Genomic approaches for detection and prevention of listeriosis outbreaks

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The bacterium Listeria monocytogenes (LM) is the causative agent of listeriosis, a severe foodborne infection. Listeriosis is characterized by a high hospitalization rate and a fatality rate of up to 30%, the highest among foodborne infectious diseases. Whole genome sequencing of clinical LM isolates has recently improved recognition of epidemics of listeriosis and the identification of their infection sources. Based on the obtained genomic data almost 2/3 of all listeriosis cases occur in infection clusters with up to more than 100 isolates, some of them protracting over years or decades. Pathogen microevolution during these long-lasting listeriosis outbreaks will be used to empirically define variability cut-offs to increase the reliability of listeriosis outbreak detection and to identify genetic determinants that make long-lasting outbreaks possible. We hypothesize that biocide tolerance and growth as biofilm are important factors in the resilience of LM in food production facilities, and the manifestation of protracted outbreaks. This hypothesis will be tested by screening an established LM model population for biocide tolerance. The subsequent genetic association study will include the improvement of the currently applied core genome based methodology by the inclusion of mobile genetic elements. This project will improve the current methodology for listeriosis outbreak detection while the obtained information on biocide tolerance is important for outbreak prevention. The tools and methodologies developed will be easily transferable to other bacterial pathogens.