Epidemiology and Outcomes of Nontyphoidal Salmonella Bacteremias from England, 2004 to 2015

Salmonella infections in Denmark from 2013-2022 with focus on serotype distribution, invasiveness, age, sex, and travel exposition

PURPOSE

To analyze the nationwide incidence of Salmonella infections in Denmark from 2013 to 2022.

METHODS

Confirmed cases of Salmonella enterica subsp. enterica were examined using the National Register of Enteric Pathogens during 2013-2022. Proportions, incidence rates (IR), relative risk (RR), and 95% confidence intervals (CI) were calculated to assess differences in serotypes, invasiveness, age, sex, and travel exposure.

RESULTS

We identified 9,944 Danish Salmonella enterica subsp. enterica cases, with an average annual incidence rate of 16.9 per 100,000 inhabitants, declining during the COVID-19 pandemic. Typhoidal cases totaled 206, with an average annual IR of 0.35 per 100,000 inhabitants. Enteric fever patients had a median age of 24 years (IQR:17-36). Leading non-typhoid Salmonella (NTS) serotypes were S. Enteritidis (26.4%), monophasic S. Typhimurium (16.5%), and S. Typhimurium (13.5%). Median age for NTS cases was 42 (IQR: 18-62), with even sex distribution, and a third reported travel prior to onset of disease. The overall percentage of invasive NTS (iNTS) infection was 8.1% (CI: 7.6-8.7). Eleven serotypes were associated with higher invasiveness, with S. Dublin and S. Panama having the highest invasiveness with age and sex-adjusted RR of 7.31 (CI: 6.35-8.43) and 5.42 (CI: 3.42-8.60), respectively, compared to all other NTS serotypes. Increased age was associated with higher RR for iNTS infection.

CONCLUSION

During the decade, there was a limited number of typhoidal cases. The dominant NTS serotypes were S. Enteritidis and monophasic S. Typhimurium, whereas S. Dublin and S. Panama exhibited the highest invasive potential.

Phenotypic and Molecular Characterization of a Hospital Outbreak Clonal Lineage of Salmonella enterica Subspecies enterica serovar Mikawasima Containing blaTEM-1B and blaSHV-2 That Emerged on a Neonatal Ward, During the COVID-19 Pandemic

Nontyphoid salmonella can cause severe infections in newborns and is therefore declared a pathogen of major health significance at this age. The aim of the study was molecular and antimicrobial characterization of β-lactamase-producing Salmonella Mikawasima outbreak clone on a Neonatal ward, University Hospital of Split (UHS), Croatia during the COVID-19 pandemic. From April 2020, until April 2023, 75 nonrepetitive strains of Salmonella Mikawasima were isolated from stool specimens and tested for antimicrobial resistance. All 75 isolates were resistant to ampicillin and gentamicin, while 98% of isolates were resistant to amoxicillin/clavulanic acid. A high level of resistance was observed to third-generation cephalosporins (36% to ceftriaxone and 47% to ceftazidime). Extended-spectrum β-lactamase production was phenotypically detected by double-disk synergy test in 40% of isolates. Moderate resistance to quinolones was detected; 7% of isolates were resistant to pefloxacin and ciprofloxacin. All isolates were susceptible to carbapenems, chloramphenicol, and co-trimoxazole. Fourteen representative isolates, from 2020, 2021, 2022, and 2023, were analyzed with PFGE and all of them belong to the same clone. Whole-genome sequencing (WGS) analysis of three outbreak-related strains (SM1 and SM2 from 2020 and SM3 from 2023) confirmed that these strains share the same serotype (Mikawasima), multilocus sequence typing profile (ST2030), resistance genes [blaTEM-1B, aac(6')-Iaa, aac(6')-Im, and aph(2'')-Ib)] and carry incompatibility group C (IncC) plasmid. Furthermore, the gene blaSHV-2 was detected in SM1 and SM2. In summary, WGS analysis of three representative strains clearly demonstrates the persistence of β-lactamase-producing Salmonella Mikawasima in UHS during the 4-year period.

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.

Vaccines to Control Salmonella in Poultry

This review is focused on describing and analyzing means by which Salmonella enterica serotype strains have been genetically modified with the purpose of developing safe, efficacious vaccines to present Salmonella-induced disease in poultry and to prevent Salmonella colonization of poultry to reduce transmission through the food chain in and on eggs and poultry meat. Emphasis is on use of recently developed means to generate defined deletion mutations to eliminate genetic sequences conferring antimicrobial resistance or residual elements that might lead to genetic instability. Problems associated with prior means to develop vaccines are discussed with presentation of various means by which these problems have been lessened, if not eliminated. Practical considerations are also discussed in hope of facilitating means to move lab-proven successful vaccination procedures and vaccine candidates to the marketplace to benefit the poultry industry.

