Typhoid fever and paratyphoid fever: Systematic review to estimate global morbidity and mortality for 2010

Prevalence and Influencing Factor Analysis of Typhoid/Paratyphoid Fever - China, 2011-2020

Introduction

Over the last 12 years, there has been a consistent decline in the cases of typhoid/paratyphoid fever in China. Studying the epidemiological patterns of these diseases in various provincial-level administrative divisions (PLADs) and examining potential influencing factors can provide crucial information for implementing successful control strategies.

Methods

In this study, we analyzed the cases and incidence rates of typhoid/paratyphoid fever reported in various PLADs of China from 2011 to 2022, along with exploring potential influencing factors. We initially studied spatial shifts in the incidence rates through centroid shift analysis. Seasonal variations in typhoid/paratyphoid fever onset were examined using heatmaps. Spatial autocorrelation analysis was utilized to understand the spatial correlations among different PLADs. To assess potential factors, we utilized a generalized estimating equations model that integrated spatial lag effects and sequence comparison analysis.

Results

The study identified significant geographical clustering of typhoid/paratyphoid fever cases in southwestern China. A decrease in incidence rates in the west resulted in a movement of the disease center towards the east. Higher incidence occurred during warmer seasons, highlighting the seasonal pattern of the diseases. Factors such as meteorological conditions and socioeconomic status were probable influencers of typhoid/paratyphoid fever.

Conclusions

The geographical and temporal spread of typhoid/paratyphoid fever can be impacted by meteorological and socioeconomic factors. Enhancing economic conditions, particularly in regions with high disease prevalence, could aid in the prevention and management of these fevers.

Loss of function of metabolic traits in typhoidal Salmonella without apparent genome degradation

Salmonella enterica serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars are exclusively adapted to the human host, where they can cause life-long persistent infection. A distinct feature of these serovars is the presence of a relatively high number of degraded coding sequences coding for metabolic pathways, most likely a consequence of their adaptation to a single host. As a result of convergent evolution, these serovars shared many of the degraded coding sequences although often affecting different genes in the same metabolic pathway. However, there are several coding sequences that appear intact in one serovar while clearly degraded in the other, suggesting differences in their metabolic capabilities. Here, we examined the functionality of metabolic pathways that appear intact in S. Typhi but that show clear signs of degradation in S. Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in S. Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. Thus, the inability of S. Typhi to metabolize Glucose-6-Phosphate or 3-phosphoglyceric acid is due to the silencing of the expression of the genes encoding the transporters for these compounds due to point mutations in the transcriptional regulatory proteins. In contrast, its inability to utilize glucarate or galactarate is due to the presence of point mutations in the transporter and enzymes necessary for the metabolism of these sugars. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted S. enterica serovars and highlight a limitation of bioinformatic approaches to predict metabolic capabilities.

IMPORTANCE

Salmonella enterica serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars can only infect the human host, where they can cause life-long persistent infection. Because of their adaptation to the human host, these bacterial pathogens have changed their metabolism, leading to the loss of their ability to utilize certain nutrients. In this study we examined the functionality of metabolic pathways that appear intact in S. Typhi but that show clear signs of degradation in S. Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in S. Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted S. enterica serovars.

Antibacterial activity of Shallots (Allium xwakegi Araki.) cultivars in Palu Valley against Salmonella Typhi ATCC 27870 through in vitro and in silico evaluation

Background and Objectives

Shallots, recognized for their minimal toxicity, cost-effectiveness, and widespread availability, are increasingly considered a viable source of biological activity. This study evaluates the antibacterial efficacy of a specific shallot cultivar from Palu Valley, Indonesia, against Salmonella typhi, the pathogen responsible for typhoid fever.

Materials and Methods

Utilizing thin-layer chromatography (TLC-bioautography) and gas chromatography-mass spectroscopy (GC-MS), the study identifies active compounds in shallot ethanol extract and employs molecular docking to assess interactions between receptors and ligands.

Results

Findings indicate significant antibacterial activity, with a notable inhibition zone diameter of 31.5 mm at spot Rf 0.28 in TLC bioautography and an optimum concentration of 2% yielding an average clear zone diameter of 28.27 mm in the agar diffusion test. GC-MS analysis reveals 41 compounds, predominantly dodecanoic acid and 1,2,3-propanetriyl ester. Additionally, molecular docking reveals the lowest binding affinity (-7.3 kcal/mol) for Ergost-8-En-3-Ol, 14-Methyl-, (3.Beta,5. Alpha.) against DNA gyrase.

Conclusion

This study confirms Palu Valley shallot extract's potent antibacterial effect against Salmonella typhi, highlighting its therapeutic potential.

