Human Salmonellosis: A Continuous Global Threat in the Farm-to-Fork Food Safety Continuum

A novel duplex qPCR-HRMA technique for simultaneous detection of Listeria monocytogenes and Salmonella typhimurium in meat products

Developing rapid, accurate, and sensitive methods to detect bacterial pathogens such as Listeria monocytogenes and Salmonella typhimurium is very important, given the global rise in foodborne outbreaks. To address this, we developed a duplex real-time PCR assay with high-resolution melting analysis (qPCR-HRMA) to detect these pathogens in meat products. The assay was standardized and validated according to ISO 22118:2011. The assay was optimized for basic PCR parameters and melting rate for HRM analysis. The reaction sensitivity was determined to be 2 pg of DNA, equivalent to 124 copies for Listeria monocytogenes and 100 copies for Salmonella typhimurium. The method sensitivity was found to be 150 CFU/mL for both pathogens in spiked meat samples. The assay was validated with proficiency test samples and was finally used to test real-world samples, where 4 samples were detected positive for the pathogens. This assay holds significant potential for regulatory food testing and clinical investigations.

The changing landscape of nontyphoidal salmonellosis: epidemiological patterns, imported cases and serovar distribution in Germany from 2012 to 2023

INTRODUCTION

Nontyphoidal Salmonella is a zoonotic foodborne pathogen that represents a global public health issue. In the European Union and Economic Area, about 66,000 cases of reported nonthyphoidal salmonellosis occurred in 2022, with about 9,100 cases in Germany. The aim of this study is to analyse the incidence and epidemiological characteristics as well as trends of salmonellosis in Germany from 2012 to 2023.

METHODS

German national surveillance data on salmonellosis from 2012 to 2023 were analysed. Available information included demographics, notification dates, country of exposure, hospitalisation, and serovar. The incidence was calculated per 100,000 population, stratified by age, sex, and travel and hospitalisation history. A descriptive analysis was conducted.

RESULTS

A total of 160,782 cases of salmonellosis were reported between 2012 and 2023 in Germany, with seasonal peaks occurring during the summer months. The incidence declined from 26 per 100,000 in 2012 to 13 per 100,000 in 2023. This decline was observed across all defined age groups, sex and regions. The proportion of imported cases increased since 2012, reaching a peak of 26% (n = 1,943) in 2023. The proportion of cases that resulted in hospitalisation remained relatively constant, accounting for approximately 30% of all cases. The incidence was higher in males and children under the age of five years. The most frequent serovars were S. Enteritidis and S. Typhimurium. From 2020 onwards, there was an increase in the number of unknown serovars.

CONCLUSION

The analysis of these surveillance data provided a good basis to monitor trends and to identify special population groups at risk. The decrease in the incidence of salmonellosis in Germany between 2012 and 2023 might reflect a positive trend in public health efforts and food safety. The increased proportion of imported cases highlights the higher importance of monitoring and addressing travel-related exposures. Ongoing efforts are essential to mitigate both domestic and imported salmonellosis cases, particularly in young children and older adults.

Candida species covered from traditional cheeses: Characterization of C. albicans regarding virulence factors, biofilm formation, caseinase activity, antifungal resistance and phylogeny

This study has provided characterization data (carriage of virulence, antifungal resistance, caseinase activity, biofilm-forming ability and genotyping) of Candida albicans isolates and the occurrence of Candida species in traditional cheeses collected from Kayseri, Türkiye. Phenotypic (E-test, Congo red agar and microtiter plate tests) and molecular tests (identification, virulence factors, biofilm-formation, antifungal susceptibility) were carried out. The phylogenetic relatedness of C. albicans isolates was obtained by constructing the PCA dendrogram from the mass spectra data. Of 102 samples, 13 (12.7%) were found to be contaminated with C. albicans, 15 (14.7%), 10 (9.8%) and five (4.9%) were found to be contaminated with C. krusei, C. lusitane and C. paraplosis, respectively. While seven (16.2%) of 43 Candida spp. isolates were obtained from cheese collected from villages, 36 (83.7%) belonged to cheeses collected from traditional retail stores. The carriage rate of C. albicans isolates belonging to virulence factors HSP90 and PLB1 genes was 30.7%. ALST1, ALST3, BCR, ECE, andHWP (virulence and biofilm-associated) genes were harbored by 30.7%, 23%, 38.4%, 53.8%, and 38.4% of the 13 isolates. According to the microplate test, eight (61.5%) of 13 isolates had strong biofilm production. ERG11 and FKS1 (antifungal resistance genes) were found in 46.1% and 23% of 13 isolates, respectively. Due to missense mutations, K128T, E266D and V488I amino acid changes were detected for some isolates regarding azole resistance. As a result of the E-test, of the 13 isolates, one (7.6%) was resistant to flucytosine, four (30.7%) were resistant to caspofungin, and nine (69.2%) were resistant to fluconazole. The PCA analysis clustered the studied isolates into two major clades. C. albicans isolates of traditional cheese collected from villages were grouped in the same cluster. Among the C. albicans isolates from village cheese, there were those obtained from the same dairy milk at different times. Samples from the same sales points produced at different dairy farms were also contaminated with C. albicans. Concerning food safety standards applied from farm to fork, in order to prevent these pathogenic agents from contaminating cheeses, attention to the hygiene conditions of the sale points, conscious personnel, prevention of cross contamination will greatly reduce public health threats in addition to the application of animal health control, milking hygiene, pasteurization parameters in traditional cheese production.

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.

Prevalence, antibiotic resistance, virulence and antimicrobial resistance gene profiles of Salmonella species recovered from retail beef and poultry processing environments

BACKGROUND

This study investigates the prevalence, antimicrobial resistance, genotypic resistance profiles, and virulence gene distribution of Salmonella isolates from poultry and beef processing environments in Shahrekord, Iran.

METHOD

A total of 680 samples were collected from poultry (n = 300) and beef (n = 380) products between January and December 2023.

RESULTS

Salmonella was detected in 21% (63/300) of poultry samples and 15.8% (60/380) of beef samples, with non-typhoidal Salmonella (NTS) being the predominant serovar. High antimicrobial resistance (AMR) rates were observed across both food types, with the most common resistances found in ciprofloxacin (48%), tetracycline (44%), and ampicillin (39%). Genotypic analysis revealed the presence of key resistance genes, including blaTEM (35%), tetA (29%), and sul1 (23%). Virulence gene analysis identified invA (92%), agfA (80%), and hilA (76%) as the most prevalent genes. Comparative analysis of resistance patterns between poultry and beef samples revealed higher resistance in poultry isolates to ciprofloxacin and tetracycline.

CONCLUSION

This study highlights significant antimicrobial resistance and the presence of virulence factors in Salmonella isolates from retail beef and poultry, suggesting a potential risk to public health and the need for enhanced surveillance and control measures in food processing environments.

CLINICAL TRIAL NUMBER

Not applicable.

Nanobody-Based Immunoassays for the Detection of Food Hazards-A Review

Food safety remains a significant global challenge that affects human health. Various hazards, including microbiological and chemical threats, can compromise food safety throughout the supply chain. To address food safety issues and ensure public health, it is necessary to adopt rapid, accurate, and highly specific detection methods. Immunoassays are considered to be an effective method for the detection of highly sensitive biochemical indicators and provide an efficient platform for the identification of food hazards. In immunoassays, antibodies function as the primary recognition elements. Nanobodies have significant potential as valuable biomolecules in diagnostic applications. Their distinctive physicochemical and structural characteristics make them excellent candidates for the development of reliable diagnostic assays, and as promising alternatives to monoclonal and polyclonal antibodies. Herein, we summarize a comprehensive overview of the status and prospects of nanobody-based immunoassays in ensuring food safety. First, we begin with a historical perspective on the development of nanobodies and their unique characteristics. Subsequently, we explore the definitions and boundaries of immunoassays and immunosensors, before discussing the potential applications of nanobody-based immunoassays in food safety testing that have emerged over the past five years, and follow the different immunoassays, highlighting their advantages over traditional detection methods. Finally, the directions and challenges of nanobody-based immunoassays in food safety are discussed. Due to their remarkable sensitivity, specificity and versatility, nanobody-based immunoassays hold great promise in revolutionizing food safety testing and ensuring public health and well-being.

