Complications and mortality of non-typhoidal salmonella invasive disease: a global systematic review and meta-analysis

Genomic and resistome analysis of Salmonella enterica isolates from retail markets in Yichun city, China

Nontyphoidal Salmonella (NTS) causes global outbreaks of foodborne disease. The main source of Salmonella for humans is animal-borne foods; however, the monitoring of Salmonella in the food chain via genomic platforms was limited in China. This study evaluated the prevalence, resistome, and virulome diversity of Salmonella strains identified from pork, retail environment, aquatic products, and poultry eggs of retail markets in Yichun city, Jiangxi province. The overall incidence of Salmonella was 9.4 %, with a higher contamination rate observed in pork at 13.5 %, followed by the retail environment at 7.69 %. The genomic analysis of the isolates revealed a total of fifteen distinct serovars, with serovar Enteritidis being the most prevalent (64.3 %). The phenotypic resistance analysis conducted by the broth microdilution method, revealed that 81.12 % of the isolates exhibited multidrug resistance (MDR), with high resistance to trimethoprim/sulphonamides (100 %), followed by tetracycline (99.3 %) and streptomycin (99.3 %). Genotypic analysis of antimicrobial resistance identified 80 antimicrobial-resistant genes (ARGs), with mdf(A), aph(3')-Ib, tet(A), dfrA12, floR, bla TEM-1B , qnrS3, and sul2, conferring resistance to different antimicrobial classes, being the predominant ARGs. Additionally, forty ESBL genes, particularly critical genes such as bla CTX-M and bla NDM-1, were also identified in Salmonella isolates. The IncR, IncFIB (K), and IncX1 plasmid replicons were widely prevalent and served as significant reservoirs of horizontally acquired foreign genes. Moreover, key virulence genes such as cdtB, lpf and sef were also detected, in addition to Salmonella pathogenicity islands SPI-1 and SPI-2. This study reveals the prevalence of multidrug-resistant and virulent strains of Salmonella serovars in the markets of Yichuan city, posing a risk of human infections. The gained knowledge provided essential baseline information that may be utilized for regular tracking of MDR Salmonella transmission in the food chain to minimize potential future outbreaks.

Landscape analysis of invasive non-typhoidal salmonella (iNTS) disease and iNTS vaccine use case and demand: Report of a WHO expert consultation

Invasive disease caused by non-typhoidal Salmonella serovars (iNTS) occurs with increased risk in the presence of other comorbidities such as malaria, HIV, malnutrition, anaemia and sickle cell disease. While infection with non-typhoidal (NTS) serovars often results in self-limited enterocolitis in high-income settings, in sub-Saharan Africa (SSA) where these risk-comorbidities are common, an invasive (iNTS) disease phenotype is seen, associated with up to 20 % case-fatality ratio, and antimicrobial resistance is both significant and growing. The need to evaluate the potential public health value of vaccines against iNTS disease is increasingly being recognized, and several candidate vaccines are in early development. A better understanding of the global burden and epidemiology of iNTS disease, as well as the potential public health and socio-economic benefits that iNTS vaccines may offer is fundamental to support and justify the investments in vaccine development. In addition, the pathways for licensure, policy recommendations and eventual vaccine prioritization and use in low- and middle-income countries (LMICs) need to be defined. Here, we report on the proceedings of an expert consultation held on 29 November - 1 December 2021 as part of an overall project to develop a Full Value of Vaccines Assessment (FVVA) for iNTS vaccines and in addition to more recent iNTS vaccine developments. Experts at the consultation reviewed the current evidence on iNTS disease and discussed knowledge gaps to be addressed to accelerate vaccine development, licensure and introduction, as well as LMIC perspectives on potential iNTS vaccine use and demand. The learnings from this consultation are critical inputs to inform remaining work under the iNTS FVVA project.

Epidemiology of Nontyphoidal Salmonella Infections in Korean Children and Genetic Factors Associated with Extra-intestinal Invasion: A Whole-genome Sequencing Analysis

Background

Understanding the virulence and pathogenicity of invasive nontyphoidal Salmonella (iNTS) in children may support timely treatment and enable closer monitoring of chronic infections. iNTS epidemiology in Asia remains inadequately described. We analyzed the genetic diversity and virulence genes associated with extra-intestinal invasion in Korean children.

Methods

Salmonella isolates from children <18 yrs of age diagnosed with moderate-to-severe salmonellosis between January 2019 and December 2021 were subjected to antibiotic susceptibility testing and whole-genome sequencing.

Results

In total, 58 cases were included. We identified 20 serotypes, the most prevalent being Salmonella Enteritidis (N=21), followed by Infantis (N=6), I 4,[5],12:i:- (N=5), and Bareilly (N=5). Extra-intestinal invasion occurred in 12 (20.7%) cases involving Salmonella Oranienburg (2/2), Give (1/1), Javiana (1/1), Paratyphi B var. L(+) tartrate+ (1/1), Schwarzengrund (1/1), Singapore (1/1), Montevideo (1/2), Saintpaul (1/2), I 4:b:- (1/2), Infantis (1/6), and Enteritidis (1/21). While the numbers of total virulence genes and genes belonging to major virulence categories did not significantly differ between iNTS and non-iNTS, several genetic factors, including Salmonella pathogenicity island (SPI)-1 (P =0.039), SPI-2 (P =0.020), SPI-5 (P =0.014), SPI-13 (P =0.010), cytolethal distending toxin-related genes (P =1.4×10-4), fepC (P =0.021), and tcpC (P =0.040) were more frequent in invasive isolates.

Conclusions

Salmonella Enteritidis-ST11 predominated in infections among Korean children, but invasive isolates were rare. Early detection of genetic factors associated with extra-intestinal invasion will be helpful for prompt and appropriate treatment.

Antibiotic-recalcitrant Salmonella during infection

Antibiotic-recalcitrant infections, defined as the prolonged carriage of pathogenic bacteria even in the presence of antibiotics, are often caused by bacteria that are genetically susceptible to the drug. These recalcitrant bacteria fail to proliferate in the presence of antibiotics but remain viable such that they may recolonize their niche following antibiotic withdrawal. Significant progress has been made in our understanding of antibiotic-recalcitrant Salmonella, which are thought to be the source of infection relapse. In recent years, it has been shown that recalcitrant bacteria manipulate host immune defences and could directly contribute to the spread of antimicrobial resistance. In this Review, we provide an overview of what is currently known about the antibiotic recalcitrance of Salmonella during infection and highlight knowledge gaps requiring additional research in the future.

Fasting-induced ketogenesis sensitizes bacteria to antibiotic treatment

Fasting metabolism is a commonly observed motivational response to acute infections and is conceptualized as being beneficial for host survival. Here, we show that fasting potentiates antibiotic treatment for murine sepsis caused by Salmonella Typhimurium, Klebsiella pneumoniae, and Enterobacter cloacae, resulting in increased bacterial clearance and improved host immune responses and survival. This effect is mediated by fasting-induced ketogenesis and could be alternatively implemented by combination therapy with antibiotics and ketone bodies. We show that the ketone body acetoacetate is an effector that sensitizes bacteria to antibiotic treatment by increasing antibiotic lethality and outer and inner membrane permeability. Our results demonstrate that acetoacetate depletes bacterial amino acids, particularly positively charged amino acids and putrescine, leading to cell membrane malfunctions and redox-related lethality. This study reveals an unrecognized role of ketogenesis in antibiotic treatment and a potential ketone body-based treatment strategy for bacterial sepsis.

The global, regional, and national burden of Invasive Non-typhoidal Salmonella (iNTS): An analysis from the Global Burden of Disease Study 1990-2021

OBJECTIVES

Invasive Non-typhoidal Salmonella (iNTS) can cause serious, life-threatening, and invasive infections, posing great challenges to public health. We aimed to systematically review the burden of iNTS disease based on Global Burden of Diseases (GBD) 2021.

METHODS

We extracted data for the incidence, death, and disability-adjusted life-years (DALYs) associated with iNTS from GBD 2021, providing an overview of its epidemiology while examining trends from 1990 to 2021. Additionally, we decomposed changes of iNTS-related burden, and quantified cross-country inequalities.

RESULTS

GBD 2021 estimated 509976(95%UI,413361 to 606167) incident cases of iNTS worldwide in 2021, with the most cases and highest age-standardized rate (ASR) in Western Sub-Saharan Africa. The low SDI region had the most cases of iNTS in 2021. The incidence and DALYs rates were highest in the Low SDI region. Among all age groups, the incidence, death, and DALYs rate of iNTS were primarily concentrated among the following age groups: <1 year, 1-4 years, 5-9 years, 10-14 years, and 15-19 years. The highest rates were observed in the <1-year group. The results of joinpoint regression analysis revealed that the global burden of iNTS increased overall from 1990 to 2005, followed by notable decrease from 2005 to 2021 at varying rates. Decomposition analysis found that population growth (103.93%) and epidemiological change (48.34%) were responsible for motivating the changes in iNTS global burden. Cross-country inequality analysis revealed that the SDI-related inequalities were moderated from 1990 to 2021.

CONCLUSIONS

The global burden of iNTS is still high, and the distribution patterns vary across different countries and territories. The global burden of iNTS was primarily noteworthy among children and adolescents, with the highest burden among infants. The changes in the iNTS burden were primarily driven by population growth and epidemic transition. Despite varying iNTS burdens across different SDI regions, SDI-related inequalities across countries became moderated gradually over time. This study reported the global disease burden and temporal trends of iNTS disease, and underscores the need for age- and region-specific strategies to mitigate the corresponding global burden.

