Invasion of epithelial cell monolayers by turkey strains of Pasteurella multocida

Two serotype 3,4:A strains of Pasteurella multocida that differ in virulence in turkeys were examined for their ability to invade epithelial cell monolayers grown in tissue culture. Both organisms were comparably adherent to cells of turkey kidney origin. However, the virulent strain (86-1913) penetrated primary turkey kidney epithelial cell monolayers at 10 times the level of the low-virulence vaccine strain. The virulent strain was also able to invade porcine epithelial cells (PK15) and feline epithelial cells (CRFK) in cell culture. Neither organism invaded rabbit epithelial cells (RK13). Invasion of turkey cells was prevented by inhibition of bacterial protein or RNA synthesis but not by pretreatment of the monolayers with periodate, trypsin, or neuraminidase. Invasion might be a mechanism of pathogenicity for this organism, contributing to colonization or virulence.