Genotyping of important medical or veterinary prokaryotes has become a very important tool during the last decades. Rapid development of fragment-separation and sequencing technologies has made many new genotyping strategies possible. Among these new methods is multilocus variable-number tandem repeat analysis (MLVA). Here we present an update on the use of MLVA in eight European countries (Denmark, France, Germany, Ireland, Italy, the Netherlands, Norway and Sweden). Researchers in Europe have been active in developing and implementing a large array of different assays. MLVA has been used as a typing tool in several contexts, from aiding in resolving outbreaks of food-borne bacteria to typing organisms that may pose a bioterrorist threat, as well as in scientific studies.

Background: Most publicly available genomes of Salmonella enterica are from human disease in the US and the UK, or from domesticated animals in the US. Methods: Here we describe a historical collection of 10,000 strains isolated between 1891-2010 in 73 different countries. They encompass a broad range of sources, ranging from rivers through reptiles to the diversity of all S. enterica isolated on the island of Ireland between 2000 and 2005. Genomic DNA was isolated, and sequenced by Illumina short read sequencing. Results: The short reads are publicly available in the Short Reads Archive. They were also uploaded to EnteroBase, which assembled and annotated draft genomes. 9769 draft genomes which passed quality control were genotyped with multiple levels of multilocus sequence typing, and used to predict serovars. Genomes were assigned to hierarchical clusters on the basis of numbers of pair-wise allelic differences in core genes, which were mapped to genetic Lineages within phylogenetic trees. Conclusions: The University of Warwick/University College Cork (UoWUCC) project greatly extends the geographic sources, dates and core genomic diversity of publicly available S. enterica genomes. We illustrate these features by an overview of core genomic Lineages within 33,000 publicly available Salmonella genomes whose strains were isolated before 2011. We also present detailed examinations of HC400, HC900 and HC2000 hierarchical clusters within exemplar Lineages, including serovars Typhimurium, Enteritidis and Mbandaka. These analyses confirm the polyphyletic nature of multiple serovars while showing that discrete clusters with geographical specificity can be reliably recognized by hierarchical clustering approaches. The results also demonstrate that the genomes sequenced here provide an important counterbalance to the sampling bias which is so dominant in current genomic sequencing.

Salmonella Typhimurium is the predominant serotype isolated from humans in Europe. Pork and pork products are recognized vehicles of Salmonella and are responsible for outbreaks of human salmonellosis. Pigs can become infected with Salmonella on the breeding or fattening farm and during transport, lairage, and slaughter. The aim of this study was to investigate selected points of Salmonella contamination from the time pigs entered the lairage to the time the carcass was processed in the boning hall and to determine the importance of different sources of Salmonella along the Irish pork production chain. A second objective was to evaluate whether the serological status or category of a herd influenced the levels of bacteriological contamination detected on individual carcasses and pork cuts during slaughter and dressing operations. All samples were tested for the presence and numbers of Salmonella. Enterobacteriaceae numbers were also determined. Serotype, phage type, and pulsed-field gel electrophoresis were utilized to determine similarity among Salmonella isolates. Lairage was a major source of cross-contamination with Salmonella as were the hands of evisceration operatives, conveyor belts, and equipment in the boning hall. Cross-contamination within the slaughter plant environment accounted for up to 69 % of Salmonella carcass contamination. In general, herd category reflected the bacteriological status of carcasses and pork cuts. Major findings were a strong association (P < 0.01) between Enterobacteriaceae counts and Salmonella occurrence on prechill carcasses and a significant association (P < 0.05) between Enterobacteriaceae counts and Salmonella occurrence on pork cut samples.

Due to concerns about a link between variant Creutzfeldt-Jakob disease in humans and similar prion protein-induced disease in cattle, i.e., bovine spongiform encephalopathy (BSE), strict controls are in place to exclude BSE-positive animals and/or specified risk materials including bovine central nervous system (CNS) tissue from the human food chain. However, current slaughter practice, using captive bolt guns, may induce disruption of brain tissues and mobilize CNS tissues into the bovine circulatory system, leading to the dispersion of CNS tissues (including prion proteins) throughout the derived carcass. This project used a marker (antibiotic-resistant) strain of Pseudomonas fluorescens to model the effects of commercial captive bolt stunning procedures on the movement of mobilized CNS material within slaughtered animals and the abattoir environment. The marker organism, introduced by injection through the bolt entry aperture or directly using a cartridge-fired captive bolt, was detected in the slaughter environment immediately after stunning and in the abattoir environment at each subsequent stage of the slaughter-dressing process. The marker organism was also detected on the hands of operatives; on slaughter equipment; and in samples of blood, organs, and musculature of inoculated animals. There were no significant differences between the results obtained by the two inoculation methods (P < 0.05). This study demonstrates that material present in, or introduced into, the CNS of cattle during commercial captive bolt stunning may become widely dispersed across the many animate and inanimate elements of the slaughter-dressing environment and within derived carcasses including meat entering the human food chain.

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This risk assessment study aimed to estimate the prevalence of Salmonella on pig carcasses and pork joints produced in slaughterhouses, on the basis that within groups of slaughter there is a strong association between the proportion of Salmonella-positive animals entering the slaughter lines (x) and the resulting proportion of contaminated eviscerated pig carcasses (y). To this effect, the results of a number of published studies reporting estimates of x and y were assembled in order to model a stochastic weighted regression considering the sensitivities of the diverse Salmonella culture methods. Meta-analysis was used to assign weights to the regression and to estimate the overall effect of chilling on Salmonella incidence on pig carcasses. The model's ability to produce accurate estimates and the intrinsic effectiveness of the modeling capabilities of meta-analysis were appraised using Irish data for the input parameter of prevalence of Salmonella carrier slaughter pigs. The model approximated a Salmonella prevalence in pork joints from Irish boning halls of 4.0% (95% confidence interval, 0.3 to 12.0%) and was validated by the results of a large survey (n = 720) of Salmonella in pork joints (mean, 3.3%; 95% confidence interval, 2.0 to 4.6%) carried out in four commercial pork abattoirs as part of this research project. Sensitivity analysis reinforced the importance of final rinsing (r = -0.382) and chilling (r = -0.221) as stages that contribute to reducing considerably the occurrence of Salmonella on the final product, while hygiene practices during jointing seemed to moderate only marginally the amount of contaminated pork joints. Finally, the adequacy of meta-analysis for integrating different findings and producing distributions for use in stochastic modeling was demonstrated.