Decoding the invasive nature of a tropical pathogen of concern: The invasive non-Typhoidal Salmonella strains causing host-restricted extraintestinal infections worldwide

Invasive-Non-Typhoidal Salmonella (iNTS) are the major cause of health concern in the low-income, under-developed nations in Africa and Asia that lack proper sanitation facilities. Around 5% of the NTS cases give rise to invasive, extraintestinal diseases leading to focal infections like osteomyelitis, meningitis, osteoarthritis, endocarditis and neonatal sepsis. iNTS serovars like S. Typhimurium, S. Enteritidis, S. Dublin, S. Choleraesuis show a greater propensity to become invasive than others which hints at the genetic basis of their emergence. The major risk factors attributing to the invasive diseases include immune-compromised individuals having co-infection with malaria or HIV, or suffering from malnutrition. The rampant use of antibiotics leading to the emergence of multi-drug resistant strains poses a great challenge in disease management. An extensive understanding of the iNTS pathogenesis and its epidemiology will open up avenues for the development of new vaccination and therapeutic strategies to restrict the spread of this neglected disease.

Typhoid and Non-Typhoid Salmonellosis Related Mortality in Iran, National Data from the Ministry of Health

Background

Despite the declining trend, salmonellosis is still an important preventable cause of death in Iran and the world, especially in certain age and occupational subgroups, and the need for preventive measures, especially raising awareness of at-risk groups, is necessary.

Methods

Data were obtained from the Ministry of Health covering the years 2013 to 2019. The data were then stratified by year, season, month, and province of death as well as sex, age group, belonging to rural vs. urban communities and cause of death and were then analyzed using SPSS to report differences in age, sex, seasonal patterns, and spatial distribution.

Results

Non-typhoid salmonellosis (NTS) and typhoid were recorded as the cause of 800 and 32 deaths, respectively, with the highest number in 2015 and 2013. Septicemia was the cause of 87.3% of deaths due to NTS, whereas typhoid was the cause of 62.5% of its respective cases. The highest percentage of death related to both occurred in spring (P<0.001). NTS mortality rates were higher in the 70-80 and 80-90 age groups, while typhoid mortality was greatest in the under 10 yr age group. NTS mortality was higher in urban while typhoid mortality was higher in rural areas (P<0.001). Most deaths occurred in Ardabil, Sistan and Baluchistan and Khorasan Razavi provinces and Sistan and Baluchistan, West Azerbaijan and Khorasan Razavi related to NTS and typhoid, respectively.

Conclusion

Salmonella remains a preventable cause of death, especially among the elderly and children, the data gathered in this study provides important information for priority setting in specific subpopulations and food safety policy.

Bacterial distribution and drug resistance in blood samples of children in Jiangxi Region, 2017-2021

Objective

This study aims to investigate the distribution and drug resistance of bacteria in clinical blood culture specimens from children in Jiangxi province in recent years and to provide a foundation for preventing and treating bloodstream infection diseases in children.

Methods

The study involved a statistical analysis of the isolation and drug resistance of bacterial strains obtained from blood culture specimens of children in Jiangxi province between 2017 and 2021. The analysis was performed using the WHONET 5.6 software.

Results

A total of 7,977 bacterial strains were isolated from the blood samples of children between 2017 and 2021. Of these, 2,334 strains (29.3%) were identified as Gram-negative bacteria, and 5,643 strains (70.7%) were identified as Gram-positive bacteria. The most commonly isolated pathogens were coagulase-negative Staphylococcus, Escherichia coli, and Staphylococcus aureus. Among the Gram-negative bacteria, Escherichia coli (840 strains, 36.0%), Klebsiella pneumoniae (385 strains), Salmonella (283 strains), Acinetobacter baumannii (137 strains), and Pseudomonas aeruginosa (109 strains) were the most prevalent. Among the Gram-positive bacteria, coagulase-negative Staphylococcus (3,424 strains, 60.7%), Staphylococcus aureus (679 strains), Streptococcus pneumoniae (432 strains), Enterococcus sp. (292 strains), and Streptococcus agalactiae (192 strains) were the most common. Resistance to third-generation cephalosporins (cefotaxime/ceftriaxone) was observed in 45.9% and 56.0% of Escherichia coli and Klebsiella pneumoniae strains, respectively, while resistance to carbapenems was observed in 4.6% and 20.3% of these strains, respectively. Resistance to third-generation cephalosporins (cefotaxime/ceftriaxone) was observed in 15.5% of Salmonella strains, while resistance to imipenem was absent. Carbapenem resistance was observed in 17.1% (20/117) and 13% (14/108) of Acinetobacter baumannii and Pseudomonas aeruginosa strains, respectively. Methicillin-resistant Staphylococcus aureus (MRSA) was detected in 32.7% of the strains, while methicillin-resistant coagulase-negative Staphylococcus was detected in 64.3% of the coagulase-negative Staphylococcus strains. No Staphylococcus bacteria resistant to vancomycin were detected. Four strains of vancomycin-resistant Enterococcus faecium were detected over the 5-year period, and one strain of linezolid-resistant Enterococcus faecalis was detected.

