London

Researchers have developed a test that will speed up the identification of antibiotic-resistant bacteria in hospitals, allowing quicker treatment for patients and curbing the spread of infections.

The test tracks down methicillin-resistant Staphylococcus aureus (MRSA) bacteria by tagging them with luminescent enzymes and measuring the light they give off. It uses technology first developed at the UK Ministry of Defence bioweapons laboratory at Porton Down in Wiltshire to monitor airborne bacteria for bioweapon detection.

“We have cut down the time needed for the diagnosis of MRSA,” says Bill Mullen, chief executive of Acolyte Biomedica, a company based at Porton Down science park that has patented the test. Acolyte Biomedica has a licence agreement that gives it access to the defence lab's work.

Worldwide infections of MRSA have steadily escalated since it was first detected in the 1960s. In Britain, where the problem has caused widespread public alarm, MRSA costs the National Health Service £1 billion (US$1.8 billion) each year, according to the National Audit Office, which audits the accounts of government departments and agencies.

MRSA is usually carried asymptomatically on the skin, but causes infection when it enters wounds or affects weak immune systems. It can be fatal because its resistance to antibiotics makes it difficult to treat.

In the test, samples are taken from patients' nasal fluids and the swabs placed in liquid containing magnetic beads coated in antibodies that stick to the bacteria. These are then removed from the liquid using another magnet.

If MRSA cells are present in the sample, the beads will then be covered in them. To test this, the liquid coating the beads is placed in a dish with the antibiotic methicillin. This kills all other bacteria, leaving only the MRSA to divide and multiply.

After a few hours, the firefly enzyme luciferase, which reacts with adenosine triphosphate (ATP) in living cells to produce light, is added to the mix. The culture will glow if MRSA is present. Another compound, adenosine diphosphate, which amplifies the amount of ATP produced, is also added, increasing the test's sensitivity 100-fold. Other tests for MRSA take days, rather than hours.

Mullen is pleased the military work will help to address a public-health problem. “We are turning swords into ploughshares,” he says. He adds that the test will be tried out in hospitals from May and will be available for general use by early next year.