Phase variation affects long-term survival of Bordetella bronchiseptica in professional phagocytes

Several Bordetella bronchiseptica isolates were investigated for intracellular survival in macrophages. A significant number of viable bacteria of all strains could be recovered even after 96 h postinfection. In all cases bvg mutants of the B. bronchiseptica strains showed a significant survival advantage over the respective wild-type strains. The bacteria were already located in phagolysosomes early after uptake. Neither opsonization of the bacteria nor activation of the macrophages with gamma interferon or lipopolysaccharide prior to infection affected uptake and survival of the bacteria. Bordetella bronchiseptica is very closely related to B. pertussis, the etiological agent of whooping cough (26). Whereas B. per-tussis is an obligate human pathogen, B. bronchiseptica has a broader host range causing respiratory disease in several mam-malian species but only occasionally in man (26, 28). Both organisms produce a series of highly related virulence factors such as adhesins and the adenylate cyclase toxin (26). How-ever, only B. pertussis is able to produce the pertussis toxin interfering with regulatory G proteins in the cell membrane i