Prevalence and risk factors for bacterial food-borne zoonotic hazards in slaughter pigs: a review

Listeria monocytogenes prevalence and genomic diversity along the pig and pork production chain

The facultative intracellular bacterium Listeria monocytogenes (L. monocytogenes) is the causative agent of listeriosis, a severe invasive illness. This ubiquitous species is widely distributed in the environment, but infection occurs almost exclusively through ingestion of contaminated food. The pork production sector has been heavily affected by a series of L. monocytogenes-related foodborne outbreaks in the past around the world. Ready-to-eat (RTE) pork products represent one of the main food sources for strong-evidence listeriosis outbreaks. This pathogen is known to be present throughout the entire pig and pork production chain. Some studies hypothesized that the main source of contamination in final pork products was either living pigs or the food-processing environment. A detailed genomic picture of L. monocytogenes can provide a renewed understanding of the routes of contamination from pig farms to the final products. This review provides an overview of the prevalence, the genomic diversity and the genetic background linked to virulence of L. monocytogenes along the entire pig and pork production chain, from farm to fork.

Impact of In-Feed versus In-Water Chlortetracycline and Tiamulin Administrations on Fecal Prevalence and Antimicrobial Susceptibilities of Campylobacter in a Population of Nursery Pigs

Antimicrobial resistance (AMR) in bacteria is a major public health concern in the US and around the world. Campylobacter is an important foodborne pathogen that resides in the gut of pigs and is shed in feces, with the potential to be transmitted to humans. In pigs, the oral route, either in-feed or in-water, is by far the most common route of administration of antimicrobials. Because the distribution of the antibiotic in the gut and the dosages are different, the impact of in-feed vs. in-water administration of antibiotics on the development of AMR is likely to be different. Therefore, a study was conducted to compare in-feed vs. in-water administrations of chlortetracycline (CTC) and/or tiamulin on fecal prevalence and AMR profiles of Campylobacter among weaned nursery piglets. A total of 1,296 weaned piglets, allocated into 48 pens (27 piglets per pen), were assigned randomly to six treatment groups: Control (no antibiotic), in-feed CTC, in-water CTC, in-feed tiamulin, in-water tiamulin, or in-feed CTC and tiamulin. Fecal samples were collected randomly from 5 piglets from each pen during the pre-treatment (days 0, 7), treatment (days 14, 21), and post-treatment (days 28, 35) phases. Bacterial isolations and species identifications were conducted by culture and PCR, respectively. The microbroth dilution method with SensititreTM plates was used to determine the antimicrobial susceptibility and resistance of Campylobacter isolates. The results on resistance were interpreted based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) epidemiological cutoff values for Campylobacter. The overall prevalence of Campylobacter was 18.2% (262/1440). Speciation of Campylobacter isolates by PCR indicated the prevalence of only two species: Campylobacter hyointestinalis (17.9%; 258/1440) and C. coli (0.3%; 4/1440). Campylobacter isolates were resistant to tetracycline (98.5%), ciprofloxacin (89.3%), and nalidixic acid (60.3%). Neither the antibiotic nor the route of administration had an effect (p > 0.05) on the prevalence of AMR Campylobacter in the feces of piglets.

Identification of intestinal and fecal microbial biomarkers using a porcine social stress model

Understanding the relationships between social stress and the gastrointestinal microbiota, and how they influence host health and performance is expected to have many scientific and commercial implementations in different species, including identification and improvement of challenges to animal welfare and health. In particular, the study of the stress impact on the gastrointestinal microbiota of pigs may be of interest as a model for human health. A porcine stress model based on repeated regrouping and reduced space allowance during the last 4 weeks of the finishing period was developed to identify stress-induced changes in the gut microbiome composition. The application of the porcine stress model resulted in a significant increase in salivary cortisol concentration over the course of the trial and decreased growth performance and appetite. The applied social stress resulted in 32 bacteria being either enriched (13) or depleted (19) in the intestine and feces. Fecal samples showed a greater number of microbial genera influenced by stress than caecum or colon samples. Our trial revealed that the opportunistic pathogens Treponema and Clostridium were enriched in colonic and fecal samples from stressed pigs. Additionally, genera such as Streptococcus, Parabacteroides, Desulfovibrio, Terrisporobacter, Marvinbryantia, and Romboutsia were found to be enriched in response to social stress. In contrast, the genera Prevotella, Faecalibacterium, Butyricicoccus, Dialister, Alloprevotella, Megasphaera, and Mitsuokella were depleted. These depleted bacteria are of great interest because they synthesize metabolites [e.g., short-chain fatty acids (SCFA), in particular, butyrate] showing beneficial health benefits due to inhibitory effects on pathogenic bacteria in different animal species. Of particular interest are Dialister and Faecalibacterium, as their depletion was identified in a human study to be associated with inferior quality of life and depression. We also revealed that some pigs were more susceptible to pathogens as indicated by large enrichments of opportunistic pathogens of Clostridium, Treponema, Streptococcus and Campylobacter. Generally, our results provide further evidence for the microbiota-gut-brain axis as indicated by an increase in cortisol concentration due to social stress regulated by the hypothalamic-pituitary-adrenal axis, and a change in microbiota composition, particularly of bacteria known to be associated with pathogenicity and mental health diseases.

Salmonella Infection in Pigs: Disease, Prevalence, and a Link between Swine and Human Health

Salmonella is one of the most spread foodborne pathogens worldwide, and Salmonella infections in humans still represent a global health burden. The main source of Salmonella infections in humans is represented by contaminated animal-derived foodstuffs, with pork products being one of the most important players. Salmonella infection in swine is critical not only because it is one of the main causes of economic losses in the pork industry, but also because pigs can be infected by several Salmonella serovars, potentially contaminating the pig meat production chain and thus posing a significant threat to public health globally. As of now, in Europe and in the United States, swine-related Salmonella serovars, e.g., Salmonella Typhimurium and its monophasic variant Salmonella enterica subsp. enterica 1,4,[5],12:i:-, are also frequently associated with human salmonellosis cases. Moreover, multiple outbreaks have been reported in the last few decades which were triggered by the consumption of Salmonella-contaminated pig meat. Throughout the years, changes and evolution across the pork industry may have acted as triggers for new issues and obstacles hindering Salmonella control along the food chain. Gathered evidence reinforces the importance of coordinating control measures and harmonizing monitoring programs for the efficient control of Salmonella in swine. This is necessary in order to manage outbreaks of clinical disease in pigs and also to protect pork consumers by controlling Salmonella subclinical carriage and shedding. This review provides an update on Salmonella infection in pigs, with insights on Salmonella ecology, focusing mainly on Salmonella Choleraesuis, S. Typhimurium, and S. 1,4,[5],12:i:-, and their correlation to human salmonellosis cases. An update on surveillance methods for epidemiological purposes of Salmonella infection in pigs and humans, in a "One Health" approach, will also be reported.

