Health Outcomes from Multidrug-Resistant Salmonella Infections in High-Income Countries: A Systematic Review and Meta-Analysis

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.

Assessment of the Microbiological Quality and Effect of Public Health of Ready-to-Eat Salad Samples in Isparta

Salmonella spp. and Citrobacter spp. are among the microorganisms causing important foodborne outbreaks. In this study, it was tried to determine the presence and rate of Salmonella spp. and Citrobacter spp. in salad samples collected from certain regions of province of Isparta in Türkiye. A total of 50 salad samples were analyzed. Classical culture technique was used for microbiological analysis of salad samples. Suspected isolates obtained were identified using the VITEK-2 system. Although no negative visual changes were observed in the salad samples used in the study, it was determined that the number of Gram-negative microorganisms was very high and six salad samples were not suitable for public health. In 50 salad samples, 2% Salmonella and 4% Citrobacter freundii were detected. In addition, it was determined that the Salmonella strain isolated from the salad sample was resistant to three different antibiotics and Citrobacter was resistant to two different antibiotics. Salmonella spp. and Citrobacter spp. are considered very dangerous to public health because they are associated with foodborne outbreaks and can develop antibiotic resistance very quickly. Salad producers should try to reduce the possibility of microbial contamination by using different technologies.

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

Objective

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

Methods

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

Results

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

Conclusion

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

Deletion of an immune evasion gene, steD, from a live Salmonella enterica serovar Typhimurium vaccine improves vaccine responses in aged mice

Introduction

Non-typhoidal Salmonella (NTS) generally causes self-limiting gastroenteritis. However, older adults (≥65 years) can experience more severe outcomes from NTS infection. We have previously shown that a live attenuated S. Typhimurium vaccine, CVD 1926 (I77 ΔguaBA ΔclpP ΔpipA ΔhtrA), was immunogenic in adult but not aged mice. Here we describe modification of CVD 1926 through deletion of steD, a Salmonella effector responsible for host immune escape, which we hypothesized would increase immunogenicity in aged mice.

Methods

Mel Juso and/or mutuDC cells were infected with S. Typhimurium I77, CVD 1926, and their respective steD mutants, and the MHC-II levels were evaluated. Aged (18-month-old) C57BL/6 mice received two doses of PBS, CVD 1926, or CVD 1926 ΔsteD perorally (109 CFU) and the number of FliC-specific CD4+ T cells were determined. Lastly, aged C57BL/6 mice received three doses of PBS, CVD 1926, or CVD 1926 ΔsteD perorally (109 CFU) and then were challenged perorally with wild-type S. Typhimurium SL1344 (108 CFU). These animals were also evaluated for antibody responses.

Results

MHC-II induction was higher in cells treated with steD mutants, compared to their respective parental strains. Compared to PBS-vaccinated mice, CVD 1926 ΔsteD elicited significantly more FliC-specific CD4+ T cells in the Peyer's Patches. There were no significant differences in FliC-specific CD4+ T cells in the Peyer's patches or spleen of CVD 1926- versus PBS-immunized mice. CVD 1926 and CVD 1926 ΔsteD induced similar serum and fecal anti-core and O polysaccharide antibody titers after three doses. After two immunizations, the proportion of seroconverters for CVD 1926 ΔsteD was 83% (10/12) compared to 42% (5/12) for CVD 1926. Compared to PBS-immunized mice, mice immunized with CVD 1926 ΔsteD had significantly lower S. Typhimurium counts in the spleen, cecum, and small intestine upon challenge. In contrast, there were no differences in bacterial loads in the tissues of PBS-vaccinated and CVD 1926-immunized animals.

Conclusion

These data suggest that the steD deletion enhanced the immunogenicity of our live attenuated S. Typhimurium vaccine. Deletion of immune evasion genes could be a potential strategy to improve the immunogenicity of live attenuated vaccines in older adults.

Effects of in ovo injection of bacterial peptides and CpG-ODN on Salmonella enterica serovar Heidelberg infection in specific pathogen-free (SPF) chicks

RESEARCH HIGHLIGHTS

Peptides + CpG-ODN reduced SH in caeca at the first week post-infection.Administered formulations did not reduce SH-faecal excretion.Levels of intestinal IgA were similar between all groups.CpG-ODN improved some parameters associated with chick intestinal health.

Outbreak of multidrug-resistant Salmonella infections in people linked to pig ear pet treats, United States, 2015-2019: results of a multistate investigation

Background

International distribution of contaminated foods can be a source of Salmonella infections in people and can contribute to the spread of antimicrobial-resistant bacteria across countries. We report an investigation led by the United States Centers for Disease Control and Prevention, the Food and Drug Administration (FDA), and state governmental officials into a multistate outbreak of salmonellosis linked to pig ear pet treats.

Methods

Pig ear treats and companion dogs were tested for Salmonella by state officials and the FDA. Products were traced back to the country of origin when possible. Cases were defined as outbreak illnesses in people associated with one of seven Salmonella serotypes genetically related to samples from pig ear pet treats, with isolation dates from June 2015 to September 2019. Whole genome sequencing (WGS) of isolates was used to predict antimicrobial resistance.

Findings

The outbreak included 154 human cases in 34 states. Of these, 107 of 122 (88%) patients reported dog contact, and 65 of 97 (67%) reported contact with pig ear pet treats. Salmonella was isolated from 137 pig ear treats, including some imported from Argentina, Brazil, and Colombia, and from four dogs. WGS predicted 77% (105/137) of human and 43% (58/135) of pig ear treat isolates were resistant to ≥3 antimicrobial classes.

Interpretation

This was the first documented United States multistate outbreak of Salmonella infections linked to pig ear pet treats. This multidrug-resistant outbreak highlights the interconnectedness of human health and companion animal ownership and the need for zoonotic pathogen surveillance to prevent human illness resulting from internationally transported pet food products.

Funding

Animal Feed Regulatory Program Standards award. Animal and product testing conducted by FDA Vet-LIRN was funded by Vet-LIRN infrastructure grants (PAR-22-063).

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

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

Clinical Outcomes of Patients With Nontyphoidal Salmonella Infections by Isolate Resistance-Foodborne Diseases Active Surveillance Network, 10 US Sites, 2004-2018

BACKGROUND

Nontyphoidal Salmonella causes an estimated 1.35 million US infections annually. Antimicrobial-resistant strains are a serious public health threat. We examined the association between resistance and the clinical outcomes of hospitalization, length-of-stay ≥3 days, and death.

METHODS

We linked epidemiologic data from the Foodborne Diseases Active Surveillance Network with antimicrobial resistance data from the National Antimicrobial Resistance Monitoring System (NARMS) for nontyphoidal Salmonella infections from 2004 to 2018. We defined any resistance as resistance to ≥1 antimicrobial and clinical resistance as resistance to ampicillin, azithromycin, ceftriaxone, ciprofloxacin, or trimethoprim-sulfamethoxazole (for the subset of isolates tested for all 5 agents). We compared outcomes before and after adjusting for age, state, race/ethnicity, international travel, outbreak association, and isolate serotype and source.

RESULTS

Twenty percent of isolates (1105/5549) had any resistance, and 16% (469/2969) had clinical resistance. Persons whose isolates had any resistance were more likely to be hospitalized (31% vs 28%, P = .01) or have length-of-stay ≥3 days (20% vs 16%, P = .01). Deaths were rare but more common among those with any than no resistance (1.0% vs 0.4%, P = .01). Outcomes for patients whose isolates had clinical resistance did not differ significantly from those with no resistance. After adjustment, any resistance (adjusted odds ratio 1.23, 95% confidence interval 1.04-1.46) remained significantly associated with hospitalization.

CONCLUSIONS

We observed a significant association between nontyphoidal Salmonella infections caused by resistant pathogens and likelihood of hospitalization. Clinical resistance was not associated with poorer outcomes, suggesting that factors other than treatment failure (eg, strain virulence, strain source, host factors) may be important.

Effects of intrinsic characteristics of Salmonella enterica strains isolated from foods and humans, and their interaction with food matrices during simulated gastric conditions

The stomach's acidic pH is a crucial barrier against foodborne pathogens such as Salmonella enterica. This study investigated the survival of S. enterica under simulated oral and gastric conditions (SGC; pH 2 for 120 min) as a function of intrinsic pathogen characteristics and food matrix. Fifty-seven S. enterica strains isolated from food and human infections (previously characterized by serotype, virulotype, multi-drug resistance, isolation source, and isolation season) were subjected to SGC using water as a vehicle. Population reduction among the 57 isolates ranged from 2.7 to 4.7 log CFU, revealing that human isolates were inactivated less than food isolates (p = 0.0008). Among food strains, strains isolated during the cold season (food sampled from December to February) displayed the highest reduction (p = 0.00002). Six representatives of the 57 S. enterica strains were selected according to their virulotype and antimicrobial profile. They were further used to evaluate their survival under SGC in four food matrices (water, mango, tomato, and chicken), measuring S. enterica at 30 min intervals. The strains in chicken showed the lowest reduction and inactivation rate (1.42 ± 0.35 log CFU; 0.03 ± 0.005 min-1), followed by tomato (3.75 ± 0.57 log CFU; 0.15 ± 0.02 min-1), water (4.23 ± 0.27 log CFU; 0.17 ± 0.02 min-1), and mango (4.49 ± 0.39 log CFU; 0.17 ± 0.03 min-1). These data suggest that not all S. enterica strains have the same ability to survive under SGC, influencing the probability of arriving into the small intestine.

