Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: February 25, 1998
Publication Date: N/A
Bordetella bronchiseptica is a primary etiologic agent of swine atrophic rhinitis and pneumonia. Resistance of this organism to the bactericidal effects of complement and specific antibody has been proposed as a virulence factor. The present study demonstrates 85-100% survival of two virulent swine isolates tested in a colony count assay using serum from rabbits hyperimmunized with B. bronchiseptica and supplemented with guinea pig complement. Survival of E. coli incubated under similar conditions in the presence of specific antibody was <0.0001%. A radial diffusion killing assay also demonstrated serum resistance of the B. bronchiseptica isolates tested. Southern blotting revealed that these isolates, as well as a large number of additional swine and rabbit strains, contain the brkAB locus, which is required for serum resistance in the related human pathogen Bordetella pertussis. However, serum resistance of both a naturally occurring brk mutant and one constructed in vitro is only slightly reduced as compared to wild type strains. Serum resistance may also be independent of the bvg locus, which controls expression of many virulence factors of B. bronchiseptica, since modulated cultures and a bvgS mutant displayed only a partial reduction in survival.