Antibacterial activity of decontamination treatments for pig carcasses

The prevalence, distribution, and diversity of Salmonella isolated from pork slaughtering processors and retail outlets in the Shandong Province of China

Salmonella is a foodborne pathogen of global significance and is highly prevalent in pork. This study investigated the prevalence, contamination distribution, virulence genes and antibiotic resistance of Salmonella in 3 pork processors in the Shandong Province of China. Samples were collected from 13 different sampling sources across the slaughter procedures (600 samples) as well as at retail outlets supplied by these processors (45 samples). The prevalence was 18.9 % among all the samples, with the highest prevalence observed in feces (40.0 %), lairage pens (38.0 %), and hides (34.0 %). A total of 6 serotypes were identified, with S. Rissen (46.3 %) and S. typhimurium (32.0 %) found to be the most prevalent serotypes. 86.8 % of Salmonella isolates were multi-drug resistant, with the majority of strains resistant to erythromycin, sulfisoxazole, and ampicillin. The multilocus sequence typing analysis revealed 6 STs were obtained from 45 isolates, with the dominant type ST469 accounting for 40.0 % of the total, which suggested a high possibility of cross-contamination between the plant processing chain and retail outlets. This work reveals the prevalence and correlation of Salmonella isolates between pork slaughter and retail outlets and acts as a case-study for stakeholders wishing to improve pork supply chain hygiene, control cross-contamination between the various slaughtering processes, and obtain continuous updates on Salmonella surveillance.

Modeling nonlinear inactivation of hygiene indicator bacteria in pig carcasses during scalding at different pHs

This study aimed to investigate the influence of adding an alkalizing agent to the scalding water of a slaughterhouse in Brazil to inactivate hygiene indicator bacteria in pig carcasses. Scalding is critical during carcass processing because slaughterhouses' scalding water is constantly renewed; therefore, it is usually contaminated with organic matter, such as faeces and dirt from the previous carcasses. The treatments evaluated consisted of counting Enterobacteriaceae and mesophilic bacteria in pork jowls at 62 °C, 65 °C, 68 C, and 72 °C after 0.0, 1.5, 3.0, 4.5, 6.0, and 7.5 min of simulated scalding at the pHs of 7.0 (control) and 11.0 (after addition of alkalizing agent). Decimal reduction times of hygiene indicator bacteria for all treatments were estimated with different nonlinear bacterial inactivation models. As a result, adding the alkalizing agent did not significantly inactivate most of the bacteria in the studied samples. However, it contributed to the inactivation of some bacteria, mostly belonging to the mesophilic group, at some specific temperatures. The results obtained in the current study can provide useful insights into dealing with pig carcass contamination in a real-world scenario and applying the obtained information in the industrial environment.

Exploration of the shelf-life difference between chilled beef and pork with similar initial levels of bacterial contamination

This study compared the shelf-life of beef and pork longissimus lumborum muscles (loins) that had the same initial bacterial loads and were held under the same chilled storage conditions. To identify the underlying pathways, comparisons were conducted from the perspective of the spoilage indicators; protease/lipase activity, and the volatile organic compounds (VOC) generated over 28 d of chilled storage. The initial total viable microbial count (TVC) on Day 0 for both type of meat was 4.3 log10 CFU/g. It was found that the TVC of beef and pork did not differ throughout the total chilled storage period and both ultimately exceeded 7 log10 CFU/g after 28 d. Based on total volatile basic nitrogen (TVB-N) guidelines, pork was spoilt after 21 d of chilled storage and therefore 7 d earlier than beef. Changes in the concentration of VOC spoilage biomarkers, including 1-octen-3-ol, 1-octanol, nonanal, and others, confirmed that pork had a shorter shelf-life than beef. An important reason for the difference in shelf-life between the two types of meat was that pork had a higher protease activity, although the beef had higher levels of total lipase activity. These findings help us understand the differences in the spoilage process of raw meat from different species and explore specific measures to control the spoilage of beef or pork.

