Science-- there's something for everyone

Monday, April 30, 2012

Just when you thought it was safe to drink your own urine

Contrary to popular mythology, urine is not necessarily sterile. Because many of the bacterial species found in the human bladder cannot be grown in the lab, they’ve long gone unidentified. However, new sequencing techniques allow researchers to catalog bacteria without the necessity of first cultivating them. In this way, Linda Brubaker from Loyola University Chicago and her colleagues from that school, Indiana University and the University of North Texas have been able to find bacteria growing in the bladders of even asymptomatic women.

In the past, if you wanted to get a DNA sequence you’d need to get your hands on a large quantity of that DNA. If you were interested in a microbe, this meant growing a vial full of the little buggers. Nowadays, this is no longer necessary. Not only do tiny amounts of DNA suffice, but you don’t even need to separate out the DNA by species prior to sequencing. Thus, the researchers were able to throw all the DNA they collected into one bag and pull out any bacterial sequences that happened to be in there.

Women who were already scheduled for surgery were asked to give their urine for science. They provided a ‘clean-catch’ (the pee-in-a-cup method of urine collection) before surgery. While they were anesthetized, urine was also obtained both by catheter and by syringe directly out of the bladder.

Bacteria were found using all three urine collection methods, even in women with no symptoms of urinary tract infection. In only two out of twenty-three women did syringe aspiration of urine directly from the bladder not yield bacteria.

The numbers and types of bacteria did differ between the different collection methods, indicating that contamination is occurring during so called ‘clean-catch’. However, there are clearly bacteria residing in the bladders of most women. Whether those bacteria are long-time residents or occasional squatters has yet to be seen. One thing’s for sure though: urine is not as sterile as we thought it was.