HUMORAL IMMUNE RESPONSE TO SHIGA TOXIN 2 (STX2) IN CHILDREN WITH ESCHERICHIOSIS WITH HEMOLYTIC-UREMIC SYNDROME

Shiga toxin-producing Escherichia coli (STEC) causes acute intestinal infections and also causes acute renal failure, especially in children. Shiga toxins (Stx) occupy a central place in the pathogenesis of hemolytic uremic syndrome (HUS) in Escherichiosis. The presented work analyzes the effectiveness of laboratory diagnostics of enterohemorrhagic escherichiosis in patients at the stage of manifestation of HUS and/or acute renal failure using microbiological, immunological research methods and PCR analysis. The study used clinical material from 30 patients in the pediatric intensive care unit of the St. Vladimir Children's City Clinical Hospital in Moscow with symptoms of HUS aged from 8 months to 5 years. Blood sera from 20 healthy donors were used as control. As a result of PCR analysis, stx2 DNA was detected in 23.3% of cases. Bacteriological research made it possible to sow a pure culture of Escherichia coli O157:H7 in only 3.3% of cases. Since the development of HUS begins in patients with acute intestinal infection caused by Shiga toxin-producing microorganisms starting from the 5th day of the disease, when antibiotic therapy is already carried out, the bacteria can be completely destroyed, which makes it difficult to identify them by bacteriological methods, as well as to detect genes encoding Shiga toxin in PCR analysis. Typically, patients with HUS are admitted to the intensive care unit 5-7 days after the onset of the disease, when class G immunoglobulins specific to the pathogen are already beginning to circulate in the blood. In this regard, the use of immunological tests can be effective to confirm the diagnosis of STEC infection. In our studies, enzyme immunoassay allowed us to detect antibodies to Stx2A in 63.3%, and to Stx2B in 43.3% of patients. Using immunoblotting, antibodies to Stx2A were detected in all sera obtained from patients, and in 66.7% of cases to Stx2B. Immunoblot analysis was characterized by higher sensitivity for detecting antibodies to Stx2, however, due to the presence of an immunological layer among healthy people, it is preferable to use ELISA analysis. In healthy donors with antibodies to Stx2, the antibody titer was significantly lower than in patients. Thus, laboratory confirmation of the diagnosis of STEC infection is difficult when conducting microbiological and molecular genetic studies, which is confirmed in this work. The effectiveness of laboratory diagnostics can be expanded by performing an ELISA aimed at detecting antibodies to Stx2A.