Fat globule membrane of sow milk as a target for adhesion of K88-positive Escherichia coli.

Membrane adhesion of K88-positive Escherichia coli was studied on intestinal brush-border membranes on 237 Finnish Landrace pigs. Forty-one per cent of the brush-border membrane preparations aggregated E. coli (positive adhesion). Similar dualism of adherence/nonadherence was observed on sow milk fat globule membranes. Washed milk fat globules (washed cream) can be used as a convenient source of material for adhesion studies. Bacterial adherence on to milk fat globules is evident as agglutination of the globules (dark-field microscopy). By this procedure the sows can be typed according to their receptor phenotype. This simple principle of fat globule agglutination due to receptors for K88-positive E. coli might be complicated by SigA-mediated bacterial adherence. Fat globule membranes were shown to contain SigA, which may act as a mediator of bacterial adherence onto fat globules. The significance of this adhesive property of milk fat globule might be to provide alternative receptors for E. coli thus preventing bacterial adhesion on to gastro-intestinal epithelium of the offspring. Sow milk fat globules can be used for typing E. coli for membrane adhesiveness. The adhesiveness of the strains showed a good correlation with the presence of the K88 antigen, as well as the hydrophobicity of the bacterial strain as determined by an association on Phenyl-Sepharose beads.