Listeria Outbreak in Jensen Farms Cantaloupes: Lessons Learned

Bacterial contamination recently turned a nutritious, beta-carotene-rich melon into an agent of foodborne illness for some unfortunate consumers. The Denver Post reports October 26 that the multi-state outbreak, traced to Rocky-Ford brand cantaloupes grown at Jensen Farms in Holly, Colorado, has caused 28 deaths and that the Colorado cantaloupe industry will be subjected to stronger oversight. Although all Jensen Farms cantaloupes have been recalled, the Centers for Disease Control and Prevention says further cases of infection may surface in the coming months as Listeria monocytogenes bacteria continues to incubate in human hosts. This foodborne outbreak is the deadliest one in the past 25 years.

An investigation conducted by the Food and Drug Administration (FDA) identified several likely sources of contamination at Jensen Farms, where agricultural practices were not up to par. The report cites several potential factors contributing to the outbreak. These factors fall under two categories:

Cross-contamination of Listeria on farm surfaces

  • Cattle are known carriers of Listeria. The packing shed floor, cantaloupe-transport truck tires and farm equipment might have been contaminated with cattle waste, leading to cantaloupe contamination. Another possibility is that Listeria infected cantaloupes through contact with a used potato-washing machine.

Conditions favorable to Listeria growth

  • The FDA noted a refrigerator drain line allowed water to pool on the floor next to cantaloupe packing equipment, setting up a moist environment conducive to bacterial grow. Additionally, in a departure from normal procedure, cantaloupes were not pre-cooled prior to cold storage, which might have resulted in condensation on the melon surfaces, providing moisture to sustain bacteria. Unlike many other germs, Listeria can grow even in the cold temperatures of the refrigerator. And the uneven surface of cantaloupe provides many “hiding places” for dirt and germs.

According to FDA, the cantaloupe outbreak highlights the importance of employing good agricultural and management practices in packing facilities as well as in growing fields. FDA recommendations include assessing produce facilities and equipment design to ensure adequately cleanable surfaces, eliminating opportunities for the introduction, growth and spread of Listeria. Cleaning and sanitizing procedures were clearly inadequate at Jensen Farms.

Foodborne Illness Prevention for Consumers:

    • Wash fresh produce thoroughly under running water just before eating, cutting or cooking. Even if you plan to peel the produce before eating or scoop it out as you would a melon, it is important to wash it first, according to Use a clean produce brush to scrub the uneven surfaces of fruits like cantaloupe especially well because dirt and germs may be difficult to dislodge. Cut out any bruised areas.

FDA Directions for a Homemade Sanitizer for Food-contact Surfaces

Combine one teaspoon of unscented bleach to one quart of water, flooding the surface and letting it stand for 10 minutes. Then rinse with clean water. Let surfaces air dry or pat them with fresh paper towels.

Bleach solutions become less effective with time, so discard unused portions daily.

  • Clean and sanitize food-contact surfaces. The FDA web page, “Keep Listeria out of Your Kitchen” recommends cleaning hands and kitchen surfaces often in order to prevent Listeria spreading from one surface to another. FDA advises using warm soapy water on food preparation surfaces followed by sanitizing as an added precaution (see directions at right). FDA further recommends cleaning refrigerator walls and shelves regularly with warm water and liquid soap, followed by rinsing. Sanitize the refrigerator monthly, according to FDA, for added caution by using the diluted bleach solution and procedure described in the box at the right.
  • Be armed with knowledge. The website is an excellent source of information on food contamination issues. For example, the site explains that Listeria infection is 20 times more likely in pregnant women than in other healthy adults and can lead to miscarriage, stillbirth or life-long health problems. Knowledge is power, so learn all you can about preventing foodborne illness!

Linda Golodner is President Emeritus of the National Consumers League and Vice Chair of the Water Quality & Health Council.