Submitted to: Morbidity and Mortality Weekly Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2011
Publication Date: 4/8/2011
Citation: Delaune, E., Sokol, T., Ratard, R., Kissler, B., Allen, L., Seys, S., Ward, T.J., Silk, B., Jackson, K., Graves, L., Trees, E. 2011. Outbreak of invasive listeriosis associated with the consumption of hog head cheese, Louisiana, 2010. Morbidity and Mortality Weekly Reports. 60:401-405. Interpretive Summary: Listeria monocytogenes is a food-borne bacterium that places a serious burden on human health and the agricultural economy. Listeria monocytogenes is responsible for over one-quarter of foodborne disease-related deaths linked to known pathogens, and L. monocytogenes contamination has been a leading cause of food recalls in recent years. Rapid detection of listeriosis outbreaks and identification of contaminated food is critical to containing foodborne disease. This report describes the successful application of molecular subtyping in an epidemiological investigation identifying an association between the outbreak of invasive listeriosis and hog’s head cheese contaminated with L. monocytogenes. This investigation resulted in a voluntary recall of approximately 500,000 pounds of hog’s head cheese and smoked andouille sausage from a single production facility in Louisiana on August 14, 2010. In addition to limiting the potential for further illness, this study provides information on the integration of multiple molecular subtyping platforms, and will be of direct interest to epidemiologists, food-processors and distributors, public health and food inspection agencies, and scientists involved in food safety research.
Technical Abstract: A cluster of eight cases of laboratory-confirmed invasive listeriosis was reported to the Louisiana Office of Public Health (OPH) between February and June of 2010. All eight clinical isolates were Listeria monocytogenes, serotype 1/2a and had indistinguishable pulsed-field gel electrophoresis (PFGE) patterns. A more in depth epidemiological investigation and an environmental investigation were initiated on July 26. Food history questionnaires were completed by interviewing four cases. Three cases reported eating hog’s head cheese (a pork product made from the head and feet), which was purchased at two different grocery stores in Louisiana. A single brand of hog’s head cheese was common between the two grocery stores. L. monocytogenes, serotype 1/2a was cultured from one of three product samples; the product isolate had a PFGE pattern that was indistinguishable from the clinical isolates. On August 14, the Louisiana Department of Agriculture and Forestry (LDAF) coordinated the voluntary recall of approximately 500,000 pounds of hog’s head cheese and sausage due to potential contamination with L. monocytogenes. L. monocytogenes was also detected in two environmental samples collected by LDAF at the production facility. One isolate had a PFGE pattern that was indistinguishable from the product and clinical isolates. This report describes the successful application of PulseNet and CDC’s Listeria Initiative (1) in identifying an association between the outbreak of invasive listeriosis and hog’s head cheese. Hog’s head cheese is a novel food vehicle for listeriosis and a ready-to-eat (RTE) meat, which is subject to the U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) “zero tolerance” policy for L. monocytogenes contamination in the United States (2,3).