Exploring the antimicrobial efficacy of Manuka honey against multidrug-resistant and extensively drug-resistant Salmonella Typhi causing septicemia in Pakistan.

Aim: To determine the efficacy of manuka honey against multidrug-resistant (MDR) and extensively drug-resistant (XDR) clinical strains of Salmonella Typhi. Materials & methods: Clinical isolates were processed using the Bactec blood culture system, identification and antibiogram by Vitek 2 and antibiotic resistance genes through polymerase chain reaction (PCR). Microbroth dilution assays evaluated the antibacterial activity of manuka honey. Results: MDR and XDR-S. Typhi was susceptible to azithromycin. These strains carried the H58, gyrA, gyrB, blaCTX-M-15 , and blaTEM-1 genes. At 100% honey, the zone of inhibition for MDR (15-23 mm) and XDR (15-24 mm) strains. 18/50 MDR and 14/50 XDR strains inhibited at 3.125 v/v% killed at 6.25 v/v% concentration respectively. Conclusion: Manuka honey could be an alternative option for treating S. Typhi infections.

Typhoid fever is a life-threatening bacterial infection caused by the Salmonella Typhi. These bacteria are transmitted through contaminated water and food and cause fever, abdominal pain, headache, vomiting, and diarrhea mainly in children under 5. There are around 9 million people get infected with S. Typhi, with an increased death of 1,10,000 annually. Bees that collect nectar from the blossoms of the Manuka tree in Australia and New Zealand produce a type of honey known as manuka honey. This honey is famous for its antibacterial activity, and potential health benefits. Therefore, we aimed to determine its antibacterial activity against S. Typhi. Our finding shows that the commonly available antibiotics did not kill S. Typhi because their DNA was drug-resistant. After applying the manuka honey, these bacteria were killed and given a clear zone ranging from 15­24mm on the agar plate. Further analysis revealed that at low concentrations of manuka honey, 3.1% and 6.25%, most of the S. Typhi stopped growing and killed, respectively. This study suggested that manuka honey, which is affordable and readily available, could be used as a treatment option to treat infections produced by these harmful bacteria after further analysis.

An emerging assay for rapid diagnosis of live Salmonella Typhimurium by exploiting aqueous/liquid crystal interface.

The rapid and accurate identification of live pathogens with high proliferative ability is in great demand to mitigate foodborne infection outbreaks. Herein, we have developed an ultrasensitive image-based aptasensing array to directly detect live Salmonella typhimurium (S.T) cells. This method relies on the long-range orientation of surfactant-decorated liquid crystals (LCs) and the superiority of aptamers (aptST). The self-assembling of hydrophobic surfactant tails leads to a perpendicular/vertical ordered film at the aqueous/LC interface and signal-off response. The addition of aptST perturbed LCs' ordering into a planar/tilted state at the aqueous phase due to electrostatic interactions between the surfactant with the aptST, and a signal-on response. Following the conformational switch of aptST in the presence of live S. typhimurium, a relative reversing signal-off response was observed upon the target concentration. This aptasensor could promptly confirm the presence of S. typhimurium without intricate DNA-extraction or pre-enrichment stats over a linear range of 1-1.1 × 106 CFU/mL and a detection limit of 1.2 CFU/mL within ∼30 min. These results were successfully validated using molecular and culture-based methods in spiked-milk samples, with a 92.61-104.61 % recovery value. Meanwhile, the flexibility of this portable sensing platform allows for its development and adoption for the precise detection of various pathogens in food and the environment.

Oligodeoxynucleotides containing CpG motifs upregulate bactericidal activities of heterophils and enhance immunoprotection of neonatal broiler chickens against Salmonella Typhimurium septicemia.

