Listeria Outbreak in Leafy Greens Prompts Change in CDC Listeria Questionnaire

Investigations into a multi-state, multi-year listeriosis outbreak continue. In September 2015 PulseNet, the Centers for Disease Control and Prevention’s (CDC) national molecular subtyping network for food-borne disease surveillance, identified a cluster, indistinguishable by two-enzyme pulse-field gel electrophoresis (PFGE). The cluster was defined as an isolation of Listeria with an isolation date on or after July 5, 2015, the isolate date of the earliest case in the cluster.

According to the CDC’s Notes from the Field, “A standardized Listeria questionnaire was used to gather information about foods consumed in the 4 weeks before illness from seven persons identified by November 30, 2015, with isolation dates occurring July 5, 2015—October 30, 2015.” However, the tool did not include leafy green vegetables and failed to assist in identifying a common source for the infections.

The CDC then began to engage patients or their surrogates through open-ended interviews and shopper card records between December 2015 and January 2016. All of the patients who were interviewed reported consuming leafy greens in the month before the onset of their illness. Among those interviewed, 88% reported consuming romaine lettuce and 75% reported consuming spinach: “Six patients (75%) recalled consuming packaged salad, and three patients (38%) recalled consuming packaged salad brands processed by Company A.”

“Company A” has since been identified as Dole Food Co., currently under investigation for failing to report Listeria for more than a year before shutting down on January 27, 2016, after PulseNet analyzed sequenced data from Listeria isolated from samples obtained from their Springfield, OH facility. The company recalled all salad mixes, including 22 varieties of packaged salads sold under various brand names produced in Springfield.

This is the first outbreak of listeriosis associated with leafy greens and the eighth reported outbreak of listeriosis associated with fresh produce in the United States since 2008. The CDC Notes go on to clarify that, “It is unclear whether the appearance of these outbreaks might be attributed to improved outbreak detection, changes in consumer behavior, or changes in production and distribution. Fresh produce processors are advised to review food safety plans and consider incorporating measures to avoid the growth and persistence of Listeria. The Listeria Initiative questionnaire has been revised to include additional questions about fresh produce to better identify produce vehicles of Listeria.”

Recently, consumers in Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee, and Virginia, who purchased pre-packaged, fresh-cut vegetable products were urged to return the products for a full refund amidst a new recall by Country Fresh, LLC in Conroe, Texas. “The product bears “BEST IF USED BY” dates between August 7, 2016 (8/7/16) through August 19, 2016 (8/19/16).”

Eight retailers received the fresh-cut vegetables, packaged in clear plastic “clamshell” containers and Styrofoam trays wrapped in clear plastic film. The retailers are:

• BI-LO
• Fresh Point
• Harris Teeter Supermarkets
• Publix Supermarkets Inc
• QuikTrip
• The Spinx Company
• Wal-Mart Stores Inc
• Winn Dixie

At the time of publication, no illnesses related to the recall have been reported.