Prevention and Control of Human Salmonella enterica Infections: An Implication in Food Safety

Isolation and characterization of virulent bacteriophages and controlling Salmonella Enteritidis biofilms on chicken meat

Salmonella is a prominent zoonotic pathogen that continues to represent a large threat to food safety and public health worldwide. Concurrently, the inappropriate use of antibiotics has led to the development of antibiotic-resistant strains of Salmonella, highlighting the urgent need for new approaches to manage these bacteria. In this context, virulent bacteriophages are increasingly recognized as a potential and effective biological control method against Salmonella. This study identifies two newly isolated virulent Salmonella phages, phage vB_SalD_ABTNLS3 (S3 for short) and phage 2-3 (2-3 for short). Both phages exhibited effectiveness in preventing biofilm formation and reducing biofilm. S3 and 2-3 could maximize the inhibition of more than 70% and 91% of biofilm formation after 48 h of treatment, and maximize the removal of more than 59% and 96% of mature biofilm after 3 h and 5 h, respectively. Based on these, our study assessed the efficacy of 2-3 in controlling Salmonella enterica serotype Enteritidis (SE) on raw chicken meat at 4°C with varying MOIs, including 1, 100, and 10,000. The maximum reduction observed in SE on chicken meat was 1.15 log10 CFU/mL following a 12-h treatment with the 2-3, a significant decrease of more than 92% compared to the initial levels present in the experiment (MOI = 10,000). In conclusion, our phages performed well in controlling biofilm and disinfecting refrigerated food at 4°C, suggesting their potential as biological agents to reduce Salmonella contamination in the food industry.

Transmission of a plasmid harboring NDM-1 gene between Salmonella Typhimurium and Escherichia coli strains in an infant

BACKGROUND

NDM-1 has been frequently identified in Enterobacteriaceae strains from clinical samples, but its occurrence in Salmonella Typhimurium (S. Typhimurium) is uncommon. Moreover, reports on the transmission of a plasmid harboring NDM-1 between different species in clinical samples are rare.

METHODS

Two S. Typhimurium strains and an Escherichia coli (E. coli) strain were isolated from a 14-month-old infant presenting with diarrhea. The resistance phenotypes were determined using the VITEK 2 Compact System. Genomic DNA was extracted from the isolated strains and whole genome sequencing was performed. The transmissibility of plasmids was validated by a conjugation experiment.

RESULTS

The subsequently isolated S. Typhimurium and E. coli strains exhibited resistance to imipenem, and whole genomic analysis revealed that each strain harbored a plasmid harboring NDM-1 and Qnrs1 genes. The two plasmids were nearly identical based on their sequences and could transfer to recipient strains. A genomic region containing several genes encoding phosphoribosylanthranilate isomerase, bleomycin binding protein, subclass B1 metallo-beta-lactamase, and IS30-like element ISAba125 family transposase was surrounded by the two flanking IS26 elements.

CONCLUSION

The transfer of plasmid harboring NDM-1 between S. Typhimurium and E. coli strains within patients highlights the potential for widespread transmission between different species. Continuous monitoring these strains may be important for preventing extensive transmission of resistance genes.

Stress responses and Physiological Changes of Salmonella enterica Serovar Enteritidis on Short-Term and Long-Term Benzalkonium Bromide Adaptation

Salmonella enterica is a common foodborne pathogen that poses significant safety risks across the world. And benzalkonium bromide (BK) is widely used as a disinfectant to sterilize the food processing equipment. It has been reported that sub-lethal concentration of disinfectants induced not only the homologous resistance but also cross-resistances. This work analyzed the induced resistances of Salmonella Enteritidis by short-term adaptation (STA) and long-term adaptation (LTA) to BK. We have demonstrated that inefficient sterilization exposes Salmonella Enteritidis to sub-lethal concentrations of BK, and adapts bacteria to a higher minimum inhibitory concentration and minimum bactericidal concentration. In addition, STA, but not LTA, to BK induced heterogeneous resistance to sodium hypochlorite, and cross-resistance to freezing, desiccation, and heating, which may be caused by the membrane composition change of Salmonella Enteritidis. This work could be useful to the optimization of cleaning protocol.

Salmonella Heidelberg isolates from poultry in Brazil and the United States share a large number of resistance and virulence determinants

Salmonella enterica subps. enterica serovar Heidelberg (SH) is one of the most common serovars isolated from poultry and associated with severe infections in humans. Commonly considered multidrug-resistant, it represents a risk to public health. We analyzed 317 SH genomes, including 314 from the Enterobase database from Brazil and the United States (US), and added three recently sequenced Brazilian isolates. In genomes from both countries, the main identified resistance genes were: aac(6')-Iaa, fosA7, sul2, tet(A), and blaCMY-2. Mutations in GyrA (S83Y only from US genomes and S83F and D87N from Brazilian genomes) were observed in 17 % and 90.62 % of genomes from US and Brazil, respectively, and ParC mutation (T57S), was identified in all genomes. The plasmid replicons most identified in both countries were ColpVC, IncC, IncI1-I(Gamma), and IncX1. The core and soft-core genes were utilized as the basis for conducting a phylogenetic analysis, showing seven clusters of strains, of which only one was shared between strains from the US and Brazil. Overall, this study highlights the variation in genomic profiles of SH circulating in poultry production in both countries, emphasizing the need for improved surveillance measures to protect human and animal populations from potential outbreaks worldwide.

