Salmonella antimicrobials inherited and the non-inherited resistance: mechanisms and alternative therapeutic strategies

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.

Salmonella enterica serovar Braenderup shows clade-specific source associations and a high proportion of molecular epidemiological clustering

Salmonella enterica serovar Braenderup (S. enterica ser. Braenderup) is an important clinical serovar in the United States. This serovar was reported by the CDC in 2017 as the fifth most common Salmonella enterica serovar associated with outbreaks in the United States, which have been linked to both fresh produce and food animal products. The goals of this study were to compare the relatedness of human clinical isolates from southeastern USA (Tennessee (n = 106), Kentucky (n = 48), Virginia (n = 252), South Carolina (n = 109), Georgia (n = 159), Alabama (n = 8), Arkansas (n = 26), and Louisiana (n = 91)) and global clinical (n = 5,153) and nonclinical (n = 1,053) isolates obtained from the NCBI. Additionally, we also examined the population structure of S. enterica ser. Braenderup strains (n = 3,131) on EnteroBase and found that all the strains of this serovar are associated with a single cgMLST eBurst group (ceBG 185), confirming that this serovar is monophyletic. We divided the S. enterica ser. Braenderup population into two clades (Clade I and Clade II) and one clade group (Clade Group III). The composition of distinct environmental isolates in the clades differed: Clade I was significantly associated with produce (90.7%; P < 0.0001) and water, soil, and sediment (76.9%; P < 0.0001), and Clade II was significantly associated with poultry environments (62.8%; P < 0.0001). The clade-specific gene associations (e.g., Clade I-associated competence proteins and cytochrome_c_asm protein and Clade II-associated heme-exporter protein and dimethyl sulfoxide [DMSO] reductase-encoding genes) provide potential insights into possible mechanisms driving environmental adaptation and host-pathogen interaction. Phylogenetic analyses identified 218 molecular epidemiological clusters in the current study, which represented a greater proportion of potentially outbreak-related isolates than previously estimated.

IMPORTANCE

This study provides insights into the genomic diversity of S. enterica ser. Braenderup by revealing distinct clade-specific source attribution patterns and showing that a greater proportion of isolates were associated with epidemiological clusters based on the genomic relatedness than previously estimated. Specifically, we analyzed the diversity of human clinical isolates from southeastern USA and compared them with the global clinical and nonclinical isolates. Our analysis showed different clades of S. enterica ser. Braenderup linked to different environments, providing insights on the potential source of human sporadic infection and outbreaks. These findings can enhance public health surveillance and response strategies targeting S. enterica serovar Braenderup by expanding our understanding of potential transmission pathways and the genomic diversity of clinical and environmental isolates.

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.

Isolation, characterization and liposome-loaded encapsulation of a novel virulent Salmonella phage vB-SeS-01

Introduction

Salmonella is a common foodborne pathogenic bacterium, displaying facultative intracellular parasitic behavior, which can help the escape against antibiotics treatment. Bacteriophages have the potential to control both intracellular and facultative intracellular bacteria and can be developed as antibiotic alternatives.

Methods

This study isolated and characterized vB-SeS-01, a novel Guernseyvirinae phage preying on Salmonella enterica, whose genome is closely related to those of phages SHWT1 and vB-SenS-EnJE1. Furthermore, nine phage-carrying liposome formulations were developed by film hydration method and via liposome extruder.

Results and Discussion

Phage vB-SeS-01 displays strong lysis ability against 9 out of 24 tested S. enterica strains (including the pathogenic "Sendai" and "Enteritidis" serovars), high replicability with a burst size of 111 ± 15 PFU/ cell and a titre up to 2.1 × 1011 PFU/mL, and broad pH (4.0 ~ 13.0) and temperature (4 ~ 80°C) stabilities. Among the nine vB-SeS-01 liposome-carrying formulations, the one encapsulated with PC:Chol:T80:SA = 9:1:2:0.5 without sonication displayed the optimal features. This formulation carried up to 1011 PFU/mL, with an encapsulation rate of 80%, an average size of 172.8 nm, and a polydispersity index (PDI) of 0.087. It remained stable at 4°C and 23°C for at least 21 days and at 37°C for 7 days. Both vB-SeS-01 and vB-SeS-01-loaded liposomes displayed intracellular antimicrobial effects and could reduce the transcription level of some tested intracellular inflammatory factors caused by the infected S. enterica sv. Sendai 16,226 and Enteritidis 50041CMCC.

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.

When the solution becomes the problem: a review on antimicrobial resistance in dairy cattle

Antibiotics' action, once a 'magic bullet', is now hindered by widespread microbial resistance, creating a global antimicrobial resistance (AMR) crisis. A primary driver of AMR is the selective pressure from antimicrobial use. Between 2000 and 2015, antibiotic consumption increased by 65%, reaching 34.8 billion tons, 73% of which was used in animals. In the dairy cattle sector, antibiotics are crucial for treating diseases like mastitis, posing risks to humans, animals and potentially leading to environmental contamination. To address AMR, strategies like selective dry cow therapy, alternative treatments (nanoparticles, phages) and waste management innovations are emerging. However, most solutions are in development, emphasizing the urgent need for further research to tackle AMR in dairy farms.

