Serotyping is the process of categorizing subtypes within the same species of microorganisms that share a common characteristic. Serotyping is a time-consuming process; for salmonella, it can take up to three days. Some serovars can take up to 12 days to serotype. But now, researchers from Cornell, the Mars Global Food Safety Center in Beijing, and the University of Georgia have been able to serotype salmonella in hours, rather than days.
It’s important to be able to determine the serotype of salmonella because it helps food safety workers find the source of bacterial contamination, which could come from fruits, nuts, meat, cereal, and more. Lead study author, Dr. Silin Tang, says, “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."
Conventional serotyping is expensive and time-consuming, which led to a new method for identifying different subtypes called whole-genome sequencing. There are 38 strains and 34 subtypes of salmonella. The researchers were able to accurately predict the serotype through whole-genome sequencing. The new test uses relatively simple equipment which means that testing can now be done in more labs. According to researcher Martin Wiedmann, Ph.D., “For the food industry, processing plants are in the middle of nowhere. Now you can conduct testing in a lab that’s close to the food processing plant.”
According to Wiedmann, different salmonella serotypes come from different places. He used chicken pot pie as an example. “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."
The study is published in the online journal, Food Microbiology.