Ready, Aim, Fire! Pathogen detection by laser

By Joseph James Whitworth

- Last updated on GMT

Picture: Istock/MihailUlianikov
Picture: Istock/MihailUlianikov
Progress on a reagent free technology to detect foodborne pathogens has been presented during a vendor seminar at an international conference in Prague.

The technology is based on the use of elastic light scatter (ELS). It uses a laser to fire at a colony on an agar plate and the light-scatter that is produced by that gives a pattern.

This is called a fingerprint and from that fingerprint the organism can be identified without damaging the colony and with no reagents. This can be done inside the petri dish without opening the plate.

Once the system has been trained, the user can identify organisms rapidly and reagent free.

Work with Hettich

Hettich Imaging Technology, is commercialising the work, it designs, engineers, and commercializes software and automated incubation systems for identifying pathogens using ELS.

Using standard microbiological practices, results are generated in a non-destructive environment.

The firm is introducing BEAM, a modular platform applying technology to identify various pathogens.

Paul Robinson, professor of biomedical engineering at Purdue University said there will be one and two channel instruments and fully automated systems.

“The first and foremost application was designed for foodborne contamination so for identifying organisms in food and particularly tracking those pathogens. The technology was designed to pick out those pathogens in a mixture of colonies,” ​he told FoodQualityNews at the RAFA Syymposium.

“It has many applications in tracking and tracing organisms in different samples. It could be in sterility testing or in bio-defense.”

Various physical parameters - such as refractive indices, local density of bacteria and individual shape - can influence incoming photons.

Time to result and specificity

Robinson said the time to result depends as the system requires the chosen organism to be cultured on agar on a petri-dish and different organisms grow at different speeds.

“This is one of the advantages of an automated system which can determine when a colony is at a size that it can be differentiated," ​he said. 

“So it can be as low as four to six hours or as long as 48 hours if a colony takes to grow. Then in terms of specificity and accuracy, we are in the 90% sensitivity with no reagents and it is non-destructive.”

The work was funded by the US Department of Agriculture (USDA) with additional support from the National Science Foundation (NSF) and National Institute of Health.

It has developed many different machine sizes including a shoebox instrument which could be carried to a field laboratory where a contamination site is of interest in food production for example.

Once you identify an organism a database can be built and Purdue has done just that.

“Once we identify an organism which is a known organism we culture that onto a plate with maybe 50 colonies, we will then analyse ever one of those colonies," ​said Robinson. 

“This now becomes a classifier for that organism which goes into the database and we will do that for every organism of interest and once we have those organisms of interest in the database then we have a series of classifiers.”

Robinson said cost of operation and no reagents makes the technology stand out.   

“I would say cost of operation and no reagents and it works in standard petri dishes and agars, is fast and has a high level of accuracy. If you are culturing your organisms anyway this is definitely one of the ways to go," ​he said.

“There will be virtually no training at all. As long as you know how to put a plate into a machine everything else is done for you.”

Related topics: Food Safety & Quality

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