Is urine sterile

Urine not sterile after all

Doctors and pharmacists learn in their training: The urine of healthy people is germ-free. If bacteria are found in the urine, this indicates a urinary tract infection. But that does not seem to be the rule, but rather the exception. American researchers working with urologist Linda Brubaker from Loyola University in Chicago also found numerous bacteria in the urine of healthy women. Although these cannot be cultivated with standard methods, they can be detected with a genetic analysis, 16S rRNA sequencing. After the US researchers had indirectly proven the existence of the bacteria, they also succeeded in cultivating them using a special method.

After all, the US researchers found bacteria in 80% of the urine samples examined. In 92% of these positive samples, no bacterial growth was detectable in the standard test; so they would have been wrongly considered germ-free.

The US researchers found a total of 85 types of bacteria in the urine of women, most of them from the same species Lactobacillus (15%), Corynebacterium (14,2%), Streptococcus (11,9%), Actinomyces and Staphylococcus (6.9% each). They also found species of Aerococcus, Gardnerella, Bifidobacterium and Actinobaculum.

A few years ago, the research group succeeded in detecting bacterial genetic material in the urine of healthy women. The new results now show that, contrary to the prevailing doctrine, there is also a kind of physiological bacterial flora in the healthy urinary bladder, which can vary greatly from case to case.

Source: Hilt EE, et al. Urine is not sterile: Use of Enhanced Urine Culture Techniques to Detect Resident Bacterial Flora in the Adult Female Bladder. J Clin Microbiol 2014; 52 (3): 871.