According to the researchers, conventional food safety testing only indicates the presence of specific bacteria which does not necessarily describe toxicity and the potential to cause harm. The tests, they say, cannot tell whether the contaminating bacteria are alive or dead, cannot directly assess their toxic potential and sometimes do not detect newly emerging or genetically rearranged strains.
“Sometimes bacteria only exhibit the behaviour that can cause illness under specific environmental conditions, and it is that toxic behaviour that we need to detect”, Janine Trempy, professor of microbiology and associate dean of the Oregon State University College of Science said. "Bacteria are common on exposed surfaces as food products", Trempy said. “Simply knowing they are there does not completely tell you, in a direct measurement, about their potential to make you sick."
The new approach is built on the characteristics of certain "chromatophore" or pigment bearing cells, called erythrophores, from the Siamese fighting fish. Research found that when this fish encounters certain stressful or threatening environmental conditions, such as exposure to toxic chemicals or illness-causing bacteria, the erythrophores change appearance, and the pigment moves in a characteristic pattern to an internal part of the cell.
The change in pigment location in response to a toxic chemical is rapid, obvious and can be numerically described. "We discovered that the pigment bearing cells respond immediately to certain food associated, toxin producing bacteria", Trempy said. "There is potential to directly assess the toxic behaviour of the contaminating bacteria, not just the presence of the DNA or protein of these bacteria. And this response can be easily seen under a low-power microscope and quickly quantified, numerically, to describe the intensity of the situation."
The method can detect food-associated bacteria as Salmonella, Clostridium perfringens, Bacillus cereus and Clostridium botulinum. Further studies are needed to define cell response to other important bacteria, such as Escherichia coli O157:H7 and Listeria, Trempy said.
MEDICA.de; Source: Oregon State University