Figure 3. Histopathological and immunohistochemical features of formalin-fixed, paraffin-embedded biopsy specimens collected from the right and left kidney allografts procured from a donor who died of murine typhus, from a study describing the transmission of Rickettsia typhi from an organ donor to 2 kidney transplant recipients, Texas, 2024. A) When stained with hematoxylin and eosin, both allografts showed multifocal, interstitial, and predominantly mononuclear peritubular infiltrates, associated with focal endarteritis (thin arrows), features of acute tubular injury, including epithelial attenuation with loss of apical cytoplasm, and pigmented casts (large arrow). B) Glomeruli displayed moderate mesangial hypercellularity and tuft adhesions to the Bowman’s capsules (arrows) and intracapillary and mesangial phagocytic foam-cells. C) Short chains comprising small, rod-shaped bacteria were revealed in glomerular capillaries by the Warthin–Starry silver impregnation staining technique. D–F) An immunohistochemical stain for typhus-group rickettsiae revealed intact bacteria within endothelial cells of inflamed small vessels and vascular spaces of mesangial capillaries (arrows) and phagocytized bacterial antigens in the cytoplasm of glomerular foam-cells (arrows). Original magnifications ×400 (A, B, and E) and ×1,000 (C, D, and F).