Okay that information helps.
What concerns me the most about blaming all of these signs on her possible urinary tract infection is that true bacterial infections of the urinary tract in young cats such as she is are not common. While these cats certainly can have urinary discomfort and inflammation, it is not usually caused by bacteria in which case the antibiotics probably are not going to make a big difference in relieving her symptoms. More often these cats are affected by a condition called idiopathic cystitis, or more simply, inflammation of the bladder from an unknown cause. They can be very uncomfortable and could have signs as you describe. There usually is blood in the urine. The only way to definitively rule out this condition from a bacterial infection is with the urine culture, so if one were not performed, it is uncertain whether she needs the antibiotics or if they are helping her. If not, it would be worth investigating other possible causes of urinary discomfort like for instance bladder stones, tumors etc. In addition, if this truly was a case of idiopathic cystitis, it sounds like she needs some pain relief.
It is also possible that the urinary tract is not the problem and her urinary accidents may simply be because she is painful or something else is bothering her. Sometimes cats with colitis or G.I. signs will develop a litter box aversion, because they associate their litter pan with pain, but the same could be true, if she were having pain or discomfort, generating from another source like her hips.
If she is continuing with these symptoms, I would definitely have her re-examined today.
The symptoms you describe and the results of her urine tests do not strongly point to the urinary tract as the cause. While it could be, it still would be a good idea to look for other possible causes, especially since cats are so good at hiding their diseases.
I am linking an article about feline lower urinary tract disease for you to read more about it
Good luck with her and I hope you're able to get the bottom of the soon so that she can get some relief. Please let me know if you have any further questions.
Edited by Dr Z on 2/9/2010 at 4:53 PM EST