Understanding the ecology of Listeria and its interactions with microbiomes in food processing facilities to inform biocontrol strategies

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There are over one million cases of food poisoning in the UK each year with an estimated economic burden of £1.5 billion. Listeria monocytogenes is one of the five major causes of food poisoning. It is a particular problem with chilled foods such as unpasteurised milk, soft cheeses, salads and many of the ready-to-eat, chilled foods. L. monocytogenes can cause meningitis, still births and abortion, in vulnerable groups including pregnant women, the elderly, and the neonates. In Europe, 2161 confirmed cases of listeriosis were reported in 2014, a rise of 30% on the previous year. In comparison to other food-borne diseases the incidence of listeriosis is relatively low, however the disease is associated with significant public health and economic burdens because of its high mortality rate of up to 30%.This project will provide a knowledge base of factors that influence survival of Listeria in the food processing environment where it is able to colonise many sites, particularly damp, moist conditions such as drains, floors, wash areas and food handling surfaces. Despite robust cleaning and sanitising procedures, Listeria spp. persist in the environment. While we know a great deal about the genetics and persistence of Listeria spp. originating from clinical samples, Listeria spp. present in food factory environments have not been studied to the same degree, and there remains a significant gap in our understanding of: (a) the genetic makeup of Listeria strains that are found in food processing factories and (b) how these Listeria spp. interact with diverse bacterial species of the factory microbial communities. This proposal will address these gaps in our knowledge. We will work closely with the food processing sector and analyse swabs obtained from different types of surfaces within food processing factories. These samples will then be used to identify both the Listeria spp. and associated factory bacteria. The whole genome sequence will be determined to track the pathogen through different parts of the processing factory and this will provide unique insight into routes of contamination within the factory and the persistence of particular Listeria spp. in specific areas of the factory. To survey the complete diversity of bacteria in the factory environment we will use advanced DNA based fingerprinting methods to identify which other types of bacteria are present in different factory sites and if there is a connection between these bacteria and presence/absence of the Listeria strains at a particular location. Whole genome sequence data will also provide insight into the genes associated with biofilm formation, biocide resistance and association as complex communities with other bacteria.Strong evidence suggests that Listeria persists in the environment because of its ability to form biofilms (where bacteria grow as communities on solid surfaces). We will therefore determine the ability of the Listeria isolates to form biofilms, both individually and also in the presence of other bacteria isolated from the factory surfaces to assess how these bacteria impact biofilm formation by Listeria spp. and their persistence in the factory. These biofilm studies will be examined in a 'model factory' that we will set up in the IFR lab to recreate diverse surfaces and simulate factory environmental conditions. To undertake this multidisciplinary programme we have assembled a collaborative team of technical experts from the food industry and academic research scientists. This research will provide improved understanding of the behaviour and survival of Listeria spp. in food processing environments. Our ultimate aim is to provide detailed, extensive knowledge to inform the industrial development of new methods to reduce Listeria spp. levels in the food processing environment. These improved methods will be shared as 'best practice' with the wider chilled food industry, eventually leading to significant health / economic benefits.