Rhamnolipids functionalized intrinsically active liposomes loaded with cinnamaldehyde: Potent antimicrobial and antibiofilm activity against Salmonella Typhimurium and Salmonella Enteritidis

Intrinsically active rhamnolipids functionalized liposomes (rhamnosomes) as a carrier for cinnamaldehyde were developed to enhance the antibacterial activity against foodborne Salmonella isolates. Stable rhamnosomes were optimized with an excellent encapsulation efficiency of 85 ± 1%. SEM revealed slightly rough surface morphology and the mean diameter was slightly increased after the incorporation of cinnamaldehyde in rhamnosomes from 77 to 137 ± 2 nm. However, negative zeta-potential values were reduced from -18.2 ± 4 mV to - 13.4 ± 2 mV for cinnamaldehyde-loaded rhamnosomes. FTIR analyses revealed chemical interactions between rhamnolipids and phospholipids, which facilitated the development of rhamnosomes. Cinnamaldehyde-loaded rhamnosomes exhibited higher anti-Salmonella activity as compared to free cinnamaldehyde and void-rhamnosomes, and 75-80% reduction in biomass was observed due to their enhanced binding with the bacterial membrane in the antibiofilm assays. Antimicrobial results revealed that cinnamaldehyde-loaded rhamnosomes inhibited bacterial growth, displayed adequate biocompatibility and stability while providing an innovative strategy to control foodborne-resistant pathogens.

Salmonella: Infection mechanism and control strategies

Salmonella is a foodborne pathogen that predominantly resides in the intestinal tract of humans and animals. Infections caused by Salmonella can lead to various illnesses, including gastroenteritis, bacteremia, septicemia, and focal infections, with severe cases potentially resulting in host mortality. The mechanisms by which Salmonella invades host cells and disseminates throughout the body are partly understood, but there are still many scientific questions to be solved. This review aims to synthesize existing research on the interactions between Salmonella and hosts, detailing a comprehensive infection mechanism from adhesion and invasion to intracellular propagation and systemic spread. Overuse of antibiotics contributes to the emergence of drug-resistant Salmonella strains. An in-depth analysis of the mechanism of Salmonella infection will provide a theoretical basis for the development of novel Salmonella control strategies. These innovative control strategies include antibiotic adjuvants, small molecules, phages, attenuated vaccines, and probiotic therapies, which show huge potential in controlling Salmonella infection.

Ecotin protects Salmonella Typhimurium against the microbicidal activity of host proteases

Salmonella enterica serovar Typhimurium causes acute diarrhea upon oral infection in humans. The harsh and proteolytic environment found in the gastrointestinal tract is the first obstacle that these bacteria face after infection. However, the mechanisms that allow Salmonella to survive the hostile conditions of the gut are poorly understood. The ecotin gene is found in an extensive range of known phyla of bacteria and it encodes a protein that has been shown to inhibit serine proteases. Thus, in the present work we studied the role of ecotin of Salmonella Typhimurium in host-pathogen interactions. We found that the Salmonella Typhimurium ∆ecotin strain exhibited lower inflammation in a murine model of Salmonella induced colitis. The ∆ecotin mutant was more susceptible to the action of pancreatin and purified pancreatic elastase. In addition, the lack of ecotin led to impaired adhesion to Caco-2 and HT-29 cell lines, related to the proteolytic activity of brush border enzymes. Besides, ∆ecotin showed higher susceptibility to lysosomal proteolytic content and intracellular replication defects in macrophages. In addition, we found Ecotin to have a crucial role in Salmonella against the microbicidal action of granule contents and neutrophil extracellular traps released from human polymorphonuclear leukocytes. Thus, the work presented here highlights the importance of ecotin in Salmonella as countermeasures against the host proteolytic defense system.

Prevalence and Distribution of Salmonella in Water Bodies in South America: A Systematic Review

The presence of Salmonella in rivers, lakes, or beaches in South America represents a challenge to public health and aquatic ecosystems. This review explores the distribution, prevalence, and the main factors contributing to the survival and spread of Salmonella, including wastewater discharge, agricultural runoff, and climatic variables such as high temperatures and precipitation. These factors also facilitate the distribution of multidrug-resistant strains in water. The review is based on bibliographic searches in various databases, focusing on Salmonella species, South American countries, and types of water bodies. Predominant serovars include S. Enteritidis and S. Typhimurium, with S. Typhi and S. Panama frequently detected in Chile, S. Enteritidis in Argentina, and S. Typhimurium in Brazil. Less common serovars, including S. Dublin and S. Paratyphi B, were identified, along with subspecies such as diarizonae and houtenae. These findings highlight the role of environmental, physicochemical, and anthropogenic factors influencing Salmonella dynamics. The review identifies research gaps, advocating for further studies to better understand the interactions between Salmonella, climate change, and human activity. Strengthening surveillance and mitigation strategies is crucial to protect water resources and public health in South America.

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.

A Colorimetric LAMP Assay for Salmonella spp. Detection: Towards a DNA Extraction-Free Approach for Pathogen Screening

As of today, bacteriological identification and the molecular approach PCR are considered the gold standards for Salmonella spp. detection. However, these methods are time-consuming and costly due to the requirements for enrichment and nucleic acid extraction. In this study, we evaluated the reliability of a developed colorimetric loop-mediated isothermal amplification (cLAMP) assay targeting the hilA gene, using Phenol Red as an amplification indicator. Given that Phenol Red is pH-dependent, and to develop an extraction-free test, we evaluated chicken meat pretreatment and thermal treatment. First, we assessed the reliability of this test using a pure culture of Salmonella spp. and then in 50 chicken samples pretreated with optimal NaOH concentrations under standardized conditions. Samples representing extreme pH values were artificially contaminated and subjected to DNA extraction and a heat-treatment protocol. Serial dilutions of these products served as templates for LAMP reactions. The assay sensitivity was estimated to be around 3.9 CFU/µL of pure bacterial culture. In contrast, in biological samples, we detected up to 10 CFU/µL using DNA extraction, while heat treatment successfully amplified the initial solution and even some dilutions up to 103 CFU/µL. In conclusion, our cLAMP assay demonstrated good sensitivity and provided clear evidence of its potential for in-field use without relying on prior enrichment steps and DNA extraction.

Isolation and characterization of Salmonella Typhimurium monophasic variant phage and its application in foods

Salmonella Typhimurium monophasic variant (STm) is an emerging Salmonella serotype that causes food poisoning through the contamination of various foods, including animal products, vegetables, and fruits. In particular, the increasing prevalence of multidrug-resistant STm highlights the urgent need to develop effective strategies to control this pathogen. In this work, a novel and broad-spectrum Salmonella phage named vB_Sal_TmvP009 was isolated and characterized. Morphological and genomic analyses revealed that phage vB_Sal_TmvP009 belonged to the genus Jerseyvirus. Phage vB_Sal_TmvP009 was tolerant to a wide range of temperatures (-20°C∼60°C) and pH values (3∼12). The optimal multiplicity of phage infection was 0.0001, and it had a shorter latent period (8 min), longer lysis period (70 min), and a burst size of 292 PFU/cell. A total of 13 Salmonella serotypes could be lysed by phage vB_Sal_TmvP009. Furthermore, phage vB_Sal_TmvP009 inhibited the growth of multidrug-resistant Salmonella in lettuce or milk with the highest suppression of 3.4 and 3.7 log CFU/mL within 24 h, respectively. The genome of phage vB_Sal_TmvP009 contains lysin and spanin protein, but no tRNA, virulence factors, or drug resistance-related genes. These findings suggest that phage vB_Sal_TmvP009 is a promising antibacterial agent for controlling Salmonella in the food industry.

Comparative Patho-Genomics of Salmonella enterica Serovar Enteritidis Reveal Potential Host-Specific Virulence Factors

Salmonella enterica serovar Enteritidis (S. Enteritidis) is one of the most common causes of bacterial foodborne infections worldwide. It has an extensive host range, including birds and humans, making it one of the most adaptable Salmonella serovars. This study aims to define the virulence gene profile of S. Enteritidis and identify genes critical to its host specificity. Currently, there is limited understanding of the molecular mechanisms that allow S. Enteritidis to continue as an important foodborne pathogen. To better understand the genes that may play a role in the host-specific virulence and/or fitness of S. Enteritidis, we first compiled a virulence gene profile-based genome analysis of sequenced S. Enteritidis strains isolated from shell eggs in our laboratory. This analysis was subsequently used to compare the representative genomes of Salmonella serovars with varying host ranges and S. Enteritidis genomes. The study involved a comprehensive and direct examination of the conservation of virulence and/or fitness factors, especially in a host-specific manner-an area that has not been previously explored. Key findings include the identification of 10 virulence-associated clusters of orthologous genes (COGs) specific to poultry-colonizing serovars and 12 virulence-associated COGs unique to human-colonizing serovars. Virulence/fitness-associated gene analysis identified more than 600 genes. The genome sequences of the two S. Enteritidis isolates were compared to those of the other serovars. Genome analysis revealed a core of 2817 COGs that were common to all the Salmonella serovars examined. Comparative genome analysis revealed that 10 virulence-associated COGs were specific to poultry-colonizing serovars, whereas 12 virulence-associated COGs were present in all human-colonizing serovars. Phylogenetic analyses further highlight the evolution of host specificity in S. Enteritidis. This study offers the first comprehensive analysis of genes that may be unique to and possibly essential for the colonization and/or pathogenesis of S. Enteritidis in various and specific hosts.