In the past, we demonstrated that oligodeoxynucleotides containing CpG motifs (CpG-ODN) mimicking bacterial DNA, stimulate the innate immune system of neonatal broiler chickens and protect them against Escherichia coli and Salmonella Typhimurium (S. Typhimurium) septicemia. The first line of innate immune defense mechanism is formed by heterophils and plays a critical protective role against bacterial septicemia in avian species. Therefore, the objectives of this study were 1) to explore the kinetics of CpG-ODN mediated antibacterial mechanisms of heterophils following single or twice administration of CpG-ODN in neonatal broiler chickens and 2) to investigate the kinetics of the immunoprotective efficacy of single versus twice administration of CpG-ODN against S. Typhimurium septicemia. In this study, we successfully developed and optimized flow cytometry-based assays to measure phagocytosis, oxidative burst, and degranulation activity of heterophils. Birds that received CpG-ODN had significantly increased (p < 0.05) phagocytosis, oxidative burst, and degranulation activity of heterophils as early as 24 h following CpG-ODN administration. Twice administration of CpG-ODN significantly increased the phagocytosis activity of heterophils. In addition, our newly developed CD107a based flow cytometry assay demonstrated a significantly higher degranulation activity of heterophils following twice than single administration of CpG-ODN. However, the oxidative burst activity of heterophils was not significantly different between birds that received CpG-ODN only once or twice. Furthermore, delivery of CpG-ODN twice increased immunoprotection against S. Typhimurium septicemia compared to once but the difference was not statistically significant. In conclusion, we demonstrated enhanced bactericidal activity of heterophils after administration of CpG-ODN to neonatal broiler chickens. Further investigations will be required to identify other activated innate immune cells and the specific molecular pathways associated with the CpG-ODN mediated activation of heterophils.

S100a8/a9 regulated by LPS/TLR4 axis plays an important role in Salmonella-based tumor therapy and host defense.

Bacteria are ideal anticancer agents and carriers due to their unique capabilities that are convenient in genetic manipulation, tumor-specific targeting, and deep-tissue penetration. However, the specific molecular mechanisms of bacteria-mediated cancer therapy (BMCT) have not been clarified. In this study, we found that TLR4 signaling pathway is critical for Salmonella-mediated tumor targeting, tumor suppression, and liver and spleen protection. TLR4 knockout in mice decreased the levels of cytokines and chemokines, such as S100a8, S100a9, TNF-α, and IL-1ß, in tumor microenvironments (TMEs) after Salmonella treatment, which inhibited tumor cell death and nutrient release, led to reduced bacterial contents in tumors and attenuated antitumor efficacy in a negative feedback manner. Importantly, we found that S100a8 and S100a9 played a leading role in Salmonella-mediated cancer therapy (SMCT). The antitumor efficacy was abrogated and liver damage was prominent when blocked with a specific inhibitor. These findings elucidated the mechanism of Salmonella-mediated tumor targeting, suppression, and host antibacterial defense, providing insights into clinical cancer therapeutics.

Lactate promotes the biofilm-to-invasive-planktonic transition in Salmonella enterica serovar Typhimurium via the de novo purine pathway.

Salmonella enterica serovar Typhimurium (S. Typhimurium) infection triggers an inflammatory response that changes the concentration of metabolites in the gut impacting the luminal environment. Some of these environmental adjustments are conducive to S. Typhimurium growth, such as the increased concentrations of nitrate and tetrathionate or the reduced levels of Clostridia-produced butyrate. We recently demonstrated that S. Typhimurium can form biofilms within the host environment and respond to nitrate as a signaling molecule, enabling it to transition between sessile and planktonic states. To investigate whether S. Typhimurium utilizes additional metabolites to regulate its behavior, our study delved into the impact of inflammatory metabolites on biofilm formation. The results revealed that lactate, the most prevalent metabolite in the inflammatory environment, impedes biofilm development by reducing intracellular c-di-GMP levels, suppressing the expression of curli and cellulose, and increasing the expression of flagellar genes. A transcriptomic analysis determined that the expression of the de novo purine pathway increases during high lactate conditions, and a transposon mutagenesis genetic screen identified that PurA and PurG, in particular, play a significant role in the inhibition of curli expression and biofilm formation. Lactate also increases the transcription of the type III secretion system genes involved in tissue invasion. Finally, we show that the pyruvate-modulated two-component system BtsSR is activated in the presence of high lactate, which suggests that lactate-derived pyruvate activates BtsSR system after being exported from the cytosol. All these findings propose that lactate is an important inflammatory metabolite used by S. Typhimurium to transition from a biofilm to a motile state and fine-tune its virulence.IMPORTANCEWhen colonizing the gut, Salmonella enterica serovar Typhimurium (S. Typhimurium) adopts a dynamic lifestyle that alternates between a virulent planktonic state and a multicellular biofilm state. The coexistence of biofilm formers and planktonic S. Typhimurium in the gut suggests the presence of regulatory mechanisms that control planktonic-to-sessile transition. The signals triggering the transition of S. Typhimurium between these two lifestyles are not fully explored. In this work, we demonstrated that in the presence of lactate, the most dominant host-derived metabolite in the inflamed gut, there is a reduction of c-di-GMP in S. Typhimurium, which subsequently inhibits biofilm formation and induces the expression of its invasion machinery, motility genes, and de novo purine metabolic pathway genes. Furthermore, high levels of lactate activate the BtsSR two-component system. Collectively, this work presents new insights toward the comprehension of host metabolism and gut microenvironment roles in the regulation of S. Typhimurium biology during infection.