Assessing the difference in contamination of retail meat with multidrug-resistant bacteria using for-consumer package label claims that indicate on-farm antibiotic use practices- United States, 2016-2019

BACKGROUND

Antibiotic use in food-producing animals can select for antibiotic resistance in bacteria that can be transmitted to people through contamination of food products during meat processing. Contamination resulting in foodborne illness contributes to adverse health outcomes. Some livestock producers have implemented antibiotic use reduction strategies marketed to consumers on regulated retail meat packaging labels ("label claims").

OBJECTIVE

We investigated whether retail meat label claims were associated with isolation of multidrug-resistant organisms (MDROs, resistant to ≥3 classes of antibiotics) from U.S. meat samples.

METHODS

We utilized retail meat data from the U.S. Food and Drug Administration National Antimicrobial Resistance Monitoring System (NARMS) collected during 2016-2019 for bacterial contamination of chicken breast, ground turkey, ground beef, and pork chops. We used modified Poisson regression models to compare the prevalence of MDRO contamination among meat samples with any antibiotic restriction label claims versus those without such claims (i.e., conventionally produced).

RESULTS

In NARMS, 62,338 meat samples were evaluated for bacterial growth from 2016-2019. Of these, 24,446 (39%) samples had label claims that indicated antibiotic use was restricted during animal production. MDROs were isolated from 2252 (4%) meat samples, of which 71% (n = 1591) were conventionally produced, and 29% (n = 661) had antibiotic restriction label claims. Compared with conventional samples, meat with antibiotic restriction label claims had a statistically lower prevalence of MDROs (adjusted prevalence ratio: 0.66; 95% CI: 0.61, 0.73). This relationship was consistent for the outcome of any bacterial growth.

IMPACT

This repeated cross-sectional analysis of a nationally representative retail meat surveillance database in the United States supports that retail meats labeled with antibiotic restriction claims were less likely to be contaminated with MDROs compared with retail meat without such claims during 2016-2019. These findings indicate the potential for the public to become exposed to bacterial pathogens via retail meat and emphasizes a possibility that consumers could reduce their exposure to environmental reservoirs of foodborne pathogens that are resistant to antibiotics.

Geographical and temporal distribution of multidrug-resistant Salmonella Infantis in Europe and the Americas

Recently emerged S. Infantis strains carrying resistance to several commonly used antimicrobials have been reported from different parts of the globe, causing human cases of salmonellosis and with occurrence reported predominantly in broiler chickens. Here, we performed phylogenetic and genetic clustering analyses to describe the population structure of 417 S. Infantis originating from multiple European countries and the Americas collected between 1985 and 2019. Of these, 171 were collected from 56 distinct premises located in England and Wales (E/W) between 2009 and 2019, including isolates linked to incursions of multidrug-resistant (MDR) strains from Europe associated with imported poultry meat. The analysis facilitated the comparison of isolates from different E/W sources with isolates originating from other countries. There was a high degree of congruency between the outputs of different types of population structure analyses revealing that the E/W and central European (Germany, Hungary, and Poland) isolates formed several disparate groups, which were distinct from the cluster relating to the United States (USA) and Ecuador/Peru, but that isolates from Brazil were closely related to the E/W and the central European isolates. Nearly half of the analysed strains/genomes (194/417) harboured the IncFIB(pN55391) replicon typical of the "parasitic" pESI-like megaplasmid found in diverse strains of S. Infantis. The isolates that contained the IncFIB(pN55391) replicon clustered together, despite originating from different parts of the globe. This outcome was corroborated by the time-measured phylogeny, which indicated that the initial acquisition of IncFIB(pN55391) likely occurred in Europe in the late 1980s, with a single introduction of IncFIB(pN55391)-carrying S. Infantis to the Americas several years later. Most of the antimicrobial resistance (AMR) genes were identified in isolates that harboured one or more different plasmids, but based on the short-read assemblies, only a minority of the resistance genes found in these isolates were identified as being associated with the detected plasmids, whereas the hybrid assemblies comprising the short and long reads demonstrated that the majority of the identified AMR genes were associated with IncFIB(pN55391) and other detected plasmid replicon types. This finding underlies the importance of applying appropriate methodologies to investigate associations of AMR genes with bacterial plasmids.

Contribution of Food to the Human Health Burden of Antimicrobial Resistance

The impact of foodborne antimicrobial resistance (AMR) on the human health burden of AMR infections is unknown. The aim of this review was to evaluate and summarize the scientific literature investigating all potential sources of human AMR infections related to food. A literature search was conducted in Embase (Ovid) and MEDLINE (Ovid) databases to identify appropriate studies published between 2010 and 2023. The results of the search were reviewed and categorized based on the primary subject matter. Key concepts from each category are described from the perspective of food safety as a public health objective. The search yielded 3457 references, 1921 remained after removal of duplicates, abstracts, editorials, comments, notes, retractions, and errata. No properly designed source attribution studies were identified, but 383 journal articles were considered relevant and were classified into eight subcategories and discussed in the context of four streams of evidence: prevalence data, epidemiological studies, outbreak investigations and human health impact estimates. There was sufficient evidence to conclude that AMR genes, whether present in pathogenic or nonpathogenic bacteria, constitute a foodborne hazard. The level of consumer risk owing to this hazard cannot be accurately estimated based on the data summarized here. Key gaps in the literature are noted.

Antimicrobial resistance in multistate outbreaks of nontyphoidal Salmonella infections linked to animal contact-United States, 2015-2018

Animal contact is an established risk factor for nontyphoidal Salmonella infections and outbreaks. During 2015-2018, the U.S. Centers for Disease Control and Prevention (CDC) and other U.S. public health laboratories began implementing whole-genome sequencing (WGS) of Salmonella isolates. WGS was used to supplement the traditional methods of pulsed-field gel electrophoresis for isolate subtyping, outbreak detection, and antimicrobial susceptibility testing (AST) for the detection of resistance. We characterized the epidemiology and antimicrobial resistance (AMR) of multistate salmonellosis outbreaks linked to animal contact during this time period. An isolate was considered resistant if AST yielded a resistant (or intermediate, for ciprofloxacin) interpretation to any antimicrobial tested by the CDC or if WGS showed a resistance determinant in its genome for one of these agents. We identified 31 outbreaks linked to contact with poultry (n = 23), reptiles (n = 6), dairy calves (n = 1), and guinea pigs (n = 1). Of the 26 outbreaks with resistance data available, we identified antimicrobial resistance in at least one isolate from 20 outbreaks (77%). Of 1,309 isolates with resistance information, 247 (19%) were resistant to ≥1 antimicrobial, and 134 (10%) were multidrug-resistant to antimicrobials from ≥3 antimicrobial classes. The use of resistance data predicted from WGS increased the number of isolates with resistance information available fivefold compared with AST, and 28 of 43 total resistance patterns were identified exclusively by WGS; concordance was high (>99%) for resistance determined by AST and WGS. The use of predicted resistance from WGS enhanced the characterization of the resistance profiles of outbreaks linked to animal contact by providing resistance information for more isolates.

Prevalence and genomic characterization of Salmonella isolates from commercial chicken eggs retailed in traditional markets in Ghana

Salmonella enterica are important foodborne bacterial pathogens globally associated with poultry. Exposure to Salmonella-contaminated eggs and egg-related products is a major risk for human salmonellosis. Presently, there is a huge data gap regarding the prevalence and circulating serovars of Salmonella in chicken eggs sold in Ghana. In this study, 2,304 eggs (pools of six per sample unit) collected from informal markets in Accra, Kumasi and Tamale, representing the three ecological belts across Ghana, were tested for Salmonella. Antimicrobial susceptibility testing and Whole Genome Sequencing (WGS) of the isolates were performed using standard microdilution protocols and the Illumina NextSeq platform, respectively. The total prevalence of Salmonella was 5.5% with a higher rate of contamination in eggshell (4.9%) over egg content (1.8%). The serovars identified were S. Ajiobo (n = 1), S. Chester (n = 6), S. Hader (n = 7), S. enteritidis (n = 2); and S. I 4:b:- (n = 8). WGS analysis revealed varied sequence types (STs) that were serovar specific. The S. I 4:b:- isolates had a novel ST (ST8938), suggesting a local origin. The two S. enteritidis isolates belonged to ST11 and were identified with an invasive lineage of a global epidemic clade. All isolates were susceptible to ampicillin, azithromycin, cefotaxime, ceftazidime, gentamicin, meropenem, and tigecycline. The phenotypic resistance profiles to seven antimicrobials: chloramphenicol (13%), ciprofloxacin (94%), and nalidixic acid (94%), colistin (13%), trimethoprim (50%) sulfamethoxazole (50%) and tetracycline (50%) corresponded with the presence of antimicrobial resistance (AMR) determinants including quinolones (gyrA (D87N), qnrB81), aminoglycosides (aadA1), (aph(3")-Ib aph(6)-Id), tetracyclines (tet(A)), phenicols (catA1), trimethoprim (dfrA14 and dfrA1). The S. enteritidis and S. Chester isolates were multidrug resistant (MDR). Several virulence factors were identified, notably cytolethal distending toxin (cdtB gene), rck, pef and spv that may promote host invasion and disease progression in humans. The findings from this study indicate the presence of multidrug resistant and virulent strains of Salmonella serovars in Ghanaian chicken eggs, with the potential to cause human infections. This is a critical baseline information that could be used for Salmonella risk assessment in the egg food chain to mitigate potential future outbreaks.