Proteomic analysis of Staphylococcus aureus exposed to bacteriocin XJS01 and its bio-preservative effect on raw pork loins

Antibacterial mechanism of bacteriocins against foodborne S. aureus is still to be explored, particularly in proteomics, and a deep and comprehensive study on application of bacteriocins for preservation of raw pork is required. Here, proteomic mechanism of Lactobacillus salivarius bacteriocin XJS01 against foodborne S. aureus 2612:1606BL1486 (S. aureus_26) and its preservation effect on raw pork loins stored at 4 °C for 12 days was investigated. The results showed that 301 differentially abundant proteins (DAPs) were identified between XJS01-treated and -free groups (control group) using Tandem mass tag (TMT) quantitative proteomics technology, which were primarily involved in amino acids and carbohydrate metabolism, cytolysis, defense response, cell apoptosis, cell killing, adhesion, and oxygen utilization of S. aureus_26. Bacterial secretion system (SRP) and cationic antimicrobial peptide resistance may be key pathways to maintain protein secretion and counteract the deleterious effects on S. aureus_26 caused by XJS01. In addition, XJS01 could significantly improve the preservation of raw pork loins by the evaluation results of sensory and antibacterial activity on the meat surface. Overall, this study showed that XJS01 induced a complex organism response in S. aureus, and it could be potential pork preservative.

Efficacy of Antimicrobial Spray Treatments in Reducing Salmonella enterica Populations on Chilled Pork

Studies reporting on alternative antimicrobial interventions for pathogen control on chilled pork carcasses and cuts are limited. In this study, the antimicrobial effects of various spray treatments against Salmonella enterica inoculated on skin-on pork samples were evaluated. Chilled pork jowls were portioned (10 by 5 by 1 cm) and inoculated, on the skin side, with a mixture of six S. enterica serotype strains to target levels of 6 to 7 log CFU/cm² (high inoculation level) or 3 to 4 log CFU/cm² (low inoculation level). Samples were then left nontreated (control) or were treated (10 s) using a laboratory-scale spray cabinet with water, formic acid (1.5%), a proprietary blend of sulfuric acid and sodium sulfate (SSS, pH 1.2), peroxyacetic acid (PAA, 400 ppm), or PAA (400 ppm) that was pH-adjusted (acidified) with acetic acid (1.5%), formic acid (1.5%), or SSS (pH 1.2). Samples (n = 6) were analyzed for Salmonella populations after treatment application (0 h) and after 24 h of refrigerated (4°C) storage. Irrespective of inoculation level, all spray treatments effectively reduced (P < 0.05) Salmonella levels immediately following their application. Overall, pathogen reductions for the chemical treatments, compared to the respective high and low inoculation level nontreated controls, ranged from 1.2 to 1.9 log CFU/cm² (high inoculation level) and 1.0 to 1.7 log CFU/cm² (low inoculation level). Acidification of PAA with acetic acid, formic acid, or SSS did not (P ≥ 0.05) enhance the initial bactericidal effects of the nonacidified PAA treatment. Salmonella populations recovered from all treated samples following 24 h of storage were, in general, similar (P ≥ 0.05) or up to 0.6 log CFU/cm² lower (P < 0.05) than those recovered from samples analyzed immediately after treatment application. The results of the study may be used by processing establishments to help identify effective decontamination interventions for reducing Salmonella contamination on pork.

Surface Decontamination and Shelf-Life Extension of Gilthead Sea Bream by Alternative Washing Treatments

The efficacy of washing and the investigation of alternative sanitizing treatments for the reduction of microbial population are major issues for fresh fish and seafood. Limited work on the effect of alternative washing media on fish, particularly gilthead sea bream, one of the important popular fish species, has been published and no industrial scaling-up has been reported. The objective of this study was to systematically evaluate the effect of surface decontamination treatments on the microbial load of fish and the quality and shelf life during subsequent chilled storage. Citric acid (200 ppm for 0–10 min), lactic acid (200 ppm for 0–10 min), and peracetic acid (0–200 ppm for 0–4 min) were tested as alternative washing media by immersion of gutted gilthead sea bream by evaluating their effect on microbial growth and physicochemical and organoleptic degradation of fish. The results of the study indicated that washing with citric (200 ppm, 10 min) and peracetic acid (200 ppm, 4 min) significantly delayed the growth of spoilage microorganisms (total viable count, Pseudomonas spp., Enterobacteriaceae spp., and H2S-producting bacteria) in gutted fish and extended the shelf life to 18 days at 0 °C, compared to 11 days without washing treatment. Appropriate handling and processing of fish and shelf-life extension may enable longer transportation and thus open new distant markets, as well as contribute to reduce food waste during transportation and storage.

