Scientists develop a quick Salmonella detection method

The conventional scientific process for identifying bacteria’s family — known as serotyping — can be time-consuming. For Salmonella it used to take three days, and in some cases more than 12 days, to assign a final classification for complex servovars.

Researchers have developed a method for completing whole-genome sequencing to determine Salmonella serotypes in two hours, and the whole identification process within eight hours. The study was conducted by researchers from Cornell University, the Mars Global Food Safety Centre in Beijing and the University of Georgia, with its findings published in Food Microbiology.

Determining Salmonella serotypes allows food safety professionals to find the source of bacterial contamination, which can occurs in a range of foods such as fruits, vegetables, nuts, meat, cereal, infant formula and pet food.

“As the food supply chain becomes ever more global and interconnected, the opportunity for food to become contaminated with Salmonella increases. In the fast-moving world of food manufacturing, where rapid identification and response to Salmonella contamination incidents is critical, developing a more efficient pathogen identification method is essential,” said Silin Tang, lead author and senior research scientist in microbial risk management at the Mars Global Food Safety Centre.

Salmonella cells proliferate in an agar plate. Image credit: Mars Global Food Safety Centre.

Global food safety regulators, food authorities and public health agencies are opting to use whole-genome sequencing methods for pathogen subtyping rather than conventional serotyping to monitor Salmonella infections. Researchers have attributed this to the high turnaround times, costs and complex sample preparations associated with conventional serotyping.

The study assessed all 38 Salmonella strains — representing 34 serotypes —and accurately predicted the serotype level for all, using whole-genome sequencing. The findings present good news for the food industry, as very few laboratories can conduct classical serotyping. Whole-genome sequencing enables testing to be conducted in labs close to food processing plants, as the test uses simple equipment.

“In some countries, it can take up to two days to even get the suspected Salmonella to a certified lab,” said Martin Wiedmann, food safety professor and faculty fellow at the Cornell Institute for Food Systems.

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