RESUMO
OBJECTIVES: Actinobacillus pleuropneumoniae causes an often fatal infection of swine due to pleuropneumonia. To determine if inflammatory cytokines are associated with A. pleuropneumoniae-induced pneumonia, infected and noninfected animals were concomitantly administered saline or dexamethasone. METHODS: Twenty-four swine were treated with saline, A. pleuropneumoniae, dexamethasone, or A. pleuropneumoniae and dexamethasone (n = 6). The plasma levels of TNF-alpha, IL-1beta, IL-6, IL-8, and IL-10 were examined through time of necropsy (72 h). Gross pathology and histopathology was performed on all animals. RESULTS: Dexamethasone had no effect on A. pleuropneumoniae-induced increases in lung/body weight ratios. Gross pathology of the infected pigs included fibrinous pleuropneumonia with necrosis and hemorrhage in a focal to a multifocal pattern. Histopathology of infected pig lungs revealed necrotizing extensive, fibrinopurulent pneumonia with edema and fibrinopurulent pleuritis. Plasma IL-6 levels were elevated in A. pleuropneumoniae-infected animals beginning 6 h after infection. Dexamethasone treatment did not alter A. pleuropneumoniae-induced plasma IL-6 levels. A. pleuropneumoniae infection did not elicit plasma levels of TNF-alpha, IL-1beta, IL-8, or IL-10. CONCLUSION: These results suggest that the pneumonia caused by A. pleuropneumoniae infection is not due to the release of systemic inflammatory cytokines.