Molecular Prediction and Correlation of the Structure and Function of Universal Stress Protein A (UspA) from Salmonella Typhimurium

Salmonella Typhimurium (ST) is a zoonotic pathogen that can cause gastroenteritis in humans when they consume contaminated food or water. When exposed to various stressors, both from living organisms (biotic) and the environment (abiotic), Salmonella Typhimurium produces Universal Stress Proteins (USPs). These proteins are gaining recognition for their crucial role in bacterial stress resistance and the ability to enter a prolonged state of growth arrest. Additionally, USPs exhibit diverse structures due to the fusion of the USP domain with different catalytic motifs, enabling them to participate in various reactions and cellular activities during stressful conditions. In this particular study, researchers cloned and analyzed the uspA gene obtained from poultry-derived strains of Salmonella Typhimurium. The gene comprises 435 base pairs, encoding a USP family protein consisting of 144 amino acids. Phylogenetic analysis demonstrated a close relationship between the uspA genes of Salmonella Typhimurium and those found in other bacterial species. We used molecular dynamics simulations and 3D structure prediction to ensure that the USPA protein was stable. Furthermore, we also carried out motif search and network analysis of protein-protein interactions. The findings from this study offer valuable insights for the development of inhibitors targeted against Salmonella Typhimurium.

Tracking the shift in enteric fever trends and evolving antibiotic sensitivity patterns

Objective

This study aims to examine the frequency of Salmonella Paratyphi found in blood cultures and evaluate the antibiotic susceptibility pattern of Salmonella isolates to different antibiotics. Additionally, the study aims to assess the paradigm shift in the trend of enteric fever caused by Salmonella Typhi (S. Typhi) to Salmonella Paratyphi(S. Paratyphi) .

Study Design

Retrospective study.

Participant

The study enrolled patients aged 12 years and above diagnosed with enteric fever (positive blood culture) and admitted to Peelamedu Samanaidu Govindasamy Naidu (PSG) Hospital.

Interventions

The study analyzed demographic and antibiotic susceptibility profiles of Salmonella isolates collected from 106 enteric fever patients in the hospital between 2010 and 2022. The susceptibility profiles of Salmonella isolates to multiple antibiotics were assessed.

Results

There were 106 participants, and 95 (89.62%) of them had enteric fever linked to Salmonella Typhi, while only 11 (10.38%) had enteric fever linked to Salmonella Paratyphi A. From 2010 to 2022, the study discovered a general decline in the prevalence of enteric fever caused by Salmonella species. But between 2014 and 2022, the incidence of enteric fever linked to S. Typhi rapidly increased. Azithromycin (100% , n = 106) and ceftriaxone (99% , n = 105) were highly effective against the Salmonella isolates, whereas nalidixic acid was resisted by 3 isolates (4.72%, n = 3).

Conclusion

The study observed a higher incidence of Salmonella Typhi in comparison to Paratyphi A and a greater susceptibility of males to enteric fever.

Funding

None declared.

Underestimated economic and social burdens of non-Typhoidal Salmonella infections: The One Health perspective from Nigeria

Background

The non-typhoidal salmonellosis (NTS) is a pathogenic bacterial zoonosis with substantial but often under-appreciated public health impacts. The NTS is prevalent in poultry and humans in Nigeria, yet its economic and social burden have not been determined through any empirical study. To bridge the gap, we evaluated the impact of NTS in social and economic terms.

Methods

Relevant population, economic and epidemiological data were retrieved from peer-reviewed publications, open sources and relevant authorities. Additional data were obtained through experts' opinions and field surveys. Using a customized and validated Microsoft Excel® tool, economic analysis was conducted.

Results

Using the year 2020 reference point, the burden of NTS was 325,731 cases and a total of 1043 human deaths, at a disability-adjusted life year (DALYs) of 37,321. The cost associated with infection in humans was US$ 473,982,068. A total loss of US$ 456,905,311 was estimated in poultry including the direct value of animal loss, US$ 224,236,769, loss from salvage slaughter and culling, US$ 220,386,556, and value of foregone production, US$ 12,281,987.

Interpretation

The outcomes of this important work provide empirical evidence to support informed decisions and investments in the control and eradication of human and poultry salmonellosis (NTS) in Nigeria.

The evolutionary diversification of the Salmonella artAB toxin locus

Salmonella enterica is a diverse species of bacterial pathogens comprised of >2,500 serovars with variable host ranges and virulence properties. Accumulating evidence indicates that two AB₅-type toxins, typhoid toxin and ArtAB toxin, contribute to the more severe virulence properties of the Salmonella strains that encode them. It was recently discovered that there are two distinct types of artAB-like genetic elements in Salmonella: those that encode ArtAB toxins (artAB elements) and those in which the artA gene is degraded and the ArtB homolog, dubbed PltC, serves as an alternative delivery subunit for typhoid toxin (pltC elements). Here, we take a multifaceted approach to explore the evolutionary diversification of artAB-like genetic elements in Salmonella. We identify 7 subtypes of ArtAB toxins and 4 different PltC sequence groups that are distributed throughout the Salmonella genus. Both artAB and pltC are encoded within numerous diverse prophages, indicating a central role for phages in their evolutionary diversification. Genetic and structural analyses revealed features that distinguish pltC elements from artAB and identified evolutionary adaptations that enable PltC to efficiently engage typhoid toxin A subunits. For both pltC and artAB, we find that the sequences of the B subunits are especially variable, particularly amongst amino acid residues that fine tune the chemical environment of their glycan binding pockets. This study provides a framework to delineate the remarkably complex collection of Salmonella artAB/pltC-like genetic elements and provides a window into the mechanisms of evolution for AB₅-type toxins.

