Shiga toxin-producing Escherichia coli outbreaks in California’s leafy greens production continuum

Authors: Lacombe, Alison; Quintela, Irwin; Liao, Yen-Te; Wu, Vivian

Submitted to: Frontiers In Food Science And Technology
Publication Type: Review Article
Publication Acceptance Date: 12/13/2022
Publication Date: 12/22/2022
Citation: Lacombe, A.C., Quintela, I.A., Liao, Y., Wu, V.C. 2022. Shiga toxin-producing Escherichia coli outbreaks in California’s leafy greens production continuum. Frontiers In Food Science And Technology. 2. Article 1068690. https://doi.org/10.3389/frfst.2022.1068690.
DOI: https://doi.org/10.3389/frfst.2022.1068690

Interpretive Summary: Recently leafy greens have been the subject of several high-profile E. coli outbreaks. The outbreak that occurred in 2020 represents a continuous pattern of E. coli contamination in California's leafy green production environment. The U.S. Food and Drug Administration has investigated the 2019 outbreak and traced the source of contamination to cattle on nearby lands. It is suspected that water used in agriculture can convey contamination to the lettuce plants. This finding, along with other evidence, suggests an urgent need to further investigate the potential sources of contamination and develop interventions. In addition, as climate change continues, this crisis will be exacerbated. One major concern is that is extreme droughts will severely limit the supply of safe water available for crops. This review closely examines the potential factors, such as soil, water, and time of year that can contribute to leafy green contamination.

Technical Abstract: Despite heavy investment in controlling pathogenic hazards in agriculture, leafy greens grown in California were exposed to several high-profile outbreaks of Shiga toxin-producing E. coli (STEC). The U.S. Food and Drug Administration (FDA) analysis of outbreaks found three reoccurring patterns in the STEC outbreaks on leafy greens in 2018-2020: the presence of pathogenic E. coli, common geographical regions, and issues with activities on adjacent land. The FDA response to the recurring outbreaks associated with leafy greens has published the Leafy Greens STEC Action Plan (LGAP). The FDA collaborated with U.S. Environmental Protection Agency (EPA) to create a regulatory pathway for the approval of commercial sanitizers that can be applied to agricultural irrigation water to combat STEC. However, there are several real-world limitations and economic consequences, such as the potential to overuse sanitizing products, that negatively impact leafy green and soil quality. Therefore, a targeted approach to the leafy green-STEC problem in California is urgently needed. This review aims to analyze the recent STEC outbreaks on leafy greens in California and the potential role of agricultural water and adjacent land use in the contamination mechanism. The review considers the factors involved in leafy green production, such as agriculture water, climate change, and adjacent land use, that could contribute to an increased susceptibility for pathogen contamination.