Don't know if you're still having trouble with this but I learned quite about infections with my old Doberman years ago. Any time I have a dog who has a reoccurring infection of ANY type, I go to colloidal silver. I have a machine & make my own but you can buy it at any health food store. My machine makes a very fine particle colloidal silver so it's more user friendly than some of the other types. For the type I make I can use as much as a shot glass full per dose. For the stuff you buy at a store, go by the directions. I start out giving this orally 3 times a day for the first 3 days, then two times per day for the next 7 days. In the mean time, I also take the C. Silver & put it in a glass & dunk the paws in it. (C.Silver does not like plastic, metal, or sunlight. These things cause the silver to fall out of suspension. So you store it in a dark glass container. You can put it in a syringe (no needle) to administer it but you don't store it there. So when I dunk paws, I put it in glass. Give it five minutes then dry those paws. I use those groomer towels that sucks the moisture out of the coat after a bath. Dry, dry, dry. My dogs are so used to me doing this sort of thing they don't give me any grief. This stuff is good for bacterial, viral, & fungal. My dog got so bad with staph infections that he was living on high doses of antibiotics. I did the above with my dog as well as using medicinal clay & cleared up the staph & he never had it again in his life. That was after 3 years of constant staph infection battles. I've used it for yeast, fungal, bacterial infections successfully. I have also used it with a glass spray bottle. A lot of times what happens is the body gets bogged down trying to fight this that it suppresses the immune system. So the silver does not bog down the immune system but you don't want to get carried away because C. Silver knows not the difference between good & bad flora & fauna. So rid the body of the problem then stop using it until you need it again (if you do).  
I have used this in people, livestock, & dogs. It's amazing stuff. You can use it internally & externally. You can even use it for eye drops if there is a scratch or unknown irritation in the eyes. Amazing stuff.