Prevalence and Antibiotic Resistance of Salmonella Enteritidis and Salmonella Typhimurium in Ground Beef and Meatball Samples in Samsun, Turkey

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.

Antimicrobial-resistant foodborne pathogens in the Middle East: a systematic review

Foodborne pathogens are known as significant public health hazards worldwide, particularly in the Middle East region. Antimicrobial resistance (AMR) among foodborne pathogens becomes one of the top challenges for the environment, public health, and food safety sectors. However, less is known about antimicrobial-resistant foodborne pathogens in the Middle East region. Possibly because of the lack of surveillance, documentation, and reporting. This review focuses on the current status of antimicrobial resistance profiling among foodborne pathogens in the Middle East. Therefore, PubMed and other relevant databases were searched following PRISMA guidelines. Subject heading and texts were searched for "antimicrobial resistances," "foodborne," and "Middle East" to identify observational studies on AMR foodborne pathogens published during the last 10 years (2011 to 2020). Article retrieval and screening were done using a structured search string and strict inclusion/exclusion criteria. Median and interquartile ranges of percent resistance were calculated for each antibiotic-bacterium combination. A total of 249 articles were included in the final analysis from ten countries, where only five countries had more than 85% of the included articles. The most commonly reported pathogens were Escherichia coli, Salmonella spp. Staphylococcus aureus, and Listeria spp. An apparent rise in drug resistance among foodborne pathogens was recorded particularly against amoxicillin-clavulanic acid, ampicillin, nalidixic acid, streptomycin, and tetracycline that are commonly prescribed in most countries in the Middle East. Besides, there is a lack of standardization and quality control for microbiological identification and susceptibility testing methods in many of the Middle East countries.

Antibacterial efficacy of in-house designed cell-penetrating peptide against multi-drug resistant strains of Salmonella Enteritidis and Salmonella Typhimurium

The in vitro antibacterial efficacy of an in-house designed cell-penetrating peptide (CPP) variant of Cecropin A (1-7)-Melittin (CAMA) (CAMA-CPP) against the characterized multi-drug resistant (MDR) field strains of Salmonella Enteritidis and Salmonella Typhimurium were evaluated and compared with two identified CPPs namely, P7 and APP, keeping CAMA as control. Initially, the minimum inhibitory concentration (MIC) (μg ml^-1 ) of in-house designed CAMA-CPP, APP and CAMA was determined to be 3.91, whereas that of P7 was 7.81; however, the minimum bactericidal concentration (MBC) of all the peptides were twice the MIC. CAMA-CPP and CAMA were found to be stable under different conditions (high-end temperatures, proteinase-K, cationic salts, pH and serum) when compared to the other CPPs. Moreover, CAMA-CPP exhibited negligible cytotoxicity in HEp-2 and RAW 264.7 cell lines as well as haemolysis in the sheep and human erythrocytes with no adverse effects against the commensal gut lactobacilli. In vitro time-kill assay revealed that the MBC levels of CAMA-CPP and APP could eliminate the intracellular MDR-Salmonella infections from mammalian cell lines; however, CAMA and P7 peptides were ineffective. CAMA-CPP appears to be a promising antimicrobial candidate and opens up further avenues for its in vivo clinical translation.

Class 1 integron-borne cassettes harboring blaCARB-2 gene in multidrug-resistant and virulent Salmonella Typhimurium ST19 strains recovered from clinical human stool samples, United States

International lineages, such as Salmonella Typhimurium sequence type (ST) 19, are most often associated with foodborne diseases and deaths in humans. In this study, we compared the whole-genome sequences of five S. Typhimurium strains belonging to ST19 recovered from clinical human stool samples in North Carolina, United States. Overall, S. Typhimurium strains displayed multidrug-resistant profile, being resistance to critically and highly important antimicrobials including ampicillin, ticarcillin/clavulanic acid, streptomycin and sulfisoxazole, chloramphenicol, tetracycline, respectively. Interestingly, all S. Typhimurium strains carried class 1 integron (intl1) and we were able to describe two genomic regions surrounding bla_CARB-2 gene, size 4,062 bp and 4,422 bp for S. Typhimurium strains (HS5344, HS5437, and HS5478) and (HS5302 and HS5368), respectively. Genomic analysis for antimicrobial resistome confirmed the presence of clinically important genes, including bla_CARB-2, aac(6’)-Iaa, aadA2b, sul1, tetG, floR, and biocide resistance genes (qacEΔ1). S. Typhimurium strains harbored IncFIB plasmid containing spvRABCD operon, as well as rck and pef virulence genes, which constitute an important apparatus for spreading the virulence plasmid. In addition, we identified several virulence genes, chromosomally located, while the phylogenetic analysis revealed clonal relatedness among these strains with S. enterica isolated from human and non-human sources obtained in European and Asian countries. Our results provide new insights into this unusual class 1 integron in virulent S. Typhimurium strains that harbors a pool of genes acting as potential hotspots for horizontal gene transfer providing readily adaptation to new surrounds, as well as being crucially required for virulence in vivo. Therefore, continuous genomic surveillance is an important tool for safeguarding human health.

