I'm with Batmom on this. We've had a lot of UTIs here, especially with one dog. The only test that wasn't negative was a sterile-container catch done by a vet asst (ETA: IIRC, the culture was negative). Cysto/UA/culture stuff has invariably been negative, and yet the selected antibiotic has worked. The one exception to this pattern is the most recent incident, which is starting to look more complex--but if it is a UTI, the culture was unhelpful.