Characterization and therapeutic potential of newly isolated bacteriophages targeting the most common Salmonella serovars in Europe

Despite meticulous monitoring of Salmonella spp. throughout the food chain to ensure safer animal food products for consumers, the number of salmonellosis cases in humans continues to rise annually in Europe. Phage therapy emerges as a promising tool for controlling and eradicating Salmonella in primary production. This study aimed to fully characterize new phage therapy candidates isolated from animal sources. To achieve this, a phenotypic and genetic characterization of five phage isolates was conducted. The five phages demonstrated physical stability across a wide range of temperatures and pH levels, effectively lysing 12 different Salmonella serovars, including the most prevalent ones in the European Union in recent years, as well as multidrug-resistant strains isolated from the field. Additionally, four of the phages exhibited depolymerase production in the host range, with genomic analysis confirming that all five possessed sequences encoding for this activity, suggesting their potential as surface-disinfecting agents. Genetic analysis further revealed that the phages belong to distinct genera: Felixounavirus, Cornellvirus, Skatevirus, Agtevirus and Berlinvirus. Notably, none of the phages contained harmful sequences that could compromise their future application, such as virulence factors, antibiotic resistance genes or temperate markers. Overall, these five phages show promise as suitable candidates for phage therapy applications or phage-based Salmonella eradication strategies, where their integration in the existing biocontrol measures may enhance both food safety and public health.

A systematic review of recent outbreaks and the efficacy and safety of drugs approved for the treatment of Salmonella infections

A systematic review was conducted to critically analyze the outbreaks, efficacy, and safety of drugs used to treat various Salmonella infections. Four drugs-azithromycin, ceftriaxone, ciprofloxacin, and amoxicillin-are commonly used to treat Salmonella infections, and all four drugs were included in this review. This review found that, of these, azithromycin and ceftriaxone were more effective in treating Salmonella infections based on the patient's length of stay in the hospital and the rate at which the fever was resolved. Fluoroquinolones are also effective in treating Salmonella infection but are not approved for use in children. Azithromycin was found to be the physicians' preferred choice of medication for Salmonella infection due to its less resistance development. Almost all these drugs produce varying degrees of adverse events, but they are mild to moderate. However, azithromycin was shown to be comparatively safer than the other three drugs in terms of side effects, adverse events, and relapse associated with Salmonella treatment. Developing effective and safe therapies for all strains of Salmonella remains a priority, especially given the increasing prevalence of antibiotic-resistant variants.

Impact of nafcillin and diosmin on the attachment, invasion, and stress survival of Salmonella Typhimurium

Salmonella Typhimurium is an invasive intracellular pathogen that employs various factors for its survival within host cells. To mitigate S. Typhimurium survival, it is crucial to identify factors that influence bacterial survival and to develop drugs that inhibit these factors. In this study, we investigated the effects of nafcillin and diosmin, both of which have been identified as inhibitors of Lon protease, on the intracellular survival of S. Typhimurium and its survival under various stress conditions. Additionally, we examined the expression of genes associated with the type II toxin-antitoxin system to enhance our understanding of the impact of these systems on the bacterium's survival. Our findings indicate that while nafcillin and diosmin did not affect S. Typhimurium attachment, they significantly reduced bacterial intracellular survival, particularly in Hep2 cells after 16 h. These inhibitors were also effective in decreasing bacterial survival under oxidative and acidic stress conditions. Furthermore, gene expression analysis revealed that although there were variations in the expression of TA system genes in S. Typhimurium across different cell lines, the relEB system emerged as the most effective among those studied, exhibiting the highest increase in expression. This study highlights the efficacy of nafcillin and diosmin in reducing the intracellular survival of S. Typhimurium as well as its survival under stress conditions. These findings suggest potential new strategies for developing therapies aimed at preventing S. Typhimurium infections.

IS15DIV-flanked composite transposon harboring bla NDM-5 in multidrug-resistant Salmonella Typhimurium

Multidrug-resistant Salmonella Typhimurium has emerged as a global public health concern. Asymptomatic gastrointestinal carriage is a key factor in the spread of antibiotic-resistant bacteria. However, it is challenging to obtain direct evidence of in vivo transfer of mobile genetic elements (MGEs). Here, we found that MGEs harboring bla NDM-5 were transferred from asymptomatic Escherichia coli (LS20223694) to Salmonella Typhimurium (LS20223695) in a child. BLAST analyses demonstrated that the IS15DIV-flanked composite transposon of pLS20223695_NDM5 showed high similarity with pLS20223694_NDM5 and two previously reported plasmids, suggesting the possibility of genetic recombination. Besides, conjugation experiments showed that the transconjugant carried the incompatibility group I1 (IncI1)-I(alpha) plasmid replicon with the bla NDM-5 and sul1 genes, indicating that pLS20223695_NDM5 is a conjugative plasmid with transferability. Our study provides insights into the genetic basis of an IS15DIV-flanked composite transposon in Salmonella Typhimurium.

Adsorption Studies of Salmonella Enteritidis and Escherichia coli on Chitosan-Coated Magnetic Nanoparticles

One of the challenges of microbiological testing is the complex and lengthy sample preparation, causing delays in getting the final result. Immunomagnetic separation is one of the sample preparation techniques recently used to overcome this complexity. However, it is expensive, fragile, and requires cold storage. This study aimed to use chitosan-coated magnetic nanoparticles (cMNP) to capture bacterial cells from a simulated matrix and understand the interaction between the bacteria and the cMNP using batch adsorption studies. To illustrate the concept, Salmonella Enteritidis and Escherichia coli were used. Results showed that the adsorption of Salmonella Enteritidis and E. coli fitted the pseudo-second-order kinetic model (R2 = 0.939 and 0.968, respectively) and the Freundlich isotherm model (R2 = 0.999 and 0.970, respectively). The increased ionic strength enhanced bacterial adsorption, and the highest capture efficiency was observed at pH 4 (32.8% and 98.1% for Salmonella Enteritidis and E. coli, respectively). These results show that chemisorption plays a significant role in bacterial adsorption to cMNP. Furthermore, increasing ionic strength and acidic pH (pH 4) significantly affects the adsorption of Salmonella Enteritidis and E. coli on cMNP, making them crucial for enhancing the performance of cMNP-based sample preparation methods.

