  Belgian surveillance plans to assess changes in Salmonella prevalence in meat at different production stages; ; et al in Journal of Food Protection (2005), 68(11), 160-168 From 1997 to 1999, the prevalence of Salmonella was assessed at different stages through the pork, poultry, and beef meat production chains. Different dilutions of the initial sample suspension were ... [more ▼] From 1997 to 1999, the prevalence of Salmonella was assessed at different stages through the pork, poultry, and beef meat production chains. Different dilutions of the initial sample suspension were analyzed to provide a semiquantitative evaluation of Salmonella contamination and to determine the most representative dilution necessary to detect a reduction in prevalence. An average of 300 samples for each type of meat were analyzed. According to Fisher's exact test, the dilution to be used to detect a reduction in prevalence was chosen based on an initial prevalence of 20 to 26%. Based on this introductory study, a new sampling plan representative of the nationwide Belgian meat production process was used from 2000 through to 2003. This study confirmed the consistently high rate and level of contamination of poultry meat: broiler and layer carcasses were the most contaminated samples followed by broiler fillets and poultry meat preparations. A constant and significant decrease in Salmonella prevalence was observed for pork carcasses, trimmings, and minced meat and for beef minced meat. Less than 3% of beef carcasses and trimming samples were positive for Salmonella. The Belgian plan, as utilized from 2000 to 2003, was suitable for monitoring of zoonoses because the sampling plan was representative of nationwide production processes, covered all periods of the year, and was executed by trained samplers and the analyses were carried out by recognized laboratories using an identical analytical method. [less ▲] Detailed reference viewed: 49 (7 ULg)Plasmids for heavy metal resistance in Alcaligenes eutrophus CH34: Mechanisms and applications; ; et al in FEMS Microbiology Reviews (1994), 14 Alcaligenes eutrophus CH34 is the main representative of a group of strongly related strains (mostly facultative chemolithotrophs) that are well adapted to environments containing high levels of heavy ... [more ▼] Alcaligenes eutrophus CH34 is the main representative of a group of strongly related strains (mostly facultative chemolithotrophs) that are well adapted to environments containing high levels of heavy metals. It harbors the megaplasmids pMOL28 and pMOL30 which carry resistance determinants to Co2+, Ni2+, CrO42-, Hg2+, Tl+, Cd2+, Cu2+ and Zn2+. Among the best characterized determinants are the cnr operon (resistance to Co, Ni) an pMOL28 and the czc operon on pMOL30 (resistance to Co, Cd and Zn). Although the two systems reveal a significant degree of amino acid similarity in the structural genes, the regulation of the operons is different. The resistance mechanism in both cases is based on efflux. The efflux mechanism leads to a pH increase outside of the cytoplasmic membrane. Metals are sequestered from the external medium through the bioprecipitation of metal carbonates formed in the saturated zone around the cell. This latter phenomenon can be exploited in bioreactors designed to remove metals from effluents. The bacteria are immobilized on composite membranes in a continuous tubular membrane reactor (CTMR). The effluent continuously circulates through the intertubular space, while the external surface of the tubes is in contact with the growth medium. Metal crystals are eventually removed by the effluent stream and collected on a glass bead column. The system has been applied to effluents containing Cd, Zn, Co, Ni and Cu. By introducing catabolic plasmids involved in the aerobic degradation of PCBs and 2,4-D into metal-resistant A. eutrophus strains, the application range was widened to include effluents polluted with both organic and inorganic substances. Biosensors have been developed which are based on the fusion of genes induced by metals to a reporter system, the lux operon of Vibrio fischeri. Bacterial luciferases produce light through the oxidation of fatty aldehydes. The gene fusions are useful both for the study of regulatory genes and for the determination of heavy metal concentrations in the environment. [less ▲] Detailed reference viewed: 13 (1 ULg) |
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