Estimating the economic burden of typhoid in children and adults in Blantyre, Malawi: A costing cohort study

BACKGROUND

Typhoid causes preventable death and disease. The World Health Organization recommends Typhoid Conjugate Vaccine for endemic countries, but introduction decisions depend on cost-effectiveness. We estimated household and healthcare economic burdens of typhoid in Blantyre, Malawi.

METHODS

In a prospective cohort of culture-confirmed typhoid cases at two primary- and a referral-level health facility, we collected direct medical, non-medical costs (2020 U.S. dollars) to healthcare provider, plus indirect costs to households.

RESULTS

From July 2019-March 2020, of 109 cases, 63 (58%) were <15 years old, 44 (40%) were inpatients. Mean hospitalization length was 7.7 days (SD 4.1). For inpatients, mean total household and provider costs were $93.85 (95%CI: 68.87-118.84) and $296.52 (95%CI: 225.79-367.25), respectively. For outpatients, these costs were $19.05 (95%CI: 4.38-33.71) and $39.65 (95%CI: 33.93-45.39), respectively. Household costs were due mainly to direct non-medical and indirect costs, medical care was free. Catastrophic illness cost, defined as cost >40% of non-food monthly household expenditure, occurred in 48 (44%) households.

CONCLUSIONS

Typhoid can be economically catastrophic for families, despite accessible free medical care. Typhoid is costly for government healthcare provision. These data make an economic case for TCV introduction in Malawi and the region and will be used to derive vaccine cost-effectiveness.

Multiple immunodominant O-epitopes co-expression in live attenuated Salmonella serovars induce cross-protective immune responses against S. Paratyphi A, S. Typhimurium and S. Enteritidis

Salmonella enterica subsp. enterica (S. enterica) is a significant public health concern and is estimated to cause more than 300,000 deaths annually. Nowadays, the vaccines available for human Salmonellosis prevention are all targeting just one serovar, i.e., S. Typhi, leaving a huge potential risk of Salmonella disease epidemiology change. In this study, we explored the strategy of multiple immunodominant O-epitopes co-expression in S. enterica serovars and evaluated their immunogenicity to induce cross-immune responses and cross-protections against S. Paratyphi A, S. Typhimurium and S. Enteritidis. We found that nucleotide sugar precursors CDP-Abe and CDP-Par (or CDP-Tyv) could be utilized by S. enterica serovars simultaneously, exhibiting O2&O4 (or O4&O9) double immunodominant O-serotypes without obvious growth defects. More importantly, a triple immunodominant O2&O4&O9 O-serotypes could be achieved in S. Typhimurium by improving the substrate pool of CDP-Par, glycosyltransferase WbaV and flippase Wzx via a dual-plasmid overexpressing system. Through immunization in a murine model, we found that double or triple O-serotypes live attenuated vaccine candidates could induce significantly higher heterologous serovar-specific antibodies than their wild-type parent strain. Meanwhile, the bacterial agglutination, serum bactericidal assays and protection efficacy experiments had all shown that these elicited serum antibodies are cross-reactive and cross-protective. Our work highlights the potential of developing a new type of live attenuated Salmonella vaccines against S. Paratyphi A, S. Typhimurium and S. Enteritidis simultaneously.

Salmonella Paratyphi and multiorgan dysfunction: A rare case report

Salmonella typhi (S. typhi) and Salmonella paratyphi A (S. paratyphi A), together known as typhoidal Salmonella, are causal agents for an invasive, serious, and sometimes fatal disease of humans called typhoid fever or paratyphoid fever (also known as enteric fever). S. Typhi, the lineage causing typhoid fever, is the main group; whereas S. Paratyphi A, the lineage causing paratyphoid fever, belongs to the second group, which comprises a set of three paratyphoid types (the other two being S. Paratyphi C and d-tartrate-negative S. Paratyphi B). All these lineages are adapted to humans, with S. Typhi and S. Paratyphi A being strictly restricted to growth in humans, and S. Paratyphi C being able to establish infections in experimental animals quite easily (at moderate infection doses); the host-restriction status of d-tartrate-negative S. Paratyphi B is so far unclear. The potential source of infection is the use of sewage-contaminated water in plants and vegetable irrigation and clinical presentation is varied, mainly presenting with fever, malaise, abdominal discomfort, and nonspecific symptoms often confused with other causes of the febrile syndrome. S. Paratyphi is usually a mild form of disease without any complication, but we report a complicated case of Paratyphi, who presented with fever and gastrointestinal symptoms complicated by multiorgan dysfunction needing mechanical ventilatory support, multiple hemodialysis, and blood transfusion. Fortunately, he recovered from all the insults and was discharged home in stable condition on the 26^th day of hospitalization.