Identification of Salmonella enteritidis, Salmonella typhimurium, Bacillus cereus, Bacillus subtilis, and Clostridium perfringens in hospital food

Despite conducting studies to investigate food contamination in hospitals in different parts of Iran in recent years, there have been no reliable studies to identify Salmonella enteritidis, Salmonella typhimurium, Bacillus cereus, Bacillus subtilis, and Clostridium perfringens in hospital food in Mashhad. Therefore, this study was conducted with the aim of investigating some major foodborne pathogens in hospital food. In this study, 360 food samples were randomly selected from 12 different menus from 13 hospitals affiliated with Mashhad University of Medical Sciences, Mashhad, Iran. Microbial culture methods for the recovery/isolation or enumeration of Salmonella spp., Bacillus spp. and C. perfringens as well as toxinotyping of C. perfringens using the PCR method were performed. B. cereus and C. perfringens were detected in 4 out of 360 food samples, 2 (0.55%) of which were B. cereus and, the remaining 2 (0.55%) were C. perfringens; B. subtilis was not detected in any of the food samples. Furthermore, Salmonella was found in 21 (5.82%) food samples, 12 (3.33%) of which were S. typhimurium, 4 (1.11%) were S. enteritidis, and 5 (1.38%) belonged to other Salmonella species. The most contaminated foods were salad, kebab, and rice samples, which accounted for 36%, 16%, and 12% of the contaminated foods, respectively. In our study, two strains of S. typhimurium and S. enteritidis, were the primary causative agents of food contamination among the investigated pathogens. More stringent control measures should be implemented in hospital catering, particularly for unprocessed foods such as salads.

Ensuring egg safety: Salmonella survival, control, and virulence in the supply chain

Salmonella contamination of eggs is a global food safety concern, producers, regulatory authorities, and affecting public health. To mitigate Salmonella risks on-farm and along the supply chain, egg producers have adopted various quality assurance, animal husbandry, and biosecurity practices recommended by organizations such as Australian eggs, the European Commission, and the US Department of Agriculture (USDA). However, egg storage requirements vary significantly worldwide. In Australia, most states follow the Food Standards Australia New Zealand, but discrepancies exist. In the United States, the USDA mandates refrigeration of eggs below 7.2°C to prevent Salmonella growth, whereas the European Union requires that eggs must not be refrigerated to avoid condensation, which may promote bacterial growth. Refrigeration of eggs is associated with reduced Salmonella growth and decreased infection risk. Yet, conflicting data regarding the impact of storage temperatures on Salmonella survival may contribute to the disparity between international recommendations for egg storage. Studies indicated better Salmonella survival in egg contents at 5°C due to higher expression levels of survival and stress response-related genes compared to 25°C, yet this may not lead to an increased risk or higher severity of Salmonella infection. Evidence suggests that storing eggs at less than 7°C will influence the virulence of bacteria. Warmer storage temperatures may lead to increased potential of Salmonella multiplication in the nutrient-rich yolk and may cause the expression of certain virulence genes. Eggs can be exposed to various temperatures in the supply chain. Further studies are essential to understand the relationship between the storage temperature on the farm, in the supply chain, and bacterial virulence.

Salmonella-based therapeutic strategies: improving tumor microenvironment and bringing new hope for cancer immunotherapy

Immunotherapy has revolutionized cancer treatment, yet its effectiveness is limited by immunosuppressive tumor microenvironment (TME). To overcome this challenge, innovative strategies to effectively modulate the TME are urgently needed. Over the past decades, bacteria-mediated cancer immunotherapy has recaptured increasing attention, driven by advances in synthetic biology, genetic engineering and our knowledge of host-pathogen interactions. Among various bacterial species, Salmonella has emerged as a leading candidate with significant therapeutic potential due to its broad-spectrum anti-tumor activity, tumor-targeting ability, immunomodulatory effects, oncolytic properties, genetic programmability, and engineering flexibility. These characteristics enable Salmonella to reshape the immunosuppressive TME, thereby enhancing anti-tumor efficacy. This review elaborates the regulatory effects of Salmonella on key components of the TME, the versatile engineering strategies for optimizing Salmonella's ability to modulate the TME, and recent advancements in combination cancer therapies. We also summarize current clinical applications and discuss challenges of developing safer and more effective Salmonella-based cancer immunotherapy.

Lateral Flow Immunosensing of Salmonella Typhimurium Cells in Milk: Comparing Three Sequences of Interactions

To ensure the safety of foodstuffs, widespread non-laboratory monitoring for pathogenic contaminants is in demand. A suitable technique for this purpose is lateral flow immunoassay (LFIA) which combines simplicity, rapidity, and productivity with specific immune detection. This study considered three developed formats of LFIA for Salmonella Typhimurium, a priority pathogenic contaminant of milk. Common sandwich LFIA with all immunoreagents pre-applied to the test strip (format A) was compared with incubation of the sample and (gold nanoparticle-antibody) conjugate, preceding the lateral flow processes (format B), and sequential passages of the sample and the conjugate along the test strip (format C). Under the chosen conditions, the detection limits and the assay times were 3 × 104, 1 × 105, and 3 × 105 cells/mL, 10, 15, and 20 min for formats A, B, and C, respectively. The selected format A of LFIA was successfully applied to test milk samples. The sample's dilution to a fat content of 1.0% causes pathogen detection, with 70-110% revealing and 1.5-8.5% accuracy. The obtained results demonstrate that the developed LFIA allows the detection of lower concentrations of Salmonella cells and, in this way, accelerates decision-making in food safety control.

