Evaluation of Salmonella presence in selected United States feed mills

Surveillance of antimicrobial resistance, phenotypic, and genotypic patterns of Salmonella enterica isolated from animal feedstuffs: Annual study

Background and Aim

Salmonellosis is a significant foodborne disease that causes serious illness in the gastrointestinal of humans and it is a public health problem worldwide. This study aimed to determine Salmonella spp. in animal feeds, its characteristic, serovar identification, genotyping, and drug sensitivity.

Materials and Methods

Salmonella spp. from animal feedstuffs was collected from January 1 to December 31, 2017, with 657 samples. Serogroup classification was performed by using the slide agglutination test. Then, the samples were analyzed for genotype patterns using pulsed-field gel electrophoresis (PFGE) for DNA fingerprint and antibiotic sensitivity by Vitek® 2 techniques.

Results

A total of 80 samples (12.17 %) were found to be Salmonella positive; commercial feed compounds of 60 samples (75%); soybean meal of 10 samples (12.5%); pork meal of 5 samples (6.25%); a fish meal of three samples (3.75%) and poultry meal of 2 samples (2.5%). Serogroups B, C, D, and E were found in this study; 8 samples (10%), 39 samples (48.75%), 8 samples (10%), and 13 samples (16.25%), respectively. A total of 12 samples (15%) were not determined by serogrouping. The most common serovars were Salmonella Rissen (10%), Salmonella Mbandaka (8.75%), and Salmonella Livingstone (6.25%), which belong to serogroup C. Nine of eleven pulsotypes were detected when analyzed by PFGE, showed similarity index between 40.8 and 100 %. Antimicrobial susceptibility tests by Vitek® 2 compact for 11 strains were classified into three groups: resistance to 4, 8, and 11 antibiotics, out of 20 antibiotics.

Conclusion

This study revealed annual variation of Salmonella spp. Serovar, genotype, and phenotype from commercial feed compounds and raw materials of which involved people must be aware.

Feed safety evaluation for prevalence of zoonotic Salmonella spp. in animal feed

Owing to the zoonotic nature of Salmonella, its transmission from feed-to-food is quite feasible and considered as one of the prime factors for the transmission and spread of virulent and drug-resistant strains in humans. Therefore, the present study was designed to investigate the prevalence of Salmonella in animal feed pellets from different feed mills in Jaipur and its nearby areas. For this, isolation of Salmonella was performed as per standard ISO methods and the presumable strains were further confirmed and characterized into different species by molecular methods. The confirmed strains were analyzed for virulence genes by PCR. Finally, the strains were analyzed for antimicrobial drug resistance by the standard disk diffusion method. The study revealed that the prevalence of Salmonella in feed pellets was moderate and Salmonella enteritidis and Salmonella typhimurium were the two dominated species. Strikingly, the majority of strains were found to possess the virulence genes and resistant to analyzed clinical antimicrobials. Results inferred that contaminated animal feeds may act as a potential source for the dissemination of virulent and drug-resistant Salmonella spp in animals as well as human beings. The present study implicated the need for more focused and extensive investigations from different parts of the country and the world for strict regulation of animal feed safety to assure one health concept.

Salmonella enterica 4,[5],12:i:-, an Emerging Threat for the Swine Feed and Pork Production Industry

ABSTRACT

Salmonella continues to be a significant cause of foodborne illnesses in human medicine. The Centers for Disease Control and Prevention reported Salmonella as the second leading cause of foodborne illness in the United States and the leading cause of both hospitalizations and deaths. Salmonella enterica 4,[5],12:i:- (STM) is a monophasic variant of Salmonella Typhimurium, and it is an emerging threat to both human and animal health. STM was first identified in the 1980s from poultry products and has become increasingly prevalent in meat products including pork. STM has also been identified in swine farms as well as in feed manufacturing environments and feed itself. Similar pulse-field gel electrophoresis profiles have been observed between human clinical cases and the STM samples originating from swine feed. These related profiles suggest a link between ingestion of contaminated feed by swine and the source of foodborne illness in human. The objective of this article was to better understand the history of STM and the possible pathway from swine feed to table. Continued research is necessary to better understand how STM can enter both the feed supply chain and the pork production chain to avoid contamination of pork products destined for human consumption.

