A new look at the alimentary route of tuberculosis transmission using a rabbit model (experimental study)

Background. The increase in the number of cases of generalized tuberculosis infection with intestinal damage, especially in HIV-positive patients, underscores the need for further study of this problem. Tuberculosis is transmitted by airborne droplets; however, there are known cases of intestinal tuberculosis in which infection occurred through the alimentary route. Since such cases are extremely rare, there are likely specific immunological and epidemiological conditions that allow Mycobacterium tuberculosis to penetrate the intestinal wall and develop primary inflammation.

The aim. To study the possibility of an alimentary route of tuberculosis infection in immunocompetent and immunocompromised individuals using a reproducible rabbit model.

Materials and Methods. The experiment involved rabbits, divided into three groups. Animals were orally administered a suspension of a standard laboratory isolate Mycobacterium tuberculosis H37Rv. The first group included immunocompetent rabbits immunosuppressed with infliximab, the second group had animals reinfected against the background of immunodeficiency, and the third group included rabbits with a combination of drug-induced immunosuppression and chemically induced enterocolitis. To assess the results of infection, clinical observation, detection of MTB DNA in feces, skin test with ATR, pathoanatomical, histological and molecular genetic examination of organs were used.

Results. Despite the temporary shedding of MTB DNA in feces (60–70 %), no signs of tuberculous inflammation in the organs were present in animals in groups 1 and 2. In group 3, macroand microscopic signs of tuberculosis were detected in the lungs of 83.3 % of the animals and in the mesenteric/intrathoracic lymph nodes of 58.3 %. At the same time, no specific granulomatous intestinal lesions were found in any of the groups.

Conclusion. The development of tuberculous enterocolitis in rabbits following oral infection is unlikely. The alimentary route of infection can lead to generalized tuberculosis only when two key predisposing factors are present: systemic immunosuppression and previous damage to the intestinal barrier.

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