A review of the global emergence of multidrug-resistant Salmonella enterica subsp. enterica Serovar Infantis

Salmonella enterica serovar Infantis is an emergent foodborne and zoonotic Salmonella serovar with critical implications for global health. In recent years, the prevalence of S. Infantis infections has increased in the United States, Europe, and Latin America, due to contaminated chicken and other foods. An essential trait of S. Infantis is its resistance to multiple antibiotics, including the critically important third-generation cephalosporins and quinolones, undermining effective medical treatment, particularly in low-resource settings. We describe the emergence of multidrug-resistant (MDR) S. Infantis, focusing on humans, animals, the environment, and food. We conducted a systematic review (1979-2021), selected 183 studies, and analyzed the origin, source, antimicrobial resistance, and presence of a conjugative plasmid of emerging S. Infantis (pESI) in reported isolates. S. Infantis has been detected worldwide, with a substantial increase since 2011. We found the highest number of isolations in the Americas (42.9 %), Europe (29.8 %), Western Pacific (17.2 %), Eastern Mediterranean (6.6 %), Africa (3.4 %), and South-East Asia (0.1 %). S. Infantis showed MDR patterns and numerous resistant genes in all sources. The primary source of MDR S. Infantis is broiler and their meat; however, this emerging pathogen is also present in other reservoirs such as food, wildlife, and the environment. Clinical cases of MDR S. Infantis have been reported in children and adults. The global emergence of S. Infantis is related to a plasmid (pESI) with antibiotic and arsenic- and mercury-resistance genes. Additionally, a new megaplasmid (pESI-like), carrying blaCTX-M-65 and antibiotic-resistant genes reported in an ancestral version, was detected in the broiler, human, and chicken meat isolates. Strains harboring pESI-like were primarily observed in the Americas and Europe. MDR S. Infantis has spread globally, potentially becoming a major public health threat, particularly in low- and middle-income countries.

Combined metabolomics and transcriptomics analysis reveals the mechanism of antibiotic resistance of Salmonella enterica serovar Typhimurium after acidic stress

Drug-resistant Salmonella is widely distributed in the meat production chain, endangering food safety and public health. Acidification of meat products during processing can induce acid stress, which may alter antibiotic resistance. Our study investigated the effects of acid stress on the antibiotic resistance and metabolic profile of Salmonella Typhimurium, and explored the underlying mechanisms using metabolomic and transcriptomic analysis. We found that acid-stressed 14028s was more sensitive to small molecule hydrophobic antibiotics (SMHA) while more resistant to meropenem (MERO). Metabolomic analysis revealed that enhanced sensitivity to SMHA was correlated with increased purine metabolism and tricarboxylic acid cycle. Transcriptomic analysis revealed the downregulation of chemotaxis-related genes, which are also associated with SMHA sensitivity. We also found a significant downregulation of the ompF gene, which encodes a major outer membrane protein OmpF of Salmonella. The decreased expression of OmpF porin hindered the influx of MERO, leading to enhanced resistance of the bacteria to the drug. Our findings contribute to greatly improve the understanding of the relationship between Salmonella metabolism, gene expression, and changes in drug resistance after acid stress, while providing a structural framework for exploring the relationship between bacterial stress responses and antibiotic resistance.

Phenotypic and genotypic antimicrobial resistance correlation and plasmid characterization in Salmonella spp. isolates from Italy reveal high heterogeneity among serovars

Introduction

The spread of antimicrobial resistance among zoonotic pathogens such as Salmonella is a serious health threat, and mobile genetic elements (MGEs) carrying antimicrobial resistance genes favor this phenomenon. In this work, phenotypic antimicrobial resistance to commonly used antimicrobials was studied, and the antimicrobial resistance genes (ARGs) and plasmid replicons associated with the resistances were determined.

Methods

Eighty-eight Italian Salmonella enterica strains (n = 88), from human, animal and food sources, isolated between 2009 and 2019, were selected to represent serovars with different frequency of isolation in human cases of salmonellosis. The presence of plasmid replicons was also investigated.

Results and discussion

Resistances to sulphonamides (23.9%), ciprofloxacin (27.3%), ampicillin (29.5%), and tetracycline (32.9%) were the most found phenotypes. ARGs identified in the genomes correlated with the phenotypical results, with blaTEM-1B, sul1, sul2, tetA and tetB genes being frequently identified. Point mutations in gyrA and parC genes were also detected, in addition to many different aminoglycoside-modifying genes, which, however, did not cause phenotypic resistance to aminoglycosides. Many genomes presented plasmid replicons, however, only a limited number of ARGs were predicted to be located on the contigs carrying these replicons. As an expectation of this, multiple ARGs were identified on contigs with IncQ1 plasmid replicon in strains belonging to the monophasic variant of Salmonella Typhimurium. In general, high variability in ARGs and plasmid replicons content was observed among isolates, highlighting a high level of heterogeneity in Salmonella enterica. Irrespective of the serovar., many of the ARGs, especially those associated with critically and highly important antimicrobials for human medicine were located together with plasmid replicons, thus favoring their successful dissemination.

Antimicrobial-Resistant Nontyphoidal Salmonella Infection Following International Travel-United States, 2018-2019

BACKGROUND

Antimicrobial resistance in nontyphoidal Salmonella (NTS) can limit treatment options. We assessed the contribution of international travel to antimicrobial-resistant NTS infections.

METHODS

We describe NTS infections that were reported to the Foodborne Diseases Active Surveillance Network during 2018-2019 and screened for genetic resistance determinants, including those conferring decreased susceptibility to first-line agents (ciprofloxacin, ceftriaxone, or azithromycin). We used multivariable logistic regression to assess the association between resistance and international travel during the 7 days before illness began. We estimated the contribution of international travel to resistance using population-attributable fractions, and we examined reported antimicrobial use.

RESULTS

Among 9301 NTS infections, 1159 (12%) occurred after recent international travel. Predicted resistance to first-line antimicrobials was more likely following travel; the adjusted odds ratio varied by travel region and was highest after travel to Asia (adjusted odds ratio, 7.2 [95% confidence interval, 5.5-9.5]). Overall, 19% (95% confidence interval, 17%-22%) of predicted resistance to first-line antimicrobials was attributable to international travel. More travelers than nontravelers receiving ciprofloxacin or other fluoroquinolones had isolates with predicted resistance to fluoroquinolones (29% vs 9%, respectively; P < .01).

CONCLUSIONS

International travel is a substantial risk factor for antimicrobial-resistant NTS infections. Understanding risks of resistant infection could help target prevention efforts.

Assessing phenotypic virulence of Salmonella enterica across serovars and sources

Introduction

Whole genome sequencing (WGS) is increasingly used for characterizing foodborne pathogens and it has become a standard typing technique for surveillance and research purposes. WGS data can help assessing microbial risks and defining risk mitigating strategies for foodborne pathogens, including Salmonella enterica.

Methods

To test the hypothesis that (combinations of) different genes can predict the probability of infection [P(inf)] given exposure to a certain pathogen strain, we determined P(inf) based on invasion potential of 87 S. enterica strains belonging to 15 serovars isolated from animals, foodstuffs and human patients, in an in vitro gastrointestinal tract (GIT) model system. These genomes were sequenced with WGS and screened for genes potentially involved in virulence. A random forest (RF) model was applied to assess whether P(inf) of a strain could be predicted based on the presence/absence of those genes. Moreover, the association between P(inf) and biofilm formation in different experimental conditions was assessed.

Results and Discussion

P(inf) values ranged from 6.7E-05 to 5.2E-01, showing variability both among and within serovars. P(inf) values also varied between isolation sources, but no unambiguous pattern was observed in the tested serovars. Interestingly, serovars causing the highest number of human infections did not show better ability to invade cells in the GIT model system, with strains belonging to other serovars displaying even higher infectivity. The RF model did not identify any virulence factor as significant P(inf) predictors. Significant associations of P(inf) with biofilm formation were found in all the different conditions for a limited number of serovars, indicating that the two phenotypes are governed by different mechanisms and that the ability to form biofilm does not correlate with the ability to invade epithelial cells. Other omics techniques therefore seem more promising as alternatives to identify genes associated with P(inf), and different hypotheses, such as gene expression rather than presence/absence, could be tested to explain phenotypic virulence [P(inf)].

