Fig. 1

Lesions caused by Pasteurella multocida type A in experimentally challenged pigs. a. Lung, group 2. Focally extensive hemorrhagic pleuropneumonia in the cardiac lobe with fibrin on the pleura. b. Thoracic cavity, group 7. Diffuse fibrinous pleuritis and pericarditis (*). c. Heart, group 3. Diffuse fibrinous pericarditis. d. Abdominal cavity, group 3. Fibrinous peritonitis. e. Lung, group 2. Coagulation necrosis area in the lung parenchyma (*), surrounded by abundant inflammatory cells, mild proliferation of connective tissue and suppurative exudate in the bronchioles (thin arrow). HE. Bar, 100 μm. f. Lung, group 2. Abundant (+++) inflammatory exudate, predominantly suppurative, intra-alveolar in a coagulation necrosis area on the lung parenchyma. HE. Bar, 10 μm. g. Spleen, group 5. Multiple splenic infarcts with fibrin threads on the capsule. h. Lung, group 2. Abundant antigen labeling of P. multocida (red labeling) in a coagulation necrosis area in the lung and between degenerated inflammatory cells. Bar, 50 μm. i. Lung, group 2. Coagulation necrosis area in the lung with P. multocida antigen labeling (red spots) in the cytoplasm of phagocytic cells. Bar, 5 μm. j. Spleen, group 5. Moderate (++) antigen labeling of P. multocida (red labeling) in a necrotic area. Bar, 20 μm. Immunohistochemistry, streptavidin-biotin-peroxidase method (LSAB™) with 3-amino-9-ethylcarbazole (AEC) and counterstaining with Mayer’s hematoxylin