Poor hygiene and the overuse of invasive devices - tubes inserted into patients to give or remove fluids - are the major causes of the infections, which include septicaemia (blood poisoning) and pneumonia, according to a study. One in ten in-patients at any one time has been infected while in hospital and there is a twentyfold variation in infection rates among hospitals.
Professor Alan Glynn, former director of the Central Public Health Laboratory and chief author of the study funded by the health department, said that hospital staff tended to wash their hands after intimate contact with patients' bodies rather than before. It was the most gravely ill patients who were at greatest risk but studies in the United States suggested that one-third of infections could be prevented with better controls.
"Hospital-acquired infections have been worrying health professionals for many years and are now worrying patients and the public as well. They not only cause increased suffering and more serious illness but infected patients stay longer in hospital, affecting waiting lists and diverting resources which could be better spent elsewhere," Professor Glynn said.
The three-year study conducted in 19 hospitals found that overall, 2.7 patients out of every 100 picked up an infection following admission. Those most at risk were patients with an invasive device inserted - such as a catheter to drain the bladder or a central line to a major blood vessel - who were seven times more likely to get an infection.
The study did not include infections of surgical wounds which the researchers estimate would double the rate, suggesting that more than 100,000 patients a year are infected. In intensive-care units almost one in five patients picks up a bug while in hospital, including those with infected surgical wounds.
Valerie Ward, senior nurse at the Public Health Laboratory Service and one of the study authors, said hospitals had infection control policies but half the staff were ignorant of them. "A lot of policies say when staff should wash their hands but the number of times hands are washed is not as high as it should be," she said.
Infection rates varied more than twentyfold among different hospitals in gynaecology patients who had a catheter inserted to drain the bladder, a common practice after a hysterectomy. Ms Ward said poor hygiene was likely to be "a large part" of the explanation.
Patients who had a device such as a catheter inserted were three times as likely to acquire an infection, yet one hospital catheterised 20 per cent of patients and another 75 per cent. Ms Ward said: "That is an immense difference. Hospitals may need to review their clinical practice in relation to the use of these devices."
Professor Peter Borriello, head of the Central Public Health Laboratory, said that guidelines were useless unless they were enforced. "One of the most important preventive measures you can take is washing your hands. But it has to be policed. People only adhere to it if it is monitored."