Prevalence and transmission of Salmonella collected from farming to egg processing of layer production chain in Jiangsu Province, China

Salmonella is a common foodborne pathogen found in poultry production systems. Contaminated poultry products are a major source of human salmonellosis. Understanding the conditions of contamination and the genetic relationships of Salmonella in poultry production is necessary to develop effective interventions measures for controlling Salmonella transmission. Through epidemiological investigation and whole-genome sequence (WGS) analysis, this study revealed the epidemic law, drug resistance, and genetic characteristics of Salmonella in the production chain. In total, 130 (10.77 %) Salmonella strains were isolated from the collected samples, with Salmonella Enteritidis (S. Enteritidis) and S. Infantis being the predominant serotypes. WGS analysis revealed that the Sequence Type (ST) of all the 22 strains of S. Enteritidis were ST11, and 13 strains of S. Infantis were ST32. Antimicrobial resistance gene analysis showed that 95.45 % of S. Enteritidis carried strA/strB, sul, and blaTEM-1B; 77.3 % contained tetA genes; and 100 % of S. Infantis carried aac(6')-Iaa and mdf(A), which was consistent with the drug resistance phenotype. The phylogenetic tree showed that S. Enteritidis strains with different links were distributed in the same branch which displayed the very close genetic relationship. Combined with epidemiological investigations, it was found that S. Enteritidis infection begins at the chicken breeding stage and spreads vertically and horizontally along the production chain. In addition, phylogenetic tree analysis of S. Infantis showed that the genomes of 13 strains from egg products and egg collection center were very similar and belonged to the same clone cluster. It is speculated that the S. Infantis transmitted in the industrial chain is the same strain; it can spread along the industrial chain, and cross-contamination may occur. This study indicates that Salmonella contamination in the layered industrial chain is more serious and that a cloning relationship exists among the strains of different links. Therefore, more stringent measures should be taken to control Salmonella during the chicken breeding stage, and the importance of implementing good hygiene practices at every level of production should be emphasized.

Identifying freshness of various chilled pork cuts using rapid imaging analysis

BACKGROUND

Determining the freshness of chilled pork is of paramount importance to consumers worldwide. Established freshness indicators such as total viable count, total volatile basic nitrogen and pH are destructive and time-consuming. Color change in chilled pork is also associated with freshness. However, traditional detection methods using handheld colorimeters are expensive, inconvenient and prone to limitations in accuracy. Substantial progress has been made in methods for pork preservation and freshness evaluation. However, traditional methods often necessitate expensive equipment or specialized expertise, restricting their accessibility to general consumers and small-scale traders. Therefore, developing a user-friendly, rapid and economical method is of particular importance.

RESULTS

This study conducted image analysis of photographs captured by smartphone cameras of chilled pork stored at 4 °C for 7 days. The analysis tracked color changes, which were then used to develop predictive models for freshness indicators. Compared to handheld colorimeters, smartphone image analysis demonstrated superior stability and accuracy in color data acquisition. Machine learning regression models, particularly the random forest and decision tree models, achieved prediction accuracies of more than 80% and 90%, respectively.

CONCLUSION

Our study provides a feasible and practical non-destructive approach to determining the freshness of chilled pork. © 2024 Society of Chemical Industry.

Farm-to-fork changes in poultry microbiomes and resistomes in Maputo City, Mozambique

Increasing demand for poultry has spurred poultry production in low- and middle-income countries like Mozambique. Poultry may be an important source of foodborne, antimicrobial-resistant bacteria to consumers in settings with limited water, sanitation, and hygiene infrastructure. The Chicken Exposures and Enteric Pathogens in Children Exposed through Environmental Pathways (ChEEP ChEEP) study was conducted in Maputo City, Mozambique from 2019 to 2021 to quantify enteric pathogen exposures along the supply chain for commercial and local (i.e., scavenger) chicken breeds. Here, we performed metagenomic sequencing of total DNA from banked ChEEP ChEEP samples to characterize fecal and carcass microbiomes and resistome diversity between chicken breeds and along the supply chain. Fecal samples (n = 26) were collected from commercial and local chickens at production sites and markets and carcass (n = 49) and rinse bucket samples (n = 26) from markets. We conducted taxonomic profiling and identified antimicrobial resistance genes (ARGs) from metagenomic sequence data, focusing especially on potential human pathogens and "high-risk" ARGs. We estimated alpha diversity for each sample and compared by site and breed. We estimated Bray-Curtis dissimilarity between samples and examined clustering. We found that commercial and local chickens harbored distinct fecal potential pathogens and resistomes at production and market sites. Many potentially pathogenic bacteria and ARGs present in chicken fecal samples are also present on carcasses sold to consumers. Finally, commercial chicken carcasses contain high-risk ARGs that are not necessarily introduced from chicken feces. These results indicate markets are an important site of exposure to potentially pathogenic bacteria and high-risk ARGs.

IMPORTANCE

While chicken eggs and meat are a critical protein source in low-income settings, antibiotics are routinely fed to chickens with consequences for selection of antimicrobial resistance. Evaluating how poultry gut bacterial communities, including potential human pathogens and high-risk antimicrobial resistance genes, differ from farm to market could help identify where to target interventions to minimize transmission risks to human populations. In this study in Maputo City, Mozambique, we found compositional differences between commercial and local chicken breeds at production and market sites. We also found that while all potentially pathogenic bacteria and many high-risk antimicrobial resistance genes persisted from production and market through processing, some resistance genes were detected on carcass samples only after processing, suggesting human or environmental contamination is occurring within markets. Overall, our findings indicate that open-air markets may represent a critical juncture for human exposures to pathogens and antimicrobial resistance genes from poultry and poultry products.

Combatting Salmonella: a focus on antimicrobial resistance and the need for effective vaccination

BACKGROUND

Salmonella infections represent a major global public health concern due to their widespread zoonotic transmission, antimicrobial resistance, and associated morbidity and mortality. This review aimed to summarize the zoonotic nature of Salmonella, the challenges posed by antimicrobial resistance, the global burden of infections, and the need for effective vaccination strategies to mitigate the rising threat of Salmonella.

METHODS

A systematic review of literature was conducted using databases such as PubMed, Scopus, Web of Science, and Google Scholar. Relevant studies published in English were identified using keywords including Salmonella, vaccination, antimicrobial resistance, and public health. Articles focusing on epidemiology, vaccine development, and strategies to control Salmonella infections were included, while conference abstracts and non-peer-reviewed studies were excluded.

RESULTS

Salmonella infections result in approximately 95 million global cases annually, with an estimated 150,000 deaths. Regional variations were evident, with higher infection rates in low- and middle-income countries due to poor sanitation and food safety standards. Salmonella Enteritidis and S. Typhimurium were the most prevalent serovars associated with human infections. The review highlighted an alarming rise in multidrug-resistant (MDR) Salmonella strains, particularly due to the overuse of antibiotics in humans and livestock. Despite progress in vaccine development, challenges remain in achieving a universal vaccine that targets diverse Salmonella serovars. Live-attenuated, killed, recombinant, subunit, and conjugate vaccines are currently under development, but limitations such as efficacy, cost, and accessibility persist.

CONCLUSIONS

Salmonella infections continue to impose a significant burden on global health, exacerbated by rising antimicrobial resistance. There is an urgent need for a multifaceted approach, including improved sanitation, prudent antibiotic use, and the development of affordable, broad-spectrum vaccines. Strengthening surveillance systems and promoting collaborative global efforts are essential to effectively control and reduce the burden of Salmonella.

