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Title: Contribution of Bordetella bronchiseptica Type III secretion system to respiratory disease in swine

item Brockmeier, Susan
item Nicholson, Tracy
item Loving, Crystal
item Register, Karen

Submitted to: American Society for Microbiology General Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2011
Publication Date: 5/21/2011
Citation: Brockmeier, S., Nicholson, T.L., Loving, C.L., Register, K.B. 2011. Contribution of Bordetella bronchiseptica type III secretion system to respiratory disease in swine [abstract]. American Society for Microbiology 2011 Annual Meeting. Abstract No. 1494.

Interpretive Summary:

Technical Abstract: Background: The type III secretion system (TTSS) of gram negative bacteria allows injection of effector proteins directly into the cytosol of eukaryotic cells. Previous studies have demonstrated that the B. bronchiseptica TTSS plays a role in the persistent bacterial colonization of the trachea of mice and rats by modulating host immune responses. We hypothesized that the TTSS would be necessary for B. bronchiseptica persistence in the swine respiratory tract. Methods: To investigate the role of the TTSS in Bordetella pathogenesis in swine, we constructed mutants containing an in-frame deletion of the bscN gene in KM22, a virulent B. bronchiseptica swine isolate. This gene encodes an essential component for TTSS secretion across bacterial membranes. We compared this mutant to KM22 for its ability to colonize and cause disease. Sixteen pigs each were inoculated intranasally with 10**6 CFU of either wild-type KM22, the TTSS mutant of KM22, or PBS as a control. Nasal colonization was determined by performing nasal washes on days 1, 3, 5, 7, and weekly thereafter through day 56 after inoculation. Tracheal and lung colonization was determined by euthanizing 4 pigs from each group on days 7, 14, 28 and 56 after inoculation. Results: Colonization of the TTSS mutant was similar to wild-type KM22 in the nasal cavity throughout the experiment. Colonization of the TTSS mutant was similar to wild-type KM22 in the trachea and the lung on day 7, but was significantly lower after that. In addition, fewer pigs (6/16) inoculated with the TTSS mutant developed pneumonic lesions than pigs inoculated with the wild-type KM22 (14/16). Conclusion: Our results indicate that the TTSS is required for optimal colonization in the lower respiratory tract and disease severity in swine.