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By: Juan Archila

More Americans are now seeking a healthy lifestyle and finding easy ways to engage with meal preparation. As part of a healthy diet, fresh fruits and vegetables are needed for your body to get essential nutrients and prevent chronic diseases. Leafy greens (including lettuce, spinach, kale, etc.), especially those in packaged salads, have become popular since they are easy to incorporate into healthy meals. Most packaged salads commonly say: “Triple washed,” “Thoroughly washed,” or “Ready to eat,” which makes consumers feel safe about eating the leafy greens. However, some of them have been involved in recalls and outbreaks related to harmful microorganisms’ contamination. The question is, how can this happen if they are supposed to be safe?

If we compare the ratio of safe leafy greens grown, delivered, and consumed with the ones that have been involved in recalls and outbreaks, you will notice that the safer leafy greens exceed those contaminated with harmful microorganisms. These harmful microorganisms are so tiny that you cannot see them with your naked eye, and you will only know your leafy greens are contaminated when symptoms show up. Some of those harmful microorganisms include bacteria, viruses, and parasites. This, however, is NOT a justification for those packaged salads that have been involved in recalls and outbreaks. These outbreaks have negatively affected the overall population, with severe consequences on high-risk populations, including adults aged 65 and older, children younger than five years, immunocompromised, and pregnant women.


nuts and parsley in a bowl photo by UnsplashDifferent microorganisms can contaminate those leafy greens inside packaged salads, including pathogenic E. coli, norovirus, Salmonella, Listeria, and Cyclospora. But the most common microorganism identified in these unfortunate scenarios is E. coli O157:H7, which can potentially cause life-threatening diseases. There are many routes along the supply chain where harmful microorganisms like E. coli can contaminate the leafy greens you consume. That contamination could come from the farm, transportation, packing or processing facility, retailer, and even home. For example, leafy greens can be contaminated with harmful bacteria if the irrigation water used is contaminated with cattle feces. In the food production industry, it is very important to recognize that everyone shares responsibility for the safety of these food products. This means that in each step from farm to table, everyone needs to pay special attention to how leafy greens are being handled to decrease the incidence of harmful microorganisms contamination and growth.


The way each microorganism works to cause symptoms may be different from each other and could lead to various adverse outcomes. For example, those outbreaks in which Listeria monocytogenes is involved could lead to negative consequences (e.g., miscarriages, stillbirths, preterm labor) in pregnant women and their newborns.

The following timeline summarizes some multistate leafy greens outbreaks in the past five years (it does not include fresh herbs or sprout outbreaks).

Multistate leafy greens outbreak timeline
2022 Leafy greens mixed (packaged salads) E. coli O157:H7
2021 Leafy greens mixed (packaged salads) Listeria monocytogenes
2021 Leafy greens mixed (packaged salads) Listeria monocytogenes
2021 Baby spinach (packaged salads) E. coli O157:H7
2021 Leafy greens mixed (packaged salads) Salmonella Typhimurium
2020 Leafy greens E. coli O157:H7
2020 Iceberg lettuce, red cabbage, and carrots (packaged salads) Cyclospora
2019 Leafy greens mixed (packaged salads) E. coli O157:H7
2019 Romaine lettuce E. coli O157:H7
2018 Romaine lettuce (packaged salads) E. coli O157:H7
2018 Leafy greens mixed (packaged salads) Cyclospora
2018 Romaine lettuce E. coli O157:H7


Continuous efforts have been made by the industry, government agencies, and academia to mitigate this public health risk. Even though there is specific regulation for produce safety, the Food Safety Modernization Act (FSMA) Produce Safety Rule, action plans have also been developed. These action plans are based on “prevention, response and knowledge gaps.” The prevention includes the implementation of the science-based standards that are stipulated in the Produce Safety Rule. The response consists of actions being followed to investigate produce outbreaks, including surveillance systems. And the knowledge gaps include the understanding of produce contamination using science to mimic harmful microorganisms’ dynamics.

This is too much information to process! So, let’s summarize it!

1. Packaged salads should be safe for consumption because their production must follow food safety practices.

2. Sometimes, packaged salads could be contaminated with harmful microorganisms. But that DOES NOT mean all of them are contaminated.

3. Industry, government agencies, and academia are working together to continue providing safe produce to consumers.

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Juan Carlos Archila Godinez

Juan Carlos Archila Godinez

Graduate Research Associate



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