Transmission of a plasmid harboring NDM-1 gene between Salmonella Typhimurium and Escherichia coli strains in an infant

BACKGROUND

NDM-1 has been frequently identified in Enterobacteriaceae strains from clinical samples, but its occurrence in Salmonella Typhimurium (S. Typhimurium) is uncommon. Moreover, reports on the transmission of a plasmid harboring NDM-1 between different species in clinical samples are rare.

METHODS

Two S. Typhimurium strains and an Escherichia coli (E. coli) strain were isolated from a 14-month-old infant presenting with diarrhea. The resistance phenotypes were determined using the VITEK 2 Compact System. Genomic DNA was extracted from the isolated strains and whole genome sequencing was performed. The transmissibility of plasmids was validated by a conjugation experiment.

RESULTS

The subsequently isolated S. Typhimurium and E. coli strains exhibited resistance to imipenem, and whole genomic analysis revealed that each strain harbored a plasmid harboring NDM-1 and Qnrs1 genes. The two plasmids were nearly identical based on their sequences and could transfer to recipient strains. A genomic region containing several genes encoding phosphoribosylanthranilate isomerase, bleomycin binding protein, subclass B1 metallo-beta-lactamase, and IS30-like element ISAba125 family transposase was surrounded by the two flanking IS26 elements.

CONCLUSION

The transfer of plasmid harboring NDM-1 between S. Typhimurium and E. coli strains within patients highlights the potential for widespread transmission between different species. Continuous monitoring these strains may be important for preventing extensive transmission of resistance genes.

Global burden, subtype, risk factors and etiological analysis of enteric infections from 1990-2021: population based study

Background

Enteric infections represent a prevalent global health issue and contribute significantly to the global disease burden. This study aims to investigate the patterns and trends of enteric infections from 1990 to 2021, providing valuable insights for health policy formulation, medical resource allocation, and the optimization of patient management plans.

Methods

We analyzed the Global Burden of Disease (GBD) 2021 for 21 regions and 204 countries to understand better the health burden using prevalence, incidence, mortality, and disability-adjusted life years (DALYs), subtype, risk factors, and etiology. We tested correlations with the Socio-demographic Index (SDI), and using decomposition analysis to dissect the reasons behind changes in epidemiological indicators of the disease.

Results

In 2021, the age-standardized rates of prevalence, incidence, deaths, and DALYs per 100,000 population for enteric infections were 879.58, 577.21, 17.83, and 1020.15, respectively. Compared to 1990, these rates exhibited -0.18, -0.12, -0.73, and -0.72 changes. Gender and age analyses revealed a higher burden among females, those under 15 years old, and the elderly. Regions with low SDI had higher epidemiological indicators. The burden of Typhoid fever declines in high-development regions. Unsafe water sources were identified as the primary risk factor globally in both 1990 and 2021. Rotavirus was the leading cause of deaths and DALYs.

Conclusion

This study highlights the complex epidemiological landscape of enteric infections, revealing variations in burden, risk factors, and etiological characteristics across age, gender, and geographical regions. It underscores the urgent need for healthcare professionals and policymakers to develop innovative prevention and healthcare strategies based on the current and evolving burden of enteric infections, to alleviate the global disease burden.

An Intriguing Case of Non-typhoidal Salmonella Presenting as Bacteremia and Bilateral Cellulitis in a Diabetic Patient

Non-typhoidal Salmonella typically presents acutely with gastrointestinal disease/illness. These infections infrequently manifest outside the intestines, often due to bacterial translocation from the gut. However, it is exceedingly rare for it to present as cellulitis, especially in a bilateral distribution. A 35-year-old male with a past medical history of diffuse adiposity, essential hypertension, peripheral neuropathy, and depression presented to the emergency department (ED) for evaluation of sudden onset bilateral lower extremity swelling, pain, and redness. The patient first noted these symptoms upon awakening two days prior, accompanied by night sweats. He mentioned having burned his right medial lower leg on a motorcycle exhaust pipe a week earlier but reported appropriate healing of the burn. Of note, the patient owned a corn snake, a potential vector for Salmonella, and was diagnosed with diabetes during this admission. He was ultimately found to have diffuse cellulitis of his bilateral lower extremities, with subsequent blood cultures yielding a diagnosis of bacteremia secondary to salmonellosis.

Differential infection dynamics in mononuclear and polymorphonuclear cells during Salmonella Typhimurium infection and in vitro exposure to diazoxon

S. Typhimurium bacteria cause one of the most recurrent gastrointestinal diseases worldwide. This bacterium can settle in the gastrointestinal tract and internalize into different cellular strains, causing the formation of cellular reservoirs that subsequently lead to systemic dissemination. Exogenous factors such as pesticide exposure can also cause immunological alterations, increasing susceptibility to bacterial infection. The present work evaluated the infection capacity of Salmonella Typhimurium, during a short period (1 h) on mononuclear and polymorphonuclear cells previously exposed to diazoxon (1 h, during 4 h). Mononuclear cells were infected more frequently and in greater magnitude than polymorphonuclear cells. However, when actin polymerization and the release of reactive oxygen species (ROS) were analyzed, polymorphonuclear cells showed increased activity. These processes were evidenced by conformational changes during infection. This suggests differential dynamics of S. Typhimurium infection in mononuclear and polymorphonuclear cells previously exposed to diazoxon.

Electropositive Magnetic Fluorescent Nanoprobe-Mediated Immunochromatographic Assay for the Ultrasensitive and Simultaneous Detection of Bacteria

Immunochromatographic assays (ICAs) provide simple and rapid strategies for bacterial diagnosis but still suffer from the problems of low sensitivity and high dependency on paired antibodies. Herein, the broad-spectrum capture and detection capability of the antibody-free electropositive nanoprobe are clarified for bacteria for the first time and an ultrasensitive fluorescent ICA platform is constructed for the simultaneous diagnosis of multiple pathogens. A magnetic multilayer quantum dot nanocomposite with an amino-embedded SiO2 shell (MagMQD@Si+) is designed to enrich bacteria from solutions effectively, offer high luminescence, and reduce background signals on test strips, thus greatly improving the sensitivity and stability of ICA technique for pathogen. The superior performance of the MagMQD@Si+-based ICA through the multiplex detection of three common pathogens is demonstrated, namely, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Salmonella typhimurium, showing that this ICA possesses high sensitivity (8-40 cells mL-1), good reproducibility (relative standard deviation <5.4%), and high specificity for the three target bacteria. The clinical utility of the proposed method is verified through the detection of 30 real sputum samples from patients with bacterial respiratory infections, revealing that the MagMQD@Si+-based ICA has massive potential as a powerful inspection tool for the rapid, sensitive, and ultrasensitive diagnosis of bacterial infections. [Correction added on 29 January 2025, after first online publication: Streptococcus typhi was corrected to Salmonella typhimurium.].

Characterization of non-typhoidal Salmonella reveals the highly prevalent mcr-1-positive S. 1,4,[5],12:i:- within eggs are derived from chickens

Salmonella is one of the most common foodborne pathogens. Antimicrobial-resistant Salmonella isolates, especially those resistant to colistin, pose a significant threat to public health worldwide. However, data about the prevalence of mcr-positive Salmonella in animals was few and the dissemination of mcr-positive Salmonella from animals to food, especially eggs, has not been fully addressed. The role of houseflies in the Salmonella transmission has also not been clarified. Here, we analyzed the prevalence and resistance characteristics of mcr-positive Salmonella in 1707 samples of animals (commercial laying hens, broilers, waterfowls and swine), eggs and flies from 23 farms in four cities of China between July 2021 and October 2022. Pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS) analyses of Salmonella from different sources were further performed. Among animals, waterfowls had the highest isolation rate of Salmonella (18.1 %, 35/193), followed by swine (6.1 %, 23/377), laying hens (4.2 %, 21/505) and broilers (1.4 %, 7/489). Two of the 53 flies (3.8 %) carried Salmonella. The detection rate of Salmonella in eggs from farms was 26.7 %. All mcr-1-positive Salmonella isolates were S. 1,4,[5],12:i:- and were only found in hens (0.2 %) and eggs (11.1 %). PFGE and WGS analyses showed that the mcr-1-positive S. 1,4,[5],12:i:- from commercial laying hens and eggs in the same farm had no single nucleotide polymorphism (SNP) variation, indicating that the mcr-1-positive S. 1,4,[5],12:i:- in eggs were derived from hens. The phylogenomic analysis also showed that the mcr-1-positive S. 1,4,[5],12:i:- isolates from hens and eggs were closely related to previously reported mcr-1-positive Salmonella from human in China, further confirming that such mcr-1-positive Salmonella in animals could transmit to humans via the food chain. Furthermore, the blaCTX-M-1G-positive S. Kentucky isolates from broiler and flies in the same farm had a limited number of variations (5-7 SNPs), proving the clonal transmission of Salmonella between broilers and flies. The S. Kentucky isolates carrying blaCTX-M-1G from broilers were also closely related to the S. Kentucky isolates from chicken meats and humans. Our findings suggest that Salmonella including those carrying mcr-1 in animals could transmit to eggs/meats and potentially trigger human infections. The houseflies can play an important role in the Salmonella transmission within farms. Salmonella carrying mcr in animals and animal products should be monitored regularly and control measures are urgently needed to reduce the dissemination of such pathogens.

