A review of Salmonella enterica with particular focus on the pathogenicity and virulence factors, host specificity and antimicrobial resistance including multidrug resistance

Isolation and characterization of duck sewage source Salmonella phage P6 and antibacterial activity for recombinant endolysin LysP6

Salmonella is a globally prevalent foodborne pathogen, and adverse events caused by S. Enteritidis and S. Typhimurium are extremely common. With the emergence of drug resistance, there is an urgent need for efficient and specific lytic bacteriophages as alternative to antibiotics in clinical practice. In this study, phage P6 was isolated and screened from effluent and fecal samples from duck farm environments to specifically lyse the duck sources S. Typhimurium and S. Enteritidis. Phage P6 belongs to the genus Lederbergvirus, unclassified Lederbergvirus species. The phage P6 genome did not contained non-coding RNA, virulence genes and drug resistance genes, indicating that phage P6 was biologically safe for clinical applications. Phage P6 lysed 77.78% (28/36) of multidrug-resistant Salmonella and reduced biofilms formed by S. Enteritidis CVCC 3377, 4, and 24, and S. Typhimurium 44 by 44% to 75% within 3 h, and decreased Salmonella in duckling feces by up to 1.64 orders of magnitude. Prokaryotic expression of endolysin LysP6 lysed the chloroform-treated bacterial outer membrane from different serotypes of duck-derived Salmonella and E. coli standard strain ATCC 25922. The host range was expanded compared to phage P6, and the growth of Salmonella was effectively inhibited by LysP6 in conjunction with the membrane permeabilizer EDTA within 24 h. Therefore, phage P6 and phage-derived endolysins LysP6 are suitable for application as potent biocontrol agents to improve poultry health and food safety.

Epidemiological and molecular investigations of Salmonella isolated from duck farms in southwest and around area of Shandong, China

Salmonella is a zoonotic pathogen posing a serious risk to the farming industry and public health due to food animals serving as reservoirs for future contamination and spread of Salmonella. The present study is designed to monitor the contamination status of Salmonella in duck farms and the main control points during breeding. 160 strains of duck-derived Salmonella were isolated from the 736 samples (cloacal swabs, feces, water, feed, soil, air and dead duck embryos) collected in southwest Shandong Province and the province's surrounding area. The percentage of Salmonella-positive samples collected was 21.74 % (160/736), and the greatest prevalence from duck embryo samples (40.00 %, 36/90). These Salmonella were classified into 23 serotypes depending on their O and H antigens, in which S. Typhimurium (30.15 %), S. Kottbus (13.97 %) and S. Enteritidis (10.29 %) were the prevailing serotypes. Subsequently, the molecular subtyping was done. Clustered regularly interspaced short palindromic repeats (CRISPR) analysis showed that 41 strains of S. Typhimurium and 14 strains of S. Enteritidis were classified into 13 and 3 genotypes, respectively. 19 S. Kottbus isolates from different sources featured ST1546, ST198, ST321, and ST1690 by multilocus sequence typing (MLST) analysis, among which ST1546 belongs to S. Kottbus was a new ST. The minimum spanning tree analysis based on the two CRISPR loci and seven MLST loci from all S. Typhimurium, S. Enteritidis and S. Kottbus isolates revealed that duck embryos, feed and water were key control points to the spread of Salmonella along the breeding chain. Meanwhile, the emergence of S. Kottbus in duck flocks was considered a potential public health hazard.

In vitro and in vivo efficacy of zinc oxide green nanoparticles against multidrug-resistant Salmonella Typhi

Antibiotic resistance is an increasing threat, requiring novel therapeutic solutions. Metal nanoparticles e.g., zinc oxide nanoparticles (ZnO NPs) exhibited the potential against many bacterial pathogens. Strains of Salmonella enterica serovar Typhi resistant to ceftriaxone were reported first from Pakistan in 2016. Since then, S. Typhi is a pathogen of concern globally owing to its rapidly emerging resistance potential against many last resort antibiotics. In the present study, in vitro and in vivo antimicrobial activity of ZnO NPs against multidrug resistant (MDR) and extensively drug resistant (XDR) Salmonella Typhi strains from Pakistan was evaluated. Zinc oxide green nanoparticles (ZnO GNPs), synthesized from Aloe vera, were characterized by SEM, XRD, UV-vis and Raman spectroscopy. In vitro antibacterial activity of two different concentrations of ZnO GNPs (7 and 15%) was checked using agar well diffusion method. Further, broth microdilution and time kill assays were performed using the ZnO GNPs. In vivo assays were conducted in BALB/c mice sepsis models. In all the three methods, agar well diffusion assay broth microdilution and time kill assay, different zinc oxide dihydrate precursor concentrations had shown the antibacterial activity. The minimum inhibitory concentration (MIC) of ZnO GNPs nanoparticles against MDR and XDR S. Typhi strains was found as 16 to 64 µg/ml. In vivo experiment has shown a significant decrease in CFU/ml in the mice treated with ZnO GNPs as compared to the control group. Our findings have revealed that ZnO GNPs have significant antibacterial activity against MDR and XDR S. Typhi, both in vitro and in vivo.

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.

Salmonella pathogenesis-based In-silico design and immunoinformatic analysis of multi-epitope vaccine constructs in broiler veterinary medicine

Salmonellosis, a zoonotic gastrointestinal disease, presents a significant global health burden with a high incidence rate. Transmission primarily occurs through the consumption of contaminated poultry products, although water and contact with asymptomatic animals are also vectors. The disease's pervasiveness has prompted international health organizations to advocate for robust prevention and control strategies. This study focuses on the in-silico design of a multi-epitope vaccine targeting Salmonella enterica serovar Typhimurium's fimH protein, a fimbriae component crucial for bacterial adhesion and pathogenicity. The vaccine construct was developed by identifying and synthesizing non-allergenic, antigenic, and non-toxic epitopes for both Cytotoxic T Lymphocytes and Helper T Lymphocytes. Adjuvants were incorporated to enhance immunogenicity, and the vaccine's structure was modeled using advanced bioinformatics tools. The proposed vaccine demonstrated promising antigenicity and immunogenicity profiles, with a favorable physical-chemical property analysis. The vaccine's structures, designed by computational analysis, suggests high likelihood to native protein configurations. Antigenicity and allergenicity assessments validate the vaccine's immunogenic potential and hypoallergenic nature. Physicochemical evaluations indicate favorable stability and solubility profiles, essential for vaccine efficacy. This comprehensive approach to vaccine design expressed in Chlorella vulgaris holds promises for effective salmonellosis control. The multi-epitope vaccine, designed through meticulous in-silico methods, emerges as a promising candidate for controlling salmonellosis. Its strategic construction based on the fimH protein epitopes offers a targeted approach to elicit a robust immune response, potentially curbing the spread of this disease in poultry.

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.

Genetic engineering of Salmonella spp. for novel vaccine strategies and therapeutics

Salmonella enterica is a diverse species that infects both humans and animals. S. enterica subspecies enterica consists of more than 1,500 serovars. Unlike typhoidal Salmonella serovars which are human host-restricted, non-typhoidal Salmonella (NTS) serovars are associated with foodborne illnesses worldwide and are transmitted via the food chain. Additionally, NTS serovars can cause disease in livestock animals causing significant economic losses. Salmonella is a well-studied model organism that is easy to manipulate and evaluate in animal models of infection. Advances in genetic engineering approaches in recent years have led to the development of Salmonella vaccines for both humans and animals. In this review, we focus on current progress of recombinant live-attenuated Salmonella vaccines, their use as a source of antigens for parenteral vaccines, their use as live-vector vaccines to deliver foreign antigens, and their use as therapeutic cancer vaccines in humans. We also describe development of live-attenuated Salmonella vaccines and live-vector vaccines for use in animals.

Multiplex PCR-based genotyping of Salmonella Enteritidis and Salmonella Typhimurium from food sources and assessment of their antimicrobial resistance profiles in Egypt

BACKGROUND

Salmonellosis is a widespread zoonotic disease that poses a significant threat to livestock and public health. This study aimed to serotype 20 Salmonella isolates obtained from sixty retail chicken meats, assess Salmonella contamination from eggs, and evaluate antibiotic resistance profiles.

METHODS AND RESULTS

Twenty eggs were randomly collected in the new Borg El Arab market. Bacterial isolation was carried out utilizing both traditional culture, biochemical, and PCR methods. Among the twenty eggs analyzed, three (15%) tested positive for Salmonella, while the remaining seventeen (85%) were confirmed as negative. Genotyping through multiplex PCR revealed the presence of two S. Enteritidis and other serovar, with the use of three specific gene sets: a random sequence for Salmonella spp., sdfI gene for S. Enteritidis, and flagellin (fliC gene) for S. Typhimurium. Out of the 20 isolates obtained from chicken meat, five (25%) were identified as S. Typhimurium, and three (15%) were classified as S. Enteritidis. All isolates sourced from chicken meat exhibited resistance to Rifampicin and Amoxicillin, with 90% displaying sensitivity to cefotaxime, gemifloxacin, and Erythromycin. Importantly, S. Blegdam, identified via serological methods, displayed resistance to all tested antibiotics. For the three isolates obtained from eggs, 66.6% showed sensitivity to cefotaxime, erythromycin, cefuraxime, and cefaclor, while displaying complete resistance (100%) to Amoxicillin, rifampicin, clarithromycin, and cefadroxil. Notably, one serovar exhibited absolute resistance to all tested drugs.

