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Background: Enzyme-linked immunosorbent assays (ELISAs) are the most widely used diagnostic tools in bovine paratuberculosis (bPTB) control. However, their diagnostic accuracy may be compromised by bovine tuberculosis (bTB) infection, as both diseases share diagnostic targets., Methods: The bPTB and bTB infection status of 228 animals was determined using microbiological tissue culture as a reference test. The diagnostic performance (sensitivity, specificity, likelihood ratios and predictive values) of the bPTB-ELISA on blood serum samples, taking into account the bPTB animal-level prevalence of the area and the bTB status of the animals, was evaluated., Results: A sensitivity of 40.7% (95% confidence interval [CI]: 27.5%-53.9%) and a specificity of 94.7% (95% CI: 91.4%-98.0%) were obtained for bPTB-ELISA in all animals. A bPTB-ELISA-positive animal would have a post-test probability of 70% or more of being infected in areas with a bPTB prevalence of 23% or more. A negative bPTB-ELISA result, in areas with a bPTB prevalence of 41% or less, would rule out the disease with more than 70% certainty. In bTB-positive animals, sensitivity increased (94.4% [95% CI: 81.4%-100%] vs. 25.1% [95% CI: 11.8%-38.4%]) and specificity decreased (82.6% [95% CI: 71.8%-93.4%] vs. 99.4% [95% CI: 98.0%-99.9%]). The bPTB-ELISA is a good tool to rule out bPTB co-infection in bTB-positive animals, while in bTB-negative animals, it allows confirmation of disease with more than 70% probability if disease prevalence is 6% or more., Limitations: The observed differences could be enhanced by the effect of frequent application of the intradermal tuberculin test, which was unknown in the animals studied., Conclusions: These results provide useful guidance for the application and interpretation of ELISA as a tool for bPTB disease control., (© 2023 British Veterinary Association.)

Background: Listeria monocytogenes is a foodborne bacterial pathogen that causes listeriosis, an infectious disease in animals and people, with pigs acting as asymptomatic reservoirs. In August 2019 an outbreak associated with the consumption of pork meat caused 222 human cases of listeriosis in Spain. Determining the diversity as well as the virulence potential of strains from pigs is important to public health., Methods: The behaviour of 23 L monocytogenes strains recovered from pig tonsils, meat and skin was compared by studying (1) internalin A, internalin B, listeriolysin O, actin assembly-inducing protein and PrfA expression levels, and (2) their invasion and intracellular growth in eukaryotic cells., Results: Marked differences were found in the expression of the selected virulence factors and the invasion and intracellular replication phenotypes of L monocytogenes strains. Strains obtained from meat samples and belonging to serotype 1/2a did not have internalin A anchored to the peptidoglycan. Some strains expressed higher levels of the studied virulence factors and invaded and replicated intracellularly more efficiently than an epidemic L monocytogenes reference strain (F2365)., Conclusion: This study demonstrates the presence of virulent L monocytogenes strains with virulent potential in pigs, with valuable implications in veterinary medicine and food safety., Competing Interests: Competing interests: None declared., (© British Veterinary Association 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Pigs are asymptomatic carriers of foodborne bacteria, such as Salmonella enterica and Campylobacter species, which can pose a risk to human health. New strategies to control bacteria burden before reaching the slaughterhouse are necessary. This study evaluated the effect of Pediococcus acidilactici on performance parameters and on the burden of foodborne pathogens, that have subsequent implications on food quality and safety, in free-range finishing pigs at the slaughterhouse., Methods: Pigs were randomly allocated and blocked by weight into control group (control diet) and treated group (control diet supplemented with P acidilactici ) 31 days before slaughter. Weight and average daily gain were recorded and changes in faecal microbiota were determined at the beginning and at the end of the study., Results: No changes were observed in performance parameters. No statistically significant differences were observed when comparing between treated and control animals at the beginning or at the end of the study. However, a significant decrease was detected in the counts of Campylobacter species in treated animals between day 0 and day 31 (4.86-3.40 log colony-forming units/g; P=0.002)., Conclusion: This study indicates that supplementation with P acidilactici represents a useful approach to control Campylobacter species load in free-range finishing pigs before slaughter., Competing Interests: Competing interests: None declared., (© British Veterinary Association 2020. No commercial re-use. See rights and permissions. Published by BMJ.)