Identifying the Source of Foodborne Outbreaks: WGS, the New Sleuth on the Block

Foodborne infectious outbreaks are a major public health and food safety concern. Their successful detection and investigation depends upon microbiological and epidemiological tools being used in concert with food traceback studies to define and quantify the number of cases, identify the pathogen, detect the source of infection, and determine the route of transmission. This enables effective control measures to be implemented and action to be taken to stop further cases and prevent future outbreaks. Tracing food back to its source is often complicated; many foods go through multiple processing and distribution steps, which may involve more than one country. Once the food source has been established, the point at which and exactly how contamination occurred needs to be determined to enable implementation of effective public health measures.

Whole genome sequencing (WGS) offers unprecedented resolution for determining the genetic relatedness of bacterial strains and has proven to be a transformational tool for investigating foodborne infectious illness. The application of WGS to foodborne bacterial pathogens is able to provide strong microbiological evidence in identifying clusters and outbreaks previously unidentified by conventional typing and surveillance tools; to link isolates from human illness with those from food and environmental samples; to refine case definitions in outbreaks and, thus, hone epidemiological investigations. In addition the phylogenetic context derived from WGS can provide enhanced source attribution and evidence for the initial point of contamination in the food chain. This presentation will demonstrate how WGS of bacterial foodborne pathogens is being used by Public Health England to improve the investigation of foodborne bacterial disease.