Evaluation of multi-drug resistance, virulence factors, and antimicrobial resistance genes of non-typhoidal Salmonella isolated from ruminants as a potential human health threat in Razavi Khorasan, northeastern Iran

Non-typhoidal Salmonella (NTS) is a significant foodborne pathogen that poses a threat to human health by causing infections and potentially acquiring antibiotic resistance. We evaluated thirty-five Salmonella serovars previously isolated from cattle, sheep, goats, and their retail meat in Razavi Khorasan Province, Iran. The isolates were confirmed with Salmonella polyvalent antiserum. Furthermore, PCR was used to identify the Salmonella Enteritidis, Salmonella Typhimurium, and the host-adapted serovars Salmonella Dublin and Salmonella Abortusovis. Additionally, the antimicrobial susceptibility of the serovars was evaluated using the disk diffusion method. Subsequently, the occurrence of antimicrobial resistance genes and virulence factors was evaluated using the PCR technique. Molecular typing revealed that 20 % of the isolates were S. Typhimurium, 11.4 % were S. Dublin, 8.6 % were S. Enteritidis, 5.7 % were S. Abortusovis, and 54.3 % (19 isolates) were classified as non-typed serovars. Salmonella isolates showed high susceptibility to ciprofloxacin (91.4 %), colistin (88.6 %), gentamicin (88.6 %), and cefotaxime (85.7 %) while exhibiting high resistance to others such as ampicillin (88.6 %), streptomycin (74.3 %), and tetracycline (51.4 %). The most prevalent resistance genes in non-typhoidal Salmonella (NTS) are blaTEM (91.4 %), sul1 (65.7 %), and aadA (54.3 %). Additionally, twenty-five isolates (71.4 %) showed multi-drug resistance profiles. The most frequent virulence genes are stn (100 %), iroN (100 %), and pefA (42.9 %). The current study has revealed that Salmonella serovars isolated from sheep and goats, like those from cattle, exhibit multi-drug resistance and harbor antimicrobial resistance genes. Additionally, they possess diverse virulence factors that can threaten human health by spreading diseases and developing drug resistance, leading to antibiotic treatment failure.

Identifying key weather factors influencing human salmonellosis: A conditional incidence analysis in England, Wales, and the Netherlands

OBJECTIVES

This study aimed to improve the understanding of seasonal incidence pattern observed in salmonellosis by identifying the most influential weather factors, characterising the nature of this association, and assessing whether it is geographically restricted or generalisable to other locations.

METHODS

A novel statistical model was employed to estimate the incidence of salmonellosis conditional to various combinations of three simultaneous weather factors from 14 available. The analysis utilised daily salmonellosis cases reported from 2000 to 2016 along with detailed spatial and temporal weather data from England and Wales, and the Netherlands.

RESULTS

The incidence simulated from weather data effectively reproduced empirical incidence patterns in both countries. Key weather factors associated with increased salmonellosis cases, regardless of geographical location, included air temperature (>10 ⁰C), relative humidity, reduced precipitation, dewpoint temperature (7-10 ⁰C), and longer day lengths (12-15 h). Other weather factors, such as air pressure, wind speed, temperature amplitude, and sunshine duration, showed limited or no association with the empirical data. The model was suitable for the Netherlands, despite a difference in case ascertainment.

CONCLUSIONS

The conditional incidence is a simple and transparent method readily applicable to other countries and weather scenarios that provides a detailed description of salmonellosis cases conditional on local weather factors.

Effectiveness of iNTS vaccination in sub-Saharan Africa

Invasive non-Typhoidal Salmonella (iNTS) is one of the leading causes of blood stream infections in Sub-Saharan Africa, especially among children. iNTS can be difficult to diagnose, particularly in areas where malaria is endemic, and difficult to treat, partly because of the emergence of antibiotic resistance. We developed a mathematical model to evaluate the impact of a vaccine for iNTS in 49 countries of sub-Saharan Africa. Without vaccination we estimate 9.2 million new iNTS cases among children below 5 years old in these 49 countries from 2022 to 2038, 6.2 million of which between 2028 and 2038. The introduction of a [Formula: see text] ([Formula: see text]) efficacy vaccine in 2028 would prevent 2.6 (2.9) million of these new infections. We provide the country-specific impact of a iNTS vaccine considering the different age structures and vaccine coverage levels.

Developing a clinical prediction model to modify empirical antibiotics for non-typhoidal Salmonella bloodstream infection in children under-five in the Democratic Republic of Congo

BACKGROUND

Non-typhoidal Salmonella (NTS) frequently cause bloodstream infection in children under-five in sub-Saharan Africa, particularly in malaria-endemic areas. Due to increasing drug resistance, NTS are often not covered by standard-of-care empirical antibiotics for severe febrile illness. We developed a clinical prediction model to orient the choice of empirical antibiotics (standard-of-care versus alternative antibiotics) for children admitted to hospital in settings with high proportions of drug-resistant NTS.

METHODS

Data were collected during a prospective cohort study in children (> 28 days-< 5 years) admitted with severe febrile illness to Kisantu district hospital, DR Congo. The outcome variable was blood culture confirmed NTS bloodstream infection; the comparison group were children without NTS bloodstream infection. Predictors were selected a priori based on systematic literature review. The prediction model was developed with multivariable logistic regression; a simplified scoring system was derived. Internal validation to estimate optimism-corrected performance was performed using bootstrapping and net benefits were calculated to evaluate clinical usefulness.

RESULTS

NTS bloodstream infection was diagnosed in 12.7% (295/2327) of enrolled children. The area under the curve was 0.79 (95%CI: 0.76-0.82) for the prediction model, and 0.78 (0.85-0.80) for the scoring system. The estimated calibration slopes were 0.95 (model) and 0.91 (scoring system). At a decision threshold of 20% NTS risk, the prediction model and scoring system had 57% and 53% sensitivity, and 85% specificity. The net benefit for decisions thresholds < 30% ranged from 2.4 to 3.9 per 100 children.

CONCLUSION

The model predicts NTS bloodstream infection and can support the choice of empiric antibiotics to include coverage of drug-resistant NTS, in particular for decision thresholds < 30%. External validation studies are needed to investigate generalizability.

TRIAL REGISTRATION

DeNTS study, clinicaltrials.gov: NCT04473768 (registration 16/07/2020) and TreNTS study, clinicaltrials.gov: NCT04850677 (registration 20/04/2021).

Genomic insights into a clinical Salmonella Typhimurium isolate carrying plasmid-mediated blaNDM-5

OBJECTIVE

Highly carbapenem-resistant Salmonella has emerged worldwide in recent years and is largely associated with the multiform transmission of resistance genes, which poses a huge challenge in clinical practice. Our study delves into the resistance mechanisms and epidemiology of blaNDM-carrying plasmids.

METHODS

Whole-genome sequencing was utilised to analyse the molecular characteristics and antimicrobial resistance mechanisms of Salmonella isolates recovered from the faeces of a paediatric patient at the Children's Hospital of Nanjing Medical University. Moreover, we conducted an epidemiologic analysis and focused on studying the mechanisms of plasmid-mediated blaNDM transmission, incorporating genomes deposited in the NCBI Pathogen Detection database.

RESULTS

The clinical isolate 23S9 belonged to serovar Typhimurium, antigenic profile 4:i:-, ST34, and carried pNDM_23S9 harbouring several antimicrobial resistance genes, including aac(6')-Ib-cr6, OXA-1, catB3, arr-3, qacEdeltal and blaNDM. Comparative analysis revealed that blaNDM-5 can exist in different plasmids of different isolates, proving its transmission through plasmids. Furthermore, blaNDM-carrying isolates are mostly resistant to beta-lactams, aminoglycosides, sulphonamide, macrolides, and trimethoprim.

CONCLUSIONS

These findings provided thorough and intuitive insights into the intercontinental spread of blaNDM-carrying Salmonella. Ongoing surveillance is essential for effectively monitoring the worldwide dissemination of this high-risk carbapenem-resistant Salmonella.

Foodborne Infections and Salmonella: Current Primary Prevention Tools and Future Perspectives

Salmonella is considered the major zoonotic and foodborne pathogen responsible for human infections. It includes the serovars causing typhoid fever (S. typhi and S. paratyphi) and the non-typhoidal salmonella (NTS) serovars (S. enteritidis and S. typhimurium), causing enteric infections known as "Salmonellosis". NTS represents a major public health burden worldwide. The consumption of S. enteritidis-contaminated animal foods is the main source of this disease in humans, and eradicating bacteria from animals remains a challenge. NTS causes various clinical manifestations, depending on the quantity of bacteria present in the food and the immune status of the infected individual, ranging from localized, self-limiting gastroenteritis to more serious systemic infections. Salmonellosis prevention is based on hygienic and behavioral rules related to food handling that aim to reduce the risk of infection. However, no vaccine against NTS is available for human use. This aspect, in addition to the increase in multidrug-resistant strains and the high morbidity, mortality, and socioeconomic costs of NTS-related diseases, makes the development of new prevention and control strategies urgently needed. The success of the vaccines used to protect against S. typhi encouraged the development of NTS vaccine candidates, including live attenuated, subunit-based, and recombinant-protein-based vaccines. In this review, we discuss the epidemiological burden of Salmonellosis and its primary prevention, focusing on the current status and future perspectives of the vaccines against NTS.

Non-typhoidal Salmonella in humans in India, Vietnam, Bangladesh and Sri Lanka: a systematic review

Objectives

Non-typhoidal Salmonella (NTS) commonly causes a self-limiting illness but invasive disease (iNTS) can be life-threatening. Antimicrobial resistance (AMR) increases the risk of mortality. This systematic review aimed to estimate the proportion of NTS isolated in those attending healthcare services, serovar burden, AMR, serovar-specific AMR, and case fatality rate (CFR) in India, Bangladesh, Sri Lanka and Vietnam.

