Comparative investigations of Listeria monocytogenes isolated from a turkey processing plant, turkey products, and from human cases of listeriosis inDenmark

Listeria monocytogenes was isolated from critical control points in a Danis h turkey processing plant, from turkey products and from cases of human lis teriosis. During processing in the plant the prevalence of L. monocytogenes ranged from 25.9 to 41.4%. Cleaning and disinfection decreased the prevale nce to 64%. Isolates of L. monocytogenes were characterized by pulsed-field gel electrophoresis (PFGE) using restriction endonuclease ApaI. Identical DNA types were obtained from turkey products and the processing line even a fter cleaning and disinfection. Two identical DNA types were demonstrated a mong isolates from turkey products and human cases of listeriosis. The prev alence of L. monocytogenes in turkey products ranged from 7.3 to 17.4% for ready-to-eat products and raw products, respectively. Since none of the 27 flocks examined before slaughter sampled positive for L. monocytogenes and the prevalence increased during processing, the potential risk from turkey meat was apparently due to factory hygiene rather than intrinsic contaminat ion of the turkeys.