I had problem with reoccurring UTI'S and for me what finally helped was I took a supplement called D-Mannose. I found the brand Source Naturals worked best for me rather than the one from Mercola but I do think a probiotic is helpful. I also had acupuncture for the first few months fairly regularly and now not as often. I also bought a hand held $12.00 bidet which I think was another big help. I can't say for sure which one worked, maybe it was the combination.
D-Mannose is as I understand it, the part of the cranberry that keeps the infection from attaching to the urinary track. I've seen it as an ingredient in some of the dog foods specific for urinary track issues.
http://www.amazon.com/gp/product/B004IW ... UTF8&psc=1
http://products.mercola.com/d-mannose/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2684288/