Conclusion

Gram-positive cocci were the most commonly isolated clinical pathogens in blood specimens from children in Jiangxi province. The composition of the pathogen species showed a slight change over the years. The detection ratios of pathogens varied with age group and season. Although the isolation rate of common carbapenem-resistant Enterobacter bacteria has decreased, it remains high. It is necessary to monitor the antimicrobial resistance of pathogens causing bloodstream infections in children more closely, and antimicrobial agents should be used with caution.

The global profile of antibiotic resistance in bacteria isolated from goats and sheep: A systematic review

Background and Aim

Antibiotic resistance has become an issue of global importance due to increasing levels of bacterial infections worldwide. Farm management and usage of antibiotics in livestock are known risk factors associated with the increase in global levels of antibiotic resistance. Goats and sheep are examples of livestock with large populations. Although antibiotic resistance in bacteria from livestock negatively affects both human health and the economy, the global data regarding this issue in goats and sheep are limited. Therefore, this study aimed to provide information on the antibiotic-resistance profile of bacteria isolated from goats and sheep worldwide (Asia, Europe, and Africa).

Materials and Methods

We performed a systematic review of articles published on this topic without any restriction on the year of publication. We searched the Directory of Open Access Journals, PubMed, Google Scholar, and Scopus using Boolean logic through various keywords. The search generated a total of 1325 articles, and after screening for duplicates and implementing inclusion and exclusion criteria, qualitative synthesis (i.e., qualitative systematic review) was performed on 37 articles.

Results

The synthesized information indicated that 18 Gram-positive and 13 Gram-negative bacterial species from goats and sheep were resistant to ten antibiotics, namely penicillin, ampicillin, amoxicillin, chloramphenicol, streptomycin, tetracycline, cephalothin, gentamicin, ciprofloxacin (CIP), and sulfamethoxazole. The prevalence of antibiotic resistance ranged from 0.4% to 100%. However, up to 100% of some bacteria, namely, Salmonella Dublin, Aeromonas caviae, and Aeromonas sobria, were susceptible to CIP. Staphylococcus aureus and Escherichia coli were highly resistant to all antibiotics tested. Moreover, eight of the ten antibiotics tested were critically important antibiotics for humans.

Conclusion

Antibiotic-resistant bacteria in goats and sheep are a potential risk to animal and human health. Collaboration between all stakeholders and further research is needed to prevent the negative impacts of antibiotic resistance.

Prevalence and antimicrobial resistance of Salmonella enterica serovars Enteritidis and Typhimurium isolated from retail chicken meat in Wasit markets, Iraq

Background and Aim: Food poisoning caused by Salmonella enterica serovars is the most common type of foodborne illness. Tainted chicken meat is a major vector for spreading these serovars throughout the food supply chain. Salmonella isolates that developed resistance to commonly used antimicrobials pose a noteworthy risk to public health, yet there has been a lack of data on this issue in Iraq. Therefore, it is crucial to address these serious public health challenges with an adequate database on the occurrence and antibiotic resistance of these serovars. This study aimed to determine the frequency of occurrence of Salmonella enterica serovars Enteritidis and Typhimurium (S. Enteritidis and S. Typhimurium), antimicrobial resistance (AMR), and prevalence of multidrug resistance among S. Enteritidis and S. Typhimurium isolated from poultry meat collected in Wasit Province in Iraq. Materials and Methods: A total of 150 raw and frozen poultry meat samples were gathered from retail markets in various locales across the Wasit Governorate in Iraq. Salmonella spp. were successfully cultured and identified using the technique recommended by ISO 6579:2002, with minor modifications. The multiplex polymerase chain reaction approach was used to confirm Salmonella spp. (S. Enteritidis and S. Typhimurium). A disk diffusion test was performed to determine the susceptibility to particular antimicrobial agents, and 12 different antimicrobial agents were evaluated. Results: Only 19 of the 150 (12.7%) samples tested positive for Salmonella (16% and 11% were isolated from raw and frozen chicken meat, respectively). S. Enteritidis accounted for 63.2%, whereas S. Typhimurium accounted for 36.8%. Nalidixic acid resistance was the most common (73.7%), followed by sulfamethoxazole-trimethoprim (63.2%) and tetracycline (63.2%), but gentamicin and ciprofloxacin (up to 15.8%) only had modest resistance. Antibiogram of S. Enteritidis and S. Typhimurium yield 13 antibiotypes. Among the 19 Salmonella isolates, 12 of 19 (63.2%) established resistance to no less than three categories of antimicrobials. Conclusion: This study highlighted the necessity of limiting the utilization of antibiotics in animal production by providing vital information regarding the frequency and AMR of Salmonella at markets in Wasit Province. Therefore, risk assessment models could use these data to lessen the amount of Salmonella passed on to humans in Iraq from chicken meat. Keywords: antimicrobial resistance, chicken, food poisoning, serovars.

