An Intracellular Pathogen Uses One of Three Major Strategies to Survive

Short Answer

An intracellular pathogen uses one of three major strategies to survive and replicate once inside the host cell, as shown in the schematic drawing below. Indicate which strategy (1, 2, or 3) each of the following pathogens employs for this purpose. Your answer would be a three-digit number composed of digits 1 to 3 only, e.g. 332.

( ) Listeria monocytogenes
( ) Legionella pneumophila
( ) Shigella flexneri