Comparative Analysis of Campylobacter jejuni and C. coli Isolated from Livestock Animals to C. jejuni and C. coli Isolated from Surface Water Using DNA Sequencing and MALDI-TOF

This study evaluated the contribution of cattle, sheep, poultry and pigs to the contamination of surface water from rivers by Campylobacter jejuni and C. coli using MLST, cgMLST and considered MALDI-TOF MS as an alternative technique. The 263 strains isolated from cattle (n = 61), sheep (n = 42), poultry (n = 65), pigs (n = 60) and surface water (n = 35) were distributed across 115 sequence types (STs), 49 for C. jejuni and 66 for C. coli. Considering MLST data, 14.2%, 11.4% and 2.8% of the surface water strains could be attributed to cattle, poultry and sheep, respectively, none to pigs, and 85.7% were non-attributed. Analysis of cg-MLST data with STRUCTURE indicated that C. jejuni strains from water were predominantly attributed to poultry (93.5%), weakly to sheep (<1%) and 6.3% non-attributed, and that conversely, C. coli strains from water were predominantly non-attributed (94.3%) and 5.7% attributed to poultry. Considering the protein profiles with a threshold of 94% and 97% of similarity, respectively, strains from surface water could be attributed to poultry (31.4% and 17.1%), and to cattle (17.1% and 5.7%); 54.1% and 77.1% were non-attributed. This study confirmed these livestock animals might contribute to the contamination of surface water, with a level of contribution depending on the typing technique and the method of analysis. MALDI-TOF could potentially be an alternative approach for source attribution.

Public health implications of Yersinia enterocolitica investigation: an ecological modeling and molecular epidemiology study

BACKGROUND

Yersinia enterocolitica has been sporadically recovered from animals, foods, and human clinical samples in various regions of Ningxia, China. However, the ecological and molecular characteristics of Y. enterocolitica, as well as public health concerns about infection in the Ningxia Hui Autonomous Region, remain unclear. This study aims to analyze the ecological and molecular epidemiological characteristics of Y. enterocolitis in order to inform the public health intervention strategies for the contains of related diseases.

METHODS

A total of 270 samples were collected for isolation [animals (n = 208), food (n = 49), and patients (n = 13)], then suspect colonies were isolated and identified by the API20E biochemical identification system, serological tests, biotyping tests, and 16S rRNA-PCR. Then, we used an ecological epidemiological approach combined with machine learning algorithms (general linear model, random forest model, and eXtreme Gradient Boosting) to explore the associations between ecological factors and the pathogenicity of Y. enterocolitis. Furthermore, average nucleotide identity (ANI) estimation, single nucleotide polymorphism (SNP), and core gene multilocus sequence typing (cgMLST) were applied to characterize the molecular profile of isolates based on whole genome sequencing. The statistical test used single-factor analysis, Chi-square tests, t-tests/ANOVA-tests, Wilcoxon rank-sum tests, and Kruskal-Wallis tests.

RESULTS

A total of 270 isolates of Yersinia were identified from poultry and livestock (n = 191), food (n = 49), diarrhoea patients (n = 13), rats (n = 15), and hamsters (n = 2). The detection rates of samples from different hosts were statistically different (χ² = 22.636, P < 0.001). According to the relatedness clustering results, 270 isolates were divided into 12 species, and Y. enterocolitica (n = 187) is a predominated species. Pathogenic isolates made up 52.4% (98/187), while non-pathogenic isolates made up 47.6% (89/187). Temperature and precipitation were strongly associated with the pathogenicity of the isolates (P < 0.001). The random forest (RF) prediction model showed the best performance. The prediction result shows a high risk of pathogenicity Y. enterocolitica was located in the northern, northwestern, and southern of the Ningxia Hui Autonomous Region. The Y. enterocolitica isolates were classified into 54 sequence types (STs) and 125 cgMLST types (CTs), with 4/O:3 being the dominant bioserotype in Ningxia. The dominant STs and dominant CTs of pathogenic isolates in Ningxia were ST429 and HC100_2571, respectively.

CONCLUSIONS

The data indicated geographical variations in the distribution of STs and CTs of Y. enterocolitica isolates in Ningxia. Our work offered the first evidence that the pathogenicity of isolates was directly related to fluctuations in temperature and precipitation of the environment. CgMLST typing strategies showed that the isolates were transmitted to the population via pigs and food. Therefore, strengthening health surveillance on pig farms in high-risk areas and focusing on testing food of pig origin are optional strategies to prevent disease outbreaks.

Selection of commercial protective cultures to be added in Sardinian fermented sausage to control Listeria monocytogenes

Sardinian fermented sausage "Salsiccia Sarda" is a Mediterranean-style, semi-dry, fermented, RTE product, representing the main pork meat product in Sardinia (Italy). The high variability that characterizes the technological processes applied in different production plants results in sausages with different chemico-physical features sometimes permissive for the growth of Listeria monocytogenes. In order to guarantee the hygienic-sanitary quality of the final product and to innovate the manufacturing process, the main objective of this study was to evaluate the use of different commercial protective cultures to control L. monocytogenes growth in the Sardinian fermented sausage. In the first step, in vitro tests were carried out to evaluate the effectiveness of five freeze-dried bioprotective cultures availabe on the market in limiting the growth of L. monocytogenes. The two protective cultures that showed the best in vitro results were selected for a challenge test on artificially contaminated Sardinian fermented sausages. Moreover, the protective culture that showed the best results in inhibiting the growth of L. monocytogenes according to in vitro and challenge test experiments, was included into real production settings and validated in three producing plants. As a result, it was observed that protective cultures represent an important technological innovation for the Sardinian fermented sausage processing plants as they allow to control L. monocytogenes growth without altering the composition, the microflora and the chemical-physical characteristics of the product, thus ensuring safety and quality. Protective cultures also showed to reduce Enterobacteriaceae mean levels at the end of ripening and not to affect the natural concentration of lactic acid bacteria and coagulase-negative staphylococci.

Dynamics of Microbial Shedding in Market Pigs during Fasting and the Influence of Alginate Hydrogel Bead Supplementation during Transportation

The shedding of foodborne pathogenic bacteria by food-animals can be affected by multiple factors, such as animal health, diet, stress, and environmental conditions. The practices that come with transport involve fasting, handling, mixing with unfamiliar pigs, and fluctuating temperatures. These practices, especially fasting and transport, can increase the microbial load in the feces of animals. The use of alginate hydrogels is a novel delivery system that can be a potential food safety intervention during transport to induce satiety and provide electrolytes to the animal’s system. This study sought to observe microbial shedding as affected by fasting and hydrogel bead supplementation during transport. Sixty market pigs were subjected to a 12 h fasting period and an additional 4 h transport period, in which a treatment group was fed hydrogel beads and a control group was not. Sampling points were before fast (BF), before transport (BT), and after transport (AT). Fecal samples were collected from every animal at each sampling point. Results from this study showed a significant increase in the concentrations of both Enterobacteriaceae and Escherichia coli between the before fast (BF) and after transport (AT) sampling points. However, no difference (p > 0.05) was found between the treatment (hydrogel) and control (no hydrogel) during transport. Moreover, no significant difference was found in the prevalence of Salmonella and E. coli O157:H7 at the three different sampling points, or between the treatment and control groups.

