A Three-Year National Survey of Listeria monocytogenes Prevalence in the Irish Food Chain: Implications for Food Safety

Numerous studies have examined the prevalence of Listeria monocytogenes in different ready-to-eat foods and food processing environments, but they are often confined to a limited range of produce or are limited in time. This talk will present the results of a three-year study on 54 small food businesses spread throughout the island of Ireland that included ready-to-eat foods from four main food categories (seafood, vegetables, meats and dairy produce). Samples from both foods and the processing environment were collected every two months over the three-year course ofstudy. Listeria monocytogenes was isolated using the ISO11290 standard method. Multiplex PCR and Pulse Field Gel Electrophoresis were used to type all isolates obtained in the study, allowing an assessment of the relatedness of isolates from different locations and different food groups. In total, 86 distinct pulsotypes were identified in the study. The overall occurrence of L. monocytogenes in foods was 4.2% and in samples from food processing environments, the prevalence was 3.8%. Meat was found to have the highest rate of L. monocytogenes positive samples (7.5%), whereas, seafood was the lowest (1.7%). Many of the strains identified were found to be repeatedly isolated from particular environments; suggesting that some strains have a persistent phenotype. The implications of the findings of this study for food safety and public health will be discussed.