HIGHLIGHTS

Antimicrobial-resistant Salmonella is detected more frequently in feed milling equipment than in raw feed components or processed animal feed

Food for human and animal consumption can provide a vehicle for the transfer of pathogenic and antimicrobial‐resistant bacteria into the food chain. We investigated the antimicrobial susceptibility of 453 Salmonella isolates collected from raw feed components, equipment and finished feed from 17 commercial feed mills in Australia between 2012 and 2021. Previous studies have found Salmonella prevalence and the diversity of Salmonella serotypes are greatest in the raw feed components. We, therefore, hypothesised that we would find a greater proportion of antimicrobial‐resistant Salmonella isolates in the raw feed components compared to other sample types. We found that of 453 isolates tested, 356 (0.80) were susceptible to all antimicrobials tested, 49 (0.11) were nonsusceptible to streptomycin only and 48 (0.11) were resistant to two or more antimicrobials. Of the 48 antimicrobial‐resistant isolates, 44 were found in feed milling equipment, two in raw feed components and two in finished feed. Statistical analysis, using a logistic regression with random effects model, found that the population‐adjusted mean probability of detecting antimicrobial‐resistant Salmonella isolates from feed milling equipment of 0.39, was larger than the probability of detecting resistant isolates in raw feed components 0.01, (P < 0.001) and in finished feed, 0.11, (P = 0.006). This propensity for antimicrobial‐resistant bacteria to colonise feed milling equipment has not been previously reported. Further studies are required to understand the ecology of antimicrobial‐resistant Salmonella in the feed milling environment.

Salmonella detection in commercially prepared livestock feed and the raw ingredients and equipment used to manufacture the feed: A systematic review and meta-analysis

Salmonella contamination of livestock feed is a serious veterinary and public health issue. In this study we used a systematic review to assess the prevalence and characterization of Salmonella isolates detected in raw feed components, feed milling equipment and finished feed from 97 studies published from 1955 to 2020 across seven global regions. Eighty-five studies were included in a meta-analyses to estimate the combined prevalence of Salmonella detection and to compare the risk of contamination associated with different sample types. We found the overall combined prevalence estimate of Salmonella detection was 0.14 with a prevalence of 0.18 in raw feed components, 0.09 in finished feed and 0.08 in feed milling equipment. Animal based raw feed components were 3.9 times more likely to be contaminated with Salmonella than plant based raw feed components. Differences between studies accounted for 99 % of the variance in the prevalence estimate for all sample types and there was no effect of region on the prevalence estimates. The combined prevalence of Salmonella detection in raw feed components decreased from 0.25 in 1955 to 0.11 in 2019. The proportion of Salmonella isolates that were resistant to antimicrobials was largest for amikacin (0.20), tetracycline (0.18) streptomycin (0.17), cefotaxime (0.14) and sulfisoxazole (0.11). The prevalence of Salmonella contamination of animal feed varies widely between individual studies and is an ongoing challenge for the commercial feed industry. Control relies on the vigilant monitoring and control of Salmonella in each individual mill.

Salmonella Diversity Along the Farm-to-Fork Continuum of Pastured Poultry Flocks in the Southeastern United States