Effect of Supplementing Seaweed Extracts to Pigs until d35 Post-Weaning on Performance and Aspects of Intestinal Health

The objective of this study was to examine the effects of feeding laminarin (LAM) and fucoidan (FUC) enriched seaweed extracts up to d35 post-weaning on measures of animal performance, intestinal microbial and transcriptome profiles. 75 pigs were assigned to one of three groups: (1) basal diet; (2) basal diet + 250 ppm fucoidan; (3) basal diet + 300 ppm laminarin with 7 replicates per treatment group. Measures of performance were collected weekly and animals sacrificed on d35 post-weaning for the sampling of gastrointestinal tissue and digesta. Animal performance was similar between the basal group and the groups supplemented with FUC and LAM (P > 0.05). Pigs fed the basal diet had higher alpha diversity compared to both the LAM and FUC supplemented pigs (P < 0.05). Supplementation with LAM and FUC increased the production of butyric acid compared to basal fed pigs (P < 0.05). At genus level pigs fed the LAM supplemented diet had the greatest abundance of Faecalbacterium, Roseburia and the lowest Campylobacter of the three experimental treatments (P< 0.05). While neither extract had beneficial effects on animal performance, LAM supplementation had a positive influence on intestinal health through alterations in the gastrointestinal microbiome and increased butyrate production.

Assessing Environmental Factors within the One Health Approach

Background: One Health is a comprehensive and multisectoral approach to assess and examine the health of animals, humans and the environment. However, while the One Health approach gains increasing momentum, its practical application meets hindrances. This paper investigates the environmental pillar of the One Health approach, using two case studies to highlight the integration of environmental considerations. The first case study pertains to the Danish monitoring and surveillance programme for antimicrobial resistance, DANMAP. The second case illustrates the occurrence of aflatoxin M1 (AFM1) in milk in dairy-producing ruminants in Italian regions. Method: A scientific literature search was conducted in PubMed and Web of Science to locate articles informing the two cases. Grey literature was gathered to describe the cases as well as their contexts. Results: 19 articles and 10 reports were reviewed and informed the two cases. The cases show how the environmental component influences the apparent impacts for human and animal health. The DANMAP highlights the two approaches One Health and farm to fork. The literature provides information on the comprehensiveness of the DANMAP, but highlights some shortcomings in terms of environmental considerations. The AFM1 case, the milk metabolite of the carcinogenic mycotoxin aflatoxin B1, shows that dairy products are heavily impacted by changes of the climate as well as by economic drivers. Conclusions: The two cases show that environmental conditions directly influence the onset and diffusion of hazardous factors. Climate change, treatment of soils, water and standards in slaughterhouses as well as farms can have a great impact on the health of animals, humans and the environment. Hence, it is important to include environmental considerations, for example, via engaging environmental experts and sharing data. Further case studies will help to better define the roles of environment in One Health scenarios.

Genetic Diversity and Distribution of Virulence-Associated Genes in Y. enterocolitica and Y. enterocolitica-Like Isolates from Humans and Animals in Poland

Yersinia enterocolitica, widespread within domestic and wild-living animals, is a foodborne pathogen causing yersiniosis. The goal of this study was to assess a genetic similarity of Y. enterocolitica and Y. enterocolitica-like strains isolated from different hosts using Multiple Locus Variable-Number Tandem Repeat Analysis (MLVA) and Pulsed-Field Gel Electrophoresis (PFGE) methods, and analyze the prevalence of virulence genes using multiplex-Polymerase Chain Reaction (PCR) assays. Among 51 Yersinia sp. strains 20 virulotypes were determined. The most common virulence genes were ymoA, ureC, inv, myfA, and yst. Yersinia sp. strains had genes which may contribute to the bacterial invasion and colonization of the intestines as well as survival in serum. One wild boar Y. enterocolitica 1A strain possessed ail gene implying the possible pathogenicity of 1A biotype. Wild boar strains, represented mainly by 1A biotype, were not classified into the predominant Variable-Number Tandem Repeats (VNTR)/PFGE profile and virulotype. There was a clustering tendency among VNTR/PFGE profiles of pig origin, 4/O:3, and virulence profile. Pig and human strains formed the most related group, characterized by ~80% of genetic similarity what suggest the role of pigs as a potential source of infection for the pork consumers.

Critical Analysis of Pork QMRA Focusing on Slaughterhouses: Lessons from the Past and Future Trends

Foodborne microbial diseases have a significant impact on public health, leading to millions of human illnesses each year worldwide. Pork is one of the most consumed meat in Europe but may also be a major source of pathogens introduced all along the farm-to-fork chain. Several quantitative microbial risk assessment (QMRA) have been developed to assess human health risks associated with pork consumption and to evaluate the efficiency of different risk reduction strategies. The present critical analysis aims to review pork QMRA. An exhaustive search was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology. It resulted in identification of a collection of 2489 papers including 42 on QMRA, after screening. Among them, a total of 29 studies focused on Salmonella spp. with clear concern on impacts at the slaughterhouse, modeling the spreading of contaminations and growth at critical stages along with potential reductions. Along with strict compliance with good hygiene practices, several potential risk mitigation pathways were highlighted for each slaughterhouse step. The slaughterhouse has a key role to play to ensure food safety of pork-based products but consideration of the whole farm-to-fork chain is necessary to enable better control of bacteria. This review provides an analysis of pork meat QMRA, to facilitate their reuse, and identify gaps to guide future research activities.

Prevalence of Campylobacter spp. in a poultry and pork processing plants

The study aimed to investigate the prevalence of Campylobacter spp. in different stages of poultry and pork processing in the Central region of Russia. A total of 47 Campylobacter isolates were obtained from 107 samples from poultry processing plants (40.2%): 87.2% were identified as Campylobacter jejuni, whereas 12.8% were identified as Campylobacter coli. The prevalence of Campylobacter was significantly (p <0.05) higher after evisceration in the poultry processing plant. Campylobacter spp.was detected in 62.7% of the equipment and environmental samples. From positive samples of Campylobacter spp., 84.3% of Campylobacter jejuni and 15.7% Campylobacter coli were observed. A total of nine Campylobacter isolates were obtained from 116 samples from pork processing plants (7.8%): 33.3% of them were identified as Campylobacter jejuni whereas 66.7% were identified as Campylobacter coli. Splitting and evisceration were also critical in Campylobacter contamination. Almost all pork carcasses were Campylobacter positive, and all of them were identified as Campylobacter coli. The prevalence of positive Campylobacter samples in poultry processing plants was significantly (p < 0.05) higher than in pork processing plants.

Occurrence, distribution and diversity of Listeria monocytogenes contamination on beef and pig carcasses after slaughter

In this study we investigated the prevalence and location of Listeria monocytogenes and hygiene indicator bacteria on beef and pig carcasses. Carcasses were sampled after slaughter and before cooling at eight and nine sites on the carcass, respectively. For each sample, detection and enumeration of Listeria was performed, as well as the enumeration of Total Aerobic Counts (TAC) and Enterobacteriaceae. The L. monocytogenes isolates were also typed to determine pulsotypes and clonal complexes (CC). L. monocytogenes was detected on 46% [95% CI: 35-56%] of beef and 22% [95% CI: 11-32%] of pig carcasses. Contamination levels at the different carcass sites differed considerably between beef and pigs. Genetic typing of strains suggests that carcass contamination originates from both incoming animals with transmission during slaughter practices as well as persistent (CC9) contamination from the slaughterhouse environment. These findings can be used to understand the complexity of introduction and persistence of this pathogen in slaughter facilities. Accurate correlation of L. monocytogenes presence proved unfeasible with any of the tested hygiene indicator bacteria.

