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Technology allows faster screening for bacteria on food

By Joe Whitworth , 21-Jan-2013
Last updated the 21-Jan-2013 at 17:35 GMT

Australian researchers have claimed a breakthrough that will allow them to use DNA amplification on “microspheres” to rapidly detect and identify large numbers of different bacteria at once.

Scientists from the University of Queensland (UQ) and the Department of Agriculture, Fisheries and Forestry (DAFF) said the time required for one run is the same as existing methods but the nanobiotechnology will allow more reactions to be done at once, in a single run.

However, the reliability for testing very large panels of pathogens remains to be established, which is part of a new project, said the researchers.

How it works

The process involves colour coded polystyrene Luminex microspheres which are mixed with DNA extracted from the samples.

Up to 100 colour coded miscrospheres are available and each colour corresponds (one-to-one) to a particular target pathogen.

Professor Ross Barnard, director of the Biotechnology Program at the UQ School of Chemistry & Molecular Biosciences, said the techniques could help improve food safety.

A polymerase chain reaction (PCR) is carried out in a mixture, in a PCR reaction tube containing the colour coded beads.  

“A fluorescent signal (green) develops on those beads on which a positive reaction takes place (I.e. the pathogen is present in the sample).

“After the PCR reaction the micropheres are separated in a capillary sorting machine, which uses lasers to detect the colour code on the microspheres, and the green signal on each microsphere can be measured at the same time.

Green signal

Barnard said a stronger green signal on a particular microsphere means more of the corresponding pathogen was present in the starting sample.

He said while testing methods do exist, they had been slow and less effective, so focus had been turned to leveraging existing “microsphere” technology to a new level.

When asked about future developments, he said: Extension to testing multiple pathogens (Campylobacter coli and Camplyobacter jejuni genotypes- of which there are many) and other disease targets.  

“The test could be used for food samples before shipping, or in tracing outbreaks if and when they happened.”

The discovery was the result of five years of research and the full scale of the benefits is yet to be known, he concluded.

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