Evaluation of Genomic Typing Methods in the Salmonella Reference Laboratory in Public Health, England, 2012-2020

We aim to provide an evidence-based evaluation of whole genome sequence (WGS) methods, employed at the Salmonella reference laboratory in England, in terms of its impact on public health and whether these methods remain a fit for purpose test under UKAS ISO 15189. The evaluation of the genomic methods were mapped against the value of detecting microbiological clusters to support the investigation of food-borne outbreaks of Salmonella in England between 2012-2020. The analysis of WGS with both SNP- and allelic-based methods provided an unprecedented level of strain discrimination and detection of additional clusters when comparing to all of the previous typing methods. The robustness of the routine genomic sequencing at the reference laboratory ensured confidence in the microbiological identifications, even in large outbreaks with complex international food distribution networks. There was evidence that the phylogeny derived from the WGS data can be used to inform the provenance of strains and support discrimination between domestic and non-domestic transmission events. Further insight on the evolutionary context of the emerging pathogenic strains was enabled with a deep dive of the phylogenetic data, including the detection of nested clusters. The public availability of the WGS data linked to the clinical, epidemiological and environmental context of the sequenced strains has improved the trace-back investigations during outbreaks. The global expansion in the use of WGS-based typing in reference laboratories has shown that the WGS methods are a fit for purpose test in public health as it has ensured the rapid implementation of interventions to protect public health, informed risk assessment and has facilitated the management of national and international food-borne outbreaks of Salmonella.

Co-existence of extended-spectrum β-lactamases blaCTX-M-9 and blaCTX-M-15 genes in Salmonella species isolated from febrile and diarrhoeagenic patients in Lagos, Nigeria: a cross-sectional study

BACKGROUND

Resistance to different antimicrobial classes by Salmonella species has generated a global public health concern. The spread of extended-spectrum β-lactamases (ESBLs) bla_CTX gene variants is also increasing. This study aimed to investigate the antibiotic resistance and the carriage of bla_CTX-M-9 and bla_CTX-M-15 as well as the quinolone resistance gene (qnrB19) among Salmonella species from hospitalised patients in Lagos, Nigeria.

METHODS

In this cross-sectional study from April 2021 to August 2021, a total of 508 samples were collected from hospitalised patients. The samples were subjected to standard microbiological investigation. All the isolates were identified using API 20E kits and real-time polymerase chain reaction (RT-PCR). The in vitro antibiotic susceptibility testing (AST) was investigated using the disk diffusion method. Detection of antibiotic resistance and virulence gene makers was conducted using RT-PCR.

RESULTS

In total, 24 Salmonella species were identified. All the isolates were non-typhoidal Salmonella isolates. None of the isolates screened was S. Typhi and S. Paratyphi. Most of the isolates were susceptible to imipenem, ciprofloxacin, ofloxacin and gentamycin, while a high level of resistance to all cephalosporins, penicillin, and some carbapenems was observed. In total, 79.2% (19/24) of the Salmonella isolates harboured the bla_CTX-M variant including 54.2% (13/24) bla_CTX-M-9 and 12.5% (3/24) bla_CTX-M-15, while co-habitation of bla_CTX-M-9 and bla_CTX-M-15 was observed in 12.5% (3/24) of the isolates, respectively. None of the isolates harboured quinolone-resistant qnrB19 gene and virulence gene stn. However, invA gene was present in 66.7% (16/24) of all isolates.

CONCLUSIONS

This study is considered the first report of bla_CTX-M-9 and bla_CTX-M-15 variants in Salmonella species in Nigeria. The continued existence of cefotaximase (CTX-M)-producing Salmonella within our environment calls for the prudent use of cephalosporins.

Prevalence, serotype, and antimicrobial resistance profiles of children infected with Salmonella in Guangzhou, southern China, 2016-2021

Purpose

Salmonella infection is a key global public health concern and has lead to an increased economic burden on society. We investigated the epidemiological characteristics and antimicrobial resistance profiles of clinically isolated Salmonella strains in Guangzhou Women and Children's Medical Center.

Patients and methods

This was a retrospective study of 1,338 Salmonella strains collected from children in Guangzhou Women and Children's Medical Center during 2016 to 2021.

Results

The results revealed that 1,338 cases of Salmonella were mainly isolated from feces and blood samples. The age distribution was dominated by infants under 3 years old. The seasonal distribution was high in summer and autumn. 48 serotypes were detected, and S. typhimurium (78.7%) was the predominant serogroup. The results of antimicrobial susceptibility showed that the highest resistance was observed in ampicillin (84.5%), while lower resistance was observed in piperacillin/tazobactam, cefoperazone/sulbactam and ciprofloxacin. The antimicrobial resistance rate of fecal isolates was higher than that of blood isolates. The five-year average detection rate of multi-drug resistant Salmonella was 8.5% (114/1338) and the MDR rate of S. typhimurium was the lowest (6.9%; 73/1053).

