An immunocompromised murine model of chronic Bartonella infection.

Bartonella are ubiquitous gram-negative pathogens that cause chronic blood stream infections in mammals. Two species most often responsible for human infection, B. henselae and B. quintana, cause prolonged febrile illness in immunocompetent hosts, known as cat scratch disease and trench fever, respectively. Fascinatingly, in immunocompromised hosts, these organisms also induce new blood vessel formation leading to the formation of angioproliferative tumors, a disease process named bacillary angiomatosis. In addition, they cause an endothelial-lined cystic disease in the liver known as bacillary peliosis. Unfortunately, there are as yet no completely satisfying small animal models for exploring these unique human pathologies, as neither species appears able to sustain infection in small animal models. Therefore, we investigated the potential use of other Bartonella species for their ability to recapitulate human pathologies in an immunodeficient murine host. Here, we demonstrate the ability of Bartonella taylorii to cause chronic infection in SCID/BEIGE mice. In this model, Bartonella grows in extracellular aggregates, embedded within collagen matrix, similar to previous observations in cat scratch disease, bacillary peliosis, and bacillary angiomatosis. Interestingly, despite overwhelming infection later in disease, evidence for significant intracellular replication in endothelial or other cell types was not evident. We believe that this new model will provide an important new tool for investigation of Bartonella-host interaction.