Shigellosis (bacterial dysentery)

Shigellosis (bacterial dysentery, Shigellosis, dysenterya) is an acute infectious disease caused by bacteria of the genus Shigella with a fecal-oral mechanism of transmission of the pathogen and characterized by a picture of distal colitis and intoxication. Symptoms of dysentery include fever, nausea, vomiting and diarrhea, which is usually bloody in nature. Diagnosis of dysentery is based on the clinic and confirmed by a culture study. Treatment of dysentery is supportive and mainly aimed at rehydration and the administration of antibiotics (for example, ampicillin or trimethoprim-sulfamethoxazole). These drugs are the drugs of choice.

ICD 10 codes

• A03.0. Dysentery due to Shigella dysenteriae.
• A03.1. Dysentery due to Shigella flexneri.
• A03.2. Dysentery due to Shigella boydii.
• A03.3. Dysentery caused by Shigella sonnei.
• A03.8. Other dysentery.
• A03.9. Dysentery, unspecified.

What causes dysentery?

Shigella species are widespread and are the typical cause of inflammatory dysentery. Shigella species account for 5-10% of diarrheal diseases in many regions. Shigella are divided into four main subgroups: A, B, C, and D, which are further divided into specific serologic types. Shigella flexneri and Shigella sonnei are found more frequently than Shigella boydii, and especially the virulent Shigella dysenteriae. Shigella sonnei is the most frequently encountered isolate in the United States.

The source of infection is the feces of sick people and recovering carriers. Direct spread occurs via the fecal-oral route. Indirect spread occurs through contaminated food and objects. Fleas can serve as carriers of shigella. Epidemics most often occur in densely populated populations with inadequate sanitary measures. Dysentery is especially common in young children living in endemic regions. In adults, dysentery is usually not as acute.

Convalescent and subclinical carriers can be a serious source of infection, but long-term carriage of this microorganism is rare. Dysentery leaves almost no immunity.

The pathogen penetrates the mucosa of the lower intestine, causing mucus secretion, hyperemia, leukocyte infiltration, edema, and often superficial ulceration of the mucosa. Shigella dysenteriae type 1 (not found in the United States) produces Shiga toxin, which causes severe watery diarrhea and sometimes hemolytic uremic syndrome.

What are the symptoms of dysentery?

Dysentery has an incubation period of 1-4 days, after which typical symptoms of dysentery appear. The most common manifestation is watery diarrhea, which is indistinguishable from diarrhea that occurs with other bacterial, viral and protozoan infections, in which there is increased secretory activity of intestinal epithelial cells.

In adults, dysentery may begin with episodes of cramping abdominal pain, urge to defecate, and defecation of formed feces, followed by temporary relief of pain. These episodes recur with increasing severity and frequency. Diarrhea becomes severe, with soft, loose stools containing mucus, pus, and often blood. Rectal prolapse and subsequent fecal incontinence may cause acute tenesmus. In adults, the infection may manifest without fever, with diarrhea in which the stool contains no mucus or blood, and with little or no tenesmus. Dysentery usually ends in recovery. In the case of a moderate infection, this occurs in 4-8 days, in the case of an acute infection - in 3-6 weeks. Severe dehydration with loss of electrolytes and circulatory collapse and death usually occurs in debilitated adults and children under 2 years of age.

Rarely, dysentery begins suddenly with rice-water diarrhea and serous (sometimes bloody) stools. The patient may vomit and quickly become dehydrated. Dysentery may manifest with delirium, convulsions, and coma. Diarrhea is mild or absent. Death may occur within 12 to 24 hours.

In young children, dysentery begins suddenly. Fever, irritability or tearfulness, loss of appetite, nausea or vomiting, diarrhea, abdominal pain and bloating, and tenesmus occur. Within 3 days, blood, pus, and mucus appear in the stool. The number of bowel movements may reach more than 20 per day, and weight loss and dehydration become acute. If untreated, the child may die within the first 12 days of the disease. In cases where the child survives, the symptoms of dysentery gradually subside by the end of the second week.

Secondary bacterial infections may occur, especially in debilitated and dehydrated patients. Acute mucosal ulcerations may result in acute blood loss.

Other complications are rare. They may include toxic neuritis, arthritis, myocarditis, and rarely intestinal perforation. Hemolytic uremic syndrome may complicate shigellosis in children. This infection cannot become chronic. It is also not an etiologic factor for ulcerative colitis. Patients with the HLA-B27 genotype more often develop reactive arthritis after shigellosis and other enteritis.

How is dysentery diagnosed?

Diagnosis is made simpler by a high index of suspicion for shigellosis during outbreaks, the presence of the disease in endemic regions, and the detection of leukocytes in stool when examining smears stained with methylene blue or Wright's stain. Stool culture allows diagnosis and should therefore be performed. In patients with dysentery symptoms (mucus or blood in the stool), differential diagnosis is necessary with invasive E. coli, salmonella, yersiniosis, campylobacteriosis, as well as amebiasis and viral diarrhea.

The mucosal surface is diffusely erythematous with numerous small ulcers when examined with a rectoscope. Although the white blood cell count is low at the onset of the disease, it averages 13x109. Hemoconcentration and diarrhea-induced metabolic acidosis are common.

How is dysentery treated?

Dysentery is treated symptomatically with oral or intravenous fluids. Antibiotics may relieve the symptoms of dysentery due to dysentery and mucosal damage, but are not necessary in otherwise healthy adults with mild infection. Children, the elderly, the debilitated, and those with acute infection should be treated with antibiotics for dysentery. In adults, the drugs of choice are a fluoroquinolone such as ciprofloxacin 500 mg orally for 3 to 5 days or trimethoprim-sulfamethoxazole two tablets once every 12 hours. In children, treatment is with trimethoprim-sulfamethoxazole 4 mg/kg orally every 12 hours. Dosing is based on the trimethoprim component. Many Shigella isolates are likely to be resistant to ampicillin and tetracycline.

How is dysentery prevented?

Dysentery is prevented by washing hands thoroughly before preparing food, and by placing soiled clothing and bedding in closed containers with soap and water until they can be boiled. Proper isolation techniques (especially stool isolation) should be used in patients and carriers. A live vaccine for Sonne dysentery is in development, and studies in endemic areas show promise. Immunity is usually type-specific.