Abstract: To clarify the role of the 43 ku outer membrane protein (43K OMP) in the adhesion of Fusobacterium necrophorum to cells, the mouse mammary epithelial cells and the recombinant protein or the natural protein were co-incubated in this study, and the adhesion of the 43K OMP of F.necrophorum was observed under a laser confocal microscope. Meanwhile, the adhesion inhibition assay with antibodies against the recombinant 43K OMP or the natural protein was used to determine the effect of the 43K OMP on the adhesion of F. necrophorum to host cells, and the effect of 43K OMP gene deletion on the adhesion of F. necrophorum to host cells was investigated using deletion mutant strain. Immunofluorescence results showed that the natural 43K OMP and recombinant 43K OMP could bind to the cell membrane of mouse mammary epithelial cells. When mouse mammary epithelial cells or mouse liver cells were preincubated with the natural 43K OMP, the adhesion of F. necrophorum significantly decreased (P < 0.05). When F. necrophorum was preincubated with polyclonal antibody or monoclonal antibody against the recombinant 43K OMP, the adhesion of F. necrophorum to mouse mammary epithelial cells or mouse liver cells significantly decreased compared with the negative serum control and the no antibody control (P < 0.05). The number of bacterial cells attached to cells was higher with F. necrophorum A25 strains than that of the mutant strain A25Δ43K OMP(P < 0.01), The 43K OMP gene deletion reduced the binding of F. necrophorum to mouse mammary epithelial cells or mouse liver cells by 94.4% and 90.4%. Therefore, the 43K OMP plays a key role in the adhesion of F. necrophorum to host cells, and further study of the adhesion mechanism will provide a theoretical basis for revealing the pathogenic mechanism of F. necrophorum.

Key words: Fusobacterium necrophorum, 43K OMP, bacterial adhesion