Clostridioides difficile (C. diff) is a bacterial infection that commonly affects people with ulcerative colitis (UC). It can worsen symptoms and cause complications. It can also trigger a different type of colitis.

UC is a type of inflammatory bowel disease (IBD) that causes chronic inflammation and ulcers on the lining of your large intestine.

People with UC can be at a high risk of developing an infection with a bacterium known as C. diff.

C. diff is an opportunistic pathogen. That means it usually doesn’t infect healthy hosts but can cause an infection in people with weakened immune systems or an imbalance of microbes in their gut, like those with IBD.

While C. diff doesn’t cause UC, it can cause a flare-up. If you have worsening symptoms, like diarrhea and abdominal pain, your doctor might recommend testing for C. diff.

In people without UC, C. diff infections most commonly result from taking certain antibiotics. But people with UC can often get C. diff infections even when they don’t take antibiotics.

Researchers think the infection results from changes in bacteria and other microbes in your gut. Together, these bacteria and microbes are known as the gut microbiome. This imbalance in the gut microbiome allows C. diff to colonize the intestines and grow.

The symptoms of C. diff infection and UC are very similar. It can be difficult for a doctor to tell the difference based on symptoms alone.

Symptoms of UC with C. diff may include:

A C. diff infection can cause a UC flare-up. It can also increase the chance of your UC therapy becoming ineffective, so you may need to change or intensify your treatment plan.

People with UC and C. diff infections can also be more likely to need surgery, like a colectomy.

In some cases, C. diff can result in severe complications, like:

In some cases, the complications can lead to death. According to a 2019 research review, C. diff infections increased the risk of death in people with UC.

Based on symptoms alone, it can be hard to tell the difference between a UC flare and a C. diff infection. Doctors recommend testing for C. diff infection when you experience a flare-up.

A doctor can detect C. diff through a stool test. You’ll provide a stool sample in a sterile container, and they’ll send the sample to a laboratory for analysis.

C. diff is treatable with antibiotics like vancomycin or fidaxomicin.

A doctor may recommend a fecal transplant if you have recurrent C. diff infections. A fecal transplant involves inserting stool from a donor into your gastrointestinal tract. It can help restore a balance to your gut microbiome.

Research shows that fecal transplants are usually safe and effective for treating C. diff infections, but experts need more clinical trials to understand how well they work in people with UC.

While you receive treatment for C. diff infection, your doctor might also change your other UC medications. They may decide to increase or decrease the dosage of immunosuppressive therapy. Your doctor will monitor you for complications or worsening symptoms.

Older adults and people who’ve recently visited an emergency department or experienced hospitalization may have an increased risk of a C. diff infection.

Other risk factors may include:

C. diff infection can spread through contact with the feces of a person with the infection. Washing hands often with soap and water, especially before you eat, can help prevent infection. Regularly disinfecting all commonly touched surfaces can also help.

If you know anyone with diarrhea, use a separate bathroom and avoid close physical contact until they no longer have symptoms.

If possible, avoid any unnecessary use of antibiotics if you have UC.

Many people with UC and mild C. diff infection can make a full recovery but may need to stay in the hospital for several days during treatment.

More severe infections can require more lengthy hospital stays or surgery.

In one 2017 study analyzing data from U.S. hospitals, people with UC and a C. diff infection stayed in the hospital longer and had higher in-hospital death rates than those without infection.

Recurrence rates are also high. According to the Centers for Disease Control and Prevention, about 1 in 6 people with C. diff get a repeat infection within 2–8 weeks. The rates of subsequent recurrences are even higher.

Here are some answers to frequently asked questions about C. diff and UC.

Is C. diff contagious?

Yes, C. diff is contagious and can spread through contact with the feces of someone with an infection. If a person with C. diff infection doesn’t wash their hands after they go to the bathroom, they can spread the bacteria through anything they touch.

Can C. diff infection cause UC?

C. diff infection doesn’t cause UC, but it can worsen flare-ups.

C. diff can cause another type of colitis called pseudomembranous colitis. Also called C. diff colitis, it results in severe inflammation of the lining of the large intestine.

What other infections can you get with UC?

With UC, you may be at a higher risk of several viral and bacterial infections, especially if you take medications that suppress the immune system. Common infections include:

C. diff infection is one of the most common complications in people with UC. If you have UC and experience worsening symptoms, a doctor may recommend testing for C. diff.

C. diff infections can be serious without treatment. Talk with a doctor about your risk of C. diff and what you can do to prevent infection.