The Canadian Food Inspection Agency (CIFA) recently provided insight into how whole genome sequencing (WGS) and international data-sharing helped trace a 2020 multinational food safety outbreak of Listeria monocytogenes to enoki mushrooms, enabling countries to rapidly recall the affected products.
WGS is a tool that can be used to map out the DNA of pathogenic bacteria found in food, allowing scientists to compare bacteria from a food sample to samples obtained from infected people or other contaminated food. Bacteria that are closely related based on WGS are referred to as a "match" and are more likely to have originated from the same source. Such information can be useful in foodborne illness outbreak investigations.
During the investigation of the 2020 outbreak linked to enoki mushrooms, the U.S. Centers for Disease Control and Prevention (CDC) contacted the Public Health Agency of Canada (PHAC) to inquire if there were any Canadian matches to clinical samples from U.S. patients sickened in the outbreak. Because CFIA regularly sends WGS data from food samples to PHAC to monitor for matches with clinical samples, a match was quickly found between U.S. clinical samples and a CFIA sample of enoki mushrooms imported from the Republic of Korea.
During 2017–2019, there were six known cases of foodborne illness in Canada associated with the strain of L. monocytogenes identified by WGS in the contaminated enoki mushrooms. In the U.S., the outbreak resulted in four deaths and 31 hospitalizations. Throughout the multinational investigation, CFIA shared information about the enoki mushrooms with U.S. officials, helping to identify the source of the outbreak and take appropriate action, including recalling affected products.
Information relating to the investigation, including WGS data, was also shared with the International Food Safety Authorities Network (INFOSAN) and international partners through the secure INFOSAN community website, resulting in further food safety action in other countries. In addition to Canada and the U.S., the investigations led to further recalls of enoki mushrooms in Australia.