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Study finds novel method to test food for contamination

By Jane Byrne , 26-Sep-2008

US researchers claim to have developed a new technology to detect illness causing bacteria that could remove the need for product recalls and protect the health of consumers.

The group said their approach, the details of which were published in the journal, Microbial Biotechnology, is more directly related to toxicity assessment than the conventional techniques to test food for bacterial contamination and safety.

According to the researchers, led by Janine Trempy of the Oregon State University, accurate methods for detecting and identifying diverse groups of pathogenic bacteria is essential for diagnosis and treatment of bacterial infections as well as assessing the toxicity potential of bacterial.

Detection evasion

They claim that recent cases of Salmonella contaminated tomatoes, peanut butter and spinach as well as C. botulinum contaminated canned meats indicate the ease by which food-associated bacterial pathogens evade detection, often resulting in massive recalls of popular food items.

According to the researchers, existing tests only work to detect bacteria that have already been characterized, based on a specific sequence of DNA or the type of protein they produce,.

They said that such tests cannot tell whether the contaminating bacteria are alive or dead, they cannot directly assess their toxic potential and sometimes do not detect newly emerging or genetically rearranged strains as bacteria mutate, thus they argue there is a need for detection methods based on parameters different from those describing bacterial presence.

Toxic reaction

Trempy said that bacteria sometimes only exhibit the behaviour that can case illness under specific environmental conditions and it is that toxic reaction the technology detects.

She said the team’s novel approach is based on previous research looking at the colour changes in pigment-bearing cells from Siamese fighting fish.

According to Trempy, studies have found that when Siamese fighting fish encounter certain stressful or threatening environmental conditions, such as exposure to toxic chemicals like mercury, the erythrophores change appearance, and the pigment moves in a characteristic pattern to an internal part of the cell.

She said that the change in pigment location in response to a toxic chemical is rapid, obvious and can be numerically described.

Results

“We discovered that the pigment bearing cells, erythrophores, respond immediately to certain food associated, toxin producing bacteria responsible for making humans sick,” said Trempy. “There is the potential to directly assess the toxic behaviour of the contaminating bacteria, not just the simple presence of the DNA or protein of these bacteria.”

They said that this method can detect such food-associated bacteria as Salmonella and Clostridium perfringens, responsible for diarrhoeal illnesses; Bacillus cereus, responsible for gastrointestinal illness and Clostridium botulinum, which causes toxin-induced botulism.

Trempy said that further studies are needed to define the pigment bearing cell response to other important bacteria of concern, such as E. coli O157:H7 and Listeria

The researchers said their method has been patented.

Trempy said that further work is also required to develop a pigment bearing cell for mass production and commercial use and that the team anticipate that portable kits could result that would enable food processors, distributors and handlers, or even consumers to quickly test food for contaminating bacterial toxicity.

Source: Microbial Biotechnology
Published online ahead of print
Erythrophone cell response to food associated pathogenic bacteria: implications for detection
J.R. Hutchison, S. R. Dukovcic, K. P. Dierksen, C. A. Carlyle, B. A. Caldwell, J E. Trempy

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