Non-harmful bacterial invasion of cells
Survival of the host cell is in many cases dependent on the egress strategy of the pathogen. There are many examples documented in various species. The only case I found that's somewhat relevant to human cells was were mutant Legionella pneumophila, defective in the lytic pore complex, did not produce necrosis of the host cell. However, the cells did release the bacteria after a while, probably apoptosis due to accumulation.

EDIT: I found an article documenting Cryptococcus neoformans infection. 


  Cryptococcus neoformans causes disease in people with immune deficiencies such as AIDS. Upon infection, C. neoformans cells are ingested by macrophage immune cells, which provide a niche for survival and replication. After ingestion, macrophages can expel the fungi without causing harm to either cell type, a process named nonlytic exocytosis.