Restricting antibiotics could be key to fighting 'hospital superbug'

The team from Oxford University Hospitals NHS Trust and the University of Oxford led a unique study to map all cases of Clostridium difficile (C.diff) in Oxfordshire over a three-year period from 2008 to 2011. They used whole genome sequencing to read each bacteria's entire genetic code.

The study involving researchers from Oxford and Leeds found that fewer than one in five cases of the so-called 'hospital superbug' were likely to have been acquired from other hospital cases, where the focus of infection control measures has been.

The researchers also found the total number of C.diff cases fell over the period. This suggests hospital infection control was not the most significant factor in curbing the infection.

Professor Tim Peto of the OUH NHS Trust and the Nuffield Department of Clinical Medicine at Oxford University said: 'We must be clear: good infection control measures have helped minimise transmission rates in hospitals. However, what our study has shown is the vast majority of cases were not caught from other hospital cases and the total number of cases has fallen. So other factors, in addition to hospital infection control, must be at work.'

Professor Peto points to the fact that the use of antibiotics fell across 175 English hospitals during a period that overlapped with this study. He said: 'C.diff is resistant to antibiotics and that is the key.'

Dr David Eyre of the Nuffield Department of Clinical Medicine at Oxford University agrees. He said: 'People usually become ill with C.diff after taking antibiotics, because antibiotics don’t just kill "bad" bugs but also "good" bugs in the gut, allowing the resistant C.diff to take over. One explanation for all types of C.diff going down is that using antibiotics more carefully can prevent people becoming ill with C.diff even if they are exposed to it.

'Our study indicates that restricting the use of antibiotics may be more effective in reducing the number people who fall ill with C.diff than lowering transmission rates through infection control measures.'

Professor Mark Wilcox of the University of Leeds and Leeds Teaching Hospitals leads on C.diff infection for Public Health England and was a member of the study team. He said: 'This is a landmark study in understanding how patients with C.diff are linked. The results have an important message for infection teams. Continuing on the same path to controlling C.diff will not ensure that all preventable cases are avoided. New measures are needed to prevent this bug spreading and being provoked to cause infection.'

The study was supported by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, the Wellcome Trust and the Medical Research Council, and is published in the New England Journal of Medicine.

C.diff causes severe diarrhoea, cramps and sometimes life-threatening complications, and has traditionally been thought to be transmitted within hospitals from other sick C.diff patients.

By assessing the genetic variation between C.diff cases, the team identified those cases that were matched and were likely to be linked. By adding hospital records and the community movements of each case, they worked out whether transmission was likely to have happened as a result of hospital or patient contact.

They found that 35% of cases were so genetically similar that they were likely to be caused by direct transmission. Of that group, just over half (55%) could be linked by hospital contact. In total, only 19% of all cases could be clearly linked to hospital transmission from other sick patients with C.diff.

Professor Peto said: 'Additionally, 45% of all cases were so different that they could not have come from another sick C.diff patient in Oxfordshire. These results suggest that there is a large, unknown reservoir of C.diff bugs that can cause infection and more work needs to be done to identify these sources.'