Listeria monocytogenes was isolated from critical control points in a Danish turkey processing plant, from turkey products and from cases of human listeriosis. During processing in the plant the prevalence of L. monocytogenes ranged from 25.9 to 41.4%. Cleaning and disinfection decreased the prevalence to 6.4%. 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 after cleaning and disinfection. Two identical DNA types were demonstrated among isolates from turkey products and human cases of listeriosis. The prevalence 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 contamination of the turkeys.
Forty Listeria monocytogenes isolates obtained in European and Far East regions of Russia were differentiated on the basis of polymorphism of 5 markergenes. Total length of concatemers obtained after sequencing of internal fragments of genes inlA, inlB, inlC, inlE and prs was 3029 b.p. Comparative analysis of concatemers' sequences revealed 237 variable nucleotides. Totally, 25 sequence types were revealed, and isolates from European and Far East regions belonged to different types. On the dendrogram isolates split on 2 clusters, which correspond to early described phylogenetic lines of L. monocytogenes specie. Isolates obtained in European and Far East regions formed independent subclusters within main clusters. Fifteen clinical isolates of L. monocytogenes belonged to 7 different types. Analysis of epidemiologic data on time and place of isolates obtaining suggested that isolates of the same sequence type are epidemiologically related and might represent one strain; index of discrimination for proposed typing method was calculated as 0.982.