Epidemiology, Serotype and Resistance of Salmonella Isolates from a Children's Hospital in Hangzhou, Zhejiang, China, 2006-2021

Purpose

This research investigated the dynamics of antibiotic resistance in Salmonella and the epidemiology of Salmonella infection in children. These data can aid in the prevention and control of the Salmonella epidemic and the diagnosis and treatment of salmonellosis.

Methods

In this study, we retrospectively reviewed and analysed data regarding epidemiology, clinical symptoms, Salmonella serotypes, and antibiotic resistance from the medical records of patients with Salmonella infections in Hangzhou Children’s Hospital from April 2006 to December 2021.

Results

A total of 2099 Salmonella isolates were identified during the 16-year study period, and 98.6% (2069) of the isolates were isolated from stool. About 84.5% (1773/2099) of the total Salmonella isolates were detected from May to October. The median age of the 2099 children with Salmonella infection was 1.4 years (17 months) (IQR: 0.9–2.8 years). In 1572 (74.9%) patients, the course of the disease was limited to uncomplicated gastroenteritis. S. Typhimurium (805/2099, 38.4%) was predominant, followed by S. Enteritidis (290/2099, 13.8%). The total number of serotypes and the number of less common serotypes are increasing. Nontyphoid Salmonella that cause invasive infections, including S. Typhimurium, S. Stanley, and S. Choleraesuis, accounted for 60.0% (18/30). The Salmonella strains were resistant to ampicillin, ampicillin-sulbactam, trimethoprim-sulfamethoxazole, ceftriaxone, and ciprofloxacin at percentages of 71.5%, 51.5%, 36.5%, 22.4%, and 14.7%, respectively. No imipenem-resistant strains were identified. 24.8% of the isolates exhibited multidrug resistance (MDR).

Conclusion

S. typhimurium and S. enteritidis were the dominant serotypes in children (<2 years) with salmonella-infected arrhoea in Hangzhou, China. Ongoing serotype monitoring should be necessitated and dynamic changes in serotypes should be carefully examined to prevent the sudden outbreak of foodborne illness. Salmonella exhibits a higher rate of resistance to common antibiotics, and the risk of multidrug resistance should not be ignored. Therefore, clinicians should administer antibiotics judiciously according to the results of drug sensitivity tests.

Bacteriophage therapy of human restricted Salmonella Species- A study in a surrogate bacterial and animal model

Salmonella Typhi has been an important human restricted pathogen from time immemorial, and unfortunately, the indiscriminate use of antibiotics has induced the emergence of Multidrug-resistance in S. Typhi. Bacteriophage therapy may be a possible alternative in countering antimicrobial resistance. Therefore, this study was planned to assess the efficacy of bacteriophages in treating acute and chronic S. Typhimurium infection in the mouse as a surrogate model. We isolated bacteriophages against S. Typhimurium and selected three different bacteriophages for the in vivo experiments. The lethal dose of S. Typhimurium was decided for Swiss albino mice, and acute infection was developed. Further, bacteriophage therapy by daily intraperitoneal injection of phage cocktail was given for 14 days. While the chronic carrier state of S. Typhimurium in Swiss albino mice was developed by inoculating intraperitoneally sequential 10 fold increasing doses of the bacterium. On the successful establishment of carrier state, oral feeding of phage cocktail at a high count was given, which completely cured the carrier state in 7 days of feeding. These experiments confirmed that the phage cocktail could eradicate the S. Typhimurium from the mice in both types of infections, i.e., acute and chronic.

Typhoid toxin sorting and exocytic transport from Salmonella Typhi-infected cells

Typhoid toxin is an essential virulence factor for Salmonella Typhi, the cause of typhoid fever in humans. This toxin has an unusual biology in that it is produced by Salmonella Typhi only when located within host cells. Once synthesized, the toxin is secreted to the lumen of the Salmonella-containing vacuole from where it is transported to the extracellular space by vesicle carrier intermediates. Here, we report the identification of the typhoid toxin sorting receptor and components of the cellular machinery that packages the toxin into vesicle carriers, and exports it to the extracellular space. We found that the cation-independent mannose-6-phosphate receptor serves as typhoid toxin sorting receptor and that the coat protein COPII and the GTPase Sar1 mediate its packaging into vesicle carriers. Formation of the typhoid toxin carriers requires the specific environment of the Salmonella Typhi-containing vacuole, which is determined by the activities of specific effectors of its type III protein secretion systems. We also found that Rab11B and its interacting protein Rip11 control the intracellular transport of the typhoid toxin carriers, and the SNARE proteins VAMP7, SNAP23, and Syntaxin 4 their fusion to the plasma membrane. Typhoid toxin's cooption of specific cellular machinery for its transport to the extracellular space illustrates the remarkable adaptation of an exotoxin to exert its function in the context of an intracellular pathogen.

