Hypervirulent strains of Clostridium difficile.

North America has seen increasing numbers of hospitalised patients and others in nursing homes and the community, with more severe Clostridium difficile associated diarrhoea. This is also described in Northern Europe and surveillance systems are being developed or improved to monitor the situation. One strain (ribotype O27) is described in detail and, like other emerging strains, is demonstrating increasing antimicrobial resistance, notably to quinolone antibiotics. However, its association with increased virulence is not straightforward, probably reflecting the interactions with differing patient case mix. There are many subtypes of the strain and more sophisticated typing and virulence assessment systems need to be developed using isolates carefully collected to test different epidemiological hypotheses. There are also environmental factors relating to treatment such as antimicrobials, cytotoxics and proton pump inhibitors. An emerging theme is the importance of aspects of healthcare delivery in contributing to the problem; this includes poorly maintained and cleaned healthcare premises, overcrowded hospitals and increased staffing workloads leading to poor compliance with infection control.