Methods

The review included quantitative studies on NTS and AMR from 1980 to 2020 but excluded studies unrelated to humans or selected countries. Data were extracted from articles identified from Ovid SP, Web of Science, Wiley Cochrane Library, Elsevier Scopus and WHO Global Index Medicus. The Joanna Briggs Institute Critical Appraisal Tools Checklist for Prevalence Studies was used for risk-of-bias assessment. Meta-analyses were performed for the proportion of NTS isolated, the proportion of specific serovars isolated, percentage of AMR and CFR.

Results

Six thousand and twenty-six isolates (79 serovars) were identified from 73 studies, with Salmonella enterica serovar Typhimurium being the most common. Of the 73 selected studies, 46% were hospital/laboratory surveillance studies, examining the aetiology of invasive or non-invasive infections. The pooled proportion estimate for non-iNTS was 2.1% (95% CI: 1.2%-3.2%) and for iNTS was 0.3% (95% CI: 0.1%-0.5%). The pooled CFR was 14.9% (95% CI: 4.0%-29.6%). Pooled resistance estimates for ampicillin, ceftriaxone, chloramphenicol, ciprofloxacin, co-trimoxazole, nalidixic acid and azithromycin were calculated. MDR iNTS was less prevalent in India [22.3% (95% CI: 0.0%-66.8%)] than in Vietnam [41.2% (95% CI: 33.6%-49.3%)]. Heterogeneity of studies was high as the majority were observational surveillance studies.

Conclusions

Despite data scarcity in some countries, this review highlights the continued contribution of NTS infection to disease burden, compounded by high AMR rates.

Platelet aggregation responses to Salmonella Typhimurium are determined by host anti-Salmonella antibody levels

Invasive non-typhoidal Salmonella infections are responsible for >75 000 deaths/year and >500 000 cases/year globally. Seventy-five percent of these cases occur in Sub-Saharan Africa, an increasing number of which are from multi-drug resistant strains. Interactions between bacteria and platelets can lead to thrombus formation, which can be beneficial for control of infection (immunothrombosis), or harmful through uncontrolled inflammation and organ damage (thromboinflammation). It is unknown whether Salmonella Typhimurium can activate human platelets. To assess this, light transmission aggregometry was used to measure platelet activation by two different Salmonella Typhimurium strains in 26 healthy donors in platelet-rich plasma and washed platelets. In platelet-rich plasma, but not in washed platelets, Salmonella Typhimurium activated platelets in a donor- and strain-dependent manner mediated through the low affinity immune receptor FcγRIIA and the feedback agonists, ADP and thromboxane A2. Plasma swap studies between strong and weak responders demonstrated a plasma component was responsible for the variation between donors. Depletion of anti-Salmonella antibodies from plasma abolished Salmonella-induced platelet aggregation responses, and addition of polyclonal anti-Salmonella antibody allowed aggregation in washed platelets. Correlating levels of anti-Salmonella total IgG or the IgG1, IgG2, IgG3 and IgG4 subclasses to platelet responses revealed total IgG levels, rather than levels of individual subclasses, positively correlated with maximum platelet aggregation results, and negatively with lag times. Overall, we show that anti-Salmonella IgG antibodies are responsible for donor variation in platelet aggregation responses to Salmonella and mediate this activity through FcγRIIA.

Genomic and Transcriptomic Comparison Between Invasive Non-Typhoidal Salmonella and Non-Invasive Isolates

Invasive non-typhoidal Salmonella (iNTS) poses a significant threat to global public health. Salmonella enterica Enteritidis and Typhimurium are the primary serovars responsible for both invasive diseases and gastroenteritis. This study aims to investigate the genomic and transcriptomic differences between isolates associated with these contrasting clinical presentations. We retrieved genomes of Salmonella Enteritidis and Salmonella Typhimurium from Enterobase, utilizing blood and stool isolates as representatives for iNTS and non-iNTS, respectively. An indistinguishable phylogenetic relationship was revealed between the blood and stool isolates for both serovars. Few genes were specifically identified in iNTS. Random forest and principal coordinates analysis permitted moderate discrimination between the two sources of isolates based on overall genome content. Notably, the blood isolates of Salmonella Typhimurium displayed an elevated level of antimicrobial resistance and genome degradation compared to stool isolates. Meanwhile, transcriptome sequencing identified few genes that were differentially expressed between blood and stool isolates. Hierarchical clustering and principal component analysis did not effectively differentiate the expression profile of iNTS from non-iNTS. In summary, few genes could serve as reliable biomarkers to distinguish iNTS and non-iNTS at either the genomic or transcriptomic level. Nevertheless, iNTS has indeed accumulated subtle genomic differences from non-iNTS, which might contribute to invasiveness.

Bridging Classical Methodologies in Salmonella Investigation with Modern Technologies: A Comprehensive Review

Advancements in genomics and machine learning have significantly enhanced the study of Salmonella epidemiology. Whole-genome sequencing has revolutionized bacterial genomics, allowing for detailed analysis of genetic variation and aiding in outbreak investigations and source tracking. Short-read sequencing technologies, such as those provided by Illumina, have been instrumental in generating draft genomes that facilitate serotyping and the detection of antimicrobial resistance. Long-read sequencing technologies, including those from Pacific Biosciences and Oxford Nanopore Technologies, offer the potential for more complete genome assemblies and better insights into genetic diversity. In addition to these sequencing approaches, machine learning techniques like decision trees and random forests provide powerful tools for pattern recognition and predictive modeling. Importantly, the study of bacteriophages, which interact with Salmonella, offers additional layers of understanding. Phages can impact Salmonella population dynamics and evolution, and their integration into Salmonella genomics research holds promise for novel insights into pathogen control and epidemiology. This review revisits the history of Salmonella and its pathogenesis and highlights the integration of these modern methodologies in advancing our understanding of Salmonella.

Synergistic antimicrobial activity of alpha-linolenic acid in combination with tetracycline or florfenicol against multidrug-resistant Salmonella typhimurium

Salmonella is a major foodborne pathogen that can be transmitted from livestock and poultry to humans through the food chain. Due to the widespread use of antibiotics, antibiotic resistance Salmonella has become an important factor threatening food safety. Combining antibiotic and non-antibiotic agents is a promising approach to address the widespread emergence of antibiotic-resistant pathogens. In this study, we investigated the antibiotic resistance profile and molecular characterization of different serotypes of Salmonella isolated from large-scale egg farms using drug susceptibility testing and whole genome sequencing. The synergistic effect of alpha-linolenic acid (ALA) with antibiotics was evaluated using the checkerboard test and time-kill curve. The molecular mechanism of α-linolenic acid synergism was explored using biochemical assays, pull-down assays, and molecular docking. In vivo efficacy of ALA in combination with florfenicol (FFC) or tetracycline (TET) against multidrug-resistant (MDR) Salmonella enterica subsp. enterica serovar typhimurium was also investigated using a mouse model. We found that ALA reduced the minimum inhibitory concentration (MIC) of tetracycline and florfenicol in all strains tested. When ALA (512 mg/L) was combined with florfenicol (32 mg/L) or tetracycline (16 mg/L), we observed disruption of cell membrane integrity, increased outer membrane permeability, lowered cell membrane potential, and inhibition of proton-drive-dependent efflux pumps. The synergistic treatment also inhibited biofilm production and promoted oxidative damage. These changes together led to an increase in bacterial antibiotic susceptibility. The improved efficacy of ALA combination treatment with antibiotics was validated in the mouse model. Molecular docking results indicate that ALA can bind to membrane proteins via hydrogen bonding. Our findings demonstrated that combined treatment using ALA and antibiotics is effective in preventing infections involving MDR bacteria. Our results are of great significance for the scientific and effective prevention and control of antibiotic resistance Salmonella, as well as ensuring food safety.

Emerging blaNDM-positive Salmonella enterica in Chinese pediatric infections

Non-typhoidal Salmonella (NTS) is a common zoonotic foodborne pathogen, whose rising antimicrobial resistance has been an urgent threat to global public health. Here, we reported two carbapenem-resistant Salmonella enterica (CRSE) strains (NBFE-049 and NBFE-164) carrying the blaNDM genes, which were recovered from two Chinese children, belonged to Salmonella enterica serovar Typhimurium (S. Typhimurium) monophasic variant (S. 1,4,[5],12:i:-) ST34 (a sequence type) and S. Typhimurium ST19, respectively. Genes blaNDM-5 and blaNDM-13 were detected in NBFE-049 and NBFE-164, respectively. The blaNDM-5 in NBFE-049 was located in an IncHI2-type plasmid, named pNBFE-049. In NBFE-164, the blaNDM-13 was located in an IncI1-type plasmid, named pNBFE-164. The plasmid pNBFE-164 successfully transferred its resistance phenotype into the recipient strain Escherichia coli J53 with a high efficiency of 1.1 × 10-2, while no transconjugants were obtained in pNBFE-049 conjugation assays. We further elucidated the genetic relationships of globally occurring New Delhi Metallo-β-lactamase (NDM)-positive strains and locally distributed clinical strains within the same serovar. The closest relative of NBFE-049 was clinical Salmonella strain 1722, which was recovered in 2020 and differed by only three Single Nucleotide Polymorphisms (SNPs). No NDM-positive ST19 could be found in the National Center for Biotechnology Information (NCBI) database, and NBFE-164 showed a close genetic relationship with the other ST19 in this area. To sum up, we suggested the potential contributions of clonal spread and plasmid-mediated blaNDM transfer in CRSE dissemination. This study reported the complete genome of two blaNDM-carrying S. Typhimurium isolates, shedding new insights into the antimicrobial resistance mechanisms and dissemination patterns of the emerging CRSE.IMPORTANCENTS is one of the most common zoonotic pathogens that causes foodborne illnesses, while S. Typhimurium is one of the most common serovars. With the rising prevalence of multi-resistant Salmonella worldwide, carbapenems have emerged as the last-line antibiotics for treating severe bacterial infections. In this study, we reported the genomic characteristics of two carbapenem-resistant S. Typhimurium strains, which were recovered from two pediatric patients, carrying blaNDM-5 and blaNDM-13, providing new insights into the antimicrobial resistance deteriminants and transmission risk of blaNDM-positive NTS in China. We suggested the potential contributions of clonal spread and plasmid-mediated blaNDM transfer in CRSE dissemination. Future enhanced surveillance policy should mitigate CRSE spreading, and more importantly, clinical antimicrobial therapeutic regimens should be adjusted accordingly.

