C. diff Colitis (Clostridioides difficile Infection)

What C. diff colitis is

Clostridioides difficile (formerly Clostridium difficile) is a bacterium that forms tough spores. Many people swallow spores without harm, because a healthy mix of gut bacteria stops C. diff from multiplying. When antibiotics disrupt that mix, spores germinate in the colon and the bacteria release toxins A and B. These toxins damage the lining of the colon, causing inflammation (colitis) and watery diarrhea.

In severe cases, yellow-white plaques form on the inflamed lining. This appearance is called pseudomembranous colitis, and C. diff causes almost all cases of it. Some people carry C. diff without symptoms. This is colonization, not infection, and it is not treated.

In the US, C. diff causes nearly half a million infections a year and is one of the most common healthcare-associated infections.

Symptoms

Symptoms usually start during antibiotic treatment or within a few weeks after it, though they can appear up to 3 months later.

Mild to moderate infection:

• watery diarrhea three or more times in 24 hours, often with a distinctive strong smell
• lower abdominal cramping and tenderness
• low-grade fever
• nausea and loss of appetite

Severe infection:

• 10 to 15 watery stools a day
• fever and a fast heart rate
• blood or pus in the stool
• dehydration and reduced kidney function
• a very high white blood cell count on blood tests

Fulminant infection is the most dangerous form. The colon can stop moving (ileus) or swell massively (toxic megacolon), so diarrhea may paradoxically lessen while the belly becomes distended and painful. Low blood pressure, shock and perforation of the bowel can follow.

Causes and risk factors

Antibiotics

Almost any antibiotic can trigger it. The highest-risk ones are clindamycin, fluoroquinolones (such as ciprofloxacin), cephalosporins and broad-spectrum penicillins. Risk is highest during the course and in the month after, and remains raised for about 3 months. Longer courses and multiple antibiotics increase risk.

Other risk factors

• Age 65 or older
• A recent stay in a hospital or nursing home
• A weakened immune system, including chemotherapy and organ transplant
• Inflammatory bowel disease
• Chronic kidney disease
• Long-term stomach acid-reducing drugs (proton pump inhibitors)
• A previous C. diff infection

About a third or more of cases now arise in the community, in people with no recent hospital stay, and some have no recent antibiotic use.

C. diff vs ordinary antibiotic diarrhea

See antibiotic-associated diarrhea for the milder, more common problem.

How C. diff is diagnosed

• Stool test: labs test only unformed (liquid) stool. Methods include PCR for toxin genes and enzyme tests for the toxin itself, often combined. Testing people without diarrhea is not recommended, because carriers will test positive.
• Blood tests: white cell count and creatinine (kidney function) determine severity.
• Imaging: a CT scan if severe disease, megacolon or perforation is suspected.
• Colonoscopy or sigmoidoscopy: rarely needed. It can show pseudomembranes when the diagnosis is unclear.

Treatment

Stop the trigger

If possible, the antibiotic that caused the infection is stopped or switched. Stomach acid-reducing drugs are reviewed.

Antibiotics that treat C. diff

Current US guidelines (IDSA/SHEA and ACG) recommend:

• Fidaxomicin: preferred for a first episode, because it has a lower recurrence rate.
• Oral vancomycin: an effective alternative. Taken by mouth, it stays in the gut where it is needed.
• Metronidazole: now reserved for mild cases when the other drugs are not available.

A standard course lasts 10 days. Diarrhea usually improves within 2 to 3 days.

Severe and fulminant infection

People with fulminant disease are treated in hospital with high-dose oral or tube-fed vancomycin, intravenous metronidazole and sometimes vancomycin given rectally. Surgery to remove part or all of the colon, or a loop ileostomy, can be lifesaving when the colon is perforated or does not respond.

Recurrent C. diff

Recurrence happens in roughly 15% to 25% of people, usually within 8 weeks. Options include fidaxomicin, a long tapered and pulsed course of oral vancomycin, and fecal microbiota transplantation (FMT). FMT restores healthy gut bacteria using screened donor stool. FDA-approved microbiome products, given rectally or as capsules, are now available for people with recurrent infection.

Supportive care

• Drink plenty of fluids. Oral rehydration solutions replace salt and sugar better than water alone.
• Do not take antidiarrheal medicines such as loperamide unless a doctor advises it, because slowing the gut can keep toxins inside.
• Probiotics have mixed evidence and are not a substitute for treatment.

Complications

• dehydration and acute kidney injury
• toxic megacolon and bowel perforation
• sepsis and death, mainly in older and frail people
• repeated recurrences

Preventing spread and recurrence

• Wash hands with soap and water. Alcohol hand sanitizer does not kill C. diff spores.
• Clean toilets, sinks and door handles with a bleach-based (chlorine) cleaner.
• Use a separate bathroom if you can while you have diarrhea.
• Wash soiled laundry on a hot cycle with detergent.
• Take antibiotics only when they are needed, and tell every prescriber you have had C. diff.

Frequently asked questions

Is C. diff contagious?

Yes. C. diff spreads through spores in feces that contaminate hands, toilets and surfaces. The spores can survive for months and are not killed by alcohol gel. Healthy people at home are at low risk, but careful handwashing with soap and water and bleach cleaning reduce spread.

Why does C. diff happen after antibiotics?

Antibiotics kill many of the normal bacteria that live in the colon and keep C. diff from growing. With that competition gone, C. diff spores germinate, multiply and release toxins that inflame the colon. Risk is highest during treatment and in the following month.

How long does C. diff last?

With fidaxomicin or oral vancomycin, diarrhea usually improves within 2 to 3 days and resolves by the end of a 10-day course. Bowel habits can take a few weeks to fully normalize. About 1 in 6 people have a recurrence, usually within 8 weeks.

What does C. diff stool look like?

It is typically watery or very loose, frequent (three or more times a day), and has a strong, distinctive odor. It may be green or yellow tinged. Blood or mucus can appear in more severe colitis. Smell and appearance alone cannot confirm C. diff, so a stool test is needed.

What is pseudomembranous colitis?

It is a severe form of colitis in which yellow-white plaques (pseudomembranes) form on the lining of the colon. C. diff toxins cause almost all cases. It is seen on colonoscopy and signals significant inflammation that needs prompt treatment.

Can C. diff come back?

Yes. Roughly 15% to 25% of people have a recurrence, and the risk rises after each episode. Fidaxomicin lowers recurrence after a first episode. For repeated recurrences, tapered vancomycin and fecal microbiota therapy are very effective.