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United States Department of Agriculture

Agricultural Research Service

Title: Early Colonization of the Rat Upper Respiratory Tract by Temperature Modulated Bordetella Bronchiseptica

Author
item Brockmeier, Susan

Submitted to: Federation of European Microbiological Societies Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 1999
Publication Date: N/A

Interpretive Summary: Bordetella bronchiseptica is a pathogen which contributes to respiratory disease in pigs, one of the most important disease problems facing the swine producer today. Although the organism is largely thought to be transmitted from animal to animal, studies have shown that it can survive in water, thus an environmental phase for this organism could also be important in its dissemination. When the bacteria are growing in the host a set of genes which help it survive are activated. When the bacteria are found in the environment, these genes are not expressed but others important for survival in the environment are. A recent report has shown that bacteria grown at room temperature adhered to cells from the respiratory tract better than those grown at body temperature, which may be another indication that environmental sources of infection are important. The ability of B. bronchiseptica grown at 37 C (body temperature) and 23 C (room temperature) to colonize the respiratory tract was investigated. Initially, statistically greater numbers of bacteria grown at 23 C adhered to the nasal cavity of the rats. These bacteria appeared to be quickly cleared to levels lower than the bacteria grown at 23 C by 4 h after inoculation and stayed lower until 48 h after inoculation when colonization levels were equal. These findings suggest that there may be increased adherence from an environmental phase to ensure bacteria survive initial clearance mechanisms until the genes important for survival within the host can be expressed. This information is important in determining the best way to control infection with this organism by interrupting the transmission process, as well as developing more efficacious vaccines.

Technical Abstract: The ability of nonmodulated Bvg**+ phase cultures, temperature modulated Bvg**- phase cultures, and a Bvg**- phase-locked mutant of Bordetella bronchiseptica to colonize the rat upper respiratory tract was investigated. Initially, greater numbers of the temperature modulated Bvg**- phase bacteria adhered to the nasal cavity of the rats. The temperature modulated Bvg**- phase bacteria appeared to be quickly cleared to levels lower than the Bvg**+ phase bacteria by 4 h after inoculation and stayed lower until 48 h after inoculation when colonization levels were equal to the Bvg**+ phase bacteria. The level of colonization with the Bvg**- phase-locked mutant of B. bronchiseptica was lower than that of the nonmodulated Bvg**+ phase, and temperature modulated Bvg**- phase cultures declined over time during the experiment. These findings suggest that there may be increased adherence from an environmental phase to ensure bacteria survive initial clearance mechanisms until switch to the Bvg**+ phase occurs.

Last Modified: 11/23/2014
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