Factors influencing the degree of in vitro bacterial adhesion to ovine mammary gland epithelial cells.

Bacterial adhesion to mammary gland epithelial cells (EC) may play a role in the pathogenesis of mastitis. In vitro adherence systems have been developed to study mastitis in cattle but little has been done in sheep. In this work, a method is described for obtaining mammary gland cell preparations containing greater than or equal to 65% EC from live or dead ewes, using a Ficoll-Hypaque flotation method (cell viability = 70-90%). An in vitro adhesion assay procedure was also developed to study the interaction between EC and ovine mastitis bacterial strains. It was observed that, under the test conditions, adherence increased as the incubation time was prolonged from 30 to 120 min (P less than 0.05). Adhesion was greater at incubation temperature of 37 degrees C than at 22 degrees C (P less than 0.001). An acidic pH (5.9) was associated with an increase in adhesion, when compared with a higher pH (7.2; P less than 0.05). Tween 20, Tween 80 and bovine serum albumin helped to eliminate a background of unbound bacteria from the test slides, but they also inhibited adhesion to some strains. Strain differences in adhesion and in ability to form a background were also observed. Some of these findings may have in vivo implications.