E. coli outbreaks linked to leafy greens grown in the California Central Coastal region have plagued the area since 2017, despite efforts to stop them. The most recent outbreak, in the fall of 2020, prompted an FDA investigation; the agency published its findings in April 2021.
The investigation found that samples collected in response to leafy greens outbreaks in 2019 and 2020 contained the same strain of Shiga toxin-producing E. coli (STEC) O157:H7. In light of this finding, FDA analyzed trends across outbreaks that had occurred each fall since 2017 and found three key trends in the contamination of leafy greens by E. coli O157:H7 in recent years: a reoccurring strain, a reoccurring region, and reoccurring concerns with the potential impacts of adjacent lands.
According to Jim Gorny, PhD, senior science advisor for produce safety at FDA’s Center for Food Safety and Applied Nutrition in College Park, Md., the reoccurring pathogenic E. coli strain appears to be a reasonably foreseeable hazard, specifically in the South Monterey County area of the Salinas Valley and Santa Maria Valley growing regions.
FDA’s report recommended that agricultural communities in the affected areas work to identify where the reoccurring strain of pathogenic E. coli is persisting in the environment and the likely routes of lettuce contamination with the strains of STEC. Furthermore, FDA encouraged producers in the Central Coast of California growing region to participate in the California Longitudinal Study, an initiative launched in November 2020 to improve food safety after continued E. coli outbreaks, and in a locally led, locally convened workgroup organized by the California Department of Food and Agriculture and the Monterey County Farm Bureau to identify what actions can be taken to reduce contamination.
When pathogens are identified through microbiological surveys or pre-harvest or post-harvest testing, FDA recommends that growers implement industry-led root cause analyses to determine how the contamination likely occurred and then implement appropriate prevention and verification measures, Dr. Gorny says.
Another Step: Updating the Leafy Greens Action Plan
In addition to its investigation, FDA has updated its Leafy Greens STEC Action Plan (LGAP), originally released in 2020, for 2021. The new plan includes steps the agency will take in collaboration with leafy green stakeholders to advance lettuce safety.
The update is informed by work and knowledge gained over the past year. “New actions have been added based on information collected and lessons learned, including those from the 2020 investigative report,” Dr. Gorny says. “The updated plan includes a renewed emphasis on actions to prevent contamination stemming from activities on adjacent land, announces new actions that build on the accomplishments and learnings from the 2020 plan, and renews FDA’s commitment to complete certain actions that were difficult to accomplish in 2020 due to challenges presented by the COVID-19 pandemic.”
In commenting on the updated LGAP, Ben Miller, MPH, PhD, senior director of scientific and regulatory affairs at The Acheson Group, a global food safety consulting group based in Bigfork, Mont., says, “These approaches have been updated for 2021 to better understand how STEC can move from the surrounding environment and contaminate produce grown in California and Arizona. Based on investigations in 2019 and 2020, addressing risks from nearby cattle operations form the basis of many updates in the 2021 plan.”
The updated LGAP includes 33 specific action items.
A Closer Look at LGAP
The updated LGAP emphasizes three components:
- Enhancing prevention strategies;
- Improving response activities by FDA and other entities; and
- Identifying and addressing knowledge gaps that exist around STEC contamination of leafy greens.
Regarding prevention strategies, Dr. Miller says the new approaches are largely focused on irrigation water and adjacent land use; however, the close proximity of cattle to these growing areas and unknown routes of contamination from the environment to leafy greens makes developing and validating effective mitigation and control measures difficult.