Influence of potential virulence determinants on Bordetella bronchiseptica-induced ciliostasis

Abstract

Eighteen strains of Bordetella bronchiseptica, selected on the basis of previously determined phenotypic characteristics, were examined for their ability to induce ciliostasis in canine tracheal outgrowth cultures. Fifteen strains grown on brucella agar caused ciliostasis. Strains that did not cause ciliostasis were stable, nonpiliated, and nonhemolytic, they did not produce extracellular adenylate cyclase, and were morphologically indistinguishable from rough-phase variants on brucella agar. Plasmids were detected in only five of the strains which induced ciliostasis, transfer of plasmids from four of these strains to one which did not induce ciliostasis did not alter its virulence or colony morphology. All strains which were hemolytic on Bordet-Gengou agar produced extracellular adenylate cyclase. Two nonhemolytic strains, one which produced only rough colonies on brucella agar, also induced ciliostasis. Two types of colony (phase) variation were observed: one recognizable on both brucella agar and Bordet-Gengou agar at frequencies of less than or equal to 10(-2), associated with multiple loss of virulence determinants, and the other recognizable only on Bordet-Gengou agar at frequencies of greater than or equal to 10(-2), associated with flagellum expression. The possession of readily detectable somatic pili was the only phenotypic characteristic consistently associated with the ability to induce ciliostasis. Formalin-killed and chloramphenicol-inhibited B. bronchiseptica strain 110H organisms had detectable pili and attached to cilia, but did not cause ciliostasis. Protease-treated B. bronchiseptica strain 110H organisms did not have detectable pili and in the presence of chloramphenicol did not attach to cilia. Attachment to cilia, although not in itself sufficient to cause ciliostasis, is intimately associated with and may be required for the induction of ciliostasis by B. bronchiseptica strains.