Antimicrobial Resistance Among Pathogens Causing Bloodstream Infections: A Multicenter Surveillance Report Over 20 Years (1998–2017)

Purpose

Bloodstream infections (BSIs) are a common consequence of infectious diseases and cause high morbidity and mortality. Appropriate antibiotic use is critical for patients’ treatment and prognosis. Long-term monitoring and analysis of antimicrobial resistance are important in guiding physicians to choose appropriate antibiotics and understand the changes in antimicrobial resistance and infection control. Here, we report a retrospective study on the trends of antimicrobial resistance in the common BSI-associated pathogens.

Methods

The identification of strains and antimicrobial susceptibility tests were performed in each anticipating hospital independently. Data from the Hubei Province Antimicrobial Resistance Surveillance System (HBARSS) from 1998 to 2017 were retrospectively analyzed using WHONET 5.6 software.

Results

Data from HBARSS (1998–2017) revealed that 40,518 Gram-positive bacteria and 26,568 Gram-negative bacteria caused BSIs, the most common of which were Staphylococcus aureus and Escherichia coli. Salmonella typhi was a predominant BSI-associated pathogen in 1998–2003. Antimicrobial susceptibility data showed that the resistance rates of E. coli and Klebsiella pneumoniae to cefotaxime were significantly higher than those to ceftazidime. The proportion of strains of special antimicrobial resistance phenotypes including difficult-to-treat resistance (DTR), carbapenem-resistant (CR), extended-spectrum cephalosporin resistant (ECR) and fluoroquinolone resistant (FQR) in E. coli was 0.18%, 0.26%, 13.95%, 22.78% while in K. pneumoniae was 11.95%, 14.00%, 31.91% and 11.40%, respectively. In 2013–2017, K. pneumoniae showed resistance levels reaching 15.8% and 17.5% to imipenem and meropenem, respectively, and Acinetobacter baumannii showed high resistance rates ranging from 60 to 80% to common antibiotics. The detection rate of Salmonella typhi resistance to third-generation cephalosporins and fluoroquinolones was less than 5%. Control of methicillin-resistant Staphylococcus aureus (MRSA) remains a major challenge, and in 2009–2017, the MRSA detection rate was 40–50%.

Conclusion

Prevalence of CR K. pneumoniae has increased significantly in recent years. Resistance rates of A. baumannii to common antimicrobial agents have increased exponentially, reaching high levels. MRSA remains a challenge to control. For K. pneumoniae, DTR, CR, ECR and FQR were antimicrobial resistance phenotypes that could not be ignored while for E. coli DTR and CR were rare antimicrobial resistance phenotypes. CR K. pneumoniae, A. baumannii and MRSA present major challenges for controlling BSIs.

Antimicrobial Resistance in Salmonella Typhi Isolated From a Referral Hospital of Kathmandu, Nepal

Purpose:

The morbidity and mortality due to typhoid fever can be significantly reduced with the use of effective antibiotics. At present, fluoroquinolones, third generation cephalosporins, and azithromycin are widely used to treat typhoid fever. However, changing antibiotic susceptibility among Salmonella Typhi and Salmonella Paratyphi poses a particular challenge to the therapeutic management of enteric fever. The objective of this study was to assess the antibiotic susceptibility pattern of Salmonella Typhi isolates.

Patients and Methods:

A total of 706 blood specimens were collected from febrile patients attending the outpatient department of Kathmandu Model Hospital during June to September, 2018. The antibiotic susceptibility testing for 11 different antibiotics (nalidixic acid, ciprofloxacin, ofloxacin, levofloxacin, cefixime, ceftriaxone, cefotaxime, azithromycin, cotrimoxazole, chloramphenicol, and amoxicillin) was performed by disk diffusion method. Furthermore, minimum inhibitory concentration (MIC) values of ciprofloxacin, ofloxacin, and azithromycin were determined by agar dilution method. Mutation at gyrA ser83 associated with reduced susceptibility to fluoroquinolones was determined by PCR-RFLP.

Results:

Out of 706 blood samples, 6.94% (n = 49) were culture positive for Salmonella enterica (S. Typhi, n = 46). It was revealed that 97.8% S. Typhi isolates were susceptible to conventional first-line antibiotics (ampicillin, chloramphenicol, and cotrimoxazole), 97.3% to cephalosporins and 95.7% to azithromycin. S. Typhi were either resistant or intermediately susceptible to fluoroquinolones: 97.8% to ciprofloxacin, 91.3% to ofloxacin, and 89.1% to levofloxacin. The MIC of ciprofloxacin, ofloxacin, and azithromycin for S. Typhi ranged from 0.008 to 32, 0.03 to 16, and 2 to 8 μg/mL, respectively. Out of 46 S. Typhi isolates, 44 (95.65%) had gyrA ser83 mutation.

Conclusion:

Fluoroquinolones have poor activity against Salmonella Typhi. The trends of increasing azithromycin MIC value among S. Typhi might limit its use for the treatment of typhoid fever. Effectiveness of conventional first-line antibiotics in vitro suggests considering their clinical use after large-scale studies.

