Serologic Responses and Kinetics of B. abortus Biotype 1 Infection in Sprague-Dawley Rats

Background: Brucellosis is an important zoonotic disease in animals and humans caused by Brucella abortus. The pathogenesis and immune responses of B. abortus is mainly studied in mice and cattle. The serologic responses as well as the kinetics and distribution of bacteria were measured for 8 weeks after infection of Sprague-Dawley (SD) rats with B. abortus biotype 1. Methodology: Thirty-two SD rats received an intraperitoneal dose of 1×10 10 colony-forming units (CFU) of B. abortus biovar 1 isolated from cattle in Korea. At regular intervals after infection the rats were randomly bled for serologic studies and euthanatized for bacteriological examinations. Results: Sera were found positive for B. abortus specific antibody response by rose bengal plate test (RBPT), tube agglutination test (TAT) and plate agglutination test (PAT) at one week after infection. The peak antibody titers were recorded at 5 weeks after infection by the TAT and PAT then the titer gradually decreased until the end of the study. After experimental infection B. abortus was disseminated in blood and lymphoid tissues (spleen, liver and kidney). The persistence of B. abortus in blood was noted for short time, up to 5 weeks of infection. Bacterial persistence was recorded in the spleen throughout the experiment. No bacteria were cultured from the liver and kidney at 6 weeks after infection. Conclusion: The serologic responses and distribution of B. abortus in SD rats following experimental infection suggests that SD rats can clear the infection after a single exposure which will be helpful for the diagnosis of brucellosis.