Submitted to: Cellular Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/2/2004
Publication Date: 5/20/2005
Citation: Fretin, D., Fauconnier, A., Kohler, S., Halling, S.M., Leonard, S., Nijskens, C., Ferooz, J., Lestrate, P., Delrue, R.M., Danese, I. 2005. The sheathed flagellum of b. melitensis is involved in persistence in a murine model of infection. Cellular Microbiology. 7(5):687-698. Interpretive Summary: Bovine brucellosis causes economic losses and wildlife serves as a reservoir. Though some vaccines strains have been shown to have a degree of efficacy among some wildlife species, the live vaccine strains persists in many vaccinated animals for months. We have identified a pathway necessary for persistence that can be modified in vaccine strains, potentially eliminating vaccines in the environment.
Technical Abstract: Persistence of infection is the keystone of the ruminant and human diseases called brucellosis and Malta fever, respectively, and is linked to the intracellular tropism of Brucella spp.. While described as non motile, Brucella spp. have all the genes except the chemotactic system, necessary to assemble a functional flagellum. This study was conducted to determine if these genes are expressed and are playing a role in some step of the disease process. We demonstrated that in the early log phase of a growth curve in 2YT nutrient broth, B. melitensis expresses genes corresponding to the basal (MS ring) and the distal (hook and filament) parts of the flagellar apparatus. Under these conditions, a complete polar flagellar stucture sheathed by an outer membrane is visible by transmissible electron microscopy. We evaluated the effect of mutations in flagellar genes of B. melitensis encoding various parts of the structure, MS ring, P-ring, motor protein, secretion apparatus, hook and filament. None of these mutants gave a discernable phenotype as compared to the wild type strain in cellular models of infection. In contrast, all these mutants were unable to establish a chronic infection in mice infected via the intraperitoneal route, raising the question of the biological role(s) of this flagellar appendage.