Adherence ofBordetella bronchisepticaandPasteurella multocidato swine nasal ciliated epithelial cellsin vitro

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Abstract
A bacterial adherence assay using swine nasal turbinate fragments was established. Turbinate fragments were incubated withBordetella bronchisepticaorPasteurella multocidatype D at different concentrations or for different inbucation times at 37°C on a shaker at 120 rev/min.B. bronchisepticaphase I strains exhibited strong adherence to swine nasal ciliated epithelial cells. The number of adherent bacteria per cell increased when the bacterial concentration or incubation time increased (0, 15, 30, and 60 min); however, the number of adherent bacteria decreased after 3 or 6 hours' incubation due to the loss of cilia from cells. The optimal bacterial concentration and incubation time were 1 times 109organisms/ml and one hour respectively, which resulted in 7.48 ± 0.66 (Mean ± SEM;B. bronchisepticastrain 03) and 9.31 ± 0.54 (B. bronchisepticastrain 013) adherent bacteria per cell. In contrast toB. bronchisepticaphase I strains, rough phase strains ofB. bronchisepticaand allP. multocidastrains tested showed no adherence to swine nasal ciliated epithelial cells. AllB. bronchisepticaphase I strains could agglutinate calf RBC but rough phase strains could not. Furthermore, pretreatment ofB. bronchisepticaphase I organisms with 1 mg/ml or 2 mg/ml of trypsin significantly inhibited the adherence ofB. bronchisepticato ciliated epithelial cells; however, trypsin (2 mg/ml) treatment of bacteria did not decrease their ability to agglutinate calf RBC. From these results we conclude that, in addition to hemagglutinin, other proteinaceous components exist on the surface of virulentB. bronchisepticathat are sensitive to 2 mg/ml trypsin; these are suggested to be the adhesins for the adherence ofB. bronchisepticato swine nasal ciliatd epithelial cells.