Scientists discover a better way to test the presence of Salmonella in ... - Interesting Engineering

Infections caused by Salmonella bacteria are a health hazard. The Centres for Disease Control and Prevention (CDC) estimates that the bacteria causes around 1.35 million infections, 26,500 hospitalizations, and 420 deaths in the U.S each year. This foodborne disease has a strong resistance factor and fast reproduction rate. Foodborne illnesses such as Salmonella costs the U.S over $15.6 billion each year.

There are various methods available today to detect the disease, however these approaches are time consuming, labor intensive and cost a lot of money.

A team of researchers from McMaster University have developed a faster and better test method to check for Salmonella contamination in food products like chicken. Claiming that it's easier to use than a home Covid-19 test, the new method could potentially improve food safety, reduce the processing cost of food items, and help reduce recalls made to food batches that have been contaminated.

What makes the test work?

The test developed by the team at McMaster University in Hamilton, Canada, has two components.

The first is a new synthetic nucleic acid molecule that interacts with Salmonella, which was developed in-house by the team. This molecule is sandwiched between layers of gold microscopic particles. The composite material lines the inside of the tip of a glass pipette. When a liquified sample of a food is drawn inside the tube, that interaction leads to an action.

Here we come to our second component. If salmonella is present, the bacteria will cut through the gold microparticles allowing nucleic acid to escape into the liquid sample. When this solution is dropped onto a piece of paper, the droplet will change color to red to mark the presence of salmonella. The greater the concentration of the bacteria, the brighter the shade of red.

Researchers performing the test

The test can be performed without a power source and takes about an hour to yield accurate results. The research team says that in comparison to today's monitoring through lab cultures, which require at least a full day to produce results, their newly developed test method is far better.

"Anyone can use it right in the setting where food is being prepared, processed or sold," says co-author of the study, Yingfu Li, a professor of Biochemistry and Chemical Biology who leads McMaster's Functional Nucleic Acids Research Group.

Study abstract:

An Au-on-Au tip sensor is developed for the detection of Salmonella typhimurium(Salmonella), using a new synthetic nucleic acid probe (NAP) as a linker for the immobilization of a DNA-conjugated Au nanoparticle (AuNP) onto a DNA-attached thin Au layer inside a pipette tip. In the presence of Salmonella, RNase H2 from Salmonella (STH2) cleaves the NAP and the freed DNA-conjugated AuNP can be visually detected by a paper strip. This portable biosensor does not require any electronic, electrochemical or optical equipment. It delivers a detection limit of 3.2×103 CFU mL−1 for Salmonella in 1 h without cell-culturing or signal amplification and does not show cross-reactivity with several control bacteria. Further, the sensor reliably detects Salmonella spiked in food samples, such as ground beef and chicken, milk, and eggs. The sensor can be reused and is stable at ambient temperature, showing its potential as a point-of-need device for the prevention of food poisoning by Salmonella.

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