Figure 3. A) Section of an aortic valve from a patient with Bartonella endocarditis. Note the extensive fibrosis of the connective valve tissue (arrowhead), the vegetation (*), and the low inflammatory infiltrate of the valve tissue (hematoxylin-phloxine-saffron, original magnification 100x). B) Resected valve with Bartonella quintana infection showing darkly stained bacilli consistent with Bartonella. Note the numerous clusters of argyrophilic bacteria present in the valvular vegetation (Warthin-Starry silver, original magnification 1,000x). C) Immunohistochemical detection of B. quintana in a resected valve from a patient with Bartonella endocarditis. Note the extracellular distribution of the bacterial colonies (*) in the valvular vegetation (polyclonal antibody and hematoxylin counterstain, original magnification 250x).