New Biosensor Will Detect Low Levels of Listeria monocytogenes

A team of food scientists have developed a sensor that can detect Listeria monocytogenes in less than 24 hours at concentrations as low as 10³ cells per ml. in pure culture. The sensor also is specific enough to recognize L.monocytogenes only.

"The ability to distinguish this one species from all others makes this a very powerful sensor. No other sensor today can do that," said Arun Bhunia, professor of food microbiology and one of the sensor's developers.

The sensor is made of a small piece of optical fiber - a clear, solid, plastic material that transmits light through its core. The fiber is coated with an antibody, which recognizes and capturesL. monocytogenes, binding it to the fiber. When the fiber is placed in a liquid food solution, any L. monocytogenes in the sample will stick to the fiber.

The presence of L. monocytogenes is verified by the addition of a second antibody, carrying a label that produces a fluorescent glow when exposed to laser light. This antibody attaches to the L. monocytogenes bound to the fiber and signals the pathogen's presence when laser light is passed through the liquid.

The team expects the sensor to be ready for industrial use in another year and hope to be able to optimize the test conditions of the biosensor so a sample can be processed in one working day and be monitored remotely via computer.

Reference: Applied and Environmental Microbiology, October 2004, p. 6138-6146, Vol. 70, No. 10