Control of Listeria monocytogenes in the fresh produce supply chain. Industry-match funded project 3

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Fresh produce (salads and herbs) are considered essential for a healthy nutritious diet but may be exposed to environmental contamination in the farm and factory. Potential health risk is exacerbated due to fresh produce not being cooked. Of particular concern is contamination of fresh produce with Listeria monocytogenes, a pathogen responsible for only a small number of foodborne outbreaks but it causes a serious gastrointestinal infection which can be extremely debilitating for immunocompromised patients, causes miscarriage in pregnant women and has the highest mortality of all the major foodborne pathogens. It is widely found in soil and water and can grow over a range of temperatures, including chill temperatures of 4oC which are found in food processing and storage. We showed it forms monoculture biofilms over the temperature range and can become viable but nonculturable (VBNC) depending on nutrient availability, temperature and disinfection stress. The VBNC phenotype means that its presence is missed using the ISO approved, gold standard culture recovery methods, presenting a public health risk if food is deemed free of pathogens. Little is known about its ability to survive in polymicrobial biofilm communities (microbiomes) present in food supply chains and how interactions may support pathogen persistence, antimicrobial resistance including to sanitisers regularly used by the food industry, and the VBNC state in the presence or absence of sanitisers. The aims are: Develop appropriate sample recovery and molecular methods to detect microbiomes and culturable and VBNC L. monocytogenes at critical points in the supply chain. Determine possible synergistic or antagonistic interactions in supporting L. monocytogenes persistence in the supply chain. Determine appropriate sanitisation procedures for factory cleaning using appropriate laboratory models of factory biofilms of microbiomes and L. monocytogenes. Validate lab studies with on-site factory testing of suitable sanitisers to determine real life safe operating conditions.