Food Pathways of Salmonella and Its Ability to Cause Gastroenteritis in North Africa

Infections caused by human pathogenic bacteria in food sources pose significant and widespread concerns, leading to substantial economic losses and adverse impacts on public health. This review seeks to shed light on the recent literature addressing the prevalence of Salmonella in the food supply chains of North African countries. Additionally, it aims to provide an overview of the available information regarding health-related concerns, such as virulence genes, and the presence of antibiotic resistance in Salmonella. This review highlights a gap in our comprehensive understanding of Salmonella prevalence in the food supply chains of North African nations, with limited molecular characterization efforts to identify its sources. Studies at the molecular level across the region have shown the diversity of Salmonella strains and their virulence profiles, thus, these results show the difficulty of controlling Salmonella infections in the region. In addition, the discussion of antibiotic resistance makes it clear that there is a need for the development of comprehensive strategies to fight the potential threat of antimicrobial resistance in Salmonella strains. Despite common reports on animal-derived foods in this region, this review underscores the persistent challenges that Salmonella may pose to food safety and public health in North African countries.

Emerging Resistance and Virulence Patterns in Salmonella enterica: Insights into Silver Nanoparticles as an Antimicrobial Strategy

BACKGROUND/OBJECTIVES

This study aims to characterize antibiotic resistance (AR) and virulence markers in Salmonella spp. isolated from Romanian outpatients' stool samples.

METHODS

In 2019, community-acquired Salmonella strains were collected and identified using MALDI-TOF mass spectrometry, antibiotic susceptibility profiles have been determined with the MicroScan system, and soluble virulence factors were evaluated using specific culture media, while biofilm formation was quantified in 96-well plates. Molecular analysis targeted resistance genes for β-lactams (e.g., blaTEM and blaSHV); tetracyclines (e.g., tet(A)); sulphonamides; and quinolones, as well as virulence genes (e.g., invA, spvC, pldA, and held). Whole-genome sequencing (WGS) was performed on 19 selected isolates. A silver nanoparticles (AgNPsol) alternative to conventional antibiotics was tested for effectiveness against multidrug-resistant (MDR) isolates.

RESULTS

From the total of 309 Salmonella isolates (65.05% from children under 4 years of age) belonging to four subtypes and four serovars, 27.86% showed resistance to at least one antibiotic, most frequently to tetracycline, ampicillin, and piperacillin. The strains frequently expressed haemolysin (67%), aesculinase (65%), and gelatinase (62%). Resistance to trimethoprim-sulfamethoxazole was encoded by the sul1 gene in 44.83% of the strains and to tetracyclines by the tet(A) gene (59.52%). The ESBL genes blaTEM, blaSHV, and blaCTX-M were detected by PCR in 16.18%, 2.91%, and 0.65% of the strains, respectively. Additionally, 98.63% of the strains carried the invA marker, with notable positive associations between blaSHV, qnrB, and sul1 with spvC.

CONCLUSIONS

The present findings revealed significant patterns in Salmonella isolates, subtypes, serovars, AR, and virulence, emphasising the need for continuous surveillance of Salmonella infections. Additionally, the potential of AgNPs as an alternative treatment option was demonstrated, particularly for paediatric S. enterica infections.

Innovative approaches to controlling Salmonella in the meat industry

Salmonella, a Gram-negative, rod-shaped bacterium from the Enterobacteriaceae family, is a significant cause of illnesses in humans and animals. It resides in the digestive tracts of livestock, poultry, and other warm-blooded animals and can contaminate various environments and foods through fecal matter. Salmonella enterica, the main species that affects humans, is widespread in cattle, pigs, and poultry. Despite efforts to control pathogens in meat systems, over 1.4 million human salmonellosis cases occur annually in the U.S., with serotypes S. enteritidis and S. typhimurium being predominant. Advances in meat processing have targeted pathogen reduction at multiple stages, but more innovative approaches are needed for substantial public health impact. This paper discusses current and future strategies to minimize Salmonella in the food supply. It emphasizes pre- and post-harvest Salmonella prevalence by biomapping it through the whole processing chain, focusing on beef and pork interventions such as probiotics. These interventions have shown promise in reducing pathogen loads in cattle manure and lymph nodes. Techniques such as microbiome, whole genome sequencing (WGS), and electron microscopy (EM) provide detailed insights into Salmonella's genetic and bacterial structural-morphological characteristics, aiding in the development of targeted interventions. Integrating rapid detection, biomapping, and enviromapping enhances pathogen tracking in meat production, reducing Salmonella prevalence and improving risk assessment and food safety. The advanced, current, and innovative techniques allow for timely identification, detailed spatial and quantitative data, and more effective interventions. This leads to safer food products and reduces foodborne illnesses.

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.

In vitro characterization and genome sequencing of two novel lytic phages against Salmonella Infantis isolated from poultry feces

Introduction

Salmonella spp. is the second most common bacteria associated with foodborne gastrointestinal outbreaks in humans, with the highest contamination levels in meat, especially poultry. Salmonella enterica subsp. enterica serovar Infantis is the primary serovar isolated from broilers, without causing any symptomatic disease. Conversely, certain human strains can result in symptomatic illness (fever, headache, and diarrhoea). Therefore, reducing S. Infantis colonization in broilers is important before slaughter, to prevent this pathogen carryover along the food chain.

Methods

Here, we report the characterization of two S. Infantis virulent phages, isolated from broiler feces. Isolates were phenotypically and genetically characterized.

Results and discussion

Phages (ɸ) SaI_NFG_5581 and SaI_NFG_5577 were characterized as strictly lytic versus S. Infantis but with different bacteriolytic activities and genetic features. They both belong to the Caudoviricetes class, but ɸSaI_NFG_5581 (genome length 112,970 bp) belongs to the Demerecviridae family while ɸSaI_NFG_5577 (genome length 42,481 bp) to the Guernseyvirinae family. Genomic analysis excluded the presence of lysogeny, toxin, or antimicrobial resistance genes, and for those reasons, the two phages could be considered safe. Phages are stable under a broad range of pH (4-10) and temperature (4°C-50°C) conditions. In vitro, both ɸSaI_NFG_5581 and ɸSaI_NFG_5577 were able to lower Salmonella counts of about 2.2 LOG/mL and 3.4 LOG CFU/mL respectively, at MOI 0.1 after 2 h of treatment. After 24 h, Salmonella counts treated with both phages remained lower than the control (non-phage-treated Salmonella). These newly isolated phages have promising features, which could be exploited and further studied for potential in vivo application.

Refining the gut colonization Zophobas morio larvae model using an oral administration of multidrug-resistant Escherichia coli

BACKGROUND

The darkling beetle Zophobas morio can be implemented as an alternative in vivo model to study different intestinal colonization aspects. Recently, we showed that its larvae can be colonized by multidrug-resistant Escherichia coli strains administered via contaminated food (for 7 d) for a total experimental duration of 28 d.

METHOD

In the present work, we aimed to shorten the model to 14 d (T14) by administering the previously used CTX-M-15 extended-spectrum β-lactamase-producing ST131 E. coli strain Ec-4901.28 via a single oral administration (5 µL dose of 108 CFU/mL), using a blunt 26s-gauge needle connected to a 250 μL gastight syringe. Force-feeding was performed either without or with (larvae placed on ice for 10 min before injection) anaesthesia. In addition, phage-treated larvae were orally injected with 10 µL of INTESTI bacteriophage cocktail (∼105-6 PFU/mL) on d 4 (T4) and 7 (T7).

RESULTS

Growth curve analyses showed that, while larvae rapidly became colonized with Ec-4901.28 (T1, ∼106-7 CFU/mL), only those anaesthetized maintained a high bacterial load (∼102-3 vs. ∼105-6 CFU/mL) and survival rate (76% vs. 99%; P < 0.001) by T14. Moreover, bacteriophage administration to anaesthetized larvae significantly reduced the bacterial count of INTESTI-susceptible Ec-4901.28 at T14 (5.17 × 105 vs. 2.26 × 104, for non-treated and phage-treated larvae, respectively; P = 0.04).

CONCLUSIONS

The methodological refinements applied to establish the intestinal colonization model simplify the use of Z. morio larvae, facilitate prompt evaluation of novel decolonization approaches and reduce experiments involving vertebrate animals in accordance with the Replacement, Reduction and Refinement principles.

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.

