Salmonella and broiler processing in the United States: Relationship to foodborne salmonellosis

Co-exposure to polyethylene fiber and Salmonella enterica serovar Typhimurium alters microbiome and metabolome of in vitro chicken cecal mesocosms

Humans and animals encounter a summation of exposures during their lifetime (the exposome). In recent years, the scope of the exposome has begun to include microplastics. Microplastics (MPs) have increasingly been found in locations, including in animal gastrointestinal tracts, where there could be an interaction with Salmonella enterica serovar Typhimurium, one of the commonly isolated serovars from processed chicken. However, there is limited knowledge on how gut microbiomes are affected by microplastics and if an effect would be exacerbated by the presence of a pathogen. In this study, we aimed to determine if acute exposure to microplastics in vitro altered the gut microbiome membership and activity. The microbiota response to a 24 h co-exposure to Salmonella enterica serovar Typhimurium and/or low-density polyethylene (PE) microplastics in an in vitro broiler cecal model was determined using 16S rRNA amplicon sequencing (Illumina) and untargeted metabolomics. Community sequencing results indicated that PE fiber with and without S. Typhimurium yielded a lower Firmicutes/Bacteroides ratio compared with other treatment groups, which is associated with poor gut health, and overall had greater changes to the cecal microbial community composition. However, changes in the total metabolome were primarily driven by the presence of S. Typhimurium. Additionally, the co-exposure to PE fiber and S. Typhimurium caused greater cecal microbial community and metabolome changes than either exposure alone. Our results indicate that polymer shape is an important factor in effects resulting from exposure. It also demonstrates that microplastic-pathogen interactions cause metabolic alterations to the chicken cecal microbiome in an in vitro chicken cecal mesocosm.

IMPORTANCE

Researching the exposome, a summation of exposure to one's lifespan, will aid in determining the environmental factors that contribute to disease states. There is an emerging concern that microplastic-pathogen interactions in the gastrointestinal tract of broiler chickens may lead to an increase in Salmonella infection across flocks and eventually increased incidence of human salmonellosis cases. In this research article, we elucidated the effects of acute co-exposure to polyethylene microplastics and Salmonella enterica serovar Typhimurium on the ceca microbial community in vitro. Salmonella presence caused strong shifts in the cecal metabolome but not the microbiome. The inverse was true for polyethylene fiber. Polyethylene powder had almost no effect. The co-exposure had worse effects than either alone. This demonstrates that exposure effects to the gut microbial community are contaminant-specific. When combined, the interactions between exposures exacerbate changes to the gut environment, necessitating future experiments studying low-dose chronic exposure effects with in vivo model systems.

Colonization, spread and persistence of Salmonella (Typhimurium, Infantis and Reading) in internal organs of broilers

Transfer of Salmonella to internal organs of broilers over a 35 d grow-out period was evaluated. A total of 360 one-day old chicks were placed in 18 floor pens of 3 groups with 6 replicate pens each. On d 0, broilers were orally challenged with a cocktail of Salmonella (equal population of marked serovars; nalidixic acid-resistant S. Typhimurium, rifampicin-resistant S. Infantis, and kanamycin-resistant S. Reading) to have 3 groups: L (low; ∼2 log CFU/bird); M (medium; ∼5 log CFU/bird); and H (High; ∼8 log CFU/bird). On d 2, 7 and 35, 4 birds/pen were euthanized and ceca, liver, and spleen samples were collected aseptically. Gizzard samples (4/pen) were collected on d 35. The concentration of Salmonella in liver and spleen were transformed to binary outcomes (positive and negative) and fitted in glm function of R using cecal Salmonella concentrations (log CFU/g) and inoculation doses (L, M, and H) as inputs. On d 2, H group showed greater (P ≤ 0.05) cecal colonization of all 3 serovars compared to L and M groups. However, M group showed greater (P ≤ 0.05) colonization of all 3 serovars in the liver and spleen compared to L group. Salmonella colonization increased linearly in the ceca and quadratically in the liver and spleen with increasing challenge dose (P ≤ 0.05). On d 35, L group had greater (P ≤ 0.05) S. Infantis colonization in the ceca and liver compared to M and H groups (P ≤ 0.05). Moreover, within each group on d 35, the concentration of S. Reading was greater than those of S. Typhimurium and S. Infantis for all 3 doses in the ceca and high dose in the liver and gizzard (P ≤ 0.05). Salmonella colonization diminished in the ceca, liver, and spleen during grow-out from d 0 to d 35 (P ≤ 0.05). On d 35, birds challenged with different doses of Salmonella cocktail showed a similar total Salmonella spp. population in the ceca (ca. 3.14 log CFU/g), liver (ca. 0.54 log CFU/g), spleen (ca. 0.31 log CFU/g), and gizzard (ca. 0.42 log CFU/g). Estimates from the fitted logistic model showed that one log CFU/g increase in cecal Salmonella concentration will result in an increase in relative risk of liver and spleen being Salmonella-positive by 4.02 and 3.40 times (P ≤ 0.01), respectively. Broilers from H or M group had a lower risk (28 and 23%) of being Salmonella-positive in the liver compared to the L group when the cecal Salmonella concentration is the same (P ≤ 0.05). Oral challenge of broilers with Salmonella spp. with various doses resulted in linear or quadratic increases in Salmonella colonization in the internal organs during early age and these populations decreased during grow-out (d 35). This research can provide guidance on practices to effectively mitigate the risk of Salmonella from chicken parts and enhance public health.

Mitigating the attachment of Salmonella Infantis on isolated poultry skin with cetylpyridinium chloride

To provide the poultry industry with effective mitigation strategies, the effects of cetylpyridinium chloride (CPC) on the reduction of Salmonella Infantis, hilA expression, and chicken skin microbiota were evaluated. Chicken breast skins (4×4 cm; N = 100, n = 10, k = 5) were inoculated with Salmonella (Typhimurium or Infantis) at 4°C (30min) to obtain 108 CFU/g attachment. Skins were shaken (30s), with remaining bacteria being considered firmly attached. Treatments were applied as 30s dips in 50 mL: no inocula-no-treatment control (NINTC), no treatment control (NTC), tap water (TW), TW+600 ppm PAA (PAA), or TW+0.5% CPC (CPC). Excess fluid was shaken off (30s). Samples were homogenized in nBPW (1 min). Samples were discarded. Salmonella was enumerated and Log10 transformed. Reverse transcriptase-qPCR (rt-qPCR) was performed targeting hilA gene and normalized using the 2-ΔΔCt method. Data were analyzed using one-way ANOVA in RStudio with means separated by Tukey's HSD (P≤0.05). Genomic DNA of rinsates was extracted, 16S rRNA gene (V4) was sequenced (MiSeq), and data analyzed in QIIME2 (P≤0.05 and Q≤0.05). CPC and PAA affected Salmonella levels differently with CPC being effective against S. Infantis compared to TW (P<0.05). Treatment with CPC on S. Infantis-infected skin altered the hilA expression compared to TW (P<0.05). When inoculated with S. Typhimurium, there was no difference between the microbiota diversity of skins treated with PAA and CPC; however, when inoculated with S. Infantis, there was a difference in the Shannon's Entropy and Jaccard Dissimilarity between the two treatments (P<0.05). Using ANCOM at the genus level, Brochothrix was significant (W = 118) among skin inoculated with S. Typhimurium. Among S. Infantis inoculated, Yersiniaceae, Enterobacterales, Lachnospiraceae CHKCI001, Clostridia vadinBB60 group, Leuconostoc, Campylobacter, and bacteria were significant (408). CPC and PAA-treated skins had lowest relative abundance of the genera. In conclusion, CPC mitigated Salmonella Infantis, altered hilA expression, and influenced the chicken skin microbiota.

