A scientist has developed a machine which can, he says, detect the presence of E.coli in seawater in less than an hour.

Many current tests take days to complete and require samples to sent away to laboratories.

It could speed the closure of danger beaches - and their reopening once the danger has passed.

Millions of Britons are heading for the beach this summer, but hundreds of millions of gallons of raw or partially-treated sewage are discharged around the UK coastline every day.

These may harbour a variety of potentially harmful bugs.

Researchers from the Michigan School of Public Health have developed a portable testing kit.

It can yield a result in less than 45 minutes.

Magnetic field

The test works by a principle called "immunomagnetic separation".

This uses tiny beads coated with antibodies - which are designed to lock onto E.coli bacteria as they pass by.

The beads with bacteria attached can then be extracted with a magnet, and mixed into clean water.

A chemical process allows the bacteria to be broken open, to release a substance called adenosine triphosphate (ATP).

A marker chemical is then added which fluoresces when it meets ATP.

The amount of light, easily measured with a handheld luminometer, equals the concentration of E.coli bacteria.

The testing device costs about $5,000 to buy and each test approximately $5.