In early September 2011, the US Food and Drug Administration and US Centers for Disease Control began investigating a multiple state outbreak of listeriosis in which cantaloupe was the suspected infection vehicle. Four outbreak strains of Listeria monocytogenes were found in 26 U.S. states, leading to 29 deaths and 33 additional illnesses. Settlements to the families may cost $150 million1.

The bacteria that causes Listeria monocytogenes produces varying symptoms depending on a person’s risk factors. Generally listeriosis starts with diarrhea followed by fever and muscle aches similar to flu-like symptoms. Pregnant women will develop flu-like symptoms as well as endure side effects including miscarriage, stillbirth, premature delivery or a fatal infection of the newborn infant. Elderly people with comprised immune systems and young children may develop headache, stiff neck, mental confusion, loss of balance and convulsions that sometimes result in fatal meningitis or encephalitis. Most people do not remember the source of the infection because symptoms can occur between three days to two months after the infection occurs2.

The Colorado Department of Public Health and Environment reported it had nine cases of listeriosis including two deaths on September 2, 2011 prompting the US Food and Drug Administration (FDA) and US Centers for Disease Control (CDC) to commence an urgent investigation of the multiple state outbreak in which cantaloupe was the suspected infection vehicle3.

On September 10, 2011 the US FDA and Colorado state officials visited Jensen Farms and collected multiple samples. Of the 30 environmental swabs taken, 13 were confirmed positive for Listeria monocytogenes with pulsed-field electrophoresis (PFGE) pattern combinations that matched three of the four outbreak strains. Twelve of these swabs were from the processing line and one was from the packing area. Additionally cantaloupes from the firm’s cold storage area were confirmed positive for Listeria monocytogenes with PFGE pattern combinations that matched two of the four outbreak strains.

Rocky Ford cantaloupes from Jensen Farms were recalled on September 14, while cut product from Carol’s Cuts and Fruit Fresh Up (both of which purchased whole cantaloupes from Jensen Farms) were recalled on September 23 and October 6, respectively.

Evaluating the Jensen Farms operation, the US FDA identified factors that most likely caused the introduction, spread and growth of Listeria monocytogenes in the facility. The problem may have been introduced by low levels of Listeria monocytogenes in the field where the cantaloupe were grown or through contamination of the packing facility by a truck that hauled culled cantaloupes to a cattle operation.The bacteria may have been spread by water collecting near the machinery and employee walkways, hard-to-clean floors and/or machinery in the packing facility, or equipment previously used for other agricultural products. Bacteria growth may have been caused by condensation stemming from the lack of a pre-cooling step to remove field heat from the cantaloupe before cold storage4.

If the facility had followed non-binding recommendations for minimizing microbial food safety hazards in melons that were published by the US FDA in July 20095, these problems might have been averted. Mandatory produce safety standards are scheduled to be promulgated under the Food Safety Modernization Act of 2010, providing new enforcement authorities for the US FDA.

SGS has testing labs throughout the world that can test for Listeria monocytogenes.

1 Listeria Cantaloupe Outbreak Could Cost $150 million
2 More Deaths in Listeria/Cantaloupe Outbreak
3 Colorado Department of Health warns of Listeria outbreak
4 US FDA Information on the Recalled Jensen Farms Whole Cantaloupes
5 US FDA Guidance for Industry: Guide to Minimize Microbial Food Safety Hazards of Melons

James Cook
SGS – North America, Inc.
291 Fairfield Avenue
Fairfield, NJ 07004

t: + 1 (93) 575-5252

The SGS Group is the global leader and innovator in inspection, verification, testing and certification services. Founded in 1878, SGS is recognised as the global benchmark in quality and integrity. With 67,000 employees, SGS operates a network of over 1,250 offices and laboratories around the world.