Regulating effects of chlorinated drinking water on cecal microbiota of broiler chicks

In this study, 2 types of drinking water were provided to broiler chicks to evaluate the relationship between the bacterial load of drinking water and cecal microbiota. One type of drinking water was untreated, while the other type was daily treated with sodium dichlorocyanurate (50 mg/L). A total of 240 broiler chicks were divided into 2 groups based on their initial body weight. There were 6 replicates in each group, and each replicate cage contained 20 birds. Each cage was assigned to a different floor of the battery cage. On the final day, water samples were collected from each replicate cage at the opening of the drinking cup height, and one bird was selected from each replicate cage to obtain cecal content samples for measuring microbiota composition using the 16S rRNA technique. We found that drinking water treated with sodium dichlorocyanurate significantly reduced the richness and diversity of microbiota and diminished/disappeared most gram-negative bacteria. Broiler chicks that consumed chlorinated drinking water exhibited changes in the composition of cecal microbiota, with Alistipes serving as the marker species in the cecal content of broiler chicks that consumed untreated water, whereas AF12 served as the marker species in the cecal content of broiler chicks that consumed chlorinated drinking water. Functional prediction using the MetaCyc database and species composition analysis of metabolic pathways showed that changes in 7 metabolic pathways were related to the abundance of Providencia. Therefore, we concluded that chlorinated drinking water reduced the bacterial load in drinking water, thereby altering the cecal microbiota composition and regulating the metabolic activity of broiler chicks.

Co-exposure to Polyethylene Fiber and Salmonella enterica Typhimurium Alters Microbiome and Metabolome of in vitro Chicken Cecal Mesocosms

Humans and animals encounter a summation of exposures during their lifetime (the exposome). In recent years, the scope of the exposome has begun to include microplastics. Microplastics (MPs) have increasingly been found in locations where there could be an interaction with Salmonella enterica Typhimurium, one of the commonly isolated serovars from processed chicken. In this study, the microbiota response to a 24-hour co-exposure to Salmonella enterica Typhimurium and/or low-density polyethylene (PE) microplastics in an in vitro broiler cecal model was determined using 16S rRNA amplicon sequencing (Illumina) and untargeted metabolomics. Community sequencing results indicated that PE fiber with and without S. Typhimurium yielded a lower Firmicutes/Bacteroides ratio compared to other treatment groups, which is associated with poor gut health, and overall had greater changes to the cecal microbial community composition. However, changes in the total metabolome were primarily driven by the presence of S. Typhimurium. Additionally, the co-exposure to PE Fiber and S. Typhimurium caused greater cecal microbial community and metabolome changes than either exposure alone. Our results indicate that polymer shape is an important factor in effects resulting from exposure. It also demonstrates that microplastic-pathogen interactions cause metabolic alterations to the chicken cecal microbiome in an in vitro chicken cecal model.

The effect of emulsifier type and oil fraction on Salmonella Typhimurium growth and thermal inactivation in oil-in-water emulsion

High water activity oil-in-water emulsions can promote survival and growth of Salmonella Typhimurium. Nevertheless, the precise effect of emulsifier type and oil content on bacterial growth and inactivation is not fully understood. Here, emulsions were prepared using different emulsifiers (Tween 20, Tween 80, and Triton X-100) and different oil fractions (20%, 40%, and 60% (v/v)). TSB (control), emulsifier solutions, and emulsions were inoculated with S. Typhimurium. Bacterial growth rate was measured at 7, 22, and 37°C, whereas thermal inactivation was performed at 55°C. Growth and inactivation data was fitted into Logistic and Weibull models, respectively. At an incubation temperature of 37°C, the presence of high amount of oil (60%) in Tween 20 and Triton X stabilized emulsions extended the lag phase (5.83 ± 2.20 and 9.43 ± 1.07 h, respectively, compared to 2.28 ± 1.54 h for TSB, p < 0.05), whereas individual emulsifiers had no effect on growth behavior compared to TSB. This effect was also prevalent but attenuated at 22°C, whereas no growth was observed at 7°C. In thermal inactivation, we observed protective effect in Tween 80 and Triton X-100 solutions, where time required for five-log reduction was 1914.70 ± 706.35 min and 795.34 ± 420.09 min, respectively, compared to 203.89 ± 10.18 min for TSB (p < 0.05). Interestingly, the presence of high amount of oil did not offer protective effect during thermal inactivation. We hypothesize that oleic acid in Tween 80 and lower hydrophobicity value of Triton X-100 help maintain membrane integrity and improve the resistance of bacteria to heat inactivation.

Comparison of peroxyacetic acid and acidified sodium chlorite at reducing natural microbial contamination on chicken meat pieces

The spin-chill process at poultry processing plants involves the immersion of chicken carcasses in cold water (<5°C) often containing sodium hypochlorite which significantly contributes to the reduction of bacterial loads. Cutting carcasses into pieces, however, has been linked with increases in Campylobacter and Salmonella counts. Here, the efficacy of PAA and ASC on reducing bacteria on skin-on, bone-in thigh cuts was investigated. Three concentrations of ASC (60, 112, and 225 ppm) and PAA (50, 75, 100 ppm) were used. Thighs were dipped into sanitizer and tested for total viable bacterial counts, Campylobacter load, and prevalence of Salmonella. The efficacy of PAA and ASC was also compared with chlorine (8 ppm). All sanitizers exhibited a greater log reduction compared with water. PAA at both 75 and 100 ppm resulted in significantly higher log reductions compared with the water only. PAA at 100 ppm and 225 ppm ASC were the most effective at reducing Campylobacter. All wash treatments reduced the proportion of Salmonella positive samples, but the greatest reduction was observed for 225 ppm ASC. Both concentrations of ASC resulted in a greater reduction in total viable counts compared with chlorine.

Dietary protocatechuic acid ameliorates ileal mucosal barrier injury and inflammatory response and improves intestinal microbiota composition in Yellow chickens challenged with Salmonella typhimurium

Salmonella typhimurium (ST) is a common foodborne pathogen that severely affects the health of humans and livestock. Protocatechuic acid (PCA) has been shown to possess anti-inflammatory and anti-bacterial functions. Chickens were used to investigate the effect of PCA on the gut health infected with ST. A total of one hundred eighty, 1-d-old birds were randomly allocated into 3 treatments, each with 6 replicates per treatment and 10 chicks per replicate. Broiler chicks in the control and ST treatment were fed a basal diet, and birds in the PCA+ST treatment received the basal diet with 600 mg/kg PCA. On d 14 and 16 of the trial, broilers in ST and PCA+ST treatments received an oral dose of ST, while broilers in CON received an equal amount of PBS. The data were analyzed by the one-way ANOVA. Dietary PCA increased (P < 0.05) final body weight, average daily gain, and feed to gain ratio in ST-challenged Yellow broilers. Protocatechuic acid significantly alleviated ST-induced intestinal mucosal injury reflected in the decreased (P < 0.05) plasma activity of diamine oxidase and ileal apoptosis, with increased (P < 0.05) ileal villus height and villus height/crypt depth. Protocatechuic acid treatment significantly decreased (P < 0.05) ST-induced proinflammatory cytokine (Interleukin-1β, Interleukin-6, Tumor necrosis factor-α, and Interferon-β) content in ileum. Meanwhile, PCA treatment significantly increased (P < 0.05) the transcript abundances of claudin 1 (CLDN1), zonula occludens-1 (ZO-1), and mucin 2 (MUC2) in ileum, all related to the intestinal barrier in ST-challenged Yellow broilers. Additionally, PCA also increased (P < 0.05) the diversity and richness of the cecal microflora as reflected by reduced (P < 0.05) abundance of Bacteroidota, Proteobacteria and Escherichia-Shigella, and increased (P < 0.05) abundance of Firmicutes and Lactobacillus in ST-challenged Yellow broilers. These findings indicate that PCA relieves ST-induced loss weight, intestinal barrier injury, inflammatory response, and improves intestinal microbiota composition in Yellow broilers.