Towards the perfect soft-boiled chicken eggs: defining cooking conditions, quality criteria, and safety assessments

In recent years, ready-to-eat soft-boiled chicken eggs, with coagulated whites and semi-solid yolks have become popular among Chinese consumers due to their convenience, tender texture, and nutritional benefits. However, the standards for these products are currently inconsistent, and quality evaluation parameters and food safety issues remain unclear. Softness ratio, representing the semi-liquid yolk proportion in a cross-section, was defined through a survey of different brands of ready-to-eat soft-boiled chicken eggs. By accounting for egg weight and cooking time, optimal softness under specific conditions was determined. A quality evaluation method was established based on the softness ratio and shelling score. Finally, the safety of soft-boiled chicken eggs was assessed by measuring yolk center temperature. The optimal softness ratio was 0.46 to 0.64. Optimal cooking times in boiling water (100°C) with a 5:1 water-to-egg ratio were 300 s for 43 to 48 g eggs, 330 seconds for 48 to 53g, 350 s for 53 to 58 g, and 370 s for 58 to 63g. After cooking, eggs were cooled for 6 min in an ice water mixture with a 3:1 water-to-egg ratio. Shelling scores (0-5) depended on the egg white surface exposed post-shelling, peaking at an air cell diameter of 21.55 ± 2.26 mm. Egg weight and shelling score had a correlation of -0.41, while egg white springiness and shelling score had a correlation of 0.86. Ensuring core yolk pasteurization standards was difficult, thus stricter management or whole egg irradiation was suggested for safety.

A Novel Application of B.EL.D™ Technology: Biosensor-Based Detection of Salmonella spp. in Food

The prevalence of foodborne diseases is continuously increasing, causing numerous hospitalizations and deaths, as well as money loss in the agri-food sector and food supply chain worldwide. The standard analyses currently used for bacteria detection have significant limitations with the most important being their long procedural time that can be crucial for foodborne outbreaks. In this study, a biosensor system able to perform robust and accurate detection of Salmonella spp. in meat products was developed. To achieve this, a portable device developed by EMBIO Diagnostics called B.EL.DTM (Bio Electric Diagnostics) and cell-based biosensor technology (BERA) were used. Results indicated that the new method could detect the pathogen within 24 h after a 3-min analysis and discriminate samples with and without Salmonella with high accuracy. Achieving an accuracy of 86.1% and a detection limit (LOD) of 1 log CFU g-1, this innovative technology enables rapid and sensitive identification of Salmonella spp. in meat and meat products, making it an excellent tool for pathogen screening.

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.

Prevalence and Antibiotic Susceptibility of Nontyphoidal Salmonella from Food-Animal Products in Bejaia, Algeria

Nontyphoidal Salmonella presents a significant threat to animal and human health as a food-borne infectious agent. This study focused on the characterization of Salmonella isolates obtained from fresh animal products consumed in Bejaia, Algeria. In total, 495 beef products, 600 chicken products, and 355 dairy products were collected from retail outlets and slaughterhouses in the region. Out of the 1450 samples collected, a Salmonella positivity rate of 3.5% (51/1450) was observed. Traditional Algerian sausages exhibited the highest prevalence of Salmonella contamination (14.1%, 36/256). Fifteen different serotypes were identified, with S. Kentucky (n = 12), S. Anatum (n = 11), and S. Bredeney (n = 9) being the most prevalent. Antimicrobial susceptibility testing showed resistance to diverse antibiotics, particularly against tetracycline, ampicillin, nalidixic acid, and sulphonamides. Whole-genome sequencing conducted on 21 isolates enabled the comparison of phylogenetic links between isolates. We notably identified clones circulating across the region in different locations and food types, suggesting contamination at the early stages of the food chain (in the herd or slaughterhouses) that disseminated to numerous butcher shops in various cities. We also identified acquired antibiotic resistance genes and point mutations in the quinolone resistance-determining region genes, contributing to the observed resistance patterns. This study describes the genomic and phylogenetic characteristics of several Salmonella clones found in diverse food samples in Algeria. It suggests potential transmission dynamics that could better understand Salmonella's contamination routes.

Food Public Opinion Prevention and Control Model Based on Sentiment Analysis

Food public opinion is characterized by its low ignition point, high diffusibility, persistence, and strong negativity, which significantly impact food safety and consumer trust. This paper introduces the Food Public Opinion Prevention and Control (FPOPC) model driven by deep learning and personalized recommendation algorithms, rigorously tested and analyzed through experimentation. Initially, based on an analysis of food public opinion development, a comprehensive FPOPC framework addressing all stages of food public opinion was established. Subsequently, a sentiment prediction model for food news based on user comments was developed using a Stacked Autoencoder (SAE), enabling predictions about consumer sentiments toward food news. The sentiment values of the food news were then quantified, and improvements were made in allocating Pearson correlation coefficient weights, leading to the design of a collaborative filtering-based personalized food news recommendation mechanism. Furthermore, an enhanced Bloom filter integrated with HDFS technology devised a rapid recommendation mechanism for food public opinion. Finally, the designed FPOPC model and its associated mechanisms were validated through experimental verification and simulation analysis. The results demonstrate that the FPOPC model can accurately predict and control the development of food public opinion and the entire food supply chain, providing regulatory agencies with effective tools for managing food public sentiment.

Comprehensive review of salmonellosis: current status of the disease and future perspectives

Salmonellosis is a significant public health concern in Saudi Arabia, with various serovars of Salmonella causing outbreaks and infections. The disease's clinical presentation includes common symptoms such as diarrhea, fever, and abdominal cramps, with potential complications in severe cases. Diagnosing salmonellosis in Saudi Arabia involves a combination of traditional laboratory methods and molecular techniques to ensure accurate identification and treatment. Preventive measures and control strategies, including vaccination campaigns, food safety protocols, and public health education, have been implemented to mitigate the spread of salmonellosis. Challenges such as antimicrobial resistance, limited healthcare resources in rural areas, and underreporting of cases persist and impact the effective management of the disease. Recommendations for improving salmonellosis prevention and management include enhancing surveillance, implementing public health education campaigns, strengthening food safety regulations, promoting antimicrobial stewardship, investing in research, improving healthcare infrastructure, and fostering collaboration and coordination between sectors. Implementing these recommendations can help Saudi Arabia effectively address the challenges posed by salmonellosis and reduce the burden of the disease on public health.

The lasso peptide produced by Bacillus licheniformis MCC 2514 demonstrates efficacy in treating in-vivoSalmonella Typhimurium infection

Salmonella, a significant pathogen transmitted through food, presents a substantial threat to public health. The issue of antibiotic misuse is causing a quest for alternative replacements. An antimicrobial peptide, predicted as lasso peptide 2514 (LP-2514), derived from the probiotic bacteria Bacillus licheniformis MCC 2514, has demonstrated effectiveness against various foodborne pathogens including Salmonella. This study aims to assess the efficacy of this peptide in vivo. Mice infected with Salmonella Typhimurium received daily oral administration of LP-2514 (30 mg/kg/day) for 2 weeks until the symptoms subsided. After the treatment, biochemical and histopathological parameters were examined. LP-2514 treated mice demonstrated reduced infection, as evidenced by a 5-fold decrease in aspartate aminotransferase concentration and a 10-fold decrease in alanine aminotransferase concentration in plasma. Nitric oxide generation was decreased by 61.23 %, C-reactive protein by 75.9 %, and numerous antioxidant enzymes were elevated to suppress the infection. Increased expression of the anti-inflammatory marker Interleukin-10 (IL-10) by 43-fold was observed in treated mice, while untreated mice displayed elevated expression of pro-inflammatory cytokines indicating the severity of infection. Hence, LP-2514 successfully alleviated the disease symptoms caused by S. Typhimurium, thus exhibiting as a potential replacement for antibiotics or food-grade preservatives.

Salmonella enterica virulence databases and bioinformatic analysis tools development

Salmonella enterica, a prominent foodborne pathogen, contributes significantly to global foodborne illnesses annually. This species exhibits significant genetic diversity, potentially impacting its infectivity, disease severity, and antimicrobial resistance. Whole genome sequencing (WGS) offers comprehensive genetic insights that can be utilized for virulence assessment. However, existing bioinformatic tools for studying Salmonella virulence have notable limitations. To address this gap, a Salmonella Virulence Database with a non-redundant, comprehensive list of putative virulence factors was constructed. Two bioinformatic analysis tools, Virulence Factor Profile Assessment and Virulence Factor Profile Comparison tools, were developed. The former provides data on similarity to the reference genes, e-value, and bite score, while the latter assesses the presence/absence of virulence genes in Salmonella isolates and facilitates comparison of virulence profiles across multiple sequences. To validate the database and associated bioinformatic tools, WGS data from 43,853 Salmonella isolates spanning 14 serovars was extracted from GenBank, and WGS data previously generated in our lab was used. Overall, the Salmonella Virulence database and our bioinformatic tools effectively facilitated virulence assessment, enhancing our understanding of virulence profiles among Salmonella isolates and serovars. The public availability of these resources will empower researchers to assess Salmonella virulence comprehensively, which could inform strategies for pathogen control and risk evaluations associated with human illnesses.

