In theory. Penicillin is pretty difficult to get on its own though. Lots of other shit will grow with it and you might hurt someone as much as you help them if you don't strain it out. Better off making sulfa drugs. I've done that before and could again if we get ingredients.

Hopefully it won't come to that though. Ethanol cleaning a wound should be okay, especially if it's not a very deep wound. We also have just plain old soap.

Make sure you boil the water; I'm not sure if the river is safe to drink from without boiling. Unless you've been drinking it already and you're fine, in which case you're either ten billion percent lucky or it really is safe.