Ileal and cecal microbiota response to Salmonella Typhimurium challenge in conventional and slow-growing broilers

Despite the negative impacts of Salmonella intestinal colonization on human health, Salmonella is a natural colonizer of the gastrointestinal tract and is not overtly pathogenic to the avian host. It is of interest to understand the impacts and colonization rates of Salmonella across selected genetic lines such as slow-growing (SG) and conventional (CONV) broilers. The objective of this study was to characterize the relationship between Salmonella enterica serovar Typhimurium challenge and selected broiler genetic lines on the ileal and cecal microbiome. Male chicks of two broiler breeds (n = 156/breed) were cohoused in an open floor pen until day 7. On day 13, the chicks were then separated into 12 isolators per breed (4 rooms, 6 isolators/room, 11 chicks/isolator). On day 14, chicks in the 12 treatment isolators (6 isolators/breed, 108 total) were challenged with Salmonella Typhimurium (ST) (1 × 108 CFU/ml) via oral gavage while the remaining chicks (n = 108) were given an oral gavage of sterile tryptic soy broth control (C). Ileal and cecal contents were collected on day 7 from 24 chicks of each breed, and on days 13, 17, 21, and 24 from two chicks per isolator. Samples underwent DNA extraction and PCR amplification to obtain 16S rRNA amplicons that were sequenced with Illumina MiSeq. Salmonella Typhimurium colonization in the cecum was not different in the two broiler breeds. The main effect of breed had the greatest impact on the ileum microbiota of broilers 7 days of age where SG broilers had significantly lower diversity and richness compared to CONV broilers (p < 0.05). Salmonella Typhimurium challenge consistently caused a change in beta diversity. Regardless of day or intestinal location, challenged broilers had many amplicon sequence variants (ASVs) with decreased abundance of likely beneficial bacteria such as Mollicutes RF39, Shuttleworthia, Flavonifractor, and Oscillibacter compared to broilers that were unchallenged with Salmonella Typhimurium (p < 0.05). Additionally, there was a difference in the timing of when the microbiota alpha and beta diversity of each breed responded to Salmonella Typhimurium challenge. Thus, both broiler breed and Salmonella Typhimurium can impact the intestinal microbiota.

Establishing farm dust as a useful viral metagenomic surveillance matrix

Farm animals may harbor viral pathogens, some with zoonotic potential which can possibly cause severe clinical outcomes in animals and humans. Documenting the viral content of dust may provide information on the potential sources and movement of viruses. Here, we describe a dust sequencing strategy that provides detailed viral sequence characterization from farm dust samples and use this method to document the virus communities from chicken farm dust samples and paired feces collected from the same broiler farms in the Netherlands. From the sequencing data, Parvoviridae and Picornaviridae were the most frequently found virus families, detected in 85-100% of all fecal and dust samples with a large genomic diversity identified from the Picornaviridae. Sequences from the Caliciviridae and Astroviridae familes were also obtained. This study provides a unique characterization of virus communities in farmed chickens and paired farm dust samples and our sequencing methodology enabled the recovery of viral genome sequences from farm dust, providing important tracking details for virus movement between livestock animals and their farm environment. This study serves as a proof of concept supporting dust sampling to be used in viral metagenomic surveillance.

The Prevalence of Salmonella and Campylobacter on Broiler Meat at Different Stages of Commercial Poultry Processing

In poultry processing, Salmonella and Campylobacter contaminations are major food safety concerns. Peracetic acid (PAA) is an antimicrobial commonly used in commercial poultry processing to reduce pathogen prevalence so as to meet the USDA-FSIS performance standards. The objective of this study was to determine the prevalence of Salmonella and Campylobacter on broiler meat in various steps of commercial poultry processing in plants that use PAA. Post-pick, pre-chill, post-chill, and drumstick chicken samples were collected from three processing plants and mechanically deboned meat (MDM) was collected from two of the three plants. Each plant was sampled thrice, and 10 samples were collected from each processing step during each visit. Among the 420 samples, 79 were contaminated with Salmonella and 155 were contaminated with Campylobacter. Salmonella and Campylobacter contamination on the post-pick samples averaged 32.2%. Significant reductions in Salmonella and Campylobacter were observed in pre-chill to post-chill samples, where the prevalence was reduced from 34% and 64.4% to nondetectable limits and 1.1%, respectively (p < 0.001). Salmonella and Campylobacter remained undetectable on the drumstick samples in all three processing plants. However, the prevalence of Salmonella and Campylobacter on MDM was similar to the post-pick prevalence, which suggests substantial cross-contamination from post-chill to MDM.

Capsaicin Potently Blocks Salmonella typhimurium Invasion of Vero Cells

Salmonella typhimurium (S. typhimurium) is one of the major food and waterborne bacteria that causes several health outbreaks in the world. Although there are few antibiotics against this bacterium, some of these drugs are challenged with resistance and toxicity. To mitigate this challenge, our group explored the ethnomedicinal/herbalism knowledge about a certain spice used in Northern Ghana in West Africa against bacterial and viral infection. This plant is Capsicum chinense (C. chinense). The plant is one of the commonest food spices consumed across the world. The seed of the plant contains both capsaicin and dihydrocapsaicin. Apart from capsaicin and dihydrocapsaicin, other major capsaicinoids in C. chinense include nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin. In this pilot work, we investigated the antibacterial activity of pure capsaicin and capsaicin extract obtained from C. chinense against S. typhimurium in vitro. Capsaicin extract showed potent inhibition of S. typhimurium growth at concentrations as low as 100 ng/mL, whereas pure capsaicin comparatively showed poorer inhibition of bacteria growth at such a concentration. Interestingly, both capsaicin extract and pure capsaicin were found to potently block a S. typhimurium invasion of the Vero cell in vitro. Taken together, we believed that capsaicin might work synergistically with dihydrocapsaicin or the other capsaicinoids to inhibit S. typhimurium growth, whereas individually, capsaicin or dihydrocapsaicin could potently block the bacteria entry and invasion of Vero cells.

Synergistic interaction of tap water-based neutral electrolyzed water combined with UVA irradiation to enhance microbial inactivation on stainless steel

As an emerging electrolyzed water (EW) technology, tap water-based neutral electrolyzed water (TNEW) is an attractive alternative to other types of conventional EW for sterilization of food contact surfaces. In this study, we sought to identify strategies for improving TNEW inactivation efficiencies of major foodborne pathogenic bacteria. We investigated the synergistic antimicrobial effect of TNEW and ultraviolet-A light (UVA) combination treatment against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on stainless steel. The data confirmed that simultaneous TNEW and UVA treatment for 60 min reduced E. coli O157:H7, S. Typhimurium, and L. monocytogenes population by 2.15, 1.55, and 2.65 log CFU/cm², respectively. The synergistic cell count reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes in the combination treatment group were 1.17, 0.59, and 1.62 log units, respectively. Additionally, the mechanisms of the synergistic bactericidal effects of TNEW and UVA were identified through several approaches. Mechanistic investigations suggested that the synergistic effect was associated with intracellular reactive oxygen species generation, bacterial cell membrane damage, and inactivation of dehydrogenase. These findings demonstrate that treatment with TNEW and UVA light can enhance the microbiological safety of food contact surfaces during food processing.

Growth of Salmonella Enteritidis in the presence of quorum sensing signaling compounds produced by Pseudomonas aeruginosa

Quorum sensing (QS) can exist in food-related bacteria and potentially affect bacterial growth through acyl-homoserine lactones (AHLs). To verify the role of QS compounds in the cell-free supernatant, this study examined the effect of supernatant extracted from Pseudomonas aeruginosa culture on the growth kinetics of Salmonella Enteritidis. The results showed that the lag time (λ) of S. Enteritidis was apparently reduced (p < 0.05) under the influence of P. aeruginosa culture supernatant compared with the S. Enteritidis culture supernatant. HPLC-MS/MS test demonstrated that AHLs secreted by P. aeruginosa were mainly C14-HSL with a content of 85.71 μg/mL and a small amount of 3-oxo-C12-HSL. In addition, the commercially synthetic C14-HSL had positive effects on the growth of S. Enteritidis, confirming once again that the growth of S. Enteritidis was affected by AHL metabolized by other bacteria and the complexity of bacterial communication.

Prevalence and risk factors for Salmonella spp. contamination of slaughtered chickens in Taiwan

The present study was designed to estimate the prevalence of Salmonella contamination in Taiwanese broilers at slaughter and to identify risk factors associated with the presence of Salmonella in processed batches of broilers. Carcass rinse samples from 362 batches of broilers were collected from 45 chicken abattoirs in Taiwan between February 2013 and November 2014. Univariate analyses and multivariable logistic regression analyses were conducted to identify putative risk factors for contamination. Salmonella was detected in 32.6 % (95 % CI: 30.4-34.8) of individual broilers and 56.4 % (95 % CI: 51.1-61.5) of the sampled batches. The multivariable logistic regression model identified season (July to November) (OR = 1.95; 95 % CI: 1.2-3.2) as increasing the risk of infection. Abattoirs in the southern region (Taichung and Kaohsiung) (OR = 0.45; 95 % CI: 0.3-0.8); batches scalded for > 90 s (OR = 0.2; 95 % CI: 0.1-0.3) and batches of commercial white broilers (BR) (OR = 0.21; 95 % CI: 0.1-0.4) all had a decreased risk of contamination compared to abattoirs from the northern region, scalding < 90 s and Taiwan native chickens (TNC), respectively. This study highlights the influence of environmental conditions and poultry breed on the risk of Salmonella contamination of chickens during slaughter.

