Were you ever sure you had a UTI, but your doctor tells you that all of your tests are normal? It's possible you had a ureaplasma infection.
Mycoplasma are the smallest living organisms of which 17 species are found in human respiratory and urogenital tracts. Mycoplasma hominis, mycoplasma genitalia, and ureaplasma urealyticum are the genital mycoplasma organisms that are generally regarded as opportunists, i.e. they don't bother most people but can cause problems with impaired immune systems, such as when you're sick and your regular defense mechanisms are down. Mycoplasma hominis and Mycoplasma genitalium have been associated with salpingitis (infection of the tubes) and pelvic inflammatory disease (PID), and both Mycoplasma hominis and ureaplasma can cause infections in pregnant women.
The controversy around ureaplasma is that it is often found in the urinary tracts of healthy adults, so the question is do they really cause disease? Although most people who have ureaplasma don't have any symptoms, ureaplasma can cause urethritis (infection of the urethra or tube through which urine passes). Typical symptoms of urethritis are pain with urination, a general burning sensation, or urethral discharge. Ureaplasma can be passed genital to genital or mouth to genital. Although urethritis due to in men is well-described, there isn't clear evidence that it can cause urethritis in women. Because of this, I have to admit that I am often faced with a dilemma as to whether to keep treating a woman for ureaplasma when she has urethritis symptoms such as urethral pain or burning with urination, and she hasn't improved with treatments that are known to get rid of ureaplasma. Are her symptoms really due to ureaplasma? Or has no one found the real cause of her symptoms, and ureaplasma is a convenient scapegoat since it's normally present in a lot of people anyway?
To add to the confusion, ureaplasma isn't routinely tested for because standard urine cultures don't detect ureaplasma. The most reliable way to make the diagnosis is swabbing the urethra (yep, when your urethra hurts already, your doctor is going to kick you when you're down by putting a little brush in there).
The bottom line is knowledge regarding ureaplasma and the urinary tract is incomplete. Personally if I can't find the reason for a woman's symptoms, I think it's reasonable to treat her for ureaplasma and see if she gets better (although keep in mind many antibiotics commonly used to treat UTIs, or urinary tract infections, will also treat ureaplasma). What I don't support is treating a woman for ureaplasma over and over without any improvement. You know what the definition of insanity is...