Hi, Thanks for writing in. At 25 years,it is too early to suffer from cystitis that is not responding to standard medications and complicating to allow kidney infection. You must drink adequate amounts of water and fluids and not hold urine for long durations. You can get a urine culture and sensitivity test done and then take long duration of course of antibiotics medications which will work for the infection. For the kidney complications, it is better to do kidney function tests like serum creatinine and glomerular filtration rate to know if there is chronic kidney disease and its stage. Taking proper responsive antibiotics for an extended period usually prevents recurrent infection. The infection might be due to regular use of public toilets and please avoid unclean public toilets. Diet is not a concern for your urinary infection.