It is amazing and frightening at the same time. The other day I was reading somewhere that micro organisms on the surface of spacecraft survived on the cleaning liquid that is designed to kill them.
But it's not like they take old spacecraft sterilized with these solutions, bring them back, and try the liquid again?
Yes, I'm sure there is some kind of selection, but it should be more of a one-shot affair, not a continous cycle, like how it with anti-biotics and resistant strains.