cat Stella was diagnosed with a UTI early in February. She is a senior cat of unknown age. The vet kept her for over a week treating her as it was a severe infection. I was allowed to finally bring her home with instructions on dosing her for 14 more

My cat Stella was diagnosed with a UTI early in February. She is a senior cat of unknown age. The vet kept her for over a week treating her as it was a severe infection. I was allowed to finally bring her home with instructions on dosing her for 14 more days with liquid Clavamox 1.5ml twice daily x 14 days. I completed the course(Stella was none too happy about it) and brought her in 14 days later for a urinalysis. That test still showed bacteria in her urine. The vet had me bring her in for another urine sample.  This test which would identify the bacteria and which drug would be the best to treat it took 5 more days. When it came back it was the same bacteria suspected in the beginning. The best drug for treatment, Clavamox. This time it was the 62.5 mg pill twice daily for 14 days. (Stella was not happy withthis either) I was told to bring her back in after day 10 on the med to test again. The test results came back that she had cleared the bacteria. I was then told that even though Stella had finished the 14 days required the vet wanted me to continue dosing her profolacticly for another 14 days. I'm afraid that this is possibly over prescribing the antibiotic. When I did ask the vet, she said because of Stella's advanced age, this would insure the UTI would not have a reoccurance.  This seems to me that Stella  might develop an immunity to any efficacy the drug might have going forward. 

My question is about the medication usage. Is a profolactic use acceptable, especially in Stella's case? Please let me know. As of now I am continuing as directed. 

Thank you for any help you can provide,

Sherrie McGee