Multidrug-resistant non-typhoidal Salmonella of public health significance recovered from migratory birds in Bangladesh

Non-typhoidal Salmonella provides an exemplar for the One Health approach as it encompasses public and animal health, food safety, and environmental considerations. The contribution of environmental aspects is currently less well-defined. The purpose of this study was to determine the carriage occurrence of non-typhoidal Salmonella in migratory birds in Bangladesh and assess the potential significance to public and animal health. Cloacal swabs (N = 453) were collected in the years 2018-2020 from Tanguar and Hakaluki Haors, important wetland ecosystems in Northeastern Bangladesh. The prevalence of Salmonella was 13.5% (61 positive swabs). Classical serotyping identified six serovars: Salmonella enterica subsp. enterica serovars Perth, Kentucky, Albany, Infantis, Weltevreden, and Brancaster. Resistance towards 14 antimicrobials was assessed by broth microdilution minimum inhibitory concentration determination and the antimicrobial resistance (AMR) genotype established by whole-genome sequencing. S. Perth and S. Weltevreden isolates were susceptible and harbored no acquired AMR genes. Isolates from the remaining serovars were multidrug resistant, commonly possessing resistance to tetracycline, ampicillin, chloramphenicol, sulfamethoxazole, trimethoprim, and ciprofloxacin. Salmonella resistant to ciprofloxacin meets WHO criteria for priority pathogens. There was excellent concordance between resistance phenotype and the presence of corresponding AMR genes, many of which reside on Salmonella Genomic Islands. High-level ciprofloxacin resistance correlated with the presence of mutations in the chromosomal gyrB and/or parC genes. The S. Kentucky isolates were ST198, a widely distributed multidrug-resistant lineage reported in humans and animals, and constituting an ongoing risk to public health worldwide. We have demonstrated that multidrug-resistant non-typhoidal Salmonella of public health significance can be recovered from migratory birds. A potential for risk can manifest through direct interaction, transmission to food-producing livestock on farms, and dissemination via the long range migratory movements of birds. Risks can be mitigated by measures including continued surveillance and implementation of good farm biosecurity practices.

Reduced immunogenicity of a live Salmonella enterica serovar Typhimurium vaccine in aged mice

Introduction

Non-typhoidal Salmonella (NTS) is responsible for a high burden of foodborne infections and deaths worldwide. In the United States, NTS infections are the leading cause of hospitalizations and deaths due to foodborne illnesses, and older adults (≥65 years) are disproportionately affected by Salmonella infections. Due to this public health concern, we have developed a live attenuated vaccine, CVD 1926 (I77 ΔguaBA ΔclpP ΔpipA ΔhtrA), against Salmonella enterica serovar Typhimurium, a common serovar of NTS. Little is known about the effect of age on oral vaccine responses, and due to the decline in immune function with age, it is critical to evaluate vaccine candidates in older age groups during early product development.

Methods

In this study, adult (six-to-eight-week-old) and aged (18-month-old) C57BL/6 mice received two doses of CVD 1926 (109 CFU/dose) or PBS perorally, and animals were evaluated for antibody and cell-mediated immune responses. A separate set of mice were immunized and then pre-treated with streptomycin and challenged orally with 108 CFU of wild-type S. Typhimurium SL1344 at 4 weeks postimmunization.

Results

Compared to PBS-immunized mice, adult mice immunized with CVD 1926 had significantly lower S. Typhimurium counts in the spleen, liver, and small intestine upon challenge. In contrast, there were no differences in bacterial loads in the tissues of vaccinated versus PBS aged mice. Aged mice exhibited reduced Salmonella-specific antibody titers in the serum and feces following immunization with CVD 1926 compared to adult mice. In terms of T cell responses (T-CMI), immunized adult mice showed an increase in the frequency of IFN-γ- and IL-2-producing splenic CD4 T cells, IFN-γ- and TNF-α-producing Peyer's Patch (PP)-derived CD4 T cells, and IFN-γ- and TNF-α-producing splenic CD8 T cells compared to adult mice administered PBS. In contrast, in aged mice, T-CMI responses were similar in vaccinated versus PBS mice. CVD 1926 elicited significantly more PP-derived multifunctional T cells in adult compared to aged mice.

Conclusion

These data suggest that our candidate live attenuated S. Typhimurium vaccine, CVD 1926, may not be sufficiently protective or immunogenic in older humans and that mucosal responses to live-attenuated vaccines decrease with increasing age.

Virulence and antimicrobial resistance profiles of Salmonella enterica isolated from foods, humans, and the environment in Mexico

Salmonella enterica genotypic and phenotypic characteristics play an important role in its pathogenesis, which could be influenced by its origin. This study evaluated the association among the antimicrobial resistance, virulence, and origin of circulating S. enterica strains in Mexico, isolated from foods, humans, and the environment. The antimicrobial susceptibility to fourteen antibiotics by the Kirby-Bauer method (n = 117), and the presence of thirteen virulence genes by multiplex PCR (n = 153) and by sequence alignments (n = 2963) were evaluated. In addition, a set of S. enterica isolates from Mexico (n = 344) previously characterized according to their genotypic and phenotypic print was included to increase the coverage of the association analysis. Strains with the presence of sopE and strains with the absence of sspH1 were significantly associated with multidrug-resistant (MDR) phenotypes (p < 0.05). The origin of the strains had significant associations with the antimicrobial profiles and some virulence genes (hilA, orgA, sifA, ssaQ, sseL, sspH1, pefA, and spvC) (p < 0.05). Animal-origin food isolates showed the highest frequency of MDR (57.2 %), followed by human isolates (30.0 %). Also, sspH1, pefA, and spvC were found in major frequency in human (32.4 %, 31.0 %, 31.7 %) and animal-origin foods (41.6 %, 10.6 %, 10.6 %) isolates. The findings highlighted that antimicrobial profiles and specific virulence genes of S. enterica strains are related to their origin. Similar genotypic and phenotypic characteristics between human and animal-origin foods isolates were found, suggesting that animal-origin foods isolates are the most responsible for human cases. The revealed associations can be used to improve risk estimation assessments in national food safety surveillance programs.

Quantitative Risk Assessment of Salmonella in Ground Beef Products and the Resulting Impact of Risk Mitigation Strategies on Public Health

Salmonellosis incidence rates have not declined over the last 15 years in the US despite a significant Salmonella prevalence reduction in meat and poultry products. Ground beef is currently regulated using only qualitative Salmonella criteria, and Salmonella enumeration values have been proposed as an alternative for implementing risk-based mitigation strategies to prevent illnesses. The purpose of this study was to develop a quantitative microbial risk assessment (QMRA) model to estimate the annual number of salmonellosis cases attributable to the consumption of ground beef contaminated with Salmonella and investigate the impact of risk management strategies on public health. Model results estimated 8,980 (6,222-14,215, 90% CI) annual illnesses attributable to ground beef consumption in the US. The removal or diversion of highly contaminated ground beef production lots containing levels above 10 MPN/g (0.4%) and 1 MPN/g (2.4%) would result in a 13.6% (5369-12280, 90% CI) and 36.7% (3939-8990, 90% CI) reduction of annual salmonellosis illnesses, respectively. Frozen ground beef cooked at home was the consumption scenario of highest risk for acquiring salmonellosis. Highly virulent serotypes accounted for 96.7% of annual illnesses despite only being present in 13.7% of ground beef samples. The removal of MDR Salmonella would result in decreased burden of disease with a 44% reduction in acute DALY annually. Focusing salmonellosis reduction efforts on removing highly contaminated ground beef lots, highly virulent Salmonella serotypes, and MDR Salmonella from not-ready-to-eat (NRTE) products were predicted to be effective risk prevention strategies.

A highly-safe live auxotrophic vaccine protecting against disease caused by non-typhoidal Salmonella Typhimurium in mice

BACKGROUND

Salmonella enterica serovar Typhimurium (S. Typhimurium) has become an important intestinal pathogen worldwide and is responsible for lethal invasive infections in populations at risk. There is at present an unmet need for preventive vaccines.

METHODS

IRTA GN-3728 genome was sequenced by Illumina and d-glutamate and d-glutamate/d-alanine knockout-auxotrophs were constructed. They were characterized using electron microscopy, growth/viability curves, reversion analysis, and motility/agglutination assays. Their potential as vaccine candidates were explored using two BALB/c mouse models for Salmonella infections: a systemic and an intestinal inflammation. Clinical signs/body weight and survival were monitored, mucosal lactoferrin and specific/cross-reactive IgA/IgG were quantified by enzyme-linked-immunosorbent assays and bacterial shedding/burden in fecal/tissues were evaluated.

