Pathogenesis and pathobiology of brucellosis in livestock.

Brucellaspecies are facultative, intracellular, Gram-negative bacteria with marked tropism for the pregnant reproductive tract of domestic animals. All Brucella species establish persistent infection in the reticuloendothelial system of their natural hosts. The mechanisms of placenta localisation, trophoblast tropism and abortion are poorly understood. A complete picture of the molecular determinants and mechanisms of the cell internalisation process began to emerge only recently. Cyclic beta-1,2-glucan is a molecule secreted into the periplasm of Brucella and is required for intracellular Brucella to avoid fusion of the phagosome with lysosomes. The type IV secretion system translocates Brucella effector proteins into host cells and is critical for both survival and replication of Brucella in infected host cells. Some aspects of the pathogenesis and pathobiology of brucellosis in productive domestic animals are discussed in this section.