E. coli can live for weeks around the roots of produce plants and transfer to the edible portions, but the threat can be minimized if growers don’t harvest too soon, a Purdue University study shows.
Purdue scientists added E. coli to soil through manure application and water treated with manure and showed that the bacteria can survive and are active in the rhizosphere, or the area around the plant roots, of lettuce and radishes. E. coli eventually gets onto the aboveground surfaces of the plants, where it can live for several weeks. Activity in the rhizosphere was observed using a bioluminescent E. coli created by Bruce Applegate that glows when active. Applegate, a co-author on the project, is an associate professor in the food science and biological sciences departments at Purdue.
“E. coli is actually quite active in the rhizosphere. They’re eating something there – probably plant exudates,” said Ron Turco, a professor of agronomy and co-author of the study published in the November issue of the Journal of Food Protection.
Turco said the E. coli didn’t survive on the plants’ surfaces more than 40 days after seeds were planted. Harvesting produce at least 40 days after planting should reduce the possibility of contamination, but he warned that E. coli could still come from other sources.
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