Salmonella and E. coli Can Live Inside Plant Tissue
Carefully washing produce is the best way to reduce the risk of foodborne illness, but it can’t always eliminate it. In some cases, Salmonella and E. coli can live inside plant tissues, according to a recent study by researchers at Purdue University1.
Researchers found E. coli 0157:H7 present in the tissues of mung bean sprouts and Salmonella present in peanut seedlings in plants whose seeds had been contaminated with the pathogens prior to planting, according to study results published in separate papers in the Journal of Food Protection and Food Research International.
“The pathogens were in every major tissue, including the tissue that transports nutrients in plants," said Amanda Deering, a postdoctoral researcher in food science.
Deering and Robert Pruitt, a professor of botany and plant pathology, used a fixative to freeze the location of the bacteria in the plant tissues before slicing samples, then injected antibodies labeled with fluorescent dye to detect the pathogens. "This shows us as close to what was in the plant when it was living as possible," said Deering, who was able to count hundreds of bacteria in almost every type of tissue. "The number of bacteria increased and persisted at a high level for at least 12 days, the length of the studies."
Properly washing the produce would eliminate Salmonella and E. coli from its surface, but not inner tissues, Deering and Pruitt said. However, cooking those foods at high temperatures would kill the pathogens. In a project funded by the U.S. Department of Agriculture's Agricultural Research Service, Deering and Pruitt will continue to study the pathogens to determine how they survive inside plant tissues and possible ways to eliminate them.
1. Purdue Press Release: http://www.purdue.edu/newsroom/research/2011/110815DeeringPathogens.html .
