By Dilpreet Raju
Medill Reports

Salmonella could pose a much more long-term health risk than just upending weekend plans with food-poisoning symptoms.

According to a study published late last year in in part done by researchers at the University of Illinois Chicago, salmonella infection is considered an environmental risk factor for colon cancer.

Researchers at Leiden University Medical Center in the Netherlands discovered tissue samples that had higher prevalence of salmonella antibodies from colon cancer patients with poorer health outcomes, such as increased tumor size.

“For young people, maybe it’s not a big deal because your body is so strong when you’re young, you can handle a lot of stress from pathogens. The challenge is usually for those past mid-age,” said Jun Sun, UIC lead researcher and professor, who tested strains from Leiden to identify potential impacts.

Yong-guo Zhang, research assistant professor at UIC, said their lab received over half a dozen bacterial strains of salmonella samples obtained by Leiden via routine colon cancer surgeries. Every sample tested had a different manifestation for its host, and the researchers injected mice with the samples.

“They all behaved differently. Some of them would be lethal, killing the mice immediately,” Sun said. “Sometimes minor symptoms would be induced. We use the mice because it’s a controlled system, but naturally, mice are very resistant to salmonella, more than chickens or humans, so we have to treat them with antibiotics.”

Zhang has worked on mouse models at Sun’s lab, which focuses on microbiome interactions in health and disease, for 14 years. By using mouse models, Zhang said, researchers can “see what happens and see if the mechanism of salmonella is of use to the cancer.”

When observing cell cultures, mice infected with salmonella had noticeably quicker cell transformation, proliferation and larger tumors than those of mice not infected with salmonella.

“As you can see, the green is a lot of salmonella cells within the tumor tissue,” Zhang said.

“The challenge for individuals, especially on a daily basis,” comes from understanding when to seek clinical help, Sun said. People who think they have food poisoning often don’t seek medical advice, even if they “may feel sick for several days, especially for Americans with insurance costs here.”

More Americans put off seeking medical treatment due to cost of care in 2022 than the two decades prior, according to an annual Gallup poll.

The study points to a need for more understanding of salmonella’s interactions within the body.

“Our model also shows that salmonella can translocate to other organs, including the brain,” Sun said. “Are either dementia or Alzheimer’s disease related with salmonella infection? We don’t know.”

“It’s an important study and it’s an important opportunity to be able to remind people that we do want to take steps in our day-to-day lives and with the food we eat to help lower risk of foodborne illness,” said Amy Bragagnini, a spokesperson for the National Academy of Nutrition and Dietetics. “How can we better improve our diets to help lower the risk of salmonella?”

Bragagnini, a registered dietician and certified specialist in oncology nutrition, emphasized it is always important for people to practice good hygiene and to be careful of “sneaky” kitchen items such as hand towels.

“Everybody needs to wash their hands. That’s just the biggest step that you can take to really help lower risk of lots of things: the flu, the cold and certainly foodborne illness contaminants, I know that one is kind of obvious,” she said. “But I think you’d be surprised the amount of people that accidentally use the same cutting board, or might just rinse it off, between times that they cut meat and vegetables.

“Dieticians can help people maybe find plant-based protein sources that also, in a roundabout way, might help lower outbreaks of salmonella. In addition, we know from a cancer perspective that people that eat a lot of red meat, anything over 12 to 18 oz. a week, there is an increased risk of colorectal cancer,” Bragagnini said.

For those who still have a hankering for real meat, Bragagnini said it’s important to have a meat thermometer.

“That’s just a really a good way to help, again, lower your risk if you’re cooking the temperature so that salmonella can’t thrive,” she said. “Another good idea is washing your produce, even just scrubbing it off just to make sure” there’s no surface germs from the grocery store.

Published in Cell Reports Medicine, the full paper can be read here.

Dilpreet Raju is a master’s journalism candidate at Medill. You can follow him at @DilpreetRaju on Twitter or reach him at dilpreet@u.northwestern.edu.