CONCLUSION

Stakeholders must implement strict control measures and rationalize antibiotic use in veterinary and human medicine due to the rise of antibiotic-resistant strains.

Genomic analysis of a novel phage vB_SenS_ST1UNAM with lytic activity against Salmonella enterica serotypes

In this study, we present the complete annotated genome of a novel Salmonella phage, vB_SenS_ST1UNAM. This phage exhibits lytic activity against several Salmonella enterica serotypes, such as S. Typhi, S. Enteritidis, and S. Typhimurium strains, which are major causes of foodborne illness worldwide. Its genome consists of a linear, double-stranded DNA of 47,877 bp with an average G+C content of 46.6%. A total of 85 coding regions (CDS) were predicted, of which only 43 CDS were functionally assigned. Neither genes involved in the regulation of lysogeny, nor antibiotic resistance genes were identified. This phage harbors a lytic cassette that encodes a type II-holin and a Rz/Rz1-like spanin complex, along with a restriction-modification evasion system and a depolymerase that degrades Salmonella exopolysaccharide. Moreover, the comparative analysis with closely related phage genomes revealed that vB_SenS_ST1UNAM represents a novel genus, for which the genus "Gomezvirus" within the subfamily "ST1UNAM-like" is proposed.

Phytochemical composition, antioxidant, antibacterial, and enzyme inhibitory activities of organic extracts from flower buds of Cleistocalyx operculatus (Roxb.) Merr. et Perry

Cleistocalyx operculatus flower buds have been widely used in traditional medicine because of their rich content of bioactive constituents. In this study, we obtained seven solvent extracts from the flower buds and evaluated their total phenolic (TPC), flavonoid (TFC), tannin (TTC), triterpenoid saponin (TSC), and alkaloid (TAC) contents. We assessed antioxidant activities using the DPPH assay and also looked at antimicrobial and enzyme inhibitory effects. The water extract possessed the highest TPC (328.9 mg GAE/g extract), followed by ethanol, methanol, and hexane extracts (85.4-101.5 mg GAE/g extract). Chloroform, butanol, ethyl acetate, and ethanol extracts had high TSCs (245.4-287.2 mg OAE/g extract). The hexane extract was richest in TTC and TFC (32.7 mg CE/g extract and 81.1 mg QE/g extract, respectively). Ethanol and methanol extracts exhibited the strongest antioxidant activities (IC50 values of 25.2 and 30.3 μg/ml, respectively), followed by the water extract (IC50 of 40.2 μg/ml). The hexane extract displayed the most growth-inhibitory activity against Helicobacter pylori ATCC51932 and ATCC43504 strains and Salmonella enterica serovar Typhimurium ATCC13311 (MIC values of 0.06, 0.13, and 0.4 mg/ml, respectively). Moreover, the hexane extract revealed the strongest inhibition of H. pylori urease activity (IC50 of 4.51 μg/ml), whereas the water and methanol extracts had potent inhibitory effects on α-glucosidase activity (IC50 values of 9.9 and 15.1 μg/ml, respectively). These flower bud extracts could be used for health protection, especially in preventing bacterial infections and inhibiting enzymes associated with various human diseases. Further investigation into the application of C. operculatus flower buds in the food and pharmaceutical industries is necessary.

Molecular Characteristics of Salmonella Spp. Responsible for Bloodstream Infections in a Tertiary Hospital in Nanjing, China, 2019-2021

Objective

To investigate the clinical and molecular characteristics of Salmonella spp. causing bloodstream infections (BSIs) in our hospital.

Methods

We studied 22 clinical Salmonella isolates from BSIs and 16 from non-BSIs, performing antimicrobial susceptibility testing (AST) and whole genome sequencing (WGS). The analysis included serovars, antibiotic resistance genes (ARGs), virulence factors (VFs), sequence types (STs), plasmid replicons, and genetic relationships. We also assessed pathogenicity of the isolates causing BSIs through growth, biofilm formation, and anti-serum killing assays.

Results

WGS analysis identified 13 Salmonella serovars, with four responsible for BSIs. S. Enteritidis was the most prevalent serovar, involved in 19 (50.0%) cases. BSIs were caused by 17S. Enteritidis, two S. Typhimurium, two S. Munster and one S. Diguel. Of the 38 isolates, 27 (71.1%) exhibited high resistance to ampicillin, and 24 (63.2%) to ampicillin/sulbactam. Thirty-six types of ARGs were identified, with blaTEM-1B (n = 25, 65.8%) being the most frequent. Ten plasmid replicons were found; the combination of IncFIB(S)-IncFII(S)-IncX1 was the most common in S. Enteritidis (94.7%). Fifteen STs were identified, among which ST11 was the most prevalent and clonally disseminated, primarily responsible for BSIs. A total of 333 different VFs were detected, 177 of which were common across all strains. No significant differences were observed between the BSI and non-BSI isolates in terms of resistance rates, ARGs, plasmid replicons, and VFs, except for seven VFs. No strong pathogenicity was observed in the BSI-causing isolates.

Conclusion

BSIs were predominantly caused by clonally disseminated S. Enteritidis ST11, the majority of which carried multiple ARGs, VFs and plasmid replicons. This study provides the first data on clonally disseminated S. Enteritidis ST11 causing BSIs, highlighting the urgent need for enhanced infection control measures.

Development of super nanoantimicrobials combining AgCl, tetracycline and benzalkonium chloride

In this work, we demonstrate that a simple argentometric titration is a scalable, fast, green and robust approach for producing AgCl/antibiotic hybrid antimicrobial materials. We titrated AgNO3 into tetracycline hydrochloride (TCH) aqueous solution, thus forming AgCl/TCH in a one-step procedure. Furthermore, we investigated the one-pot synthesis of triply synergistic super-nanoantimicrobials, combining an inorganic source of Ag+ ions (AgCl), a disinfecting agent (benzyl-dimethyl-hexadecyl-ammonium chloride, BAC) and a molecular antibiotic (tetracycline hydrochloride, TCH). Conventional antimicrobial tests, industrial biofilm detection protocols, and in situ IR-ATR microbial biofilm monitoring, have been adapted to understand the performance of the synthesized super-nanoantimicrobial. The resulting hybrid AgCl/BAC/TCH nanoantimicrobials are found to be synergistically active in eradicating Salmonella enterica and Lentilactobacillus parabuchneri bacteria and biofilms. This study paves the way for the development of a new class of super-efficient nanoantimicrobials that combine relatively low amounts of multiple active species into a single (nano)formulation, thus preventing the development of antimicrobial resistance towards a single active principle.

The peptidoglycan-associated lipoprotein gene mutant elicits robust immunological defense in mice against Salmonella enteritidis

Background

Salmonella enteritidis (S. enteritidis), a zoonotic pathogen with a broad host range, presents a substantial threat to global public health safety. Vaccination stands as an effective strategy for the prevention and control of S. enteritidis infection, highlighting an immediate clinical need for the creation of safe and efficient attenuated live vaccines.

Methods

In this study, a S. enteritidis peptidoglycan-associated lipoprotein (pal) gene deletion strain (Δpal), was constructed. To assess its virulence, we conducted experiments on biofilm formation capability, motility, as well as cell and mouse infection. Subsequently, we evaluated the immune-protective effect of Δpal.

Results

It was discovered that deletion of the pal gene reduced the biofilm formation capability and motility of S. enteritidis. Cell infection experiments revealed that the Δpal strain exhibited significantly decreased abilities in invasion, adhesion, and intracellular survival, with downregulation of virulence gene expression, including mgtC, invH, spvB, sipA, sipB, ssaV, csgA, and pipB. Mouse infection experiments showed that the LD50 of Δpal increased by 104 times, and its colonization ability in mouse tissue organs was significantly reduced. The results indicated that the pal gene severely affected the virulence of S. enteritidis. Further, immunogenicity evaluation of Δpal showed a significant enhancement in the lymphocyte transformation proliferation capability of immunized mice, producing high titers of specific IgG and IgA, suggesting that Δpal possesses good immunogenicity. Challenge protection tests demonstrated that the strain could provide 100% immune protection against wild-type strains in mice.

Discussion

This study proves that the pal gene influences the virulence of S. enteritidis, and Δpal could serve as a candidate strain for attenuated live vaccines, laying the foundation for the development of attenuated live vaccines against Salmonella.

Synergistic and antibiofilm activity of DNase I and glucose oxidase loaded chitosan nanoparticles against dual-species biofilms of Listeria monocytogenes and Salmonella

Salmonella and Listeria monocytogenes are two of the most common foodborne pathogens in the food industry. They form dual-species biofilms, which have a higher sensitivity to antimicrobial treatment and a greater microbial adhesion. In this experiment, we loaded DNase I and glucose oxidase (GOX) on chitosan nanoparticles (CSNPs) to explore their inhibitory effects on and disruption of dual-species biofilms of Salmonella enterica and L. monocytogenes. Transmission electron microscopy (TEM) showed that CSNP-DNase-GOX and CSNPs were spherical in shape. CSNP-DNase-GOX was shifted and altered compared to the infrared peaks of CSNPs. CSNPs loaded with DNase I and GOX showed an increase in the particle size and an alteration in the polydispersity index (PDI) and the zeta potential. Compared to free DNase I or GOX, DNase I and GOX loaded on CSNPs had higher stability at different temperatures. CSNP-DNase-GOX was more effective in inhibiting dual-species biofilms than CSNP-GOX. Scanning electron microscopy (SEM) and fluorescence microscopy were used to observe the structure of the biofilm, which further illustrated that CSNP-DNase-GOX disrupted the dual-species biofilms of S. enterica and L. monocytogenes.

