Comparison of an infective avirulent and canine virulent Bordetella bronchiseptica.

Two Bordetella bronchiseptica isolates, S-55 and D-2, were evaluated in dogs for inducement of (i) infection, (ii) clinical bordetellosis, and (iii) histopathologic changes on tracheal and bronchiole tissues. Further, each isolate was characterized for variance in (i) toxicity for mice and (ii) intracellular proteins. Both S-55 and D-2 were detectable in test dog groups during the 26-day test period, although 545 times more D-2 was recovered than was S-55. In dogs inoculated with D-2, clinical infectious tracheobronchitis appeared in 4 days and continued for 22 days. Bordetellosis was not observed in dogs given S-55 or in noninoculated dogs. Tracheal and bronchiole tissues from dogs inoculated with the S-55 and D-2 isolates were microscopically examined for lesions. Dogs inoculated with S-55 did not have tracheal or bronchiole lesions. Lesions were not observed in noninoculated dogs. Dogs inoculated with D-2 had marked lesions in the tracheal and bronchiole tissues. The D-2 whole cells were an average 4.8 times as lethal as S-55 whole cells in mice (given intraperitoneal inoculation), whereas cell-free culture supernatants from S-55 and D-2 isolates were nontoxic. Cell-free sonicated extracts of S-55 and D-2 proved toxic to mice (intraperitoneal inoculation), but after the extracts were heated at 56 C for 30 minutes, both were nontoxic. Intracellular proteins of approximately 116,000 and 44,000 daltons were found in higher concentration in D-2 cells than in S-55 cells.