When antibiotics fail to cure UTIs, it usually means that it has become antibiotic resistant. What causes UTIs is when bacteria attaches itself to the bladder walls. After awhile antibiotics can fail to kill that bacteria because the bacteria becomes resistant to antibiotics. Cranberry will kill that bacteria and cause it to slough off the bladder walls. Cranberry can be given as the pure unsweetened juice that you can get from a health food store. A couple of tablespoons a day mixed in a little canned milk to make it less bitter and given with an oral syringe. After this is under control, cranberry extract capsules can be given every couple of days or if it starts to flare up again. Giving alot cranberry over an extended period of time really is not necessary, just give it periodically as a preventative. Dry dog food can trigger this for some reason. Even prescription dog foods. Also tap water can do it in some areas, sometimes it can affect the ph balance of the urine. If you can find a dog food that has a lower magnesium and ash content ,eliminate fish completely from the diet and increase the amount of water your puppy drinks a little more it can all help.