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.

Prussian-Blue-Nanozyme-Enhanced Simultaneous Immunochromatographic Control of Two Relevant Bacterial Pathogens in Milk

Salmonella typhimurium and Listeria monocytogenes are relevant foodborne bacterial pathogens which may cause serious intoxications and infectious diseases in humans. In this study, a sensitive immunochromatographic analysis (ICA) for the simultaneous detection of these two pathogens was developed. For this, test strips containing two test zones with specific monoclonal antibodies (MAb) against lipopolysaccharides of S. typhimurium and L. monocytogenes and one control zone with secondary antibodies were designed, and the double-assay conditions were optimized to ensure high analytical parameters. Prussian blue nanoparticles (PBNPs) were used as nanozyme labels and were conjugated with specific MAbs to perform a sandwich format of the ICA. Peroxidase-mimic properties of PBNPs allowed for the catalytic amplification of the colorimetric signal on test strips, enhancing the assay sensitivity. The limits of detection (LODs) of Salmonella and Listeria cells were 2 × 102 and 7 × 103 cells/mL, respectively. LODs were 100-fold less than those achieved due to the ICA based on the traditional gold label. The developed double ICA was approbated for the detection of bacteria in cow milk samples, which were processed by simple dilution by buffer before the assay. For S. typhimurium and L. monocytogenes, the recoveries from milk were 86.3 ± 9.8 and 118.2 ± 10.5% and correlated well with those estimated by the enzyme-linked immunosorbent assay as a reference method. The proposed approach was characterized by high specificity: no cross-reactivity with other bacteria strains was observed. The assay satisfies the requirements for rapid tests: a full cycle from sample acquisition to result assessment in less than half an hour. The developed ICA has a high application potential for the multiplex detection of other foodborne pathogens.

Salmonella Detection in Food Using a HEK-hTLR5 Reporter Cell-Based Sensor

The development of a rapid, sensitive, specific method for detecting foodborne pathogens is paramount for supplying safe food to enhance public health safety. Despite the significant improvement in pathogen detection methods, key issues are still associated with rapid methods, such as distinguishing living cells from dead, the pathogenic potential or health risk of the analyte at the time of consumption, the detection limit, and the sample-to-result. Mammalian cell-based assays analyze pathogens' interaction with host cells and are responsive only to live pathogens or active toxins. In this study, a human embryonic kidney (HEK293) cell line expressing Toll-Like Receptor 5 (TLR-5) and chromogenic reporter system (HEK dual hTLR5) was used for the detection of viable Salmonella in a 96-well tissue culture plate. This cell line responds to low concentrations of TLR5 agonist flagellin. Stimulation of TLR5 ligand activates nuclear factor-kB (NF-κB)-linked alkaline phosphatase (AP-1) signaling cascade inducing the production of secreted embryonic alkaline phosphatase (SEAP). With the addition of a ρ-nitrophenyl phosphate as a substrate, a colored end product representing a positive signal is quantified. The assay's specificity was validated with the top 20 Salmonella enterica serovars and 19 non-Salmonella spp. The performance of the assay was also validated with spiked food samples. The total detection time (sample-to-result), including shortened pre-enrichment (4 h) and selective enrichment (4 h) steps with artificially inoculated outbreak-implicated food samples (chicken, peanut kernel, peanut butter, black pepper, mayonnaise, and peach), was 15 h when inoculated at 1-100 CFU/25 g sample. These results show the potential of HEK-DualTM hTLR5 cell-based functional biosensors for the rapid screening of Salmonella.

Assessing antimicrobial resistance profiles of Salmonella enterica in the pork production system

Introduction. Salmonella enterica is a significant enteric pathogen affecting human and livestock health. Pork production is a common source of Salmonella contamination, with emerging multidrug resistance (MDR) posing a global health threat.Gap statement. Salmonella contamination and antimicrobial resistance (AMR) profiles in the pig production chain are underreported.Aim. To investigate the prevalence of S. enterica in the pig production chain and characterise their AMR profiles.Methodology. We collected 485 samples from pig farms, a standard pig abattoir and retail markets in Patthalung and Songkhla provinces in southern Thailand. Antimicrobial susceptibility testing was performed on these samples, and AMR profiles were determined.Results. S. enterica was detected in 68.67% of farm samples, 45.95% of abattoir samples and 50.67% of retail market samples. Analysis of 264 isolates, representing 18 serotypes, identified S. enterica serotype Rissen as the most prevalent. The predominant resistance phenotypes included ampicillin (AMP, 91.29%), tetracycline (TET, 88.26%) and streptomycin (STR, 84.47%). Over 80% of isolates showed resistance to three or more antimicrobial classes, indicating MDR. The AMP-STR-TET resistance pattern was found in nearly 70% of all MDR isolates across the production chain.Conclusions. The high prevalence of MDR is consistent with extensive antimicrobial use in the livestock sector. The presence of extensively resistant S. enterica highlights the urgent need for antimicrobial stewardship. Strengthening preventive strategies and control measures is crucial to mitigate the risk of MDR Salmonella spreading from farm to fork.

Label-free multi-line immunochromatographic sensor based on TCBPE for broad-spectrum detection Salmonella in food

BACKGROUND

Salmonella, a foodborne pathogen poses significant threats to food safety and human health. Immunochromatographic (ICTS) sensors have gained popularity in the field of food safety due to their convenience, speed, and cost-effectiveness. However, most existing ICTS sensors rely on antibody sandwich structures which are limited by their dependence on high-quality paired antibodies and restricted sensitivity. For the first time, we combined multi-line ICTS strips with fluorescent bacterial probes to develop a label-free multi-line immunochromatographic sensor capable of detecting broad-spectrum Salmonella. Salmonella was labeled with the aggregation-induced luminescence material TCBPE, resulting in its transformation into a green fluorescent probe.

RESULTS

Using this sensor, we successfully detected Salmonella typhimurium within the concentration range of 104-108 CFU/mL with a visual detection limit of 6.0 × 104 CFU/mL. Compared to single-line sensors, our multi-line sensor exhibited significantly improved fluorescence intensity resulting in enhanced detection sensitivity by 50 %. Furthermore, our developed multi-line ICTS sensor demonstrated successful detection of 18 different strains of Salmonella without any cross-reaction observed with 5 common foodborne pathogens tested. The applicability and reliability were validated using milk samples, cabbage juice samples as well and drinking water samples suggesting its potential for rapid and accurate detection of Salmonella in real-world scenarios across both the food industry and clinical settings.

SIGNIFICANCE

In this experiment, we developed a TCBPE-based multiline immunochromatographic sensor. Specifically, Salmonella was labeled with the aggregation-induced luminescence material TCBPE, resulting in its transformation into a green fluorescent probe. Through the multi-line analysis system, the detection sensitivity and accuracy of the sensor are improved. In brief, the sensor does not require complex antibody labeling and paired antibodies, and only one antibody is needed to complete the detection process.

Virulence and Antimicrobial-Resistant Gene Profiles of Salmonella spp. Isolates from Chicken Carcasses Markets in Ibague City, Colombia

Salmonella spp. is one of the leading causes of foodborne bacterial infections, with major impacts on public health and healthcare system. Salmonella is commonly transmitted via the fecal-to-oral route, and food contaminated with the bacteria (e.g., poultry products) is considered a common source of infection, being a potential risk for public health. The study aims to characterize the antimicrobial resistance- and virulence-associated genes in Salmonella isolates recovered from chicken marketed carcasses (n = 20). The presence of 14 antimicrobial and 23 virulence genes was evaluated using end-point PCR. The antimicrobial genes were detected in the following proportion among the isolates: bla TEM 100%, dfrA1 and bla CMY2 90% (n = 18), aadA1 75% (n = 15), sul1 and sul2 50% (n = 10), floR 45% (n = 9), qnrD 20% (n = 4), and aadA2 15% (n = 3). catA, sul3, qnrS, and aac(6')-Ib genes were absent in all isolates. Regarding virulence-associated genes, all Salmonella strains contain invA, fimA, avrA, msgA, sopB, and sopE. The cdtB gene was present in 95% (n = 19) of isolates, whereas spvC and spvB were present in 55% (n = 11). Other virulence genes such as spiC, lpfC, lpfA, and csgA were present in 90% (n = 18) of strains. The presence of antimicrobial and virulence genes in several Salmonella strains in chicken meat suggests the potential pathogenicity of the strains, which is relevant given the possibility of cross-contamination which represents a significant threat to public health.