Greater consumer demand for all natural, antibiotic-free poultry products has led to an increase in pastured poultry operations. Given the increased level of environmental interaction, and the potential increase in exposure to foodborne pathogens, a greater understanding of the prevalence and diversity of Salmonella populations inherent within pastured poultry flocks. To achieve this, 42 pastured poultry flocks from 11 farms were sampled using a farm-to-fork strategy and Salmonella was isolated and characterized through pre-harvest (feces, soil) to post-harvest (ceca, whole carcass rinse) to the final product (whole carcass rinse) the consumer would purchase. Salmonella was isolated from 353 of a total of 2,305 samples, representing an overall prevalence of 18.1%. By far the most prevalent serotype was Kentucky (72.7% of all isolates), with &lt;16% of all Salmonella representing a top serotype of concern for human health according to the CDC. Even though these flocks were raised antibiotic-free, Salmonella isolates exhibited resistances to a variety of antibiotics, with the two most common resistances being toward tetracycline and streptomycin (68.8 and 64.4% of all isolates, respectively); however, almost 98% of the multidrug resistant isolates were serotype Kentucky. Salmonella prevalence and diversity (both in terms of serotypes and antibiotic resistance profiles) were related more to the farm location than to the type of sample from which the Salmonella was isolated from along the farm-to-fork continuum. Based on these data, while Salmonella prevalence was similar to that from conventional poultry operations, serotypes of lesser concern to human health (Kentucky, Indiana) tended to fill the ecological niche for Salmonella species throughout the farm-to-fork continuum in these pastured poultry flocks. The diversity of these Salmonella populations tended to be farm specific, indicating the need for more tailored intervention strategies to continue to enhance the safety of these products.

Sampling and detection of African swine fever virus within a feed manufacturing and swine production system

Transmission of biological hazards capable of causing disease in livestock can occur through a wide variety of direct and indirect routes. In swine production, there are a large number of possible routes of exposure of a pathogen into a susceptible population. African swine fever virus (ASFV) has been a significant challenge for Southeast Asia since first detected in China in 2018 and has spread through many countries within the region. In order to understand potential transmission pathways within an ASFV endemic region, a diagnostic investigation was performed to determine the level of contamination on a wide variety of surface types within a live animal production, feed manufacturing, and feed distribution system located in Vietnam. All diagnostic testing was performed locally by the production system's internal diagnostic laboratory using real‐time polymerase chain reaction (rt‐PCR) analysis. Early in the diagnostic investigation, it became clear that feed trucks were a common site of ASFV surface contamination detection. This information resulted in biosecurity‐focused actions for feed trucks arriving back at the feed mill, including decontamination of interior truck cab surfaces and washing of exterior truck surfaces with high‐pressure water prior to application of surface disinfectants. Additionally, a low number of rt‐PCR positive samples were detected within the feed production system, with the greatest number coming from transient surfaces such as high traffic areas and worker clothing. This illustrates the importance of managing employee traffic through procedures such as zoning and separation between clean–dirty areas to reduce the likelihood of pathogen transmission. In conclusion, this report illustrates the importance of routine data capture regarding efficacy of biosecurity procedures which allows for real‐time updates and improvement as biosecurity gaps are identified.

Using environmental sampling to evaluate the effectiveness of decontamination methods to reduce detection of porcine epidemic diarrhea virus RNA on feed manufacturing surfaces

Porcine epidemic diarrhea virus (PEDV) is a possible biological hazard in feed mills. If the virus enters a feed mill, it becomes widely distributed and is difficult to decontaminate from both feed contact and non-feed contact surfaces. The objective of this study was to evaluate a variety of liquid and dry decontamination treatments that could be used to reduce the amount of PEDV found on feed manufacturing surfaces. This experiment was designed as a 5 × 10 factorial with five different feed manufacturing surfaces and 10 decontamination treatments with three replicates of each combination. Surfaces included stainless steel, solid polyethylene, woven polypropylene tote bag, rubber, and sealed concrete coupons. One mL (1×10⁵ TCID₅₀/mL) of stock PEDV was applied to each surface and allowed to dry completely for 60 min. Next, for decontamination requiring surface application, the application was performed and allowed 15 min contact time. The quantity of PEDV RNA was determined using quantitative reverse transcription PCR. A decontamination treatment × surface interaction was observed (P < 0.0001), indicating the efficacy of treatment is dependent upon the surface in which it is applied. Within the cement surfaces, the sodium hypochlorite resulted in the greatest (P < 0.05) cycle threshold (Ct) value, followed by formaldehyde which had a greater (P < 0.05) Ct value compared to remaining treatments. Within polyethylene, rubber, and stainless steel surfaces, the formaldehyde treated surfaces had the greatest Ct values (P < 0.05), followed by the sodium hypochlorite treatment, with other treatments all having lower Ct values (P < 0.05). For the woven polyethylene surfaces, the formaldehyde and sodium hypochlorite treatments had greater Ct values compared to all other treatments (P < 0.05). Additional research is necessary to identify the role of decontamination treatment on PEDV infectivity and develop methods for decontamination of feed manufacturing facilities.

