If a culture was done then the antibiotic should have been chosen which was known to work with the bacteria present. That does make me wonder if your dog has Cystitis if test now show the infection is cleared. Cystitis is when your dog's bladder becomes inflamed. It is believed that infections, polyps, tumors and stones contribute to this condition, but the actual cause is unclear. Typical symptoms are straining to urinate, frequent urination, straining to urinate, difficulty urinating and blood in the urine.
So your next step is to ensure the bacteria has been taken care of by the antibiotics. If it has, then you should consider imaging to rule out other causes of blood in the urine such as polyps, growths and stones. Read more on cystitis and treatment here:
If the bacteria has not been cleared, your dog may require a different antibiotic and for a longer period of time.
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