The FDA is releasing results from its romaine lettuce sampling findings from the Yuma, Arizona area. Lettuce from that area was linked to a deadly E .coli O157:H7 outbreak that killed five and sickened 210 people. Ninety-six people were hospitalized because they were so ill. And twenty-seven patients developed hemolytic uremic syndrome (HUS), a type of kidney failure that is a complication of an E. coli infection.
The FDA collected and tested romaine lettuce from commercial coolers in Yuma County, Arizona during February and March 2021. The lettuce was tested for Shiga toxin-producing E. coli (STEC) bacteria, specifically enterohemorrhagic E. coli (EHEC), and Salmonella. This sampling program was part of the agency’s surveillance after several multistate E. coli O157:H7 outbreaks were linked or potentially linked to romaine in the past few years.
The goal was to determine whether the target pathogens and specific strains were present in the lettuce from that region to help prevent foodborne illness. If product that tested positive for EHEC or Salmonella was found, the agency planned to work with industry and state partners to identify the cause, such as farm follow-up investigations, to develop strategies that could prevent more outbreaks.
The FDA collected 504 romaine samples. The testing was performed by an independent laboratory on contract. Each sample was made up of 10 subsamples, and each subsample contained at least 300 grams of romaine lettuce, either whole heads, hearts, or individual leaves. This method increased the possibility of detecting pathogens, since bacteria are not uniformly present on the lettuce.
The FDA detected E. coli O130:H11 in one sample. The isolate was moderate to high risk and could cause severe illness in humans, but it was not linked to any known human illnesses. None of this product ever reached consumers. The farm owner did not harvest the remaining crop from the field where it was grown.
The FDA then conducted an investigation at the farm to identify possible sources and contamination routes. The FDA collected lettuce from the field, multiple soil samples, water, sediment, and animal fecal material. Farm equipment and other surfaces were also teated. Only one of the 24 samples yielded STEC, from the outer leaves of romaine lettuce. This strain was characterized as low risk to human health. And the strain was not linked with any past known outbreaks.
The FDA continues to work on several fronts to try to prevent microbial contamination of leafy greens and to prevent outbreaks. The FDA’s Leafy Greens STEC Action Plan (LGSP) is still in place, and the agency is collaborating with industry academia, and states in the LGAP to address this issue.