Stress response modulation: the key to survival of pathogenic and spoilage bacteria during poultry processing

The control of bacterial contaminants on meat is a key area of interest in the food industry. Bacteria are exposed to a variety of stresses during broiler processing which challenge bacterial structures and metabolic pathways causing death or sublethal injury. To counter these stresses, bacteria possess robust response systems that can induce shifts in the transcriptome and proteome to enable survival. Effective adaptive responses, such as biofilm formation, shock protein production and metabolic flexibility, require rapid induction and implementation at a cellular and community level to facilitate bacterial survival in adverse conditions. This review aims to provide an overview of the scientific literature pertaining to the regulation of complex adaptive processes used by bacteria to survive the processing environment, with particular focus on species that impact the quality and safety of poultry products like Campylobacter spp., Salmonella enterica and Pseudomonas spp.

Singeing to improve visual aspect and microbiological quality of pig carcasses

ABSTRACT The proper operating conditions of the singeing machine on pig slaughterhouses to achieve good carcass quality are little reported. Thus, this study aimed to evaluate the effect of an automatic singeing machine on the quality of pig carcasses for better control in pork production. A two-factor (pressure and time) completely randomized design was used. The carcasses were subjected to four treatments using gas pressures of 0.6 and 0.8 kgf.cm-2 for 3.7 and 4.2 seconds of exposure to the flame. The carcasses were analyzed as for visual appearance, counts of Enterobacteriaceae and Escherichia coli, and temperature. Gas consumption was also assessed during the process. Carcasses subjected to 0.6 kgf.cm-2 for 4.2 s had a better visual appearance. Both pressure and time reduced the counts of Enterobacteriaceae and E. coli. Regarding gas consumption, exposure to the flame for 4.2 s consumed three times more gas than exposure for 3.7 s. Among the treatments tested, singeing using a pressure of 0.6 kgf.cm-2 for 4.2 s was sufficient to reduce microbial counts and improve visual appearance. This singeing standardization serves as a reference for slaughterhouses to produce pork with a visual appearance of better acceptability by consumers.

Prevalence and Molecular Characterization of Antimicrobial-Resistant Escherichia coli in Pig Farms, Slaughterhouses, and Terminal Markets in Henan Province of China

Escherichia coli is an important foodborne pathogen and also plays key roles in dissemination of antimicrobial resistance genes (ARGs). However, current data on the prevalence of antimicrobial-resistant E. coli at different nodes of the pork supplying chain are still limited. Herein, we investigated drug-resistant phenotypes and molecular characteristics of E. coli strains isolated from different pig farms, slaughterhouses, and terminal markets in the Henan Province of China. A total of 191 (70.74%), 140 (35.09%), and 77 (30.20%) E. coli strains were isolated from 270, 399, and 255 samples collected from pig farms, slaughterhouses, and retailing markets, respectively. Antimicrobial susceptibility testing revealed that these 408 strains showed severe antimicrobial resistance profiles. Approximately 93.19% (178/191), 66.43% (93/140), and 67.53% (52/77) of the isolates from farms, slaughterhouses, and terminal markets were resistant to three of the nine antibiotic classes tested, respectively. Multilocus sequence typing showed that sequence types (STs) 10 and ST101 were commonly identified among the isolates from farms, slaughterhouses, and terminal markets. Isolates belonging to these two STs carried multiple ARGs, conferring resistance to the antibiotics tested. Two important ARGs with great public health concerns (mcr-1 and bla_NDM-1) were found from these two STs. Isolates belonging to these two STs also carried several virulence factor-encoding genes, including astA, tsh, and traT, which might contribute to the pathogenesis of these isolates. The wide prevalence and distribution of these two STs in different nodes of pork supplying chain might represent a big public health threat and should receive more attention.

