An international team of scientists have developed a new method that expedites the identification process of salmonella, offering a more efficient method for food makers.
At present, serotyping is the conventional scientific process used to identify the presence of Enterobacteriaceae family bacterial. For salmonella, it used to take three days and, in some cases, more than twelve days to assign a final classification for complex servovars.
But now, researchers from Cornell University and the University of Georgia in the US and the Mars Global Food safety Centre in Beijing have developed a method for whole-genome sequencing to determine salmonella serotypes in just two hours and the whole identification process within eight hours.
“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 lead author Silin Tang, research scientist in microbial risk management at the Mars Global Food Safety Centre.
Conventional serotyping has been at the core of public health monitoring of salmonella infections for a half-century, Tang said. But long turnaround times, high costs and complex sample preparations have led global food safety regulators, food authorities and public health agencies to change to whole-genome sequencing methods for pathogen subtyping.
All 38 salmonella strains – representing 34 serotypes – assessed in this study were accurately predicted to the serotype level using whole-genome sequencing.
This is important news for the food industry, as very few laboratories can conduct classical serotyping, said Martin Wiedmann, the Gellert Family Professor in Food Safety and a Cornell Institute for Food Systems faculty fellow.
“In some countries, it can take up to two days to even get the suspected salmonella to a certified lab,” Wiedmann said.
With whole genome sequencing, the new state-of-the-art test relies on simple equipment. “For the food industry, processing plants are in the middle of nowhere,” he said. “Now you can conduct testing in a lab that’s close to the food processing plant.”
Different salmonella serotypes often come from different places, said Wiedmann, who explained the process through an example: chicken pot pie.
“Where does the salmonella come from?” he said. “You have carrots, peas, obviously chicken, and spices. If you have salmonella enteritidis – that’s usually associated with chicken – then you look for and track down the source of the chicken.
“If you have salmonella virchow, the serotype usually associated with food in southeast Asia, then you want to track down the spices from there. … Serotyping provides food safety scientists with a priority list of where to look.”
Their research was published in the journal Food Microbiology.