Can we effectively manage parasites, prions, and pathogens in the global feed industry to achieve One Health?

Prions and certain endoparasites, bacteria, and viruses are internationally recognized as types of disease-causing biological agents that can be transmitted from contaminated feed to animals. Historically, foodborne biological hazards such as prions (transmissible spongiform encephalopathy), endoparasites (Trichinella spiralis, Toxoplasma gondii), and pathogenic bacteria (Salmonella spp., Listeria monocytogenes, Escherichia coli O157, Clostridium spp., and Campylobacter spp.) were major food safety concerns from feeding uncooked or improperly heated animal-derived food waste and by-products. However, implementation of validated thermal processing conditions along with verifiable quality control procedures has been effective in enabling safe use of these feed materials in animal diets. More recently, the occurrence of global Porcine Epidemic Diarrhea Virus and African Swine Fever Virus epidemics, dependence on international feed ingredient supply chains, and the discovery that these viruses can survive in some feed ingredient matrices under environmental conditions of trans-oceanic shipments has created an urgent need to develop and implement rigorous biosecurity protocols that prevent and control animal viruses in feed ingredients. Implementation of verifiable risk-based preventive controls, traceability systems from origin to destination, and effective mitigation procedures is essential to minimize these food security, safety, and sustainability threats. Creating a new biosafety and biosecurity framework will enable convergence of the diverging One Health components involving low environmental impact and functional feed ingredients that are perceived as having elevated biosafety risks when used in animal feeds.

Feedborne Salmonella enterica Serovar Jerusalem Outbreak in Different Organic Poultry Flocks in Switzerland and Italy Linked to Soya Expeller

Poultry feed is a leading source of Salmonella infection in poultry. In Switzerland, heat-treated feed is used to reduce Salmonella incursions into flocks in conventional poultry production. By contrast, organic feed is only treated with organic acids. In 2019, the Swiss National Reference Center for Enteropathogenic Bacteria identified the rare serovar S. Jerusalem from samples of organic soya feed. Further, in July 2020, the European Union’s Rapid Alert System for Food and Feed published a notification of the detection of S. Jerusalem in soya expeller from Italy. During 2020, seven S. Jerusalem isolates from seven different poultry productions distributed over six cantons in Switzerland were reported, providing further evidence of a possible outbreak. Using whole-genome sequencing (WGS), S. Jerusalem isolates from feed and from animals in Switzerland were further characterized and compared to S. Jerusalem from organic poultry farm environments in Italy. WGS results showed that feed isolates and isolates from Swiss and Italian poultry flocks belonged to the sequence type (ST)1028, grouped in a very tight cluster, and were closely related. This outbreak highlights the risk of spreading Salmonella by feed and emphasizes the need for a heat-treatment process for feed, also in organic poultry production.

Selected Instrumental Techniques Applied in Food and Feed: Quality, Safety and Adulteration Analysis

This review presents an overall glance at selected instrumental analytical techniques and methods used in food analysis, focusing on their primary food science research applications. The methods described represent approaches that have already been developed or are currently being implemented in our laboratories. Some techniques are widespread and well known and hence we will focus only in very specific examples, whilst the relatively less common techniques applied in food science are covered in a wider fashion. We made a particular emphasis on the works published on this topic in the last five years. When appropriate, we referred the reader to specialized reports highlighting each technique's principle and focused on said technologies' applications in the food analysis field. Each example forwarded will consider the advantages and limitations of the application. Certain study cases will typify that several of the techniques mentioned are used simultaneously to resolve an issue, support novel data, or gather further information from the food sample.