Cananga oil inhibits Salmonella infection by mediating the homeostasis of purine metabolism and the TCA cycle

ETHNOPHARMACOLOGY RELEVANCE

Cananga oil (CO) is derived from the flowers of the traditional medicinal plant, the ylang-ylang tree. As a traditional antidepressant, CO is commonly utilized in the treatment of various mental disorders including depression, anxiety, and autism. It is also recognized as an efficient antibacterial insecticide, and has been traditionally utilized to combat malaria and acute inflammatory responses resulting from bacterial infections both in vitro and in vivo.

AIM OF THE STUDY

The objective of this study is to comprehensively investigate the anti-Salmonella activity and mechanism of CO both in vitro and in vivo, with the expectation of providing feasible strategies for exploring new antimicrobial strategies and developing novel drugs.

METHODS

The in vitro antibacterial activity of CO was comprehensively analyzed by measuring MIC, MBC, growth curve, time-killing curve, surface motility, biofilm, and Live/dead bacterial staining. The analysis of the chemistry and active ingredients of CO was conducted using GC-MS. To examine the influence of CO on the membrane homeostasis of Salmonella, we conducted utilizing diverse techniques, including ANS, PI, NPN, ONPG, BCECF-AM, DiSC3(5), and scanning electron microscopy (SEM) analysis. In addition, the antibacterial mechanism of CO was analyzed and validated through metabolomics analysis. Finally, a mouse infection model of Salmonella typhimurium was established to evaluate the toxic side effects and therapeutic effects of CO.

RESULTS

The antibacterial effect of CO is the result of the combined action of the main chemical components within its six (palmitic acid, α-linolenic acid, stearic acid, benzyl benzoate, benzyl acetate, and myristic acid). Furthermore, CO disrupts the balance of purine metabolism and the tricarboxylic acid cycle (TCA cycle) in Salmonella, interfering with redox processes. This leads to energy metabolic disorders and oxidative stress damage within the bacteria, resulting in bacterial shock, enhanced membrane damage, and ultimately bacterial death. It is worth emphasizing that CO exerts an effective protective influence on Salmonella infection in vivo within a non-toxic concentration range.

CONCLUSION

The outcomes indicate that CO displays remarkable anti-Salmonella activity both in vitro and in vivo. It triggers bacterial death by disrupting the balance of purine metabolism and the TCA cycle, interfering with the redox process, making it a promising anti-Salmonella medication.

Deciphering Microbiome, Transcriptome, and Metabolic Interactions in the Presence of Probiotic Lactobacillus acidophilus against Salmonella Typhimurium in a Murine Model

Salmonella enterica serovar Typhimurium (S. Typhimurium), a foodborne pathogen that poses significant public health risks to humans and animals, presents a formidable challenge due to its antibiotic resistance. This study explores the potential of Lactobacillus acidophilus (L. acidophilus 1.3251) probiotics as an alternative strategy to combat antibiotic resistance associated with S. Typhimurium infection. In this investigation, twenty-four BALB/c mice were assigned to four groups: a non-infected, non-treated group (CNG); an infected, non-treated group (CPG); a group fed with L. acidophilus but not infected (LAG); and a group fed with L. acidophilus and challenged with Salmonella (LAST). The results revealed a reduction in Salmonella levels in the feces of mice, along with restored weight and improved overall health in the LAST compared to the CPG. The feeding of L. acidophilus was found to downregulate pro-inflammatory cytokine mRNA induced by Salmonella while upregulating anti-inflammatory cytokines. Additionally, it influenced the expression of mRNA transcript, encoding tight junction protein, oxidative stress-induced enzymes, and apoptosis-related mRNA expression. Furthermore, the LEfSe analysis demonstrated a significant shift in the abundance of critical commensal genera in the LAST, essential for maintaining gut homeostasis, metabolic reactions, anti-inflammatory responses, and butyrate production. Transcriptomic analysis revealed 2173 upregulated and 506 downregulated differentially expressed genes (DEGs) in the LAST vs. the CPG. Functional analysis of these DEGs highlighted their involvement in immunity, metabolism, and cellular development. Kyoto Encyclopedia of Genes and Genome (KEGG) pathway analysis indicated their role in tumor necrosis factor (TNF), mitogen-activated protein kinase (MAPK), chemokine, Forkhead box O (FOXO), and transforming growth factor (TGF-β) signaling pathway. Moreover, the fecal metabolomic analysis identified 929 differential metabolites, with enrichment observed in valine, leucine, isoleucine, taurine, glycine, and other metabolites. These findings suggest that supplementation with L. acidophilus promotes the growth of beneficial commensal genera while mitigating Salmonella-induced intestinal disruption by modulating immunity, gut homeostasis, gut barrier integrity, and metabolism.