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Food Poisoning Health Center

Dirty Equipment Likely Led to Listeria Outbreak

Investigators Say Unsafe Food Handling Also Had Role in Cantaloupe Contamination
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WebMD Health News
Reviewed by Laura J. Martin, MD

Oct. 19, 2011 -- Results of an investigation by state and federal health officials have shed light on how cantaloupes grown by a Colorado farm became contaminated with deadly listeria bacteria.

Investigators say dirty, corroded equipment, unsanitary conditions, and unsafe food handling practices at a packing facility used by Jensen Farms likely allowed listeria bacteria to grow and spread to melons that were washed and refrigerated there.

No listeria was found in the fields where the cantaloupes were grown.

Tainted "Rocky Ford" cantaloupes from Jensen Farms have thus far sickened at least 123 people and killed 25 across 26 states. One miscarriage has also been attributed to the contaminated melons.

"This is the deadliest food-borne outbreak in the United States in more than 25 years," says Barbara Mahon, MD, deputy branch chief of enteric diseases at the CDC. She spoke at a news briefing to announce early results of an official investigation into the cause of the outbreak.

Problems identified by investigators include:

  • Water that pooled and sat under packing equipment.
  • Processing equipment that was difficult to clean and sanitize.
  • Refrigeration practices that likely allowed condensation to form on the melons. Experts say condensation is an ideal environment for listeria growth.

Additionally, packing equipment installed at the facility in July had been previously used to wash and pack potatoes. Officials say they aren't worried about a similar listeria outbreak in potatoes since those vegetables are rarely eaten raw.

A truck parked next to the packing area also made frequent trips to a nearby cattle farm. Listeriosis -- the illness caused by listeria bacteria -- is a common infection in livestock like cattle, sheep, and goats. The bacteria they shed can live in soil, manure, and grass.

Testing of Samples

FDA inspectors collected 39 environmental samples at the packing facility used by Jensen Farms on Sept. 10, 2011. Tests showed that 13 of those, including some taken from refrigerated melons and some from food contact surfaces, were positive for strains of listeria bacteria that were involved in the outbreak.

Conditions at the packing facility were not typical in the produce packing industry.

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