Clostridioides difficile (C. diff) Infection


Published: 19 April 2022

The bacterium Clostridioides difficile is the most common cause of healthcare-associated infectious diarrhoea (Ragusa et al. 2018) and has the potential to cause life-threatening illness (ACSQHC 2021).

Cases of Clostridioides difficile infection (CDI) are on the rise in Australia, with the most recent available data indicating an increase from 7,836 in 2016 to 8,496 in 2018 (in hospitals) (ACSQHC 2021).

Alarmingly, one in five patients who experience CDI will be re-infected within 21 days of their initial illness (ACSQHC 2021).

There’s one key factor increasing the risk of CDI: misuse and overuse of antimicrobials (ACSQHC 2021).

So, how can this be combatted?

What is Clostridioides difficile?

Clostridioides difficile bacteria

Clostridioides difficile, also known as C. difficile or C. diff, is an anaerobic, gram-positive, spore-forming bacterium (CDC 2021; ACSQHC 2018).

Previously, C. diff was referred to as Clostridium difficile before being reclassified to a new genus in 2016 (The Lancet Infectious Diseases 2019).

C. diff bacteria are able to survive for long periods of time outside of the body by forming spores, allowing them to enter a dormant state that is highly resistant to the environment and easy to transmit (Basta & Annamaraju 2022; Mayo Clinic 2021).

For this reason, dormant C. diff can be found anywhere in the environment, including:

  • In human or animal faeces
  • On surfaces
  • On unwashed hands
  • In soil
  • In water
  • On food.

(Mayo Clinic 2021)

Once ingested, the bacteria reactivate inside the digestive system (Mayo Clinic 2021).

What Causes Clostridioides difficile Infection?

In healthy adults with normal immune function, C. diff does not cause disease (Mada & Alam 2022). In fact, about 5 to 10% of adults and 15 to 70% of neonates are carrying C. diff in their gut at any given time without experiencing symptoms (SA Health 2022; Health.vic 2015).

Clostridioides difficile infection (CDI) occurs when the microbial flora in the large intestine is altered through the use of antibiotics (Mada & Alam 2022). This change allows the C. diff to multiply and produce toxins (NHMRC 2019).

People with symptomatic infection shed large numbers of C. diff in their faeces, causing their skin, bed linen and nearby surfaces to become contaminated by bacteria and spores. The spores, which are highly resistant to cleaning agents, can remain dormant in the environment for weeks or months (SA Health 2022).

These spores can then be picked up by healthcare workers caring for symptomatic patients (typically via the hands), and transmitted to other vulnerable patients (NHMRC 2019).

C. diff is transmitted from one person to another via the faecal-oral route (Mada & Alam 2022).

People are considered non-infectious once they have not experienced diarrhoea for at least 48 hours, however, C. diff spores they shed may remain in the environment and can still be spread (NHMRC 2019).

Risk Factors for Clostridioides difficile Infection

Those at the highest risk of CDI are people receiving prolonged treatment at a healthcare facility, especially if they are sharing bathrooms or toilets with people colonised with C. diff (NHMRC 2019).

Factors that further increase the risk include:

  • Older age
  • Recent or current antibiotic use
  • Undergoing gastrointestinal procedures or surgery
  • Prolonged stays at a healthcare or aged care facility
  • Being immunocompromised (e.g. being in the intensive care unit, undergoing chemotherapy, being an organ transplant recipient)
  • Underlying illness.

(NHMRC 2019; SA Health 2022)

Symptoms of Clostridioides difficile Infection

Clostridioides difficile symptoms diarrhoea patient using toilet paper

Symptoms typically occur two to three days after infection (SA Health 2022).

CDI usually presents as colitis (infection of the colon/large intestine) (Health.vic 2015), with symptoms including:

(SA Health 2022; Mada & Alam 2022; NHMRC 2019)

In severe cases, the patient might develop pseudomembranous colitis - a serious illness where the lining of the gut becomes inflamed, causing the patient to present severely unwell with abdominal distension and pain. If not detected and treated early, pseudomembranous colitis is potentially fatal (SA Health 2022; Health.vic 2015).

Diagnosing Clostridioides difficile Infection

CDI is diagnosed via laboratory testing of stool samples (SA Health 2022).

Treating Clostridioides difficile Infection

In mild cases, first-line treatment includes stopping the use of the antibiotic being taken (if applicable) and prescribing the antibiotic oral metronidazole. The patient can be managed outside of the hospital (Health.vic 2015; McFarlane & Hajkowicz 2013).

The standard dose of metronidazole for an initial case of CDI is 400 mg three times per day for 10 days (McFarlane & Hajkowicz 2013).

In cases of severe or recurrent illness, the patient will typically need to be admitted to hospital and prescribed the antibiotic oral vancomycin (McFarlane & Hajkowicz 2013).

Adequate fluid intake and rehydration solutions (if necessary) are important in preventing dehydration (McFarlane & Hajkowicz 2013).

Relapse of CDI is common (SA Health 2022). The first relapse can be treated in the same way as the initial illness, however, subsequent relapses should not be treated with metronidazole due to the risk of peripheral neuropathy. Instead, the patient may be referred to an infectious disease specialist or gastroenterologist and prescribed a prolonged tapered course of vancomycin (McFarlane & Hajkowicz 2013).

If the patient develops a fulminant infection, which is characterised by hypotension or shock, ileus, or megacolon (enlarged colon), emergency surgery may be considered (Zuckerbraun et al. 2020).

Preventing Clostridioides difficile Infection

The most crucial way to reduce the prevalence of CDI is to avoid the unnecessary use of antibiotics, especially those that commonly precede CDI (SA Health 2022). These include:

  • Cephalosporins (particular second and third generations)
  • Fluoroquinolones
  • Ampicillin and amoxicillin
  • Clindamycin.

(Aberra 2019)

However, keep in mind that all antibiotics can increase vulnerability to CDI, even those used to treat it (metronidazole and vancomycin) (McFarlane & Hajkowicz 2013).

It’s essential that when antibiotics are required, the narrowest-spectrum (targets the smallest range of bacterial types necessary) medicine is used for the shortest period of time possible (Health.vic 2015; APUA 2021).

Clostridioides difficile antibiotic use
The most crucial way to reduce the prevalence of CDI is to avoid the unnecessary use of antibiotics.

In healthcare facilities where a person with CDI is being treated, the following measures should be taken to reduce the risk of spreading C. diff:

(SA Health 2022; NHMRC 2019)


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What is the likelihood of Clostridioides difficile infection relapse occurring within three weeks of the original infection?


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