Hospitals could be adopting the wrong strategy for combating an infection which affects thousands of vulnerable patients, a study suggests.
Research showed that contact between patients only accounted for a minority of cases involving the bacterium Clostridium difficile (C.diff).
The new findings from a team based at John Radcliffe Hospital in Oxford and colleagues in Leeds contradict previous thinking.
Until now, it has been assumed that C.diff spreads through personal contact with infected patients showing symptoms.
Significant progress has been made in reducing infections in recent years but the results indicate further advances are likely to rely on more sophisticated measures.
Scientists collected samples from almost 15,000 hospital patients and found evidence of C.diff in 4.4 per cent.
Further tests identified 69 strains of the bacterium, but only 23 per cent of these could be linked to known patients with symptoms.
The authors, led by Prof Tim Peto, wrote in the online journal Public Library of Science Medicine: “In this endemic setting with well-implemented infection control measures, up to three-quarters of new (C.diff) infections are not easily explained by conventional assumptions of ward-based transmission from symptomatic patients and so may not be targeted by current interventions.
“A better understanding of other routes of transmission and reservoirs is needed to determine what other types of control interventions are required to reduce the spread of C.difficile.”
Even the cases linked to ward contact represented a “major hospital-acquired infection problem” said the scientists.
But the roughly 75 per cent of unexplained transmissions “raised concern about other acquisition routes” not captured by the study.
Other ways C.diff might be able to spread included transmission by non-symptomatic carriers, including patients’ relatives and staff, or through food or animals.
Microbiologists based at hospitals in Leeds have led the way in carrying out detailed analyses of C.diff infection outbreaks using the latest laboratory “fingerprinting” techniques to find out if cases are linked following the setting up of a national surveillance service.
C.diff rarely causes any problems in healthy people, but may trigger diarrhoea and fever in hospital patients taking antibiotics.
Older people are most likely to be affected. Patients usually recover with treatment but in some cases the infection can be fatal.
Numbers of cases have steadily fallen from a high of 56,000 in 2007-8 to fewer than 22,000 in 2010-11. One outbreak at Maidstone and Tunbridge Wells hospitals in Kent affected 1,100 people leading to the deaths of 90 patients and contributing to the deaths of 345 others.