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New sensor to detect food-borne bacteria on site


June 15, 2014

Electron micrograph of a flagellated Listeria monocytogenes bacterium, an infectious agent responsible for the food borne illness Listeriosis

Electron micrograph of a flagellated Listeria monocytogenes bacterium, an infectious agent responsible for the food borne illness Listeriosis

According to the CDC, around 48 million people in the US get sick, 128,000 are hospitalized, and 3,000 die as a result of foodborne illnesses every year. One of the main culprits is listeriosis (or listeria), which is responsible for approximately 1,600 illnesses and 260 deaths. Now researchers at the University of Southampton are trialling a device designed to detect the most common cause of listeriosis directly on food preparation surfaces, without the need to send samples away for laboratory testing.

Listeriosos is usually caused by the Listeria monocytogenes bacterium, resulting in symptoms including fever, vomiting and diarrhea. Untreated, illness can spread to other areas of the body and may lead to more severe complications, such as meningitis. Passed on from foods such as milk, cheese, vegetables, fish, and meat, L. monocytogenes is particularly dangerous for those with weakened immune systems, as well as pregnant women, newborn babies, and the elderly.

To develop a device to detect this potentially deadly bacteria, the Biolisme project – a consortium of six partner organizations from four different countries – was formed. Building on research from the University of Southampton, the project developed a sensor capable of gathering and detecting L. monocytogenes directly on food industry surfaces, as both single-cells and biofilms (groups of microorganisms whose cells clump together on surfaces).

The sensor is contained in a device that uses compressed air and water to firstly isolate the cells from the surface being tested, and then move them into contact with a specifically-prepared antibody for detection. If L. monocytogenes is present, the antibody will fluoresce, and this florescence will be detected by a camera specially designed for the device.

"We researched biofilms under different stresses to find the optimum pressure to remove cells from different surfaces, without disrupting the cells themselves," says Doctor Salomé Gião from Southampton’s Center for Biological Science Unit, who has been studying Listeria biofilms under different conditions. "We also found that biofilms can form on surfaces even if they are covered in tap water."

Current bacteria detection techniques rely on laboratory testing, which can take days to return results. And, though traditional laboratory techniques will detect all cell types rather than a specific one like in the Biolisme project, they do not discriminate between harmful live cells and harmless dead cells, thereby possibly returning false readings. The new device is designed to overcome these problems, with the ability to accumulate and detect the pathogen on site within three to four hours.

"The scientific research we have carried out at the University of Southampton has been used by our Biolisme project partners to develop a device which will have major implications for the food industry," said Dr Gião. "By making the process simpler we hope that testing will be conducted more frequently, thereby reducing the chance of infected food having to be recalled or making its way to the consumer."

The sensor prototype stage has been completed in France and on-site trials are currently being performed on the device. Once these are completed, the team plans to move onto demonstrations in food processing plants in the near future.

Source: The University of Southampton

About the Author
Colin Jeffrey Colin discovered technology at an early age, pulling apart clocks, radios, and the family TV. Despite his father's remonstrations that he never put anything back together, Colin went on to become an electronics engineer. Later he decided to get a degree in anthropology, and used that to do all manner of interesting things masquerading as work. Even later he took up sculpting, moved to the coast, and never learned to surf. All articles by Colin Jeffrey
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