Acid Adaptation Enhances Tolerance of Escherichia coli O157:H7 to High Voltage Atmospheric Cold Plasma in Raw Pineapple Juice

Pathogens that adapt to environmental stress can develop an increased tolerance to some physical or chemical antimicrobial treatments. The main objective of this study was to determine if acid adaptation increased the tolerance of Escherichia coli O157:H7 to high voltage atmospheric cold plasma (HVACP) in raw pineapple juice. Samples (10 mL) of juice were inoculated with non-acid-adapted (NAA) or acid-adapted (AA) E. coli to obtain a viable count of ~7.00 log10 CFU/mL. The samples were exposed to HVACP (70 kV) for 1-7 min, with inoculated non-HVACP-treated juice serving as a control. Juice samples were analyzed for survivors at 0.1 h and after 24 h of refrigeration (4 °C). Samples analyzed after 24 h exhibited significant decreases in viable NAA cells with sub-lethal injury detected in both NAA and AA survivors (p < 0.05). No NAA survivor in juice exposed to HVACP for 5 or 7 min was detected after 24 h. However, the number of AA survivors was 3.33 and 3.09 log10 CFU/mL in juice treated for 5 and 7 min, respectively (p < 0.05). These results indicate that acid adaptation increases the tolerance of E. coli to HVACP in pineapple juice. The potentially higher tolerance of AA E. coli O157:H7 to HVACP should be considered in developing safe juice processing parameters for this novel non-thermal technology.

Hand contamination and hand hygiene knowledge and practices among commercial transport users after the SARS-CoV-2 virus (COVID-19) scare, Enugu State, Nigeria

Contaminated hands are one of the most common modes of microorganism transmission that are responsible for many associated infections in healthcare, food industries, and public places such as transportation parks. Public health approaches during COVID-19 pandemic have shown that hand hygiene practices and associated knowledge are critical measure to control the spread of infectious agent. Hence, assessment of commercial transport users' knowledge, belief and practices on hand hygiene, and potential contamination with infectious agents which is the aim of the study, aligns with general health concern of quantifying contamination risk levels to predict disease outbreaks. This study utilized a randomized sampling approach to select 10 frequently used commercial parks within two districts in the State: Enugu and Nsukka. The parameters analysed include a cross-sectional questionnaire survey, hand swab and hand washed samples collected from dominant hand of participants. A total of 600 participants responded to the questionnaire survey, while 100 participants' hand swabs were examined for microbial contamination. This study recorded a high prevalence of fungal (90.0%) and bacterial (87.0%) species; 20 species of fungus were identified with prevalence range of 1% to 14%; 21 bacterial species were isolated with prevalence range of 1% to 16%. These species were identified as either opportunistic, non-invasive, or pathogenic, which may constitute a health concern amongst immunocompromised individuals within the population. Aspergillus spp. (14%), was the most common fungal species that was exclusively found amongst Nsukka commercial users, while E. coli was the most prevalent isolated bacterial species amongst Nsukka (12%) and Enugu (20%) commercial park users. Prevalence of fungal contamination in Nsukka (94.0%; 47/50) and Enugu (86.0%; 43/50) were both high. Prevalence of bacterial contamination was higher in Enugu than Nsukka but not significantly (47[94.0%] vs. 40[80.0%], p = 0.583). A greater number of participants (99.3%) were aware of the importance of hand hygiene, however with low compliance rate aside "after using the toilet" (80%) and "before eating" (90%), other relevant hand washing and sanitizing practices were considered less important. With these observations, we can emphatically say that despite the COVID-19 scare, commercial park users within the sampled population do not efficiently practice quality hand wash and hygiene measures, hence, risking the widespread of infectious agents in situation of disease outbreak or among immunocompromised individuals.

Genetic Characteristics of Extended-Spectrum Beta-Lactamase-Producing Salmonella Isolated from Retail Meats in South Korea

Earlier studies have validated the isolation of extended-spectrum beta-lactamase-producing Salmonella (ESBL-Sal) strains from food. While poultry is recognized as a reservoir for Salmonella contamination, pertinent data regarding ESBL-Sal remains limited. Consequently, the Ministry of Food and Drug Safety has isolated Salmonella spp. from retail meat and evaluated their antibiotic susceptibility and genetic characteristics via whole-genome sequencing. To further elucidate these aspects, this study investigates the prevalence, antibiotic resistance profiles, genomic characteristics, and homology of ESBL-Sal spp. obtained from livestock-derived products in South Korean retail outlets. A total of 653 Salmonella spp. were isolated from 1,876 meat samples, including 509 beef, 503 pork, 555 chicken, and 309 duck samples. The prevalence rates of Salmonella were 0.0%, 1.4%, 17.5%, and 28.2% in the beef, pork, chicken, and duck samples, respectively. ESBL-Sal was exclusively identified in poultry meat, with a prevalence of 1.4% in the chicken samples (8/555) and 0.3% in the duck samples (1/309). All ESBL-Sal strains carried the blaCTX-M-1 gene and exhibited resistance to ampicillin, ceftiofur, ceftazidime, nalidixic acid, and tetracycline. Eight ESBL-Sal isolates were identified as S. Enteritidis with sequence type (ST) 11. The major plasmid replicons of the Enteritidis-ST11 strains were IncFIB(S) and IncFII(S), carrying antimicrobial resistance genes (β-lactam, tetracycline, and aminoglycoside) and 166 virulence factor genes. The results of this study provide valuable insights for the surveillance and monitoring of ESBL-Sal in South Korean food chain.

Effect of oral administration of microcin Y on growth performance, intestinal barrier function and gut microbiota of chicks challenged with Salmonella Pullorum

The lasso peptide microcin Y (MccY) effectively inhibits various serotypes of Salmonella in vitro, but the antibacterial effect against S. Pullorum in poultry is still unclear. This study was the first to evaluate the safety and anti-S. Pullorum infection of MccY in specific pathogen-free (SPF) chicks. The safety test showed that the body weight, IgA and IgM levels of serum, and cecal microbiota structure of 3 groups of chicks orally administrated with different doses of MccY (5 mg/kg, 10 mg/kg, 20 mg/kg) for 14 days were not significantly different from those of the control group. Then, the chicks were randomized into 3 groups for the experiment of anti-S. Pullorum infection: (I) negative control group (NC), (II) S. Pullorum-challenged group (SP, 5 × 108 CFU/bird), (III) MccY-treated group (MccY, 20 mg/kg). The results indicated that compared to the SP group, treatment of MccY increased body weight and average daily gain (P < 0.05), reduced S. Pullorum burden in feces, liver, and cecum (P < 0.05), enhanced the thymus, and decreased the spleen and liver index (P < 0.05). Additionally, MccY increased the jejunal villus height, lowered the jejunal and ileal crypt depth (P < 0.05), and upregulated the expression of IL-4, IL-10, ZO-1 in the jejunum and ileum, as well as CLDN-1 in the jejunum (P < 0.05) compared to the SP group. Furthermore, MccY increased probiotic flora (Barnesiella, etc.), while decreasing (P < 0.05) the relative abundance of pathogenic flora (Escherichia and Salmonella, etc.) compared to the SP group.

Antimicrobial resistance and genetic relatedness of Salmonella serotypes isolated from food, asymptomatic carriers, and clinical cases in Shiyan, China

Salmonella is a primary cause of foodborne diseases globally. Despite food contamination and clinical infections garnering substantial attention and research, asymptomatic Salmonella carriers, potential sources of infection, have been comparatively overlooked. In this study, we conducted a comparative analysis of serotype distribution, antimicrobial resistance phenotypes, and genetic profiles of archived Salmonella strains isolated from food (26), asymptomatic carriers (41), and clinical cases (47) in Shiyan City, China. Among the 114 Salmonella strains identified, representing 31 serotypes and 34 Sequence Types (STs), the most prevalent serovars included Typhimurium, Derby, Enteritidis, Thompson, and London, with the most predominant STs being ST11, ST40, ST26, ST34, and ST155. Antimicrobial resistance testing revealed that all strains were only sensitive to meropenem, with 74.6% showing antimicrobial resistance (AMR) and 53.5% demonstrating multidrug resistance (MDR). Strains resistant to five and six classes of antibiotics were the most common. Pearson's chi-square test showed no statistically significant difference in the occurrence of AMR (p = 0.105) or MDR (p = 0.326) among Salmonella isolates from the three sources. Our findings underscore associations and diversities among Salmonella strains isolated from food, asymptomatic carriers, and clinical patients, emphasizing the need for increased vigilance towards asymptomatic Salmonella carriers by authorities.

Effect of Selective Enrichment Storage Temperature and Duration Time on the Detection of Salmonella in Food

BACKGROUND

For pathogen detection in food, there are occasions where samples cannot be processed immediately after selective enrichment or need to be reexamined days or weeks later for confirmation or retest.

OBJECTIVE

This study aimed to investigate the effect of different prolonged period of storage of selective enrichments of food at 4 ± 2°C and room temperature (20-22°C) on the detection and isolation of Salmonella.

