Originally Posted by
MadGrad
This is actually misleading. Urine IS sterile when it first exits your body. It is, however, also the perfect food for growing bacteria, which means as soon as it sits out for more than a couple minutes it's going to become nasty town really quick.
Urine is a
very inhospitable place for most bacteria. Acidity and toxin levels prohibit successful growth. You are more likely to have infection in just about any other media then you would urine. Don't let the color similarities between LB and urine trick you.
As for the "sitting around," pretty much anything will become unsterile after a period of time, even lytic reagents. There is a reason you have to autoclave things and not just spray them with some lysol.