Reduction of Salmonella Infantis on skin-on, bone-in chicken thighs by cetylpyridinium chloride application and the impact on the skin microbiota

Salmonella Infantis has been the etiological agent of numerous foodborne outbreaks of nontyphoidal Salmonella. Consequently, there is an emergent need to mitigate Salmonella Infantis among poultry. Thus, this study evaluated the efficacy of cetylpyridinium chloride (CPC) versus peroxyacetic acid (PAA), on bone-in, skin-on chicken thighs for the reduction of Salmonella and changes in the microbiota. Exactly 100 skin-on, bone-in chicken thighs (2 trials, 0 and 24 h, k = 5, n = 5, N = 50) were inoculated with 10⁸ CFU/mL of a nalidixic acid resistant strain of S. Infantis for an attachment of 10⁶ CFU/g. Thighs were treated with 20 s part dips (350 mL): a no inoculum, no treatment control (NINTC); no treatment control (NTC); tap water (TW); TW+CPC; TW+PAA. Following treatment, thighs were rinsed in 150 mL of nBPW, and rinsates were collected. Rinsates were spot plated for Salmonella and aerobic bacteria (APC). Log₁₀ transformed counts were analyzed using a mixed-effects model (random effect = trial) with means separated using Tukey's HSD (P ≤ 0.05). The genomic DNA of rinsates was extracted, and the 16S rDNA was sequenced on an Illumina MiSeq. Microbiota data were analyzed using QIIME2, with data considered significant at P ≤ 0.05 (main effects) and Q≤0.05 (pairwise differences). Treatment × time interactions were observed for both Salmonella and APC (P < 0.05). The treatment of thighs with PAA and CPC reduced Salmonella and APC in respect to the controls. Numerically, thighs treated with CPC had less Salmonella (4.29 log₁₀CFU/g) and less APC (4.56 log₁₀CFU/g) at 24 h than all other treatments (P > 0.05). Differences in diversity metrics were not consistently observed between treatments; however, in trial 2, the NTC treated thighs were different than those treated with CPC (P < 0.05; Q < 0.05). In both trials, ANCOM, the analysis of microbiome compositional profiles, revealed shifts at both the phylum and order levels with thighs being different in the relative abundances of Proteobacteria (P < 0.05). In conclusion, treatment of skin-on poultry parts with CPC may reduce the risk of foodborne outbreaks caused by Salmonella Infantis.

Glycyrrhizin Attenuates Salmonella Typhimurium-Induced Tissue Injury, Inflammatory Response, and Intestinal Dysbiosis in C57BL/6 Mice

Salmonellae are one of the most important foodborne pathogens, which threaten the health of humans and animals severely. Glycyrrhizin (GL) has been proven to exhibit anti-inflammatory and tissue-protective properties. Here, we investigated the effects of GL on tissue injury, inflammatory response, and intestinal dysbiosis in Salmonella Typhimurium-infected mice. Results showed that GL or gentamicin (GM) significantly (P < 0.05) alleviated ST-induced splenomegaly indicated by the decreased spleen index, injury of liver and jejunum indicated by the decreased hepatocytic apoptosis, and the increased jejunal villous height. GL significantly (P < 0.05) increased secretion of inflammatory cytokines (IFN-γ, IL-12p70, IL-6, and IL-10) in spleen and IL-12p40 mRNA expression in liver. Meanwhile, GL or GM pre-infection treatments significantly (P < 0.05) decreased ST-induced pro-inflammatory cytokine (IFN-γ, TNF-α, and IL-6) expression in both spleen and liver and increased (P < 0.05) anti-inflammatory cytokine IL-10 secretion in spleen. Furthermore, GL or GM pre-infection treatment also regulates the diversities and compositions of intestinal microbiota and decreased the negative connection among the intestinal microbes in ST-infected mice. The above findings indicate that GL alleviates ST-induced splenomegaly, hepatocytic apoptosis, injury of jejunum and liver, inflammatory response of liver and spleen, and intestinal dysbacteriosis in mice.

Evaluation of curcumin and copper acetate against Salmonella Typhimurium infection, intestinal permeability, and cecal microbiota composition in broiler chickens

BACKGROUND

Interest in the use of natural feed additives as an alternative to antimicrobials in the poultry industry has increased in recent years because of the risk of bacterial resistance. One of the most studied groups are polyphenolic compounds, given their advantages over other types of additives and their easy potentiation of effects when complexes are formed with metal ions. Therefore, the objective of the present study was to evaluate the impact of dietary supplementation of copper acetate (CA), curcumin (CR), and their combination (CA-CR) against Salmonella Typhimurium colonization, intestinal permeability, and cecal microbiota composition in broiler chickens through a laboratory Salmonella infection model. S. Typhimurium recovery was determined on day 10 post-challenge by isolating Salmonella in homogenates of the right cecal tonsil (12 chickens per group) on Xylose Lysine Tergitol-4 (XLT-4) with novobiocin and nalidixic acid. Intestinal integrity was indirectly determined by the fluorometric measurement of fluorescein isothiocyanate dextran (FITC-d) in serum samples from blood obtained on d 10 post-S. Typhimurium challenge. Finally, microbiota analysis was performed using the content of the left caecal tonsil of 5 chickens per group by sequencing V4 region of 16S rRNA gene.

RESULTS

The results showed that in two independent studies, all experimental treatments were able to significantly reduce the S. Typhimurium colonization in cecal tonsils (CT, P < 0.0001) compared to the positive control (PC) group. However, only CA-CR was the most effective treatment in reducing S. Typhimurium counts in both independent studies. Furthermore, the serum fluorescein isothiocyanate dextran (FITC-d) concentration in chickens treated with CR was significantly lower when compared to PC (P = 0.0084), which is related to a decrease in intestinal permeability and therefore intestinal integrity. The effect of dietary treatments in reducing Salmonella was further supported by the analysis of 16S rRNA gene sequences using Linear discriminant analysis effect size (LEfSe) since Salmonella was significantly enriched in PC group (LDA score > 2.0 and P < 0.05) compared to other groups. In addition, Coprobacillus, Eubacterium, and Clostridium were significantly higher in the PC group compared to other treatment groups. On the contrary, Fecalibacterium and Enterococcus in CR, unknown genus of Erysipelotrichaceae at CA-CR, and unknown genus of Lachnospiraceae at CA were significantly more abundant respectively.

CONCLUSIONS

CR treatment was the most effective treatment to reduce S. Typhimurium intestinal colonization and maintain better intestinal homeostasis which might be achieved through modulation of cecal microbiota.

Salmonella Contamination of Broiler Chicken Carcasses at Critical Steps of the Slaughter Process and in the Environment of Two Slaughter Plants: Prevalence, Genetic Profiles, and Association with the Final Carcass Status

ABSTRACT

Salmonella is a foodborne pathogen commonly associated with poultry products. The aims of this work were to (i) estimate the impact of critical steps of the slaughter process on Salmonella detection from broiler chicken carcasses in two commercial poultry slaughter plants in Quebec, Canada; (ii) investigate the presence of Salmonella in the slaughter plant environment; (iii) describe, using a high-resolution melting (HRM) approach, the HRM Salmonella profiles and serotypes present on carcasses and in the slaughter plant environment; and (iv) evaluate whether the HRM flock status after chilling could be predicted by the flock status at previous steps of the slaughter process, the status of previous flocks, or the status of the processing environment, for the same HRM profile. Eight visits were conducted in each slaughter plant over a 6-month period. In total, 379 carcass rinsates from 79 flocks were collected at five critical steps of the slaughter process. Environmental samples were also collected from seven critical sites in each slaughter plant. The bleeding step was the most contaminated, with >92% positive carcasses. A decrease of the contamination along the slaughtering process was noted, with carcasses sampled after dry-air chilling showing ≤2.5% Salmonella prevalence. The most frequently isolated serotypes were Salmonella Heidelberg, Kentucky, and Schwarzengrund. The detection of the Salmonella Heidelberg 1-1-1 HRM profile on carcasses after chilling was significantly associated with its detection at previous steps of the slaughter process and in previously slaughtered flocks from other farms during a same sampling day. Results highlight the importance of the chilling step in the control of Salmonella on broiler chicken carcasses and the need to further describe and compare the competitive advantage of Salmonella serotypes to survive processing. The current study also illustrates the usefulness of HRM typing in investigating Salmonella contamination along the slaughter process.