Effects of spraying lactic acid and peroxyacetic acid on the quality and microbial community dynamics of vacuum skin-packaged chilled beef during storage

A long shelf life for fresh meat products is very important both to processors, retailers and consumers. In this work, the effect of repeat acid spraying on the shelf life of vacuum skin-packaged (VSP) chilled beef, as well as the quality and microbial community dynamics was evaluated. Carcasses were sprayed with 300 ppm peroxyacetic acid (PA) or 3% lactic acid (LA) three times during the chilling process, or one more time of LA spray before packaging (LLA). Quality, sensory attributes and microbial load of VSP beef during 32 days of storage at 4 °C were evaluated. The results showed that quality and sensory scores decreased over time for all treatments, but LLA treated samples were still above the rejection threshold at the end of the storage period. Moreover, the total volatile basic nitrogen value and the total viable counts were 15.0 mg/100 g and 7.2 log CFU/g for the control group, while acid treated groups remained below these two values until the end of the storage period. In particular LLA treated beef steaks exhibited the best preservation potential even at the end of storage. This is attributed to the reduction of Proteobacteria in LLA beef steaks shown by the bacterial diversity analysis via high-throughput sequencing, as well as the lower counts of B. thermosphacta and Enterobacteriaceae during storage. This indicates that LLA treatment has the potential to achieve a shelf life extension of VSP steaks without impacting on quality.

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.

Relative response of populations of Escherichia coli and Salmonella enterica to exposure to thermal, alkaline and acidic treatments

We evaluated the relative response of generic Escherichia coli (GEC), Shiga toxin-producing E. coli (STEC) and Salmonella enterica to heat, alkaline or acid treatments. GEC included strains from carcasses (n = 24) and trim (n = 25) at a small beef plant where no decontamination interventions are used and at a large plant where multiple decontamination interventions are used (carcass n = 25 and trim n = 25). STEC strains belonging to nine serogroups, included isolates from cattle (n = 53), beef (n = 16) and humans (n = 44). S. enterica strains belonging to 29 serotypes, included isolates from humans (n = 30), poultry (n = 26), pork (n = 10) and beef (n = 33). Strains were grown in Brain Heart Infusion (BHI) broth and subjected to the following treatments: 60 °C for 2 min, 5% lactic acid (pH 2.9) for 1 h at 4 °C, or NaOH (pH 11.0) for 2 h at 4 °C. Median log reductions of the GEC populations after heat, alkaline and acid treatment ranged from 2.3 to 3.8, 0.7 to 2.2 and 0.7 to 1.2 log CFU/mL, respectively. No statistically significant difference in reductions was observed between carcass GEC or trim GEC from the large or small plant, except for a greater reduction in trim GEC from the small plant. Median reductions of the STEC populations ranged from 3.3 to 3.5, 0.0 to 0.6, and 0.3 to 0.5 log CFU/mL after heat, alkaline and acid treatment, respectively. The median reductions were not dependent upon isolation source, except between STEC cattle and human isolates after alkaline treatment, where the reduction of the former was higher by 0.6 log unit. For the Salmonella populations, median log reductions ranged from 3.5 to 4.0, 1.7 to 2.4 and 3.7 to 4.1 log CFU/mL after heat, alkaline and acid treatment, respectively. The reductions were not isolation source related. The median log reductions were in the order GEC < STEC < Salmonella after heat treatment and STEC < GEC < Salmonella after alkaline or acid treatment. Overall, the relative response of GEC, STEC and Salmonella in the model system suggests that exposure to heat or pH-based decontamination interventions in meat plants is not associated with increased resistance among E. coli strains in these environments, and total E. coli counts on beef can be indicative of treatment efficacy for the control of Salmonella by heat, lactic acid and alkaline treatment and for the control of STEC subjected to heat.