RESULTS

The d-glutamate auxotroph, IRTA ΔmurI, is highly attenuated, immunogenic and fully protective against systemic infection. The IRTA ΔmurI Δalr ΔdadX double auxotroph, constructed to reinforce vaccine safety, showed a higher level of attenuation and was 100% effective against systemic disease. In the intestinal model, it proved to be safe, yielding a low-degree of mucosal inflammation, short-term shedding and undetectable invasiveness in the long-term, while eliciting cross-reactive fecal IgA/serum IgG against clinically relevant multidrug-resistant (MDR) S. Typhimurium strains. It also conferred protection against homologous oral challenge, and protected mice from local and extra-intestinal dissemination caused by one MDR strain responsible for an international outbreak of highly severe human infections. Additionally, oral vaccination promoted extended survival after lethal heterologous infection.

CONCLUSION

This study yielded a very safe S. Typhimurium vaccine candidate that could be further refined for mucosal application against disease in humans.

The Occurrence and Genomic Characteristics of mcr-1-Harboring Salmonella from Retail Meats and Eggs in Qingdao, China

Salmonella are widely distributed foodborne pathogens and are often associated with food animal products. Colistin resistance mediated by mcr-1 is an increasing threat; however, data on the characteristics of mcr-1-harboring Salmonella among retail foods are still lacking. In this study, retail meats from 24 supermarkets and eggs from nine markets in Qingdao city were investigated to determine the presence and genomic characteristics of mcr-1-harboring Salmonella. We found the retail meats and eggs were highly contaminated by Salmonella, with detection rates of 17.5% (31/177) and 12.3% (16/130), respectively. A total of 76 Salmonella isolates were obtained in this study, and 77.6% showed multidrug resistance (MDR). The MDR proportion of egg isolates (97.5%) was significantly higher than that in meat isolates (55.6%) (p < 0.05). The most prevalent Salmonella serotypes were Typhimurium (56.6%) and Enteritidis (17.1%). Of the 76 Salmonella isolates, 40 possessed mcr-1. All 40 mcr-1-positive isolates were ST34 S. Typhimurium and were from eggs of eight brands. Different mcr-1-harboring isolates existed in the same egg, and some isolates from different egg samples or brands showed clonal relationships. The mcr-1 was located on similar IncHI2/HI2A MDR non-conjugative plasmids lacking transfer region, resulting in the failure of conjugation. The phylogenetic tree using genome sequences showed that the mcr-1-positive isolates from eggs clustered together with mcr-1-positive isolates from chicken and humans in China, revealing that mcr-1-positive egg-borne Salmonella might be derived from chicken and could potentially trigger outbreaks in humans. The high occurrence of mcr-1-harboring Salmonella in fresh eggs is alarming, and there is an urgent need to monitor mcr-1-harboring Salmonella in retail meats and eggs. We report for the first time the role of retail eggs in disseminating mcr-1-positive Salmonella and the risk of transmission of these MDR pathogens from retail food to humans should be evaluated comprehensively.

Factors Associated with Multi-Drug-Resistant Non-Typhoidal Salmonella in the Invasive Disease, Thailand

PURPOSE

Invasive non-typhoidal Salmonella disease, iNTS is a major global health concern, especially multi-drug resistant non-typhoidal Salmonella, MDR-NTS. Information about risk factors of MDR-NTS in the invasive disease patient group was limited. This study aimed to identify those risk factors.

METHODS

This retrospective study examined data from patients who had non-typhoidal Salmonella, NTS infection, from 10 hospitals between June 2011 and June 2020. The multivariate regression analysis included demographic data, clinical data, culture reports, and antimicrobial susceptibility.

RESULTS

A total of 166 patients were invasive salmonellosis. where the median age was 8.3 years (IQR 1.8-79). 52% were the under-15-years-old group. Most of the patient data, 64.5% (107/166), was from a tertiary hospital. The majority of cases were bacteremia 95.7% (159/166). Serogroup C was the most common serogroup (39%). MDR-NTS was present in 68.8% (95% CI 7.17-11.06) of patients. Univariate analysis showed that onset of illness >3 days PTA (p=0.11), age over 60 years old (0.014), diabetic (p=0.002), or serogroup C infection (p=0.43) were significant factors for MDR-NTS infection. Multivariate analysis showed that the onset of symptoms more than 3 days before admission (p=0.001), and age over 60 years were significant factors. The patient who had white blood cells >15,000 cells/uL (p<0.001), a peak of fever ≥39 C° (p=001), and illness for more than 3 days before admission (p=0.035) were significantly related to invasive infection by multivariate analyses.

CONCLUSION

The iNTS patients who were over 60 years old or had onset of illness more than 3 days before admission were associated with MDR-NTS infection. Therefore, the choice of antimicrobials selected must be appropriate for the local prevalence and epidemiology of MDR-NTS including clinical correlation.

Population analysis of heavy metal and biocide resistance genes in Salmonella enterica from human clinical cases in New Hampshire, United States

Microbes frequently encounter heavy metals and other toxic compounds generated from natural biogeochemical processes and anthropogenic activities. Here, we analyzed the prevalence and association of genes conferring resistance to heavy metals, biocides, and antimicrobial compounds in 394 genome sequences of clinical human-derived S. enterica from New Hampshire, USA. The most prevalent was the gold operon (gesABC-golTSB), which was present in 99.2% of the genomes. In contrast, the other five heavy metal operons (arsenic, copper, mercury, silver, tellurite) were present in 0.76% (3/394)–5.58% (22/394) of the total population. The heavy metal operons and three biocide resistance genes were differentially distributed across 15 sequence types (STs) and 16 serotypes. The number of heavy metal operons and biocide resistance genes per genome was significantly associated with high number of antimicrobial resistance (AMR) genes per genome. Notable is the mercury operon which exhibited significant association with genes conferring resistance to aminoglycosides, cephalosporins, diaminopyrimidine, sulfonamide, and fosfomycin. The mercury operon was co-located with the AMR genes aac(3)-IV, ant(3”)-IIa, aph(3’)-Ia, and aph(4)-Ia, CTX-M-65, dfrA14, sul1, and fosA3 genes within the same plasmid types. Lastly, we found evidence for negative selection of individual genes of each heavy metal operon and the biocide resistance genes (dN/dS < 1). Our study highlights the need for continued surveillance of S. enterica serotypes that carry those genes that confer resistance to heavy metals and biocides that are often associated with mobile AMR genes. The selective pressures imposed by heavy metals and biocides on S. enterica may contribute to the co-selection and spread of AMR in human infections.

Serotype Diversity and Antimicrobial Resistance Profile of Salmonella enterica Isolates From Freshwater Turtles Sold for Human Consumption in Wet Markets in Hong Kong

Chelonians are recognized as a source of human salmonellosis through direct contact or consumption of their meat. Freshwater turtles sold for food are widely available in wet markets in Asia. In this pilot study, 50 turtles belonging to three species were randomly sampled from wet markets throughout Hong Kong. The turtles were humanely euthanised and their feces or the colon were sampled for Salmonella culture. The Salmonella isolates obtained were serotyped and examined for phenotypic antimicrobial resistance and the presence of antimicrobial resistance genes. The study reports a high prevalence (42%, 95% CI: 29.4–55.8) and considerable serotype diversity of Salmonella among turtles sold in wet markets. The most common among the 11 serotypes isolated were S. Oranienburg and S. Thompson, which have been reported in turtles previously. The serotype S. Manhattan is reported in chelonians for the first time. Resistance to streptomycin and chloramphenicol was common, despite the latter being banned from aquaculture in mainland China since 2002. Resistance against fluoroquinolones and third-generation cephalosporins which represent first-line treatment options for salmonellosis was also observed. The multidrug-resistance gene cfr is identified for the first time in Salmonella. This is a worrying finding as it indicates an expansion of the cfr reservoir and potential horizontal spread to other bacteria. The results of this study emphasize the need for close surveillance of Salmonella from turtles sold as food and better regulation of turtle farming to safeguard public health and improve animal welfare.

Retail Chicken Carcasses as a Reservoir of Multidrug-Resistant Salmonella

is a major cause of foodborne disease outbreaks worldwide, mainly through poultry. Recently, there has been an increase in multidrug-resistant (MDR) Salmonella infections globally. The increased drug resistance results in increased costs and poorer health outcomes due to unavailability or delayed treatment. This study aims to determine the prevalence of Salmonella in retail raw chicken meat and identify their antimicrobial resistance profiles. A total of 270 retail raw chicken carcasses (local and imported) were collected from three hypermarket chains in Qatar between November 2017 and April 2018. Thirty carcasses were contaminated with Salmonella (11.11%). The prevalence of Salmonella in locally produced chicken was higher than in imported chicken (OR = 2.56, 95% CI: 1.18–5.53, p = 0.016). No significant differences were found between the prevalence and storage temperature or hypermarket chain. The highest resistance rates in the isolates were reported to tetracycline (73.7%) followed by nitrofurantoin (53.3%), ampicillin (50%), amoxicillin-clavulanic acid, ceftriaxone (26.7%), and ciprofloxacin (23.3%). Eight isolates were potential extended-spectrum β-lactamase-producers, all in imported frozen chicken (p < 0.0001). Additionally, 43.3% of the isolates were MDR and associated with frozen chicken (OR = 16.88, 95% CI: 2.55–111.47, p = 0.002). The findings indicate that while the prevalence of Salmonella in retail chicken in Qatar is moderate, a large proportion of them are MDR.

