Salmonella in chicken: current and developing strategies to reduce contamination at farm level.

Salmonella is a human pathogen that frequently infects poultry flocks. Consumption of raw or undercooked contaminated poultry products can induce acute gastroenteritis in humans. Faced with the public health concerns associated with salmonellosis, the European Union has established a European regulation forcing member states to implement control programs aimed at reducing Salmonella prevalence in poultry production, especially at the primary production level. The purpose of the present review article is to summarize the current research and to suggest future developments in the area of Salmonella control in poultry, which may be of value to the industry in the coming years. The review will focus especially on preventive strategies that have been developed and that aim at reducing the incidence of Salmonella colonization in broiler chickens at the farm level. In addition to the usual preventive hygienic measures, other strategies have been investigated, such as feed and drinking water acidification with organic acids and immune strategies based on passive and active immunity. Modification of the diet by changing ingredients and nutrient composition with the intent of reducing a bird's susceptibility to Salmonella infection also has been examined. Because in ovo feeding accelerates small intestine development and enhances epithelial cell function, this approach could be an efficient tool for controlling enteric pathogens. Feed additives such as antibiotics, prebiotics, probiotics, and synbiotics that modify the intestinal microflora are part of another field of investigation, and their success depends on the additive used. Other control methods such as the use of chlorate products and bacteriophages also are under study.

Effects of curing sodium nitrite additive and natural meat fat on growth control of Listeria monocytogenes by the bacteriocin-producing Lactobacillus curvatus strain CWBI-B28.

In realistic model meat systems, the separate and combined effects of fat content and sodium nitrite on the antilisterial activity of the bacteriocin of Lactobacillus curvatus CWBI-B28 were studied. In laboratory fermentations where Listeria monocytogenes was co-cultured at 4 degrees C with bacteriocin-producing CWBI-B28 in lean pork meat (fat content: 13%) without added nitrite, a strong antilisterial effect was observed after one week. The effect was maintained for an additional week, after which a slight and very gradual rebound was observed. Both added nitrite (20 ppm) and a high-fat content (43%) were found to antagonise this antilisterial effect, the Listeria cfu count reached after six weeks being 200 times as high in high-fat meat with added nitrite than in lean meat without nitrite. This antagonism could not be attributed to slower growth of the bacteriocin-producing strain, since CWBI-B28 grew optimally in fat-rich meat with 20 ppm sodium nitrite. Bacteriocin activity was also measured in the samples. The observed activity levels are discussed in relation to the degree of antilisterial protection conferred.

Membrane binding sites for the human blood group H-type 2 determinant, an inducer of laminarinase activity in protoplasts of Rubus fruticosus L.

The human blood-group determinants H-type 1 (α-L-Fuc-(1 → 2)-ß-D-Gal-(1 → 3)ß-D-GlcNAc), or type 2 (α-L-Fuc(1 → 2)-ß-D-Gal(1 → 4)-ß-D-GlcNAc) and their mono- and disaccharidic precursors, have been reported to induce D-glycanase (laminarinase) activity in Rubus cells (Y. Liénart et al. 1990, Plant Science 68, 197-202) and protoplasts (Y. Liénart et al. 1991, Plant Science 77, 41-45). Using immunoadsorbent H-type 1 as a matrix for the affinity purification of membrane proteins, and the H-type 2 trisaccharide neoglycoprotein as ligand in kinetic-dependent enzyme-linked-immunosorbent assay for measuring binding, we were able to show that Rubus microsomes contain high-affinity binding sites for the laminarinase inducers. The N-acetyl glucosamine (GlcNAc) eluate was found to contain a saturable, high affinity binding activity for GlcNAc, compatible with the presence of a single class of binding sites Kd = 2 nM, Bmax = 400 pmol · (mg protein)(-1). In contrast, the Scatchard plot of proteins in the lactose eluate was nonlinear. In competition studies, the precursors of H-type 1 (GlcNAc-OCH3, ß-D-Gal-(1 → 3)-ß-D-GlcNAc-OCH3) or of H-type 2 (GlcNAc, N-acetyl lactosamine) trisaccharides inhibited the binding of the proteins in the GlcNAc eluate by H-type 2 neoglycoprotein with respective IC50 values of 0.6, 0.6 or 2, 0.4 nM. These data, and the binding of the H-type 2 trisaccharide by a protein of Mr 260 kDa in a ligand-blot process, are indicative of the general properties exhibited by receptors.