Conclusion

We concluded that antibacterial treatment should be carefully selected according to serotype and antimicrobial sensitivity results in children. Antimicrobial resistance monitoring for multi-drug resistant Salmonella is still required.

Fitness Trade-Offs in Phage Cocktail-Resistant Salmonella enterica Serovar Enteritidis Results in Increased Antibiotic Susceptibility and Reduced Virulence

The rapid emergence of phage-resistant bacterial mutants is a major challenge for phage therapy. Phage cocktails have been considered one approach to mitigate this issue. However, the synergistic effect of randomly selected phages in the cocktails is ambiguous. Here, we rationally designed a phage cocktail consisting of four phages that utilize the lipopolysaccharide (LPS) O antigen, the LPS outer core, the LPS inner core, and the outer membrane proteins BtuB and TolC on the Salmonella enterica serovar Enteritidis cell surface as receptors. We demonstrated that the four-phage cocktail could significantly delay the emergence of phage-resistant bacterial mutants compared to the single phage. To investigate the fitness costs associated with phage resistance, we characterized a total of 80 bacterial mutants resistant to a single phage or the four-phage cocktail. We observed that mutants resistant to the four-phage cocktail were more sensitive to several antibiotics than the single-phage-resistant mutants. In addition, all mutants resistant to the four-phage cocktail had significantly reduced virulence compared to wild-type strains. Our mouse model of Salmonella Enteritidis infection also indicated that the four-phage cocktail exhibited an enhanced therapeutic effect. Together, our work demonstrates an efficient strategy to design phage cocktails by combining phages with different bacterial receptors, which can steer the evolution of phage-resistant strains toward clinically exploitable phenotypes. IMPORTANCE The selection pressure of phage promotes bacterial mutation, which results in a fitness cost. Such fitness trade-offs are related to the host receptor of the phage; therefore, we can utilize knowledge of bacterial receptors used by phages as a criterion for designing phage cocktails. Here, we evaluated the efficacy of a phage cocktail made up of phages that target four different receptors on Salmonella Enteritidis through in vivo and in vitro experiments. Importantly, we found that pressure from phage cocktails with different receptors can drive phage-resistant bacterial mutants to evolve in a direction that entails more severe fitness costs, resulting in reduced virulence and increased susceptibility to antibiotics. These findings suggest that phage cocktail therapy using combinations of phages targeting different important receptors (e.g., LPS or the efflux pump AcrAB-TolC) on the host surface can steer the host bacteria toward more detrimental surface mutations than single-phage therapy, resulting in more favorable therapeutic outcomes.

Clinical profiles and antimicrobial resistance patterns of invasive Salmonella infections in children in China

Invasive Salmonella infections result in a significant burden of disease including morbidity, mortality, and financial cost in many countries. Besides typhoid fever, the clinical impact of non-typhoid Salmonella infections is increasingly recognized with the improvement of laboratory detection capacity and techniques. A retrospective multicenter study was conducted to analyze the clinical profiles and antimicrobial resistance patterns of invasive Salmonella infections in hospitalized children in China during 2016–2018. A total of 130 children with invasive Salmonella infections were included with the median age of 12 months (range: 1–144 months). Seventy-nine percent of cases occurred between May and October. Pneumonia was the most common comorbidity in 33 (25.4%) patients. Meningitis and septic arthritis caused by nontyphoidal Salmonella (NTS) infections occurred in 12 (9.2%) patients and 5 (3.8%) patients. Patients < 12 months (OR: 16.04) and with septic shock (OR: 23.4), vomit (OR: 13.33), convulsion (OR: 15.86), C-reactive protein (CRP) ≥ 40 g/L (OR: 5.56), and a higher level of procalcitonin (PCT) (OR: 1.05) on admission were statistically associated to an increased risk of developing meningitis. Compared to 114 patients with NTS infections, 16 patients with typhoid fever presented with higher levels of CRP and PCT (P < 0.05). The rates of resistance to ampicillin, sulfamethoxazole/trimethoprim, ciprofloxacin, and ceftriaxone among Salmonella Typhi and NTS isolates were 50% vs 57.3%, 9.1% vs 24.8%, 0% vs 11.2%, and 0% vs 9.9%, respectively. NTS has been the major cause of invasive Salmonella infections in Chinese children and can result in severe diseases. Antimicrobial resistance among NTS was more common.