Microbiological Hazards in Dry Dog Chews and Feeds

Nowadays, dogs are usually equally treated with other family members. Due to the growing caregivers' awareness, the pet foods industry is changing dynamically. Pet foods are manufactured with a myriad of ingredients. Few authors of scientific papers deal with the topic of foods products' safety for pet animals, assessed from the perspective of their caregivers. Despite the many methods of producing foods of the highest quality, there are still cases of contamination of pet foods and treats. In the case of dried chews for dogs, bacteria of the genus Salmonella are the most common risk. In the case of both dry and wet foods, in addition to many species of bacteria, we often deal with mold fungi and their metabolites, mycotoxins. This article presents selected microbiological risks in dog foods and treats, and analyzes the Rapid Alert System for Food and Feed (RASFF) system (2017-2020) for pathogenic microorganisms in dried dog chews, treats and foods. In this period, pet food-related notifications were registered, which were categorized into different types. Analyzing the RASFF notifications over the period, it has been shown that there are still cases of bacterial contamination of dog foods and treats, while in terms of the overall mycotoxin content, these products may appear safe.

Biosecurity in pig farms: a review

The perception of the importance of animal health and its relationship with biosecurity has increased in recent years with the emergence and re-emergence of several diseases difficult to control. This is particularly evident in the case of pig farming as shown by the recent episodes of African swine fever or porcine epidemic diarrhoea. Moreover, a better biosecurity may help to improve productivity and may contribute to reducing the use of antibiotics. Biosecurity can be defined as the application of measures aimed to reduce the probability of the introduction (external biosecurity) and further spread of pathogens within the farm (internal biosecurity). Thus, the key idea is to avoid transmission, either between farms or within the farm. This implies knowledge of the epidemiology of the diseases to be avoided that is not always available, but since ways of transmission of pathogens are limited to a few, it is possible to implement effective actions even with some gaps in our knowledge on a given disease. For the effective design of a biosecurity program, veterinarians must know how diseases are transmitted, the risks and their importance, which mitigation measures are thought to be more effective and how to evaluate the biosecurity and its improvements. This review provides a source of information on external and internal biosecurity measures that reduce risks in swine production and the relationship between these measures and the epidemiology of the main diseases, as well as a description of some systems available for risk analysis and the assessment of biosecurity. Also, it reviews the factors affecting the successful application of a biosecurity plan in a pig farm.

Incidence of Salmonella serovars isolated from commercial animal feed mills in the United States and serovar identification using CRISPR analysis

AIMS

In this study, we sought to determine the incidence and diversity of Salmonella in a broad collection of commercial animal feeds collected from animal feed mills across the United States over an 11-month period and utilize CRISPR analysis to identify individual serovars.

METHODS AND RESULTS

Over two independent trials, 387 feed samples from 135 different animal feed mills in the United States were screened for Salmonella. A total of 6·2% (24/387) of samples were contaminated with Salmonella, which is concordant with similar studies. Clustered regularly interspaced short palindromic repeats (CRISPR)-typing was used to serotype Salmonella isolates, and serovars Infantis and Tennessee were the most common.

CONCLUSIONS

Serogroups O:4 and O:7 were enriched in the feed samples, suggesting that these serogroups are better adapted to surviving in low moisture animal feeds. The study supports the utility of CRISPR to determine serovar type since most of the serovars identified in this study have been also isolated and identified in earlier studies using more classical serotyping methods.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work contributes to a growing body of literature concerning the Salmonella prevalence in animal feeds and highlights the need to effectively mitigate pathogens in livestock and poultry feed.

A review of strategies to impact swine feed biosecurity

Global pork production has largely adopted on-farm biosecurity to minimize vectors of disease transmission and protect swine health. Feed and ingredients were not originally thought to be substantial vectors, but recent incidents have demonstrated their ability to harbor disease. The objective of this paper is to review the potential role of swine feed as a disease vector and describe biosecurity measures that have been evaluated as a way of maintaining swine health. Recent research has demonstrated that viruses such as porcine epidemic diarrhea virus and African Swine Fever Virus can survive conditions of transboundary shipment in soybean meal, lysine, and complete feed, and contaminated feed can cause animal illness. Recent research has focused on potential methods of preventing feed-based pathogens from infecting pigs, including prevention of entry to the feed system, mitigation by thermal processing, or decontamination by chemical additives. Strategies have been designed to understand the spread of pathogens throughout the feed manufacturing environment, including potential batch-to-batch carryover, thus reducing transmission risk. In summary, the focus on feed biosecurity in recent years is warranted, but additional research is needed to further understand the risk and identify cost-effective approaches to maintain feed biosecurity as a way of protecting swine health.

