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When DFI Marketing Inc. (Fresno, CA) recalled some cantaloupe melons on September 12, 2012, the story went something like this:

  • DFI routinely samples products for food borne pathogens prior to harvest; the testing is carried out by third-party labs.
  • The company’s internal sampling of the cartons involved in the recall were negative for Salmonella.
  • USDA found Salmonella on a single sample of cantaloupe during routine testing conducted at a wholesale produce distribution center (terminal market).
  • DFI, in consequence, recalled approximately 28,000 cartons of cantaloupes packed on August 26, 2012 as a precaution.

As so often happens in today’s world of sub-distributors and further processors, the DFI recall triggered others – including a September 13th recall announcement from Cut Fruit Express, Inc. (Inver Grove Heights, MN) and several supermarket chains. This time, though, there was an unusual wrinkle to the story.

Yesterday morning (Sept. 18th), I received an email from the Director of Quality Systems at one of the affected companies. This person had just been advised by their supplier that Salmonella had been found on the knife used to sample the DFI cantaloupe, and that DFI had been “cleared.” Naturally, my correspondent was eager to get to the bottom of this. As was I.

While my correspondent checked with FDA and with DFI, I queried USDA. Both FDA and DFI responded that the rumor was false; DFI even commented that they had heard the same rumor the day before from a different source.

Today, I received the following detailed reply from Shayla Mae Bailey, from the USDA Agricultural Marketing Services’ Public Affairs desk:

I received your inquiry about the DFI Cantaloupe recall, and spoke with the MDP program about the rumors surrounding the lab’s results. Below is more detail about how samples are handled during our testing.

The Microbiological Data Program (MDP) recently reported a positive Salmonella enteritidis detection in cantaloupe to the Food and Drug Administration. The cantaloupes were distributed by the firm, DFI Marketing, Inc. of California, and were collected and tested in Colorado. Questions have surfaced about the validity of MDP’s reported results, especially in regard to sample handling and possible control contamination. MDP stands by its results. To ensure the reliability of results MDP relies on the expertise of trained State Department of Agriculture sample collectors.

Collectors follow standard operating procedures (SOPs) and use aseptic technique (one-time use sterile gloves and sterile collection bags) when collecting samples for MDP. Collected samples are properly packaged and shipped the same day for overnight delivery to a MDP testing laboratory. After chain-of-custody receipt requirements are met, experienced laboratory personnel also use aseptic technique and follow SOPs to prepare samples for testing. To remove the chance for contamination, no cutting or slicing occurs for any MDP samples prior to or during any testing procedures.

When a positive is initially detected, MDP requires additional confirmation and this usually involves as many as five additional tests to be performed on the positive samples. In addition to the multiple confirmatory tests, MDP requires the laboratories to use special fluorescent-tagged controls throughout all testing procedures. These fluorescent-tagged controls allow for quick identification and also insures that a positive detection is a true result and not a control contamination. All MDP laboratories have achieved ISO 17025 certification and follow the Centers for Disease Control and Prevention guidelines for handling bacterial pathogens. For more details on MDP testing procedures, SOPs are accessible online at the website, www.usda.ams.gov/mdp.

Bottom line: The USDA stands by its results. The rumor is false. The recall is real.

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