METHOD

This study included two experiments involving 34 types of foods to compare the effect of 4 ± 2°C and room temperature storage on the detection of Salmonella in 204 selective enrichments (Rappaport-Vassiliadis [RV] and Tetrathionate [TT] broths) during a 42-day storage (Experiment I); and to monitor the survival of Salmonella in 300 selective enrichments (RV and TT) with different pre-enrichment broths (Lactose broth [LB] or Buffered peptone water broth [BPW]), stored at 4°C for 60 days (Experiment II). All the samples were subjected to Salmonella analysis following the FDA BAM method.

RESULTS

During multiple samplings, the positive detection rate for Salmonella remained consistent through Day 42 after selective enrichment, irrespective of Salmonella serotype, storage temperature, pre-enrichment broth, or selective enrichment broth in both Experiment I and II. However, on Day 60 sampling in Experiment II, seven previously positive results turned to negatives. These data indicated that storage of RV and TT enrichments at 4 ± 2°C or room temperature for up to 42 days after selective enrichment did not compromise the detection of Salmonella in the tested food categories, regardless of Salmonella serotypes and the broths used for pre-enrichment and selective enrichment.

CONCLUSIONS

At least for the food types studied in this experiment, the recovery of Salmonella from selective enrichments could be postponed for a limited period of time (e.g., <42 days) if needed without adversely affecting the test results. However, the delayed analysis of TT and RV enrichments does pose a risk of reduced detection sensitivity, as evidenced by the seven negative results on Day 60 compared to previous positives. We do not recommend or endorse delaying the analysis of TT and RV enrichments.

HIGHLIGHTS

In the food matrixes investigated in this experiment, the plating and isolation of Salmonella from selective TT and RV enrichments stored at 4 ± 2°C or room temperature could be deferred for a period (up to 42 days) without any negative effect on the test results, if necessary.

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.

Occurrence, antimicrobial resistance, and molecular characterization of Salmonella enterica from chicken products and human in Wasit Governorate of Iraq

Background

Salmonella infections are considered the most common foodborne pathogens responsible for zoonotic infections and food poisoning in humans and animal species such as birds. Antimicrobial resistance is considered a global anxiety because it causes human public health repercussions, as well as leads to an increase in animal morbidity and death.

Aim

The aims of this study are the isolation and identification of Salmonella enterica, as well as to investigate the antimicrobial susceptibility test (AST) and the molecular characteristics using polymerase chain reaction (PCR) and sequences for isolates from chicken products (eggs, livers, and minced meat) and human in the Wasit Governorate of Iraq.

Methods

A total of 300 samples (150 chicken product samples including eggs, livers, and minced meat, and 150 human fecal samples) were collected from the Wasit governorate of Iraq from January to December 2022. The bacterial isolation was done according to recommendations of ISO 6579 standard and the Global Foodborne Infections Network laboratory protocol. Serotyping test and AST were done by using 19 antibiotic agents according to the recommendations of the Clinical and Laboratory Standards Institute, 2022 by using disc diffusion susceptibility test and Vitik 2 test. Finally, the suspected isolates were confirmed using the conventional PCR method and sequencing for a unique rRNA gene.

Results

The results showed that the isolation percentage of S. enterica in chicken products was 8.66% (12% eggs, 6% livers, and 8% minced meat), while in humans it was 4.6%. Also, showed 100% of Salmonella typhi in humans. While, in chicken eggs S. typhi, Salmonella typhimurium, and Salmonella enteritidis were 50%, 33.33%, and 16.66%, respectively. Also, showed 100% of S. typhimurium in both livers and minced meat. The AST in human isolates showed resistance to Ampicillin, Cefotaxime, Ceftazidime, Cefepime, Amikacin, Gentamicin, Ciprofloxacin, Norfloxacin, and Ceftriaxone, while no resistance to Amoxicillin, Pipracillin, Ertapenem, Imipenem, Meropenem, Fosfomycin, Nitrofurantoin, Trimethoprim, Azithromycin, and Tetracycline. In chicken products, isolates were resistant with different percentages to Amikacin, Gentamicin, Tetracycline, Ciprofloxacin, Norfloxacin, Nitrofurantoin, Ampicillin, Cefotaxime, Ceftazidime, Cefepime, and Trimethoprim; while no resistance to Amoxicillin, Pipracillin, Ertapenem, Imipenem, Meropenem, Fosfomycin, Azithromycin, and Ceftriaxone. Sequencing by using rRNA gene was done for four PCR products.

Conclusion

This study showed the presence of genetic mutations for S. enterica which led to variations in the molecular characteristics, and antimicrobial drug resistance of S. enterica isolated from chicken products and humans.

STM1863, a Member of the DUFs Protein Family, Is Involved in Environmental Adaptation, Biofilm Formation, and Virulence in Salmonella Typhimurium

Salmonella Typhimurium (STM) is an important zoonotic Gram-negative pathogen that can cause infection in a variety of livestock and poultry. Meanwhile, as an important foodborne pathogen, the bacterium can survive in various stressful environments and transmits through the fecal-oral route, posing a serious threat to global food safety. To investigate the roles of STM1863, a member of the DUFs protein family, involved in STM environmental adaptation, biofilm formation, and virulence. We analyzed the molecular characteristics of the protein encoded by STM1863 gene and examined intra- and extracellular expression levels of STM1863 gene in mouse macrophages. Furthermore, we constructed STM1863 gene deletion and complementation strains and determined its environmental adaptation under stressful conditions such as acid, alkali, high salt, bile salt, and oxidation. And the capacity of biofilm formation and pathogenicity of those strains were analyzed and compared. In addition, the interaction between the promoter of STM1863 gene and RcsB protein was analyzed using DNA gel electrophoresis migration assay (electrophoretic mobility shift assay [EMSA]). The experiments revealed that acid adaptability and biofilm formation ability of STM1863 gene deletion strain were significantly weakened compared with the parental and complementary strains. Moreover, the adhesion and invasion ability of STM1863 deletion strain to mouse macrophages was significantly decreased, while the median lethal dose (LD50) increased by 2.148-fold compared with the parental strain. In addition, EMSA confirmed that RcsB protein could bind to the promoter sequence of STM1863 gene, suggesting that the expression of STM1863 gene might be modulated by RcsB. The present study demonstrated for the first time that STM1863, a member of the DUFs protein family, is involved in the modulation of environmental adaptation, biofilm formation, and virulence.

Prevalence, Molecular Detection, and Antimicrobial Resistance of Salmonella Isolates from Poultry Farms across Central Ethiopia: A Cross-Sectional Study in Urban and Peri-Urban Areas

A cross-sectional study was conducted to assess the prevalence, molecular detection, and antimicrobial resistance of Salmonella isolates within 162 poultry farms in selected urban and peri-urban areas of central Ethiopia. A total of 1515 samples, including cloacal swabs (n = 763), fresh fecal droppings (n = 188), litter (n = 188), feed (n = 188), and water (n = 188), were bacteriologically tested. The molecular detection of some culture-positive isolates was performed via polymerase chain reaction (PCR) by targeting spy and sdfl genes for Salmonella Typhimurium and Salmonella Enteritidis, respectively. Risk factors for the occurrence of the bacterial isolates were assessed. Antimicrobial susceptibility testing of PCR-confirmed Salmonella isolates was conducted using 12 antibiotics. In this study, it was observed that 50.6% of the farms were positive for Salmonella. The overall sample-level prevalence of Salmonella was 14.4%. Among the analyzed risk factors, the type of production, breed, and sample type demonstrated a statistically significant association (p < 0.05) with the bacteriological prevalence of Salmonella. The PCR test disclosed that 45.5% (15/33) and 23.3% (10/43) of the isolates were positive for genes of Salmonella Typhimurium and Salmonella Enteritidis, respectively. The antimicrobial susceptibility test disclosed multi-drug resistance to ten of the tested antibiotics that belong to different classes. Substantial isolation of Salmonella Typhimurium and Salmonella Enteritidis in poultry and on poultry farms, along with the existence of multi-drug resistant isolates, poses an alarming risk of zoonotic and food safety issues. Hence, routine flock testing, farm surveillance, biosecurity intervention, stringent antimicrobial use regulations, and policy support for the sector are highly needed.

Antibacterial effect of curcumin on Salmonella Typhimurium: In vitro and food model studies

Salmonellosis is a major foodborne disease transmitted from contaminated poultry products worldwide. Although a wide variety of chemical agents are used in the prevention of foodborne Salmonella spp. infections, consumers prefer natural additives, that do not harm human health and do not impair the characteristics of food. Curcumin is a yellow-coloured, hydrophobic polyphenol obtained from the rhizome of the Curcuma longa L. plant known as turmeric. The purpose of this study was to evaluate curcumin's antibacterial activity against S. Typhimurium in chicken meat and in vitro. In the first step, chicken samples were experimentally contaminated with S. Typhimurium at a level of 2.8 × 10-7 CFU/ml. Then, they were kept in a 1, 2, and 3% curcumin solution for 15 minutes. At the end of the treatment, chicken samples were stored at +4 °C. The number of S. Typhimurium in chicken samples was determined according to EN ISO 6579-1. In the result of the study, the number of S. Typhimurium decreased by 2.37, 2.71, and 2.84 log levels at the end of the 6th day as a result of the 1, 2 and 3% curcumin treatment, respectively. The MIC value of curcumin was determined to be 362 μg/ml for S. Typhimurium.

