No, Urine Is Not Sterile

Urine is composed of urea , water, sodium, potassium, and other chemical compounds. For a long time, people who watched too many survival shows and even doctors believed that urine was germ-free. As it turns out, urine is not sterile when it leaves your body.

In a study published in the Journal of Clinical Microbiology , researchers collected urine samples from both healthy women and women with overactive bladders . They confirmed the presence of live bacteria in the bladder and urine of even healthy women. Previously, if bacteria were found in a patient sample, doctors would view it as a kind of urinary tract infection (although the cutoff point for a positive test was over 100,000 CFUs per milliliter of urine). This is n’t the first time researchers have disproved the very notion of germ-free urine .

The sterile urine myth arose from the idea that, with routine laboratory testing methods, urine samples from healthy people do not produce enough bacterial colonies to be “clinically significant.” The bacteria present were thought to have originated from contact with skin or other non-sterile surfaces – hence the aforementioned cut-off point.

In a follow-up study presented to the American Society of Microbiology, the same researchers took urine samples from 84 women and incubated them under both more favorable conditions and standard laboratory procedures. According to the results, more than 70 percent of the samples contained bacteria, whereas in the standard testing procedure 90 percent of these bacteria were previously registered as “not growing”, which indicates its limitations.

These results also showed that the bacteria that inhabit the bladder in women with an overactive bladder are different and more diverse from those in healthy women. Scientists have hypothesized that bacteria behave in the same way as bacteria found in the intestines , and that changes in the “normal” flora balance may be the cause of overactive bladder symptoms. This is changing the way medical professionals and scientists approach research on the prevention and treatment of bladder conditions such as UTIs and urinary incontinence, one of the researchers wrote in an article in European Urology .

Urine Is Not Sterile: Using Expanded Urine Cultures to Detect Resident Bacterial Flora in the Bladder of an Adult Woman | Journal of Clinical Microbiology


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