C. diff Testing

C. diff testing checks a sample of your stool (poop) for signs of an infection with a bacteria called C. diff. C. diff is also called C. difficile or Clostridioides difficile. It used to be called Clostridium difficile.

A C. diff infection affects your large intestine. It can cause symptoms that range from mild diarrhea to serious dehydration and colitis (inflammation in your colon, which is the biggest part of your large intestine). In rare cases, a C. diff infection can become life-threatening.

C. diff bacteria are common in the environment, and it's in the stool of people who have the bacteria. If a person with a C. diff infection doesn't wash their hands well after using the bathroom, tiny amounts of contaminated stool can get on anything or anyone that they touch. You can get the bacteria if you touch a contaminated surface and then touch your mouth.

But if you're healthy, you usually won't get sick. Good bacteria in your digestive system will prevent the C. diff from growing out of control and causing an infection. Most C. diff infections happen while you're taking certain antibiotics or within weeks after you finish taking them.

That's because the antibiotics that kill bad bacteria may also get rid of good bacteria in your digestive system that help prevent infections. If your good bacteria are gone, C. diff can grow out of control and make you sick. When C. diff grows, it can release toxins that irritate the lining of your colon and cause symptoms.

Some C. diff tests check your stool sample for these toxins. Other tests check for genes from the types of C. diff that make toxins. Some types of C. diff don't make toxins or cause illness.

There are also tests that look for certain proteins from C. diff bacteria called GDH antigens. GDH antigen tests can show if you have C. diff in your body. But they can't tell if it's making you sick.

To make an accurate diagnosis, your health care provider may order more than one type of C. diff test.

Why this test is done

You may need C. diff testing if you have symptoms of an infection. The main symptoms of a C. diff infection include:

• Watery diarrhea three or more times a day with no other known cause
• Abdominal (belly) pain
• Nausea
• Loss of appetite
• Fever

It is especially important to be tested if you have symptoms and you have a high risk of getting a C. diff infection. Your risk is high if you:

• Have taken antibiotics within the last six to eight weeks.
• Are aged 65 or older.
• Have recently stayed in or worked at a hospital, nursing home, or other health care facility. C. diff bacteria are more common in health care facilities.
• Have a weakened immune system from a health condition such as HIV or certain medicines or treatments, including chemotherapy for cancer.
• Had C. diff in the past. After you recover from a C. diff infection, you may still have the bacteria in your colon. It could begin to grow again and cause a new infection.
• Know you were exposed to C. diff.

How to prepare

You don't need any special preparations for C. diff testing.

Sample type

Stool