Adherence of Bordetella bronchiseptica to swine nasal epithelial cells and its possible role in virulence.

Bordetella bronchiseptica phase I organisms adhered well to swine nasal epithelial cells cultured in vitro, while phase III variants exhibited feeble adherence to the same cells. Similarly, firm attachment of phase I organisms and poor adhesion of phase III organisms to nasal epithelium were demonstrated in experimentally infected piglets. Electron microscopic observations of nasal mucosa infected with phase I organisms showed preferential adherence to the cilia of nasal epithelial cells; the association of bacteria and cilia appeared to be mediated by fuzzy or string-like surface appendages which extended out from the bacterial cell wall. The ability to attach to epithelial cells was significantly reduced by heating the bacteria at 100 degrees C for 1 h or by pretreatment with 1 per cent formalin. Trypsin digestion treatment did not greatly reduce the adherence. Rabbit antisera to living or formalinised phase I organisms markedly impaired the attachment of the bacteria. However, antisera to heated phase I organisms or living phase III organisms did not show inhibitory effects. These data indicate that the heat labile surface component which is specific to phase I organisms may function in the adherence of the bacteria to swine nasal epithelium.