Rapid and sensitive detection of Salmonella in agro-Food and environmental samples: A review of advances in rapid tests and biosensors

Salmonella is as an intracellular bacterium, causing many human fatalities when the host-specific serotypes reach the host gastrointestinal tract. Nontyphoidal Salmonella are responsible for numerous foodborne outbreaks and product recalls worldwide whereas typhoidal Salmonella are responsible for Typhoid fever cases in developing countries. Yet, Salmonella-related foodborne disease outbreaks through its food and water contaminations have urged the advancement of rapid and sensitive Salmonella-detecting methods for public health protection. While conventional detection methods are time-consuming and ineffective for monitoring foodstuffs with short shelf lives, advances in microbiology, molecular biology and biosensor methods have hastened the detection. Here, the review discusses Salmonella pathogenic mechanisms and its detection technology advancements (fundamental concepts, features, implementations, efficiency, benefits, limitations and prospects). The time-efficiency of each rapid test method is discussed in relation to their limit of detections (LODs) and time required from sample enrichment to final data analysis. Importantly, the matrix effects (LODs and sample enrichments) were compared within the methods to potentially speculate Salmonella detection from environmental, clinical or food matrices using certain techniques. Although biotechnological advancements have led to various time-efficient Salmonella-detecting techniques, one should consider the usage of sophisticated equipment to run the analysis by moderately to highly trained personnel. Ultimately, a fast, accurate Salmonella screening that is readily executed by untrained personnels from various matrices, is desired for public health procurement.

Occurrence of Salmonella spp. in animal patients and the hospital environment at a veterinary academic hospital in South Africa

Background and Aims

Nosocomial infections caused by Salmonella spp. are common in veterinary facilities. The early identification of high-risk patients and sources of infection is important for mitigating the spread of infections to animal patients and humans. This study investigated the occurrence of Salmonella spp. among patients at a veterinary academic hospital in South Africa. In addition, this study describes the environmental factors that contribute to the spread of Salmonella spp. in the veterinary facility.

Materials and Methods

This study used a dataset of Salmonella-positive animals and environmental samples submitted to the bacteriology laboratory between 2012 and 2019. The occurrence of Salmonella isolates at the veterinary hospital was described based on source, month, season, year, and location. Proportions and 95% confidence intervals were calculated for each variable.

Results

A total of 715 Salmonella isolates were recorded, of which 67.6% (483/715) came from animals and the remainder (32.4%, 232/715) came from environmental samples. The highest proportion (29.2%) of Salmonella isolates was recorded in 2016 and most isolates were reported in November (17.4%). The winter season had the lowest (14.6%) proportion of isolates reported compared to spring (31.3%), summer (27.8%), and autumn (26.4%). Salmonella Typhimurium (20.0%) was the most frequently reported serotype among the samples tested, followed by Salmonella Anatum (11.2%). Among the positive animal cases, most (86.3%) came from equine clinics. Most reported isolates differed based on animal species with S. Typhimurium being common in equines and S. Anatum in bovines.

Conclusion

In this study, S. Typhimurium emerged as the predominant strain in animal and environmental samples. Equines were the most affected animals; however, Salmonella serotypes were also detected in the production animals. Environmental contamination was also a major source of Salmonella species in this study. To reduce the risk of transmission, strict infection prevention and control measures (biosecurity) must be implemented.

Characterization of Salmonella phages isolated from poultry coops and its effect with nisin on food bio-control

Salmonella is a bacterium associated with food contaminated by various animals, primarily poultry. Interest and research on bacteriophages are increasing because they can be used as an alternative against increasing antibiotic resistance. In our study, eight Salmonella-specific lytic bacteriophages were isolated from chicken feces. Two of the isolated phages (AUFM_Sc1 and AUFM_Sc3) were chosen for their characterization due to their broader host range. Based on morphological and genomic analysis, AUFM_Sc1 was identified to be close to similar Enterobacteria spp. CC31 (Myoviridae) and AUFM_Sc3 was identified to be close to Salmonella phage vB_Sen_I1 (Demerecviridae (formerly Siphoviridae)). Although these phages have shown promise for use in phage therapy applications for chickens, further studies are needed on their suitability. When a cocktail of these phages (AUFM_Sc1 + AUFM_Sc3) and nisin combination was applied on chicken breast meat, it was determined that it was effective against Salmonella contamination and while a good inhibitory effect was observed on the food, especially during the first 48 h, the effect decreased later, but the bacterial concentration was still low compared to the control group. Therefore, it is considered that the combination of AUFM_Sc1 + AUFM_Sc3 + nisin can be used as a food preservative against Salmonella.

Antibiotic Resistance Profile of Salmonella sp. Isolates from Commercial Laying Hen Farms in Central-Western Brazil

Microbial resistance to antibiotics poses a significant threat to both human and animal health, necessitating international efforts to mitigate this issue. This study aimed to assess the resistance profiles of Salmonella sp. isolates and identify the presence of intl1, sul1, and blaTEM resistance genes within antigenically characterized isolates, including Agona, Livingstone, Cerro, Schwarzengrund, Salmonella enterica subsp. enterica serotype O:4.5, Anatum, Enteritidis, Johannesburg, Corvallis, and Senftenberg. These isolates underwent susceptibility testing against 14 antibiotics. The highest resistance percentages were noted for sulfamethoxazole (91%), sulfonamides (51%), and ceftiofur (28.9%), while no resistance was observed for ciprofloxacin. Salmonella Johannesburg and Salmonella Corvallis showed resistance to one antibiotic, whereas other serovars were resistant to at least two. Salmonella Schwarzengrund exhibited resistance to 13 antibiotics. The intl1 gene was detected in six out of the ten serovars, and the sul1 gene in three, always co-occurring with intl1. The blaTEM gene was not identified. Our findings highlight the risk posed by the detected multiple resistances and genes to animal, human, and environmental health. The multidrug resistance, especially to third-generation cephalosporins and fluoroquinolones, highlights the need for stringent monitoring of Salmonella in laying hens. The potential of the environment, humans, eggs, and their products to act as vectors for antibiotic resistance represents a significant concern for One Health.

Salmonella enterica serovars linked with poultry in India: antibiotic resistance profiles and carriage of virulence genes

Salmonella is an important poultry pathogen with zoonotic potential. Being a foodborne pathogen, Salmonella-contaminated poultry products can act as the major source of infection in humans. In India, limited studies have addressed the diversity of Salmonella strains of poultry origin. This study represented 26 strains belonging to Salmonella serovars Typhimurium, Infantis, Virchow, Kentucky, and Agona. The strains were tested for resistance to 14 different antimicrobial agents using the Kirby-Bauer disk-diffusion assay. The presence of the invA, hilA, agfA, lpfA, sopE, and spvC virulence genes was assessed by polymerase chain reaction (PCR), and the genetic diversity was assessed by Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC-PCR). The highest resistance to tetracycline (n = 17; 65.38%) followed by nalidixic acid (n = 16; 61.53%) was detected among the strains. Among the strains (n = 17) phenotypically resistant to tetracycline, 94% (n = 16) were also positive for the tetA gene. Based on the presence of virulence genes, the strains were characterized into three virulence profiles (PI, P2, and P3). Among the investigated virulence genes, invA, hilA, agfA, and lpfA were present in all strains. The sopE gene was mostly associated with serovars Virchow (n = 3; 100%) and Typhimurium (n = 8; 80%), whereas spvC gene was exclusive for two Typhimurium strains that lacked sopE gene. ERIC-PCR profiling indicated clusters correlating their serovar, geographical, and farm origins. These results demonstrate that Salmonella isolates with a wide genetic range, antibiotic resistance, and virulence characteristics can colonize poultry. The presence of such strains is crucial for both food safety and public health.

Genetic Characteristics of Salmonella Isolates Recovered From Reused Broiler Litter Over Three Successive Flocks

Salmonella infections are a leading cause of bacterial food-borne illness worldwide. Infections are highly associated with the consumption of contaminated food, and in particular, chicken meat. The severity of Salmonella infections depends on the presence of antimicrobial resistance genes and virulence factors. While there are many studies which have investigated Salmonella strains isolated from postharvest chicken samples, there is a gap in our understanding of the genetic properties that influence the persistence of Salmonella in preharvest and in particular their makeup of antimicrobial resistance genes and virulence factors. We used whole genome sequencing and hierarchical clustering to characterize and classify the genetic diversity of Salmonella enterica isolates (n = 55) recovered from the litter of commercial broiler chicken raised in four colocated broiler houses of one integrated farm over three consecutive flocks. The chicken were raised under a newly adopted "No Antibiotics Ever" program, and copper sulfate was administered via drinking water. In-silico serovar prediction identified three S. enterica serovars: Enteritidis (n = 12), Kentucky (n = 40), and Senftenberg (n = 3). Antimicrobial susceptibility testing revealed that only one S. Kentucky isolate was resistant to streptomycin, while the remaining isolates were susceptible to all antibiotics tested. Metal resistance operons, including copper and silver, were identified chromosomally and on plasmids in serovar Senftenberg and Kentucky isolates, respectively, while serovar Enteritidis carried several virulence factors on plasmids. Serovar Kentucky isolates harboring metal resistance operons were the only Salmonella isolates recovered from the litter of third flock cohort. These results suggest that there might be environmental selection for Salmonella strains carrying plasmid-associated metal resistance and virulence genes, which could play a role in their persistence in litter.