HIGHLIGHTS

Dietary Supplementation of Potential Probiotics Bacillus subtilis, Bacillus licheniformis, and Saccharomyces cerevisiae and Synbiotic Improves Growth Performance and Immune Responses by Modulation in Intestinal System in Broiler Chicks Challenged with Salmonella Typhimurium

This study evaluates the effects of probiotics and synbiotics on the performance, immune responses, and intestinal morphology, and the expression of immunity-related genes of broiler chicks challenged with Salmonella typhimurium. Three hundred and sixty broiler chicks were divided into six groups, including broiler chicks challenged and non-challenged with S. typhimurium and fed with probiotic, synbiotic, and basal diet without additive. Growth performance (food intake, daily gain, feed conversion ratio, and mortality), immune responses (antibody titer against sheep red blood cells, immunoglobulins G and M), intestinal morphology, lactic acid bacteria population, and the expression of immunity-related genes (interferon-γ, interleukins 6 and 12, and tumor necrosis factor-α) were investigated. The administration of S. typhimurium decreased growth performance (P = 0.0001), immune responses (P = 0.0001), intestinal morphology (P = 0.0001), lactic acid bacteria population (P = 0.0001), and the expression of immunity-related genes (P = 0.0001) of broiler chickens. However, broiler chicks fed with probiotic (P = 0.001) and synbiotic (P = 0.0001) showed better growth performance, immune responses, intestinal morphology, lactic acid bacteria population, and the expression of immunity-related genes in comparison with infected broiler chicks fed with basal diet lack of probiotic and synbiotic. Feeding probiotics (P = 0.001) and synbiotics (P = 0.0001) showed positive effects for challenged and non-challenged broiler chicks. In sum, feeding synbiotic and probiotic alleviated the negative effects of S. typhimurium on growth and immunity of broiler chicks. It can be suggested to apply synbiotic and probiotics as benefit additive against infectious challenges, such as S. typhimurium.

Application of a Novel Lytic Podoviridae Phage Pu20 for Biological Control of Drug-Resistant Salmonella in Liquid Eggs

Salmonella is a globally distributed zoonotic pathogen. Among them, S. pullorum is a host-specific pathogen that seriously affects the development of the poultry breeding industry in China. It mainly infects chickens and can cause white scabs, and the mortality rate after infection is almost 100%. As antibiotics are widely used in animal feed and other production processes, Salmonella resistance has gradually increased. Therefore, there is an increasing need to develop new technologies to control multi-drug resistant (MDR) pathogens and confirm their actual effectiveness in the target food matrix. Bacteriophage can efficiently and specifically lyse bacteria, and will be a potential bactericide to replace antibiotics. In this study, 34 strains of Salmonella bacteriophages were isolated from environmental resources. Therein, phage Pu20 with the widest host spectrum had the strongest ability to lyse tested Salmonella strains. Further studies showed that Pu20 had high pH tolerance and heat resistance, short incubation period. Pu20 can effectively inhibit the growth of two strains of MDR Salmonella in liquid egg white and yolk at 4 °C and 25 °C, respectively. According to morphological and phylogenetic analysis, Pu20 belongs to the Podoviridae family. Genomic analysis of Pu20 indicates a linear 59435 bp dsDNA sequence with no homology to virulence or antibiotic resistance-related genes. Together, these results sheds light on the potential biocontrol application value of Pu20 in food products.

Strategies to Improve Poultry Food Safety, a Landscape Review

Food safety remains a significant public health issue for the poultry industry. Foodborne pathogens can be in contact at all phases of poultry production, from initial hatch to processing and ultimately to retail and meal preparation. Salmonella and Campylobacter have been considered the primary foodborne pathogens associated with poultry. Both organisms are major causative agents of human foodborne illness. Limiting these pathogens in poultry production requires identifying their sources and routes of transmission. This involves the ability to isolate and precisely identify them using methodologies capable of discernment at the genome level. Interventions to reduce their occurrence in poultry production employ two basic strategies: prevention of establishment and elimination of already-established pathogens. This review provides an overview of current findings and prospects for further research on poultry food safety issues.

Isolation, selection and evaluation of Bacillus spp. as potential multi-mode probiotics for poultry

Bacillus based probiotics are becoming relevant as alternatives to antibiotics used in poultry production and in other animal husbandry. This study describes the isolation of 48 Bacillus spp. candidates, from chickens and chicken environments, for use as potential probiotics in poultry production. These isolates, plus a further 18, were tested in a comprehensive in vitro screening regime that was specifically designed to select the best isolates that satisfied multiple modes of action desirable for commercial poultry probiotics. This screening programme involved the evaluation of the ability of the isolates to survive and grow in the limiting conditions of the chicken gastrointestinal tract. Only 11 of the isolates fulfilled these criteria; hence, they were further evaluated for the ability to adhere to epithelial cells, produce extracellular enzymes, and to demonstrate antagonistic activity against selected pathogens of significant importance in poultry production. Of these, a total of 6 isolates were selected, due to their all-round probiotic capability. Identification by 16S RNA sequencing confirmed these isolates as B. subtilis and B. velezensis, identities which are generally regarded as safe. The Bacillus isolates reported in our study exhibit strong all-inclusive probiotic effects and can potentially be formulated as a probiotic preparation for poultry production.

Impact of Poultry Processing Operating Parameters on Bacterial Transmission and Persistence on Chicken Carcasses and Their Shelf Life

It is important for the poultry industry to maximize product safety and quality by understanding the connection between bacterial diversity on chicken carcasses throughout poultry processing to the end of shelf life and the impact of the local processing environment. Enumeration of total aerobic bacteria, Campylobacter and Pseudomonas, and 16S rRNA gene amplicon sequencing were used to evaluate the processing line by collecting 10 carcasses from five processing steps: prescald, postplucker, pre- and post-immersion chill, and post-air chill. The diversity throughout a 12-day shelf life was also determined by examining 30 packaged carcasses. To identify the sources of possible contamination, scald water tank, immersion chilling water tank, air samples, and wall surfaces in the air-chill room were analyzed. Despite bacterial reductions on carcasses (>5 log10 CFU/ml) throughout the process, each step altered the bacterial diversity. Campylobacter was a minor but persistent component in the bacterial community on carcasses. The combination of scalding, defeathering, and plucking distributed thermophilic spore-forming Anoxybacillus to carcasses, which remained at a high abundance on carcasses throughout subsequent processes. Pseudomonas was not isolated from carcasses after air chilling but was abundant on the wall of the air-chill room and became the predominant taxon at the end of shelf life, suggesting possible contamination through air movement. The results suggest that attention is needed at each processing step, regardless of bacterial reductions on carcasses. Changing scalding water regularly, maintaining good hygiene practices during processing, and thorough disinfection at the end of each processing day are important to minimize bacterial transmission.IMPORTANCE Culture-based and culture-independent approaches were utilized to reveal bacterial community changes on chicken carcasses at different processing steps and potential routes from the local processing environment. Current commercial processing effectively reduced bacterial loads on carcasses. Poultry processes have similar processes across facilities, but various processing arrangements and operating parameters could impact the bacterial transmission and persistence on carcasses differently. This study showed the use of a single tunnel incorporating scalding, defeathering and plucking may undesirably distribute the thermoduric bacteria, e.g., Campylobacter and Anoxybacillus, between the local environment and carcasses, whereas this does not occur when these steps are separated. The length of immersion and air chilling also impacted bacterial diversity on carcasses. Air chilling can transfer Pseudomonas from wall surfaces onto carcasses; this may subsequently influence chicken product shelf life. This study helps poultry processors understand the impact of current commercial processing and improve the chicken product quality and safety.

