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Salmonellosis is an acute infectious disease of humans and animals caused by Salmonella serovars and occurs in children more often in the form of gastrointestinal, less often typhoid-like and septic forms.

Etiology. Salmonella are motile gram-negative bacteria that do not have capsules and do not form spores. The main antigens of Salmonella are flagella (H), antigens of the cell wall (O) and thermolabile antigens of the membrane (Vi), which block the agglutination reactions of O-antigens and O-antibodies. More than 2200 salmonella serotypes are isolated. Currently used nomenclature provides for the allocation of three groups of salmonella: S. enteritidis, S. typhi and S. choleraesuis. Each Salmonella species is subdivided into bioserotypes, for example S. enteritidis bio - thyphimurium.

Salmonella are resistant to many physical factors, die at a temperature of 54.4 ° C after 1 h, and at 60 ° C after 15 min, remain viable in the environment at low temperatures for many days, live for weeks in stagnant waters, dried up food, pharmacological agents and feces.

The properties of salmonella causing their pathogenicity remain unclear. Endotoxin increases the resistance of the microorganism to phagocytosis, therefore, strains with a deficiency of this antigen are usually avirulent. The effect of endotoxin on a macroorganism is manifested in general disorders, although it does not play an important role in the development of gastroenteritis. Some types of salmonella affect mainly humans, causing characteristic signs of the disease. Infection of S. typhosa is observed only in humans, Salmonella groups A and C are mainly detected in humans, and S. alrortus equi only in horses.

Epidemiology. Human infection occurs when contaminated food or water is consumed. The main carrier of salmonella is a person who often serves as a source of food poisoning and poisoning. Breast milk can also be a source of salmonella distribution. So, some strains of this pathogen were isolated from milk and feces of donors. In a patient in the acute period of infection, 1–109 salmonella is secreted from 1 g of feces.

Their excretion with feces continues for 2 weeks after the infection in 70–90% of patients, in 50% it lasts up to 4 weeks and in 10-25% up to 10 weeks.

The duration of the carrier period is the same in symptomatic and asymptomatic forms, but in children under the age of 1 year it is longer than in older children. Duration of bacterial carriage increases with antibiotic treatment.

Pathogenesis and pathomorphology. The dose of the pathogen necessary for the development of the disease in humans is not precisely established. For both adults and children, it is determined by the resistance of the body and the virulence of the pathogen.

Salmonella indirectly stimulate the energy system of intestinal epithelial cells, resulting in increased secretion of water and electrolytes. Diarrhea-causing strains of salmonella contribute to the appearance of neutrophilic cell infiltration in their own membrane. Prostaglandins released from inflammatory exudate can also stimulate the adenylate cyclase system, increasing the secretion of fluid and electrolytes.

For the development of enterocolitis, the presence of salmonella in the depths of the intestinal mucosa is necessary. The contents of the stomach with a pH of 2.0 kills pathogens, while higher values ​​of it have a different effect on salmonella. At pH 5.0 or more, pathogens remain viable. The accelerated passage of food through the intestines, lysozyme and other enzymes are also able to withstand Salmonella infection.

Salmonella overcome the surface layers of the intestinal mucosa without damaging the epithelial cells. Around them are concentrated phagosomes that do not have a noticeable effect on microorganisms that penetrate through cells or into the knitting membrane. Serotypes that cause diarrhea cause leukocyte infiltration of the basement membrane. The infection does not spread further, and the patient develops only diarrhea, sometimes the body temperature rises slightly. The incidence of bacteremia is unknown, but it is usually transient, metastatic foci of infection in healthy children usually do not form.

Systemic diseases caused by salmonella are found mainly in the elderly and in patients with severe disorders of cellular immunity and the function of the reticuloendothelial system.
Salmonella septicemia and osteomyelitis often develop in children suffering from sickle cell anemia. Granulomatous diseases in children or other white blood cell dysfunctions increase the predisposition to infection. Chronic salmonella bacteremia and bacteriuria are noted in patients with schistosomiasis, also characterized by imperfection of phagocytosis.

Clinical manifestations. Gastroenteritis is most often observed in late summer and early fall, which coincides with an increase in the frequency of foodborne infections. Large epidemics occur precisely at this time, but sporadic cases occur throughout the year. The incubation period is 8–48 hours. Symptoms often appear in the morning after taking contaminated food the night before. The onset is acute, accompanied by nausea, vomiting, cramping abdominal pain, after which a large amount of feces of liquid consistency, sometimes mixed with mucus and blood, leaves. Vomiting is usually profuse and short-lived. Body temperature rises to 38–39 ° C in 70% of patients, but chills are less common. Lethal outcomes are rare (about 1%), mainly in people at high risk.

Infection in some individuals occurs without fever with minor bowel dysfunction. In other patients, body temperature rises sharply, headaches appear, consciousness is impaired, convulsions and meningeal phenomena develop. Strong bloating, muscle tension, significant local pain are sometimes noted.

Hematogenous dispersal of salmonella is accompanied by chills and fever. Usually it is observed in children up to 3 months. Sometimes the symptoms can resemble a picture of typhoid fever, but it is not so long and rarely leads to death. Salmonella can settle in any organ, causing pneumonia, abscesses, empyema, osteomyelitis, purulent arthritis, pyelonephritis or meningitis.

Complications Non-typhoid salmonellosis usually proceeds without complications or is limited to extraintestinal manifestations. In rare cases, children have reactive arthritis, developing 2 weeks after the onset of diarrhea, Reiter's disease (conjunctivitis, urethritis, polyarthritis).

The diagnosis is made on the basis of the results of bacteriological studies, when the material is incubated in a tetrathionate-enriched medium, followed by reseeding to a selective medium. A preliminary result can be obtained using the direct antibody fluorescence method; microscopic studies of urine, blood, feces, cerebrospinal fluid (CSF) and other affected organs; serological tests that help in the diagnosis of typhoid fever and other salmonellosis.

Differential diagnosis. Salmonella gastroenteritis must be differentiated from other viral and bacterial diseases accompanied by diarrhea, including those caused by rotaviruses, E. coli, Yersinia and campylobacter. Sometimes clinical data and radiographic signs suggest ulcerative colitis, which should be ruled out.

Treatment. Treatment should be aimed at correcting electrolyte disturbances and maintaining adequate hydration. Antibiotic treatment is indicated only in some cases: when there is a danger of spreading the infection (under the age of 3 months, with an immunodeficiency state or a severe progressive course of the disease).

With septicemia, high body temperature and metastatic foci of infection, children should be treated with ampicillin, amoxicillin or chloramphenicol, one of which is prescribed in 4 divided doses with an interval of 6 hours. The choice of antibiotic is determined by the sensitivity of the pathogen.

The prognosis for salmonella gastroenteritis is usually favorable, with the exception of very young children and patients with severe combined pathology. With salmonella endocarditis and meningitis, it is unfavorable even with early and intensive care.

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