Bordetella bronchiseptica has a BvgAS-controlled cytotoxic effect upon interaction with epithelial cells

The interaction between the respiratory pathogen Bordetella bronchiseptica and epithelial cells was studied. After 2-3 h, B. bronchiseptica strains exerted a strong cytotoxic effect on HeLa cells which was evident by rounding of the cells and detachment from the substrate and which ultimately resulted in total disintegration of the host cell. Production of this cytotoxic activity appeared to be regulated by the BvgAS sensory transduction system, which coordinately regulates many B. bronchiseptica virulence factors, since bacteria cultured in the presence of sulfate anions, inhibitors of the BvgAS response, did not exhibit this effect. Furthermore, spontaneous phase variants of B. bronchiseptica strains adhered to HeLa cells but were not cytotoxic. The cytotoxic component is presumably not secreted because the bacterial culture supernatant was not cytotoxic for HeLa cells. Besides HeLa cells other human epithelial cell lines such as Chang cells, larynx HEp-2 cells and lung NCI-H292 cells were sensitive to the cytotoxic activity of B. bronchiseptica. These results suggest the presence of a novel BvgAS-regulated virulence factor in B. bronchiseptica.