Sex Differences in Salmonellosis Incidence Rates-An Eight-Country National Data-Pooled Analysis

Background: There are few studies on sex differences in the incidence rates (IR) for salmonellosis over several countries by age and time period. The purpose of this study was to explore the extent and consistency of the sex and age-specific differences. Methods: We analyzed national data from eight countries between 1994 and 2016. We computed country-specific male to female incidence rate ratios (IRRs) for each age group and pooled the data using meta-analytic methods. Variations of the IRRs by age, country and time period were evaluated using meta-regression. Results: The pooled male to female incidence RRs for ages 0–1, 1–4, 5–9 and 10–14, were 1.04 (1.02–1.06), 1.02 (1.01–1.03), 1.07 (1.05–1.08) and 1.28 (1.23–1.33), respectively. For the ages 15–44 and 45–64, the incidence rates were significantly higher in females. Meta-regression analyses indicate that age groups contributed most of the variation in the male to female IRRs. Conclusions: We suggest that genetic and hormonal factors and interactions between hormones and gut microbiota could contribute to the sex differences observed in young children. These findings should provide clues about the mechanisms of the infection, and should be useful in targeting treatments and development of vaccines. Highlights: (1) This manuscript provides consistent estimates of the excess salmonellosis incidence rates in male children up to age 15, which suggests an impact of sex hormones or genetic differences. (2) Our findings should promote the further investigations on sex-related determinants of infectious diseases.

Salmonella enterica serovars associated with bacteremia in Canada, 2006-2019

Background

Members of the bacterial genus Salmonella cause salmonellosis, a disease with a spectrum of clinical presentations from a self-limiting gastroenteritis to more severe bacteremia, organ failure and sepsis. The genus consists of over 2,600 serological variants (serovars). Important differences in the pathogenesis of Salmonella serovars have been noted.

Objective

The purpose of this study was to determine which Salmonella serovars were more likely to be associated with bacteremia in Canada.

Methods

Information on the total number of Salmonella infections and blood isolations reported to the National Enteric Surveillance Program (NESP) from 2006 to 2019 was extracted for each serovar. The risk (proportion) and likelihood (odds) of bacteremia were calculated for all serovars.

Results

Of the 96,082 Salmonella cases reported to the NESP during the 14-year study period, 4.4% (95% CI: 4.3%-4.6%) were bacteremic. Twenty nontyphoidal Salmonella (NTS) serovars were associated with lower rates of bacteremia compared to all NTS serovars, and 19 NTS serovars were identified as having higher rates. Heidelberg, Oranienburg, Schwarzengrund, Virchow, Panama and Poona among the top 25 most commonly reported serovars in Canada during the study period.

Conclusion

The identification of serovars associated with Salmonella bacteremia in Canada is a first step towards understanding differences in pathogenesis and disease presentation.

Tryptamine-functionalized magnetic nanoparticles for highly sensitive detection of Salmonella typhimurium

There is significant demand for the development of rapid, sensitive, and specific methods for detecting bacterial pathogens in order to identify the causes of food poisoning. Nucleic acid amplification tests (NAATs) allow for the culture-free detection of bacterial pathogens and are not as labor intensive and time consuming as culture-based detection methods. However, suitable sample preparation methods must be developed for the realization of simple, rapid, and sensitive NAATs. To resolve this problem, we developed a new sample preparation method that integrates bacterial pathogen enrichment and DNA extraction. We engineered magnetic nanoparticles (MNPs) with a physicochemical probe (tryptamine) for single-tube sample preparation with minimal sample loss. The tryptamine-functionalized MNPs (Indole@MNPs) showed inherent hydrophobicity owing to the indole side chain and a change in their zeta potential with a decrease in the pH. Because of their physicochemical characteristics, the Indole@MNPs could adsorb bacterial pathogens, thus allowing sample enrichment and DNA binding and release through weak electrostatic interactions via pH control. We successfully detected Salmonella enterica serovar Typhimurium, a common cause of bacterial food poisoning, at a concentration of 10 CFU/10 mL in milk samples using quantitative PCR. Thus, the proposed method allows for the simple and sensitive detection of Salmonella typhimurium and can be used for nontyphoidal salmonella detection to ensure food safety.

Prevalence, Clinical Characteristics and Changes of Antibiotic Resistance in Children with Nontyphoidal Salmonella Infections from 2009-2018 in Chongqing, China

Purpose

Nontyphoidal Salmonella (NTS) is a leading bacterial cause for acute gastroenteritis in children. With the increasing use of antibiotics worldwide, antibiotic resistance has become a global problem. However, data on NTS infections and changes in antibiotic resistance among children remain limited in China. We aimed to characterize the prevalence, clinical feature, serotype and the changes of antibiotic resistance of NTS in children in Chongqing.

Methods

501 hospitalized children with NTS infections (confirmed by positive NTS culture) in Children’s Hospital of Chongqing Medical University from January 2009 to December 2018 were included. The clinical data and drug sensitivity test results were retrospectively reviewed and analyzed. Antibiotic resistance in NTS infections was compared between 2009–2013 and 2014–2018.