Evolution of Salmonella spp. isolated compared to those of Campylobacter spp. in faecal samples for 12 years

OBJECTIVE

The Autonomous Community of Galicia has adopted DECREE 216/2011 on health standards for poultry production, in addition to the Spanish national programs. However, no program has yet been implemented to eradicate campylobacteriosis, which shares the same reservoir. The aim of this study was to compare the evolution of Salmonella spp. isolates with respect to those of Campylobacter spp. in faecal samples received by the Microbiology Department.

METHODS

A retrospective descriptive comparative study was conducted through the Laboratory Information System (SIL) of Salmonella spp. isolated against Campylobacter spp. in faeces between 2011 and 2022 at the Lucus Augusti University Hospital (HULA), Lugo, Spain.

RESULTS

A total of 35,704 stool samples were analysed, of which 3,045 were positive. 751 Salmonella spp. were isolated. Statistical differences were observed in the annual distribution (p<0.01), with a clear turning point in 2018. Five hundred and five patients required hospital care, especially in 2014 with 72 patients (69%). On the other hand, 1,587 Campylobacter spp. were isolated. Required hospital care 1,002 patients during the study, with a peak in 2019 with 111 cases (62%).

CONCLUSIONS

The reduction of salmonellosis cases and the maintenance of campylobacteriosis cases are directly related to the implementation of DECREE 216/2011. This, in turn, has reduced the pressure on hospitals in the HULA health area. Therefore, we believe that the ONE Health concept is being strengthened in the area studied.

Plasmid-mediated azithromycin resistance in non-typhoidal Salmonella recovered from human infections

OBJECTIVES

Mechanisms of non-typhoidal Salmonella (NTS) resistance to azithromycin have rarely been reported. Here we investigate the epidemiology and genetic features of 10 azithromycin-resistant NTS isolates.

METHODS

A total of 457 NTS isolates were collected from a tertiary hospital in Guangzhou. We performed antimicrobial susceptibility tests, conjugation experiments, efflux pump expression tests, whole-genome sequencing and bioinformatics analysis to conduct the study.

RESULTS

The results showed that 10 NTS isolates (2.8%) were resistant to azithromycin with minimum inhibitory concentration values ranging from 128 to 512 mg/L and exhibited multidrug resistance. The phylogenetic tree revealed that 5 S. London isolates (AR1-AR5) recognized at different times and departments were closely related [3-74 single-nucleotide polymorphisms (SNPs)] and 2 S. Typhimurium isolates (AR7 and AR8) were clones (<3 SNPs) at 3-month intervals. The azithromycin resistance was conferred by mph(A) gene found on different plasmids, including IncFIB, IncHI2, InFII, IncC and IncI plasmids. Among them, IncFIB, InFII and IncHI2 plasmids carried different IS26-class 1 integron (intI1) arrangement patterns that mediated multidrug resistance transmission. Conjugative IncC plasmid encoded resistance to ciprofloxacin, ceftriaxone and azithromycin. Furthermore, phylogenetic analysis demonstrated that mph(A)-positive plasmids closely related to 10 plasmids in this study were mainly discovered from NTS, Escherichia coli, Klebsiella pneumonia and Enterobacter hormaechei. The genetic environment of mph(A) in 10 NTS isolates was IS26-mph(A)-mrx(A)-mphR(A)-IS6100/IS26 that co-arranged with intI1 harbour multidrug-resistant (MDR) gene cassettes on diverse plasmids.

CONCLUSIONS

These findings highlighted that the dissemination of these plasmids carrying mph(A) and various intI1 MDR gene cassettes would seriously restrict the availability of essential antimicrobial agents for treating NTS infections.

Dietary α-linolenic acid supplementation enhances resistance to Salmonella Typhimurium challenge in chickens by altering the intestinal mucosal barrier integrity and cecal microbes

Salmonella is an important foodborne pathogen. Given the ban on the use of antibiotics during the egg-laying period in China, finding safe and effective alternatives to antibiotics to reduce Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) infections in chickens is essential for the prevention and control of this pathogen and the protection of human health. Numerous studies have shown that unsaturated fatty acids have a positive effect on intestinal inflammation and resistance to infection by intestinal pathogens. Here we investigated the protective effect of α-linolenic acid (ALA) against S. Typhimurium infection in chickens and further explored its mechanism of action. We added different proportions of ALA to the feed and observed the effect of ALA on S. Typhimurium colonization using metagenomic sequencing technology and physiological index measurements. The role of gut flora on S. Typhimurium colonization was subsequently verified by fecal microbiota transplantation (FMT). We found that ALA protects chickens from S. Typhimurium infection by reducing intestinal inflammation through remodeling the gut microbiota, up-regulating the expression of ileocecal barrier-related genes, and maintaining the integrity of the intestinal epithelium. Our data suggest that supplementation of feed with ALA may be an effective strategy to alleviate S. Typhimurium infection in chickens.

Vaccine value profile for invasive non-typhoidal Salmonella disease

Invasive non-typhoidal Salmonella (iNTS) disease is an under-recognized high-burden disease causing major health and socioeconomic issues in sub-Saharan Africa (sSA), predominantly among immune-naïve infants and young children, including those with recognized comorbidities such as HIV infection. iNTS disease is primarily caused by Salmonella enterica serovar Typhimurium sequence type (ST) 313 and 'African-restricted clades' of Salmonella Enteritidis ST11 that have emerged across the African continent as a series of epidemics associated with acquisition of new antimicrobial resistance. Due to genotypes with a high prevalence of antimicrobial resistance and scarcity of therapeutic options, these NTS serovars are designated by the World Health Organization as a priority pathogen for research and development of interventions, including vaccines, to address and reduce NTS associated bacteremia and meningitis in sSA. Novel and traditional vaccine technologies are being applied to develop vaccines against iNTS disease, and the results of the first clinical trials in the infant target population should become available in the near future. The "Vaccine Value Profile" (VVP) addresses information related predominantly to invasive disease caused by Salmonella Enteritidis and Salmonella Typhimurium prevalent in sSA. Information is included on stand-alone iNTS disease candidate vaccines and candidate vaccines targeting iNTS disease combined with another invasive serotype, Salmonella Typhi, that is also common across sSA. Out of scope for the first version of this VVP is a wider discussion on either diarrheagenic NTS disease (dNTS) also associated with Salmonella Enteritidis and Salmonella Typhimurium or the development of a multivalent Salmonella vaccines targeting key serovars for use globally. This VVP for vaccines to prevent iNTS disease is intended to provide a high-level, holistic assessment of the information and data that are currently available to inform the potential public health, economic, and societal value of pipeline vaccines and vaccine-like products. Future versions of this VVP will be updated to reflect ongoing activities such as vaccine development strategies and a "Full Vaccine Value Assessment" that will inform the value proposition of an iNTS disease vaccine. This VVP was developed by a working group of subject matter experts from academia, non-profit organizations, public private partnerships, and multi-lateral organizations, and in collaboration with stakeholders from the World Health Organization African Region. All contributors have extensive expertise on various elements of the iNTS disease VVP and collectively aimed to identify current research and knowledge gaps. The VVP was developed using only existing and publicly available information.

Bacterascites caused by Salmonella spp. following a cesarean section: A case report

RATIONALE

Bacterascites are a rare complication of cesarean sections (C/S). Here, we report the case of a patient with bacterascites after an emergent C/S.

PATIENT CONCERN

A 41-year-old female reported diffuse abdominal tightness and pain for a week after C/S, who received C/S at 38 4/7 weeks due to superimposed preeclampsia and prolonged labor.

DIAGNOSES

Bacterascites caused by Salmonella species after C/S was diagnosed.

INTERVENTIONS

Initial treatment included cefmetazole and metronidazole. On day 2, paracentesis was performed, followed by albumin and hydroxyethyl starch administration. By day 3, the patient developed pulmonary edema, necessitating Lasix administration. On day 6, ascites culture revealed Salmonella species resistant to third-generation cephalosporins, leading to meropenem therapy adjustment. This resulted in improved symptoms. Meropenem was continued for 14 days to complete the treatment regimen.

OUTCOMES

Follow-up ultrasonography revealed a decrease in ascites. As the patient clinical condition improved, she was discharged on day 20 and scheduled for outpatient department follow-up. No recurrence of ascites was observed during the subsequent follow-up period of 3 months. No ascites were noted 8 days after discharge.

LESSONS

Postoperative bacterascites with Salmonella were diagnosed. Antibiotic treatment and therapeutic paracentesis were effective for this condition.