A systematic review and meta-analysis of ambient temperature and precipitation with infections from five food-borne bacterial pathogens

Studies on climate variables and food pathogens are either pathogen- or region-specific, necessitating a consolidated view on the subject. This study aims to systematically review all studies on the association of ambient temperature and precipitation on the incidence of gastroenteritis and bacteraemia from Salmonella, Shigella, Campylobacter, Vibrio, and Listeria species. PubMed, Ovid MEDLINE, Scopus, and Web of Science databases were searched up to 9 March 2023. We screened 3,204 articles for eligibility and included 83 studies in the review and three in the meta-analysis. Except for one study on Campylobacter, all showed a positive association between temperature and Salmonella, Shigella, Vibrio sp., and Campylobacter gastroenteritis. Similarly, most of the included studies showed that precipitation was positively associated with these conditions. These positive associations were found regardless of the effect measure chosen. The pooled incidence rate ratio (IRR) for the three studies that included bacteraemia from Campylobacter and Salmonella sp. was 1.05 (95 per cent confidence interval (95% CI): 1.03, 1.06) for extreme temperature and 1.09 (95% CI: 0.99, 1.19) for extreme precipitation. If current climate trends continue, our findings suggest these pathogens would increase patient morbidity, the need for hospitalization, and prolonged antibiotic courses.

First Data on WGS-Based Typing and Antimicrobial Resistance of Human Salmonella Enteritidis Isolates in Greece

Salmonella enterica subsp. enterica serotype Enteritidis (S. Enteritidis) is one of the major causes of foodborne infections and is responsible for many national and multi-country foodborne outbreaks worldwide. In Greece, human salmonellosis is a mandatory notifiable disease, with laboratory surveillance being on a voluntary basis. This study aims to provide the first insights into the genetic characteristics and antimicrobial resistance profiles of 47 S. Enteritidis human isolates using whole-genome sequencing (WGS) technology. The S. Enteritidis population was mainly resistant to fluoroquinolones due to gyrA point mutations, whereas one isolate presented a multi-resistant plasmid-mediated phenotype. ST11 was the most frequent sequence type, and phylogenetic analysis through the cgMLST and SNP methods revealed considerable genetic diversity. Regarding virulence factors, 8 out of the 24 known SPIs and C63PI were detected. Due to the observed variability between countries, it is of utmost importance to record the circulating S. Enteritidis strains' structure and genomic epidemiology at the national level. WGS is a valuable tool that is revolutionizing our approach to Salmonella by providing a deeper understanding of these pathogens and their impact on human health.

Effect of acetylcholinesterase inhibition on immune cells in the murine intestinal mucosa

The gastrointestinal tract (GI) is the largest immune organ whose function is controlled by a complex network of neurons from the enteric nervous system (ENS) as well as the sympathetic and parasympathetic system. Evolving evidence indicates that cross-communication between gut-innervating neurons and immune cells regulates many essential physiological functions including protection against mucosal infections. We previously demonstrated that following paraoxon treatment, 70 % of the mice were able to survive an oral infection with S. typhimurium, a virulent strain of Salmonella enterica serovar Typhimurium. The present study aims to investigate the effect that rivastigmine, a reversible AChE inhibitor used for the treatment of neurodegenerative diseases, has on the murine immune defenses of the intestinal mucosa. Our findings show that, similar to what is observed with paraoxon, administration of rivastigmine promoted the release of secretory granules from goblet and Paneth cells, resulting in increased mucin layer. Surprisingly, however, and unlike paraoxon, rivastigmine treatment did not affect overall mortality of infected mice. In order to investigate the mechanistic basis for the differential effects observed between paraoxon and rivastigmine, we used multi-color flowcytometric analysis to characterize the immune cell landscape in the intraepithelial (IE) and lamina propria (LP) compartments of intestinal mucosa. Our data indicate that treatment with paraoxon, but not rivastigmine, led to an increase of resident CD3+CD8+ T lymphocytes in the ileal mucosa (epithelium and lamina propria) and CD11b- CD11c+ dendritic cells in the LP. Our findings indicate the requirement for persistent cholinergic pathway engagement to effect a change in the cellular landscape of the mucosal tissue that is necessary for protection against lethal bacterial infections. Moreover, optimal protection requires a collaboration between innate and adaptive mucosal immune responses in the intestine.

In Vivo and in Vitro Mitigation of Salmonella Typhimurium Isolates by Fortunella Japonica Fruit Extract

The vast dissemination of resistance to different antibiotics among bacterial pathogens, especially foodborne pathogens, has drawn major research attention. Thus, many attempts have been made to reveal novel alternatives to the current antibiotics. Due to their variable pharmacologically active phytochemicals, plants represent a good solution for this issue. This study investigated the antibacterial potential of Kumquat or Fortunella japonica methanol extract (FJME) against Salmonella typhimurium clinical isolates. Gas chromatography coupled with mass spectrometry (GC/MS) characterized 39 compounds in FJME. Palmitic acid (15.386%) and cis-vaccenic acid (15.012%) are the major active constituents detected by GC/MS. Remarkably, FJME had minimum inhibitory concentrations from 128 to 512 µg/mL in vitro. In addition, a systemic infection model revealed the in vivo antibacterial action of FJME. The antibacterial therapeutic activity of FJME was noticed by improving the histological features of the liver and spleen. Moreover, there was a perceptible lessening (p < 0.05) of the levels of the oxidative stress markers (nitric oxide and malondialdehyde) using ELISA. In addition, the gene expression of the proinflammatory cytokine (interleukin 6) was downregulated. On the other hand, there was an upregulation of the anti-inflammatory cytokine (interleukin 10). Accordingly, future clinical investigations should be done to reveal the potential antibacterial action of FJME on other food pathogens.

Serovar and sequence type distribution and phenotypic and genotypic antimicrobial resistance of Salmonella originating from pet animals in Chongqing, China

A total of 334 Salmonella isolates were recovered from 6,223 pet rectal samples collected at 50 pet clinics, 42 pet shops, 7 residential areas, and 4 plazas. Forty serovars were identified that included all strains except for one isolate that did not cluster via self-agglutination, with Salmonella Typhimurium monophasic variant, Salmonella Kentucky, Salmonella Enteritidis, Salmonella Pomona, and Salmonella Give being the predominant serovars. Fifty-one sequence types were identified among the isolates, and ST198, ST11, ST19, ST451, ST34, and ST155 were the most common. The top four dominant antimicrobials to which isolates were resistant were sulfisoxazole, ampicillin, doxycycline, and tetracycline, and 217 isolates exhibited multidrug resistance. The prevalence of β-lactamase genes in Salmonella isolates was 59.6%, and among these isolates, 185 harbored blaTEM, followed by blaCTX-M (66) and blaOXA (10). Moreover, six PMQR genes, namely, including qnrA (4.8%), qnrB (4.2%), qnrD (0.9%), qnrS (18.9%), aac(6')-Ib-cr (16.5%), and oqxB (1.5%), were detected. QRDR mutations (76.6%) were very common in Salmonella isolates, with the most frequent mutation in parC (T57S) (47.3%). Furthermore, we detected six tetracycline resistance genes in 176 isolates, namely, tet(A) (39.5%), tet(B) (8.1%), tet(M) (7.7%), tet(D) (5.4%), tet(J) (3.3%), and tet(C) (1.8%), and three sulfonamide resistance genes in 303 isolates, namely, sul1 (84.4%), sul2 (31.1%), and sul3 (4.2%). Finally, we found 86 isolates simultaneously harboring four types of resistance genes that cotransferred 2-7 resistance genes to recipient bacteria. The frequent occurrence of antimicrobial resistance, particularly in dogs and cats, suggests that antibiotic misuse may be driving multidrug-resistant Salmonella among pets.IMPORTANCEPet-associated human salmonellosis has been reported for many years, and antimicrobial resistance in pet-associated Salmonella has become a serious public health problem and has attracted increasing attention. There are no reports of Salmonella from pets and their antimicrobial resistance in Chongqing, China. In this study, we investigated the prevalence, serovar diversity, sequence types, and antimicrobial resistance of Salmonella strains isolated from pet fecal samples in Chongqing. In addition, β-lactamase, QRDR, PMQR, tetracycline and sulfonamide resistance genes, and mutations in QRDRs in Salmonella isolates were examined. Our findings demonstrated the diversity of serovars and sequence types of Salmonella isolates. The isolates were widely resistant to antimicrobials, notably with a high proportion of multidrug-resistant strains, which highlights the potential direct or indirect transmission of multidrug-resistant Salmonella from pets to humans. Furthermore, resistance genes were widely prevalent in the isolates, and most of the resistance genes were spread horizontally between strains.