Critical role of msgA in invasive capacity and intracellular survivability of Salmonella.

Salmonella enterica serovar Typhimurium, which is a common foodborne pathogen, causes both intestinal and systemic infections in hosts. Salmonella has a complex pathogenic mechanism that involves invasive capacity and intracellular survivability, which hampers research on virulence of Salmonella. The virulence of Salmonella is primarily studied through Salmonella pathogenicity islands (SPIs). However, there are also genes outside these SPIs that significantly impact virulence. Macrophage survival gene msgA is positioned at a region independent of the SPIs and conserved in Salmonella. However, there has been limited research on msgA to date. This study aims to investigate the virulent function of msgA to deepen our understanding of Salmonella virulence. Proteomic and RT-qPCR analyses reveal that MsgA influences multiple metabolic pathways and the expression of SPIs. The depletion of msgA led to the significantly reduced invasive capacity and intracellular survivability, and thus the decreased virulence of Salmonella. In conclusion, our study suggests that MsgA is an important regulator that mainly regulates virulence. Further research into the function of MsgA will enhance the understanding of Salmonella pathogenesis and promote the application of Salmonella for medical treatment. IMPORTANCE: Salmonella enterica serovar Typhimurium is a common foodborne pathogen, it has a complex pathogenic mechanism that involves invasive capacity and intracellular survivability. The virulence of Salmonella is primarily studied through its pathogenicity islands. In contrast, virulence genes located outside the Salmonella pathogenicity islands (SPIs) have received less attention. Macrophage survival gene (MsgA) is positioned at a region independent of the SPIs and conserved in Salmonella. Our research indicates that MsgA is a novel global regulator influencing the metabolic pathways and SPIs. Further research into the function of MsgA will enhance the understanding of Salmonella pathogenesis and promote the application of Salmonella for medical treatment.

Salmonella Prevalence and antibiotic resistance profile in raw poultry meat sold in North Lebanon: Insights from the COVID-19 pandemic and economic crisis.

Salmonella-related foodborne illness is a significant public health concern, with the primary source of human infection being animal-based food products, particularly chicken meat. Lebanon is currently experiencing a dual crisis: the COVID-19 pandemic and an unprecedented economic crisis, which has resulted in substantial challenges to the public health system and food safety. This study aims to assess the prevalence and antibiotic resistance profile of Salmonella in raw poultry meat sold in North Lebanon during this dual crisis. A cross-sectional study was carried out between May 2021 and April 2022 across six different districts in North Lebanon. A total of 288 whole, unprocessed chickens were examined. The isolation and identification of Salmonella isolates were done based on cultural and biochemical properties. All isolates were subjected to antimicrobial susceptibility testing and phenotypic assays for Extended-Spectrum Beta-lactamase (ESBL) detection. The prevalence of Salmonella in raw poultry meat purchased in North Lebanon reached 18.05 % (52/288). The dry season and chilled chicken were significantly associated with an increased risk of Salmonella contamination (P < 0.05). Additionally, 34.61 % of the isolates were potential ESBL producers, and 57.69 % exhibited multidrug resistance (MDR). This study highlights the existence of MDR in chicken meat in North Lebanon, posing a potential health risk if undercooked chicken meat is consumed. This emphasizes the importance of the implementation of preventive strategies and hygienic procedures throughout the food chain to reduce the risk of Salmonella spp. contamination in chicken meats and its potential transmission to humans.

Characterization and engineering of the type 3 secretion system needle monomer from Salmonella through the construction and screening of a comprehensive mutagenesis library.