Prevalence, probability, and outcomes of typhoidal/non-typhoidal Salmonella and malaria co-infection among febrile patients: a systematic review and meta-analysis

The geographical overlaps of malaria parasites and Salmonella spp. can lead to co-infection of these two pathogens, especially in the tropics where malaria is endemic. Moreover, few literatures suggested that malaria infection was associated with Salmonella bacteremia. Therefore, this study quantified pooled prevalence of typhoidal/non-typhoidal Salmonella (NTS) and probability of typhoidal/NTS and malaria co-infection among febrile patients. The systematic review protocol was registered at PROSPERO (CRD42021252322). Studies on co-infection of typhoidal/NTS and malaria were searched in PubMed, Scopus, and Web of Science. The risk of bias of the included studies was assessed using the checklist for analytical cross-sectional studies developed by the Joanna Briggs Institute. Meta-analyses on the following criteria were performed: (1) pooled prevalence of typhoidal/NTS and malaria co-infection among febrile patients, (2) pooled prevalence of typhoidal/NTS among malaria patients, (3) pooled prevalence of malaria infections among patients with Salmonella spp. infection, and (4) probability of typhoidal/NTS and malaria co-infection among febrile patients. Additionally, the case fatality rate and mean difference of malarial parasitemia between typhoidal/NTS and malaria co-infection and Plasmodium monoinfection were also determined. The subgroup analyses of typhoidal/NTS, regions (Africa and Asia), countries, time (publication year), characteristics of participants, and diagnostic tests for identifying Salmonella spp. were also conducted. A sensitivity test was performed to determine the robustness of the study outcomes. Publication bias among the included studies was evaluated using the funnel plot and Egger’s test. All analyses were performed using Stata version 15 (StataCorp LLC, Texas, USA) with a p-value < 0.05 indicating statistical significance. Eighty-one studies that met the eligibility criteria were included in the analyses. Of the 73,775 study participants, 4523 had typhoidal/NTS and malaria co-infections. The pooled prevalence rates of typhoidal/NTS and malaria co-infection among febrile patients were 14% (95% confidence interval [CI], 9–19%; I², 99.4%; 2971/17,720 cases) and 1% (95% CI 1–1%; I², 89.9%; 252/29,081 cases) using the Widal test and culture methods for identifying Salmonella spp., respectively. The pooled prevalence rates of typhoidal/NTS infection among patients with malaria were 31% (95% CI 23–39%; I², 99.5%; 3202/19,208 cases) and 3% (95% CI 2–3%; I², 86.8%; 407/40,426 cases) using the Widal test and culture methods for identifying Salmonella spp., respectively. The pooled prevalence rates of malaria infection among patients with typhoidal/NTS were 17% (95% CI 6–29%; I², 33.3%; 13/75 cases) and 43% (95% CI 32–53%; I², 89.1%; 287/736 cases), respectively. Malaria infection was associated with typhoidal/NTS in children aged < 15 years (p < 0.0001; odds ratio, 0.36; 95% CI 0.23–0.58; I², 73.9%; 3188/43,212 cases). The case fatality rate in patients with malaria and NTS co-infections was 16% (95% CI 9–24%; I², 89.1%; 18/103 cases). From the view of the present study, the inappropriate use of the Widal test for Salmonella spp. diagnosis can overestimate the prevalence of typhoidal/NTS and malaria co-infections. Malaria infection associated with typhoidal/NTS in children and the high case fatality rates among few patients with co-infections were highlighted. Future prospective longitudinal studies using the appropriate and confirmatory dsiagnosis for Salmonella spp. infections are highly recommended to ensure the real prevalence of co-infection and highlight the outcome of co-infection for providing adequate treatment in febrile patients who live in areas where malaria is endemic, such as tropical Africa and India.

Epidemiological Investigation of Salmonella enterica Isolates in Children with Diarrhea in Chengdu, China

Background: Children with the immature intestinal immune system are prone to Salmonella infection through the fecal-oral route causing diarrhea. Non-typhoid Salmonella (NTS) is difficult to treat and eliminate due to its zoonosis. Salmonella typhi, including typhoid and paratyphoid A, B, and C, only infect humans and cause invasive infectious diseases. Salmonella typhi infection is serious and requires antibiotic treatment. The bacterial resistance caused by conventional antibacterial drugs brings great difficulties to treatment. Objectives: This study aimed to investigate the epidemiology of S. enterica in children with diarrhea in Chengdu, China. Methods: Fresh stool specimens or rectal swabs from 6656 children aged 1 day to 13 years with diarrhea were collected, cultured, identified, and tested for antimicrobial susceptibility. Analytical Profile index 20E was used for biochemical identification, and the Kirby-Bauer method was used for the bacterial sensitivity test. The whole process was conducted in accordance with the fourth edition of the National Clinical Examination procedures, and the drug sensitivity test was conducted in accordance with the Clinical and Laboratory Standards Institute 2020 guidelines. Results: A total of 649 Salmonella strains were isolated from 6656 children with suspected Salmonella infection, among which the isolation rates of NTS and S. typhi were 8.92% and 0.83%, respectively. The infection rate of S. typhimurium was the highest every year (74.88%). Salmonella infections are on the rise, especially typhimurium, Dublin, Typhi, and London. Paratyphi is unstable, presenting a phenomenon of transition and replacement (the male to female ratio:1.12:1). The infection rate was the lowest within 1 day and 6 months (P < 0.05). Salmonella mainly infected children under 3 years of age, and the positive rate was reported as 88.29%. Within June-September, the infection rate of Salmonella was the highest, with a positive rate of 72.73%. The isolated 649 Salmonella strains had good susceptibility to cefotaxime and ciprofloxacin (87.67% and 79.20%, respectively), almost no susceptibility to ampicillin, and a drug resistance rate of 92.91%. Conclusions: The typhoid and paratyphoid vaccines should be considered together, and vaccines should focus on children under 3 years of age. Antibiotics should be rationally selected according to the drug sensitivity test and disease condition.