Application of a Novel Phage LPSEYT for Biological Control of Salmonella in Foods

Salmonella is a leading cause of foodborne diseases, and in recent years, many isolates have exhibited a high level of antibiotic resistance, which has led to huge pressures on public health. Phages are a promising strategy to control food-borne pathogens. In this study, one of our environmental phage isolates, LPSEYT, was to be able to restrict the growth of zoonotic Salmonellaenterica in vitro over a range of multiplicity of infections. Phage LPSEYT exhibited wide-ranging pH and thermal stability and rapid reproductive activity with a short latent period and a large burst size. Phage LPSEYT demonstrated potential efficiency as a biological control agent against Salmonella in a variety of food matrices, including milk and lettuce. Morphological observation, comparative genomic, and phylogenetic analysis revealed that LPSEYT does not belong to any of the currently identified genera within the Myoviridae family, and we suggest that LPSEYT represents a new genus, the LPSEYTvirus. This study contributes a phage database, develops beneficial phage resources, and sheds light on the potential application value of phages LPSEYT on food safety.

Effect of a Synbiotic Mix on Intestinal Structural Changes, and Salmonella Typhimurium and Clostridium Perfringens Colonization in Broiler Chickens

Synbiotics can prevent gastrointestinal infections in broilers. This work studies the effect of a Synbiotic on broilers. One-day-old male broilers were divided into groups: Control; Synbiotic; Synbiotic + S. Typhimurium; Synbiotic + C. perfringens; Synbiotic + S. Typhimurium + C. perfringens; S. Typhimurium; C. perfringens; and S. Typhimurium + C. perfringens. Histopathological analysis revealed that the Synbiotic promoted longer villi, less deep crypts, and better villi-crypt ratio. Broilers treated with the Synbiotic, infected with pathogens or not, had healthier mucosa. In groups infected with pathogens, the frequency and intensity of histopathologic lesions were lessened often in groups treated with the Synbiotic. The Synbiotic group had higher lactic acid bacteria counts than the Control group on day 39, and the isolation frequency of S. Typhimurium was lower (p < 0.05) in the Synbiotic-treated groups. On day 18, mucosa, villi, villi-crypt ratio, crypt, and feed intake were influenced by Enterobacteriaceae. However, on day 39 (end of the trial), those parameters were influenced by lactic acid bacteria. The Synbiotic influenced morphological modifications in the duodenal mucosa, which in turn gave the broilers the ability to resist infections caused by S. Typhimurium and C. perfringens, by inhibiting their growth and decreasing the intensity and frequency of histopathological injuries.

Non-molecular characterization of pellicle formation by poultry Salmonella Kentucky strains and other poultry-associated Salmonella serovars in Luria Bertani broth

There is limited research concerning the biofilm-forming capabilities of Salmonella Kentucky, a common poultry isolate. The objective was to quantitate pellicle formation of S. Kentucky versus better-characterized Salmonella strains of Enteritidis and Heidelberg. In separate experiments, Salmonella strains and serovars were tested for their biofilm-forming abilities in different Luria-Bertani (LB) broths (1); pellicle formation in different volumes of LB without salt (2); and the potential priming effects on formation after pellicles were transferred three consecutive times (3). Data were analyzed using One-Way ANOVA with means separated using Tukey's HSD (P ≤ 0.05). In the first experiment, there was no significant effect between strain and serovars (P > 0.05), but media type affected pellicle formation significantly with LB Miller and LB minus NaCl plus 2% glucose resulting in no pellicle formation (P < 0.001). When grown in 50 mL, Kentucky 38-0085 produced larger pellicles than Kentucky 38-0055, and Heidelberg strain 38-0127 (P < 0.0001). Serial transfers of pellicles did not significantly affect pellicle formation (P > 0.05); however, Kentucky 38-0084, 38-0085 and 38-0086 produced larger pellicles than Kentucky 38-0055 and 38-0056 and Heidelberg 38-0126, 38-0127 and 38-0152. The current study demonstrates the consistent biofilm forming capabilities of Kentucky and may explain why Kentucky is frequently isolated in poultry processing facilities.

Evaluation of Incompatibility Group I1 (IncI1) Plasmid-Containing Salmonella enterica and Assessment of the Plasmids in Bacteriocin Production and Biofilm Development

Mobile genetic elements, such as plasmids, can potentially increase the ability of bacteria to infect and persist in vertebrate host cells. IncI1 plasmids are widely distributed in Salmonella from food animal sources and associated with clinically important strains. These plasmids often encode antimicrobial resistance; however, little is known about their impact on the virulence of Salmonella strains. To assess the potential impact of the plasmids on virulence, 43 IncI1-positive Salmonella isolates from human and animal sources were subjected to whole genome sequence (WGS) analyses and evaluated for their abilities to invade and persist for 48 h in Caco-2 human intestinal epithelial cells, form biofilms and encode bacteriocins. Draft WGS data were submitted to predict the presence of virulence and antimicrobial resistance genes, plasmid replicon types present, conduct plasmid multilocus sequence typing (pMLST), and core genome MLST (cgMLST) in the isolates. Caco-2 cells were infected with Salmonella strains and incubated for both one and 48 h for the invasion and persistence assays, respectively. Additionally, Salmonella isolates and IncI1 plasmid carrying transconjugants (n = 12) generated in Escherichia coli were assessed for their ability to produce biofilms and bacteriocin inhibition of growth of other bacteria. All Salmonella isolates infected Caco-2 cells and persisted in the cells at 48 hrs. Persistent cell counts were observed to be significantly higher than invasion assay cell counts in 26% of the isolates. Among the IncI1 plasmids, there were 18 pMLST types. Nearly 35% (n = 15) of Salmonella isolates produced biofilms; however, none of the IncI1-positive transconjugants produced increased biofilms compared to the recipient. Approximately 65% (n = 28) of isolates and 67% (n = 8) of IncI1-positive transconjugants were able to inhibit growth of at least one E. coli strain; however, none inhibited the growth of strains from species other than E. coli. The study characterized IncI1 positive Salmonella isolates and provided evidence about the potential contributions of IncI1 plasmids virulence phenotypes and areas where they do not. These findings should allow for more focused efforts to assess the impact of plasmids on bacterial pathophysiology and human health.

Understanding Antimicrobial Resistance (AMR) Profiles of Salmonella Biofilm and Planktonic Bacteria Challenged with Disinfectants Commonly Used During Poultry Processing

Foodborne pathogens such as Salmonella that survive cleaning and disinfection during poultry processing are a public health concern because pathogens that survive disinfectants have greater potential to exhibit resistance to antibiotics and disinfectants after their initial disinfectant challenge. While the mechanisms conferring antimicrobial resistance (AMR) after exposure to disinfectants is complex, understanding the effects of disinfectants on Salmonella in both their planktonic and biofilm states is becoming increasingly important, as AMR and disinfectant tolerant bacteria are becoming more prevalent in the food chain. This review examines the modes of action of various types of disinfectants commonly used during poultry processing (quaternary ammonium, organic acids, chlorine, alkaline detergents) and the mechanisms that may confer tolerance to disinfectants and cross-protection to antibiotics. The goal of this review article is to characterize the AMR profiles of Salmonella in both their planktonic and biofilm state that have been challenged with hexadecylpyridinium chloride (HDP), peracetic acid (PAA), sodium hypochlorite (SHY) and trisodium phosphate (TSP) in order to understand the risk of these disinfectants inducing AMR in surviving bacteria that may enter the food chain.

Short Communication: Preliminary Differences Identified in Genes Responsible for Biofilm Formation in Poultry Isolates of Salmonella enterica Heidelberg, Enteritidis, and Kentucky

Salmonella enterica is one of the most prevalent foodborne pathogens. The large quantity of serovar types results in the colonization of a large spectrum of hosts, with different environmental conditions and hazards. The aim of this study was to evaluate the differences in gene expression (bcsA and csgD) of Salmonella enterica serovars Heidelberg, Kentucky, and Enteritidis during biofilm formation using quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR). Overall, there appeared to be differences in expression between the different serovars with high variation between strains. These data are important as they demonstrate considerable variability in gene expression between serovars and strains of poultry isolates of Salmonella enterica.

