The risk of colon cancer increases with exposure to salmonella

A Salmonella infection is a common bacterial disease that affects the intestinal tract

Are people more frequently exposed to non-typhoidal Salmonella at increased risk of colon cancer? Researchers from the Leiden University Medical Center (LUMC) and the University of Illinois have jointly conducted a study to find an answer to this question. Preliminary study results suggest that non-typhoidal Salmonella may increase the risk of colon cancer by contributing to one step in the multistep carcinogenesis process.

The researchers’ results have been published in Cell Reports Medicine.

A Salmonella infection is a common bacterial disease that affects the intestinal tract. Humans are commonly exposed to non-typhoidal Salmonella primarily through livestock and through consumption of foods derived from it, such as eggs and meat.

Typhoid Salmonella – which causes typhoid – infects 10-20 million people annually and leads to approximately 130,000 deaths worldwide. Non-typhoidal infections with Salmonella are more common and less fatal, but lead to an estimated 153 million cases of diarrhea and vomiting and 57,000 deaths worldwide each year.

Salmonella and the development of cancer
The typhoid Salmonella infection has previously been linked to gallbladder cancer. This is because the bacteria enable one step in the cancer-forming process into several steps. Epidemiological studies have also linked severe non-typhoidal Salmonella infections with an increased risk of developing colon cancer.

“A non-typhoidal Salmonella infection is often not noticed by ourselves, but this infection is recognized by our immune system! Our study investigated whether these mild and undetected non-typhoidal Salmonella infections increase the risk of colon cancer. The idea behind this is that with repeated mild bacterial infections, there is a greater chance that a bacterium will invade and manipulate cells that have already taken several steps in the development of cancer due to a previous infection, says Virginie Stévenin, postdoctoral researcher in Neefjes’ laboratory.

Research results
To find out whether there is an increased risk of colon cancer after exposure to non-typhoidal Salmonella, the researchers measured antibody levels against non-typhoidal Salmonella in more than 100 human blood samples to determine the percentage of undetected infections. The researchers discovered that people who had developed colon cancer were also more often exposed to mild Salmonella infections. Salmonella could also be detected in intestinal tumors of mice after infection.

“We also found that several mild infections increased the growth rate of these intestinal tumors. In addition, in a cell culture model, Salmonella was found to more rapidly infect cells with the potential to become fully transformed cancer cells, further promoting cancer formation.” said LUMC Professor Jacques (Sjaak) Neefjes.

Truly a risk factor
Jun Sun, professor at the University of Illinois Chicago concludes: “These experiments suggest that non-typhoidal Salmonella infections may increase the risk of colon cancer by affecting a step in the cancer formation process with several steps. It is difficult to completely avoid such infections. , as no typhoid Salmonella is common in livestock and our food, but exposure to the bacteria can be reduced by good hygiene practices in food handling and preparation.”

Read the original article in Cell Reports Medicine.

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