Prevalence of Non-typhoidal Salmonellae in the Retail Chicken Meat in Alexandria, Egypt

The objective of this study was to evaluate the extent of Salmonella contamination in retail chicken carcasses within Alexandria, Egypt, while also identifying the specific serotypes present. The research addresses the scarcity of comprehensive data concerning Salmonella distribution and its phenotypic attributes in chicken meat across the Alexandria Governorate. A total of sixty raw chicken carcass samples were randomly acquired from six different markets in Alexandria. Detection of Salmonella spp. was conducted based on standard culture techniques, biochemical analyses, and serological tests. The results revealed an overall occurrence of 33.3% in Salmonella contamination. The most prevalent serotypes were S. typhimurium and S. kentucky. Among the sampled chicken carcass components, the liver and gizzard exhibited the highest contamination rates at 60% each, followed by the neck at 50%, and the wing at 30%. Conversely, no traces of Salmonella were detected in the heart and small intestine samples. This absence could be attributed to the administration of antibiotics in poultry feeds at the farm level. Analysis of various markets highlighted differing contamination rates; Asafra, Alabrahimih, and Mansheya registered the highest rates at 60%, 40%, and 40% respectively. In contrast, Borg El Arab and Amriya experienced lower rates with both displaying a 30% contamination level. Intriguingly, a supermarket within Alexandria showed no presence of Salmonella spp. The study underscores substantial carcass contamination during the market handling phase, emphasizing the need for intervention strategies from relevant stakeholders to mitigate these contamination impacts.

Oral vaccination of young broilers with a live Salmonella Typhimurium vaccine reduces caecal and internal organ colonization following a Salmonella Infantis challenge in a seeder-bird model

Poultry products are an important source of foodborne Salmonella infections in humans. Amongst these, the prevalence of S. Infantis is rising. In this study, the protection efficacy of an authorized live-attenuated S. Typhimurium vaccine against S. Infantis, was examined using a seeder-bird model in broilers. Vaccinated birds displayed a significantly lower colonization of S. Infantis bacteria in the caeca compared to the non-vaccinated counterparts (P = 0.017), with no significant differences observed in the spleen among the groups, three days post-infection. Thirty-two days post-infection, the disparity in average S. Infantis concentration between all-vaccinated and non-vaccinated birds was significant in both caeca (P = 0.0003) and spleen (P = 0.0002). Interestingly, a third group, consisting of seeder birds that were not vaccinated but housed with vaccinated penmates, exhibited significantly lower S. Infantis levels in both caeca (P = 0.0014) and spleen (P < 0.0001) compared to the non-vaccinated group. These findings underscore the potential of a live-attenuated S. Typhimurium vaccine administered to 2-day-old chicks in conferring protection against S. Infantis in broilers up to slaughter age.

Phenotypic Characterization and Genome Analysis of New Broad-Spectrum Virulent Salmophage, Salmonella Phage KKP_3822, for Biocontrol of Multidrug-Resistant Salmonella enterica Strains

Salmonella is one of the main foodborne pathogens. Irrational antibiotic management has led to an increase in the incidence of multidrug-resistant strains. Bacteriophages may be an alternative method of food biopreservation and contribute to reducing the number of food poisonings requiring pharmacotherapy. This study aimed to isolate a bacteriophage (phage) targeting indigenous multidrug-resistant (MDR) Salmonella strains, followed by their biological, morphological, and genomic characterization. In this study we isolated Salmonella phage KKP_3822, targeting MDR Salmonella Manchester strain KKP 1213. Salmonella phage KKP_3822 retained high activity in the temperature range from -20 °C to 40 °C and active acidity from pH 3 to 11. Temperatures of 70 °C and 80 °C and extreme pH values (2 and 12) significantly reduced the phage titer. Its activity decreased proportionally to the time of UV exposure. Genome analysis (linear dsDNA with a length of 114,843 bp) revealed the presence of 27 tRNA genes. Proteins encoded by the vB_Sen-IAFB3822 phage were divided into functional modules related to (i) phage structure/assembly, (ii) DNA replication/modification/regulation, (iii) phage lysis, and (iv) DNA packaging into the capsid. No genes associated with antibiotic resistance or integration into the host genome, markers of temperate bacteriophages, were annotated in the Salmonella phage KKP_3822 genome. Based on morphological features and whole-genome sequence analysis, the newly isolated Salmonella phage KKP_3822 shows the greatest similarity to representatives of tailed phages from the Caudoviricetes class, Demerecviridae family, and Epseptimavirus genus. Genome analysis confirmed the virulent nature of the Salmonella phage KKP_3822, making it a potential candidate for food biocontrol.

Evaluating the effectiveness and safety of a novel phage cocktail as a biocontrol of Salmonella in biofilm, food products, and broiler chicken

Salmonella is a foodborne pathogen of animal and public health significance. Considering the disadvantages of antibiotics or chemical preservatives traditionally used to eliminate this pathogen, attention has shifted, in recent years, toward biocontrol agents such as bacteriophages, used either separately or in combination to prevent food contamination. However, extensive use of phage-based biocontrol agents in the food industry requires further studies to ensure their safety and efficacy. In the present study, we investigated the effectiveness and safety of phage cocktail, a phage cocktail comprising three pre-characterized Salmonella phages (vB_SenS_TUMS_E4, vB_SenS_TUMS_E15 and vB_SenS_TUMS_E19). First, we performed an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide] assay on a human foreskin fibroblast cell line, in which the resulting high cell viability revealed the safety of the phage cocktail. Next, we performed a time-kill assay in which a 4 Log decline in bacterial levels was detected. Additionally, we utilized a colorimetric method to evaluate the anti-biofilm activity of phage cocktail, in which it proved more efficacious compared to the MIC and MBEC levels of the antibiotic control. Then, we assessed the ability of phage cocktail to eradicate Salmonella in different food samples, where it considerably reduced the bacterial count regardless of the temperature (4°C and 25°C). Lastly, we used broiler chickens as an animal model to measure the growth-promoting activity of phage cocktail. Salmonella-infected chickens orally treated with modified phage cocktail demonstrated no mortality and a significant increase in weight gain compared to the untreated group (p ≤ 0.0002). The study presents a novel research evaluating the effectiveness and safety of a phage cocktail as a biocontrol agent against Salmonella in various contexts, including biofilms, food products, and broiler chickens. This multifaceted approach underscores the promising role of phage therapy as a sustainable biocontrol strategy in food safety and public health contexts.

