As mentioned in a previous writeup, Listeria is a type of bacteria associated with food poisoning epidemics. What is particularly interesting about listeria, however, is how it affects one's cells.
There is a ActA protein on its surface that sticks to and activates actin regulating complex Arp2/3. These, now active, actin regulators nucleate the polymerization
of actin microfilaments
which trail behind the bacteria like a comet's tail as it is propelled across the cytoplasm
and into the cell wall. Eventually the bacterial causes the cell wall to bulge and finally release the bacteria into a neighboring cell. Thus, the bacteria never has to enter the intracellular space where it might get attacked by the immune system
. Bacteria called Shigella and Rickettsiae behave in a similar manner.