Protein production strategies in bacteria are often limited due to the need for cell lysis and complicated purification schemes. To avoid these challenges, researchers have developed bacterial strains capable of secreting heterologous protein products outside the cell, but secretion titers often remain too low for commercial applicability. Improved understanding of the link between secretion system structure and its secretory abilities can help overcome the barrier to engineering higher secretion titers. Here, we investigated this link with the PrgI protein, the monomer of the secretory channel of the type 3 secretion system (T3SS) of Salmonella enterica. Despite detailed knowledge of the PrgI needle's assembly and structure, little is known about how its structure influences its secretory capabilities. To study this, we recently constructed a comprehensive codon mutagenesis library of the PrgI protein utilizing a novel one-pot recombineering approach. We then screened this library for functional T3SS assembly and secretion titer by measuring the secretion of alkaline phosphatase using a high-throughput activity assay. This allowed us to construct a first-of-its-kind secretion fitness landscape to characterize the PrgI needle's mutability at each position as well as the mutations which lead to enhanced T3SS secretion. We discovered new design rules for building a functional T3SS as well as identified hypersecreting mutants. This work can be used to increase understanding of the T3SS's assembly and identify further targets for engineering. This work also provides a blueprint for future efforts to engineer other complex protein assemblies through the construction of fitness landscapes.IMPORTANCEProtein secretion offers a simplified alternative method for protein purification from bacterial hosts. However, the current state-of-the-art methods for protein secretion in bacteria are still hindered by low yields relative to traditional protein purification strategies. Engineers are now seeking strategies to enhance protein secretion titers from bacterial hosts, often through genetic manipulations. In this study, we demonstrate that protein engineering strategies focused on altering the secretion apparatus can be a fruitful avenue toward this goal. Specifically, this study focuses on how changes to the PrgI needle protein from the type 3 secretion system from Salmonella enterica can impact secretion titer. We demonstrate that this complex is amenable to comprehensive mutagenesis studies and that this can yield both PrgI variants with increased secretory capabilities and insight into the normal functioning of the type 3 secretion system.

Type 1 fimbria and P pili: regulatory mechanisms of the prototypical members of the chaperone-usher fimbrial family.

Adherence to both cellular and abiotic surfaces is a crucial step in the interaction of bacterial pathogens and commensals with their hosts. Bacterial surface structures known as fimbriae or pili play a fundamental role in the early colonization stages by providing specificity or tropism. Among the various fimbrial families, the chaperone-usher family has been extensively studied due to its ubiquity, diversity, and abundance. This family is named after the components that facilitate their biogenesis. Type 1 fimbria and P pilus, two chaperone-usher fimbriae associated with urinary tract infections, have been thoroughly investigated and serve as prototypes that have laid the foundations for understanding the biogenesis of this fimbrial family. Additionally, the study of the mechanisms regulating their expression has also been a subject of great interest, revealing that the regulation of the expression of the genes encoding these structures is a complex and diverse process, involving both common global regulators and those specific to each operon.

Research progress of loop-mediated isothermal amplification in the detection of Salmonella for food safety applications.

Salmonella, the prevailing zoonotic pathogen within the Enterobacteriaceae family, holds the foremost position in global bacterial poisoning incidents, thereby signifying its paramount importance in public health. Consequently, the imperative for expeditious and uncomplicated detection techniques for Salmonella in food is underscored. After more than two decades of development, loop-mediated isothermal amplification (LAMP) has emerged as a potent adjunct to the polymerase chain reaction, demonstrating significant advantages in the realm of isothermal amplification. Its growing prominence is evident in the increasing number of reports on its application in the rapid detection of Salmonella. This paper provides a systematic exposition of the technical principles and characteristics of LAMP, along with an overview of the research progress made in the rapid detection of Salmonella using LAMP and its derivatives. Additionally, the target genes reported in various levels, including Salmonella genus, species, serogroup, and serotype, are summarized, aiming to offer a valuable reference for the advancement of LAMP application in Salmonella detection. Finally, we look forward to the development direction of LAMP and expect more competitive methods to provide strong support for food safety applications.

Methods for Fixing Biofilms of Staphylococcus aureus and Salmonella enterica for Microscopic Examination.

Different methods for fixing biofilms of Staphylococcus aureus and Salmonella enterica for light and electron microscopy were compared. Paraformaldehyde fixation did not preserve biofilm integrity during dehydration; Ito-Karnovsky fixation revealed cell morphology, but did not preserve the matrix. Ruthenium red combined with aldehydes allowed the matrix to be preserved and visualized. An analysis of the ultrastructure of S. aureus and S. enterica cells in biofilms and suspensions at various fixations is presented. The ultrastructure of the biofilm matrix has been described.

