BACKGROUND: Contaminated dairy products are common sources of foodborne outbreaks. In June 2016, the North Carolina Division of Public Health detected a cluster of Salmonella Typhimurium isolates with indistinguishable pulsed-field gel electrophoresis (PFGE) patterns. In July, a routine sample of raw milk from a local creamery (Creamery A) yielded Salmonella Typhimurium with an indistinguishable PFGE pattern. We investigated to identify opportunities for product contamination and prevent further illnesses.
METHODS: We defined a case as isolation of the outbreak strain from a specimen collected during April 24–August 15, 2016, from a North Carolina resident or visitor. We completed outbreak questionnaires for cases identified before August and conducted an on-site visit and product sampling with the North Carolina Department of Agriculture.
RESULTS: We identified 109 cases; 16 (15%) were hospitalized. Median patient age was 29 years (range: 1–92). We interviewed 46 of 61 (75%) patients identified before August; 26 (57%) respondents reported eating ≥1 Creamery A cheese. The creamery produced raw-milk cheeses aged ≥60 days and pasteurized cheeses in a 3-room, on-site facility. Few physical barriers existed between milking, production, and processing rooms; the same staff handled unfinished and finished products. The outbreak strain was isolated from a sample of a raw-milk cheese commonly consumed by patients (n = 21; 46%). Creamery A recalled all products on July 27 and began working with food safety experts to remediate and re-open.
CONCLUSIONS: Consumption of cheeses produced from contaminated raw milk resulted in a substantial Salmonella outbreak. Contamination likely resulted from a cheese aging-process failure or cross-contamination at the creamery. Physical barriers and adherence to good hygiene practices are necessary to reduce the risk for product contamination.