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Clostridium difficile infection

What is Clostridium difficile?

Clostridium difficile (so called because when it was first discovered it was difficult to grow in the laboratory) is a cause of diarrhoea, which is usually acquired in hospital. Although in most cases it causes a relatively mild illness, occasionally and particularly in elderly patients, it may result in serious illness and even death. The bacterium produces two toxins which are responsible for the diarrhoea and which damage the cells lining the bowel. However, not all strains of C. difficile produce toxin; these strains are unlikely to cause disease and patients colonised by them remain healthy. In addition, the bacterium can form spores which enable it to survive in the environment outside the body and which protect the organism against heat and chemical disinfectants.

What does Clostridium difficile cause?

C. difficile infection is usually acquired in hospital , and almost all patients who develop C. difficile diarrhoea are taking, or have recently been given, antibiotic therapy. Diarrhoea is the most common symptom but abdominal pain and fever may also occur. In the majority of patients, the illness is mild and full recovery is usual, although elderly patients may become seriously ill with dehydration as a consequence of the diarrhoea. Occasionally patients may develop a severe form of the disease called 'pseudomembranous colitis' or 'antibiotic-associated colitis' which is characterised by significant damage to the large bowel. This may lead to a grossly dilated bowel possibly resulting in rupture or perforation. Unlike some other causes of diarrhoea, it is rare for C. difficile to spread to other parts of the body such as the blood stream.

How is the disease diagnosed?

C. difficile infection should be considered in any patient who develops diarrhoea and who is taking an antibiotic, or who has received a course of antibiotics in the past few weeks. In the laboratory the most reliable way of confirming the diagnosis is by the detection of the toxin produced by C. difficile in the faeces of patients. Therefore, one or more faeces specimens should be sent to the microbiology laboratory requesting that a specific investigation for C. difficile is undertaken. Such tests are not routinely performed on all faeces specimens but are recommended for specimens from patients at increased risk of C. difficile infection, such as those on antibiotics and elderly patients in hospital. Usually, once a diagnosis has been confirmed, repeat specimens need not be taken unless there is a relapse following treatment.

Occasionally, usually in very young children or in patients who have recently been treated for C. difficile infection, large amounts of the toxin may be detected in faeces without producing symptoms in the patient. The reason for this is unknown, but it means that routine screening for C. difficile in patients without symptoms is not useful.

Although the bacterium may be grown on special culture medium, its isolation alone does not conclusively prove that the diarrhoea is due to this organism, as strains of C. difficile which do not produce the toxin are unlikely to cause diarrhoea. Direct examination of the bowel by sigmoidoscopy and taking small biopsies for analysis may also help in confirming a diagnosis, especially in suspected pseudomembranous colitis, but these procedures are not always available. X-ray investigations are sometimes helpful.

How is Clostridium difficile treated?

Fortunately, most patients develop only a mild illness and stopping the antibiotics, if clinically possible, together with fluid replacement, either by mouth or intravenous drip, usually results in rapid improvement. Sometimes, however, it is necessary to give specific therapy against C. difficile itself. Two antibiotics are known to be effective in treatment. Metronidazole taken by mouth is often prescribed as the first choice; if this is not effective then another antibiotic, vancomycin, also taken by mouth, can be tried. There is a risk of a relapse of symptoms in about 20-30% of patients and further courses of these antibiotics may be required.

How is the spread of Clostridium difficile controlled?

Patients with diarrhoea, especially if severe or accompanied by incontinence, may unintentionally spread the infection to other patients, and large outbreaks of C. difficile infection have been described in hospitals. In addition, the ability of this bacterium to form spores (which other causes of diarrhoea, such as salmonella cannot do) enables it to survive for long periods in the environment, e.g. on floors and around toilets. Infected patients should be segregated from non-affected patients, preferably in a single room. Disposable gloves and aprons should be worn by staff when caring for infected patients. Rigorous cleaning with warm water and detergent is probably the most effective means of removing spores from the contaminated environment. However, the most efficient control measure in preventing person-to-person spread of this infection is the thorough washing of hands by health care staff before and after patient contact.

What is the risk to health care workers and patient's relatives?

Because most patients with this condition have recently received antibiotics, hospital staff such as nurses and doctors, and patient's relatives are at little risk of catching the illness themselves. However, should these people be receiving antibiotics then they may be at some risk of infection, and therefore they should be especially scrupulous in their hand washing.

How can this infection be prevented?

The sensible use of antibiotics is the key to the prevention and control of C. difficile infection. Where possible, short courses of antibiotics of only three to five days are preferred to longer courses. In addition, narrow-spectrum antibiotics e.g. penicillin, which only kill a small range of bacteria are preferred to broad-spectrum agents which can have an effect on a wide range of bacteria. Both of these features of antibiotic therapy will minimise the alteration of the normal bacterial flora of the bowel which is a key factor in the development of this condition. A short course of a narrow-spectrum antibiotic is particularly advisable when the precise cause of a bacterial infection is known. Finally when a patient is identified as having C. difficile diarrhoea the infection control measures already described will minimise the risk of spread to others.