Antimicrobial Resistance and Virulence Properties of Campylobacter Spp. Originating from Domestic Geese in Poland

A total of 240 samples were evaluated for the presence of Campylobacter spp. Campylobacter was found in 83.3% of the cecum contents samples and 52.5% of the neck skin samples from carcasses. The prevailing species was C. jejuni, accounting for 87.7% of all Campylobacter isolates, and the remaining 12.3% of isolates were C. coli. All Campylobacter isolates, independent of the sample origin and species, were positive for 6 out of 15 tested genes (flaA, flhA, cadF, racR, ciaB, and cdtA genes). The prevalence of dnaJ, docA, pldA, cdtB, cdtC, and iam genes was also very common (ranging from 86.5% to 98.8%). The lowest prevalence was noted for virB11 and wlaN genes, both in Campylobacter isolates from cecum (12% and 19%) and carcasses (11.1% and 17.5%). None of the isolates tested, regardless of the sample origin, carried the cgtB gene. The highest resistance rates were observed for quinolones (90.8%) and tetracyclines (79.8%). Simultaneously, only single Campylobacter isolate was resistant to macrolides (0.6%) and none of the isolates showed resistance to aminoglycosides and amphenicols. The common presence of Campylobacter on geese carcasses as well as the detection of multidrug-resistant isolates indicate that consuming goose meat might cause a potential risk, therefore leading to human campylobacteriosis.

Interventions Targeting Deep Tissue Lymph Nodes May Not Effectively Reduce the Risk of Salmonellosis from Ground Pork Consumption: A Quantitative Microbial Risk Assessment

The inclusion of deep tissue lymph nodes (DTLNs) or nonvisceral lymph nodes contaminated with Salmonella in wholesale fresh ground pork (WFGP) production may pose risks to public health. To assess the relative contribution of DTLNs to human salmonellosis occurrence associated with ground pork consumption and to investigate potential critical control points in the slaughter-to-table continuum for the control of human salmonellosis in the United States, a quantitative microbial risk assessment (QMRA) model was established. The model predicted an average of 45 cases of salmonellosis (95% CI = [19, 71]) per 100,000 Americans annually due to WFGP consumption. Sensitivity analysis of all stochastic input variables showed that cooking temperature was the most influential parameter for reducing salmonellosis cases associated with WFGP meals, followed by storage temperature and Salmonella concentration on contaminated carcass surface before fabrication. The input variables were grouped to represent three main factors along the slaughter-to-table chain influencing Salmonella doses ingested via WFGP meals: DTLN-related factors, factors at processing other than DTLNs, and consumer-related factors. The evaluation of the impact of each group of factors by second-order Monte Carlo simulation showed that DTLN-related factors had the lowest impact on the risk estimate among the three groups of factors. These findings indicate that interventions to reduce Salmonella contamination in DTLNs or to remove DTLNs from WFGP products may be less critical for reducing human infections attributable to ground pork than improving consumers' cooking habits or interventions of carcass decontamination at processing.

The fates of microbial populations on pig carcasses during slaughtering process, on retail cuts after slaughter, and intervention efficiency of lactic acid spraying

This study was conducted to detect and identify microbial populations on pig carcasses at different slaughtering stages and on retail pork cuts at 24 h after slaughter as well as to evaluate the intervention efficiency of sprays containing different concentrations (2% and 4%) of lactic acid. The sprays were applied to the carcass surfaces at the end of the slaughter line. Microbial samples were collected from carcass surfaces after bleeding and after eviscerating, and from retail cuts at 24 h after chilling/spraying. The detected microorganisms were identified through using a Microflex identification instrument and 16S rRNA gene sequencing. The diversity of the bacterial genera; Staphylococcus, Salmonella, Shigella, Enterococci, Escherichia, Acinetobacter and Corynebacterium spp. showed counts ranging from 2.70 to 4.91 log₁₀ cfu/100 cm² on the carcasses during slaughter. Most of these genera were also detected on the carcasses after 24 h of chilling. Three species (Staphylococcus hyicus, Acinetobacter albensis, and Corynebacterium xerosis) were also found on the retail cuts of non-sprayed carcasses but not on those of the sprayed groups. Significantly greater reductions in all bacterial species were observed on the carcasses and retail cuts that were sprayed with lactic acid, particularly at the 4% level. Thus, spraying with 4% lactic acid may be an effective intervention for controlling bacterial contamination on pig carcasses to improve the microbiological safety of pork meat.

Association between antimicrobial usage, biosecurity measures as well as farm performance in German farrow-to-finish farms

Background

Antimicrobial usage in food producing animals is of major concern. A clear link between the extent of use and the development of antimicrobial resistance has already been demonstrated. To evaluate strategies that may reduce the antimicrobial usage while assuring pig health and welfare, it requires profound knowledge of factors that are associated with antimicrobial usage. Data on biosecurity and herd management practices are important parameters to identify risk factors which are related to a higher antimicrobial usage. To investigate between-farm variations of high and low usage the treatment incidence (TI) per age group in 60 German farrow-to-finish herds was qualitatively and quantitatively analysed and linked to biosecurity measures, and herd management characteristics.

Results

Weaned pigs received most of the treatments (median TI = 487.6), followed by suckling pigs (median TI = 138.9). Suckling pigs were treated with critically important antimicrobials (3rd and 4th generation cephalosporines) to a remarkable extent. The number of sows present at site (p < 0.01) and a low score for external biosecurity (p = 0.06) were associated with a higher antimicrobial usage in pigs from birth till slaughter. Herds with a higher treatment incidence in growing pigs (TI 200 days): i) were located in a region with a high pig density (p < 0.01), ii) had a less strict access check for visitors and personnel (p < 0.01) and iii) scored lower in the subcategory ‘cleaning and disinfection’ (internal biosecurity) (p < 0.01). Herds with a higher treatment incidence in breeding pigs weaned more piglets per sow and year and scored better in the internal biosecurity level (p = 0.02).

Conclusions

With the main focus on the treatment incidence in pigs from birth till slaughter and in breeding pigs risk factors for a high usage in these age groups were identified. The level of biosecurity of a herd was associated with the amount of antimicrobials used. Therefore, the findings in this study indicate possible points of action in the reduction and prudent use of antimicrobials in Germany. The active improvement of biosecurity measures could be a promising alternative to reduce antimicrobial usage on herd level.

Electronic supplementary material

The online version of this article (10.1186/s40813-018-0106-5) contains supplementary material, which is available to authorized users.