Results

A total of 501 isolates were detected. Most NTS infections occurred in children under three years old, which mainly occurred between July and October. The numbers of patients with diarrhea, fever, and vomiting were 472 (94.2%), 422 (84.2%) and 146 (29.1%), respectively. Serogroup B (67.5%) was the predominant serogroup isolates. And Salmonella Typhimurium was the most common serotype (79.2%). The study compared the drug resistance of NTS from 2009 to 2013 with that from 2014 to 2018. We found the drug resistance rates of NTS to cefazolin, cefotaxime, ciprofloxacin, levofloxacin and imipenem showed an upward trend. The drug resistance rates of NTS to chloramphenicol, ampicillin, ceftriaxone, cefepime and compound sulfamethoxazole decreased slightly, but still showed high drug resistance rates. And drug resistance rates of NTS to piperacillin/tazobactam and ceftazidime decreased significantly in the last ten years. Multi-drug resistance (MDR) isolates, were detected among 69 cases (13.7%) of 501 children with NTS infections.

Conclusion

The overall antibiotic resistance rates remained at a high level in Chongqing. Continuous surveillance of antibiotic resistance in NTS and control measures such as avoiding unnecessary antibiotic therapy in general NTS gastroenteritis are important. For severe or invasive infections caused by NTS infection in Southwest China, the use of ceftazidime is recommended until antibiotic sensitivity test results are available. And the choice of antibiotics should be based on the curative effect and the antibiotics sensitivity results.

Appendectomy and Non-Typhoidal Salmonella Infection: A Population-Based Matched Cohort Study

The potential association between appendectomy and non-typhoidal Salmonella (NTS) infection has not been elucidated. We hypothesized that appendectomy may be associated with gut vulnerability to NTS. The data were retrospectively collected from the Taiwan National Health Insurance Research Database to describe the incidence rates of NTS infection requiring hospital admission among patients with and without an appendectomy. A total of 208,585 individuals aged ≥18 years with an appendectomy were enrolled from January 2000 to December 2012, and compared with a control group of 208,585 individuals who had never received an appendectomy matched by propensity score (1:1) by index year, age, sex, occupation, and comorbidities. An appendectomy was defined by the International Classification of Diseases, Ninth Revision, Clinical Modification Procedure Codes. The main outcome was patients who were hospitalized for NTS. Cox proportional hazards models were applied to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs). Two sensitivity analyses were conducted for cross-validation. Of the 417,170 participants (215,221 (51.6%) male), 208,585 individuals (50.0%) had an appendectomy, and 112 individuals developed NTS infection requiring hospitalization. In the fully adjusted multivariable Cox proportional hazards regression model, the appendectomy group had an increased risk of NTS infection (adjusted HR (aHR), 1.61; 95% CI, 1.20-2.17). Females and individuals aged 18 to 30 years with a history of appendectomy had a statistically higher risk of NTS than the control group (aHR, 1.92; 95% CI, 1.26-2.93 and aHR, 2.67; 95% CI, 1.41-5.07). In this study, appendectomy was positively associated with subsequent hospitalization for NTS. The mechanism behind this association remains uncertain and needs further studies to clarify the interactions between appendectomy and NTS.

Changing Antimicrobial Resistance and Epidemiology of Non-Typhoidal Salmonella Infection in Taiwanese Children

Non-typhoidal Salmonella (NTS) typically causes self-limiting diarrheal disease but may occasionally lead to invasive infection. This study investigated the epidemiology and antimicrobial resistance of children with NTS infection between 2012 and 2019. We retrospectively analyzed pediatric patients with NTS infections, confirmed by positive cultures, in a tertiary medical center in Taiwan in 2012 and 2019. Clinical features and laboratory data of the patients were collected. Changes in the serogroup category and antimicrobial resistance were also analyzed. Of the total 797 isolates collected, 55 had NTS bacteremia. Compared with the resistance rates in 2012, the rates of resistances to third-generation cephalosporin and ciprofloxacin were significantly higher in 2019 (4.1% vs 14.3%, P < 0.001; 1.9% vs 28.6%, P < 0.001), especially in groups B, D, and E. Moreover, we observed significantly higher antimicrobial resistance (25.3%) to third-generation cephalosporin, and approximately half the NTS isolates in the infant group were multidrug resistant – a higher rate than those of other age groups in 2019. Invasive NTS often presented with a longer fever duration, lower hemoglobin level and with no elevated C-reactive protein (P < 0.05). Non-invasive NTS isolates in 2019 were significantly more resistant to ceftriaxone (P < 0.001) and ciprofloxacin (P < 0.001) than those in 2012. The antimicrobial resistance of NTS in children has increased progressively in the past decade, and different serogroups exhibited different resistance patterns. During this period, infants showed the highest risk to get a third-generation cephalosporin-resistant NTS infection. The high rates of antimicrobial resistance among children with NTS in Taiwan merit continual surveillance.