Emerging Strategies against Non-Typhoidal Salmonella: From Pathogenesis to Treatment

Even with the intensive efforts by public health programs to control and prevent it, non-typhoidal Salmonella (NTS) infection remains an important public health challenge. It is responsible for approximately 150 million illnesses and 60,000 deaths worldwide annually. NTS infection poses significant risks with high rates of morbidity and mortality, leading to potential short- and long-term complications. There is growing concern among health authorities about the increasing incidence of antimicrobial resistance, with multidrug resistance totaling 22.6% in Europe, highlighting an urgent need for new therapeutic approaches. Our review aims to provide a comprehensive overview of NTS infection. We outline the molecular mechanisms involved in the pathogenesis of NTS infection, as well as the events leading to invasive NTS infection and the subsequent complications associated with it. Given the widespread implications of antimicrobial resistance, our review also presents the global landscape of resistance, including multidrug resistance, and delve into the underlying mechanisms driving this resistance. The rising rates of antibiotic resistance frequently lead to treatment failures, emphasizing the importance of investigating alternative therapeutic options. Therefore, in this review we also explore potential alternative therapies that could offer promising approaches to treating NTS infections.

Recurrent Salmonella bacteraemia and right internal iliac artery endarteritis in a splenectomised patient

A man in his mid-70s with a complex medical history, including splenectomy, presented with fever and rigours. Workup revealed Salmonella enterica serotype typhimurium bacteraemia and right internal iliac artery endarteritis. Two weeks following a 6-week course of antibiotics, he had a recurrence of Salmonella bacteraemia requiring an extended course of treatment.

The Economic Burden of Non-Typhoidal Salmonella and Invasive Non-Typhoidal Salmonella Infection: A Systematic Literature Review

Non-typhoidal Salmonella (NTS) infection and invasive non-typhoidal Salmonella (iNTS) infection cause a significant global health and economic burden. This systematic review aims to investigate the reported economic burden of NTS and iNTS infection, identify research gaps, and suggest future research directions. Data from PubMed and Embase databases up to April 2022 were reviewed, and articles were screened based on predefined criteria. Cost data were extracted, categorized into direct medical costs (DMCs), direct non-medical costs (DNMCs), and indirect costs (ICs), and converted into US dollars (year 2022). Data primarily originated from high-income countries (37 out of 38), with limited representation from Africa and resource-limited settings. For inpatients, DMCs were the primary cost driver for both NTS and iNTS illnesses, with estimates ranging from USD 545.9 (Taiwan, a region of China) to USD 21,179.8 (Türkiye) for NTS and from USD 1973.1 (Taiwan, a region of China) to USD 32,507.5 (United States of America) for iNTS per case. DNMCs and ICs varied widely across studies. Although study quality improved over time, methodological differences persisted. This review underscores the lack of economic data on NTS and iNTS in resource-limited settings. It also highlights the need for economic burden data in resource-limited settings and a standardized approach to generate global datasets, which is critical for informing policy decisions, especially regarding future vaccines.

Nontyphoidal salmonella septic arthritis in A patient with systemic lupus erythematosus: A case report

We report a case of septic arthritis in a 43-year-old female patient. Despite initial treatment with ceftriaxone for Nontyphoidal Salmonella based on blood and joint fluid culture results, the shoulder joint pain worsened. Suspected systemic lupus erythematosus associated synovitis did not respond to immunosuppressive therapy including methylprednisolone, hydroxychloroquine and methotrexate. Subsequent radiograph revealed a shoulder joint abscess, leading to arthroscopic joint debridement. Ceftriaxone was administered post-operatively until analgesic efficacy was attained. This case highlights the significance of accurate diagnosis and appropriate treatment for nontyphoidal Salmonella septic arthritis.

Case report: A case of piriformis pyomyositis and pyogenic sacroiliitis due to non-typhoidal Salmonella bacteremia in an immunocompetent healthy adult

Non-typhoidal Salmonella (NTS) rarely causes bacteremia and subsequent focal infections as an extraintestinal complication, even in immunocompetent adults. A 25-year-old man was hospitalized for several days with difficulty moving due to fever, acute buttock pain, and shivering. He had no recent or current respiratory symptoms and no clear gastrointestinal symptoms. Physical examination revealed mild redness around the left buttock and difficulty raising the left lower extremity due to pain, in addition to which blood tests showed high levels of inflammatory markers. His clinical course and laboratory findings suggested sepsis, and magnetic resonance imaging revealed a high-intensity area in the left piriformis muscle on diffusion-weighted imaging; therefore, acute piriformis pyomyositis was strongly suggested. Cephazolin was started upon hospitalization; however, blood and stool cultures proved positive for NTS, and the antibiotics were changed to ceftriaxone. Follow-up MRI showed a signal in the left piriformis muscle and newly developed left pyogenic sacroiliitis. On the 25th hospital day, a colonoscopy was performed to identify the portal of entry for bacteremia, which revealed a longitudinal ulcer in the sigmoid colon in the healing process. His buttock pain gradually improved, and the antibiotics were switched to oral levofloxacin, which enabled him to continue treatment in an outpatient setting. Finally, the patient completed seven weeks of antimicrobial therapy and returned to daily life without leaving any residual disability. Invasive NTS infection due to bacteremia is rare among immunocompetent adults. Piriformis pyomyositis and subsequent pyogenic sacroiliitis should be added to the differential diagnosis of acute febrile buttock pain. In the case of NTS bacteremia, the entry site must be identified for source control. Additionally, the background of the host, especially in such an immunocompetent case, needs to be clarified; therefore, the patient should be closely examined.

Stress response of Salmonella Newport with various sequence types toward plasma-activated water: Viable but nonculturable state formation and outer membrane vesicle production

This study aims to investigate the response of Salmonella Newport to plasma-activated water (PAW), a novel disinfectant that attracts attention due to its broad-spectrum antimicrobial efficacy and eco-friendliness. In this work, we demonstrated that S. Newport of different sequence types (STs) could be induced into the viable but nonculturable (VBNC) state by PAW treatment. Notably, a remarkable 99.96% of S. Newport ST45 strain entered the VBNC state after a 12-min PAW treatment, which was the fastest observed among the five S. Newport STs (ST31, ST45, ST46, ST166, ST2364). Secretion of outer membrane vesicles was observed in ST45, suggesting a potential strategy against PAW treatment. Genes related to oxidative stress (sodA, katE, trxA), outer membrane proteins (ompA, ompC, ompD, ompF) and virulence (pagC, sipC, sopE2) were upregulated in the PAW-treated S. Newport, especially in ST45. A reduction of 38-65% in intracellular ATP level after PAW treatment was observed, indicating a contributor to the formation of the VBNC state. In addition, a rapid method for detecting the proportion of VBNC cells in food products based on pagC was established. This study contributes to understanding the formation mechanism of the VBNC state in S. Newport under PAW stress and offers insights for controlling microbial risks in the food industry.

Nontyphoidal Salmonella Outbreaks Associated With Chocolate Consumption: A Systematic Review

BACKGROUND

A large, cross-border outbreak of nontyphoidal salmonellosis connected to chocolate product consumption was recently reported. This occurrence motivated us to conduct a comprehensive review of existing literature concerning outbreaks of nontyphoidal salmonellosis associated with chocolate consumption.

METHODS

We performed a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (PROSPERO CRD42022369023) in 3 databases: U.S. National Library of Medicine, Web of Science and Excerpta Medica. Google Scholar and the bibliography of each identified report were also screened. Eligible were articles published after 1970, describing outbreaks of more than 10 patients with a nontyphoidal salmonellosis associated with chocolate consumption.

RESULTS

Twenty-three articles were included, which described 12 outbreaks involving a total of 3266 patients. All outbreaks occurred in high-income countries: 1 was limited to 1 city, 6 involved 1 country and the remaining 5 involved 2 or more countries. Six outbreaks peaked in winter, 3 in autumn, 2 in spring and 1 in summer. Children were mainly affected. No predominant serotype was identified.

CONCLUSIONS

Our data documents that chocolate is an optimal medium for the transmission of nontyphoidal salmonellosis. A connected worldwide reporting system including high-income, middle-income and low-income countries is crucial to detect infectious diseases outbreaks in an early phase and avoid their spread.

REV-ERBα negatively regulates NLRP6 transcription and reduces the severity of Salmonella infection in mice

Non-typhoidal Salmonella infection is among the most frequent foodborne diseases threatening human health worldwide. The host circadian clock orchestrates daily rhythms to adapt to environmental changes, including coordinating immune function in response to potential infections. However, the molecular mechanisms underlying the interplay between the circadian clock and the immune system in modulating infection processes are incompletely understood. Here, we demonstrate that NLRP6, a novel nucleotide-oligomerization domain (NOD)-like receptor (NLR) family member highly expressed in the intestine, is closely associated with the differential day-night response to Salmonella infection. The core clock component REV-ERBα negatively regulates NLRP6 transcription, leading to the rhythmic expression of NLRP6 and the secretion of IL-18 in intestinal epithelial cells, playing a crucial role in mediating the differential day-night response to Salmonella infection. Activating REV-ERBα with agonist SR9009 in wild-type mice attenuated the severity of infection by decreasing the NLRP6 level in intestinal epithelial cells. Our findings provide new insights into the association between the host circadian clock and the immune response to enteric infections by revealing the regulation of Salmonella infection via the inhibitory effect of REV-ERBα on NLRP6 transcription. Targeting REV-ERBα to modulate NLRP6 activation may be a potential therapeutic strategy for bacterial infections.

Advancements in understanding bacterial enteritis pathogenesis through organoids

Bacterial enteritis has a substantial role in contributing to a large portion of the global disease burden and serves as a major cause of newborn mortality. Despite advancements gained from current animal and cell models in improving our understanding of pathogens, their widespread application is hindered by apparent drawbacks. Therefore, more precise models are imperatively required to develop more accurate studies on host-pathogen interactions and drug discovery. Since the emergence of intestinal organoids, massive studies utilizing organoids have been conducted to study the pathogenesis of bacterial enteritis, revealing new mechanisms and validating established ones. In this review, we focus on the advancements of several bacterial pathogenesis mechanisms observed in intestinal organoid/enteroid models, exploring the host response and bacterial effectors during the infection process. Finally, we address the features that warrant additional investigation or could be enhanced in existing organoid models in order to guide future research endeavors.

