Research shows microbiological contamination of organic produce is low

By Cara Hungerford

July 29, 2004: Researchers in the United Kingdom collected and tested 3,200 samples of raw organic vegetables for microbial contamination and found 15, or 0.5 percent of those samples to be contaminated, testing positive for either E. Coli or Listeria ssp.

While food poisoning incidents attributed to fruits and vegetables in general are relatively low—only 1.4 percent to 3 percent of outbreaks reported in the U.S. with similar figures reported for Europe*—they still remain a concern for consumers. Organic produce in particular has been questioned because of its close relationship to manure, a common carrier of microbial pathogens, especially E. Coli. The goal of the study was to determine the actual risk posed by organic produce.

S.K. Sagoo and associates from the Environment Surveillance Unit in London gathered and tested 3,200 samples of vegetables from retail outlets ranging from supermarkets to doorstep box-scheme deliveries. All vegetables shared two common characteristics: They could be consumed with only light washing, and they were either grown in close proximity of the soil or were a common salad vegetable such as cucumber, pepper or tomato. British Standards were used to determine contamination levels.

The researchers found E. coli to be present in 1.5 percent of the samples but at contamination level in only 0.3 percent, or 11, of the 3200 samples tested, while Listeria spp. (not including L. monocytogenes) was detected in six samples and considered contaminating in four of those samples Listeria monocytogenes, Salmonella spp., Campylobacter spp., and E. Coli O157 were not detected in any of the samples.

*Figures from the European Commission Scientific Committee on Food’s Risk Profile on the Microbiological Contamination of Fruits and Vegetables Eaten Raw, April 2004.


Sagoo, S. K., et al., 2001. The microbiological examination of ready-to-eat organic vegetables from retail establishments in the United Kingdom. The Society for Applied Microbiology (33) 434-439.