Deciphering the Interrelationship of arnT Involved in Lipid-A Alteration with the Virulence of Salmonella Typhimurium

The lipopolysaccharide (LPS) that resides on the outermost surface and protects Gram-negative bacteria from host defenses is one of the key components leading to Salmonella infection, particularly the endotoxic lipid A domain of LPS. Lipid A modifications have been associated with several genes such as the arnT that encodes 4-amino-4-deoxy-L-arabinose transferase, which can be critical for bacteria to resist cationic antimicrobial peptides and interfere with host immune recognition. However, the association of arnT with virulence is not completely understood. Thus, this study aimed to elucidate the interrelationship of the major lipid A modification gene arnT with Salmonella Typhimurium virulence. We observed that the arnT-deficient S. Typhimurium (JOL2943), compared to the wild type (JOL401), displayed a significant decrease in several virulence phenotypes such as polymyxin B resistance, intracellular survival, swarming, and biofilm and extracellular polymeric substance (EPS) production. Interestingly, the cell-surface hydrophobicity, adhesion, and invasion characteristics remained unaffected. Additionally, LPS isolated from the mutant induced notably lower levels of endotoxicity-related cytokines in RAW and Hela cells and mice, particularly IL-1β with a nine-fold decrease, than WT. In terms of in vivo colonization, JOL2943 showed diminished presence in internal organs such as the spleen and liver by more than 60%, while ileal infectivity remained similar to JOL401. Overall, the arnT deletion rendered the strain less virulent, with low endotoxicity, maintained gut infectivity, and reduced colonization in internal organs. With these ideal characteristics, it can be further explored as a potential attenuated Salmonella strain for therapeutics or vaccine delivery systems.

Monitoring the long-term spatiotemporal transmission dynamics and ecological surveillance of multidrug-resistant Salmonella enterica serovar Goldcoast: A multicenter genomic epidemiology study

The emergence of multidrug-resistant Salmonella enterica serovar Goldcoast poses a significant threat to the effective treatment and control of salmonellosis within the ecological environment. Here, we conducted a genomic epidemiological study delineate the global dissemination scenarios of the multidrug-resistant S. Goldcoast originated from 11 countries for over 20 years. The population structure and evolutionary history of multidrug-resistant S. Goldcoast was investigated through phylogenomic and long-term spatiotemporal transmission dynamic analysis. ST358 and ST2529 are the predominant lineages of S. Goldcoast. Multidrug-resistant S. Goldcoast strains have mainly been identified in the ST358 lineage from human and the ST2529 lineage from livestock. ST358 S. Goldcoast was estimated to have emerged in the United Kingdom in 1969, and then spread to China, with both countries serve as centers for the global dissemination of the ST358 lineage. After its emergence and subsequent spread in Chinese clinical and environmental samples, occasional instances of this lineage have been reported in Canada, the United Kingdom, and Ireland. Clonal transmission of ST358 and ST2529 S. Goldcoast have occurred not only on an international and intercontinental scale but also among clinical, environmental and livestock samples. These data indicated that international circulation and local transmission of S. Goldcoast have occurred for over a decade. Continued surveillance of multidrug-resistant S. Goldcoast from a global "One Health" perspective is urgently needed to facilitate monitoring the spread of the antimicrobial resistant high-risk clones.

A flow cytometric assay to detect viability and persistence of Salmonella enterica subsp. enterica serotypes in nuclease-free water at 4 and 25°C

Salmonella spp. is one of the most isolated microorganisms reported to be responsible for human foodborne diseases and death. Water constitutes a major reservoir where the Salmonella spp. can persist and go undetected when present in low numbers. In this study, we assessed the viability of 12 serotypes of Salmonella enterica subsp. enterica for 160 days in nuclease-free water at 4 and 25°C using flow cytometry and Tryptic Soy Agar (TSA) plate counts. The results show that all 12 serotypes remain viable after 160 days in distilled water using flow cytometry, whereas traditional plate counts failed to detect ten serotypes incubated at 25°C. Moreover, the findings demonstrate that 4°C constitutes a more favorable environment where Salmonella can remain viable for prolonged periods without nutrients. Under such conditions, however, Salmonella exhibits a higher susceptibility to all tested antibiotics and benzalkonium chloride (BZK). The pre-enrichment with Universal Pre-enrichment Broth (UP) and 1/10 × Tryptic Soy broth (1/10 × TSB) resuscitated all tested serotypes on TSA plates, nevertheless cell size decreased after 160 days. Furthermore, phenotype microarray (PM) analysis of S. Inverness and S. Enteritidis combined with principal component analysis (PCA) revealed an inter-individual variability in serotypes with their phenotype characteristics, and the impact of long-term storage at 4 and 25°C for 160 days in nuclease-free water. This study provides an insight to Salmonella spp. long-term survivability at different temperatures and highlights the need for powerful tools to detect this microorganism to reduce the risk of disease transmission of foodborne pathogens via nuclease-free water.

Genomic characterization, in vitro, and preclinical evaluation of two microencapsulated lytic phages VB_ST_E15 and VB_ST_SPNIS2 against clinical multidrug-resistant Salmonella serovars

BACKGROUND

Salmonella infections continue to be one of the essential public health issues threatening millions of people. With the increasing occurrence of resistance against conventionally used antibiotics, the search for alternatives has become crucial. In this study, we aimed to isolate, characterize, and evaluate two lytic bacteriophages against clinically isolated multidrug-resistant (MDR) Salmonella serovars.

METHODS

Screening for the phage lytic activity was performed using a spot test. Characterization of the isolated phages was done by determining the host range, longevity test, and the effect of temperature, pH, organic solvents, and morphological characterization using a transmission electron microscope. Genomic analysis was performed using Oxford nanopore sequencing. The lytic activities of the free phage lysates and formulated phage as microencapsulated were evaluated both in vitro and in vivo.

RESULTS

Two phages (VB_ST_E15 and VB_ST_SPNIS2) were successfully isolated and showed lytic strong activities against MDR Salmonella (S.) Typhimurium ATCC 14,028, S. Paratyphi A, and S. Typhi. The two phages survived at the tested temperatures, maintained their infectivity for 90 days, and retained their activity until 60 °C with thermal inactivation at 65 °C. They were lytic at a pH range from 3 to 11 but lost their activities at extremely acidic or alkaline pH. The phages could withstand the organic solvents but were completely inactivated by 100% ethanol. Both phages were classified under the order Caudoviricetes, and Genus: Uetakevirus. Their genomic sequences were assembled, annotated, and submitted to the NCBI GenBank database (OR757455 and OR757456). The preclinical evaluation using the murine animal model revealed that the two-phage cocktail managed MDR Salmonella infection as evidenced by the reduction in the bacterial burden, increased animal weight, and histopathological examination.

CONCLUSION

The two encapsulated phage formulas could be considered promising candidates for the management of MDR Salmonella-associated infections and clinical analysis should be undertaken to evaluate their potential use in humans.

Salmonella Vitkin Outbreak Associated with Bearded Dragons, Canada and United States, 2020-2022

We identified 2 cases of Salmonella enterica serovar Vitkin infection linked by whole-genome sequencing in infants in Ontario, Canada, during 2022. Both households of the infants reported having bearded dragons as pets. The outbreak strain was also isolated from an environmental sample collected from a patient's bearded dragon enclosure. Twelve cases were detected in the United States, and onset dates occurred during March 2021-September 2022 (isolates related to isolates from Canada within 0-9 allele differences by core-genome multilocus sequence typing). Most US patients (66.7%) were <1 year of age, and most (72.7%) had reported bearded dragon exposure. Hospitalization was reported for 5 (38.5%) of 13 patients. Traceback of bearded dragons identified at least 1 potential common supplier in Southeast Asia. Sharing rare serovar information and whole-genome sequencing data between Canada and the United States can assist in timely identification of outbreaks, including those that might not be detected through routine surveillance.

Genomic-wide analysis approach revealed genomic similarity for environmental Mexican S. Oranienburg genomes

As the human population grows, an increase in food trade is needed. This elevates the risk of epidemiological outbreaks. One of the prevalent pathogens associated with food production in Mexico has been Salmonella Oranienburg. Effective surveillance systems require microbial genetic knowledge. The objective of this work is to describe the genetic composition of Mexican S. Oranienburg genomes. For that, 53 strains from different environmental sources were isolated and sequenced. Additionally, 109 S. Oranienburg genomes were downloaded. Bioinformatic analyses were used to explore the clonal complex and genomic relatedness. A major clonal group formed by ST23 was identified comprising four STs. 202 SNPs were found the maximum difference among isolates. Virulence genes for host invasion and colonization as rpoS, fimbria type 1, and, T3SS were found common for all isolates. This study suggests that Mexican S. Oranienburg strains are potential pathogens circulating continuously in the region between host and non-host environments.

