Clostridioides difficile (klos-TRID-e-oi-deez dif-uh-SEEL) is a bacterium that causes an infection of the large intestine (colon). Symptoms can range from diarrhea to life-threatening damage to the colon. The bacterium is often referred to as C. difficile or C. diff.

Illness from C. difficile typically occurs after use of antibiotic medications. It most commonly affects older adults in hospitals or in long-term care facilities. In the United States, about 200,000 people are infected annually with C. difficile in a hospital or care setting. These numbers are lower than in previous years because of improved prevention measures.

People not in care settings or hospitals also can develop C. difficile infection. Some strains of the bacterium in the general population may cause serious infections or are more likely to affect younger people. In the United States, about 170,000 infections occur annually outside of health care settings, and these numbers are increasing.

The bacterium was formerly named Clostridium (klos-TRID-e-um) difficile.

Some people carry C. difficile bacteria in their intestines but never become sick. These individuals are carriers of the bacteria and may spread infections.

Signs and symptoms usually develop within 5 to 10 days after starting a course of antibiotics. However, they may occur as soon as the first day or up to three months later.

Mild to moderate infection

The most common signs and symptoms of mild to moderate C. difficile infection are:

• Watery diarrhea three or more times a day for more than one day
• Mild abdominal cramping and tenderness

Severe infection

People who have a severe C. difficile infection tend to become dehydrated and may need to be hospitalized. C. difficile can cause the colon to become inflamed and sometimes form patches of raw tissue that can bleed or produce pus. Signs and symptoms of severe infection include:

• Watery diarrhea as often as 10 to 15 times a day
• Abdominal cramping and pain, which may be severe
• Rapid heart rate
• Dehydration
• Fever
• Nausea
• Increased white blood cell count
• Kidney failure
• Loss of appetite
• Swollen abdomen
• Weight loss
• Blood or pus in the stool

C. difficile infection that is severe and sudden, an uncommon condition, may also cause intestinal inflammation leading to enlargement of the colon (also called toxic megacolon) and sepsis. Sepsis is a life-threatening condition that occurs when the body's response to an infection damages its own tissues. People who have these conditions are admitted to the intensive care unit.

When to see a doctor

Some people have loose stools during or shortly after antibiotic therapy. This may be caused by C. difficile infection. See your doctor if you have:

• Three or more watery stools a day
• Symptoms lasting more than two days
• A new fever
• Severe abdominal pain or cramping
• Blood in your stool

C. difficile bacteria enter the body through the mouth. They can begin reproducing in the small intestine. When they reach the large intestine (colon), they can release tissue-damaging toxins. These toxins destroy cells, produce patches of inflammatory cells and cellular debris, and cause watery diarrhea.

When the bacteria are outside the colon — virtually anywhere in the environment — they are in a dormant state, or essentially shutdown. This enables them to survive for a long time in any number of places:

• Human or animal feces
• Surfaces in a room
• Unwashed hands
• Soil
• Water
• Food, including meat

When bacteria once again find their way into a person's digestive system, they "wake up" and can begin to produce infection again. The ability of dormant C. difficile to survive outside the body enables the generally easy transmission of the bacterium, particularly in the absence of thorough hand-washing and cleaning.

Although people who have no known risk factors have gotten sick from C. difficile, certain factors increase the risk.

Taking antibiotics or other medications

Your intestines contain about 100 trillion bacterial cells and between 500 to 2,000 different kinds of bacteria, many of which help protect your body from infection. When you take antibiotics to treat an infection, these drugs tend to destroy some of the helpful bacteria in your body in addition to the bacteria causing the infection.

Without enough helpful bacteria to keep it in check, C. difficile can quickly grow out of control. While any antibiotic can be implicated, the antibiotics that most often lead to C. difficile infection include:

• Clindamycin
• Cephalosporins
• Penicillins
• Fluoroquinolones

Proton pump inhibitors, a type of medicine used to reduce stomach acid, also may increase your risk of C. difficile infection.