Antibody Responses to Salmonella in Pigs from Weaning Up to Marketing and Presence of Salmonella at Slaughter

Salmonella is estimated to be one of the leading causes of enteric illness worldwide. Human salmonellosis is most frequently related to contaminated food products, particularly those of animal origin, such as pork. Pigs are often asymptomatic carriers of Salmonella, highlighting the importance of identifying high-prevalence farms and effective detection methods. The objectives of this study were to investigate Salmonella antibody responses and their association with on-farm shedding and Salmonella isolation at slaughter. Fourteen groups of pigs from eight farrowing sources were followed from birth to slaughter (totaling 796 pigs). Information about farm management was collected through a questionnaire. Blood and fecal samples were collected four times at different stages of production, and palatine tonsils/submandibular lymph nodes were obtained at slaughter. Sera were tested for Salmonella antibodies by enzyme-linked immunosorbent assay, and fecal/tissue samples were cultured for Salmonella. Data were analyzed using a mixed-effect multivariable modeling method with farm, litter, and pig as random effects. Salmonella seropositivity rates were 20.3%, 5.8%, 15.9%, and 37.3% at weaning, at the end of nursery, at end of grower, and at end of finisher, respectively. Salmonella seropositivity and shedding increased with age (p < 0.05), and pigs shedding Salmonella were more likely to test seropositive (p = 0.02). Antibody response and shedding on-farm had no significant association with isolation of Salmonella from tissues harvested at slaughter. The variation in Salmonella seropositivity due to farm was 28.9% of total variation. These findings indicate that on-farm intervention may be a more effective approach to control Salmonella and to reduce the presence of Salmonella at slaughter. Additionally, the observation that some pigs in this study were Salmonella-negative throughout production and at slaughter is promising with regard to food safety, and studies are needed to explore the genotypes of those pigs.

Descriptive and multivariate analysis of the pig sector in Georgia and its implications for disease transmission

BACKGROUND

Georgia is a country in the Caucasus region with a traditional backyard and highly variable pig farming system. The practices of such sectors have seldom been described and analyzed to better understand their implication in the introduction and spread of infectious pig diseases. Moreover, the Georgian pig sector was badly hit by an epidemic of African swine fever in 2007 that quickly spread throughout the region.

MATERIALS AND METHODS

We interviewed 487 pig farmers and 116 butchers using closed questionnaires on socioeconomic issues related to pig production, husbandry practices, biosecurity, marketing and movements, and disease awareness. Surveys were conducted in four regions of Georgia and descriptive statistics were computed. Factorial analyses of mixed data and hierarchical clustering on principal components were applied to study the relationship among collected variables for both farmers and butchers.

RESULTS

Results show that pig farming in Georgia is a non-professional sector, highly heterogeneous by region, characterized by smallholdings of few animals, with low inputs, outdated technologies, and poor biosecurity, which all translates into low outputs and productivity. The hierarchical clustering on principal components confirmed that there are five major production and husbandry strategies, which match the four regions where the study was conducted.

CONCLUSIONS

Our results are the first step to quantify biosecurity gaps and risky behaviours, develop risk profiles, and identify critical control points across the market chain where to implement mitigation measures. This study provides the baseline information needed to design realistic and sustainable prevention, surveillance and control strategies.

Characterisation of ail-positive Yersinia enterocolitica of different biotypes using HRMA

Yersiniosis is one of the four most frequent foodborne zoonotic diseases in Europe, and Yersinia enterocolitica is the primary agent in human infections. The ail gene is an important chromosomal virulence marker of Y. enterocolitica which encodes Ail, a 17-kDa outer membrane protein that promotes attachment and invasion. In the present study, ail-positive Y. enterocolitica strains of different biotypes were examined using high resolution melting analysis (HRMA) and DNA sequencing. Genotype data relating to Y. enterocolitica strains isolated from different sources and belonging to different biotypes were compared. Applied method allowed efficient distinguishing of three genotypes and phylogenetic groups: 1A - included non-pathogenic Y. enterocolitica strains; 1B - consisted of highly pathogenic Y. enterocolitica strains and 2/4 - involved weakly pathogenic Y. enterocolitica strains. Amplicon genotyping based on HRMA supports rapid identification of ail SNPs correlated with biotype of examined Y. enterocolitica strains.

Looking for new approaches for the use of serology in the context of control programmes against pig salmonellosis

Most swine Salmonella national control programmes in Europe have been based on the categorization of herds according to risk levels based on serological results. However, none of the non-Scandinavian countries have reported of any significant success on Salmonella infection reduction in fattening pigs or the number of human cases attributable to pigs or pork. The limited accuracy of the tests used, the small number of animals sampled and the likely lack of herd representativeness of the samples used could be major factors affecting the suitability of these programmes. Focusing on minimizing Salmonella shedding at slaughter appears more important to prevent human infections than focusing on detection of seropositive pigs/herds at this stage. This study assessed whether performing on-farm serology may help to predict shedding at slaughter. Between 2010 and 2016, pigs from six cohorts from a Salmonella-positive herd were bled at 30, 60 and 90 days on fattening and before slaughter, and faecal samples collected at slaughter. Serology on days 60, 90 and before slaughter predicted somewhat shedding at slaughter with no significant differences among them. Pigs with higher OD% values at these point times would have higher risk of shedding when arriving to slaughter. The probability of shedding for a pig sampled on day 90 and showing an OD% value of 10 was 43%, and the risk increased up to 65% if the OD% was 40. Concluding, on-farm serology may help to determine to some extent the risk of Salmonella shedding at slaughter from seropositive fattening units, which would allow for prompt on-farm and slaughter interventions to reduce the likelihood of slaughter contamination with Salmonella.

Correlation between slaughter practices and the distribution of Salmonella and hygiene indicator bacteria on pig carcasses during slaughter

This study investigated the distribution of hygiene indicator bacteria and Salmonella on pig carcasses. Moreover, the relation between hygiene indicator counts and Salmonella presence as well as associations between specific slaughter practices and carcass contamination were determined for each carcass area. Seven Belgian pig slaughterhouses were visited three times to swab five randomly selected carcasses at nine different areas, after evisceration and trimming. Information about slaughter practices was collected using a questionaire. In all samples, the E. coli and Salmonella presence was analyzed and Enterobacteriaceae and total aerobic bacteria were quantified. Average total aerobic counts ranged from 3.1 (loin, pelvic duct, ham) to 4.4 log₁₀ CFU/cm² (foreleg). Median Enterobacteriaceae numbers varied between 0.4 (ham) an 1.8 log₁₀ CFU/cm² (foreleg). E. coli and Salmonella presence ranged from 15% (elbow) to 89% (foreleg) and 5% (elbow) to 38% (foreleg), respectively. Positive relations were found between hygiene indicator counts and Salmonella presence at the head, sternum, loin and throat. Several slaughter practices, such as splitting the head and incising tonsils, were associated with higher levels of hygiene indicator bacteria and Salmonella. These findings can be used to educate slaughterhouse personnel and estimate the public health risk involved in consumption of different pork cuts.

