[katieHaylor (OP)]

Nico asks:

How does detergent kill bacteria?

Can you help?

[wolfekeeper]

Detergents aren't very toxic to bacteria, they can mostly survive it. Detergents are primarily used to remove fats and oils from surfaces that would otherwise provide a growth medium for bacteria.

[Bored chemist]

It rather depends on what detergent you choose.
Some of the quaternary ammonium compounds are used as biocides as well as detergents.
They kill many bacteria by disrupting the  cell membranes.