Transition to Whole Genome Sequencing Surveillance: The Impact on National Outbreak Detection and Response for Listeria monocytogenes, Salmonella, Shiga Toxin-Producing Escherichia coli, and Shigella Clusters in Canada, 2015-2021.

Between 2017 and 2019, pulsed-field gel electrophoresis was replaced by whole genome sequencing (WGS) for identifying enteric disease clusters in Canada. The number and characteristics of all clusters of Listeria monocytogenes, Salmonella, Shiga toxin-producing Escherichia coli (STEC), and Shigella spp. between 2015 and 2021 were analyzed. Following the transition to WGS, an increase in the number of Salmonella, STEC, and Shigella clusters was noted, whereas the number of clusters of L. monocytogenes decreased. Unlike previous subtyping methods, WGS provided increased resolution to identify discrete clusters of Salmonella Enteritidis. This led to the identification of a number of outbreaks linked to frozen raw breaded chicken products and ultimately a change in food safety policy to reduce the number of illnesses associated with these products. Other pathogens did not experience a similar increase in the number of outbreaks detected. Although WGS did provide increased confidence in the genetic relatedness of cases and isolates, challenges remained in collecting epidemiological data to link these illnesses to a common source.

Rapid detection of ceftriaxone-resistant Salmonella by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry combined with the ratio of optical density.

BACKGROUND: The increased resistance rate of Salmonella to third-generation cephalosporins represented by ceftriaxone (CRO) may result in the failure of the empirical use of third-generation cephalosporins for the treatment of Salmonella infection in children. The present study was conducted to evaluate a novel method for the rapid detection of CRO-resistant Salmonella (CRS). METHODS: We introduced the concept of the ratio of optical density (ROD) with and without CRO and combined it with matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) to establish a new protocol for the rapid detection of CRS. RESULTS: The optimal incubation time and CRO concentration determined by the model strain test were 2 h and 8 µg/ml, respectively. We then conducted confirmatory tests on 120 clinical strains. According to the receiver operating characteristic curve analysis, the ROD cutoff value for distinguishing CRS and non-CRS strains was 0.818 [area under the curve: 1.000; 95% confidence interval: 0.970-1.000; sensitivity: 100.00%; specificity: 100%; P < 10- 3]. CONCLUSIONS: In conclusion, the protocol for the combined ROD and MALDI-TOF MS represents a rapid, accurate, and economical method for the detection of CRS.

Contamination Status and Serotypes Distribution of Salmonella in Food in Yantai City, China: A 14-Year Continuous Monitoring Study.

Salmonella is a foodborne zoonotic pathogen that threatens food safety and public health. However, few people have conducted long-term and systematic studies on Salmonella contamination in food in Yantai City. In order to investigate the situation of Salmonella contamination in food and improve the ability of early warning and control of foodborne diseases, a total of 3420 samples from 20 categories were collected from 13 monitoring points in Yantai City, from 2010 to 2023. The difference in detection rate and bacterial strain of different monitoring points, different types, and different sources of samples was compared. Of the 3420 samples, 80 were positive with a detection rate of 2.34%. Salmonella detection rates were significantly different for samples collected at different monitoring sites. Salmonella was detected only in meat and meat products and catering food, and none of the other types were detected. The detection rate of Salmonella was higher in raw animal meat and raw poultry. Samples collected at the market stage had the highest detection rate (5.81%), and there was a significant difference in detection rate between samples from different sources (χ2 = 36.93, p < 0.05). Eighty-one strains of Salmonella were detected out of 3420 samples (2 different strains were detected in 1 positive sample). The serological test identified 8 groups and 27 serotypes. The dominant serum groups were group B 30.86% (25/81), group E1 23.46% (19/81), and group D 16.05% (13/81). The main dominant serotypes were Salmonella give 17.28% (14/81), Salmonella enteritidis 16.05% (13/81), and Salmonella derby 13.58% (11/81). Meat and meat products and catering food were the main food products contaminated with Salmonella. The resulting secondary contamination is the hidden threat of foodborne diseases and should be given sufficient attention.

Ligilactobacillus salivarius XP132 with antibacterial and immunomodulatory activities inhibits horizontal and vertical transmission of Salmonella Pullorum in chickens.