Formic Acid as an Antimicrobial for Poultry Production: A Review

Organic acids continue to receive considerable attention as feed additives for animal production. Most of the emphasis to date has focused on food safety aspects, particularly on lowering the incidence of foodborne pathogens in poultry and other livestock. Several organic acids are currently either being examined or are already being implemented in commercial settings. Among the several organic acids that have been studied extensively, is formic acid. Formic acid has been added to poultry diets as a means to limit Salmonella spp. and other foodborne pathogens both in the feed and potentially in the gastrointestinal tract once consumed. As more becomes known about the efficacy and impact formic acid has on both the host and foodborne pathogens, it is clear that the presence of formic acid can trigger certain pathways in Salmonella spp. This response may become more complex when formic acid enters the gastrointestinal tract and interacts not only with Salmonella spp. that has colonized the gastrointestinal tract but the indigenous microbial community as well. This review will cover current findings and prospects for further research on the poultry microbiome and feeds treated with formic acid.

Potential risk-factors affecting Salmonella sp. and Escherichia coli occurrence and distribution in Midwestern United States swine feed mills

AIM

This study aimed to evaluate the patterns and potential risk factors associated with the occurrence of Salmonella sp. and Escherichia coli in selected United States swine feed mills.

METHODS AND RESULTS

A total of 405 samples were collected during fall 2018, spring and summer 2019 from selected sites including floors, equipment, shoes and feed in six feed mills in the US Midwest region. Each sample was analysed for the presence of Salmonella and E. coli with culture methods and confirmed by PCR. A survey regarding production volumes, hygiene practices and microbial testing capabilities was conducted in each facility All mills had at least one sampling site positive for either Salmonella or E. coli. Of the 405 samples, 4·7, and 14·1% were positive for Salmonella sp., and E. coli respectively. Sites with higher percentages of positive samples were the receiving, manufacturing, and control area floors. The survey responses indicated that the age of the mill might be a risk factor for bacterial contamination: the older the facility, the higher the number of positive samples. Other risk factors evaluated, such as the production capacity, did not appear to relate to bacterial prevalence.

CONCLUSION

The data documents the presence of E. coli and Salmonella in selected US swine feed mills, and an association between E. coli occurrence and number of ingredient suppliers to feed mill.

SIGNIFICANCE AND IMPACT OF THE STUDY

This information could be used to understand risk factors affecting the occurrence of Salmonella sp. and E. coli in feed mills and help implement monitoring and mitigation strategies for public health.

Reviewing the risk of feed as a vehicle for swine pathogen transmission

BACKGROUND

While porcine biological hazards have had the potential to be transmitted through feed and feed mills for decades, the emerging threat of foreign animal disease has elevated the concern that these may enter or be transmitted throughout the domestic swine herd via a feed vehicle.

OBJECTIVE

The goal of this review was to describe the current classification for emerging porcine biological pathogen transmission through the feed supply chain so resources can be best directed towards those of highest risk.

METHODS

By assessing the pathogen severity to pigs and the probability of pathogen transmission through feed, an overall risk can be established using a hazard analysis matrix.

RESULTS

There is negligible risk for feed-based transmission of a transmissible spongiform encephalopathy, Trichinella spiralis, Toxoplasma gondii, Salmonella Choleraesuis, Salmonella spp. except Choleraesuis and I 4,[5],12:i:-, porcine deltacoronavirus, Senecavirus A, mammalian orthoreovirus 3, foot and mouth disease virus, classical swine fever virus or Chinese pseudorabies virus. However, the combined severity and probability of Salmonella enterica serotype I 4,[5],12:i:-, porcine epidemic diarrhoea virus and African swine fever virus warrant a moderate risk characterization for transmission through the US feed supply chain.