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.

A review and meta-analysis of non-typhoidal Salmonella in Vietnam: Challenges to the control and antimicrobial resistance traits of a neglected zoonotic pathogen

Non-typhoidal Salmonella (NTS) is a food-borne zoonotic pathogen with important implications for human health. Despite its importance, the burden of NTS infections in Vietnam is unknown. We conducted a systematic review and a meta-analysis to describe the prevalence and phenotypic antimicrobial resistance (AMR) for NTS over time in Vietnam. Following PRISMA guidelines, we identified 72 studies from PubMed and Google Scholar containing data relevant to 'Salmonella', 'Salmonellosis', and 'Vietnam', or 'Viet Nam'. Of those, forty-two papers reporting prevalence of NTS, and twenty-six including data on phenotypic resistance were selected for meta-analysis. The prevalence of NTS ranged from 2% to 5% in humans and from 30% to 41% in samples from animals and the farm/slaughterhouse environment. Between 2000 and 2020 we observed a 27.3% (p = 0.044) increase in absolute terms in prevalence among individuals with enteric diseases and a 12.0% (p = 0.047) increase in aquaculture/seafood samples. The most commonly serovars identified across studies included S. Weltevreden (12.0%), followed by S. Typhimurium (10.1%), S. Derby (6.4%), S. London (5.8%), S. Anatum (4.4%), S. Rissen (3.9%), S. Enteritidis (3.7%), S. Albany (3.3%) and S. 4,[5],12:i:- (3.0%). Over the same period, there was an increasing trend in the pooled AMR prevalence for quinolones (15.6% relative increase), 3rd-, 4th-, and 5th-generation cephalosporins (23.7%), penicillins (16.1%), tetracyclines (12.9%), sulfonamides (8.8%), amphenicol (17.8%), and multidrug resistance (11.4%) (all p ≤ 0.014). A broad range of AMR genes (ARGs) were detected in both human and animal populations. The observed prevalence and AMR trends in Vietnam underscore the need of adopting a One Health strategy encompassing surveillance systems, research initiatives, and awareness campaigns to effectively address the challenges posed by NTS.

A Systemic Review on Fitness and Survival of Salmonella in Dynamic Environment and Conceivable Ways of Its Mitigation

Gastroenteritis caused by non-typhoidal Salmonella still prevails resulting in several recent outbreaks affecting many people worldwide. The presence of invasive non-typhoidal Salmonella is exemplified by several characteristic symptoms and their severity relies on prominent risk factors. The persistence of this pathogen can be attributed to its broad host range, complex pathogenicity and virulence and adeptness in survival under challenging conditions inside the host. Moreover, a peculiar aid of the ever-changing climatic conditions grants this organism with remarkable potential to survive within the environment. Abusive use of antibiotics for the treatment of gastroenteritis has led to the emergence of multiple drug resistance, making the infections difficult to treat. This review emphasizes the importance of early detection of Salmonella, along with strategies for accomplishing it, as well as exploring alternative treatment approaches. The exceptional characteristics exhibited by Salmonella, like strategies of infection, persistence, and survival parallelly with multiple drug resistance, make this pathogen a prominent concern to human health.

Prevalence and antimicrobial susceptibility of Salmonella enteritidis and Salmonella typhimurium isolated from hen eggs and quail eggs in Karaj, Iran

BACKGROUND AND AIM

Different Salmonella serotypes are considered one of the most important food pathogens in the world. Poultry meat and eggs are the primary carriers of Salmonella in human populations. This study aimed to estimate the Salmonella enteritidis and Salmonella typhimurium contamination rates of retail hen and quail eggs in Karaj, Iran. Moreover, the antimicrobial resistance patterns of the strains were evaluated, and the efficiency of the standard culture method and multiplex polymerase chain reaction (m-PCR) were compared.

MATERIALS AND METHODS

In this descriptive cross-sectional study over 1 year (Jan-Dec 2022), 150 commercial and 150 backyard hen eggs and 300 commercial quail eggs, without cracks and fractures, were collected randomly from best selling groceries in Karaj city. All samples were examined for Salmonella contamination independently by standard culture and m-PCR approaches. A standard disc diffusion method was employed to assess the antimicrobial susceptibility of the strains against 18 antimicrobial agents.

RESULTS

Out of 300 examined eggs, 2 S. enteritidis strains were isolated from the shell of backyard hen eggs. The same serotype was also detected in the contents of one of these two eggs. One S. typhimurium was isolated from the shell of a commercial hen egg. Overall, the Salmonella contamination of the shell and contents was 1% and 0.3%, respectively. Salmonella was not isolated from the eggshells or the contents of the quail eggs. There was complete agreement between the results of m-PCR and the standard culture methods. Among the 18 tested antibiotics, the highest resistance was recorded for colistin (100%), followed by nalidixic acid (75%).

CONCLUSION

As most Salmonella spp. are associated with human food poisoning, continuous surveillance is required to effectively reduce the risk posed by contaminated poultry eggs. Furthermore, mandatory monitoring of antimicrobial use on Iranian poultry farms is recommended.

A bacteriophage cocktail can efficiently reduce five important Salmonella serotypes both on chicken skin and stainless steel

Salmonella is one of the most important zoonotic pathogens and is mostly transmitted through food of animal origin. Application of bacteriophages is a promising tool to biocontrol Salmonella on both food and food contact surfaces. In this study, we evaluated the effectiveness of a six-phage cocktail for the reduction of Salmonella Enteritidis and a mixture of five major Salmonella serotypes (S. Enteritidis, Salmonella Typhimurium, Salmonella Infantis, Salmonella Paratyphi B, and Salmonella Indiana) on chicken skin and stainless steel. A phage cocktail with a final concentration of 107 PFU/cm2 was sprayed on these surfaces. After adding the phage cocktail, the samples were incubated at RT (~23°C) for different periods of time. The phage cocktail caused a significant reduction of S. Enteritidis and the mixed culture on chicken skin 30 min after phage addition, with 1.8 log10 and 1 log10 units, respectively. Reduction rates (1.2-1.7 log10 units) on stainless steel after 30 min were similar. Four hours after addition, the phage cocktail caused a significant reduction on both surfaces up to 3 log10 units on chicken skin and 2.4 log10 units on stainless steel. In a further experiment, bacteria added to stainless steel were not allowed to dry to simulate a fresh bacterial contamination. In this case, the bacterial count of S. Enteritidis was reduced below the detection limit after 2 h. The results demonstrate that this phage cocktail has potential to be used in post-harvest applications to control Salmonella contaminations.

Epidemiology of Salmonella enterica subspecies enterica serotypes, isolated from imported, farmed and feral poultry in the Cayman Islands

Non-typhoidal Salmonellae (NTS) are common foodborne pathogens throughout the world causing acute gastroenteritis. Compared to North America and Europe, there is little information on NTS in the Caribbean. Here we investigated the prevalence and characteristics of NTS present in the local poultry of the Cayman Islands to determine the public health risk. In total, we collected 156 samples. These were made up of boot swabs of 31 broiler farms and 31 layer farms (62 samples), paper bedding from 45 imported chick boxes, and 49 pooled cecum samples from feral chickens, each sample representing 10 individual chickens. Salmonella was isolated using the ISO 6579 protocol and isolates were characterized using Whole Genome Sequencing (WGS) analysis. Eighteen Salmonella isolates were obtained and comprised six S. enterica subspecies enterica serotypes and one subspecies houtenae serotype. Serotypes were: S. Kentucky (n = 9), S. Saintpaul (n = 5), S. Javiana (n = 1), S. Senftenberg (n = 1), S. Poona (n = 1) and S. Agona (n = 1). S. Kentucky strains were all ST152 and clonally related to poultry strains from the United states. S. Saintpaul ST50 strains showed clonality to North American strains. Over half of the strains (n = 11) contained resistance genes to at least two antibiotic groups and five strains were MDR, mainly those from imported day-old chicks. The blaCMY-2 gene was found in S. Kentucky from day-old chicks. Strains from feral poultry had no acquired AMR genes. While serotypes from feral poultry have been identified in human infections, they pose minimal risk due to their low virulence.