The complex landscape of plants and microbe interaction means that food safety specialists should consider fine detail and cannot generalise when carrying out risk assessments, new research by James Hutton Institute scientists has shown.
Fresh produce is an important vehicle for transmission of disease-causing bacteria like Eschericia coli, and experimental evidence shows that they can colonise plants as secondary hosts, but differences in the capacity to colonise occur between different plant species and tissues.
Therefore, an understanding of the impact of these plant factors have on the ability of bacteria to grow and establish is required for food safety considerations and risk assessment.
In a new study, Hutton researchers working alongside partners in the rest of the UK and Ireland have determined whether growth and the ability of bacteria to form biofilms in plant extracts could be related to specific plant metabolites or could predict the ability of the bacteria to colonise living plants.
Dr Nicola Holden, a molecular bacteriologist based within the Institute’s Cell and Molecular Sciences group and co-author of the research, said: “Growth rates for sprouted seeds, including alfalfa and fenugreek, exhibited a positive relationship between plant extracts and living plants, but not for leafy vegetables such as lettuce and spinach.
“Therefore, the detailed variations at the level of the bacterial isolate, plant species and tissue type all need to be considered in risk assessments.”
While outbreaks of vegetable-associated E. coli outbreaks are rare in the UK as a result of strict control measures at all stages of the food chain from plough to plate, they do still occur, as was seen in 2013 when contaminated watercress entered the food chain resulting in seven people being hospitalised.
By understanding the mechanisms of how the bacteria interact with plants, researchers are hoping to find targeted ways to stop the binding, reducing the risk of food contamination.
The paper The influence of plant species, tissue type and temperature on the capacity of Shigatoxigenic Escherichia coli to colonise, grow and internalise into plants, by Bernhard Merget, Ken J. Forbes, Fiona Brennan, Sean McAteer, Tom Shepherd, Norval J.C. Strachan and Nicola J. Holden, is in the latest issue of Applied and Environmental Microbiology.