Evaluation of the safety and efficacy of the organic acids lactic and acetic acids to reduce microbiological surface contamination on pork carcasses and pork cuts

Studies evaluating the safety and efficacy of lactic and acetic acids to reduce microbiological surface contamination on pork carcasses pre-chill and pork meat cuts post-chill were assessed. Lactic acid treatments consisted of 2-5% solutions at temperatures of up to 80°C applied to carcasses by spraying or up to 55°C applied on cuts by spraying or dipping. Acetic acid treatments consisted of 2-4% solutions at temperatures of up to 40°C applied on carcasses by spraying or on cuts by spraying or dipping. The maximum treatment duration was 30 s. The Panel concluded that: [1] the treatments are of no safety concern, provided that the substances comply with the European Union specifications for food additives; [2] spraying of pork carcasses pre-chill with lactic acid was efficacious compared to untreated control, but based on the available data, the Panel could not conclude whether lactic acid was more efficacious than water treatment when spraying of pork carcasses pre-chill or pork meat cuts post-chill. The Panel concluded that dipping of pork meat cuts post-chill in lactic acid was more efficacious than water treatment. However, it could not conclude on the efficacy of acetic acid treatment of pork carcasses pre-chill and/or pork meat cuts post-chill; [3] the potential selection and emergence of bacteria with reduced susceptibility to biocides and/or resistance to therapeutic antimicrobials linked to the use of the substances is unlikely as long as Good Hygienic Practices are implemented; and [4] the release of both organic acids is not of concern for the environment, assuming that wastewaters released by the slaughterhouses are treated, if necessary, to counter the potentially low pH caused by lactic or acetic acid, in compliance with local rules.

Case studies of packaging and processing solutions to improve meat quality and safety

A significant amount of the meat is wasted due to spoilage or safety risks. Active packaging systems have a great potential to reduce waste through chemical and microbial control of the product and/or the storage environment. Although commercial products are already available, active packaging is far from being fully developed. In contrast, passive packaging, such as modified atmosphere packaging (MAP) and vacuum packaging, have been fully implemented. Research conducted at the Danish Meat Research Institute (DMRI), demonstrates that it is possible to create new opportunities for the meat industry by modifying MAP or combining microwave treatment with vacuum packaging. Predictive shelf life models can be used to estimate the shelf life in MAP or vacuum under dynamic temperature conditions. Using the tri-gas guidelines, the industry can benefit from the increased eating quality, and the in-package decontamination process using vacuum packaging in combination with 5.8 GHz microwaves eliminates C. botulinum spores, resulting in increased food safety and an extended shelf life.

Systematic review of the magnitude of change in prevalence and quantity of Salmonella after administration of pathogen reduction treatments on pork carcasses

OBJECTIVE

In this systematic review, we summarized change in Salmonella prevalence and/or quantity associated with pathogen reduction treatments (washes, sprays, steam) on pork carcasses or skin-on carcass parts in comparative designs (natural or artificial contamination).

METHODS

In January 2015, CAB Abstracts (1910-2015), SCI and CPCI-Science (1900-2015), Medline® and Medline® In-Process (1946-2015) (OVIDSP), Science.gov, and Safe Pork (1996-2012) were searched with no language or publication type restrictions. Reference lists of 24 review articles were checked. Two independent reviewers screened 4001 titles/abstracts and assessed 122 full-text articles for eligibility. Only English-language records were extracted.

RESULTS

Fourteen studies (5 in commercial abattoirs) were extracted and risk of bias was assessed by two reviewers independently. Risk of bias due to systematic error was moderate; a major source of bias was the potential differential recovery of Salmonella from treated carcasses due to knowledge of the intervention. The most consistently observed association was a positive effect of acid washes on categorical measures of Salmonella; however, this was based on individual results, not a summary effect measure.

CONCLUSION

There was no strong evidence that any one intervention protocol (acid temperature, acid concentration, water temperature) was clearly superior to others for Salmonella control.

Identifying critical factors influencing the disposal of dead pigs by farmers in China

Disposal of dead pigs by pig farmers may have a direct impact on pork safety, public health, and the ecological environment in China. Drawing on the existing literature, this study analyzed and summarized the main factors that could affect the disposal of dead pigs by pig farmers by conducting a survey of 654 pig farmers in Funing County, Jiangsu Province, China. The purpose of this analysis was to investigate the disposal of dead pigs in China and provide useful regulatory strategies for the government. The interrelationships among dimensions and factors that affect the disposal of dead pigs by farmers were analyzed, and critical factors were identified by a hybrid multi-criteria decision-making method, which is a combination of decision-making trial and evaluation laboratory (DEMATEL) and analytic network process (ANP). Our results demonstrated that production characteristics were the most important dimensions and that costs and profits, scale of farming, pattern of farming, knowledge of relevant laws and regulations, and knowledge of pig disease and prevention were the five most critical factors affecting the disposal of dead pigs by farmers in China at this stage. The significance of this study lies in further discussing some management policies for the Chinese government regarding strengthen regulation of disposing dead pigs.