Low occurrence of pathogenic Yersinia enterocolitica in pig tonsils at slaughter in Southern Brazil

Yersinia enterocolitica is a foodborne pathogen and pigs are the main reservoir of it in their tonsils. As Brazil is a large producer and exporter of pork meat and information regarding this pathogen is still quite scarce, this study aimed at evaluating the direct detection of Y. enterocolitica followed by pathogenic Y. enterocolitica (PYE) determination in tonsils of slaughtered pigs. For this purpose, 400 pig tonsils were collected from 15 farms in four federally certified slaughterhouses in Southern Brazil. Initially, samples were screened using conventional PCR targeting of the 16sRNA gene, followed by multiplex PCR (mPCR) in order to detect three virulence genes (ail, yadA, and virF) and quantitative real-time PCR (qPCR) for the detection of the ail gene. One hundred and one (25.2%) of the samples tested positive for the 16sRNA gene. However, a PYE was detected in one out of the 101 Y. enterocolitica positive samples. The three virulence genes were determined by mPCR and confirmed by partial DNA sequencing. Thus, a significant occurrence of Y. enterocolitica was observed in pig tonsils from federally inspected slaughterhouses in Brazil, although the presence of pathogenic strains was quite low.

Evaluation of an enhanced cleaning and disinfection protocol in Salmonella contaminated pig holdings in the United Kingdom

Salmonella is the second most commonly reported zoonotic gastrointestinal pathogen in the European Union, and a significant proportion of the cases are linked to the consumption of contaminated pork. Reduction of Salmonella at the farm level helps to mininimise the contamination pressure at the slaughterhouse, and therefore the number of Salmonella bacteria entering the food chain. Cleaning and disinfection (C&D) between batches of pigs is an intervention measure that has potential to reduce the transmission of Salmonella contamination within farms. In this study, two pig finisher buildings in each of 10 Salmonella positive farms were sampled pre-C&D, post-C&D, post-restocking with the following batch of pigs, and shortly before these pigs were sent to slaughter. The incoming batch of pigs was also sampled before it reached the study building (pre-restocking). At each visit, pooled and individual faecal samples were collected and Salmonella isolation was carried out according to an ISO 6579:2002 Annex D-based method. One building on each farm (intervention) was cleaned and disinfected according to a rigorous protocol consisting of several steps and a Defra-approved disinfectant used at the General Orders concentration, whilst the other building (control) was cleaned and disinfected as per normal farm routine. At the post-C&D visit, Enterobacteriaceae and total bacterial counts were determined to evaluate residual faecal contamination and general hygiene levels. Rodent specialists visited the farms before and after C&D and rodent carcasses were collected for Salmonella testing. The intervention buildings were significantly less likely (p = 0.004) to be positive for Salmonella after C&D. The pre-restocking pigs had the highest likelihood (p<0.001) of being Salmonella positive (often with multiple serovars) and there was no significant difference between intervention and control buildings in Salmonella prevalence at the post-restocking visit (p = 0.199). However, the pigs housed in the intervention buildings were significantly less likely (p = 0.004) to be positive for Salmonella at slaughter age. Multivariable analysis suggested that cleaning all fixtures of buildings, leaving the pens empty for 2-3 days and using an effective disinfectant are factors significantly improving the likelihood of removing Salmonella contamination during C&D. Signs of rodents were recorded in all farms, but rodent activity and harbourage availability decreased between visits. All the rats tested were Salmonella negative. S. Typhimurium or its monophasic variants were isolated from 6 mouse carcasses in 3 farms where the same serovars were isolated from pigs. This study demonstrates that an appropriate C&D programme significantly reduces the likelihood of residual contamination in Salmonella positive pig buildings, and suggests a significant reduction in the prevalence of Salmonella in the pigs in appropriately cleaned and disinfected buildings when sampled before slaughter. Due to a high prevalence of infection in replacement pigs, control of Salmonella in pig farms is challenging. Rodents may also contribute to the carry-over of infection between batches. C&D is a useful measure to help reduce the number of infected pigs going to the slaughterhouse, but should be supplemented by other control measures along the pig breeding and production chain.

Salmonella in the pork production chain and its impact on human health in the European Union

Salmonella spp. comprise the second most common food-borne pathogens in the European Union (EU). The role of pigs as carriers of Salmonella has been intensively studied both on farm and at slaughter. Salmonella infection in pigs may cause fever, diarrhoea, prostration and mortality. However, most infected pigs remain healthy carriers, and those infected at the end of the fattening period could pose a threat to human health. Contamination of pig carcasses can occur on the slaughter line, and it is linked to cross-contamination from other carcasses and the presence of Salmonella in the environment. Therefore, Salmonella serovars present on pig carcasses can be different from those detected in the same bathes on the farm. In recent years, S. Typhimurium, S. Derby and S. serotype 4,[5],12:i:- (a monophasic variant of S. Typhimurium) have been the most common serovars to be detected in pigs in EU countries, but S. Rissen, S. Infantis, S. Enteritidis and S. Brandenburg have also been reported. In humans, several cases of salmonellosis have been linked to the consumption of raw or undercooked pork and pork products. Among the main serovars of porcine origin detected in confirmed human cases, S. Typhimurium, the monophasic variant S. 4,[5],12:i:- and S. Derby are certainly the most important.

EMA and EFSA Joint Scientific Opinion on measures to reduce the need to use antimicrobial agents in animal husbandry in the European Union, and the resulting impacts on food safety (RONAFA)

EFSA and EMA have jointly reviewed measures taken in the EU to reduce the need for and use of antimicrobials in food-producing animals, and the resultant impacts on antimicrobial resistance (AMR). Reduction strategies have been implemented successfully in some Member States. Such strategies include national reduction targets, benchmarking of antimicrobial use, controls on prescribing and restrictions on use of specific critically important antimicrobials, together with improvements to animal husbandry and disease prevention and control measures. Due to the multiplicity of factors contributing to AMR, the impact of any single measure is difficult to quantify, although there is evidence of an association between reduction in antimicrobial use and reduced AMR. To minimise antimicrobial use, a multifaceted integrated approach should be implemented, adapted to local circumstances. Recommended options (non-prioritised) include: development of national strategies; harmonised systems for monitoring antimicrobial use and AMR development; establishing national targets for antimicrobial use reduction; use of on-farm health plans; increasing the responsibility of veterinarians for antimicrobial prescribing; training, education and raising public awareness; increasing the availability of rapid and reliable diagnostics; improving husbandry and management procedures for disease prevention and control; rethinking livestock production systems to reduce inherent disease risk. A limited number of studies provide robust evidence of alternatives to antimicrobials that positively influence health parameters. Possible alternatives include probiotics and prebiotics, competitive exclusion, bacteriophages, immunomodulators, organic acids and teat sealants. Development of a legislative framework that permits the use of specific products as alternatives should be considered. Further research to evaluate the potential of alternative farming systems on reducing AMR is also recommended. Animals suffering from bacterial infections should only be treated with antimicrobials based on veterinary diagnosis and prescription. Options should be reviewed to phase out most preventive use of antimicrobials and to reduce and refine metaphylaxis by applying recognised alternative measures.

