Most urinary infections are straightforward. The ones that keep coming back are a different problem.
A simple infection
Bacteria enter the urinary tract and multiply, usually in the bladder. Typical symptoms are burning, urgency, frequency, and cloudy or strong smelling urine. A single uncomplicated infection is usually treated with a short course of antibiotics and that is the end of it.
When it is not simple
Recurrent means two or more infections in six months, or three or more in a year. At that point the goal stops being treating the next infection and starts being working out why they keep happening.
Common reasons include tissue changes after menopause from falling estrogen, incomplete bladder emptying, bacterial persistence and biofilm, constipation and pelvic floor dysfunction, prior antibiotic exposure and resistant organisms.
If your cultures keep coming back negative
The standard urine culture was designed more than seventy five years ago to find a small number of common organisms growing in large numbers. A negative result does not mean your symptoms are imaginary.
PCR and next generation sequencing look for bacterial DNA rather than waiting for organisms to grow, and they routinely find what a standard culture misses.
When to be seen promptly
Fever, flank pain, nausea or vomiting suggest the infection has reached the kidney and should be assessed the same day. Blood in the urine always deserves evaluation, even when an infection explains it.