Enhanced Isolation of Brucella abortus from Lymphoid Tissues of Mice Orally Infected with Low Doses in a Two-Step Procedure

The main aspects of brucellosis have been studied in animal models to better understand the pathogenesis of the disease. Mice are the most common animal model of brucellosis. To verify that the infection has been successfully induced, it is necessary to assess the presence of Brucella in experimentally infected mice. Traditionally, high doses of Brucella have been used to establish detectable infection in oral murine models but prevent the emulation of natural pathogenesis. We propose the use of a low dose (1 × 106 CFUs) to establish a more realistic oral infection model. Using a two-step procedure consisting of selective broth enrichment followed by agar isolation, we were able to recover bacteria from gut-associated lymphoid tissues (mesenteric lymph nodes and Peyer’s patches), the spleen, and feces during the early and late stages of infection (1 h and up to 5 weeks). This technique promotes the study of early infection stages and systemic dissemination without the need for high doses to induce infection orally. It also demonstrates that Brucella remains in the intestinal-associated lymphoid tissues at time points when the infection is already systemically established.