Staying in a health care facility

The majority of C. difficile infections occur in people who are or who have recently been in a health care setting — including hospitals, nursing homes and long-term care facilities — where germs spread easily, antibiotic use is common and people are especially vulnerable to infection. In hospitals and nursing homes, C. difficile spreads on:

• Hands
• Cart handles
• Bedrails
• Bedside tables
• Toilets and sinks
• Stethoscopes, thermometers or other devices
• Telephones
• Remote controls

Having a serious illness or medical procedure

Certain medical conditions or procedures may make you more susceptible to a C. difficile infection, including:

• Inflammatory bowel disease
• Weakened immune system from a medical condition or treatment (such as chemotherapy)
• Chronic kidney disease
• Gastrointestinal procedure
• Other abdominal surgery

Other risk factors

Older age is a risk factor. In one study, the risk of becoming infected with C. difficile was 10 times greater for people age 65 and older compared with younger people.

Having one C. difficile infection increases your chance of having another one, and the risk continues to increase with each infection.

Women are more likely than men to have C. difficile infection, for reasons that are not clearly understood.

Complications of C. difficile infection include:

• Dehydration. Severe diarrhea can lead to a significant loss of fluids and electrolytes. This makes it difficult for your body to function normally and can cause blood pressure to drop to dangerously low levels.
• Kidney failure. In some cases, dehydration can occur so quickly that kidney function rapidly deteriorates (kidney failure).
• Toxic megacolon. In this rare condition, your colon is unable to expel gas and stool, causing it to become greatly enlarged (megacolon). Left untreated, your colon may rupture. Bacteria from the colon may then enter your abdominal cavity or bloodstream. Toxic megacolon may be fatal and requires emergency surgery.
• A hole in your large intestine (bowel perforation). This rare condition results from extensive damage to the lining of the colon or after toxic megacolon. Bacteria spilling from the colon into your abdominal cavity can lead to a life-threatening infection (peritonitis).
• Death. Rarely, mild to moderate C. difficile infection — but more commonly, serious infection — can quickly progress to fatal disease if not treated promptly.

To help prevent the spread of C. difficile, hospitals and other health care facilities follow strict infection-control guidelines. If you have a friend or family member in a hospital or nursing home, follow recommended practices. Ask questions if you observe caregivers or other people not following guidelines.

Preventive measures include:

• Avoid unnecessary use of antibiotics. Antibiotics are sometimes prescribed for nonbacterial conditions, such as viral illnesses, that aren't helped by these drugs. Take a wait-and-see approach for these illnesses. If you do need an antibiotic, ask your doctor if it's possible to get a prescription for a drug that is taken for a shorter time or is a narrow-spectrum antibiotic. Narrow-spectrum antibiotics target a limited number of bacteria species and are less likely to affect healthy bacteria.
• Hand-washing. Health care workers should practice good hand hygiene before and after treating each person in their care. In the event of a C. difficile outbreak, using soap and warm water is a better choice for hand hygiene, because alcohol-based hand sanitizers don't effectively destroy C. difficile spores. Visitors also should wash their hands with soap and warm water before and after leaving the room or using the bathroom.
• Contact precautions. People who are hospitalized with C. difficile infection have a private room or share a room with someone who has the same illness. Hospital staff and visitors wear disposable gloves and isolation gowns while in the room.
• Thorough cleaning. In any health care setting, all surfaces should be carefully disinfected with a product that contains chlorine bleach. C. difficile spores can survive exposure to routine cleaning products that don't contain bleach.

A diagnosis of C. difficile infection is based on the presence of:

• Diarrhea
• Other signs and symptoms of C. difficile infection
• Presence of C. difficile in a stool sample

People who have regular, formed stools should not be tested for C. difficile infection. Recent use of antibiotics is not required for making a diagnosis of C. difficile infection.

Stool tests

If C. difficile infection is suspected, your doctor will order one or more laboratory tests of a stool sample. These tests identify either the toxins or strains of the bacteria that produce toxins.

