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Spotlight on Salmonella: Understanding pathogens of concern for fruit and vegetable farms

February 7, 2022
A microscope image of Salmonella bacteria dark blue against a light blue background.

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By Ollie Cultrara, Vermont Agency of Agriculture, Food and Markets

What comes to mind when you hear the phrase “produce safety”? You may have heard about foodborne illness outbreaks, such as the recent outbreaks of E. coli linked to baby spinach or Salmonella linked to onions. Because many fruits and vegetables are commonly eaten raw, we can’t rely on cooking to kill any harmful bacteria, viruses, or parasites that may be hitching a ride on our produce. Here in the Agency’s Produce Program, when we say “produce safety,” we mean protecting fresh fruits and vegetables from becoming contaminated with pathogens that can get people sick.  

Understanding the pathogens we’re most concerned about—where they come from, the environments they thrive in, and how they spread—is key to preventing contamination from happening in the first place. Let’s look at one category of pathogens that is a culprit in some foodborne illness outbreaks: Salmonella bacteria. 

What’s at stake 

Bacteria in the genus Salmonella are responsible for over 1 million infections in the U.S. each year. Salmonella is the pathogen most frequently implicated in foodborne illness outbreaks that have been linked to fresh fruits and vegetables. Most people with a Salmonella infection experience diarrhea, fever, and stomach cramps. While many infections last for a week or less and do not require treatment, serious cases can lead to additional, more severe, or long-lasting symptoms. In rare cases, infection may cause life-threatening complications. Those at the highest risk for severe illness from foodborne pathogens include young children, older adults, and people who are pregnant or have weakened immune systems—but anyone can become sick from contaminated food. 

How it spreads 

Salmonella bacteria can live in the intestines of animals, including livestock, wildlife, pets, and humans, and they are widely distributed in the environment. If soil, water, worker hands or clothing, tools, equipment, or other surfaces that touch food come into contact with feces, they can transfer potential pathogens to produce. Factors to consider when assessing risks of Salmonella contamination in fruit and vegetable production include livestock and wildlife activity (especially birds), manure and compost use, agricultural water quality, worker hygiene, and sanitation. 

Bacteria need nutrients, moisture, and the right temperatures to grow and divide. Salmonella bacteria can attach to crop surfaces and be transported through plant tissues. When the tissue of produce is cut or damaged, sugars can be released, providing a nutrient source for any pathogenic or spoilage bacteria present on the surface to multiply. In areas and equipment used for handling produce, spaces where water and organic debris collect are important to clean regularly to avoid allowing these "harborage points” to become environments where bacteria can thrive. 

Reducing risks 

Farms are biodiverse environments where both beneficial and potentially harmful microorganisms are present, but microbial risks can be managed. Good agricultural practices to reduce the risk of produce becoming contaminated with pathogenic Salmonella include: 

  • Avoiding harvest of produce with visible animal damage or feces 
  • Excluding birds and other animals from buildings where produce and related equipment, such as harvest containers, are handled and stored 
  • Reinforcing good hygiene practices, including regular handwashing and clean clothing 
  • Understanding and protecting the quality of water used on produce 
  • Routinely cleaning, and when appropriate, sanitizing, food contact surfaces  

Next steps 

The Food Safety Modernization Act (FSMA) Produce Safety Rule (PSR) is a federal regulation that aims to prevent foodborne illnesses related to fresh fruits and vegetables. The PSR sets a science-based, national standard for safely growing, harvesting, packing and holding produce on farms. The Rule focuses on microbial contamination risks – conditions that could spread harmful pathogens to produce.  

Whether or not your farm is subject to inspection under the PSR, the Vermont Agency of Agriculture’s Produce Program can help you implement practices to protect food safety on your farm. Contact the Vermont Produce Program at AGR.FSMA@vermont.gov, (802) 461-5128. For more information, visit agriculture.vermont.gov/produceprogram

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