Dirty Equipment Blamed for Cantaloupe Listeria Outbreak

The cause of the deadliest U.S. foodborne illness outbreak in a quarter century has been linked to pools of water on the floor and old, hard-to-clean equipment at a Colorado farm’s cantaloupe packing facility.

Investigators from the Food and Drug Administration (FDA) found positive samples of listeria bacteria on equipment in the Jensen Farms packing facility and on contaminated Rocky Ford cantaloupes that had been held there. The Centers for Disease Control and Prevention said the Jensen Farms’ outbreak has thus far sickened at least 123 people and killed 25 across 26 states. One miscarriage has also been attributed to the contaminated melons.

The incident is the deadliest known case of foodborne illness in the U.S. since an outbreak of listeria in Mexican-style cheese in 1985.

In a six-page assessment of the conditions at the farm based on investigators’ visits in September, the FDA said Jensen Farms recently bought used equipment that was corroded, dirty and hard to clean. The packing facility floors also were constructed so they were hard to clean, so pools of water potentially harbouring the bacteria formed close to the packing equipment, according to media reports.

Investigators said the dirty equipment, coupled with reported unsanitary conditions and unsafe food handling practices at 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.

"This is the deadliest food-borne outbreak in the United States in more than 25 years," said Barbara Mahon, MD, deputy branch chief of enteric diseases at the CDC.

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.

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.

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.

Industry experts said conditions at the packing facility were atypical for most produce packing houses. "I've been to a lot of produce handling facilities and again, the key issues were sanitary facility design, sanitary equipment design, and post-harvest handling” James Gorny, a senior advisor for produce safety at the FDA's Center for Food Safety and Applied Nutrition in College Park, Md., was quoted as saying. “None of these were typical for a typical post-harvest handling operation of any fruit or vegetable," Gorny added.

The FDA has issued a warning letter ordering the owners of Jensen Farms to correct the problems at the open-air packing facility and are also reportedly weighing other sanctions against the farm.