Clostridium difficile

Clostridium difficile (C. difficile) is a commensal bacterium, found in the gut flora of around 5% of the population. However, particularly after antibiotic therapy, the flora balance favours growth of C. difficile, both endogenous and from infection. Hence infection often follows antibiotic use in patients co-morbid with other conditions, in a hospital setting.

The bacterial spores are particularly long-lasting and are not eradicated by some disinfectants, hence the prevalence in specific hospitals and institutions, perpetuating infectivity.

Release of enterotoxin (toxin A) and cytotoxin (toxin B) lead to a number of C. difficile Associated Diseases (CDAD). These include mild to severe diarrhoea, colitis and sepsis. Infection and mortality is highly weighted to the over 65 age range.

With over 100 strains identified, of particular note has been the emergence of type 027, first isolated in 1999. It has high toxin production and a greater resistance to many antibiotics than others, along with significant growth in incidence.

Antibiotics can be effective, but their main weaknesses are speed of onset of action, and growth of resistance to antibiotics.

A viable strategy is prophylactic protection, in defined circumstances such as:

• On admission to hospitalisation or ahead of scheduled admission.
• Health workers.
• At-risks groups, with increased likelihood of hospital admission, potentially including use as a universal vaccine for the elderly.

Breadth of protection, a strength of HspC technology, is necessary for effective vaccination, including against 027 isolate.