Treponema pallidum immobilization reaction

Treponema pallidum immobilization test (TPI) is a serological test used to diagnose syphilis. It is based on the ability of antibodies present in the serum of a patient with syphilis to immobilize live Treponema pallidum, the causative agent of syphilis.

To carry out RIBT, the Treponema pallidum Nichols strain grown on a special nutrient medium is used. A suspension of live motile Treponema pallidum is mixed with the test serum and incubated at a temperature of 36°C. Then the preparation is microscopically examined with an immersion system and the number of mobile and immobile (immobilized) treponemes in the field of view is counted.

The result is considered positive when more than 50% of the treponemes are immobilized. RIBT allows you to detect the disease in the early stages and evaluate the effectiveness of treatment. This test is more sensitive than other serological tests for syphilis.

RIBT was proposed in 1949 by American scientists Nelson and Meyer and is still widely used for laboratory diagnosis of syphilis.

RIT is a microbiological test based on thermoagglutination of Neisseria gonorrhoeae bacteria, which recover after exposure to IR radiation without visible growth during the first 24 hours; agglutination occurs on the third day and only at 37 C, as IR is destroyed, the enzymatic properties of N.gonorrhoeae are restored. In incubation samples stained with gelatin agar, a clear oval rod shape is visible under microscopy under light with a focus of red cells. This is a state of non-productive growth of test strains. The principle of the method is based on the ability of the studied microbial impurities to fix dyes without prior exposure to the penetrating power of IR radiation, followed by restoration of their properties upon irradiation for 5 minutes near 800 nm. To detect residual N. Gonorrhoea DNA, a so-called “dye fixation test” can be used in combination with a reduced RNA enzyme. As a result, RIBT obtains a positive result only after 5 days if the subject is sick with gonococcal infection.