New research finds that E. coli O157:H7 can spread more than a tenth of a mile downwind from a cattle feedlot onto nearby produce. In the study, first author Elaine D. Berry of the U.S. Department of Agriculture’s U.S. Meat Animal Research Center and her colleagues sampled leafy greens growing in nine plots (three each at 60, 120, and 180 meters downwind from the cattle feedlot at the research center) over a two-year period. The rate of contamination with the pathogenic E. coli O157:H7 declined with distance. There was an average positive sample 3.5 percent of the time at 60 meters and 1.8 percent at 180 meters. The findings suggest that current buffer-zone guidelines of 120 meters (400 feet) from a feedlot may be inadequate. Transmission of the pathogens is thought to be airborne. The researchers found E. coli in air samples at 180 meters from the feedlot, though the instruments were not sensitive enough to pick up E. coli O157:H7. The highest levels of contamination on the produce were in August and September of 2012 after several weeks of very little rainfall and several days of high temperatures, conditions that appear to aid airborne transport of bacteria. The research was published ahead of print in the journal Applied and Environmental Microbiology.
