Binding and activation of plasminogen at the surface of Fusobacterium necrophorum.

Fusobacterium necrophorum is a gram-negative, anaerobic bacterium, which has been suggested to be a normal inhabitant of the oral flora. In rare cases, it can invade the tonsils and deeper tissues, causing the serious condition Lemièrre's syndrome. Recruitment of host plasminogen is a well-known bacterial virulence mechanism, and plasmin activity at the bacterial surface is thought to be important for bacterial invasion. Herein we show that plasminogen can be recruited to the surface of F. necrophorum, that surface-bound plasminogen is more easily converted to active plasmin than plasminogen in buffer, and that bound plasminogen is protected against inactivation by α2-antiplasmin. These findings add to the understanding of the pathogenesis of Lemièrre's syndrome.