Probiotics are increasingly recognized for their capacity to combat pathogenic bacteria. In this study, we isolated a strain of Ligilactobacillus salivarius XP132 from the gut microbiota of healthy chickens. This strain exhibited resistance to low pH and bile salts, auto-aggregation capabilities, and the ability to co-aggregate with pathogenic Salmonella. The in vitro antibacterial activity of Ligilactobacillus salivarius XP132 was tested using an Oxford cup antibacterial test, and the results showed that Ligilactobacillus salivarius XP132 exhibited broad-spectrum antibacterial activity, with especially strong antibacterial activity against Salmonella. In animal experiments with white feather broilers and specific-pathogens-free (SPF) chickens, we orally administered 1 × 109 CFU XP132 live bacteria per chicken per day, and detected the content of Salmonella in the liver, spleen, intestinal contents, and eggs of the chickens by RT-qPCR. Oral administration of Lactobacillus salivarius XP132 group significantly reduced the levels of Salmonella in chicken liver, spleen, intestinal contents and eggs, and the oral administration of Ligilactobacillus salivarius XP132 significantly inhibited the horizontal and vertical transmission of Salmonella in SPF chickens and white-feathered broilers. After oral administration of XP132, the production of chicken serum anti-infective cytokine IFN-γ was also significantly up-regulated, thereby enhancing the host's ability to resist infection. In addition, the production of various serum inflammatory cytokines, including IL-1ß, IL-6, IL-8, and TNF-α, was down-regulated, leading to significant amelioration of the inflammatory response induced by S. Pullorum in chickens. These findings suggest that Ligilactobacillus salivarius XP132 possesses potent antibacterial and immunomodulatory properties that effectively prevent both horizontal and vertical transmission of Salmonella Pullorum, highlighting its potential as a valuable tool for the prevention and control of Salmonella disease.

Dietary supplementation with a novel acidifier sodium diformate improves growth performance by increasing growth-related hormones levels and prevents Salmonella enterica serovar Pullorum infection in chickens.

Since the use of antibiotics as growth promoters in animal feed has been restricted or banned in several countries, finding suitable alternatives is crucial for maintaining animal health. In this study, a novel formate acidifier named sodium diformate (NaDF) was synthesized, and the effects on growth performance and the prevention effects against Salmonella enterica serovar Pullorum infections in chickens were assessed. In broilers, NaDF supplementation improved growth performance, as evidenced by increased body weights and reduced feed conversion ratios. At 38 days of age, NaDF supplementation increased the levels of growth-hormone and ghrelin in the serum, lowered pH values in the gut, improved duodenal morphology, as shown by increased villus length/crypt depth ratios. NaDF also modulated the abundance of beneficial and harmful bacteria without changing the general microbiota diversity and short-chain fatty acids levels, which would be beneficial for maintaining gut homeostasis during its use. NaDF exhibited a broad spectrum of antibacterial activity in vitro. Supplementation with NaDF effectively decreased S. Pullorum colonization in the cecum, liver and spleen in chickens, and mitigated pathological changes in the tissues. Therefore, as a novel acidifier, NaDF can improve chicken growth performance by increasing growth-related hormones levels while maintaining the diversity of gut microbiota, and also resist intestinal bacterial infection. These results provided evidences for the application of NaDF as an effective and safe animal feed in poultry farming.

Presence of integrons and their correlation with multidrug resistance in Salmonella enterica serovar Typhimurium: Exploratory systematic review / Presencia de integrones y su correlación con la multirresistencia en Salmonella enterica serovar Typhimurium: revisión sistemática exploratoria.

In Salmonella enterica serovar Typhimurium (Typhimurium), multidrug resistance is associated with integrons carrying resistance genes dispersed by mobile genetic elements. This exploratory systematic review sought to identify integron types and their resistance genes in multidrug resistance Typhimurium isolates. We used Medline, PubMed, SciELO, ScienceDirect, Redalyc, and Google Scholar as motor searchers for articles in Spanish or English published between 2012 and 2020, including the keywords "integrons", "antibiotic resistance", and "Salmonella Typhimurium". We included 38 articles reporting multidrug resistance up to five antibiotic families. Class 1 integrons with aadA2 and blaPSE-1 gene cassettes were predominant, some probably related to the Salmonella genomic island 1. We did not find studies detailing class 1 and 2 integrons in the same isolate, nor class 3 integrons reported. The presence of integrons largely explains the resistance profiles found in isolates from different sources in 15 countries.

