|Gentry-Weeks, C - CO STATE U., FT. COLLINS|
|Magyar, Tibor - VET. MED. RES. INST., HU|
Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 1996
Publication Date: N/A
Technical Abstract: B. bronchiseptica is associated with pneumonia and atrophic rhinitis in swine. To assess the importance of virulence factors in vivo, we have developed an experimental model using 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 yielded an average of 31 x 10*6* cfu; by day 15 the number dropped to 14 x 10*6* cfu. In the first experiment, lethality by day 11 PI was 20%, compared to 33% in the second experiment. Pigs were necropsied at day 11 or 15 PI. Turbinate averaged >10*8* cfu/g, whereas trachea and lung averaged between 10*6* and 10*7* cfu/g. Minimal to moderate turbinate atrophy and mild to marked pneumonia were seen. By day 15 PI, there were moderate to marked peribronchial fibrosis and loss of cilia. A second strain, B133, was tested in this model and found to be equally virulent based on degree of colonization, lethality, clinical signs, and histology. We intend to test isogenic mutants of 4609 and B133 to determine the importance of putative virulence factors in vivo.