Could prestidigitation be used to clean poison off an enemy's arrow?

[awa]

that's not how rust or tetanus works

tetanus is a bacteria that can collect in rusts rough surface but nothing about rust produces the bacteria out of nothing.

D&d does not tend to care about normal dirty wounds only, not even in the more crunch heavy editions. So i would say no soiling just means it makes it dirty not covers it in poison.

I would allow it but i also doubt it is a good use of your action unless I'm mistaken you are trading a whole action to remove the poison from one attack. And that assumes he doesn't notice it if he does well drawing a new arrow is a free.

edit
also if rusty arrows were better than normal arrows you could just leave the arrow heads out in the rain for a bit and make them non-magical rusty.