Salmonella manipulates macrophage migration via SteC-mediated myosin light chain activation to penetrate the gut-vascular barrier

The intestinal pathogen Salmonella enterica rapidly enters the bloodstream after the invasion of intestinal epithelial cells, but how Salmonella breaks through the gut-vascular barrier is largely unknown. Here, we report that Salmonella enters the bloodstream through intestinal CX3CR1+ macrophages during early infection. Mechanistically, Salmonella induces the migration/invasion properties of macrophages in a manner dependent on host cell actin and on the pathogen effector SteC. SteC recruits host myosin light chain protein Myl12a and phosphorylates its Ser19 and Thr20 residues. Myl12a phosphorylation results in actin rearrangement, and enhanced migration and invasion of macrophages. SteC is able to utilize a wide range of NTPs other than ATP to phosphorylate Myl12a. We further solved the crystal structure of SteC, which suggests an atypical dimerization-mediated catalytic mechanism. Finally, in vivo data show that SteC-mediated cytoskeleton manipulation is crucial for Salmonella breaching the gut vascular barrier and spreading to target organs.

Examining geospatial and temporal distribution of invasive non-typhoidal Salmonella disease occurrence in sub-Saharan Africa: a systematic review and modelling study

BACKGROUND

Invasive non-typhoidal Salmonella (iNTS) disease is a significant health concern in sub-Saharan Africa. While our knowledge of a larger-scale variation is growing, understanding of the subnational variation in iNTS disease occurrence is lacking, yet crucial for targeted intervention.

METHOD

We performed a systematic review of reported occurrences of iNTS disease in sub-Saharan Africa, consulting literature from PubMed, Embase and Web of Science published since 2000. Eligibility for inclusion was not limited by study type but required that studies reported original data on human iNTS diseases based on the culture of a normally sterile site, specifying subnational locations and the year, and were available as full-text articles. We excluded studies that diagnosed iNTS disease based on clinical indications, cultures from non-sterile sites or serological testing. We estimated the probability of occurrence of iNTS disease for sub-Saharan Africa on 20 km × 20 km grids by exploring the association with geospatial covariates such as malaria, HIV, childhood growth failure, access to improved water, and sanitation using a boosted regression tree.

RESULTS

We identified 130 unique references reporting human iNTS disease in 21 countries published from 2000 through 2020. The estimated probability of iNTS occurrence grids showed significant spatial heterogeneity at all levels (20 km × 20 km grids, subnational, country and subregional levels) and temporal heterogeneity by year. For 2020, the probability of occurrence was higher in Middle Africa (0.34, 95% CI: 0.25 to 0.46), followed by Western Africa (0.33, 95% CI: 0.23 to 0.44), Eastern Africa (0.24, 95% CI: 0.17 to 0.33) and Southern Africa (0.08, 95% CI: 0.03 to 0.11). Temporal heterogeneity indicated that the probability of occurrence increased between 2000 and 2020 in countries such as the Republic of the Congo (0.05 to 0.59) and Democratic Republic of the Congo (0.10 to 0.48) whereas it decreased in countries such as Uganda (0.65 to 0.23) or Zimbabwe (0.61 to 0.37).

CONCLUSION

The iNTS disease occurrence varied greatly across sub-Saharan Africa, with certain regions being disproportionately affected. Exploring regions at high risk for iNTS disease, despite the limitations in our data, may inform focused resource allocation. This targeted approach may enhance efforts to combat iNTS disease in more affected areas.

The 2022 Vaccines Against Shigella and Enterotoxigenic Escherichia coli (VASE) Conference: Summary of breakout workshops

The global public health nonprofit organization PATH hosted the third Vaccines Against Shigella and Enterotoxigenic Escherichia coli (VASE) Conference in Washington, DC, from November 29 to December 1, 2022. This international gathering focused on cutting-edge research related to the development of vaccines against neglected diarrheal pathogens including Shigella, enterotoxigenic Escherichia coli (ETEC), Campylobacter, and non-typhoidal Salmonella. In addition to the conference's plenary content, the agenda featured ten breakout workshops on topics of importance to the enteric vaccine field. This unique aspect of VASE Conferences allows focused groups of attendees to engage in in-depth discussions on subjects of interest to the enteric vaccine development community. In 2022, the workshops covered a range of topics. Two focused on the public health value of enteric vaccines, with one examining how to translate evidence into policy and the other on the value proposition of potential combination vaccines against bacterial enteric pathogens. Two more workshops explored new tools for the development and evaluation of vaccines, with the first on integrating antigen/antibody technologies for mucosal vaccine and immunoprophylactic development, and the second on adjuvants specifically for Shigella vaccines for children in low- and middle-income countries. Another pair of workshops covered the status of vaccines against two emerging enteric pathogens, Campylobacter and invasive non-typhoidal Salmonella. The remaining four workshops examined the assessment of vaccine impact on acute and long-term morbidity. These included discussions on the nature and severity of intestinal inflammation; cellular immunity and immunological memory in ETEC and Shigella infections; clinical and microbiologic endpoints for Shigella vaccine efficacy studies in children; and intricacies of protective immunity to enteric pathogens. This article provides a brief summary of the presentations and discussions at each workshop in order to share these sessions with the broader enteric vaccine field.

Antimicrobial resistance and genomic investigation of Salmonella isolated from retail foods in Guizhou, China

Introduction

Salmonella is a major foodborne pathogen worldwide that causes severe morbidity and mortality. It is mainly caused by consuming contaminated food, with retail food considered the primary source.

Methods

In Guizhou, China, 102 Salmonella strains isolated from 2016 to 2021 underwent phenotypic antimicrobial resistance testing and whole-genome sequencing (WGS) to understand Salmonella diversity, including serotypes, sequencing types (STs), antimicrobial genes, virulence genes, plasmid types, multi-locus sequence types (MLST), and core genome MLST (cgMLST).

Results and discussion

S.Typhimurium was the dominant serotype, and O:4(B) was the leading serogroup. The most prevalent genotype was ST40. Phenotypic antimicrobial resistance identified 66.7% of the sampled isolates as multi-drug resistant (MDR). S.Enteritidis (n = 7), S.Typhimurium (n = 1), S.Indiana (n = 1), S.Kentucky (n = 1), S.Uganda (n = 1), all of which were MDR, were resistant to Colistin. Resistance rates varied significantly across different strains and food types, particularly meat products exhibiting higher resistance. Notably, significant increases in resistance were observed from 2016 to 2021 for the following: ≥ 1 resistant (P = 0.001), MDR (P = 0.001), ampicillin (P = 0.001), tetracycline (P < 0.001), chloramphenicol (P = 0.030), and trimethoprim/sulfamethoxazole (P = 0.003). The marked escalation in drug resistance over the recent years, coupled with the varying resistance rates among food sources, underscores the growing public health concern. Our findings highlight the need for a coordinated approach to effectively monitor and respond to Salmonella infections in Guizhou, China.

A Population-Based Study on the Incidence, Risk Factors, and Outcome of Salmonella Bloodstream Infections in South Sweden 2012-2022

INTRODUCTION

Invasive infections caused by Salmonella are a significant global health concern. This population-based study aimed to comprehensively analyze invasive Salmonella infections in South Sweden, focusing on incidence, clinical presentation, risk factors, and outcomes.

METHODS

This population-based observational cohort study, conducted from 2012 to 2022, included all patients with Salmonella bloodstream infections (BSI) in the Skåne region, South Sweden. A control group consisted of patients with positive stool cultures/PCR for Salmonella but without BSI. Data were collected following a predefined study protocol from medical records. Standardized statistical analyses assessed patient characteristics, clinical presentation, and outcomes.

RESULTS

Between 2012 and 2022, 149 patients with SBSI were identified, with the majority having non-typhoidal Salmonella (NTS) infections (95%). A declining trend in the incidence of SBSI was observed, with the highest incidence in 2012 (1.5 per 100,000 person-years) and the lowest in 2020 (0.3 per 100,000 person-years). Patients with BSI were more likely to be older, have comorbidities, be immunosuppressed, and use proton pump inhibitors (PPIs). Additionally, patients with BSI presented with fewer gastrointestinal symptoms, had a higher respiratory rate, lower saturation, and higher SOFA scores, suggesting a more septic presentation. Patients with SBSI had significantly longer hospital stays and higher 30-day, 90-day, 180-day, and 365-day mortality rates compared to the control group.

CONCLUSION

Invasive Salmonella infections are rare in South Sweden. In a cohort of enteric and invasive Salmonella infection, the absence of classic gastroenteritis symptoms increases the risk of Salmonella bloodstream infection. This study highlights the importance of distinguishing between clinical presentations to guide appropriate treatment when Salmonella infection is suspected. The declining trend in incidence, particularly associated with international travel, necessitates further investigation to understand contributing factors.

