cranberry urinary infection kidney

Cranberry has been proven to prevent bacteria from locking on to the cell( or something similar), yet my father's urologist just wrote off cranberry juice as useless. yes it might upset the stomach since it is an acidic juice. But my father was doing fine fighting off infection until he stopped drinking it. Now he has a massive pyelonephritis(infection) that almost killed him; he is still fighting it. Also, I have strong reason to believe that the treatment the doctor gave him caused him an arrythmia(heart problem). I taught him how to eat healthier( fiber, fruits and vegetables) and he was doing fine(and he is 84).
The other doctor he has prescribed him a medication he was allergic to. Why cannot they test the medication on the skin before administering, and see if there is a reaction.
Why don't doctors test medication in each patient before the fact; remember, human beings?not just cash cows?Oh I know, if all else fails, they carry insurance, so why bother.