Urine May Not Be As Sterile As Once Thought
April 10, 2012

Urine May Not Be As Sterile As Once Thought

Researchers have found the presence of bacteria in the bladders of healthy women. While such a finding may seem quite obvious, it does disprove a common theory that urine is a sterile substance. Published in the April issue of Clinical Microbiology, researchers at Loyola University Chicago Stritch School of Medicine (SSOM) studied women with symptoms consistent with urinary tract infections, but were free from actual UTIs.

Linda Brubaker, MD, MS, and dean of SSOM said in a press release, “Doctors have been trained to believe that urine is germ-free. However, these findings challenge this notion, so this research may have positive implications for how we treat patients with urinary tract conditions in the future.”

To conduct the study, the researchers collected urine samples from the women with UTI-like symptoms. These samples were then genetically analyzed to find certain types of bacteria not usually identified by urine culture techniques used to diagnose UTIs.

These urine cultures have often been used to determine UTIs, though some doctors say they are not as effective as the new DNA-based measures.

“While urine cultures have been the gold standard to identify UTIs in the past, they have limited utility,” said Alan Wolfe, PhD, co-author and professor of Microbiology and Immunology, SSOM. “They are not as effective as the DNA-based detection measures used in this study.”

One issue the researchers had to tackle was how to collect the urine samples without being contaminated by other forms of bacteria. The standard method of capturing a urine sample in a cup can be risky, as other forms of bacteria can infect the sample. It was determined the best way to capture a urine specimen was by using a catheter, as it returned the most consistent results.

The Loyola researchers now set out to determine which bacteria found in the bladder are helpful and which are harmful. Additionally, the researchers will begin to determine how these bacteria interact with one another, as well as how they interacts with their host. A larger, international effort is also underway to determine the types of bacteria found in a healthy human body. Together, these research teams hope to correlate their findings to determine changes in the bacterial communities of healthy human bodies and those with diseases.

“Further studies are needed to determine if the bacteria found in the bladders of women in this study are relevant to urinary tract conditions,” Dr. Brubaker said. “If that is the case, these studies could make it possible to identify women who are at-risk for these conditions, which may change how we manage patients.”

According to the Merriam-Webster dictionary, “Sterile” can be defined as “free from living organisms and especially microorganisms.” As bacteria are living organisms, this research disproves the common notion that urine is sterile. It has been widely, yet falsely understood by laypersons that the sterility of urine gave it multiple uses, such as being administered as an antiseptic and as a water replacement. Both of these cases are usually mentioned where survival techniques are being discussed, though the Army field manual directly opposes this.