Genomic investigation and nationwide tracking of pediatric invasive nontyphoidal Salmonella in China

Invasive nontyphoidal Salmonella (iNTS) causes significant concern with ~15% morbidity, affecting populations mainly in African countries. However, iNTS infections among the Chinese pediatric population remain largely unknown. Here, we conducted a genomic investigation to study pediatric iNTS infections in a Chinese hospital. iNTS isolates accounted for 15.2% (18/119) of all nontyphoidal Salmonella (NTS) strains. Compared to non-iNTS isolates, iNTS isolates harbored a lower prevalence of antimicrobial-resistant genes of fluoroquinolones and β-lactams, as well as disinfectant determinants and plasmids, but carried a significantly higher prevalence of cdtB, faeCDE, and tcpC genes. Importantly, we detected an emerging serovar Goldcoast as the predominant iNTS serovar locally. By integrating 320 global Goldcoast genomes based on the One Health samplings, we conducted nationwide phylogenomic tracking and detected repeated human-to-human transmission events among iNTS cases caused by an underestimated serovar Goldcoast. Together, our exploratory genomic approach highlights a new trend in pediatric iNTS infections.

Synergistic activity of Limosilactobacillus reuteri KUB-AC5 and water-based plants against Salmonella challenge in a human in vitro gut model

A synbiotic is a combination of live microorganisms and specific substrates that are selectively utilized by host microorganisms, resulting in health benefits for the host. Previous studies have demonstrated the protective effects of L. reuteri KUB-AC5 against Salmonella infection in chicken and mouse models. The probiotic activity of L. reuteri KUB-AC5 in these hosts was influenced by nutritional supplements. Water-based plants contain significant amounts of carbohydrates, particularly dietary fiber and proteins, making them potential prebiotic substrates. In this study, four water-based plants (Ulva rigida, Caulerpa lentillifera, Wolffia globosa, and Gracillaria fisheri) were screened for their ability to support the growth of L. reuteri KUB-AC5. Under monoculture testing, U. rigida exhibited the highest capacity to support the growth of L. reuteri KUB-AC5 and the production of organic acids, including acetic acid, lactic acid, and propionic acid (p ≤ 0.05). In co-culture experiments, the synbiotic combination of U. rigida and L. reuteri KUB-AC5 demonstrated the potential to eliminate Salmonella Typhimurium DMST 48437 when inoculated at 104 CFU/mL within 9 h. The synbiotic activities of U. rigida and L. reuteri KUB-AC5 were further investigated using an in vitro human gut model. Compared to the probiotic treatment, the synbiotic combination of L. reuteri KUB-AC5 and U. rigida showed significantly higher levels of L. reuteri KUB-AC5 (5.1 log copies/mL) and a reduction of S. Typhimurium by 0.8 log (CFU/ml) after 24 h (p ≤ 0.05). Synbiotic treatment also significantly promoted the production of short-chain fatty acids (SCFAs), including butyric acid, propionic acid, and acetic acid, compared to prebiotic and probiotic treatments alone (p ≤ 0.05). Furthermore, the synbiotic formulation modulated the in vitro simulated gut microbiome, enhancing putatively beneficial gut microbes, including lactobacilli, Faecalibacterium, and Blautia. Our findings demonstrated that L. reuteri KUB-AC5, in combination with U. rigida, exhibited synergistic activity, as indicated by increased viability, higher anti-pathogenicity toward Salmonella, and the ability to modulate the gut microbiome.

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.

Effects and mechanisms of Salmonella plasmid virulence gene spv on host-regulated cell death

Salmonella is responsible for the majority of food poisoning outbreaks around the world. Pathogenic Salmonella mostly carries a virulence plasmid that contains the Salmonella plasmid virulence gene (spv), a highly conserved sequence encoding effector proteins that can manipulate host cells. Intestinal epithelial cells are crucial components of the innate immune system, acting as the first barrier of defense against infection. When the barrier is breached, Salmonella encounters the underlying macrophages in lamina propria, triggering inflammation and engaging in combat with immune cells recruited by inflammatory factors. Host regulated cell death (RCD) provides a variety of means to fight against or favour Salmonella infection. However, Salmonella releases effector proteins to regulate RCD, evading host immune killing and neutralizing host antimicrobial effects. This review provides an overview of pathogen-host interactions in terms of (1) pathogenicity of Salmonella spv on intestinal epithelial cells and macrophages, (2) mechanisms of host RCD to limit or promote pathogenic Salmonella expansion, and (3) effects and mechanisms of Salmonella spv gene on host RCD.

Typhoid Fever and Non-typhoidal Salmonella Outbreaks: A Portrait of Regional Socioeconomic Inequalities in Brazil

Typhoid fever occurs in an endemic form in Brazil and is a serious public health problem in some regions. In this scenario, further research is urgently needed to identify the associations between socioeconomic factors and typhoid fever, contributing to guiding policy decisions in the country. We aimed to investigate the influence of socioeconomic disparities on the prevalence of typhoid fever and non-typhoidal Salmonella (NTS) in Brazil. A search for data from 2010 to 2019 was carried out with the national health and human development agencies. As milk and derivatives are the fourth food incriminated in food outbreaks in Brazil, analyses for detecting Salmonella spp. in commercial dairy products allowed us to assess whether the outbreaks associated with these foods are due to inadequacies in sanitary control in dairy establishments or whether they are mainly home-based outbreaks. Predictive models validated by the bootstrapping method demonstrate an association of NTS prevalence reduction with improvements in the Sanitation Service Index (Rv ≥  -8 0.686; p ≤ 0.01) and Municipal Human Development Index - MHDI - (Rv =  -0.789; p ≤ 0.02). In the North, typhoid fever prevalence had seasonal variability with the rainfall, while sanitation services (Rv ≥-0.684; p ≤ 0.04) and MHDI (Rv ≥-0.949; p ≤ 0.003) directly influenced Northeast and South Brazil. Thus, the unequal distribution of investments in the sanitation sector contributed to disparities in typhoid fever prevalence among Brazilian regions. The absence of Salmonella spp. in commercial samples ratified the collected data that the outbreaks of Salmonella spp. in the Brazilian population occur mainly at residences. These findings show that implementing public health education and increasing investments in sanitation in regions with poor service can control outbreaks of Salmonella spp. in Brazilian endemic areas.

Characterization of nontyphoidal Salmonella strains from a tertiary hospital in China: serotype diversity, multidrug resistance, and genetic insights

Objective

Nontyphoidal Salmonella is a significant public health concern due to its ability to cause foodborne illnesses worldwide. This study aims to characterize the nontyphoidal Salmonella strains isolated from patients in China.

Methods

A total of 19 nontyphoidal Salmonella strains were characterized through serovar identification, antimicrobial susceptibility testing (AST), biofilm formation assessment. Genetic relatedness was determined using pulsed-field gel electrophoresis (PFGE). WGS was employed to decipher the resistance mechanism and to contextualize the S. serovar Mbandaka strains among previously sequenced isolates in China. The biofilm associated mrkA gene was examined by PCR.

Results

The predominant serovar identified was S. Enteritidis, followed by S. Mbandaka, S. Thompson, S. Livingston, S. Alachua, and S. Infantis. PFGE analysis indicated a notable genetic similarity among the S. Mbandaka isolates. Phylogenetic analysis suggested that these strains were likely derived from a single source that had persisted in China for over five years. One multidrug resistance (MDR) S. Enteritidis isolate carried a highly transferable IncB/O/K/Z plasmid with bla CTX-M-15. One S. Thompson strain, harboring the mrkABCDF operon in an IncX1 plasmid, isolated from cutaneous lesions, demonstrated robust biofilm formation. However, no mrkABCDF loci were detected in other strains.

Conclusion

Our study emphasizes the importance of persisted surveillance and prompt response to Salmonella infections to protect public health. The dissemination of bla CTX-M-15-harboring IncB/O/K/Z plasmid and the spread of virulent mrkABCDF operon among Salmonella in China and other global regions warrant close monitoring.

A candidate glycoconjugate vaccine induces protective antibodies in the serum and intestinal secretions, antibody recall response and memory T cells and protects against both typhoidal and non-typhoidal Salmonella serovars

Human Salmonella infections pose significant public health challenges globally, primarily due to low diagnostic yield of systemic infections, emerging and expanding antibiotic resistance of both the typhoidal and non-typhoidal Salmonella strains and the development of asymptomatic carrier state that functions as a reservoir of infection in the community. The limited long-term efficacy of the currently licensed typhoid vaccines, especially in smaller children and non-availability of vaccines against other Salmonella serovars necessitate active research towards developing a multivalent vaccine with wider coverage of protection against pathogenic Salmonella serovars. We had earlier reported immunogenicity and protective efficacy of a subunit vaccine containing a recombinant outer membrane protein (T2544) of Salmonella Typhi in a mouse model. This was achieved through the robust induction of serum IgG, mucosal secretory IgA and Salmonella-specific cytotoxic T cells as well as memory B and T cell response. Here, we report the development of a glycoconjugate vaccine, containing high molecular weight complexes of Salmonella Typhimurium O-specific polysaccharide (OSP) and recombinant T2544 that conferred simultaneous protection against S. Typhi, S. Paratyphi, S. Typhimurium and cross-protection against S. enteritidis in mice. Our findings corroborate with the published studies that suggested the potential of Salmonella OSP as a vaccine antigen. The role of serum antibodies in vaccine-mediated protection is suggested by rapid seroconversion with high titers of serum IgG and IgA, persistently elevated titers after primary immunization along with a strong antibody recall response with higher avidity serum IgG against both OSP and T2544 and significantly raised SBA titers of both primary and secondary antibodies against different Salmonella serovars. Elevated intestinal secretory IgA and bacterial motility inhibition by the secretory antibodies supported their role as well in vaccine-induced protection. Finally, robust induction of T effector memory response indicates long term efficacy of the candidate vaccine. The above findings coupled with protection of vaccinated animals against multiple clinical isolates confirm the suitability of OSP-rT2544 as a broad-spectrum candidate subunit vaccine against human infection due to typhoidal and non-typhoidal Salmonella serovars.