On October 19, 2011, FDA released a document which provides an overview of factors that potentially contributed to the contamination of fresh, whole cantaloupe with the pathogen Listeria monocytogenes, which was implicated in a 2011 multi-state outbreak of listeriosis. In early September 2011, the Food and Drug Administration (FDA), in conjunction with the Centers for Disease Control and Prevention (CDC) and state health departments, began to investigate a multi-state outbreak of listeriosis. Early in the investigation, cantaloupes from Jensen Farms in the southwest region of Colorado were implicated in the outbreak.

On September 10, 2011, FDA, along with Colorado state officials, conducted an inspection at Jensen Farms during which FDA collected multiple samples, including whole cantaloupes and environmental (non-product) samples from within the facility, for laboratory culturing to identify the presence of Listeria monocytogenes. Of the 39 environmental samples collected from within the facility, 13 were confirmed positive for Listeria monocytogenes with pulsed-field gel electrophoresis (PFGE) pattern combinations that were indistinguishable from three of the four outbreak strains collected from affected patients. Cantaloupe collected from the firm’s cold storage during the inspection was also confirmed positive for Listeria monocytogenes with PFGE pattern combinations that were indistinguishable from two of the four outbreak strains.

As a result of the isolation of outbreak strains of Listeria monocytogenes in the environment of the packing facility and whole cantaloupes collected from cold storage, and the fact that this is the first documented listeriosis outbreak associated with fresh, whole cantaloupe in the United States, FDA initiated an environmental assessment in conjunction with Colorado state and local officials. FDA, state, and local officials conducted the environmental assessment at Jensen Farms on September 22-23, 2011. The environmental assessment was conducted to gather more information to assist FDA in identifying the factors that potentially contributed to the introduction, growth, or spread of the Listeria monocytogenes strains that contaminated the cantaloupe.

FDA identified the following factors as those that most likely contributed to the introduction, spread, and growth of Listeria monocytogenes in the cantaloupes:

Introduction:

• There could have been low level sporadic Listeria monocytogenes in the field where the cantaloupe were grown, which could have been introduced into the packing facility
• A truck used to haul culled cantaloupe to a cattle operation was parked adjacent to the packing facility and could have introduced contamination into the facility

Spread:

• The packing facility’s design allowed water to pool on the floor near equipment and employee walkways;
• The packing facility floor was constructed in a manner that made it difficult to clean
• The packing equipment was not easily cleaned and sanitized; washing and drying equipment used for cantaloupe packing was previously used for postharvest handling of another raw agricultural commodity.

Growth:

• There was no pre-cooling step to remove field heat from the cantaloupes before cold storage. As the cantaloupes cooled there may have been condensation that promoted the growth of Listeria monocytogenes.

FDA’s findings regarding this particular outbreak highlight the importance for firms to employ good agricultural and management practices in their packing facilities as well as in growing fields. FDA recommends that firms employ good agricultural and management practices recommended for the growing, harvesting, washing, sorting, packing, storage and transporting of fruits and vegetables sold to consumers in an unprocessed or minimally processed raw form.

FDA has issued a warning letter to Jensen Farms based on environmental and cantaloupe samples collected during the inspection. FDA’s investigation at Jensen Farms is still considered an open investigation.

Jensen Farms' Recall

Jensen Farms voluntarily recalled its whole cantaloupes on Sept. 14 in response to the multi-state outbreak of listeriosis. Cantaloupes from other farms have not been linked to this outbreak.

FDA has successfully audited the majority of Jensen Farms’ direct and secondary accounts. The recalled cantaloupes were produced from the end of July to September 10, 2011. Given that the Jensen Farms’ recall has been in effect for more than a month and that the shelf life of a cantaloupe is approximately two weeks, it is expected that all of the recalled whole Jensen Farms cantaloupes have been removed from the marketplace.

FDA has verified that the following states received recalled cantaloupes directly from Jensen Farms: Arizona, Arkansas, Colorado, Idaho, Illinois, Indiana, Kansas, Louisiana, Minnesota, Missouri, Montana, Nebraska, New Jersey, New Mexico, New York, North Dakota, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, Utah, Wisconsin and Wyoming. There is no indication of foreign distribution.

Consumer Safety Information

Listeria can grow at refrigerator temperatures, about 40◦ Fahrenheit (4◦ Celsius). The longer ready-to-eat refrigerated foods are stored in the refrigerator, the more opportunity Listeria has to grow.

It is very important that consumers clean their refrigerators and other food preparation surfaces. Consumers should follow these simple steps:

• Wash hands with warm water and soap for at least 20 seconds before and after handling food.
• Wash the inside walls and shelves of the refrigerator, cutting boards and countertops; then sanitize them with a solution of one tablespoon of chlorine bleach to one gallon of hot water; dry with a clean cloth or paper towel that has not been previously used.
• Wipe up spills in the refrigerator immediately and clean the refrigerator regularly.
• Always wash hands with warm water and soap following the cleaning and sanitization process.

FDA advises consumers not to eat the recalled cantaloupes and to throw them away. Do not try to wash the harmful bacteria off the cantaloupe as contamination may be both on the inside and outside of the cantaloupe. Cutting, slicing and dicing may also transfer harmful bacteria from the fruit’s surface to the fruit’s flesh.

Listeriosis is rare but can be fatal, especially in certain high-risk groups. These groups include older adults, people with compromised immune systems and unborn babies and newborns. In pregnant women, listeriosis can cause miscarriage, stillbirth, and serious illness or death in newborn babies, though the mother herself rarely becomes seriously ill. A person with listeriosis usually has fever and muscle aches. Persons who think they might have become ill should consult their doctor.

For more information on the epidemiologic investigation, please refer to CDC’s Investigation on the Multi-State Listeriosis Outbreak 2.