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Human pathogens in fresh produce

Status quo, routes of entry and influence of storage conditions.

Adulteration of foods with human pathogenic bacteria is a persistent food safety risk. Most of the pathogenic bacteria that cause foodborne disease are associated with foods of animal origin. In contrast to this, there is only limited information available on the presence of human pathogenic bacteria in fresh produce. As these products are often consumed in unprocessed and raw form, without appropriate inactivation of the microorganisms by a heat processing step, a high hygienic standard during processing is essential. The most important human pathogens such as Salmonella spp., EHEC, Listeria monocytogenes and Yersinia spp. commonly occur in the plant growing environment,  can persist there for very long times and contaminate the product during growing and and harvesting.

Against this background, the Department of Microbiology and Biotechnology and the Department of Safety and Quality of Fruit and Vegetables work together closely in an inter-departmental project that aims to monitor the prevalence of human pathogens in fresh plant products such as carrots, cucumbers, herbs, green and mixed salads. The studies serve to provide data on the incidence of relevant human pathogens in these food products in Germany. For this, samples are investigated at regular intervals for the incidence and contamination levels of pathogens such as Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, Bacillus cereus, as well as pathogenic Escherichia coli, including enterohaemorrhagic E. coli (EHEC) strains. Molecular biological methods such as multiplex PCR or quantitative PCR protocols are developed and applied together with classical microbiological cultivation techniques in order to detect, isolate and characterize pathogens from fresh produce. The influence of storage conditions on the growth of human pathogens in vegetable products will be assessed in challenge experiments. The use of bacteriophages as biocontrol tool to combat human pathogens in vegetal products is a specific decontamination strategy that will be investigated in this project.

This project is partly funded by the QS-Science Fund. Project duration: 1 year (May 2016 until April 2017).