Cat not using her litter box

Question
I have 5 cats, ranging in age from 1 year, to 10 years old. One of the cats will urinate on the bathroom rug, instead of the litter box. She only urinates, no bowel movements. The litter boxes [we have 4] are cleaned every 3rd day. We have been treating her for bacteria in her urine, with clavamox[excuse the spelling] for approx. 4 weeks. Our vet thought  it might be a bladder infection. After 4 weeks a urine sample revealed almost no bacteria, but she still urinates on the rug. Any suggestions would be appreciated.

Answer
Hi Mike!  Urinating outside the litter box is the most common symptom of a urinary tract infection, and since your cat has been treated, and her urine is almost bacteria free, this would have to be the scent that is causing her to continue going there.
Cat urine (as you probably know) is very strongly scented.  Even after cleaning a rug, the cat's sensitive sense of smell can still pick up that scent.  If your cat is finding her scent on that rug, she will continue to go there.  Try cleaning the rug with Nature's Miracle Pet Odor and Stain Remover.  I have found this to work the best.  After you are done cleaning the rug with this product, mist just a bit of Lemon Pine Sol over the area.  Cat's despise the scent of lemon and this will deter her from going there.  I really hope this helps!  Please let me know how she does!
Hilary
P.S. You spelled Clavamox perfectly! :-)