Plant Microbe Interaction-Predicting the Pathogen Internalization Through Stomata Using Computational Neural Network Modeling

Foodborne disease presents a substantial challenge to researchers, as foliar water intake greatly influences pathogen internalization via stomata. Comprehending plant-pathogen interactions, especially under fluctuating humidity and temperature circumstances, is crucial for formulating ways to prevent pathogen ingress and diminish foodborne hazards. This study introduces a computational model utilizing neural networks to anticipate pathogen internalization via stomata, contrasting with previous research that emphasized biocontrol techniques. Computational modeling assesses the likelihood and duration of internalization for bacterial pathogens such as Salmonella enterica (S. enterica), considering various environmental factors including humidity and temperature. The estimated likelihood ranges from 0.6200 to 0.8820, while the internalization time varies from 4000 s to 5080 s, assessed at 50% and 100% humidity levels. The difference in internalization time, roughly 1042.73 s shorter at 100% humidity, correlates with a 26.2% increase in the likelihood of internalization, rising from 0.6200 to 0.8820. A neural network model has been developed to quantitatively predict these values, thereby enhancing the understanding of plant-microbe interactions. These methods will aid researchers in understanding plant-pathogen interactions, especially in environments characterized by varying humidity and temperature and are essential for formulating strategies to prevent pathogen ingress and tackle foodborne illnesses within a technologically advanced context.

Network and systems biology approaches help investigate gene regulatory interactions between Salmonella disease and host in chickens: Model-based in silico evidence combined with gene expression assays

BACKGROUND

Salmonella enteritidis (SE), a previously widespread infectious disease, is still cited as a major factor in economic losses in commercial chicken production. The host's genetic immune system determines the pathogenicity of a particular bacterium. To shed light on this topic, it was necessary to understand the key candidate genes essential for regulating susceptibility and resistance to the target disease. The field of poultry farming in particular has benefited greatly from the connection between quantitative and molecular genetics.

OBJECTIVES

This study aims to identify the most important immune-related genes and their signalling pathways (gene ontology, co-expression and interactions) and to analyse their accumulation in host-resistant SE diseases by combining gene expression assays with model-based in silico evidence.

METHODS

A two-step experimental design is followed. To start, we used free computational tools and online bioinformatics resources, including predicting gene function using a multiple association network integration algorithm (geneMania), the Kyoto Encyclopedia of Genes and Genomes, the Annotation, Visualization and Integrated Discovery (DAVID) database and the stimulator of interferon genes. Natural resistance-associated macrophage protein 1 (NRAMP1), Toll-like receptor 4 (TLR4), interferon-γ (IFNγ), immunoglobulin Y (IgY) and interleukin 8 (IL8) were among the five genes whose expression levels in liver, spleen, and cecum were evaluated at 1107 SE after 48 h of inoculation. This molecular study was developed in the second phase of research to validate the in silico observations. Next, we use five promising biomarkers for relative real-time polymerase chain reaction (PCR) quantification: TLR4, IL8, NRAMP1, IFNγ and IgY genes in two case and control assays. The 2-∆∆Ct Livak and Schmittgen method was used to compare the expression of genes in treated and untreated samples. This method normalizes the expression of the target gene to that of actin, an internal control and estimates the change in expression relative to the untreated control. Internal control was provided by the Beta actin gene. Next, statistically, the postdoc test was used for the evaluation of treatments using SAS version 9.4, and p values of 0.05 and 0.01 were chosen for significant level.

RESULTS

Interestingly, the results of our study suggest the involvement of various factors in the host immune response to Salmonella. These include inducible nitric oxide synthase, NRAMP1, immunoglobulin light chain (IgL), transforming growth factor B family (TGFb2, TGFb3 and TGFb4), interleukin 2 (IL2), apoptosis inhibitor protein 1 (IAP1), TLR4, myeloid differentiation protein 2 (MD2), IFNγ, caspase 1 (CASP1), lipopolysaccharide-induced tumour necrosis factor (LITAF), cluster of differentiation 28 (CD28) and prosaposin (PSAP). The summary of gene ontology and related genes found for SE resistance was surprisingly comprehensive and covered the following topics: positive regulation of endopeptidase activity, interleukin-8 production, chemokine production, interferon-gamma production, interleukin-6 production, positive regulation of mononuclear cell proliferation and response to interferon-gamma. The role of these promising biomarkers in our networks against SE susceptibility is essentially confirmed by these results. After 48 h, the spleen showed significant expression of the tissue-specific gene expression patterns for NRAMP1 and IL8 in the cecum, spleen and liver. Based on this information, this report searches for resistance and susceptibility lineages in most genomic regions for SE.

CONCLUSIONS

In conclusion, the development of an appropriate selection program to improve resistance to salmonellosis can be facilitated by a comprehensive understanding of the immune responses of the chicken immune system after SE exposure.