Influence of On-farm pig Salmonella status on Salmonella Shedding at Slaughter

The risk of Salmonella shedding among pigs at slaughter with regard to their previous on-farm Salmonella status was assessed in a group of pigs from a farm from NE of Spain. A total of 202 pigs that had been serologically monitored monthly during the fattening period and from which mesenteric lymph nodes (MLN) and faecal (SFEC) samples were collected at slaughter for Salmonella isolation were included. A repeated-measures anova was used to assess the relationship between mean OD% values during the fattening period and sampling time and bacteriology on MLN and SFEC. Pigs were also grouped into four groups, that is pigs seronegative during the fattening period and Salmonella negative in MLN (group A; n = 69); pigs seronegative during the fattening period but Salmonella positive in MLN (B; n = 36); pigs seropositive at least once and Salmonella positive in MLN (C; n = 50); and pigs seropositive at least once but Salmonella negative in (D; n = 47). Pigs shedding at slaughter seroconverted much earlier and showed much higher mean OD% values than non-shedders pigs. The proportion of Salmonella shedders in groups A and D was high and similar (26.1% and 29.8%, respectively), but significantly lower than that for groups B and C. The odds of shedding Salmonella for groups B and C were 4.8 (95% CI = 1.5-15.5) and 20.9 (3.7-118) times higher, respectively, when compared to A. It was concluded that a large proportion of Salmonella seronegative pigs may shed Salmonella at slaughter, which would be likely associated to previous exposure with contaminated environments (i.e. transport and lairage). For pigs already infected at farm, the likelihood of shedding Salmonella was much higher and may depend on whether the bacterium has colonized the MLN or not. The odds of shedding Salmonella spp. were always much higher for pigs in which Salmonella was isolated from MLN.

Susceptibilidad antimicrobiana de aislamientos de Salmonella enterica provenientes de pisos, equipos, utensilios y producto terminado en el beneficio porcino en Colombia

<p>La diseminación de aislamientos de Salmonella spp resistentes a antimicrobianos, a través de las cadenas productivas de alimentos de origen animal, es una preocupación de salud pública de carácter mundial. Éste estudio describe los patrones de resistencia antimicrobiana de 283 aislamientos de Salmonella enterica procedentes de plantas de beneficio porcino en Colombia. Se evaluó la susceptibilidad antimicrobiana frente a diez antimicrobianos: amoxacilina-ácido clavulánico (30 ug),  ampicilina(10 ug), ceftiofur (30 ug), ciprofloxacina (5 ug), cloranfenicol (30 ug), florfenicol (30 ug),  gentamicina (10 ug), sulfadiazina/trimetroprim (25 ug), tetraciclina (30 ug) y tilmicosina (15 ug) mediante el método de difusión en disco (Bauer &amp; Kirby, 1966). Los resultados evidenciaron la presencia de 279 aislamientos multiresistentes de Salmonella enterica de origen porcino provenientes del ambiente y producto terminado de las plantas de beneficio evaluadas (46.64% n: 132).  Se detectaron 52 patrones de multiresistencia, el más común fue ceftiofur-tetraciclina-tilmicosina en el 9,89% (n: 28) de los aislamientos. Con referencia a éstos antimicrobianos el 96,82% (n: 274) de los aislamientos fueron resistentes a tetraciclina, 73,14% (n: 207) a tilmicosina y 28,27% (n: 80)  a ceftiofur. De especial interés fue la alta proporción de aislamientos resistentes a éste último, debido a una posible resistencia cruzada con ceftriaxona. Los resultados obtenidos demuestran la necesidad de promover y fortalecer un Programa oficial de  Vigilancia de la Resistencia Antimicrobiana y  sistemas de monitoreo voluntario en cada eslabón de las cadenas productivas, para contribuir a la prevención y control de la transmisión de microorganismos  resistentes de origen alimentario en el marco del sistema de gestión de inocuidad alimentaria en Colombia.</p>

Phenotypic and Genotypic Diversity of Salmonella in Finishing Swine

Salmonella enterica (nontyphoidal) is one of the major causes of foodborne diseases in the United States and worldwide. Molecular typing methods are significant tools used to better understand the transmission and ecology of Salmonella in order to implement pre-harvest control measures. The objectives of this study were to describe the Salmonella genotypes, the distribution of isolate subtypes from different ecological niches (i.e., barn environment, nursery, and individual pigs) and their evolution over time in a longitudinal study conducted in three finishing sites (housing pigs from 10 weeks of age until slaughter at 24-26 weeks of age). Among the 107 Salmonella isolates submitted for pulsed-field gel electrophoresis (PFGE) analysis, there were 25 distinct subtypes. PFGE genotyping results were consistent with the serotype findings. A large number of distinguishable PFGE patterns (i.e., within the same serovar) were observed and different combinations of subtypes were identified within and across sites and cohorts. New subtypes may result of the introduction of new strains, genetic changes, or ongoing transmission of evolved strains within the production system. The same subtypes were detected intermittently during the study period, which suggests the persistence of indistinguishable subtypes in this production system. In addition, this study suggests persistence of the same subtype over several cohorts of pigs and potential residual contamination from the barn. Factors affecting adaptation and transmission of Salmonella within and among ecological systems (e.g., finishing pigs, nursery, and environment) should be further investigated. Understanding genotypic diversity of Salmonella in different ecological niches during pre-harvest may contribute to the development of more targeted and cost effective control programs during nursery and finishing phases.

A Farm Transmission Model for Salmonella in Pigs, Applicable to E.U. Member States

The burden of Salmonella entering pig slaughterhouses across the European Union is considered a primary food safety concern. To assist E.U. member states with the development of national control plans, we have developed a farm transmission model applicable to all member states. It is an individual-based stochastic susceptible-infected model that takes into account four different sources of infection of pigs (sows, feed, external contaminants such as rodents, and new stock) and various management practices linked to Salmonella transmission/protection (housing, flooring, feed, all-in-all-out production). A novel development within the model is the assessment of dynamic shedding rates. The results of the model, parameterized for two case study member states (one high and one low prevalence) suggest that breeding herd prevalence is a strong indicator of slaughter pig prevalence. Until a member state's' breeding herd prevalence is brought below 10%, the sow will be the dominant source of infection to pigs raised for meat production; below this level of breeding herd prevalence, feed becomes the dominant force of infection.

Ecology and geographic distribution of Yersinia enterocolitica among livestock and wildlife in China

The results in this study show the prevalence of Yersinia enterocolitica varies in different animal species and regions of China. The highest prevalence is among pigs (12.91%), followed by dogs (9.80%), Ochotona curzoniae (plateau pica) (6.76%), chickens (4.50%), rodents (3.40%), cattle (2.78%) and sheep (0.89%). Pathogenic isolates comprised the majority of the Y. enterocolitica recovered from pigs (73.50%) and dogs (59.44%); whereas the nonpathogenic Y. enterocolitica made up most of poultry and wildlife recovered strains. A correlation analysis comparing the prevalence and geographic factors showed the isolation rate of Y. enterocolitica in pigs and dogs was negatively correlated with elevation (r=-0.50, P<0.05) and annual average air temperature (r=-0.43, P<0.05), but there was positive correlation with annual precipitation (r=0.43, P<0.05); conversely, the isolation rate from wildlife is positively correlated with elevation (r=0.3, P<0.05) contrary to the result seen in livestock. Twelve novel biotype 2 pathogenic Y. enterocolitica carried ail and ystB virulence genes, and one biotype 1A nonpathogenic strain positive with ail, ystB and ystA genes were isolated from Microtus fuscus (Qinghai vole) on plague foci of the Qinghai-Xizang plateau. The PFGE pattern K6GN11C30021 was predominant in pigs (44.25%) and patients (41.18%); K6GN11C30068 was predominant in dogs (40.16%). Animal isolates from the same region shared the same pattern (K6GN11C30021 and K6GN11C30012), indicating they may be from the same clone and arose through cross infection. Moreover, the identical PFGE pattern among local animals and diarrhea patients suggested that the animals may be the source of infections in these areas.

