FN1 and infection: In the early stage of infection, the invasion process is largely dependent on the outer membrane proteins (OMPs) of Bartonella, among which TAAs, for instance, BadA of B. henselae [28,63], variably expressed outer membrane proteins (Vomps) of B. quintana [64] and Bartonella repeat proteins of B. bacilliformis [65] which are crucial for attaching to various extracellular matrix (ECM) components (collagen, laminin, fibronectin [Fn]) and membrane proteins of host cells.