Research unveils new food-borne illness link

The threat to human health occurs because these bacteria are not simply sitting on the surface of the plant and are particularly difficult to remove post-harvest.

The E-coli outbreak in Germany linked to infected cucumbers, which has so far claimed 10 lives, could be an indication that fruit and vegetables are ingesting these bacteria as they grow, according to a Scottish scientist.

Dr Nicola Holden of The James Hutton Institute is leading research into the presence of bacteria such as Escherichia coli O157:H7 and Salmonella enterica in fresh fruit and vegetables and has found that washing alone may not be enough as the bacteria can be inside the food itself.

“Food-borne illness has traditionally been associated with undercooked meat products and eggs. However, we have seen a recent rise in the number of outbreaks associated instead with fresh fruit and vegetables; in particular foods that are eaten raw or lightly cooked, like salad vegetables, fresh fruit and sprouted beans,” explained Dr Holden.

“The outbreaks, which are thankfully still very unusual, have been caused by bacteria that we are already familiar with, such as Escherichia coli O157:H7 and Salmonella enterica, but the surprise was finding the bacteria associated with plants and not animals.

“The bacteria are able to get from animal sources on to crops through different routes, most likely in irrigation water or sometimes from slurry spraying, while some contamination can also occur during processing and packaging.

“Although some bacteria land directly on the plants, we know that they are able to grow to much higher numbers in the vicinity of plant roots, despite heavy competition from microbes already in the soil.

“From the root system the bacteria then have the opportunity to move to the edible foliage or fruits. They are able to cope with the plant defence systems and continue to grow in a relatively protective environment as the plants themselves continue to grow until harvest.

“The threat to human health occurs because these bacteria are not simply sitting on the surface of the plant and are particularly difficult to remove post-harvest,” she added.

Fortunately these types of outbreaks are still relatively rare because the majority of fresh produce in the UK is rigorously checked by the producers and only a very small proportion will fall 'though the net'. Potential problems arise because the foods are eaten raw and not cooked, unlike meat and most egg products.

Notes for Editors

The James Hutton Institute has research centres in Dundee and Aberdeen. It was formed earlier this year by the coming together of the Macaulay Land Use Research Institute and SCRI, the Scottish Crop Research Institute. It employs about 600 scientists, researchers and support staff and is one of the biggest food, land and environment research centres in Europe.

The Scottish Government is the principal customer of The James Hutton Institute. In 2011-2012 the Scottish Government will be investing £25M in research and associated initiatives at the Institute.