-Label
Principen 500 mg Principen Ampicillin On-Label Augmentin Amoxicillin/Clavulanate Off-Label
Noroxin Norfloxacin On-Label

What might complicate it?

Complications include severe dehydration, shock, or collapse. Septicemia, a life-threatening illness, can occur when bacteria multiply rapidly in the blood stream.

Predicted outcome

Shigellosis is a self-limited disease. The illness usually subsides after a week or so, but severe cases may last several weeks. Most individuals recover completely without any lasting effects.


Conditions with similar symptoms include inflammatory bowel disease, irritable bowel syndrome, or other forms of infective gastroenteritis.

Appropriate specialists

Internist and infectious disease specialist.

Last updated 18 December 2015


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