There are plenty of reasons to cook your chicken thoroughly before eating it, including avoiding a nasty stomach bug. But a new study published Tuesday in mBio might offer a new one: It could prevent you getting an urinary tract infection from Escherichia coli bacteria.
UTIs, which can cause frequent urination, pain or burning while urinating, and muscle aches, are a common ailment, especially for women. According to a 2011 report from the Centers for Disease and Prevention, for instance, there were more than 10 million visits to a doctor’s office or hospital in the U.S. in 2007 because of UTI-related symptoms, including 2 million to 3 million visits to an emergency room. Around two-thirds of these cases are caused by E. coli.
A person can get a UTI in lots of different ways. Sometimes, the normally harmless bacteria in the gut can contaminate the urinary tract through our own feces. Other times, sexual intercourse can introduce bacteria from the colon and vagina to the urinary tract. In both scenarios, women are at greater risk because their urethras are shorter than men’s, meaning the bacteria have less distance to travel before reaching the bladder.
Different E. coli strains cause UTIs and the stereotypical stomach bug. But that hasn’t stopped researchers and doctors from worrying that undercooked, contaminated food could spread both kinds of disease. There’s been conflicting evidence, though, as to whether it can. But according to lead author Lance Price, a professor at George Washington University’s Milken Institute School of Public Health, the current study’s findings are entirely unambiguous.
“This is the first study where we can say: ‘People are definitely picking up those infections from poultry,’” Price told Gizmodo. “We have to open up our heads and acknowledge that foodborne infections aren’t just diarrhea and/or vomiting; they can be UTIs, too.”
Price and his team conducted a relatively simple experiment. For an entire year, twice a month, they tested samples of chicken, pork, and turkey bought from every large retail store in Flagstaff, Arizona, sequencing the DNA of E. coli strains they found. At the same time, they collected blood and urine samples from patients who visited Flagstaff’s only major medical center, again mapping out the E. coli strains found in people diagnosed with an UTI.
More than 80 percent of the meat products carried E. coli, as did around 70 percent of human UTI samples. One particular UTI-causing E. coli strain, ST131, was found in both people and meat (almost always in poultry). And genetic analysis revealed that some people carried and were sickened by a specific lineage of ST131 that likely had its beginnings in birds.
This lineage, called ST131-H22, had mobile strands of DNA (known as plasmids) that are only often seen in strains of E. coli that spread among birds, not humans. Human samples of this E. coli strain, carrying these plasmids, were closely related to meat strains with these same plasmids, further implicating the birds as the true origin of infection (as opposed to, for example, factory workers who contaminated the poultry with their own E. coli). When Price’s team looked at the evolutionary history of ST131-H22, they also found evidence these plasmids had existed since the 1940s, with the lineage losing and acquiring them at least six times. If that’s true, we could have been catching UTIs from this particular germ for decades.
That said, ST131-H22 was only present in a sliver of the meat and human samples found to contain E. coli, and not all infections caused visible symptoms. But Price points out there are countless other UTI-causing strains that could be theoretically spread via food. And though the strains in the samples weren’t resistant to antibiotics used to treat UTIs in humans, they did often show resistance to common antibiotics used on farms. The possibility of more farm-spread E. coli is particularly worrying, because these bacteria can and already have given dangerous plasmids to other bacteria, including those that provide resistance to some of our last remaining antibiotics effective against certain infections.
“These strains weren’t super resistant, but I think it underscores the relevance of antibiotic use in animal products,” Price said. “If I was paid by the industry, I might have doubt about that. But I’m not, so I don’t.”
The next step, which Price and his team are already working on, is to nail down just how big the problem could be. They hope to quantify what percentage of UTIs overall come from the food supply, as well as identify the riskiest strains that can cause more serious infections. That might, in the future, allow farmers to vaccinate animals against these specific strains, or at least allow us to keep an eye out for them.
In the meantime, Price said, the findings only reinforce just how important it is to properly prepare and cook store-bought chicken and other meats.
“Me personally, I always choose animals not raised with antibiotics,” he added.