Limiting antibiotics may slow down hospital ‘superbug’

"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," says David Eyre. (Credit: jason carlin/Flickr)

Better use of antibiotics could be critical for reducing the number of hospital cases of Clostridium difficile (C. diff).

The infection causes severe diarrhea, cramps, and sometimes life-threatening complications. Current thinking is that the infection is transmitted within hospitals from other patients with C. diff.

Researchers mapped all cases of C. diff in Oxfordshire over a three-year period (2008 to 2011). They found that less than one in five cases of the so called “hospital superbug” were likely to have been caught from other hospital cases of C. diff, where the focus of infection control measures has been.

Researchers also found the total number of cases of C. diff, whether acquired from other sick patients in hospitals or acquired from elsewhere, fell over the three-year period.

Other factors at work

As a result, the research suggested stringent infection control measures in hospitals were not the most significant factor in curbing the infection.

“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,” says Professor Mark Wilcox, of the University of Leeds and a member of the study team.

“New measures are needed to prevent this bug spreading and being provoked to cause infection.”

The New England Journal of Medicine reported the findings.

“We must be clear, good infection control measures have helped minimize transmission rates in hospitals,” says Tim Peto, study author and professor of infectious diseases at the University of Oxford. “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.”

Peto says that during an overlapping period to the study, the use of antibiotics fell across 175 English hospitals. “C. diff is resistant to antibiotics and that is the key,” he adds.

Infection control vs. antibiotic restriction

“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,” says David Eyre, co-author of the study. “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.”

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 if that transmission was likely to have happened as a result of hospital or patient contact.

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

“Additionally, 45 percent of all cases were so different that they could not have come from another sick C. diff patient in Oxfordshire,” says Peto. “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.”

The National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, the Wellcome Trust, and the Medical Research Council funded the work.

Source: University of Leeds