Real-time WGS monitoring identifies L. monocytogenes outbreaks in The Netherlands and contributes to a rapid detection of the source

Whole genome sequencing (WGS) is increasingly used by food regulatory agencies and public health institutes. It is a powerful tool to identify the source of a foodborne outbreak. Real-time WGS analysis helps to act fast during a foodborne outbreak, and with that the impact of an outbreak can be significantly decreased. In The Netherlands real-time WGS analysis is performed for L. monocytogenes originating from humans and from the food chain, and WGS data is shared between the food regulatory agencies (WFSR and NVWA) and the public health institute (RIVM). Consequently, by molecular typing and cluster analysis probable infection sources of L. monocytogenes are identified. These analysis already identified 18 clusters of human L. monocytogenes isolates related to food isolates, and also several clusters that might suggest persistence of L. monocytogenes in different production environments. Real-time WGS analysis for example contributed to the fast identification of the source of a ST-6 L. monocytogenes outbreak originating from ready-to-eat meat products, and the subsequent termination of this outbreak. The timeframe of human cases (n=19) and strains isolated from the RTE meat products, together with the genetic relatedness of the strains suggest that the source of the outbreak was a L. monocytogenes strain which persisted in the production environment. This shows the effectiveness of real-time WGS analysis in solving foodborne outbreaks in the Netherlands and its potential for the food industry in the prevention of these outbreaks in the future.