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This Common Infection Could Raise Your Risk for Colon Cancer

March 21, 2023 -- Researchers are homing in on a new connection between colon cancer and the infectious bacteria known as Clostridioides difficile, or C. diff.

C. diff is a bacterium that infects your large intestine, causing difficult GI symptoms like frequent diarrheaC. diff is a widespread infection among patients who have  been hospitalized, estimated at almost a half million cases per year. It's extremely contagious. 

C. diff has been known to lead to dangerous problems like sepsis if left untreated. Previous research has found that there is a higher amount of C. diff in cancerous lesions than in healthy body tissue. But a recent study from Johns Hopkins and Vanderbilt University has expanded upon the link between C. diff and colon cancer.  This study found that C. diff bacteria may change normal cells to cancer cells. 

The researchers found that many patients with colon cancer have “biofilms” -- or dense amounts of bacteria -- on the surface of their colons. Looking at what type of bacteria made up the biofilms that cause an increase in colorectal tumors, the researchers found that C. diff was capable of producing these tumors in a “cascade.”  

“Big picture, we’re working to learn what the exact mechanism for this is,” says Julia L. Drewes, PhD, assistant professor of medicine at Johns Hopkins University School of Medicine in Baltimore, MD, and a co-author of the study.

What Are the Symptoms of C. diff?

The the following symptoms may mean that you have C. diff

  • Watery diarrhea, from one to as many as 15 times a day
  • Stomach cramps
  • Nausea
  • Fever
  • Loss of appetite 
  • A swollen abdomen

In severe cases, C. diff may cause:

  • Blood or pus in your stool
  • Weight loss
  • Rapid heartbeat
  • Low white blood cell count
  • Dehydration
  • Kidney failure 

C. diff can also cause enlargement of the colon, and sepsis can occur if the infection damages tissues in the body.

Who's at Risk for C. diff?

Anyone can get C. diff, but certain people are more susceptible.  

“People who are over 65, have weakened immune systems, live in nursing homes, or work in health care settings are most at risk for C. diff,” says Lilian Chen, MD, a colon and rectal surgeon at Tufts Medical Center in Boston, MA,  and assistant professor of surgery at Tufts University School of Medicine. “People with C. diff can also get it again; 1 in 6 patients will end up with recurrent infections.”

Another risk factor: taking antibiotics. “Trillions of microbes are normally found in and on our body, including both good and bad bacteria,” says Caroline Um, PhD, MPH, principal scientist in epidemiology research for the American Cancer Society.  “Normally, good bacteria help us fight against bad bacteria such as C. diff. However, you may have a greater chance of C. diff infection after taking antibiotics, since they usually wipe out both good and bad bacteria in our gut.”

C. diff is transmitted through stool, often if someone doesn’t wash their hands after using the bathroom.  If you touch that person’s skin or a surface that person touched, your body can be “colonized” with the bacteria. 

“Once someone is colonized with C. diff, you find it everywhere in their environment – in fact, C. diff is all around all of us,” says Aasma Shaukat, MD, MPH, a gastroenterologist at the NYU Langone Medical Center in New York City and director of GI outcomes research at the NYU Grossman School of Medicine.

But you may show no symptoms.

“In a healthy person, this kind of exposure doesn’t matter because C. diff will not make them sick,” Shaukat continues. “It’s when someone has a compromised immune system that C. diff becomes a concern.” 

How Might C. diff Lead to Colon Cancer?

C. diff may kickstart the process of how cancer begins to form -- through inflammation.

“There are two types of toxins present in C. diff: toxin A and toxin B,” says Drewes. “We need to do more work in order to determine an exact mechanism, but toxin B, or TcdB, which is found in a majority of C. diff infections, appears to drive inflammation in the body.  This inflammation contributes to cell damage in the colon, which may then be connected to a mutation that can cause cancer.” 

This doesn’t mean that every patient who has C. diff will get diagnosed with colon cancer.  

“Cancer is just bad luck– starting with one cell,” says Drewes. But the findings could help researchers understand why so many people under the age of 50 are now being diagnosed with colon cancer. 

How Can I Protect Myself From Getting C. diff?

C. diff can be difficult to eradicate,” says Shaukat. “Hand sanitizer does not kill C. diff. Handwashing with soap and water does, however. Cleaning surfaces with diluted bleach can kill C. diff spores, and in the hospital, UV light is used to kill the spores as well.”

You can get a stool sample test from your doctor to see if you have C. diff.  If you do, treatment will consist of a 10-day course of medication. If you’re on antibiotics, your doctor may actually switch you to a new antibiotic that targets C. diff, like fidaxomicin, metronidazole, or vancomycin.

If I’ve Had C. diff, Do I Need to Be Screened for Colon Cancer? 

“We need a better understanding of the potential role of C. diff in colorectal cancer before we can determine whether this changes current colorectal cancer screening guidelines,” says Um. “However, it’s a good idea to talk with your health care professional about colorectal cancer screening, regardless of whether you have had C. diff. Various factors like smoking, poor diet, being overweight, or having a family history of colorectal cancer can affect an individual’s risk.” 

The bottom line: it’s important to do everything you can to reduce your odds of colon cancer.

“Even though more research is needed, and we can’t fully make the connection between C. diff and colorectal cancer yet, you should feel free to ask your doctor questions about your specific risk if you’ve had C. diff,” says Drewes.  

The more information you have, the better health decisions you can make.

Show Sources


Caroline Um, PhD, MPH, principal scientist in epidemiology research, American Cancer Society.

Julia L. Drewes, PhD, assistant professor of medicine, Johns Hopkins University School of Medicine, Baltimore. 

Lillian Chen, MD, colon and rectal surgeon, Tufts Medical Center, Boston; assistant professor of surgery, Tufts University School of Medicine.

Aasma Shaukat, MD, MPH,  gastroenterologist, NYU Langone Medical Center, New York City; director of GI outcomes research, NYU Grossman School of Medicine. 

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