E. coli bacteria are an infamous cause of food poisoning, but a new study suggests those same microbes lurking in meat may be behind nearly half a million cases of urinary tract infections (UTIs).
UTIs are very common, affecting more than half of all women at least once in their lives. And the vast majority of those infections are caused by E. coli bacteria.
Although E. coli may be best known for spurring outbreaks of food poisoning, most strains of the bacteria are actually harmless. In fact, E. coli lives happily in the human gut, as part of the vast array of beneficial bacteria that make up the body's "microbiome."
Sometimes, though, when that gut-dwelling E. coli is shed in your stool, it can migrate to your urinary tract and cause a UTI.
That, at least, is the source of most UTIs, said study author Lance Price, a microbiologist and professor at George Washington University, in Washington, D.C.
Price's team found genetic evidence that some UTIs are caused by E. coli in the chicken, turkey and pork that people buy at the grocery store. The bacteria find their way to the urinary tract the same way as other UTI-causing E. coli do — but the source is different.
The researchers estimated that around 8% of UTIs caused by E. coli can be traced to a food source. That would translate to about a half-million such infections among Americans each year, Price noted.
UTIs are especially prevalent among women, who get them up to 30 times more often than men, according to the U.S. Office on Women's Health. Women are vulnerable largely due to anatomy: The opening to the urethra (the tube through which urine flows) is situated close to the anus — making it easier for E. coli to find its way to the urinary tract.
For the most part, UTIs occur in the bladder and cause symptoms like a frequent urge to urinate, burning during urination and lower belly pain. In a small number of cases, UTIs lead to more serious, even life-threatening, infections if they spread to the kidneys or blood.
So, preventing even a small portion of the infections could have a big payoff, Price said.
The study, published online recently in the journal One Health, is not the first to suggest that foodborne E. coli plays a role in UTIs. A 2005 study, for example, concluded that a multistate outbreak of UTIs — which do not normally occur as outbreaks — was likely caused by contaminated food of "animal origin."
The new research took a broader, and more extensive, approach, Price explained.
Over the course of a year, the investigators went out every two weeks to buy samples of all available brands of raw chicken, turkey and pork at the nine major grocery chains in Flagstaff, Ariz. They also collected all E. coli samples isolated from patients at the city's major medical center during the same period.
By analyzing the genomes of E. coli from meat and from patients, the researchers zeroed in on segments of bacterial DNA that are unique to strains that colonize animals that people eat — not people. From there, they developed a mathematical model that predicted the likelihood that E. coli came from a person or from food.
In the end, the model identified 8% of patients as having E. coli infection from meat.
Scaling that to the national level, the researchers estimated that foodborne E. coli could account for around half a million UTIs each year.
A urologist not involved in the study cautioned that the findings do not definitively prove that people in the study contracted UTIs due to undercooked chicken. So, more research is warranted, said Dr. Johanna Figueroa, a urologist at Northwell Health, in New Hyde Park, N.Y.
At the same time, she said, no one would argue against safe cooking and good bathroom hygiene to protect yourself against foodborne E. coli.
Price agreed. That means not only adequately cooking meat, but being vigilant about cross-contamination: Wash your hands after handling raw meat or its packaging, Price said, and keep food preparation surfaces clean.
"I tell people to make the salad, or anything you're going to eat raw, first — before you even take the meat out of the refrigerator," Price added.
As for reducing the risk of recurrent UTIs, the standard advice to women is good bathroom hygiene: Wipe "front to back" to help keep E. coli away from the urinary tract. Drinking enough water is also important, Figueroa said, since that dilutes the urine and lowers the concentration of bacteria.
Neither expert advised people with repeat UTIs to go vegetarian. But Figueroa noted that a nutritious diet (including plenty of fruits and vegetables), adequate sleep, exercise and other healthy habits can help support stronger immune function.
On a larger scale, Price said he hopes the findings can ultimately be used by industry. The research points the finger at specific E. coli strains that may be contributing to UTIs, so it may be possible to limit their presence in the food supply, he noted.
The U.S. Centers for Disease Control and Prevention has advice on preventing E. coli infection.
SOURCES: Lance B. Price, PhD, professor, environmental and occupational health, George Washington University Milken Institute School of Public Health, Washington, D.C.; Johanna Figueroa, MD, urologist, Northwell Health, New Hyde Park, N.Y.; One Health, March 23, 2023, online