Improvement of bacterial clearance and relief of clinical signs of Salmonella enterica serovar Typhimurium infection in pigs through upregulation of Th 1-specific responses by administration of a combination of two silicate minerals, biotite and bentonite

Biotite and bentonite are phyllosilicate minerals that were originally used in industrial applications. Several beneficial activities of them have recently been reported, especially regulation of the immune system and antimicrobial effects. Therefore, we investigated the immune-enhancing and bacterial clearance effects of a biotite and bentonite mixture (BBM) on experimental infection of Salmonella enterica serovar Typhimurium (S. Typhimurium) to determine whether the BBM could be used as an alternative antibiotic. We administered 1% or 2% BBM as a feed supplement. We then evaluated the bacterial clearance effects of the BBM against S. Typhimurium. We also evaluated the immune-enhancing effect of the BBM through several immunological experiments that included examination of the lysozyme activity, CD4(+)/CD8(+) T lymphocyte ratio and the T-helper type 1 (Th 1) cytokine profile. The clinical signs of S. Typhimurium and the number of viable bacteria in feces and tissues were significantly decreased in both BBM groups, especially in the 2% BBM group. The BBM also markedly enhanced the lysozyme activity, CD4(+)/CD8(+) T lymphocyte ratio and expression levels of IFN-γ and IL-12 in S. Typhimurium-challenged pigs. Therefore, the BBM could be a good candidate as an alternative antibiotic that improves Th 1-specific immune responses and the bacterial clearance effect.

Salmonella Prevalence and Microbiological Contamination of Pig Carcasses and Slaughterhouse Environment

In seven EC swine abattoirs Salmonella prevalence (ISO 6579/2002) and serotypes of 25 piglets, 61 finishing pigs (lymph nodes, colon content, carcass and liver surface) and slaughterhouse environments (scalding water, surfaces in contact with meat and not in contact with meat) were investigated. Moreover, aerobic colony count [total viable count (TVC); ISO 4833] and Enterobacteriaceae (ISO 21528-2) of piglets and finishing pigs' carcasses were evaluated, and the results compared with EU process hygiene criteria (Reg. EC 2073/2005). Salmonella was not isolated in any of the piglets samples. Prevalence differed between slaughterhouses (P<0.5), and Salmonella was isolated from 39 of 244 samples of finishing slaughtered pigs (15.9%) and from 4 of 45 environmental samples (8.9%). In pig samples, carcasses showed the highest prevalence (18%) followed by colon content (14.8%), lymph nodes (13%) and liver (1.6%). S. Anatum was the most prevalent serotype (71.8%), followed by S. Derby (33.3%), S. Bredeney (5%) and S. Holcomb (2.5%). Between environmental samples, S. Anatum (50%), S. Bredeney and S. Derby (25%) were identified. Total viable mean counts (log10 CFU/cm2) of carcass surfaces ranged from 4.6 and 5.7 for piglets, and from 4.6 and 5.9 for finishing pigs, while Enterobacteriaceae ranged between 1.1 and 5 for piglets and between 2.1 and 5.3 for finishing pigs. These results were not in compliance with EU performance criteria. Total aerobic viable counts and Enterobacteriaceae mean levels of environmental samples appeared critical, particularly referred to surfaces in contact with meat (splitting equipment) and indicated an inadequate application of good manufacturing and hygiene practices during slaughtering and sanitisation.

Poly D,L-lactide-co-glycolide (PLGA) nanoparticle-encapsulated honeybee (Apis melifera) venom promotes clearance of Salmonella enterica serovar Typhimurium infection in experimentally challenged pigs through the up-regulation of T helper type 1 specific immune responses

Honeybee (Apis melifera) venom (HBV), which includes melittin and lipid-soluble ingredients (chrysin and pinocembrin), elicited increases in the CD4(+)/CD8(+) T lymphocyte ratio, relative mRNA expression levels of the T helper type 1 (Th 1) cytokines (interferon-γ and IL-12) and reinforced viral clearance of an experimental porcine reproductive and respiratory syndrome (PRRS) virus infection in our previous study. On the basis of that previous study, we have now developed poly-d,l-lactide-co-glycolide (PLGA)-encapsulated HBV nanoparticles (P-HBV) for longer sustained release of HBV. We administered P-HBV to pigs via the rectal route, and then evaluated the potential immune-enhancing and bacterial clearance effects of P-HBV against Salmonella enterica serovar Typhimurium. The CD4(+)/CD8(+) lymphocyte ratio, proliferative capacity of peripheral blood lymphocytes and relative mRNA expression levels of IFN-γ and IL-12 (produced mainly by Th1 lymphocytes) were significantly increased in the P-HBV group up to 2 weeks post-administration of P-HBV. After S. Typhimurium infection, the P-HBV group showed a marked reduction in microbial burden in feces and all tissue samples (including the ileum, cecum, colon, and mesenteric lymph node (MLN)), a significant increase in Th 1 cytokines (IFN-γ, IL-2, and IL-12) and a marked decrease in a Th 2 cytokine (IL-4) in all tissue samples and peripheral blood lymphocytes. Thus, P-HBV may be a promising strategy for immune enhancement and prevention of S. Typhimurium or other bacterial infections.

Tissue-specific expression and regulatory networks of pig microRNAome

Background

Despite the economic and medical importance of the pig, knowledge about its genome organization, gene expression regulation, and molecular mechanisms involved in physiological processes is far from that achieved for mouse and rat, the two most used model organisms in biomedical research. MicroRNAs (miRNAs) are a wide class of molecules that exert a recognized role in gene expression modulation, but only 280 miRNAs in pig have been characterized to date.

Results

We applied a novel computational approach to predict species-specific and conserved miRNAs in the pig genome, which were then subjected to experimental validation. We experimentally identified candidate miRNAs sequences grouped in high-confidence (424) and medium-confidence (353) miRNAs according to RNA-seq results. A group of miRNAs was also validated by PCR experiments. We established the subtle variability in expression of isomiRs and miRNA-miRNA star couples supporting a biological function for these molecules. Finally, miRNA and mRNA expression profiles produced from the same sample of 20 different tissue of the animal were combined, using a correlation threshold to filter miRNA-target predictions, to identify tissue-specific regulatory networks.

Conclusions

Our data represent a significant progress in the current understanding of miRNAome in pig. The identification of miRNAs, their target mRNAs, and the construction of regulatory circuits will provide new insights into the complex biological networks in several tissues of this important animal model.