Sequential Transmission of Salmonella in the Slaughtering Process of Chicken in Korea

Salmonella is one of the most common foodborne pathogens worldwide. Salmonella infections in humans are mainly associated with consumption of poultry products contaminated with this foodborne pathogen. Therefore, strict sanitary measures are necessary to control Salmonella contamination during the slaughtering process of poultry. The objective of this study was to determine the occurrence and transmission of Salmonella at a series of steps in the slaughtering process of chicken. A total of 601 samples were collected from a series of slaughtering steps (10 sampling sites) of 26 chicken slaughterhouses throughout Korea. Salmonella was isolated from samples and its distribution was analyzed along the slaughtering process. Isolates from each sampling site were tested for susceptibility to 15 antibiotics by the broth microdilution method. They were also genotypically characterized by pulsed-field gel electrophoresis (PFGE). Salmonela was isolated from 168 out of 601 samples. Sixteen serotypes were identified while six isolates were untypable. Salmonella enterica serovars Montevideo (n = 29) and Virchow (n = 27) were the most common serotypes out of 119 nonredundant isolates. Relatively high contamination rates of Salmonella were found in shackles (75.0%), feathers near plucking machine (68.5%), and feces from crates (44.0%). Twenty-three antibiotic resistance patterns were recognized and 40 (33.6%) isolates were resistant to five or more antibiotics. The same serotypes of Salmonella were distributed along the slaughtering process of each Salmonella-positive slaughterhouse. Most of those isolates belonging to the same serotype had identical or closely related PFGE profiles. They also shared common antibiotic resistance patterns. Overall findings of this study indicated that Salmonella were sequentially transmitted through the chicken slaughtering process. PRACTICAL APPLICATION: This study provides useful information on the distribution and transmission of Salmonella serotypes through the chicken slaughtering process. Overall findings indicated the need for routine microbiological monitoring along the slaughtering process. This study also showed that on-farm control of Salmonella is needed to obtain Salmonella-free chicken carcasses.

The Efficacy of Sodium Bisulfate Salt (SBS) Alone and Combined With Peracetic Acid (PAA) as an Antimicrobial on Whole Chicken Drumsticks Artificially Inoculated With Salmonella Enteritidis

The presence of Salmonella spp. on poultry products is one of the leading causes of foodborne illness in the United States. Therefore, novel antimicrobial substances are being explored as potential interventions in poultry processing facilities. The objective of the current study was to evaluate the efficacy of varying concentrations of sodium bisulfate salt, SBS, alone or in combination with peracetic acid, PAA, in 15 s whole part dips. Ninety six drumsticks (4 replications, 8 treatments, 3 days) were inoculated separately in a 400 mL solution of nalidixic resistant (NA) Salmonella Enteritidis (10⁷ CFU/mL) and allowed to adhere for 60 to 90 min at 4°C for a final concentration of 10⁶ CFU/g. The experimental treatments included: a no treatment (control), and 15 s dips in 300 mL of tap water alone (TW) or with the addition of 1; 2; and 3% SBS; 1; 2; and 3% SBS+PAA. After treatment, drumsticks were stored at 4°C until microbial sampling was conducted. On d 0, l, and 3, drumsticks were rinsed in 150 mL of nBPW for 1 min, 100 μL of rinsate was serially diluted, spread plated on XLT4+NA (20 μg/mL), and incubated aerobically at 37°C for 24 h. Log-transformed counts were analyzed using a randomized complete block design (day) using One-Way ANOVA, polynomial contrasts, and pairwise comparisons with means being separated by Tukey's HSD with a significance level of P ≤ 0.05. A treatment by day interaction (P = 0.14071) was not substantial. Thus, the treatment effect was investigated separately by days. Over time, a linear trend was observed in S. Enteritidis concentration when SBS was increased (1 < 2 < 3%). The concentration of S. Enteritidis was different between 1% SBS and 1% SBS+PAA on d 0. However, the level of S. Enteritidis was not different among drumsticks treated in 2 and 3% SBS and 2 and 3% SBS+PAA across d 0, 1, 3. The application of 3% SBS alone or in combination with 200 ppm of PAA is capable of reducing the presence of Salmonella over a 3-d refrigeration period; potentially increasing the safety of poultry products for consumers.

Ω-Shaped Fiber-Optic Probe-Based Localized Surface Plasmon Resonance Biosensor for Real-Time Detection of Salmonella Typhimurium

A novel, Ω-shaped fiber-optic localized surface plasmon resonance (FOLSPR) biosensor was designed for sensitive real-time and label-free bacterial detection. The designed Ω-shaped fiber-optic probe exhibits an outstanding sensitivity, due to the effect of unique geometry on performance. The results show that refractive index (RI) sensitivity of the Ω-shaped fiber-optic probe is 14 times and 2.5 times higher than those of the straight-shaped and the U-shaped FOLSPR, respectively. In addition, the reason for the geometry and the bending radius effects on RI sensitivity was discussed by investigating the relationship between RI sensitivity and the bending area. The results show that RI sensitivity was enhanced with the increase of bending area, and the best RI sensitivity obtained by Ω-shaped FOLSPR was 64.582 (a.u.)/RIU. Combined with this newly designed Ω-shaped FOLSPR biosensor, a real-time, label-free, sensitive, and highly selective bacterial detection method was established. In this work, the aptamers immobilized on the surface of FOLSPR could specifically capture Salmonella Typhimurium, resulting in an intense change of the absorption peak. In line with this principle, the FOLSPR biosensor achieved high detection sensitivity for Salmonella Typhimurium down to 128 CFU/mL within a linear range from 5 × 10² to 1 × 10⁸ CFU/mL and showed good selectivity for Salmonella Typhimurium detection compared to other bacteria. Furthermore, the FOLSPR biosensor was successfully applied to the detection of Salmonella Typhimurium in a chicken sample with the recoveries of 85-123%. With these characteristics, the novel biosensor is a potential alternative tool in food analysis and environmental monitoring.

Semi-Quantification of Total Campylobacter and Salmonella During Egg Incubations Using a Combination of 16S rDNA and Specific Pathogen Primers for qPCR

Rapid molecular techniques that evaluate eggs for the presence of foodborne pathogens is an essential component to poultry food safety monitoring. Interestingly, it is not just table eggs that contribute to outbreaks of foodborne disease. Broiler layer production actively contributes to sustaining of foodborne pathogens within a flock. The surface contamination of production eggs with invasive pathogens such as Salmonella enterica, Campylobacter jejuni, and Listeria monocytogenes during embryogenesis results in gastrointestinal tract (GIT) colonization. Pathogens that secure a niche within the GIT during embryonic development are nearly impossible to eradicate from the food chain. Therefore, current monitoring paradigms are not comprehensive because they fail to capture the presence of invasive pathogens within the embryonic GIT rapidly. By developing tools to recognize the pathogens' presence in the GIT during embryogenesis, producers are then able to spot evaluate broiler eggs for their potential risk as carriers of foodborne pathogens. In this study a novel qPCR assay was developed to semi-quantify pathogen load relative to total bacterial burden. Eggs sampled from three independent production broiler flocks of different ages were assayed for S. enterica (invA), C. jejuni (HipO), and L. monocytogenes (HlyA) against total microbial load (16s). The eggs were sampled at 1-day post-set within each flock, 2 weeks post-set, after vaccination (at 2.5 weeks) and 1-day post-hatch. The eggs were washed, and the yolk and embryonic chick GIT were collected. The DNA was extracted and subjected to a qPCR assay. The results confirm a novel technique for pathogen monitoring relative to total bacterial load and a unique method for monitoring the dynamics of foodborne pathogen invasion throughout broiler egg production.

Salmonella Contamination in Broiler Synovial Fluid: Are We Missing a Potential Reservoir?

The objective of this study was to assess the presence and characteristics of Salmonella enterica found in the synovial fluid of broiler carcasses. The synovial fluid of three individual joints from 500 broiler carcasses was individually sampled from five broiler processing facilities located in the Southeast and West regions of the United States (1,500 total samples). The external surface of broiler carcass was decontaminated before sampling of the shoulder, coxofemoral, and tibiofemoral joints. Individual samples were enriched, composited, and subjected to rapid PCR-based detection of Salmonella. Individual samples from any positive composites were also enriched before determination of Salmonella presence in the same manner. Positive individual samples were subjected to secondary enrichment before plating onto selective agar for isolation of Salmonella. Salmonella isolates were serotyped before determination of antimicrobial susceptibility. Overall, 1.00% (5 of 500 broiler carcasses) of composite samples and 0.47% (7 of 1,500 samples) of individual samples were positive for Salmonella. Five of the seven isolates were susceptible to all drugs tested and determined to be Salmonella Enteritidis. The remaining two isolates, identified as Salmonella Typhimurium, were resistant to streptomycin. To our knowledge, no previous assessments of Salmonella in the synovial fluid of broilers has been reported; however, results of the present study suggested that the synovial fluid may be a reservoir for Salmonella in broilers. Although the prevalence of Salmonella is low, this information provides valuable insight into potential poultry contamination pathways and warrants further exploration.

