A new vaccine against killer superbug C-diff is to be trialled in UK hospitals.

The vaccine, developed by biotech firm Acambis, could be used both to treat severely ill patients and mass-vaccinate pensioners who are most at risk from the bacterium.

C. difficile infection is the leading cause of antibiotic-associated diarrhoea in hospitals. Most C. difficile-associated disease (CDAD) cases involve elderly individuals who become infected in hospitals and long-term care facilities that have become reservoirs of these bacteria.

CDAD occurs in susceptible individuals following antibiotic therapy. A large variety of bacteria live in the colon of every healthy person that is collectively referred as the colonic flora. The colonic flora helps the digestive system to function effectively and apparently prevents colonization by C. difficile.

When antibiotics are administered to treat infection with harmful bacteria, they destroy the normal colonic flora and the patient becomes susceptible to C. difficile infection. Infection results from ingestion of C. difficile organisms present in the environment.

Hospitals and long-term care facilities have become reservoirs of C. difficile infection. Infected patients with diarrhoea release C. difficile organisms which produce microscopic spores that persist in the environment for years. There is currently no effective method to prevent the transmission of C. difficile spores in healthcare facilities. Consequently, C. difficile outbreaks are frequent and can lead to the temporary closure of hospital units.

The symptoms of CDAD vary according to the severity of the infection. Symptoms result from the production by C. difficile of two potent toxins (toxin A and toxin B) that cause inflammation of the colon (colitis). Mild infection is characterised by diarrhoea and abdominal pain while severe infection is associated with fever and dehydration. Pseudomembranous colitis is the most serious form of C. difficile infection and can be life-threatening.