Novel Lactobacillaceae strains and consortia to produce propionate-containing fermentates as biopreservatives

Biopreservation refers to the use of natural or controlled microbial single strains or consortia, and/or their metabolites such as short-chain carboxylic acids (SCCA), to improve the shelf-life of foods. This study aimed at establishing a novel Lactobacillaceae-driven bioprocess that led to the production of the SCCA propionate through the cross-feeding on 1,2-propanediol (1,2-PD) derived from the deoxyhexoses rhamnose or fucose. When grown as single cultures in Hungate tubes, strains of Lacticaseibacillus rhamnosus preferred fucose over rhamnose and produced 1,2-PD in addition to lactate, acetate, and formate, while Limosilactobacillus reuteri metabolized 1,2-PD into propionate, propanol and propanal. Loigolactobacillus coryniformis used fucose to produce 1,2-PD and only formed propionate when supplied with 1,2-PD. Fermentates collected from batch fermentations in bioreactor using two-strain consortia (L. rhamnosus and L. reuteri) or fed-batch fermentations of single strain cultures of L. coryniformis with rhamnose contained mixtures of SCCA consisting of mainly lactate and acetate and also propionate. Synthetic mixtures that contained SCCA at concentrations present in the fermentates were more antimicrobial against Salmonella enterica if propionate was present. Together, this study (i) demonstrates the potential of single strains and two-strain consortia to produce propionate in the presence of deoxyhexoses extending the fermentation metabolite profile of Lactobacillaceae, and (ii) emphasizes the potential of applying propionate-containing fermentates as biopreservatives.

Effect of Salmonella pathogenicity island 1 and 2 (SPI-1 and SPI-2) deletion on intestinal colonization and systemic dissemination in chickens

Salmonella's virulence genes are located in two regions known as Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2). SPI-1 allows the bacteria to invade the intestine, while SPI-2 is important for intracellular survival and replication, although it is also necessary for intestinal disease. The aim of this study was to evaluate the effect of the deletion of SPI-1 or SPI-2 genes on the intestinal and systemic salmonellosis using the avian model. Groups of chickens were orally infected with 1010 Colony-Forming Units (CFU) of S. Typhimurium SL1344 WT strain, as well as mutants ∆SPI-1 or ∆SPI-2. At different times post-infection, 5 chickens from each group were euthanized and examined postmortem. Cecum and liver were taken from each chicken for determination of CFU's, histopathological analysis and immunochemistry. Bacterial colonies were recovered from the liver and cecum samples infected with WT strain, while in the cultures from the organs infected with the mutant strains no colonies were recovered or were drastically affected in the ability to survive. In histopathological analysis, the WT strain produced lesions in liver and ceca, and it was detected by immunohistochemistry throughout the course of the infection. On the other hand, organs of chickens infected with ∆SPI-1 or ∆SPI-2 showed attenuated lesions and the immunohistochemistry revealed less bacteria compared to the WT strain. Taken together, our results show the importance of SPI-1 and SPI-2 genes for the complete intestinal and systemic disease in an in vivo avian model.

A systematic review on the occurrence of Salmonella in farmed Tenebrio molitor and Acheta domesticus or their derived products

Insects represent a sustainable and protein-rich food source. This new supply chain requires the study and monitoring of pathogens' presence and impact, as for other farmed animals. Among pathogens, Salmonella is of interest due to the well-established possibility for insects to harbor it. Since Acheta domesticus (cricket) and Tenebrio molitor (mealworm) are the most sold and farmed insect species, the present systematic review aimed to collect, select, and evaluate, in the available scientific literature, studies investigating the occurrence of Salmonella in these species sampled. All available studies published in peer-reviewed journals in English, French, Italian, Portuguese, German, and Spanish were considered. No time limits were imposed. We searched PUBMED, EMBASE, WEB of Science Core Collection, and Food Science and Technology Abstracts. The first date searched was May 10th, 2022; an update of the search was conducted on May 5th, 2023. The data synthesis was presented in tables reporting the number of positives on the number of total analyzed samples with other relevant characteristics of the study. The quality assessment was carried out considering relevant aspects for sampling and the method of analysis for Salmonella detection. At the end of the screening process, 10 and nine studies conducted on crickets and mealworms, respectively, were included for data extraction. The S. serovar Wandsworth and S. serovar Stanley were isolated only in one sample of ready-to-eat crickets. A second study detected OTUs related to S. enterica in cricket and mealworm powders. No studies detected Salmonella in mealworms according to cultural methods. The limitations of the present review are that few studies were retrieved and that included studies had important limitations in terms of study design as sampling was mostly based on convenience and not on a sound statistical basis. The present systematic review underlines the need to obtain reliable data about Salmonella presence in insects considering the growing market and the scaling up of existing farms. This research was funded by the Italian Ministry of Health - Ricerca Corrente IZSVe 03/21. The review protocol was published on the Systematic Reviews for Animals and Food (SYREAF) Web site (https://syreaf.org/protocols/).

A Comprehensive Review of the Common Bacterial Infections in Dairy Calves and Advanced Strategies for Health Management

Dairy farming faces a significant challenge of bacterial infections in dairy calves, which can have detrimental effects on their health and productivity. This review offers a comprehensive overview of the most prevalent bacterial infections in dairy calves, including Escherichia coli, Salmonella typhimurium, Salmonella dublin, Salmonella enterica, Clostridium perfringens, Pasteurella multocida, Listeria monocytogenes, Mycoplasma bovis, and Haemophilus somnus. These pathogens can cause various clinical signs and symptoms, leading to diarrhea, respiratory distress, septicemia, and even mortality. Factors such as management practices, environmental conditions, and herd health influence the incidence and severity of the infections. Efficient management and prevention strategies include good colostrum and nutrient feeding, early detection, appropriate treatment, hygiene practices, and supportive care. Regular health monitoring and diagnostic tests facilitate early detection and intervention. The use of antibiotics should be judicious to prevent antimicrobial resistance and supportive care such as fluid therapy and nutritional support promotes recovery. Diagnostic methods, including immunological tests, culture, polymerase chain reaction (PCR), and serology, aid in the identification of specific pathogens. This review also explores recent advancements in the diagnosis, treatment, and prevention of bacterial infections in dairy calves, providing valuable insights for dairy farmers, veterinarians, and researchers. By synthesizing pertinent scientific literature, this review contributes to the development of effective strategies aimed at mitigating the impact of bacterial infections on the health, welfare, and productivity of young calves. Moreover, more research is required to enhance the understanding of the epidemiology and characterization of bacterial infections in dairy calves.

Gut microbiome carbon and sulfur metabolisms support Salmonella during pathogen infection

Salmonella enterica serovar Typhimurium is a pervasive enteric pathogen and an ongoing global threat to public health. Ecological studies in the Salmonella impacted gut remain underrepresented in the literature, discounting the microbiome mediated interactions that may inform Salmonella physiology during colonization and infection. To understand the microbial ecology of Salmonella remodeling of the gut microbiome, here we performed multi-omics approaches on fecal microbial communities from untreated and Salmonella -infected mice. Reconstructed genomes recruited metatranscriptomic and metabolomic data providing a strain-resolved view of the expressed metabolisms of the microbiome during Salmonella infection. This data informed possible Salmonella interactions with members of the gut microbiome that were previously uncharacterized. Salmonella- induced inflammation significantly reduced the diversity of transcriptionally active members in the gut microbiome, yet increased gene expression was detected for 7 members, with Luxibacter and Ligilactobacillus being the most active. Metatranscriptomic insights from Salmonella and other persistent taxa in the inflamed microbiome further expounded the necessity for oxidative tolerance mechanisms to endure the host inflammatory responses to infection. In the inflamed gut lactate was a key metabolite, with microbiota production and consumption reported amongst transcriptionally active members. We also showed that organic sulfur sources could be converted by gut microbiota to yield inorganic sulfur pools that become oxidized in the inflamed gut, resulting in thiosulfate and tetrathionate that supports Salmonella respiration. Advancement of pathobiome understanding beyond inferences from prior amplicon-based approaches can hold promise for infection mitigation, with the active community outlined here offering intriguing organismal and metabolic therapeutic targets.

Versatile allelic replacement and self-excising integrative vectors for plasmid genome mutation and complementation

IMPORTANCE

In spite of the dissemination of multidrug-resistant plasmids among Gram-negative pathogens, including those carrying virulence genes, vector tools for studying plasmid-born genes are lacking. The allelic replacement vectors can be used to generate plasmid or chromosomal mutations including markless point mutations. This is the first report describing a self-excising integrative vector that can be used as a stable single-copy complementing tool to study medically important pathogens including in vivo studies without the need for antibiotic selection. Overall, our newly developed vectors can be applied for the assessment of the function of plasmid-encoded genes by specifically creating mutations, moving large operons between plasmids and to/from the chromosome, and complementing phenotypes associated with gene mutation. Furthermore, the vectors express chromophores for the detection of target gene modification or colony isolation, avoiding time-consuming screening procedures.

Experimental promoter identification of a foodborne pathogen Salmonella enterica subsp. enterica serovar Typhimurium with near single base-pair resolution

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common foodborne pathogen which is frequently used as the reference strain for Salmonella. Investigating the sigma factor network and protomers is crucial to understand the genomic and transcriptomic properties of the bacterium. Its promoters were identified using various methods such as dRNA-seq, ChIP-chip, or ChIP-Seq. However, validation using ChIP-exo, which exhibits higher-resolution performance compared to conventional ChIP, has not been conducted to date. In this study, using the representative strain S. Typhimurium LT2 (LT2), the ChIP-exo experiment was conducted to accurately determine the binding sites of catalytic RNA polymerase subunit RpoB and major sigma factors (RpoD, RpoN, RpoS, and RpoE) during exponential phase. Integrated with the results of RNA-Seq, promoters and sigmulons for the sigma factors and their association with RpoB have been discovered. Notably, the overlapping regions among binding sites of each alternative sigma factor were found. Furthermore, comparative analysis with Escherichia coli str. K-12 substr. MG1655 (MG1655) revealed conserved binding sites of RpoD and RpoN across different species. In the case of small RNAs (sRNAs), 50 sRNAs observed their expression during the exponential growth of LT2. Collectively, the integration of ChIP-exo and RNA-Seq enables genome-scale promoter mapping with high resolution and facilitates the characterization of binding events of alternative sigma factors, enabling a comprehensive understanding of the bacterial sigma factor network and condition-specific active promoters.

