Rapid food poisoning analysis

Mouldy food can cause health problems

Scientists have developed a gadget that can determine very rapidly whether food is harbouring poisonous bugs.

At first the device, called ImmunoFlow, will be used by food-processing companies.

But its inventors plan that it will eventually be used by health inspectors to mete out on-the-spot justice to caterers who fail to meet acceptable hygiene standards.

Ultimately, a version may be made available for use in the home to test food that has been in the fridge for a few days.

At present it can take several days before analysis reveals whether food samples are contaminated with bacteria that can cause ill health.

New Scientist magazine reports that ImmunoFlow should do the job in 15 to 30 minutes.

The inventor Dr Bart Weimer, a microbiologist at Utah State University, believes that those saved hours could be critical when investigating an outbreak.

Better sensitivity

He said: "We can now detect bacteria more easily and with better sensitivity than existing commercial tests."

ImmunoFlow is so sensitive it can detect Salmonella, Listeria and E. coli O157 - even when there are only 100 cells per millilitre.

At the moment, when food inspectors investigate a report of tainted food, they place the offending morsel in a sterile container and take it to a lab for analysis.

It takes at least 24 hours for any bugs in the sample to grow on a plate. Sometimes it is seven days before they get an answer.

With the new device, investigators simply pour a smidgen of the suspect food or drink directly into the ImmunoFlow's testing chamber.

Solid food has to be pulverised first with a bit of water or buffer solution. A battery-operated pump pushes the sample into the testing chamber.

Inside the chamber are hundreds of glass beads, each coated with millions of antibodies that stick to the kind of bacteria you are testing for, say Salmonella.

Dr Weimer said that previous antibody-based tests lacked the sensitivity of ImmunoFlow because they relied on the bacteria diffusing through a paper membrane covered with antibodies.

But bacteria are big and bulky, so they diffuse slowly and incompletely, which makes the tests less sensitive.

The pump in the ImmunoFlow forces the liquid through the beads so the beads do not get clogged.

Glow

The investigator then adds another set of antibodies labelled with a luminescent marker that will bind to any antibody-bacterium complexes trapped in the chamber, giving off a telltale glow.

At present the ImmunoFlow has to be plugged into a machine called a photon counter, which can be as big as a PC.

However, Dr Weimer's company, Biomatrix Solutions, plans to make a smaller, portable version.

Caroline Smith de Waal, of the Center for Science in the Public Interest, a nutrition and food safety advocacy group, said: "A rapid test such as this could decrease the number of illnesses and deaths due to food-borne bacteria.

"We need to monitor food much more regularly than is being done today."

A spokesperson for the Public Health Laboratory Services said: "If a test could be developed that would reliably detect the presence of harmful bacteria at very low levels at the site of food production or service it would be very useful in the prevention of food poisoning and thus protecting the health of the consumer."