Effect of low-pressure cold plasma on surface microflora of meat and quality attributes

The aim of this study was to investigate the effect of cold plasma treatment on the inactivation of microorganisms on meat surface and its influence on colour of meat and pH value. Nitrogen, argon and helium plasma were generated by high voltage discharge in a vacuum chamber (final 0.8 MPa) with exposure times of 5 and 10 min. Total number of microorganisms, psychrotrophs and number of yeast and mould were determined using plate method. Instrumental evaluation of colour parameters L* a* b* was performed by colorimeter Minolta Cr 400. Psychrotroph bacteria counts and total number of microorganisms exposed to helium and argon plasma for 10 min were reduced about 3 log cfu/cm(2) and 2 log cfu/cm(2), respectively. Increasing reductions of yeasts and moulds were also obtained and were about 3 cfu/cm(2) (helium) and 2,6 cfu/cm(2) (argon). The usage of nitrogen plasma has not resulted in any significant reduction of counts of psychrotrophs and total. number of microorganisms. Yeasts and moulds were little affected by nitrogen plasma and their numbers decrease about 1 log cfu/cm(2.) after 10 min of treatment. No significant differences in colour parameters and pH value after cold plasma treatment were observed. These results demonstrated that cold plasma has antimicrobial activity and could be a promising method of biodecontamination, but further investigations focusing on meat quality have to be determinate.

From pig to pork: methicillin-resistant Staphylococcus aureus in the pork production chain

Methicillin-resistant Staphylococcus aureus (MRSA) is a major global public health concern and could be a food safety issue. Recurrent reports have documented that pig herds are an important reservoir for MRSA, specifically the livestock-associated sequence type 398. The high prevalence of MRSA in pig primary production facilities and the frequent detection of MRSA of the same types in pork and pig meat products raise the question of underlying mechanisms behind the introduction and transmission of MRSA along the pork production chain. A comprehensive review of current literature on the worldwide presence of livestock-associated MRSA in various steps of the pork production chain revealed that the slaughter process plays a decisive role in MRSA transmission from farm to fork. Superficial heat treatments such as scalding and flaming during the slaughter process can significantly reduce the burden of MRSA on the carcasses. However, recontamination with MRSA might occur via surface treating machinery, as a result of fecal contamination at evisceration, or via increased human handling during meat processing. By optimizing processes for carcass decontamination and avoiding recontamination by effective cleaning and personal hygiene management, transmission of MRSA from pig to pork can be minimized.

Role of slaughtering in Salmonella spreading and control in pork production

Salmonella is one of the major foodborne pathogens worldwide. Pork products are among the main sources of Salmonella infection in humans, and several countries have established Salmonella surveillance and control programs. The role of slaughtering in carcass contamination has been indicated by studies focused on the slaughterhouse environment. In this review, we examine and discuss the information available regarding the influence that farm status, pig transport, and lairage have on the carriage of Salmonella by pigs entering the slaughter line. The evolution of carcass contamination throughout the slaughtering process, the main sources of contamination in the dirty and clean zones of the slaughter line, and previously reported prevalence of Salmonella on carcasses and factors affecting this prevalence also are discussed. The importance of implementing interventions at the slaughter level is discussed briefly. Consistent with the information available, pigs from infected farms and newly acquired or recrudescent infections in pigs at the subsequent stages of transport and lairage are important sources of Salmonella at the slaughtering plant. The continuous introduction of Salmonella into the slaughterhouse and the potential for resident flora constitute a risk for carcass contamination. At the slaughterhouse, some dressing activities can reduce carcass contamination, but others are critical control points that jeopardize carcass hygiene. This information indicates the importance of considering slaughter and previous stages in the pork production chain for controlling Salmonella in swine production.