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Diagnosis of salmonellosis
Medical expert of the article
Last reviewed: 04.07.2025
Typical forms of salmonellosis begin acutely with increasing severity of the general condition; fever is relatively long, characterized by infrequent but prolonged "unmotivated" vomiting, pain and rumbling in the right iliac region, thickly coated tongue, flatulence ("full belly"), enteritic or enterocolitis stool of the "swamp mud" type with an unpleasant, foul odor. In moderate and severe forms, hepatosplenomegaly occurs, especially in young children, CNS changes in the form of lethargy, confusion, drowsiness, in the peripheral blood - pronounced leukocytosis, neutrophilia with a shift to the left (band-nuclear shift), increased ESR.
The results of bacteriological and serological studies are decisive in establishing a diagnosis.
- The bacteriological method is of the greatest importance. Salmonella can be detected in feces, vomit, gastric lavage, urine, blood, and cerebrospinal fluid. The material is collected and cultured on nutrient media in the same way as with shigellosis and other bacterial intestinal infections. Feces, urine, and bile are cultured on elective nutrient media (Ploskirev medium, bismuth-sulfite agar, etc.) or on enrichment media (Muller medium, Kaufman medium, etc.). Blood culture should be done throughout the febrile period. 5-8 ml of blood is taken from a vein and cultured in 10-20% bile broth or Rappoport medium. The percentage of positive results in bacteriological testing ranges from 40 to 80%. The greatest number of positive results occurs in the first week of the disease.
- Serological methods of research are aimed at detection of both specific antibodies in the patient's blood and antigen in the biomaterial. The presence of specific antibodies in the patient's blood and their titer are determined using RA or RNGA with erythrocyte diagnosticums. Take 1-2 ml of blood from a vein or from a finger, dilute the obtained blood serum with an isotopic solution of sodium chloride, add a diagnosticum containing O-antigens of salmonella serogroups A, B, C, D. The presence of antibodies in a dilution of 1:100 or an increase in their titer in the dynamics of the disease by 2-4 times or more is of diagnostic value. Currently, in practical work, RNGA is most widely used as a more sensitive and specific reaction than RA. Negative results of serological research occur in the mildest, erased forms of the disease, as well as in young children and newborns with severe forms of the disease.
To detect salmonella antigens in coprofiltrates and urine, the coagglutination reaction and ELISA are used, which allows determining the antibody titer in the blood. This is a more effective and promising method, since it can be used to separately determine specific antibodies of different classes (A, M, G). Specific immunoglobulins of class M always indicate an active infectious process.
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