Risk factors for hospitalization among adults aged ≥65 years with non-typhoidal Salmonella infection linked to backyard poultry contact

OBJECTIVE

We describe the epidemiology of live poultry-associated salmonellosis (LPAS) and investigate potential risk factors associated with hospitalization among adults aged ≥65 years in the United States during 2008-2017. LPAS is a public health concern in the United States, especially among people with increased risk for hospitalization, such as older adults.

SAMPLE

We analysed data from people aged ≥65 years with non-typhoidal salmonellosis who reported live poultry contact within seven days prior to illness onset.

PROCEDURE

We used logistic regression to estimate the odds of hospitalization associated with several risk factors including types of live poultry contact exposures.

RESULTS

LPAS among older adults in this analysis resulted in high hospitalization rates. Salmonella Hadar infection was associated with increased hospitalization. Among older adults with LPAS, 109 individuals of 127 (86%) reported contact with live poultry at their or someone else's residence, and 85 of 105 with available information (81%) reported owning poultry.

CONCLUSIONS AND CLINICAL RELEVANCE

Additional infection prevention information and education targeted at poultry-owning older adults are needed to prevent illness and hospitalization.

Invasive non-typhoidal Salmonella infection complicated by metastatic infections: report of three cases

Non-typhoidal Salmonella (NTS) disease is usually a self-limiting infection presenting with digestive symptoms. However, disseminated presentation with involvement of secondary infectious sites is observed. We report diagnostic specificities and challenges related to the management of three patients with invasive NTS (iNTS) and secondary infectious locations. Among the seven patients (age range 46 – 83 years), four (two with extra-digestive infectious sites) had at least one immune debilitating condition. Two patients were incidentally discovered with iNTS and deceased after developing a septic shock despite antimicrobial treatment. Two individuals recovered under medical treatment without complications. Three other patients presented with secondary infectious sites. Case 1 suffered from urinary tract infection and dorsolumbar spondylodiscitis that responded well to antimicrobials and surgery. Abdominal prosthetic aortic aneurysm was diagnosed in case 2 and medical treatment only was applied. After four years of follow-up, he remains under antimicrobial treatment. Case 3 presented with conjoint thoracic aortic aneurysm and cutaneous abscesses managed with antimicrobials and surgery. Atherosclerosis and previous vascular intervention were the predisposing events for vascular involvement. iNTS is a serious disease carrying a high risk of mortality or secondary locations. Secondary locations can be managed by long duration antimicrobial therapy combined with surgery. Spine and aortitis are the most frequent secondary locations. Multi-drug resistant NTS represent an additional risk of mortality. Public health measures should be implemented to limit the spread of NTS to humans and the emergence of drug resistance.

The European Union Summary Report on Antimicrobial Resistance in zoonotic and indicator bacteria from humans, animals and food in 2019–2020

Data on antimicrobial resistance (AMR) in zoonotic and indicator bacteria from humans, animals and food are collected annually by the EU Member States (MSs), jointly analysed by the EFSA and the ECDC and reported in a yearly EU Summary Report. The annual monitoring of AMR in animals and food within the EU is targeted at selected animal species corresponding to the reporting year. The 2020 monitoring specifically focussed on poultry and their derived carcases/meat, while the monitoring performed in 2019 specifically focused on fattening pigs and calves under 1 year of age, as well as their derived carcases/meat. Monitoring and reporting of AMR in 2019–2020 included data regarding Salmonella, Campylobacter and indicator E. coli isolates, as well as data obtained from the specific monitoring of presumptive ESBL‐/AmpC‐/carbapenemase‐producing E. coli isolates. Additionally, some MSs reported voluntary data on the occurrence of methicillin‐resistant Staphylococcus aureus in animals and food, with some countries also providing data on antimicrobial susceptibility. This report provides an overview of the main findings of the 2019–2020 harmonised AMR monitoring in the main food‐producing animal populations monitored, in carcase/meat samples and in humans. Where available, monitoring data obtained from pigs, calves, broilers, laying hens and turkeys, as well as from carcase/meat samples and humans were combined and compared at the EU level, with particular emphasis on multidrug resistance, complete susceptibility and combined resistance patterns to critically important antimicrobials, as well as Salmonella and E. coli isolates possessing ESBL‐/AmpC‐/carbapenemase phenotypes. The key outcome indicators for AMR in food‐producing animals, such as complete susceptibility to the harmonised panel of antimicrobials in E. coli and the prevalence of ESBL‐/AmpC‐producing E. coli have been specifically analysed over the period 2014–2020.

A natural compound hyperoside targets Salmonella Typhimurium T3SS needle protein InvG

The antimicrobial actions of natural compounds derived from medicinal plants have been well documented. However, their detailed mechanism underlying the action against microorganisms remains largely unexplored. Salmonella enterica is a...

Detection, quantification, and characterization of Salmonella enterica in mango, tomato, and raw chicken purchased in the central region of Mexico

To estimate human exposure to Salmonella enterica, it is essential to understand the pathogen distribution and characteristics. Prevalence and concentration of S. enterica were determined in mango, tomato, and raw chicken samples purchased in three states (Aguascalientes, Querétaro, and Guadalajara) located in the central region of Mexico during two seasons. In addition, S. enterica isolates were characterized by absence/presence of 13 virulence genes (chromosomal, prophage, and plasmid) and resistance to 14 antibiotics. A total of 300 samples of mango, 272 of tomato, and 354 of raw chicken were analyzed. The mean of the prevalence (24.9%) and concentration (-0.61 Log MPN/g) of S. enterica in chicken was higher than in mango (1.3%, -1.7 Log MPN/g) and tomato (1.1%, -1.7 Log MPN). Among S. enterica isolates (284), there were 7 different virulotypes, belonging 68.7% of isolates to V2; there was high variability in the presence of mobile genetic elements. The occurrence of specific mobile elements ranged from 81.4% to 11.3% among isolates. Among the isolates, 91.5% were resistant to at least one antibiotic with ampicillin being the most frequent; 54.9% of isolates were multidrug resistant. Data from this study can be used for quantitative microbial risk assessment of S. enterica related to mango, tomato, and raw chicken consumption in the central region of Mexico. PRACTICAL APPLICATION: Data on the prevalence and concentration of Salmonella enterica obtained in this study can be used to estimate the exposure assessment for the consumption of mango, tomato, and chicken in the central region of Mexico. In addition, the characteristics of the S. enterica isolates could be used to select representative strains for future studies to evaluate the intraspecies variability.

In Silico Detection of Antimicrobial Resistance Integrons in Salmonella enterica Isolates from Countries of the Andean Community

Antimicrobial resistance genes are often associated with integrons, which promote their movement between and within DNA molecules. IntFinder 1.0 and I-VIP v1.2 were used for the detection of integrons and their associated resistance genes in assembled sequences and raw reads. A dataset comprising 1688 sequenced Salmonella enterica isolates from countries of the Andean Community was developed. A total of 749 and 680 integrons were identified by IntFinder 1.0 and I-VIP v1.2, respectively; class 2 integrons were the most abundant followed by class 1, whereas no class 3 integrons were detected. These elements were mainly associated with isolates from animal sources. S. Infantis ST32 contained the majority of integrons. Trimethoprim resistance genes (dfrA) were found in greater numbers than others, including aadA and bla genes. The presence of these resistance integrons may come as a response to antibiotic misuse, especially of co-trimoxazole. This represents a public health risk as novel resistant strains might appear due to gene dissemination. The information gathered from in silico studies not only contributes to our understanding of integron dynamics in pathogenic Salmonella, but also helps identify potential emergent patterns of resistance in the region, which is fundamental for developing pertinent antibiotic surveillance programs.

Diversity and Resistance Profiles of Human Non-typhoidal Salmonella spp. in Greece, 2003-2020

Salmonella spp. is one of the most common foodborne pathogens in humans. Here, we summarize the laboratory surveillance data of human non-typhoidal salmonellosis in Greece for 2003–2020. The total number of samples declined over the study period (p < 0.001). Of the 193 identified serotypes, S. Enteritidis was the most common (52.8%), followed by S. Typhimurium (11.5%), monophasic S. Typhimurium 1,4,[5],12:i:- (4.4%), S. Bovismorbificans (3.4%) and S. Oranienburg (2.4%). The isolation rate of S. Enteritidis declined (p < 0.001), followed by an increase of the less common serotypes. Monophasic S. Typhimurium has been among the five most frequently identified serotypes every year since it was first identified in 2007. Overall, Salmonella isolates were resistant to penicillins (11%); aminoglycosides (15%); tetracyclines (12%); miscellaneous agents (sulphonamides, trimethoprim, chloramphenicol and streptomycin) (12%) and third-generation cephalosporins (2%). No isolate was resistant to carbapenems. In total, 2070 isolates (24%) were resistant to one or two antimicrobial classes and 903 (10%) to three and more. Out of the 1166 isolates resistant to fluoroquinolones (13%), 845 (72%) were S. Enteritidis. S. Enteritidis was also the most frequently identified serotype with a resistance to third-generation cephalosporins (37%, 62/166), followed by S. Typhimurium (12%, 20/166). MDR was most frequently identified for S. Typhimurium and its monophasic variant (resistant phenotype of ampicillin, streptomycin, tetracycline and sulphamethoxazole with or without chloramphenicol or trimethoprim).

