Interaction of Corynebacterium pseudotuberculosis with ovine cells in vitro

Caseous lymphadenitis is an infectious and contagious disease caused by Corynebacterium pseudotuberculosis, with a worldwide distribution and high prevalence in small ruminant populations. This disease causes significant economic loss in small ruminants through reduced meat, wool, and milk production. C. pseudotuberculosis can also affect horses, domestic and wild large ruminants, swine, and man. It is considered an occupational zoonosis for humans. As part of in vitro investigations of the pathogenesis of C. pseudotuberculosis, this study analyzed its capacity to adhere to and invade the FLK-BLV-044 cell line, derived from ovine embryonic kidney cells. C. pseudotuberculosis showed a measurable capacity to adhere to and invade this cell line with no significant differences between the four strains assessed. The incubation of the cell line at 4ºC, pre-incubation with sugars, complete and heat inactivated antiserum, and heat-killed and ultraviolet-killed bacteria produced a significant (P < 0.05) decrease in the invasion efficiency or inability to invade the cell line. Plate counting and fluorescence studies showed intracellular bacteria for up to 6 days. Non-phagocytic cells may therefore act as a suitable environment for C. pseudotuberculosis survival and play a role in the spread of infection and/or maintenance of a carrier state.