Human Bordetella bronchiseptica infection related to contact with infected animals: persistence of bacteria in host.

Within a period of 2 1/2 years, Bordetella bronchiseptica was isolated four times from a 79-year-old woman with bronchopneumonia. We have demonstrated by pulsed-field gel electrophoresis that this infection was related to contact with infected rabbits. The initial human B. bronchiseptica isolate had a phenotype characteristic of usual B. bronchiseptica clinical isolates; it produced toxin and adhesins, such as adenylate cyclase-hemolysin, filamentous hemagglutinin, and pertactin, and was able to induce lethality in a murine respiratory model. By contrast, although the three successive human isolates produced adhesins, they did not express adenylate cyclase-hemolysin and were unable to induce lethality. This implies that adenylate cyclase-hemolysin is required to induce lethality. We suggest that B. bronchiseptica may persist in the host, with expression of adenylate cyclase-hemolysin being essential for the initiation of infection and expression of adhesins being essential for persistence.