Emergence of a Salmonella enterica serovar Typhimurium ST34 isolate, CFSA629, carrying a novel mcr-1.19 variant cultured from egg in China

OBJECTIVES

This study aimed to characterize the genomic features of a Salmonella enterica serovar Typhimurium ST34 isolate, CFSA629, which carried a novel mcr-1 variant, designated as mcr-1.19, mapped to an ESBL-encoding IncHI2 plasmid.

METHODS

Antimicrobial susceptibility assays as well as WGS were carried out on isolate CFSA629. The complete closed genome was obtained and then explored to obtain genomic features. Plasmid sequence comparison was performed for pCFSA629 with similar plasmids and the mcr-1 genetic environment was analysed.

RESULTS

S. Typhimurium ST34 CFSA629 expressed an MDR phenotype to six classes of compound and consisted of a single circular chromosome and one plasmid. It possessed 11 resistance genes including 2 ESBL genes that mapped to the chromosome and the plasmid; an IS26-flanked composite-like transposon was identified. A novel mcr-1 variant (mcr-1.19) was identified, which had a unique SNP (G1534A) that gave rise to a novel MCR-1 protein containing a Val512Ile amino acid substitution. Plasmid pCFSA629 possessed a conjugative plasmid transfer gene cluster as well as an antimicrobial resistance-encoding gene cluster-containing region that contained two IS26 composite-like transposonal modules, but was devoid of any plasmid-mediated quinolone resistance genes. The background of mcr-1.19 consisted of an ISApl1-mcr-1-PAP2-ter module.

CONCLUSIONS

We report on an MDR S. Typhimurium ST34 CFSA629 isolate cultured from egg in China, harbouring an mcr-1.19 variant mapped to an IncHI2 plasmid. This highlights the importance of surveillance to mitigate dissemination of mcr-encoding genes among foodborne Salmonella. Improved surveillance is important for tackling the dissemination of mcr genes among foodborne Salmonella around the world.

Molecular Characterization and Survive Abilities of Salmonella Heidelberg Strains of Poultry Origin in Brazil

The aim of the study was to evaluate the genotypic and phenotypic characteristics of 20 strains of S. Heidelberg (SH) isolated from broilers produced in southern Brazil. The similarity and presence of genetic determinants linked to virulence, antimicrobial resistance, biofilm formation, and in silico-predicted metabolic interactions revealed this serovar as a threat to public health. The presence of the ompC, invA, sodC, avrA, lpfA, and agfA genes was detected in 100% of the strains and the luxS gene in 70% of them. None of the strains carries the bla_SHV, mcr-1, qnrA, qnrB, and qnrS genes. All strains showed a multidrug-resistant profile to at least three non-β-lactam drugs, which include colistin, sulfamethoxazole, and tetracycline. Resistance to penicillin, ceftriaxone (90%), meropenem (25%), and cefoxitin (25%) were associated with the presence of bla_CTX–M and bla_CMY–2 genes. Biofilm formation reached a mature stage at 25 and 37°C, especially with chicken juice (CJ) addition. The sodium hypochlorite 1% was the least efficient in controlling the sessile cells. Genomic analysis of two strains identified more than 100 virulence genes and the presence of resistance to 24 classes of antibiotics correlated to phenotypic tests. Protein-protein interaction (PPI) prediction shows two metabolic pathways correlation with biofilm formation. Virulence, resistance, and biofilm determinants must be constant monitoring in SH, due to the possibility of occurring infections extremely difficult to cure and due risk of the maintenance of the bacterium in production environments.

Antimicrobial Resistance and Genomic Characterization of Two mcr-1-Harboring Foodborne Salmonella Isolates Recovered in China, 2016

The mcr-1 gene mediating mobile colistin resistance in Escherichia coli was first reported in China in 2016 followed by reports among different species worldwide, especially in E. coli and Klebsiella. However, data on its transmission in Salmonella are still lacking. This study analyzed the antimicrobial resistance (AMR) profiles and the mcr-1 gene presence in 755 foodborne Salmonella from 26 provinces of mainland, China in 2016. Genomic features of two mcr-1-carrying isolates, genome sequencing, serotypes and further resistance profiles were studied. Among the 755 Salmonella tested, 72.6% were found to be resistant to at least one antimicrobial agent and 10% were defined as multi-drug resistant (MDR). Salmonella Derby CFSA231 and Salmonella Typhimurium CFSA629 were mcr-1-harboring isolates. Both expressed an MDR phenotype and included a single circular chromosome and one plasmid. Among the 22 AMR genes identified in S. Derby CFSA231, only the mcr-1 gene was localized on the IncX4 type plasmid pCFSA231 while 20 chromosomal AMR genes, including four plasmid-mediated quinolone resistance (PMQR) genes, were mapped within a 64 kb Salmonella genomic island (SGI) like region. S. Typhimurium CFSA629 possessed 11 resistance genes including an mcr-1.19 variant and two ESBL genes. Two IS26-flanked composite-like transposons were identified. Additionally, 153 and 152 virulence factors were separately identified in these two isolates with secretion system and fimbrial adherence determinants as the dominant virulence classes. Our study extends our concern on mcr-1-carrying Salmonella in regards to antimicrobial resistance and virulence factors, and highlight the importance of surveillance to mitigate dissemination of mcr-encoding genes among foodborne Salmonella.

The European Union Summary Report on Antimicrobial Resistance in zoonotic and indicator bacteria from humans, animals and food in 2018/2019

Data on antimicrobial resistance (AMR) in zoonotic and indicator bacteria from humans, animals and food are collected annually by the EU Member States (MSs), jointly analysed by the EFSA and the ECDC and reported in a yearly EU Summary Report. The annual monitoring of AMR in animals and food within the EU is targeted at selected animal species corresponding to the reporting year. The 2018 monitoring specifically focussed on poultry and their derived carcases/meat, while the monitoring performed in 2019 specifically focused on pigs and calves under 1 year of age, as well as their derived carcases/meat. Monitoring and reporting of AMR in 2018/2019 included data regarding Salmonella, Campylobacter and indicator Escherichia coli isolates, as well as data obtained from the specific monitoring of presumptive ESBL-/AmpC-/carbapenemase-producing E. coli isolates. Additionally, some MSs reported voluntary data on the occurrence of meticillin-resistant Staphylococcus aureus in animals and food, with some countries also providing data on antimicrobial susceptibility. This report provides an overview of the main findings of the 2018/2019 harmonised AMR monitoring in the main food-producing animal populations monitored, in related carcase/meat samples and in humans. Where available, data monitoring obtained from pigs, calves, broilers, laying hens and turkeys, as well as from carcase/meat samples and humans were combined and compared at the EU level, with particular emphasis on multidrug resistance, complete susceptibility and combined resistance patterns to critically important antimicrobials, as well as Salmonella and E. coli isolates possessing ESBL-/AmpC-/carbapenemase phenotypes. The outcome indicators for AMR in food-producing animals such as complete susceptibility to the harmonised panel of antimicrobials in E. coli and the prevalence of ESBL-/AmpC-producing E. coli have been also specifically analysed over the period 2015-2019.

Identification and characterization of a spreadable IncI1 plasmid harbouring a blaCTX-M-15 gene in an Italian human isolate of Salmonella serovar Napoli

Salmonella enterica subsp. enterica serovar Napoli (S. Napoli) ranks among the top serovars causing human infections in Italy, although not common in other European countries. Isolates are generally pan-susceptible or resistant to aminoglycosides only, however data on antimicrobial resistance genes in strains of S. Napoli are limited. Recently an isolate encoding resistance to third generation cephalosporins was reported. This study aimed to characterize plasmid-encoded cephalosporin resistance due to the bla_CTX-M-15 gene in a human S. Napoli isolate in Italy, and to investigate plasmid stability over time. S. Napoli 16/174478 was confirmed to be ESBL-producing. The bla_CTX-M-15 gene was shown to be located on an IncI1α plasmid of 90,272 bp (50.03 GC%) encoding for 107 coding sequences (CDS). The plasmid was successfully transferred by conjugation to an E. coli 1816 recipient strain (conjugation frequency 3.9 × 10^-2 transconjugants per donor). Transconjugants were confirmed to carry the IncI1α plasmid, and to be ESBL-producing strains as well. Moreover, transconjugant colonies maintained the plasmid for up to 10 passages. The identification of S. Napoli isolates able to produce ESBLs is of great concern, as this pathogen is frequently associated with invasive infections and a higher risk of bacteraemia, and its reservoir has not yet been clearly identified.