CONCLUSIONS

This risk can be maintained below critical status by minimizing the likelihood that a pathogen can enter the feed supply chain, such as by excluding high-risk ingredients from facilities, extending biosecurity to mills, and considering proactive mitigation strategies. In reality, all these actions may be necessary to prevent the detrimental transmission of porcine biological hazards into the US swine herd through the feed supply chain.

Characterization of Salmonella enterica Isolates from Selected U.S. Swine Feed Mills by Whole-Genome Sequencing

Every year salmonellosis is responsible for $2.3 billion in costs to the U.S. food industry, with nearly 6% of the reported cases associated with pork and/or pork products. Several studies have demonstrated the role of pigs as Salmonella reservoirs. Furthermore, this pathogen has been identified as a potential biological hazard in many livestock feeds. The overall objective of this research was to characterize Salmonella enterica isolates in selected U.S. swine feed mills by whole-genome sequencing (WGS) and evaluate isolates in association with the season and feed production stages. Salmonella isolates were collected from 11 facilities during a previous study. Samples were analyzed for Salmonella prevalence following the U.S. Department of Agriculture guidelines and confirmed by PCR. WGS was carried out on either the MiSeq or NextSeq sequencer. De novo genome assemblies were obtained with the Shovill pipeline, version 0.9. ResFinder and SPIFinder were used to identify antibiotic resistance genes and pathogenicity islands. Finally, their phylogenetic relationship and diversity were determined by core genome multilocus sequence typing. Overall, our analysis showed the presence of S. enterica in the feed mill environment. Isolates belonged to 16 different serotypes. Salmonella Agona, Salmonella Mbandaka, Salmonella Senfenberg, and Salmonella Scharzengrund were the most frequently found, and 18 single-nucleotide polymorphism clusters were identified. In silico analysis showed that 40% of the strains carried at least one antimicrobial resistance gene. All isolates in this study could be considered of public health concern and pathogenic potential. Our findings underscore the potential role of the feed mill environment as the pathogen entry route into the human food value chain.

Multi-Laboratory Validation of a Loop-Mediated Isothermal Amplification Method for Screening Salmonella in Animal Food

Loop-mediated isothermal amplification (LAMP) has gained wide popularity in the detection of Salmonella in foods owing to its simplicity, rapidity, and robustness. This multi-laboratory validation (MLV) study aimed to validate a Salmonella LAMP-based method against the United States Food and Drug Administration (FDA) Bacteriological Analytical Manual (BAM) Chapter 5 Salmonella reference method in a representative animal food matrix (dry dog food). Fourteen independent collaborators from seven laboratories in the United States and Canada participated in the study. Each collaborator received two sets of 24 blind-coded dry dog food samples (eight uninoculated; eight inoculated at a low level, 0.65 MPN/25 g; and eight inoculated at a high level, 3.01 MPN/25 g) and initiated the testing on the same day. The MLV study used an unpaired design where different test portions were analyzed by the LAMP and BAM methods using different preenrichment protocols (buffered peptone water for LAMP and lactose broth for BAM). All LAMP samples were confirmed by culture using the BAM method. BAM samples were also tested by LAMP following lactose broth preenrichment (paired samples). Statistical analysis was carried out by the probability of detection (POD) per AOAC guidelines and by a random intercept logistic regression model. Overall, no significant differences in POD between the Salmonella LAMP and BAM methods were observed with either unpaired or paired samples, indicating the methods were comparable. LAMP testing following preenrichment in buffered peptone water or lactose broth also resulted in insignificant POD differences (P > 0.05). The MLV study strongly supports the utility and applicability of this rapid and reliable LAMP method in routine regulatory screening of Salmonella in animal food.

