Isolation and characterisation of Listeria monocytogenes from piggeries in France

Abstract

Recent analyses of human listeriosis outbreaks showed that these were associated with consumption of delicatessen items or pork products from other sources. Serotyping of impli- cated strains demonstrated that they belonged mainly to serotype 4b. Serotype 4b Listeria mono- cytogenes was rarely among isolates from slaughterhouses, which belonged mainly to serotype 1/2a. A study was carried out on 32 pig herds to describe the situation regarding this pathogen. Combining different sampling sites Listeria monocytogenes was found in 6 (18.7%) of the herds. Considerable strain diversity among isolates from the 6 herds (6 different serotypes) was showed. Moreover a herd carrying strains of serotype 4b was identified. Using RFLP-PFGE we were able to describe a difference between strains of this serotype. The study suggests that the role of pigs as a primary source of serotype 4b strains in the pork production chain should be reconsidered. Introduction Foodborne diseases are a significant public health concern in many countries. Whether or not is listeriosis associated more with meningitis, neonatal mortality and abortion than gastrointestinal disturbance, Listeria monocytogenes is well recognised as a cause of food- borne outbreaks. The main food sources have been known for many years (1, 2) and involve the consumption of cheese and vegetables (3), but epidemiological investigation of recent outbreaks clearly associated cases with consumption of delicatessen items and further processed pork products from other sources (4-6). Nowadays measures taken to control potential pathogens in the food production chain tend to follow a stable-to-table approach. Many studies have charac- terised the strains of Listeria isolated at different stages of the pork production chain including