Since Nystatin is toxic to our cells and system as well as targeted fungai and beneficial intestinal bacteria, if your MD is advising it, I would think it is time for a Doctor upgrade, or perhaps time to share some up to date research texts with them. (you know that bacteria supplements are severely incapable/inefficient for restoring the appendix organisms after we remove them, so why go that route, unless you arent motivated to find the cause for the immune response insufficiency)
Horsetail aka Shave Grass herb(tea) is one of the best for UTIs.