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Scientists firm up kits to detect food pathogens
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Stopping the distribution of contaminated foods from the farm to the fork is a ceaseless challenge for the food industry that relies heavily on technology to identify any anomalies.
A constant threat to the food chain, in the US alone foodborne illness annually costs the country $5.79 billion. And as global food production, processing and distribution rises, so grows in parallel demand for food safety research to ensure the food supply remains secure. The food industry needs cost-effective analytical methods that are safe, accurate and minimise waste to develop methods to screen, detect, and confirm multiple chemical residues and harmful bacteria, including their toxins, in foodstuffs.
But in industrialized countries, the percentage of people suffering from foodborne diseases each year has been reported to be up to 30 per cent. And in the US, for example, around 76 million cases of foodborne diseases, resulting in 325,000 hospitalizations and 5,000 deaths, are estimated to occur each year.
Chemist Guoying Chen at the Agricultural Research Services (ARS) in the US, the government science agency, has developed a prototype of a portable, suitcase-sized device to detect contaminants, such as tetracycline antibiotics, in meat, milk, and fish.
The 11.3 kilo prototype was designed for rule-enforcers to take directly to a site for field analysis. According to ARS, the product’s ‘user-friendly custom software’ is already completed and will run in a Microsoft Windows environment.
The filter-based fluorometer uses TRL to detect trace amounts of target chemicals by removing interference from fluorescent background signals given off by other organic substances present in a meat sample.
The system requires 1-5 g of meat from which to extract the antibiotics present and concentrate them into liquid solution, say the researchers, adding that testing can be done on site and results provided on the spot.
“A quick change of filters allows the user to move from one targeted drug to another. The device is capable of analysing key antibiotics in chicken and beef at slaughterhouses, and it could be used to check for contaminants in liquids, such as milk, water, or urine,” report the ARS scientists.
Antibodies are protein molecules that bind to antigens–such as bacteria–and remove them from the body. Researchers can use antibodies to also isolate pathogens or chemicals in food products.
Andrew Gehring, another chemist in the ARS unit in Wyndmoor, Pennsylvania, is working with researcher Shu-I Tu on a procedure to simultaneously detect Escherichia coli and Salmonella in ground beef, ground turkey, alfalfa sprouts, and seeds.
The procedure uses magnetic beads that are coated with pathogen-specific antibodies. The antibodies bind to the bacteria, and the magnetism pulls them out of complex mixtures of food. Once extracted, the bacteria can be more easily detected.
According to ARS, Gehring is also developing a luminescence-based method coupled with an ELISA (enzyme-linked immunosorbent assay) to detect and confirm E. coli O157:H7.
An ELISA is a sensitive laboratory test that uses antibodies and enzymes to detect and measure specific antigens in samples. Gehring’s test can be completed in 8 hours and can detect 1-10 bacteria per gram of ground meat, say the researchers. The US government would ultimately like to be able to detect 1 bacterium in 25 grams of meat, they add.
Sixty-one deaths and 73,000 illnesses — such as bloody diarrhoea and hemorrhagic colitis – are blamed on eating foods contaminated with the pathogen E. coli each year, according to the US Centers for Disease Control and Prevention.
In 1996, an outbreak of Escherichia coli O157:H7 in Japan affected over 6,300 school children and resulted in two deaths. The UN-backed World Health Organisation claims this is the largest outbreak ever recorded for this pathogen.