Shigelosis - Causes, Symptoms and Treatments

Shigelosis, also known as bacillary dysentery, is an acute intestinal infection caused by the bacteria Shigella, a short, nonmotile, gram-negative rod. Shigella can be classified into four groups, all of which may cause shigellosis: group A (Shigella dysenteriae), which is most common in Central America and causes particularly severe infection and septicemia; group B (Shigellafiexneri); group C (Shigella boydii); and group D (Shigella sonnei). Typically, shigellosis causes a high fever (especially in children), acute self-limiting diarrhea with tenesmus (ineffectual straining at stool) and, possibly, electrolyte imbalance and dehydration. It's most common in children ages 1 to 4; however, many adults acquire the illness from children.

Shigellosis is endemic in North America, Europe, and the tropics. In the United States, about 23,000 cases appear annually, usually in children or in elderly, debilitated, or malnourished people. Shigellosis commonly occurs among confined populations such as those in mental institutions; it's also common in hospitals.

The prognosis is good. Mild infections usually subside within 10 days; severe infections may persist for 2 to 6 weeks. With prompt treatment, shigellosis is fatal in only 1 % of cases, although in severe Shigella dysenteriae epidemics, mortality may reach 8%.

Causes of Shigelosis:

Transmission occurs through the fecaloral route, by direct contact with contaminated objects, or through ingestion of contaminated food or water. Occasionally, the housetly is a vector.

Signs and symptoms of Shigelosis:

After an incubation period of 1 to 4 days, Shigella bacteria invade the intestinal mucosa and cause inflammation. In children, shigellosis usually produces high fever, diarrhea with tenesmus, nausea, vomiting, irritability, drowsiness, and abdominal pain and distention. Within a few days, the child's stool may contain pus, mucus, and -from the superficial intestinal ulceration typical of this infection - blood. Without treatment, dehydration and weight loss are rapid and overwhelming.

In adults, shigellosis produces sporadic, intense abdominal pain, which may be relieved at first by passing formed stools. Eventually, however, it causes rectal irritability, tenesmus and, in severe infection, headache and prostration. Stools may contain pus, mucus, and blood. In adults, shigellosis doesn't usually cause fever.

Complications of shigellosis, such as electrolyte imbalance (especially hypokalemia), metabolic acidosis, and shock, are not common but may be fatal in children and debilitated patients. Less common complications include conjunctivitis, iritis, arthritis, rectal prolapse, secondary bacterial infection, acute blood loss from mucosal ulcers, and toxic neuritis.

Diagnosis of Shigelosis:

Fever (in children) and diarrhea with stools containing blood, pus, and mucus point to this diagnosis; microscopic bacteriologic studies and culture help confirm it.

Microscopic examination of a fresh stool may reveal mucus, red blood cells, and polymorphonuclear leukocytes; direct immunofluorescence with specific antisera may reveal Shigella. Severe infection increases hemagglutinating antibodies. Sigmoidoscopy or proctoscopy may reveal typical superficial ulcerations.

Diagnosis must rule out other causes of diarrhea, such as enteropathogenic Escherichia coli infection, malabsorption diseases, and amebic or viral diseases.

Treatment of Shigelosis:

Treatment of shigellosis includes enteric precautions, low-residue diet and, most Important, replacement of fluids and elcctrolytes with I.V. infusions of normal saline solution (with electrolytes) in sufficient quantities to maintain a urine output of 40 to 50 ml/hour. Antibiotics are of questionable value but may be used in an attempt to eliminate the microbe and there­by prevent further spread. Ampicillin, tetracycline, or cotrimoxazole may be useful in severe cases, especially in children with overwhelming fluid and electrolyte loss.

Antidiarrheals that slow intestinal motility are contraindicated in shigellosis because they delay fecal excretion of Shigella and prolong fever and diarrhea. An investigational vaccine containing attenuated strains of Shigella appears promising in preventing shigellosis.

Special considerations and Prevention tips of Shigelosis:

Supportive care can minimize complications and increase patient comfort.

1. To prevent dehydration, administer I.V. fluids, as ordered. Measure intake and output (including stools) carefully.

2. Correct identification of Shigella requires examination and culture of fresh stool specimens. Therefore, hand-carry specimens directly to the laboratory. Because shigellosis is suspected, include this information on the laboratory slip.

3. Use a disposable hot-water bottle to relieve abdominal discomfort, and schedule care to conserve patient strength.

4. To help prevent spread of this disease, maintain enteric precautions until microscopic bacteriologic studies confirm that the stool specimen is negative.

5. If a risk of exposure to the patient's stool exists, put on a gown and gloves before entering the room.

6. Keep the patient's (and your own) nails short to avoid harboring microbes. Change soiled linen promptly and store in an isolation container.

7. During shigellosis outbreaks, obtain stool specimens from all potentially infected staff, and instruct those infected to remain away from work until two stool specimens are negative.