CANADA – Researchers in Canada have created a colorimetric sensor they claim can “rapidly” identify Salmonella-contaminated food using a nucleic acid probe.

The gadget is an “easy-to-use” colorimetric assay, according to the scientists, that is based on a novel nucleic acid probe that has been cleaved by an RNase enzyme unique to the Salmonella species.

The researchers from McMaster University in Hamilton, Canada, under the direction of Yingfu Li, Tohid Didar, and Carlos Filipe, noted that this particular enzymatic cleavage principle “made it possible to build a sensitive but simple and portable test system using colloidal gold”.

Consuming eggs, ground meat, or chicken that has been contaminated with Salmonella typhimurium can result in life-threatening food illness.

Noting that typically, food contaminated with Salmonella is “usually only confirmed several days later when the bacteria are detected in microbiology laboratories by growing them in culture”, the scientists worked on developing a novel test system based on a hybrid DNA-RNA probe that specifically and rapidly detects salmonella, without the need for microbiological diagnostics or expensive analytical equipment.

Using a multi-round selection procedure, the researchers discovered a synthetic DNA-RNA hybrid probe that serves as a substrate for an RNase H enzyme that is unique to the salmonella species.

Based on these results, the team created a fluorescence-based assay for salmonella RNase H initially, then extended the idea to create a straightforward, portable assay for salmonella based on colloidal gold colorimetry.

“When the sample mixture contains salmonella, the upper layer is released thanks to the salmonella RNase H specifically cleaving the DNA-RNA linker probe.

“When the gold-containing solution is then drained onto an absorbent pad with a nylon membrane, a clear red spot indicates the presence of salmonella in the sample being tested,” explained the researchers.

The scientists further examined the system’s selectivity and asserted that it did not mistakenly detect the presence of other bacteria that had RNAse H.

The gadget is an “easy-to-use” colorimetric assay, according to the scientists, that is based on a novel nucleic acid probe that has been cleaved by an RNase enzyme unique to the Salmonella species.


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The team claims that their testing procedure is “much less complex than other methods for detecting salmonella” and is also substantially faster.

“In contrast to other methods, only one hour of incubation in a pipette tip is required for highly sensitive detection of salmonella, for example, in ground beef,” said the researchers.

In the future, the researchers plan to create more nucleic acid probes that can particularly identify other infectious bacteria like E. coli.

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