Colon examination

In rare instances, to help confirm a diagnosis of C. difficile infection and look for alternative causes of your symptoms, your doctor may examine the inside of your colon. This test (flexible sigmoidoscopy or colonoscopy) involves inserting a flexible tube with a small camera on one end into your colon to look for areas of inflammation or abnormal tissue.

Imaging tests

If your doctor is concerned about possible complications of C. difficile infection, he or she may order an abdominal X-ray or a computerized tomography (CT) scan, which provides images of your colon. The scan can detect the presence of complications such as:

• Thickening of the colon wall
• Enlargement of the bowel
• A hole (perforation) in the lining of your colon.

Treatments are used only if a person has signs or symptoms of infection. People who carry the bacteria — but are not sick — are not treated.

Antibiotics

If C. difficile infection is related to an antibiotic you're taking, your doctor will likely discontinue use of that drug. In many cases, however, an antibiotic treatment is critical for treating another infectious condition. Your doctor may prescribe a different antibiotic that is less likely to contribute to diarrhea related to C. difficile infection.

Antibiotics are the mainstay to treat C. difficile infection. Commonly used antibiotics include:

• Vancomycin (Vancocin HCL, Firvanq)
• Fidaxomicin (Dificid)

Metronidazole (Flagyl) may be used in combination with vancomycin to treat serious C. difficile infection.

Surgery

Surgery to remove the diseased portion of the colon may be necessary in some cases, including:

• Severe pain
• Organ failure
• Toxic megacolon
• Inflammation of the lining of the abdominal wall

Treatment for recurrent infection

Approximately 25% of people treated for C. difficile infection get sick again, either because the initial infection never went away or because they've been reinfected with a different strain of the bacteria. The risk increases with each C. difficile infection episode and exceeds 50% after three or more infections.

Your risk of recurrence is higher if you:

• Are older than 65
• Are taking other antibiotics for a different condition while being treated with antibiotics for C. difficile infection
• Have a severe underlying medical disorder, such as chronic kidney failure, inflammatory bowel disease or chronic liver disease

Treatment for recurrent disease may include the following strategies.

• Antibiotics. Antibiotic therapy for recurrent infections may involve one or more courses of a medication. The drugs are usually different from the type of antibiotic used previously. The effectiveness of antibiotic therapy declines with each subsequent recurrence.
• Antibody-based therapy. A therapy, known as bezlotoxumab (Zinplava), is a human antibody against the C. difficile toxin B and has been shown to reduce the risk of recurrent C. difficile infection in those at a high risk of recurrence.

• Fecal microbiota transplant (FMT). FMT is an emerging treatment for multiple recurrent C. difficile infection that has been studied in clinical trials. The U.S. Food and Drug Administration has not approved FMT but allows the use of FMT for C. difficile infection as an experimental procedure. You need to sign an informed consent about the benefits and risks of the experimental procedure. FMT is also called a stool transplant or an intestinal microbiota transplant.

  FMT restores healthy intestinal bacteria by placing another person's (donor's) stool in your colon with specialized tubes inserted through your rectum. Donors are screened for medical conditions, their blood is tested for infections, and stools are carefully screened for parasites, viruses and other infectious bacteria before being used for FMT.

  Research has shown that FMT done one or more times has a success rate higher than 85% for treating recurrent C. difficile infections.

• Probiotics. Probiotics are supplements or foods that contain microorganisms intended to maintain or improve the "good" bacteria in the body. The role of these products in C. difficile infection is controversial. Research hasn't consistently shown that currently available products are helpful in preventing or treating infection with C. difficile. Advanced probiotics are currently being studied for their potential use in the treatment or prevention of C. difficile infection but aren't currently available.

Supportive treatment for diarrhea includes:

• Plenty of fluids. Choose fluids containing water, salt and sugar, such as diluted fruit juice, soft drinks and broths.
• Good nutrition. If you have watery diarrhea, eat starchy foods, such as potatoes, noodles, rice, wheat and oatmeal. Other good choices are saltine crackers, bananas, soup and boiled vegetables. If you aren't hungry, you may need a liquid diet at first. After your diarrhea clears up, you may have temporary difficulty digesting milk and milk-based products.