Submitted to: Journal of Comparative Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/1996
Publication Date: N/A
Interpretive Summary: Bordetella bronchiseptica is a bacteria that is associated with pneumonia and an upper respiratory tract disease of pigs termed atrophic rhinitis. This bacteria colonizes cells that line the respiratory tract. The bacteria produces several types of molecules that could potentially mediate adherence of the bacteria to the nasal cells; some strains also produce several types of toxins. In this study, we have created a porcine model t study adherence of B. bronchiseptica to the porcine respiratory tract. In this model, we can measure the degree of colonization of various segments of the respiratory tract through bacterial culture and light microscopy. In addition, this model can be used to determine the relative virulence of B. bronchiseptica strains. We will use this model in the future to test mutant strains of B. bronchiseptica which lack specific adherence molecules or toxins. Our long term goal is to identify B. bronchiseptica virulence factors vital to the disease process and develop vaccines or other therapies to decrease disease incidence and disease severity.
Technical Abstract: Studies assessing the importance of virulence factors of Bordetella bronchiseptica in vivo require a suitable system that yields multiple parameters. We have developed an experimental model system in seven- day-old colostrum-deprived, cesarean-derived pigs. In two different experiments a total of 11 pigs were inoculated intranasally with 1 x 10**6 cfu of the virulent strain 4609. At 3 days post-inoculation (PI), nasal washings had an average of 3.1 x 10**6 cfu; by day 15 the average was 1.4 x 10**6. One of five pigs died in the first experiment and 1/6 in the second. Turbinate and trachea averaged >10**8 cfu/g, whereas lung averaged between 10**7 and 10**8 cfu/g. Moderate turbinate atrophy was present in pigs by 11 days PI, and peribronchiolar fibrosis was present at 15 days PI. By immunocytochemistry all pigs had bacterial antigen in ciliated cells of turbinate, trachea, and lung; fewer pigs had bronchial bacteria. Bacteria antigen was also present in some bronchioles and within the cytoplasm of pulmonary macrophages and neutrophils. A second set of pigs was inoculated with another strain of B. bronchiseptica, B133, and produced a similar level of bacterial colonization as determined by nasal washing and organ culture, lethality, turbinate atrophy, microscopic lesions, and immunocytochemical localization of antigen. This work establishes a model system to study virulent strains of B. bronchiseptica and is useful for comparing strains and isogenic mutants deficient in putative virulence factors.