La multirresistencia a los antibióticos en Salmonella enterica serovar Typhimurium (Typhimurium) se asocia con integrones que portan genes de resistencia y que son dispersados por elementos genéticos móviles. En esta revisión sistemática exploratoria, se buscó identificar los tipos de integrones y sus genes de resistencia en aislamientos de Typhimurium multirresistentes a antibióticos. Se realizó una búsqueda de artículos en Medline, PubMed, SciELO, ScienceDirect, Redalyc y Google Académico, publicados entre el 2012 y el 2020, en español o inglés, con las palabras claves: "integrons", "antibiotic resistance" y "Salmonella Typhimurium". En el análisis se incluyeron 38 artículos que reportaron multirresistencia a cinco familias de antibióticos. Los integrones de clase 1 con casetes de genes aadA2 y blaPSE-1 fueron los predominantes, algunos probablemente relacionados con la isla genómica de Salmonella 1. No se encontraron integrones de clase 1 y 2 en un mismo aislamiento, ni se reportaron integrones de clase 3. La presencia de integrones explica en gran medida los perfiles de resistencia encontrados en aislamientos de diferentes fuentes de 15 países.

Molecular detection of avian pathogens in poultry red mite (Dermanyssus gallinae) in Algerian layer farms as a potential predictive tool.

The poultry red mite Dermanyssus gallinae is a hematophagous ectoparasite of layer hens. Infestations with poultry red mites pose an increasing threat to the egg production industry, causing serious problems to animal health and welfare, directly or indirectly as a vector of several infectious agents. In this study, we aimed to investigate common avian pathogens in mites. The mite samples were collected from 58 poultry farms in 7 regions accounting for more than 70 % of the national egg production in Algeria. The presence of 13 avian pathogens was detected using DNA and RNA samples from mites collected. Results revealed significant associations between PRM and potential pathogens such as Escherichia coli, Salmonella enterica, fowlpox virus, and gallid herpesvirus 1. Pathogen detection in Dermanyssus gallinae could serve as an early diagnostic or a risk analysis tool for infectious diseases in poultry farms, facilitating effective disease management strategies. Despite further research being necessary to address uncertainties, such a strategy could be used to enhance the integrated management of poultry health.

Salmonella infection impacts host proteome thermal stability.

Intracellular bacterial pathogens hijack the protein machinery of infected host cells to evade their defenses and cultivate a favorable intracellular niche. The intracellular pathogen Salmonella enterica subsp. Typhimurium (STm) achieves this by injecting a cocktail of effector proteins into host cells that modify the activity of target host proteins. Yet, proteome-wide approaches to systematically map changes in host protein function during infection have remained challenging. Here we adapted a functional proteomics approach - Thermal-Proteome Profiling (TPP) - to systematically assess proteome-wide changes in host protein abundance and thermal stability throughout an STm infection cycle. By comparing macrophages treated with live or heat-killed STm, we observed that most host protein abundance changes occur independently of STm viability. In contrast, a large portion of host protein thermal stability changes were specific to infection with live STm. This included pronounced thermal stability changes in proteins linked to mitochondrial function (Acod1/Irg1, Cox6c, Samm50, Vdac1, and mitochondrial respiratory chain complex proteins), as well as the interferon-inducible protein with tetratricopeptide repeats, Ifit1. Integration of our TPP data with a publicly available STm-host protein-protein interaction database led us to discover that the secreted STm effector kinase, SteC, thermally destabilizes and phosphorylates the ribosomal preservation factor Serbp1. In summary, this work emphasizes the utility of measuring protein thermal stability during infection to accelerate the discovery of novel molecular interactions at the host-pathogen interface.

Quantitative method for measuring the proportion of bacterial cells expressing phase 1 or 2 of flagellin of Salmonella enterica serovar typhimurium.

Salmonella enterica subsp. enterica is a major pathogen that causes zoonotic foodborne diseases worldwide. Some Salmonella serovars possess two antigenic phases for flagellin: phase 1 and 2. In Salmonella enterica serovar Typhimurium (S. typhimurium), the flagellin is antigenically divided into "Hi" as phase 1 and "H1 or H2" as phase 2. Flagellin phase variation is regulated by inversion of hin gene. We focused on the inversion of hin and developed a real-time PCR system to quantitatively measure the proportion of bacterial cells expressing each phase of flagellin. In this study, we demonstrated that our newly developed real-time PCR system shows high quantitative accuracy and aligns with flagellin expression status. Furthermore, the newly developed real-time PCR system was applicable to various S. typhimurium laboratory and field strains. This newly developed real-time PCR system has the potential to become a powerful tool for analyzing flagellin phase variation.