Purpose: In late June and July 2013, CDC, FDA’s Coordinated Outbreak Response and Evaluation Network (CORE) and state partners investigated an outbreak of five LM cases from four states, including one adult death and one fetal loss; the isolates had indistinguishable PFGE patterns. Rapid epidemiologic, traceback, and molecular analyses were used to identify the contaminated food and prevent additional illnesses.
Methods: State and local partners shared epidemiological information with CDC. CDC notified CORE of the cluster and identified soft cheese epidemiologically as a suspect exposure. FDA/CORE’s research of past environmental isolates matching this PFGE pattern combination identified a Wisconsin cheese manufacturer (Company A) with a history of colonization by this LM strain. CORE shared this information with CDC to assist the epidemiologic investigation. State and local partners collected and analyzed household and retail products, in addition to environmental samples. FDA/CORE conducted a traceback investigation from several points of service to Company A, while FDA and the Wisconsin Department of Agriculture jointly inspected Company A.
Results: All patients reported definite or probable consumption of a Company A cheese. The LM outbreak strain was isolated from two retail samples collected by Minnesota Department of Agriculture and one product sample collected during inspection of Company A. The traceback and facility investigations determined the contamination most likely occurred at Company A. The firm ceased all cheese production and voluntarily recalled its product. Root cause analysis efforts are ongoing.
Significance: This outbreak highlights the effectiveness of federal and state collaboration to rapidly identify and remove a contaminated product from the marketplace, thereby protecting public health.