Antimicrobial efficacy of Cecropin A (1-7)- Melittin and Lactoferricin (17-30) against multi-drug resistant Salmonella Enteritidis

The present study evaluated intracellular antibacterial efficacy of two short-chain cationic antimicrobial peptides (AMPs) namely, Cecropin A (1-7)-Melittin and lactoferricin (17-30) against three field strains of multi-drug resistant Salmonella Enteritidis. Initially, antimicrobial ability of both the AMPs was evaluated for their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against multi-drug resistant S. Enteritidis strains. Besides, the AMPs were evaluated for its in vitro stability (high-end temperatures, proteases, physiological concentrations of cationic salts and pH) and safety (haemolytic assay in sheep erythrocytes; cytotoxicity assay in murine macrophage RAW 264.7 cell line and human epithelioma HEp-2 cell line and beneficial gut lactobacilli). Later, a time-kill assay was performed to assess the intracellular antibacterial activity of Cecropin A (1-7)-Melittin and lactoferricin (17-30) against multi-drug resistant S. Enteritidis in RAW 264.7 and HEp-2 cells. The observed MBC values of Cecropin A (1-7)-Melittin and lactoferricin (17-30) against multi-drug resistant S. Enteritidis (128 μM; 256 μM) were generally twice or four-fold greater than the MIC values (64 μM). Further, both the AMPs were found variably stable after exposure at high-end temperatures (70 °C and 90 °C), protease treatment (trypsin, proteinase K, lysozyme), higher concentration of physiological salts (150 mM NaCl and 2 mM MgCl₂) and hydrogen ion concentrations (pH 4.0 to 8.0). Both the AMPs were found non-haemolytic on sheep erythrocytes, revealed minimal cytotoxicity in RAW 264.7 and HEp-2 cells, and was tested safe against beneficial gut lactobacilli (L. acidophilus and L. rhamnosus). Intracellular bacteriostatic effect with both cationic AMPs against multi-drug resistant S. Enteritidis was evident in RAW 264.7 cells; however, in both the cell lines, the significant bactericidal effect was not observed (P > 0.05) with both cationic AMPs understudy against multi-drug resistant S. Enteritidis. Based on the results of the present study, both the cationic AMPs understudy may not be useful for the intracellular elimination of multi-drug resistant S. Enteritidis; hence, further studies such as conjugation of these AMPs with either cell-penetrating peptides (CPP) and/or nanoparticles (NPs) are warranted.

Antimicrobial Resistance in Nontyphoidal Salmonella Isolates from Human and Swine Sources in Brazil: A Systematic Review of the Past Three Decades

Salmonella is the leading cause of foodborne illnesses worldwide. The widespread use of antimicrobials as prophylactic, therapeutic, and growth promoters in both livestock and human medicine has resulted in selective pressure regarding antimicrobial-resistant (AMR) bacteria. This systematic review summarizes phenotypic antimicrobial resistance profiles in Salmonella isolates from human and swine sources between 1990 and 2018 in Brazil. The 20 studies that matched the eligibility criteria-isolates from pigs and humans from Brazil, between 1990 and 2016, containing information on the number of Salmonella isolates, and applying the disk diffusion susceptibility method-were included. During the assessed period, Salmonella strains isolated from swine sources displayed the highest resistance rates for tetracycline (20.3%) and sulfonamides (17.4%). In contrast, human isolates displayed the highest resistance rates against ampicillin (19.8%) and tetracycline (17%). Salmonella Typhimurium was the most frequent AMR isolate from both swine and human sources, corresponding to 67% of all isolates. From 2001 to 2005, tetracycline and ampicillin were the top antimicrobial resistance compounds, and the most frequently detected in swine and human sources, respectively. A total of 63 and 58 multiple drug resistance profiles were identified in swine and human isolates, respectively. Antimicrobial resistance has decreased throughout the 1990-2016 period, except for gentamicin and nalidixic acid in swine and human isolates, respectively. The results indicate that Salmonella isolated from human and swine display resistance against clinically important antimicrobials, indicating that swine are possibly one of the main vectors for spreading human salmonellosis in Brazil.