Invasion of HeLa cells by Bordetella bronchiseptica

Invasion, defined as adhesion to, followed by entrance into HeLa cells by Bordetella bronchiseptica was determined by (i) specific staining of intracellular bacteria and (ii) counting of viable intracellular bacteria after killing extracellular bacteria with colistin. It was demonstrated for the first time that B. bronchiseptica, like Bordetella pertussis and Bordetella parapertussis, is able to invade HeLa cells. Comparison of the invasiveness of Bvg+ and Bvg- B. bronchiseptica showed that B. bronchiseptica, in contrast to B. pertussis, invaded HeLa cells in both phases. The number of viable intracellular bacteria isolated after invasion of bacteria in the Bvg- (flagellated) phase was ten-fold lower than when Bvg+ (fimbriated) bacteria were used. Strains which are deficient in the production of either FimX or Fim2 fimbriae were as invasive as wild-type B. bronchiseptica, which indicates that not these fimbriae but probably filamentous haemagglutinin (FHA) is the major adhesin of B. bronchiseptica.