There are quite a few types of mouthwash on the market, and many of them contain alcohol. Alcohol has a reputation for killing bacteria; it does so by penetrating the cell walls of bacteria and rending them inactive.
Mouthwash Sans Alcohol
Cetylpyridinium chloride (CPC) is typically the active ingredient in mouthwash that does not contain alcohol. This acts in the same way that alcohol does. It dissolves the membrane around the cells that make up bacteria.
The Battle Between Mouthwash and Bacteria
The beauty of mouthwash is that it can reach into the tiny crevices and spaces in between teeth. Those are the places that harbour bacteria because your toothbrush cannot always clean those areas.