Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2001
Publication Date: N/A
Interpretive Summary: Respiratory diseases are among the most costly health problems in swine herds. Bordetella bronchiseptica is one of the bacteria which causes atrophic rhinitis (a disease which results in damage to the nose) and pneumonia in pigs. B. bronchiseptica produces several toxins which help it produce disease. The purpose of this experiment was to determine the role of one of these toxins, the dermonecrotic toxin, in causing disease. Pigs were infected with either bacteria which produced the dermonecrotic toxin or bacteria which did not. Turbinate atrophy and pneumonia were seen only in pigs given the bacteria which produced the toxin. Thus, the dermo- necrotic toxin of B. bronchiseptica is responsible for producing the lesions of turbinate atrophy and pneumonia seen in pigs infected with this bacteria. These findings are important in developing potential vaccines to protect against these diseases.
Technical Abstract: Bordetella bronchiseptica is one of the etiologic agents causing atrophic rhinitis and pneumonia in swine. B. bronchiseptica produces several purported virulence factors, including the dermonecrotic toxin (DNT) which has been implicated in the turbinate atrophy seen in cases of atrophic rhinitis. The purpose of this experiment was to determine the role of this toxin in pathogenesis by comparing the pathogenicity in swine of two isogenic DNT- mutants to their virulent DNT**+ parent strains. Two separate experiments were performed, one with each of the mutant/parent pairs. One-week old caesarian-derived, colostrum-deprived pigs were inoculated intranasally with the DNT**+ parent strain, the DNT- mutant strain, or PBS. Weekly nasal washes were performed to follow colonization of the nasal cavity, and the pigs were euthanized 4 weeks after inoculation to determine colonization of tissues and to examine the respiratory tract for pathology. There was evidence that colonization of the upper respiratory tract, but not the lower respiratory tract, was slightly greater for the parent strains as compared to the DNT- mutants. Moderate turbinate atrophy and bronchopneumonia were seen in most pigs given the parent strains, while there was no turbinate atrophy or pneumonia seen in pigs challenged with the DNT- mutant strains. Thus, production of DNT by B. bronchiseptica is necessary to produce the lesions of turbinate atrophy and bronchopneumonia seen in pigs infected with this organism.