It's speeding it up. You don't even need to look at medications for this. Just grab a petri dish of E. coli, spread them around real good, give them a bubble bath with antibacterial soap, incubate for 24 hours, and voila! You still get colonies spread throughout the dish.
Dirty hands? Grab some HCl instead! That'll do it.

As for our part, then yes, it's slowing natural selection. But hey, what is, doesn't have to be ought.