Sensitive diagnostic tests now demonstrate that healthy urinary tracts host a ubiquitous, complex microbial community. Recognition of this microbiome, largely undetectable using standard agar-based cultures, offers a new perspective on "UTI." Everyone is bacteriuric. From this perspective, most people who are treated for a "UTI" would probably be better off without treatment.
From "Urinary Tract Infection"—Requiem for a Heavyweight"
https://www.medscape.com/viewarticle/887109 (free registration required)
I often get questions from members about whether or not the new DNA and PCR-type supersensitive tests should be trusted when looking for infection. Whether or not you have an infection is traditionally determined by the
number of organisms they find. If the urine, for example, is teeming with E. coli, then you can safely say there is a UTI. But if you ignore the fact that a patient has no bacteria — or low counts of bacteria — in his fluids, and instead do highly sophisticated searches for the tiniest genetic traces of any bacterium, you will find those traces, in almost all people, including healthy people. You can then proclaim "Infection!", even though there is no infection, only a
presence.
That's why the extended “7 day” culture tests are such a scam, because even one solitary innocent bacterium will breed up into a vast colony in that time, suggesting infection where none exists.
Our bowels, for example, are full of bacteria that can do us great harm (e.g. Clostridium difficile), but they are kept in check by other bacteria. You can find these pathogens in the bowel, but they are not "infections".
The paper cited above makes the point that the urethra, prostate, bladder are part of the skin surface:
The urine-bearing urinary tract extends without interruption from Bowman's capsule [kidney] to the urethral orifice, essentially a part of the body surface. Continuous production of urine presents perineal and ascending microbes with a reliable supply of nutrition. The biological plausibility of a sterile urinary tract is quite low.
As such, we should not expect our urethras, bladders or prostates to be sterile.