Actually, it sort of
does treat it--which is why we're a little worried that if we have to switch over to Cephalexin, it might mean trouble with the leptospirosis (if she has it).
Clavamox, which she's on now, is just Amoxicillin with an extra ingredient, clavanoic acid or some such... For lepto, the dogs are getting two weeks of Amoxicillin followed by two weeks of Doxycycline. So the Clavamox is actually a fairly good choice.
If she has lepto, we'll have to follow up the Clavamox with a couple of weeks of Doxy once her face infection has cleared up.