Pyelonephritis with bacteremia caused by Salmonella Choleraesuis in a Japanese patient with carcinoma of unknown primary origin: A case report

Salmonella enterica subspecies enterica serovar Choleraesuis (S. Choleraesuis) is a nontyphoidal Salmonella pathogen that causes swine paratyphoids. S. Choleraesuis is a zoonotic pathogen transmitted to humans via contaminated food and causes sepsis. Here, we report a rare case of pyelonephritis caused by S. Choleraesuis in a Japanese patient with a carcinoma of unknown primary origin. On the day of admission, the patient was diagnosed with pyelonephritis associated with ureteral stent obstruction. He had no history of raw pork consumption or gastrointestinal symptoms. Gram-negative rods were isolated from urine and blood cultures, identified as Salmonella enterica subsp. enterica using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The serological typing results were O7: -: 1 and 5; however, the serotypes could not be determined. The isolate was identified as S. Choleraesuis using multilocus sequence typing, nucleotide sequence analysis of the fliC gene, and biochemical examination. Four days after a 14-day course of intravenous piperacillin-tazobactam (9 g/day), the patient showed relapse of the condition. Subsequently, the patient was treated with intravenous ceftriaxone (2 g/day) and oral amoxicillin (1000 mg/day) for 14 days each; recurrence was not observed. This novel case of pyelonephritis with bacteremia was caused by S. Choleraesuis in Japan. Conventional testing methods could not identify the serotypes; however, the case highlights the importance of adopting advanced diagnostic techniques based on molecular biology to ensure accurate pathogen identification.

Potential Involvement of Reactive Oxygen Species in the Bactericidal Activity of Eugenol against Salmonella Typhimurium

There is an increasing need to develop alternative antimicrobials to replace currently used antibiotics. Phytochemicals, such as essential oils, have garnered significant attention in recent years as potential antimicrobials. However, the mechanisms underlying their bactericidal activities are not yet fully understood. In this study, we investigated the bactericidal activity of eugenol oil against Salmonella enterica serovar Typhimurium (S. Typhimurium) to elucidate its mechanism of action. We hypothesized that eugenol exerts its bactericidal effects through the production of reactive oxygen species (ROS), which ultimately leads to cell death. The result of this study demonstrated that the bactericidal activity of eugenol against S. Typhimurium was significantly (p < 0.05) mitigated by thiourea (ROS scavenger) or iron chelator 2,2'-dipyridyl, supporting the hypothesis. This finding contributes to a better understanding of the killing mechanism by eugenol oil.

Target-inhibited MCOF-Apt-AuNPs self-assembly for multicolor colorimetric detection of Salmonella Typhimurium

Pathogens detection is a crucial measure in the prevention of foodborne diseases. This study developed a novel multicolor colorimetric assay to visually detect Salmonella Typhimurium (S. Typhimurium), by utilizing the etching process of gold nanorods (AuNRs) with TMB2+. The strategy involved the construction of nanozyme by assembling magnetic covalent organic framework (MCOF) with aptamer-conjugated AuNPs (Apt-AuNPs), exhibiting remarkable peroxidase-like activity to catalyze the oxidation of TMB/H2O2 and inducing the etching of AuNRs. The presence of S. Typhimurium could inhibit this process, resulting in the generation of vivid colors. The multicolor colorimetric assay could specifically determine S. Typhimurium from 102 to 108 CFU mL-1 in 60 min with visual detection limit of 102 CFU mL-1, and instrumental detection limit of 2.3 CFU mL-1. Moreover, detecting S. Typhimurium in chicken, milk, pork and lettuce samples has shown promise in practical applications.

Combatting extensively drug-resistant Salmonella: a global perspective on outbreaks, impacts, and control strategies

Antibiotic resistance in typhoid fever poses a critical public health problem due to the emergence of extensively drug-resistant (XDR) Salmonella, resulting in prolonged illness and treatment failure. Salmonella enterica serovar Typhi is the most predominant among all serotypes and can acquire resistance. The emergence of XDR Salmonella in various regions globally, particularly Pakistan, presents a concerning trend. However, limited data availability impedes a comprehensive understanding of the outbreaks and hinders the development of real-time solutions. Here, we have provided an updated overview of the current outbreaks of XDR Salmonella in epidemic and endemic regions. Treatments of XDR Salmonella infections are challenging, as there are records of treatment failure in humans and animals. However, intensive prevention techniques can be implemented pending the advent of novel antibiotics. Emphasis on antimicrobial stewardship and frequent surveillance of the pathogen should be made to keep track of potential outbreaks in both human and animal populations. Although progress is being made to combat XDR Salmonella within some regions, a unified and efficient effort on an international scale is required to curtail the XDR outbreak before it escalates and leads us back to the pre-antibiotic era.

Characterization of two virulent Salmonella phages and transient application in egg, meat and lettuce safety

Salmonella, a prominent foodborne pathogen, has posed enduring challenges to the advancement of food safety and global public health. The escalating concern over antibiotic misuse, resulting in the excessive presence of drug residues in animal-derived food products, necessitates urgent exploration of alternative strategies for Salmonella control. Bacteriophages emerge as promising green biocontrol agents against pathogenic bacteria. This study delineates the identification of two novel virulent Salmonella phages, namely phage vB_SalS_ABTNLsp11241 (referred to as sp11241) and phage 8-19 (referred to as 8-19). Both phages exhibited efficient infectivity against Salmonella enterica serotype Enteritidis (SE). Furthermore, this study evaluated the effectiveness of two phages to control SE in three different foods (whole chicken eggs, raw chicken meat, and lettuce) at different MOIs (1, 100, and 10000) at 4°C. It's worth noting that sp11241 and 8-19 achieved complete elimination of SE on eggs after 3 h and 6 h at MOI = 100, and after 2 h and 5 h at MOI = 10000, respectively. After 12 h of treatment with sp11241, a maximum reduction of 3.17 log10 CFU/mL in SE was achieved on raw chicken meat, and a maximum reduction of 3.00 log10 CFU/mL was achieved on lettuce. Phage 8-19 has the same effect on lettuce as sp11241, but is slightly less effective than sp11241 on chicken meat (a maximum 2.69 log10 CFU/mL reduction). In conclusion, sp11241 and 8-19 exhibit considerable potential for controlling Salmonella contamination in food at a low temperature and represent viable candidates as green antibacterial agents for food applications.