Modulation of the Immune Response to Improve Health and Reduce Foodborne Pathogens in Poultry

Salmonella and Campylobacter are the two leading causes of bacterial-induced foodborne illness in the US. Food production animals including cattle, swine, and chickens are transmission sources for both pathogens. The number of Salmonella outbreaks attributed to poultry has decreased. However, the same cannot be said for Campylobacter where 50⁻70% of human cases result from poultry products. The poultry industry selects heavily on performance traits which adversely affects immune competence. Despite increasing demand for poultry, regulations and public outcry resulted in the ban of antibiotic growth promoters, pressuring the industry to find alternatives to manage flock health. One approach is to incorporate a program that naturally enhances/modulates the bird's immune response. Immunomodulation of the immune system can be achieved using a targeted dietary supplementation and/or feed additive to alter immune function. Science-based modulation of the immune system targets ways to reduce inflammation, boost a weakened response, manage gut health, and provide an alternative approach to prevent disease and control foodborne pathogens when conventional methods are not efficacious or not available. The role of immunomodulation is just one aspect of an integrated, coordinated approach to produce healthy birds that are also safe and wholesome products for consumers.

Salmonella control in poultry flocks and its public health impact

An increase in confirmed human salmonellosis cases in the EU after 2014 triggered investigation of contributory factors and control options in poultry production. Reconsideration of the five current target serovars for breeding hens showed that there is justification for retaining Salmonella Enteritidis, Salmonella Typhimurium (including monophasic variants) and Salmonella Infantis, while Salmonella Virchow and Salmonella Hadar could be replaced by Salmonella Kentucky and either Salmonella Heidelberg, Salmonella Thompson or a variable serovar in national prevalence targets. However, a target that incorporates all serovars is expected to be more effective as the most relevant serovars in breeding flocks vary between Member State (MS) and over time. Achievement of a 1% target for the current target serovars in laying hen flocks is estimated to be reduced by 254,400 CrI95[98,540; 602,700] compared to the situation in 2016. This translates to a reduction of 53.4% CrI95[39.1; 65.7] considering the layer-associated human salmonellosis true cases and 6.2% considering the overall human salmonellosis true cases in the 23 MSs included in attribution modelling. A review of risk factors for Salmonella in laying hens revealed that overall evidence points to a lower occurrence in non-cage compared to cage systems. A conclusion on the effect of outdoor access or impact of the shift from conventional to enriched cages could not be reached. A similar review for broiler chickens concluded that the evidence that outdoor access affects the occurrence of Salmonella is inconclusive. There is conclusive evidence that an increased stocking density, larger farms and stress result in increased occurrence, persistence and spread of Salmonella in laying hen flocks. Based on scientific evidence, an impact of Salmonella control programmes, apart from general hygiene procedures, on the prevalence of Campylobacter in broiler flocks at the holding and on broiler meat at the end of the slaughter process is not expected.

Draft Genome Sequences of 57 Salmonella enterica Strains from Selected U.S. Swine Feed Mills

The number of Salmonella infection cases linked to pork products has increased. Pathogen presence in the feed mill environment is one of the many potential transmission routes into the food production chain.

The number of Salmonella infection cases linked to pork products has increased. Pathogen presence in the feed mill environment is one of the many potential transmission routes into the food production chain. Here, we describe the draft genome sequences of 57 Salmonella enterica isolates from selected U.S. swine feed mills.

Evaluation of Salmonella presence in selected United States feed mills

Salmonella is a pathogen of public health concern. Each year, Salmonella infections cost to the food industry approximately $2.3 billion and 33% of the reported cases are associated with beef, poultry, or pork. Pathogen presence in feed mills can represent one of the many potential routes for entry and transmission into the food production chain. Nevertheless, little is known about Salmonella incidence and association with these types of environments. The objective of this study was to investigate Salmonella presence in different feed mills across the United States. Eleven facilities were selected in eight states and 12 sites were sampled within each feed mill. Samples were analyzed following the FSIS guidelines for isolation and identification of Salmonella. Positive isolates were further investigated by a PCR analysis targeting the invA gene to differentiate for Salmonella enterica. The total number of environmental samples collected was 237: 66% resulted culture positive and 13.1% were PCR positive. All sampled feed mills had at least one culture positive site and following production flow the number of positive samples decreased from ingredient receiving to final product. These preliminary results demonstrate the presence of Salmonella in selected United States feed mills and suggest their potential role as vehicle for pathogen transmission and spread into the food production chain.