Pasteurella multocida and its role in porcine pneumonia.

Pasteurella multocida has been recognized as a contributor to debilitating and fatal porcine pneumonia for at least 120 years and there continues to be sustained, unabated high prevalence of the organism in cases submitted for diagnostic work up. Understanding of its role in disease has been limited, in part because of difficulty in reproducing the disease experimentally with capsular type A strains of P. multocida, the predominant type associated with porcine pneumonia. This limitation has stymied the development of improved methods for disease control. In this review, the reports of efforts to reproduce the disease are compared. Reports have indicated induction of pneumonia in combined infections with agents such as hog cholera virus, pseudorabies virus and Mycoplasma hyopneumoniae. Pneumonia has been induced with intratracheal or endobronchial inoculation of anesthetized swine using capsular type A strains. Substantial recent progress in understanding the putative virulence attributes and molecular genetics of P. multocida will likely lead to better understanding of the host-parasite and parasite-parasite interactions in porcine pneumonia associated with this organism. In particular, it seems important to consider the role of biofilm formation in the pathogenesis of this disease. Ultimately, this understanding should provide a foundation for better methods for induction of the experimental disease, development of improved diagnostics, development of better therapeutic/prophylactic pharmaceutical approaches and development of immunoprophylactic products.