Risk factors for Listeria monocytogenes contamination in French laying hens and broiler flocks.

The objective of this study was to identify potential risk factors for Listeria monocytogenes contamination in French poultry production. Eighty-four flocks of layer hens kept in cages and 142 broiler flocks were included in this study. For each production type, a questionnaire was submitted to farmers and fecal samples were taken to assess the L. monocytogenes status of the flocks during a single visit to the farm. Two logistic regression models (specific to each production) were used to assess the association between management practices and the risk of L. monocytogenes contamination of the flock. The prevalence of L. monocytogenes-positive flocks was 30.9% (95% CI: 21.0; 40.9) and 31.7% (95% CI: 24.0; 39.4) for cage-layers and broiler flocks, respectively. For layer flocks, the risk of L. monocytogenes contamination was increased when pets were present on the production site. When droppings were evacuated by conveyor belt with deep pit storage, the risk of L. monocytogenes contamination decreased significantly. Feed meal was found to be associated with a higher risk of L. monocytogenes contamination than feed crumb. For broiler flocks, the risk of L. monocytogenes contamination was increased when farmers did not respect the principle of two areas (clean and dirty) at the poultry house entrance. A first disinfection by thermal fogging and the absence of pest control of the poultry house before the arrival of the next flock was found to increase the risk of contamination. When litter was not protected during storage and when farm staff also took care of other broiler chicken houses, the risk of L. monocytogenes contamination increased significantly. In the case of the watering system, nipples with cups were found to decrease the risk of contamination.

Occurrence and distribution of Listeria monocytogenes and other Listeria species in ready-to-eat and raw meat products.

The present study was undertaken to estimate the occurrence and distribution of Listeria monocytogenes and other Listeria species in ready-to-eat food items (pasteurized milk, cheese, ice cream, and cakes) and raw meat products (minced beef, pork, and chicken carcasses). A total of 711 randomly selected samples were collected from supermarkets and pastry shops in Addis Ababa, Ethiopia. Listeria monocytogenes and other Listeria species were isolated and identified according to the techniques recommended by the International Organization for Standardization (ISO 11290-1). Serotyping of L. monocytogenes strains was carried out at the French Food Safety Agency (AFSSA), Ploufragan, France. Of the 711 food samples examined, 189 (26.6%) were Listeria positive of which 34 (4.8%) were L. monocytogenes. Pork was the most contaminated with Listeria species (62.5%) followed by minced beef (47.7%), ice cream (42.7%), soft cheese (16.8%), chicken carcasses (16.0%), and cakes (12.1%). All pasteurized milk and cottage cheese samples examined were Listeria negative. Listeria monocytogenes strains were isolated in ready-to-eat food items consisting of ice cream (11.7%), cakes (6.5%), and soft cheese (3.9%) and in meat products ranging from 3.7% to 5.1%. Among the 34 isolates of L. monocytogenes serotyped, serotypes 4b/4e (n = 32), 4c, and 4e (n = 2) were identified. The presence of L. monocytogenes in some ready-to-eat food items could pose public health hazards to the consumer, particularly to the high-risk group of the population.

Prevalence of Listeria monocytogenes in poultry production in France.

This study aimed to update and create a data set from laying hens and broilers regarding contamination by Listeria monocytogenes. Two hundred laying-hen flocks were sampled, with 88 flocks reared in cages and 112 reared on the floor. One hundred forty-five broiler flocks were sampled, with 85 conventional and 60 free-range flocks. A total of 774 and 725 samples were analyzed from laying hens and broilers, respectively. L. monocytogenes was detected in 31 of 200 flocks, yielding an estimated prevalence of 15.5% in laying-hen flocks. Among positive flocks, there appeared a significant (P = 0.004) difference between caged and floor-reared hens, with a higher detection in dust samples from floor-reared hens. In positive caged hen flocks, significant (P = 0.028) differences between dust and fecal samples appeared, with a higher detection in feces than in dust samples. In broiler flocks, L. monocytogenes was isolated in 46 of 145 flocks, yielding an estimated prevalence of 32% (28% in conventional flocks versus 37% in the free-range flocks). L. monocytogenes was isolated in samples taken from conventional flocks with a lower frequency than in free-range flocks (13 versus 18%, respectively). The serotyping of L. monocytogenes strains showed that the majority belonged to type 1/2a in laying-hen flocks (74.3%) and in broiler flocks (40.5%). A significant difference (P = 0.007) between laying hens and broilers was shown for serogroup 4 and for serovar 1/2b (P = 0.007); these serogroups were more prevalent in broilers (40%) than in laying hens (5.7%).

Listeria monocytogenes contamination of finishing pigs: an exploratory epidemiological survey in France.

Listeria monocytogenes is a foodborne pathogen of major concern for public health in industrialised countries. Since L. monocytogenes carriage by pigs at the herd level could be a primary source for carcass contamination, control measures should be designed to reduce the L. monocytogenes load at the pre-harvest stage. For this purpose, an exploratory analytical survey was carried out in 2000-2001 in 93 French farrow-to-finish pig farms concerning L. monocytogenes contamination in pigs before they left for the slaughterhouse. On each farm, the L. monocytogenes status of a batch of contemporary fattening pigs housed in the same room was assessed on faecal material samples taken by means of gauze swabs wiped on the perianal region of the pigs. Fourteen percent of the batches studied had at least one contaminated sample and were therefore classified as L. monocytogenes contaminated batches. Two logistic regression models were used to assess the association between managerial and hygiene practices and the risk of L. monocytogenes contamination of the batch at the end of the finishing period on the whole data set (n = 93) and in the wet feeding farms only (n = 57). Wet feeding during the fattening period was identified as a risk factor for L. monocytogenes contamination. Risk factors related to the introduction of L. monocytogenes in pig facilities were identified for both the general and wet feeding farm data sets. Poor care paid to hygiene on the farms was found to increase the risk of being infected (boots cleaning, change room presence). When the duration of the empty period prior to the introduction of growing pigs was less than one day in the fattening section, the risk of L. monocytogenes contamination was significantly increased. For wet feeding farms, a distribution pipeline cleaning procedure including disinfection was found to be associated with a higher risk of contamination than no cleaning or a procedure consisting of rinsing with water only.

Ecology of Listeria monocytogenes in the environment of raw poultry meat and raw pork meat processing plants.

The zoonotic Listeria monocytogenes is mainly transmitted to humans by the food-borne route. This bacterium was often found in the environment of food processing plants. Therefore the aims of this study were (i) the identification of environmental factors associated with L. monocytogenes contamination on working and non-working surfaces in poultry or pork processing plants and (ii) the understanding of its survival in such environments. The physicochemical risk profiles showed that a surface in resin or plastic, rather than uneven, with organic residues, with a neutral pH, a low temperature and a high hygrometry was associated with L. monocytogenes contamination.