from Kevin Moreau and Frank Lafont writing in Bacterial Pathogenesis: Molecular and Cellular Mechanisms:
Most invading bacteria enter the host cell by using either a triggered or a zippered mechanism. The former depends on membrane ruffles induced by injection of bacteria-derived effectors into the eukaryotic cell. A hallmark of the latter is a "sliding" of the bacteria into the cell through a clathrin-mediated structure, which is distinct from the pits in conventional clathrin-mediated endocytosis. Bacteria hijacking either of these mechanisms can also take advantage of signalling platforms activated within specialized membrane domains (lipid rafts). At the entry site, activated signalling pathways regulate the fate of the invading microorganism. Bacteria may then replicate in either cytoplasmic or vacuolar niches. Alternatively, the host immune system can deal with the infection and target the pathogen for elimination via several degradation pathways (notably including autophagy).
Further reading: Bacterial Pathogenesis: Molecular and Cellular Mechanisms