M. suis infection induces endothelial cell detachment and activation. Transmission electron micrographs of aortic sections. A. ECs (black arrows) of pigs infected with M. suis (black arrowheads) are characterized by extensive microvilli (MV) formation. Scale bar = 4 μm; B. Absence of ECs/EC detachment and remaining vacuolar cells. Scale bar = 4 μm; C, D. M. suis was detected in the aortic sub-cellular tissue by nanogold silver intensification staining. Scale bar = 0.2 μm (C); Scale bar = 0.5 μm (D); E. Endothelial cells (ECs) of uninfected control pigs showing normal ultrastructure. Scale bar = 4 μm. Abbreviations: Co, collagen; L, lumen; PV, plasmalemma vesicle; N, nucleus; SP, silver precipitates; RM, tunica media; and VC, vacuolar cell.