Control of Salmonella Enteritidis on food contact surfaces with bacteriophage PVP-SE2

Salmonella is one of the worldwide leading foodborne pathogens responsible for illnesses and hospitalizations, and its capacity to form biofilms is one of its many virulence factors. This work evaluated (bacterio)phage control of adhered and biofilm cells of Salmonella Enteritidis on three different substrata at refrigerated and room temperatures, and also a preventive approach in poultry skin. PVP-SE2 phage was efficient in reducing both 24- and 48-h old Salmonella biofilms from polystyrene and stainless steel causing 2 to 5 log CFU cm^-2 reductions with a higher killing efficiency at room temperature. PVP-SE2 phage application on poultry skins reduced levels of Salmonella. Freezing phage-pretreated poultry skin samples had no influence on the viability of phage PVP-SE2 and their in vitro contamination with S. Enteritidis provided evidence that phages prevented their further growth. Although not all conditions favor phage treatment, this study endorses their use to prevent and control foodborne pathogen colonization of surfaces.

Molecular-based identification and detection of Salmonella in food production systems: current perspectives

Salmonella remains a prominent cause of foodborne illnesses and can originate from a wide range of food products. Given the continued presence of pathogenic Salmonella in food production systems, there is a consistent need to improve identification and detection methods that can identify this pathogen at all stages in food systems. Methods for subtyping have evolved over the years, and the introduction of whole genome sequencing and advancements in PCR technologies have greatly improved the resolution for differentiating strains within a particular serovar. This, in turn, has led to the continued improvement in Salmonella detection technologies for utilization in food production systems. In this review, the focus will be on recent advancements in these technologies, as well as potential issues associated with the application of these tools in food production. In addition, the recent and emerging research developments on Salmonella detection and identification methodologies and their potential application in food production systems will be discussed.

Salmonella Cold Stress Response: Mechanisms and Occurrence in Foods

Since bacteria in foods often encounter various cold environments during food processing, such as chilling, cold chain distribution, and cold storage, lower temperatures can become a major stress environment for foodborne pathogens. Bacterial responses in stressful environments have been considered in the past, but now the importance of stress responses at the molecular level is becoming recognized. Documenting how bacterial changes occur at the molecular level may help to achieve the in-depth understanding of stress responses, to predict microbial fate when they encounter cold temperatures, and to design and develop more effective strategies to control pathogens in food for ensuring food safety. Microorganisms differ in responding to a sudden downshift in temperature and this, in turn, impacts their metabolic processes and can cause various structural modifications. In this review, the fundamental aspects of bacterial cold stress responses focused on cell membrane modification, DNA supercoiling modification, transcriptional and translational responses, cold-induced protein synthesis including CspA, CsdA, NusA, DnaA, RecA, RbfA, PNPase, KsgA, SrmB, trigger factors, and initiation factors are discussed. In this context, specific Salmonella responses to cold temperature including growth, injury, and survival and their physiological and genetic responses to cold environments with a focus on cross-protection, different gene expression levels, and virulence factors will be discussed.

Salmonella in Foods: A Reemerging Problem

The number of human salmonellosis within the European Union tended to increase since 2013. One of the reasons might be Salmonella Enteritidis rising in laying hens flocks by around 17% in 2015 vs 2014 and by 57% in 2016 vs 2015. The most important sources of food-borne Salmonella outbreaks are still eggs and egg products as well as ready-to-eat foods having a long shelf life. Specific actions are suggested to restart decreasing the number of human salmonellosis: (1) revision of sampling schemes to solve pathogen under detection in both animals and foods; (2) integration of microbiological criteria with fit for purpose performance objectives and food safety objectives; and (3) improvement of epidemiological investigations of human, food, and animal isolates by using whole-genome sequencing in order to effectively track salmonellosis and verify which prevention measures are most effective.

Effect of Various Inoculum Levels of Multidrug-Resistant Salmonella enterica Serovar Heidelberg (2011 Ground Turkey Outbreak Isolate) on Cecal Colonization, Dissemination to Internal Organs, and Deposition in Skeletal Muscles of Commercial Turkeys after Experimental Oral Challenge

Salmonella enterica serovar Heidelberg (S. Heidelberg) is a major foodborne pathogen colonizing poultry. The pathogen is associated with a significant number of foodborne outbreaks through contaminated poultry meat, including turkeys. Recently, multidrug-resistant (MDR) strains of S. Heidelberg have emerged as a threat to human public health in the United States. The objective of this study was to determine the cecal colonization, dissemination to internal organs, and the potential for skeletal muscle deposition of an MDR S. Heidelberg isolate from the 2011 ground turkey outbreak in the United States after the experimental oral challenge of poults (young turkeys) and adult turkey hens. In the poult study, two separate experiments using day-old, straight-run, commercial hybrid converter poults were randomly assigned to five challenge groups (0, 10∧2, 10∧4, 10∧6, 10∧8 CFU groups; 12 poults/group; N = 60/experiment) and a week after, treatment groups were challenged separately with 0-, 2-, 4-, 6-, and 8- log10 CFU of S. Heidelberg orally. After 14 days post-challenge, the poults were euthanized, and samples were collected to determine MDR S. Heidelberg colonization in the cecum, dissemination to liver and spleen, and deposition in the thigh, drumstick, and breast muscles. A similar experimental design was followed for the adult turkey hens. In two separate experiments, 11-week-old commercial Hybrid Converter turkey hens (4 hens/group; N = 20/experiment) were challenged with MDR S. Heidelberg and on day 16 post-challenge, birds were euthanized and samples were collected to determine Salmonella populations in the samples. The results indicated that, in turkey poults, the recovery of MDR S. Heidelberg was highest in the cecum followed by spleen, liver, thigh, drumstick, and breast. All tested inoculum levels resulted in more than 3.5 log10 CFU/g colonization in the poult cecum. The cecal colonization, dissemination to internal organs, and tissue deposition of MDR S. Heidelberg were high in poults. The pathogen recovery from the cecum of adult turkey hens ranged from 37.5 to 62.5% in the challenge groups. The results signify the importance of controlling MDR S. Heidelberg in turkeys at the farm level to improve the safety of turkey products.

Prevalence, Virulence Genes and Antimicrobial Resistance Profiles of Salmonella Serovars from Retail Beef in Selangor, Malaysia

The aim of the present study was to investigate the prevalence of Salmonella spp., Salmonella Enteritidis and Salmonella Typhimurium in retail beef from different retail markets of Selangor area, as well as, to assess their pathogenic potential and antimicrobial resistance. A total of 240 retail beef meat samples (chuck = 60; rib = 60; round = 60; sirloin = 60) were randomly collected. The multiplex polymerase chain reaction (mPCR) in combination with the most probable number (MPN) method was employed to detect Salmonella spp., S. Enteritidis and S. Typhimurium in the meat samples. The prevalence of Salmonella spp., S. Enteritidis and S. Typhimurium in 240 beef meat samples were 7.50, 1.25, and 0.83%, respectively. The microbial loads of total Salmonella was found in the range of <3 to 15 MPN/g. Eight different serovars of Salmonella were identified among the 23 isolates, and S. Agona was the predominant serovar (26.09%). Interestingly, all the Salmonella isolates were resistant to penicillin, erythromycin and vancomycin, but the sensitivity was observed for tetracycline, gentamicin and amoxicillin/clavulanic acid. All 23 isolates were resistant to at least three antibiotics. Two S. Typhimurium isolates (8.70%) exhibited the highest multiple antibiotic resistance (MAR) index value of 0.56 which shown resistance to nine antibiotics. PCR analysis of virulence genes showed that all Salmonella isolates (100%) were positive for the invA gene. Meanwhile, pefA was only identified in S. Enteritidis and S. Typhimurium. The findings in this study indicate that retail beef products tested were widely contaminated with multi-drug resistant (MDR) Salmonella and various virulence genes are present among the isolated Salmonella serovars.