Environmental Sampling

The U.S. Food and Drug Administration (FDA) is conducting inspections of harvest operations and collecting environmental samples from harvest equipment after an outbreak strain of Listeria monocytogenes was recovered from harvest equipment in 2022. The FDA is seeking to gain insights about the potential for human pathogens to persist on harvest equipment after routine cleaning and sanitizing and to be subsequently transmitted to produce. Accordingly, the agency has designed this assignment, which centers on the inspection and swabbing of harvest equipment. This assignment is a part of the FDA’s Leafy Greens STEC Action Plan, an ongoing preventative effort to help ensure the microbiological safety of leafy greens.

Questions and Answers

What types of harvest equipment will the FDA inspect?

The inspections will focus on equipment used in the harvest of “carton ready” and “process ready” leafy greens. This is expected to include equipment used in field harvest activities related to fully intact lettuce heads and lettuce intended for processing.

How has the FDA selected the inspection sites?

The inspections will focus on the harvest operations of three produce companies and entities with whom they work (e.g., growers, harvesters). The three produce companies have been linked or potentially linked to leafy green outbreaks of foodborne illness in recent years. The inspections will be conducted in three states: Arizona, California, and Florida.

What microbial hazards is the FDA testing for? 

Listeria monocytogenes and E. coli O157:H7.

When will the FDA conduct the inspections?

The FDA plans to conduct the inspections from July 2023 through March 2024. Inspections will occur during the leafy green harvest season in Arizona, California, and Florida.

How many inspections will occur, and how many samples does the FDA plan to collect for this assignment?

There will be 36 inspections in all, and the FDA plans to swab one harvester per inspection. At least two samples will be collected per inspection (i.e., one sample to test for each analyte), and each sample will consist of at least 64 environmental swabs.

How will the samples be collected?

The agency will notify each farm of the inspection typically a few days in advance. At each inspection, one harvest machine will be inspected. The FDA will observe employee practices during active harvest, including the operation of harvest equipment. FDA investigators, with potential participation by the state agencies, plan to collect swab samples after routine cleaning and sanitizing of equipment. They will employ standard techniques outlined in the FDA’s Investigations Operations Manual (Chapter 4.3), which describes the use of sterile equipment and aseptic procedures.

Who will conduct the testing?

The FDA will test the samples at its laboratories, and in all cases, the samples will be shipped overnight, irrespective of which agency lab they may be sent to.

Should a farm pause use of the harvest equipment that was swabbed and/or hold associated product pending notification of test results?

These decisions rest with the farm. During the inspection and sampling, the investigator will ask if the farm plans to voluntarily pause use of the harvest equipment that was swabbed and/or hold associated product pending notification of test results and will note the farm’s response accordingly.

What regulatory action will the FDA take if it detects Listeria monocytogenes and/or E. coli O157:H7?

The FDA will evaluate the possibility that produce came into contact with an equipment surface that yielded a human pathogen and the related possibility that produce became contaminated. If product is contaminated with a pathogen or may have been contaminated with a pathogen, the FDA will consider follow-up action. As part of our consideration, we will make a determination about what product corresponds to the positive sample result. The FDA will notify the responsible party/parties at the farm (typically, its owner or operator). The FDA will discuss with the farm what voluntary action the farm intends to take concerning the harvest equipment and, more importantly, with respect to any product either found to be contaminated with a pathogen or that may have been contaminated with a pathogen. The FDA also will consider whether a broader follow-up inspection is warranted and what actions may be needed. The goal of a follow-up inspection would be to help the farm management identify practices or equipment that may present contamination risks so that they can strengthen the microbiological safety of their operation.