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Clostridium difficile: the age of the superbug

Dr Matt Doyle gives a round-up of the latest thinking on another key nMRCGP subject

Dr Matt Doyle gives a round-up of the latest thinking on another key nMRCGP subject

What is it?

Clostridium difficile (a gram-positive anaerobic spore-forming rod) is now the most common hospital acquired infection. In 2004 it was reportedly responsible for more than 40,000 UK hospital-acquired infections. It is found in the gut of up to 3 per cent of healthy adults and more than 60 per cent of infants.

C. difficile has a far higher incidence than MRSA bacteraemia. The Health Protection Agency published data in January 2007 on rates of both infections. Between April and September 2006 they reported 3,391 episodes of MRSA bacteraemia and 27,348 cases of C. difficile infection.Several studies since the 1980s have shown that C. difficile is found in around 5 per cent of positive stool cultures taken in primary care for diarrhoeal illness, making it the most commonly isolated diarrhoeal pathogen in general practice.

Survival

C. difficile was first isolated in the 1930s. In 1978 it was recognised as an important cause of antibiotic-induced diarrhoea and colitis. The bacterium produces resilient spores which can be passed between patients by poor hygiene and hand-washing. These spores have been reported as surviving on metal work surfaces for more than four weeks. C. difficile produces two toxins, A and B, which cause the diarrhoeal illness.

In 2006, strain 630 of C. difficile was isolated, sequenced and analysed. Only about 40 per cent of the genes were shared between different strains of C. difficile; worse still, 10 per cent appeared to be mobile elements in a state of flux, allowing it to develop antibiotic resistance easily.

Clinical

Infection often follows broad spectrum antibiotic treatment. Some 80 per cent of cases are seen in the over-65s.

The clinical picture can vary from a mild diarrhoeal illness to pseudomembranous colitis. This gives a severe illness of diarrhoea, fever and abdominal pain following a recent course of broad-spectrum antibiotics. Sigmoidoscopy or colonoscopy often reveal pale 'pseudomembranes' on the gut wall, though now the diagnosis is usually made by testing the stool for C. difficile toxins.Treatment is by oral vancomycin or metronidazole. Some evidence points to 'probiotic' or 'friendly bacteria' approaches to treatment.

Antibiotics and PPIs

The use of broad-spectrum antibiotics is accepted as an important aetiological factor in C. difficile infection, with current Department of Health recommendations suggesting 'prudent' prescribing to help reduce the number of cases.

Other drugs commonly used in general practice are also implicated. An article from 2005 showed that not only is the number of cases isolated in primary care increasing (1 case per 100,000 in 1994 versus 22 cases per 100,000 in 2004, General Practice Research Database) but that there are significantly higher rates in patients taking PPIs, H2 receptor antagonists and NSAIDs. A Bandolier article published in the same year suggested that cutting PPI use could help reduce the incidence of C. difficile.

Stoke Mandeville

In 2006 the Healthcare Commission carried out an investigation into two outbreaks of C. difficile at Stoke Mandeville in Buckinghamshire between 2003 and 2005. During this time 334 people developed the illness and 33 died. The investigators blamed several factors at the hospital such as lack of hand-washing facilities, poor infection control and failure to isolate patients effectively as contributing to the outbreaks.

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