Meat quality and safety issues during high temperatures and cutting-edge technologies to mitigate the scenario

Climate change, driven by the natural process of global warming, is a worldwide issue of significant concern because of its adverse effects on livestock output. The increasing trend of environmental temperature surging has drastically affected meat production and meat product quality, hence result in economic losses for the worldwide livestock business. Due to the increasing greenhouse gas emissions, the situation would get prolonged, and heat exposure-related stress is expected to worsen. Heat exposure causes metabolic and physiological disruptions in livestock. Ruminants and monogastric animals are very sensitive to heat stress due to their rate of metabolism, development, and higher production levels. Before slaughter, intense hot weather triggers muscle glycogen breakdown, producing pale, mushy, and exudative meat with less water-holding capacity. Animals exposed to prolonged high temperatures experience a decrease in their muscle glycogen reserves, producing dry, dark, and complex meat with elevated final pH and increased water-holding capacity. Furthermore, heat stress also causes oxidative stresses, especially secondary metabolites from lipid oxidation, severely affects the functionality of proteins, oxidation of proteins, decreasing shelf life, and food safety by promoting exfoliation and bacterial growth. Addressing the heat-related issues to retain the sustainability of the meat sector is an essential task that deserves an inclusive and comprehensive approach. Considering the intensity of the heat stress effects, this review has been designed primarily to examine the consequences of hot environment temperatures and related stresses on the quality and safety of meat and secondarily focus on cutting edge technology to reduce or alleviate the situational impact.

A Single Base Change in the csgD Promoter Resulted in Enhanced Biofilm in Swine-Derived Salmonella Typhimurium

Pathogenic Salmonella strains causing gastroenteritis typically can colonize and proliferate in the intestines of multiple host species. They retain the ability to form red dry and rough (rdar) biofilms, as seen in Salmonella enterica serovar Typhimurium. Conversely, Salmonella serovar like Typhi, which can cause systemic infections and exhibit host restriction, are rdar-negative. In this study, duck-derived strains and swine-derived strains of S. Typhimurium locate on independent phylogenetic clades and display relative genomic specificity. The duck isolates appear more closely related to human blood isolates and invasive non-typhoidal Salmonella (iNTS), whereas the swine isolates were more distinct. Phenotypically, compared to duck isolates, swine isolates exhibited enhanced biofilm formation that was unaffected by the temperature. The transcriptomic analysis revealed the upregulation of csgDEFG transcription as the direct cause. This upregulation may be mainly attributed to the enhanced promoter activity caused by the G-to-T substitution at position -44 of the csgD promoter. Swine isolates have created biofilm polymorphisms by altering a conserved base present in Salmonella Typhi, iNTS, and most Salmonella Typhimurium (such as duck isolates). This provides a genomic characteristics perspective for understanding Salmonella transmission cycles and evolution.

PEG modification increases thermostability and inhibitor resistance of Bst DNA polymerase

Polyethylene glycol modification (PEGylation) is a widely used strategy to improve the physicochemical properties of various macromolecules, especially protein drugs. However, its application in enhancing the performance of enzymes for molecular biology remains underexplored. This study explored the PEGylation of Bst DNA polymerase, determining optimal modification reaction conditions. In comparison to the unmodified wild-type counterpart, the modified Bst DNA polymerase exhibited significantly improved activity, thermal stability, and inhibitor tolerance during loop-mediated isothermal amplification. When applied for the detection of Salmonella in crude samples, the modified enzyme demonstrated a notably accelerated reaction rate. Therefore, PEGylation emerges as a viable strategy for refining DNA polymerases, helping in the development of novel molecular diagnostic reagents.

Tackling salmonellosis: A comprehensive exploration of risks factors, impacts, and solutions

Salmonellosis, caused by Salmonella species, is one of the most common foodborne illnesses worldwide with an estimated 93.8 million cases and about 155,00 fatalities. In both industrialized and developing nations, Salmonellosis has been reported to be one of the most prevalent foodborne zoonoses and is linked with arrays of illness syndromes such as acute and chronic enteritis, and septicaemia. The two major and most common Salmonella species implicated in both warm-blooded and cold-blooded animals are Salmonella bongori and Salmonella enterica. To date, more than 2400 S. enterica serovars which affect both humans and animals have been identified. Salmonella is further classified into serotypes based on three primary antigenic determinants: somatic (O), flagella (H), and capsular (K). The capacity of nearly all Salmonella species to infect, multiply, and survive in human host cells with the aid of their pathogenic and virulence arsenals makes them deadly and important public health pathogens. Primarily, food-producing animals such as poultry, swine, cattle, and their products have been identified as important sources of salmonellosis. Additionally, raw fruits and vegetables are among other food types that have been linked to the spread of Salmonella spp. Based on the clinical manifestation of human salmonellosis, Salmonella strains can be categorized as either non-typhoidal Salmonella (NTS) and typhoidal Salmonella. The detection of aseptically collected Salmonella in necropsies, environmental samples, feedstuffs, rectal swabs, and food products serves as the basis for diagnosis. In developing nations, typhoid fever due to Salmonella Typhi typically results in the death of 5%-30% of those affected. The World Health Organization (WHO) calculated that there are between 16 and 17 million typhoid cases worldwide each year, with scaring 600,000 deaths as a result. The contagiousness of a Salmonella outbreak depends on the bacterial strain, serovar, growth environment, and host susceptibility. Risk factors for Salmonella infection include a variety of foods; for example, contaminated chicken, beef, and pork. Globally, there is a growing incidence and emergence of life-threatening clinical cases, especially due to multidrug-resistant (MDR) Salmonella spp, including strains exhibiting resistance to important antimicrobials such as beta-lactams, fluoroquinolones, and third-generation cephalosporins. In extreme cases, especially in situations involving very difficult-to-treat strains, death usually results. The severity of the infections resulting from Salmonella pathogens is dependent on the serovar type, host susceptibility, the type of bacterial strains, and growth environment. This review therefore aims to detail the nomenclature, etiology, history, pathogenesis, reservoir, clinical manifestations, diagnosis, epidemiology, transmission, risk factors, antimicrobial resistance, public health importance, economic impact, treatment, and control of salmonellosis.