Serotype Distribution, Antimicrobial Resistance, Virulence Genes, and Genetic Diversity of Salmonella spp. Isolated from small-scale Leafy Green Vegetable Supply Chains in South Africa

Salmonella have been implicated in foodborne disease outbreaks globally and is a pressing concern in the South African small-scale sector due to inadequate hygiene standards and limited regulatory oversight, leading to a higher risk of foodborne diseases. By investigating irrigation water and leafy green vegetables produced by small-scale growers and sold through unregulated supply chains, this study was able to determine the presence, serotype distribution, virulence gene profiles, antibiotic resistance, and genetic diversity of Salmonella isolated from these sources. From 426 samples, 21 Salmonella-positive samples were identified, providing 53 Salmonella isolates. Of these, six different Salmonella serotypes and sequence types (STs) were identified, including Salmonella II 42:r: ST1208 (33.96%; n = 18), Salmonella Enteritidis: ST11 (22.64%; n = 12), Salmonella II 42:z29: ST4395 (16.98%; n = 9), Salmonella Havana: ST1524 (15.09%; n = 8), Salmonella Typhimurium: ST19 (9.43%; n = 5), and Salmonella IIIb 47:i:z: ST7890 (1.89%; n = 1). A total of 92.45% of the isolates were found to be multidrug-resistant, showing high rates of resistance to aztreonam (88.68%; n = 47), ceftazidime (86.79%; n = 46), nalidixic acid (77.36%; n = 41), cefotaxime (75.47%; n = 40), cefepime (71.70%; n = 38), and streptomycin (69.81%; n = 37). All isolates possessed the aac(6')-Iaa antimicrobial resistance gene, with a range of between 9 and 256 virulence genes. Eleven cluster patterns were observed from Enterobacterial Repetitive Intergenic Consensus sequence analyses, demonstrating high diversity among the Salmonella spp., with water and fresh produce isolates clustering, suggesting water as a potential contamination source. Plasmid replicon types were identified in 41.51% (n = 22) of the isolates, including Col(pHAD28) in Salmonella Havana (5.66%; n = 3), Col156 in Salmonella II 42:z29:- (1.89%; n = 1) and both IncFIB(S) and IncFII(S) in Salmonella Enteritidis (22.64; n = 12), Salmonella Typhimurium (9.43%; n = 5), and Salmonella Havana (1.89%; n = 1). This study highlights the presence of multidrug-resistant and multivirulent Salmonella spp. in the small-scale leafy green vegetable supply chains, underscoring the need for the development of a "fit-for-purpose" food safety management system within this system.

Transcriptional responses of cytokines, immunoglobulin A, and nitric oxide genes in 1-day-old chicks post Salmonella typhimurium infection: An experimental study

Background

Salmonella has become one of the hazards prevalent foodborne pathogens causing different diseases in chickens. However, Salmonella typhimurium (ST), a nonhost-specific serovar, is a major avian agent that causes severe disturbance in young chicken wellness.

Aim

The occurrence of Salmonella in chickens and their antimicrobial resistance were explored in this study. In addition, the immune response of 1-day-old broiler chicks, against multidrug resistant (MDR) ST infection, was also assessed at 4 and 24 hours post infection (pi) in the cecum and spleen, representing their mucosal and systemic immune responses, respectively.

Methods

A total of 375 samples from 130 diseased and apparently healthy broiler and layer chickens were randomly collected for Salmonella isolation, identification, and resistance profile evaluation, from farms and different clinical laboratories. The immune response of 1-day-old broiler chicks, Ross 308, against in-vivo ST infection was ascertained through the evaluation of heterophile phagocytosis and s expression of cytokines, immunoglobulin A and other immune-regulating genes in the cecum and spleen. Twenty-four, 1-day-old nonvaccinated broiler chicks were used and divided into two groups. The chicks in the infected group were orally inoculated with 0.5 ml of 2 × 108 colony forming units (CFU)/ml of MDR ST suspension, while those in the control group were taken nutrient broth.

Results

Seven out of 130 (5.38%) examined chickens were positive for Salmonella. All isolates (100%) were resistant to amoxicillin-clavulanic acid (AMC), cefazolin (CZ), cefoxitin (FOX), ciprofloxacin (CIP), nalidixic acid (NA), tetracycline (TE), fosfomycin (FOS), and colistin (CT) with multiple antimicrobial resistances (MARs) index range of 0.72-0.83, where none of them was resistant to meropenem (MEM). The results of immune response revealed that chicks infected with ST showed significantly different phagocytosis percentages and index values compared to controls. According to the real-time quantitative polymerase chain reaction (RT-qPCR) results, the transcription of IL-8, iNOS, IL-18, IgA, and IFN-γ for chicks infected by ST showed a significantly increased trend (p < 0.01) with increasing chicken age and was higher in the cecum than spleen compared to controls (p < 0.05) during 24 hours after infection.

Conclusion

The findings indicated a strong mucosal immune response in the chicks after the ST challenge, which reflects humoral and cellular responses. Our insight recommended the occurrence of a natural immune response stimulator at 1 day age to face the infection, and this can prevent the resistance transfer, with efficient control measures.

The quorum sensing molecule C12-HSL promotes biofilm formation and increases adrA expression in Salmonella Enteritidis under anaerobic conditions

Acyl-homoserine lactones (AHLs) are quorum-sensing signaling molecules in Gram-negative bacteria and positively regulate biofilm formation in Salmonella under specific conditions. In this study, biofilm formation in Salmonella enterica was evaluated at 28 and 37 °C, under aerobic and anaerobic conditions. Additionally, the influence of the N-dodecanoyl-DL-homoserine lactone (C12-HSL) on biofilm formation and the expression of genes related to the synthesis of structural components, regulation, and quorum sensing was assessed under anaerobiosis at 28 and 37 °C. Biofilm formation was found not to be influenced by the atmospheric conditions at 28 °C. However, it was reduced at 37 °C under anaerobiosis. C12-HSL enhanced biofilm formation at 37 °C under anaerobiosis and increased the expression of the adrA and luxS genes, suggesting an increase in c-di-GMP, a second messenger that controls essential physiological functions in bacteria. These results provide new insights into the regulation of biofilm formation in Salmonella under anaerobic conditions.

Animal and In Vitro Models as Powerful Tools to Decipher the Effects of Enteric Pathogens on the Human Gut Microbiota

Examining the interplay between intestinal pathogens and the gut microbiota is crucial to fully comprehend the pathogenic role of enteropathogens and their broader impact on human health. Valid alternatives to human studies have been introduced in laboratory practice to evaluate the effects of infectious agents on the gut microbiota, thereby exploring their translational implications in intestinal functionality and overall health. Different animal species are currently used as valuable models for intestinal infections. In addition, considering the recent advances in bioengineering, futuristic in vitro models resembling the intestinal environment are also available for this purpose. In this review, the impact of the main human enteropathogens (i.e., Clostridioides difficile, Campylobacter jejuni, diarrheagenic Escherichia coli, non-typhoidal Salmonella enterica, Shigella flexneri and Shigella sonnei, Vibrio cholerae, and Bacillus cereus) on intestinal microbial communities is summarized, with specific emphasis on results derived from investigations employing animal and in vitro models.

Antimicrobial Effects of Plant-Based Supplements on Gut Microbial Diversity in Small Ruminants

Every year in the United States, approximately 48 million people are affected by bacterial illnesses that are transmitted through food, leading to 3000 fatalities. These illnesses typically stem from food animals and their by-products, which may harbor dangerous pathogens like Salmonella enterica, Listeria monocytogenes, enterohemorrhagic Escherichia coli O157:H7, and Campylobacter jejuni. Factors that contribute to contamination include manure used as a soil amendment, exposure to polluted irrigation water, and contact with animals. To improve food safety, researchers are studying pre-slaughter intervention methods to eliminate bacterial contamination in live animals. While small ruminants are vital to global agriculture and income generation for small farms, traditional feeding practices involve supplements and antibiotics to boost performance, which contributes to antibiotic resistance. Hence, researchers are looking for friendly bacterial strains that enhance both animal and human health without impacting livestock productivity. The global trend is to minimize the use of antibiotics as feed supplements, with many countries prohibiting or limiting their use. The aim of this review is to provide a comprehensive insight on the antioxidant capabilities, therapeutic attributes, and applications of bioactive compounds derived from sweet potato tops (SPTs), rice bran (RB) and radish tops (RTs). This overview provides an insight on plant parts that are abundant in antioxidant and prebiotic effects and could be used as value-added products in animal feed and pharmaceutical applications. This review was based on previous findings that supplementation of basal diets with natural supplements represents a multifaceted intervention that will become highly important over time. By remarkably reducing the burden of foodborne pathogens, they apply to multiple species, are cheap, do not require withdrawal periods, and can be applied at any time in food animal production.