Salmonella Typhimurium and inflammation: a pathogen-centric affair

Microbial infections are controlled by host inflammatory responses that are initiated by innate immune receptors after recognition of conserved microbial products. As inflammation can also lead to disease, tissues that are exposed to microbial products such as the intestinal epithelium are subject to stringent regulatory mechanisms to prevent indiscriminate signalling through innate immune receptors. The enteric pathogen Salmonella enterica subsp. enterica serovar Typhimurium, which requires intestinal inflammation to sustain its replication in the intestinal tract, uses effector proteins of its type III secretion systems to trigger an inflammatory response without the engagement of innate immune receptors. Furthermore, S. Typhimurium uses a different set of effectors to restrict the inflammatory response to preserve host homeostasis. The S. Typhimurium-host interface is a remarkable example of the unique balance that emerges from the co-evolution of a pathogen and its host.

Incidence and Risk Factors for Notifiable Typhoid and Paratyphoid in Taiwan during the Period 2011-2020

The risk of the geographic transmission of emerging infectious diseases through air travel varies greatly. In this study, we collected data on cases of food-borne diseases between the years 2011 and 2020 in Taiwan to access the epidemiological features, differences, and trends in domestic and imported cases of typhoid and paratyphoid in terms of patient sex, age, month of confirmation, and area of residence. In this study, we made use of the open data website provided by Taiwan’s Centers for Disease Control (TCDC) to extract the reported numbers of cases of typhoid and paratyphoid between January and December from 2011 to 2020 for comparison. Univariate analysis was performed using the Chi-square test for categorical variables. Fisher’s exact test was performed if an expected frequency was less than 5. A total of 226 typhoid cases and 61 paratyphoid cases were analyzed from the database. The incidences of typhoid and paratyphoid per million of the population were 0.42–2.11 and 0–0.39, respectively. There was a significant difference in the incidence of the diseases between the age groups (p = 0.019), with a gradual increase in the 20–40 years group. A distinct seasonal (between fall and spring) variation was also observed (p = 0.012). There were 34 cases of children with typhoid in the period 2011–2015 and 12 cases of children with typhoid in the period 2016–2020. During these periods, there were two cases of paratyphoid. This study indicated that the risk of children suffering from typhoid has been significantly reduced in the last five years. Furthermore, we found that more women have acquired typhoid and paratyphoid than men, and that living in the Taipei metropolitan area and the northern area was a potential risk factor. Furthermore, the number of imported cases of typhoid (n = 3) and paratyphoid (n = 0) reported during the COVID-19 pandemic was lower than that reported for the same disease from 2011 to 2020. More typhoid and paratyphoid cases were imported from Indonesia, India, Myanmar, and Cambodia. This study represents the first report on confirmed cases of acquired typhoid and paratyphoid from surveillance data from Taiwan’s CDC for the period 2011–2020. This study also demonstrates that the cases of typhoid and paratyphoid decreased in Taiwan during the COVID pandemic. Big data were used in this study, which may inform future surveillance and research efforts in Taiwan.

Increasingly limited options for the treatment of enteric fever in travellers returning to England, 2014-2019: a cross-sectional analytical study

