Researchers in Tennessee, along with scientists at the U.S. Centers for Disease Control and Prevention (CDC) have released a study published in Foodborne Pathogens and Disease about the risk of E. coli O157:H7 in bagged salads. An estimated 63,000 STEC O157 infections occur every year in the United States. Recent outbreaks have been associated with leafy greens such as lettuce and spinach.
The researchers look at an outbreak of STEC O157 that was associated with bagged salads in institutional settings. The outbreak was in schools, and the case-control study was made up of controls matched by school and grade.
Seventeen patients from three states were identified. The median age of a cases was 23 years. Seventy-six percent of the cases were female. Six people were hospitalized and two died in this particular outbreak. The illness onset dates ranged from April 29 to May 12, 2012.
The analytical epidemiology analysis identified a single significant food service exposure: lettuce provided by a school cafeteria. The bagged salad was traced back to a single facility. Growing areas were scheduled for more inspection during the upcoming growing season to see if a source of the contamination, whether runoff from animals farms, problems in harvest or shipping, or some other source could be found.
