Multistate Outbreak of<i>Listeria monocytogenes</i>Infection Linked to Delicatessen Turkey Meat

TLDR

Molecular subtyping has revealed increasing listeriosis outbreaks, including a 2000 cluster of Listeria monocytogenes with identical PFGE patterns identified by NYC health authorities, highlighting the persistent challenge of contamination in food processing plants. The study aimed to quantify the outbreak’s magnitude and identify infection risk factors through a case‑control investigation. Cases were defined as patients or mother‑infant pairs with the outbreak PFGE pattern and controls as those with different patterns; participants reported 30‑day food and drink histories during May–December 2000 across 11 states. The outbreak caused 4 deaths and 3 miscarriages, was linked to sliced processed turkey from a delicatessen (OR 8.0, 95 % CI 1.2–43.3), traced to a single processing plant that recalled 16 million pounds of meat, and underscored the ongoing challenge of persistent Listeria contamination in food processing.

Abstract

Despite a decreasing incidence of listeriosis in the United States, molecular subtyping has increased the number of recognized outbreaks. In September 2000, the New York City Department of Health identified a cluster of infections caused by Listeria monocytogenes isolates with identical molecular subtypes by pulsed-field gel electrophoresis (PFGE) and ribotyping.To determine the magnitude of the outbreak and identify risk factors for infection, we notified state health departments and conducted a case-control study. A case was defined as a patient or mother-infant pair infected with Listeria monocytogenes whose isolate yielded the outbreak PFGE pattern. Controls were patients infected with Listeria monocytogenes whose isolate yielded a different PFGE pattern. Patients were asked about food and drink consumed during the 30 days before the onset of illness.Between May and December 2000, there were 30 clinical isolates of Listeria monocytogenes with identical PFGE patterns identified in 11 US states. Cases of infection caused by these isolates were associated with 4 deaths and 3 miscarriages. A case-control study implicated sliced processed turkey from a delicatessen (Mantel-Haenszel odds ratio, 8.0; 95% confidence interval, 1.2-43.3). A traceback investigation identified a single processing plant as the likely source of the outbreak, and the company voluntarily recalled 16 million pounds of processed meat. The same plant had been identified in a Listeria contamination event that had occurred more than a decade previously.Prevention of persistent L. monocytogenes contamination in food processing plants presents a critical challenge to food safety professionals.