Shared Extended-Spectrum β-Lactamase-Producing Salmonella Serovars between Agricultural and Aquatic Environments Revealed through invA Amplicon Sequencing

The presence of antibiotic-resistant Salmonella spp. in the environment is of great public health interest, worldwide. Furthermore, its extended-spectrum β-lactamase (ESBL)-producing strains constitute an emerging global health concern due to their limited treatment options in hospital. Therefore, this study aimed at characterising and tracking nonresistant and ESBL-producing Salmonella spp. from agricultural settings to nearby water sources highlighting their antibiotic resistance genes (ARG) and virulence factor (VF) distribution using a combination of both culture-dependent and independent methods. Furthermore, this study investigated the diversity and shared serovars among sampled matrices using amplicon sequencing of the invasion gene A (invA) of Salmonella spp. The results showed that soil had the highest prevalence of Salmonella spp. (62.5%, 65/104) and ESBL-producing Salmonella (34.6%, 36/104). For typed ARG, the most commonly detected gene was blaOXA with 75% (30/40), followed by blaCTX-M 67.5% (27/40),blaTEM 40% (16/40) and sul1 30% (12/40) gene; blaSHV gene was not detected in isolated ESBL-producing Salmonella spp. For VF, the most detected gene was invA (96.9%, 38/40), followed by spaM (17.5%, 7/40), spiC (40%, 16/40), orfL (32.5%, 13/40), misL 32.5% (13/40) and pipD 32.5 (13/40). For diversity analysis, soil, manure, irrigation water and nearby freshwater revealed 81, 68, 12 and 9 serovars, respectively. Soil, manure, irrigation water and freshwater stream samples shared five serovars, which indicated circulation of ESBL-producing Salmonella spp. within the agricultural environment and nearby water sources. Soil is therefore identified as one of the major reservoirs of ESBL-producing Salmonella spp. It is concluded that agricultural environment contamination may have a direct relationship with the presence of antibiotic-producing Salmonella in freshwater streams.

Ambient Air Pollution, Extreme Temperatures and Birth Outcomes: A Protocol for an Umbrella Review, Systematic Review and Meta-Analysis

Prenatal exposure to ambient air pollution and extreme temperatures are among the major risk factors of adverse birth outcomes and with potential long-term effects during the life course. Although low- and middle-income countries (LMICs) are most vulnerable, there is limited synthesis of evidence in such settings. This document describes a protocol for both an umbrella review (Systematic Review 1) and a focused systematic review and meta-analysis of studies from LMICs (Systematic Review 2). We will search from start date of each database to present, six major academic databases (PubMed, CINAHL, Scopus, MEDLINE/Ovid, EMBASE/Ovid and Web of Science Core Collection), systematic reviews repositories and references of eligible studies. Additional searches in grey literature will also be conducted. Eligibility criteria include studies of pregnant women exposed to ambient air pollutants and/or extreme temperatures during pregnancy with and without adverse birth outcomes. The umbrella review (Systematic Review 1) will include only previous systematic reviews while Systematic Review 2 will include quantitative observational studies in LMICs. Searches will be restricted to English language using comprehensive search terms to consecutively screen the titles, abstracts and full-texts to select eligible studies. Two independent authors will conduct the study screening and selection, risk of bias assessment and data extraction using JBI SUMARI web-based software. Narrative and semi-quantitative syntheses will be employed for the Systematic Review 1. For Systematic Review 2, we will perform meta-analysis with two alternative meta-analytical methods (quality effect and inverse variance heterogeneity) as well as the classic random effect model. If meta-analysis is infeasible, narrative synthesis will be presented. Confidence in cumulative evidence and the strength of the evidence will be assessed. This protocol is registered with PROSPERO (CRD42020200387).

The role of animals as a source of antimicrobial resistant nontyphoidal Salmonella causing invasive and non-invasive human disease in Vietnam

BACKGROUND

Nontyphoidal Salmonella (NTS) are associated with both diarrhea and bacteremia. Antimicrobial resistance (AMR) is common in NTS in low-middle income countries, but the major source(s) of AMR NTS in humans are not known. Here, we aimed to assess the role of animals as a source of AMR in human NTS infections in Vietnam. We retrospectively combined and analyzed 672 NTS human and animal isolates from four studies in southern Vietnam and compared serovars, sequence types (ST), and AMR profiles. We generated a population structure of circulating organisms and aimed to attribute sources of AMR in NTS causing invasive and noninvasive disease in humans using Bayesian multinomial mixture models.

RESULTS

Among 672 NTS isolates, 148 (22%) originated from human blood, 211 (31%) from human stool, and 313 (47%) from animal stool. The distribution of serovars, STs, and AMR profiles differed among sources; serovars Enteritidis, Typhimurium, and Weltevreden were the most common in human blood, human stool, and animals, respectively. We identified an association between the source of NTS and AMR profile; the majority of AMR isolates were isolated from human blood (p < 0.001). Modelling by ST-AMR profile found chickens and pigs were likely the major sources of AMR NTS in human blood and stool, respectively; but unsampled sources were found to be a major contributor.

CONCLUSIONS

Antimicrobial use in food animals is hypothesized to play role in the emergence of AMR in human pathogens. Our cross-sectional population-based approach suggests a significant overlap between AMR in NTS in animals and humans, but animal NTS does explain the full extent of AMR in human NTS infections in Vietnam.

Field investigations of multidrug-resistant Salmonella Infantis epidemic strain incursions into broiler flocks in England and Wales

Salmonella Infantis is a major public health concern and has become established in the broiler sector in some European countries, as well as globally, and is frequently multidrug resistant (MDR). Three broiler farms in England and Wales, which had incursions of MDR S. Infantis between 2013 and 2017, were investigated longitudinally. The company feed mill and two associated hatcheries were intensively sampled. Following each visit, advice on cleaning, disinfection and other control measures for Salmonella was given to help eliminate S. Infantis from the premises. Four samples collected from inside the broiler houses after cleaning and disinfection were Salmonella-positive, indicating cleaning and disinfection within houses was generally effective. However, the exterior of persistently infected houses remained substantially contaminated and feeding systems could not be sampled. Clearance of S. Infantis from affected houses requires additional attention to decontamination of these aspects. Sixty S. Infantis isolates were tested for antimicrobial susceptibility by disk diffusion tests. All isolates were MDR, with resistance to at least nalidixic acid (Na), tetracycline (T), compound sulphonamide (Su), streptomycin (S) and furazolidone. This is a similar resistance pattern to the previously identified MDR (NaSSuT) clone in some European countries. The study shows that to remove S. Infantis from premises effectively, a combined approach to poultry houses and the surrounding farm environment is necessary. A revised cleaning and disinfection programme was developed that was associated with the clearance of MDR S. Infantis from persistently infected and newly infected broiler flocks, and UK livestock remains free of MDR S. Infantis. RESEARCH HIGHLIGHTS Standard cleaning and disinfection protocols did not completely eliminate infection. A revised cleaning and disinfection programme was developed. Disinfecting feeder lines and external areas was key to eliminating S. Infantis. Identified similar antimicrobial resistance pattern to MDR epidemic S. Infantis.

A review on the origin of multidrug-resistant Salmonella and perspective of tailored phoP gene towards avirulence

Salmonellosis continues to remain a health problem as the causative organism Salmonella spp. developed resistance to many of the antibiotics. As per World Health Organization (WHO), it is estimated that enteric fever, accounts for almost 16 million cases annually and over 600,000 deaths worldwide. Recent data revealed that the multi-drug resistance (MDR) rate of enteric fever was as high as 70% in Asian countries, as compared with the overall reported incidence of 50%. Emergence of MDR typhoid fever demands the use of newer antibiotics which also not offer promising effect in recent days. Effective antimicrobial therapy is required to control morbidity and prevent death from typhoid fever. The studies on PhoP/Q regulation revealed it as a best-characterized transcriptional regulation; a two-component system required for Salmonella pathogenesis which controls the expression of more than 40 genes. The PhoP DNA binding proteins possess positively charged amino acids such as arginine, lysine and histidine which present in the DNA binding site. Prevention of PhoP binding in phoP box may ultimately prevent the expression of many regulatory mechanism which plays vital role in Salmonella virulence. Deepness study of PhoP protein and various mutation swots may offer effectual controlling of MDR Salmonella.

Differential antimicrobial susceptibility profiles between symptomatic and asymptomatic non-typhoidal Salmonella infections in Vietnamese children

Non-typhoidal Salmonella (NTS) serovars, sequences types and antimicrobial susceptibility profiles have specific associations with animal and human infections in Vietnam. Antimicrobial resistance may have an effect on the manifestation of human NTS infections, with isolates from asymptomatic individuals being more susceptible to antimicrobials than those associated with animals and human diarrhoea.