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Shigellosis (bacterial dysentery)

The disease is an acute inflammatory process in the gastrointestinal tract caused by bacteria of the genus Shigella and is characterized by fever, cramping abdominal pain and diarrhea mixed with mucus, pus and blood in the feces. Sometimes the disease proceeds like normal diarrhea.

Etiology. Shigella - short motionless gram-negative rods, the biochemical feature of which is the absence or very slow fermentation of lactose. Other biochemical features help distinguish shigella from E. coli, which also does not ferment lactose and does not produce gas. The genus Shigella is divided into four groups (A, B, C and D) depending on their biochemical properties and antigenic composition. Group A includes 10 serotypes, of which Shigella disenteriae is of the greatest importance. Group B includes 6 serotypes, of which Shigella flexneri is the most common. Of the serotypes of group C, S. boydii is found, and group D contains only one pathogen, most often S. sonnei, which accounts for half of the cases of the disease.

Epidemiology. Shigella are common throughout the world. Most often, children aged 1–4 years fall ill. The maximum incidence rate is observed at the end of summer, but seasonality is not as pronounced as with salmonellosis.

Man serves as the main reservoir of infection. Infection occurs with direct infection by the feces of sick patients with water or food. Ways of infection: contact-household, food, water. Flies are active carriers of the disease.

Pathogenesis. For the development of the disease, infection with a small number of shigella (less than 200) is sufficient. Pathogens remain viable in the acidic environment of the gastric contents for 4 hours. The infection develops only when the pathogen penetrates the intestinal epithelial cells. Reproduction of the pathogen can occur simultaneously in epithelial cells, the submucosal layer of lamina propria. In this case, epithelial cells are destroyed, edema, local inflammation and hyperemia develop. Damage is superficial, and therefore intestinal perforation does not occur, and bacteremia is very rare. The phenomena of gastroenterocolitis usually resolve spontaneously after 4-7 days. S. disenteriae produce enterotoxin, but their role in the pathogenesis of the disease is not entirely clear. Toxigenic, but minimally invasive forms of shigella do not cause disease. At the same time, non-toxic, but highly invasive strains cause severe dysentery. Virulent strains of S. flexneri and S. sonnei are distinguished by the presence of a plasmid that encodes the J antigen belonging to the side chain of Shigella O-polysaccharides.

Clinical manifestations. The incubation period depends on the route of infection and the dose of the pathogen and usually ranges from 6-8 hours to 7 days, more often 36-72 hours, during which the shigella reach the large intestine. Initially, patients complain of fever and cramping abdominal pain. Body temperature can reach 40 ° C, the effects of general intoxication intensify. 48 hours after the onset of the disease, diarrhea appears, bowel movements with blood and mucus occur up to 20 times a day. In the following days of the disease, bloody diarrhea may persist against a background of normalized body temperature or the absence of abdominal pain. When examining a child, there is a slight pain in the abdomen during palpation without a clear localization.

At high temperature and seizures, shigellosis can be accompanied by symptoms of damage to the nervous system, reminiscent of meningitis, encephalitis. Significant loss of fluid and electrolytes can lead to dehydration, acidosis and electrolyte imbalance. Children may have tenesmus. In severe forms of dysentery, especially in weakened, dystrophic children, rectal prolapse may develop.

With contamination of the eyes with fingers or other objects, conjunctivitis develops. Bacteremia develops extremely rarely, so local foci of infection outside the intestine are usually not found. General infection with the development of pneumonia, meningitis, osteomyelitis and arthritis can occur only in young children with significant malnutrition. In such cases, severe dehydration is observed, sometimes leading to hemolytic uremic syndrome and renal failure.
Non-purulent arthritis and Reiter's syndrome due to dysenteric infection are usually associated with the presence of the HLA B27 antigen. Mortality with bacteremia due to shigellosis reaches 50%, this complication usually occurs with dehydration in non-fever children with prolonged diarrhea and malnutrition.

Diagnosis. Dysentery should be suspected in all patients with diarrhea accompanied by fever. The diagnosis of shigellosis is established on the basis of clinical and epidemiological data, with mandatory laboratory confirmation.

For the final diagnosis use:

1) the bacteriological method of greatest importance. It is carried out before the appointment of antibacterial therapy. For the study of the material, particles of feces with pathological impurities, except blood, are selected. Sowing of the material is carried out on selective media. A negative result is given on the 3rd-51st day, and a positive result is the 5th-7th day from the moment the material is delivered to the laboratory;

2) serological methods used in doubtful cases and with negative results of bacteriological examination of feces. They are carried out in two directions: determination of the titer of specific antibodies in the patient's blood serum and antigen in the feces. In the presence of typical clinical symptoms and the detection of a diagnostic titer of specific antibodies (1: 200 and higher) or an increase in their titer in the dynamics of the disease, a clinical diagnosis of shigellosis infection is considered established even in the absence of seeding shigella from the patient's stool;

3) express diagnostic methods based on the detection of Shigella antigen in feces using the direct method of luminescent antibodies or the immunoadsorption method;

4) a sigmoidoscopic method used to diagnose erased forms of the disease and to elucidate the causes of prolonged bacterial excretion of shigella;

5) the coprological method used as an auxiliary in the diagnosis of shigellosis in the presence of colitis. In patients with shigellosis, along with inflammatory changes, signs of a violation of the enzymatic and absorption functions of the intestine are determined;

6) a study of peripheral blood. With all shigellosis, moderate leukocytosis, neutrophilic and stab shift of the blood formula, accelerated ESR are noted. Differential diagnosis. Bacterial dysentery must be differentiated with other forms of enterocolitis caused by enterotoxigenic Escherichia coli, salmonella, campylobacter, amoebic dysentery, viral infections, acute appendicitis, intestinal invagination and mesenteric lymphadenitis.

Treatment. With antibiotic treatment, the duration of the disease and the timing of the release of shigella are significantly reduced. The choice of antibiotic depends on the drug sensitivity of pathogens that persist in members of this team. Antibiotics usually allow you to clear the digestive tract from shigella. Long-term carriage of bacteria develops very rarely. In such cases, a temporary effect is caused by lactulose, a derivative of lactose. In acute forms of dysentery, lactulosis is ineffective. Drugs that reduce peristalsis are contraindicated in bacterial dysentery. The need for the introduction of fluid and electrolytes is determined by the hydration status of the patient.

Forecast and prevention. In most previously healthy children, shigellosis is favorable and prone to spontaneous cure. Pathogens continue to be excreted for about 3 months after an acute illness. High levels of morbidity and mortality from bacterial dysentery are observed in closed groups in developing countries, in which children often suffer from dystrophy.

Strict observance of personal hygiene and sanitary measures are the basis for the prevention of shigellosis. Thorough and systematic hand washing should be law for all persons caring for patients with bacterial dysentery. In hospitals, all requirements for isolation of patients must be strictly observed. An effective and affordable vaccine has not been created.

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Shigellosis (bacterial dysentery)

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