Biological Activity and Phytochemical Characteristics of Star Anise (Illicium verum) Essential Oil and Its Anti-Salmonella Activity on Sous Vide Pumpkin Model

Illicium verum, commonly known as star anise, represents one of the notable botanical species and is recognized for its rich reservoir of diverse bioactive compounds. Beyond its culinary application as a spice, this plant has been extensively utilized in traditional medicine. Given the contemporary emphasis on incorporating natural resources into food production, particularly essential oils, to enhance sensory attributes and extend shelf life, our study seeks to elucidate the chemical composition and evaluate the antibacterial (in vitro, in situ) and insecticidal properties of Illicium verum essential oil (IVEO). Also, microbiological analyses of pumpkin sous vide treated with IVEO after inoculation of Salmonella enterica were evaluated after 1 and 7 days of study. GC/MS analysis revealed a significantly high amount of (E)-anethole (88.4%) in the investigated EO. The disc diffusion method shows that the antibacterial activity of the IVEO ranged from 5.33 (Streptococcus constellatus) to 10.33 mm (Citrobacter freundii). The lowest minimal inhibition concentration was found against E. coli and the minimum biofilm inhibition concertation was found against S. enterica. In the vapor phase, the best antimicrobial activity was found against E. coli in the pears model and against S. sonei in the beetroot model. The application of the sous vide method in combination with IVEO application decreased the number of microbial counts and eliminated the growth of S. enterica. The most isolated microbiota identified from the sous vide pumpkin were Bacillus amyloliquefaciens, B. cereus, B. licheniformis, and Ralstonia picketii. Modifications to the protein composition of biofilm-forming bacteria S. enterica were suggested by the MALDI TOF MS instigations. The IVEO showed insecticidal potential against Harmonia axyridis. Thanks to the properties of IVEO, our results suggest it can be used in the food industry as a natural supplement to extend the shelf life of foods and as a natural insecticide.

Fermentation of Rubus dolichocarpus juice using Lactobacillus gasseri and Lacticaseibacillus casei and protecting phenolic compounds by Stevia extract during cold storage

This study aimed to investigate the biological activities of Lactobacillus gasseri SM 05 (L. gasseri) and Lacticaseibacillus casei subsp. casei PTCC 1608 (L. casei) in the black raspberry (Rubus dolichocarpus) juice (BRJ) environment, and also the anti-adhesion activity against Salmonella typhimurium (S. typhimurium) in fermented black raspberry juice (FBRJ). Results showed significant anti-adhesion activity in Caco-2 epithelial cells. In the anti-adhesion process, lactic acid bacteria (LAB) improve intestinal health by preventing the adhesion of pathogens. Adding LAB to BRJ produces metabolites with bacteriocin properties. Major findings of this research include improved intestinal health, improved antidiabetic properties, inhibition of degradation of amino acids, and increase in the nutritional value of foods that have been subjected to heat processing by preventing Maillard inhibition, and inhibition of oxidation of foodstuff by increased antioxidant activity of BRJ. Both species of Lactobacillus effectively controlled the growth of S. typhimurium during BRJ fermentation. Moreover, in all tests, as well as Maillard's and α-amylase inhibition, L. gasseri was more effective than L. casei. The phenolic and flavonoid compounds increased significantly after fermentation by both LAB (p < 0.05). Adding Stevia extract to FBRJ and performing the HHP process showed convenient protection of phenolic compounds compared to heat processing.

Sophy β-Glucan from the Black Yeast Aureobasidium pullulans Attenuates Salmonella-Induced Intestinal Epithelial Barrier Injury in Caco-2 Cell Monolayers via Exerting Anti-Oxidant and Anti-Inflammatory Properties

The zoonotic pathogens Salmonella spp. infection disrupted intestinal epithelial barrier function and induced local gastroenteritis and systemic inflammation in humans and animals. Sophy β-glucan, a water-soluble β-1,3/1,6-glucan synthesized from the black yeast Aureobasidium pullulans, was reported with immune-regulatory, anti-inflammatory, and anti-infective properties. Here, we investigated the protective role of sophy β-glucan on Salmonella enterica serotype Enteritidis (SE)-challenged Caco-2 cells monolayer and explored underlying action mechanisms. The results showed that pretreatment with sophy β-glucan blocked the adhesion and invasion of SE onto Caco-2 cells along with alleviating SE-induced epithelial barrier injury, as evidenced by increased trans-epithelial electrical resistance, decreased fluorescently-labeled dextran 4 flux permeability, and an enhanced Claudin-4 protein level in the SE-stimulated Caco-2 cell monolayer. Moreover, treatment with β-glucan down-regulated pro-inflammatory factors (IL-1β, IL-8, and TNF-α) while up-regulating anti-inflammatory factors IL-10 at mRNA and protein levels in SE-infected Caco-2 cells. Furthermore, sophy β-glucan strengthened the anti-oxidative capacity of Caco-2 monolayers cells by elevating T-AOC and SOD activity and inhibiting MDA production defending SE. Together, our data showed that sophy β-glucan could prevent intestinal epithelial injury induced by SE, possibly by exerting anti-oxidant and anti-inflammatory properties, and it might be helpful for controlling SE infection.