Molecular and phenotypic characterization of efflux pump and biofilm in multi-drug resistant non-typhoidal Salmonella Serovars isolated from food animals and handlers in Lagos Nigeria

BACKGROUND

Multidrug resistance efflux pumps and biofilm formation are mechanisms by which bacteria can evade the actions of many antimicrobials. Antibiotic resistant non-typhoidal Salmonella serovars have become wide spread causing infections that result in high morbidity and mortality globally. The aim of this study was to evaluate the efflux pump activity and biofilm forming capability of multidrug resistant non-typhoidal Salmonella (NTS) serovars isolated from food handlers and animals (cattle, chicken and sheep) in Lagos.

METHODS

Forty eight NTS serovars were subjected to antibiotic susceptibility testing by the disc diffusion method and phenotypic characterization of biofilm formation was done by tissue culture plate method. Phenotypic evaluation of efflux pump activity was done by the ethidium bromide cartwheel method and genes encoding biofilm formation and efflux pump activity were determined by PCR.

RESULTS

All 48 Salmonella isolates displayed resistance to one or more classes of test antibiotics with 100% resistance to amoxicillin-clavulanic acid. Phenotypically, 28 (58.3%) of the isolates exhibited efflux pump activity. However, genotypically, 7 (14.6%) of the isolates harboured acrA, acrB and tolC, 8 (16.7%) harboured acrA, acrD and tolC while 33 (68.8%) possessed acrA, acrB, acrD and tolC. All (100%) the isolates phenotypically had the ability to form biofilm with 23 (47.9%), 24 (50.0%), 1 (2.1%) categorized as strong (SBF), moderate (MBF) and weak (WBF) biofilm formers respectively but csgA gene was detected in only 23 (47.9%) of them. Antibiotic resistance frequency was significant (p < 0.05) in SBF and MBF and efflux pump activity was detected in 6, 21, and 1 SBF, MBF and WBF respectively.

CONCLUSION

These data suggest that Salmonella serovars isolated from different food animals and humans possess active efflux pumps and biofilm forming potential which has an interplay in antibiotic resistance. There is need for prudent use of antibiotics in veterinary medicine and scrupulous hygiene practice to prevent the transmission of multidrug resistant Salmonella species within the food chain.

Epidemiology and Characterization of CTX-M-55-Type Extended-Spectrum β-Lactamase-Producing Salmonella enterica Serovar Enteritidis Isolated from Patients in Shanghai, China

The emergence of extended-spectrum β-lactamase-producing Salmonella enterica serovar Enteritidis (ESBL-SE) in humans and foods has gained global attention. In particular, CTX-M-type ESBL-SE are increasingly being detected from various sample types. The aim of this study was to comprehensively analyze the epidemiology and characteristics of bla_CTX-M-55-carrying ESBL-SE isolates of clinical origin in Shanghai, China. A total of 292 S. Enteritidis isolates were recovered from the feces and blood of outpatients and inpatients between 2006 and 2014. Overall, there was a high frequency of cefotaxime-resistant isolates (97.3%), which was significantly higher (p < 0.01) than that of isolates resistant to the other tested antibiotics. All S. Enteritidis isolates exhibited resistance to ≥1 antibiotic, and 98.0% were multidrug resistant. A total of 233 isolates were identified as ESBL-SE, 166 of which were CTX-M type. Six subtypes of CTX-M-encoding genes were detected, among which bla_CTX-M-55 (91.6%, 152/166) was the most prevalent genotype. There was high genetic similarity among bla_CTX-M-55-positive ESBL-SE. The bla_CTX-M-55 gene in the ESBL-SE donor strains could be easily transferred into Enterobacteriaceae recipient strains. This study highlights that CTX-M-55 should be considered an important surveillance target in Shanghai, China. Cephalosporins, especially cefotaxime, must be used with caution in empirical treatment for Salmonella infections.

Occurrence and antimicrobial susceptibility of Salmonella isolates from grilled chicken meat sold at retail outlets in Erbil City, Kurdistan region, Iraq

Food borne salmonellosis is a major public health problem worldwide. This study aimed to detect the occurrence and antibiotics sensitivity of Salmonella species in grilled chicken meat sold at retail outlets in Erbil City, Kurdistan, Iraq. Two hundred and twenty-five (225) samples were aseptically collected from central and suburb retail outlets. For isolation of salmonellae, samples were cultured on selective media and tested for their susceptibility to common antibiotics by disk diffusion assay. The results revealed that the overall prevalence of Salmonella among grilled chicken meat samples was 7.1%. The isolates belonged to eight different serotypes of Salmonella. These include S. Typhimurium, S. Tennessee, S. Newport, S. Enteritidis, S. Anatum, S. Arizona, S. Muenchen, and S. Montevideo. The antibiotic resistance profile revealed a total resistance to Levofloxacin and total sensitivity to Cefotaxime, Amoxicillin, and Cefadroxil. This resistance among Salmonella may pose a public health hazard that requires effective precautions and response.