Introduction. Enteric fever (caused by Salmonella enterica serovars Typhi and Paratyphi) frequently presents as an acute, undifferentiated febrile illness in returning travellers, requiring timely empirical antibiotics.Gap Statement. Determining which empirical antibiotics to prescribe for enteric fever requires up-to-date knowledge of susceptibility patterns.Aim. By characterising factors associated with antimicrobial resistance in cases of S. Typhi and S. Paratyphi imported to England, we aim to guide effective empirical treatment.Methodology. All English isolates of S. Typhi and S. Paratyphi 2014-2019 underwent antimicrobial susceptibility testing; results were compared to a previous survey in London 2005-2012. Risk factors for antimicrobial resistance were analysed with logistic regression models to predict adjusted odds ratios (aOR) for resistance to individual antibiotics and multi-drug resistance.Results. We identified 1088 cases of S. Typhi, 729 S. Paratyphi A, 93 S. Paratyphi B, and one S. Paratyphi C. In total, 93 % were imported. Overall, 90 % of S. Typhi and 97 % of S. Paratyphi A isolates were resistant to ciprofloxacin; 26 % of S. Typhi were multidrug resistant to ciprofloxacin, amoxicillin, co-trimoxazole, and chloramphenicol (MDR+FQ). Of the isolates, 4 % of S. Typhi showed an extended drug resistance (XDR) phenotype of MDR+FQ plus resistance to third-generation cephalosporins, with cases of XDR rising sharply in recent years (none before 2017, one in 2017, six in 2018, 32 in 2019). For S. Typhi isolates, resistance to ciprofloxacin was associated with travel to Pakistan (aOR=32.0, 95 % CI: 15.4-66.4), India (aOR=21.8, 95 % CI: 11.6-41.2), and Bangladesh (aOR=6.2, 95 % CI: 2.8-13.6) compared to travel elsewhere, after adjusting for rising prevalence of resistance over time. MDR+FQ resistance in S. Typhi isolates was associated with travel to Pakistan (aOR=3.5, 95 % CI: 2.4-5.2) and less likely with travel to India (aOR=0.07, 95 % CI 0.04-0.15) compared to travel elsewhere. All XDR cases were imported from Pakistan. No isolate was resistant to azithromycin. Comparison with the 2005-2012 London survey indicates substantial increases in the prevalence of resistance of S. Typhi isolates to ciprofloxacin associated with travel to Pakistan (from 79-98 %) and Africa (from 12-60 %).Conclusion. Third-generation cephalosporins and azithromycin remain appropriate choices for empirical treatment of enteric fever in most returning travellers to the UK from endemic countries, except from Pakistan, where XDR represents a significant risk.

Invasive nontyphoidal Salmonella infection in a patient with Roux-en-Y gastric bypass and gastrostomy tube: a case report

Background

Infections with nontyphoidal Salmonella most commonly cause a self-limited gastroenteritis in humans and are the leading source of foodborne illness. In the USA, the incidence of culture-confirmed invasive Salmonella is extremely rare. Here, we present a unique case of enteric nontyphoidal Salmonella enteritidis infection that progressed to an invasive bacteremia in a patient with Roux-en-Y gastric bypass and gastrostomy feeding tube.

Case presentation

A 58-year-old Caucasian woman with a past medical history of Roux-en-Y gastric bypass with revision and recent gastrostomy feeding tube insertion was admitted with fever and diarrhea. During her inpatient stay, two sets of blood cultures grew Salmonella enteritidis and she was promptly treated with intravenous antibiotics. Her hospital course was also complicated by acute kidney injury. The patient recovered after treatment with a third-generation cephalosporin and supportive treatment.

Conclusion

We present an unusual case of nontyphoidal Salmonella enteritidis bacteremia complicated by acute kidney injury in a middle-aged woman with a previous history of Roux-en-Y gastric bypass and gastrostomy feeding tube insertion. Further investigation is needed to identify whether gastric surgeries or procedures are independent risk factors for invasive nontyphoidal salmonellosis.

A Salmonella Typhi Controlled Human Infection Study for Assessing Correlation between Bactericidal Antibodies and Protection against Infection Induced by Typhoid Vaccination

Vi-polysaccharide conjugate vaccines are efficacious against typhoid fever in children living in endemic settings, their recent deployment is a promising step in the control of typhoid fever. However, there is currently no accepted correlate of protection. IgG and IgA antibodies generated in response to Vi conjugate or Vi plain polysaccharide vaccination are important but there are no definitive protective titre thresholds. We adapted a luminescence-based serum bactericidal activity (SBA) for use with S. Typhi and assessed whether bactericidal antibodies induced by either Vi tetanus toxoid conjugate (Vi-TT) or Vi plain polysaccharide (Vi-PS) were associated with protection in a controlled human infection model of typhoid fever. Both Vi-PS and Vi-TT induced significant increase in SBA titre after 28 days (Vi-PS; p < 0.0001, Vi-TT; p = 0.003), however higher SBA titre at the point of challenge did not correlate with protection from infection or reduced symptom severity. We cannot eliminate the role of SBA as part of a multifactorial immune response which protects against infection, however, our results do not support a strong role for SBA as a mechanism of Vi vaccine mediated protection in the CHIM setting.

Bacteriostatic and Bactericidal Activities of Camel Lactoferrins Against Salmonella enterica Serovar Typhi

Lactoferrin is an iron-binding glycoprotein present in various secretions (e.g., milk, tears, saliva, pancreatic juice), which performs multiple functions, with one of them being the antimicrobial defense. Purified camel lactoferrins (cLfs) from different Saudi camel clans, as well as human and bovine lactoferrins (hLf or bLf) were tested as antimicrobial agents against Salmonella enterica serovar Typhi (S. Typhi). All cLfs showed superior antibacterial potentials relative to hLf or bLf, while there was no noticeable difference in the antimicrobial capabilities between the cLfs from different camel clans. We observed synergy between the inhibitory activities of Lfs and antibiotics against bacterial growth. Expression of numerous bacterial proteins was affected by the treatment with Lf and its combinations, giving insight into the molecular mechanisms of the Lf action. Furthermore, several bacterial proteins were shown to interact with cLf-biotin. Scanning and transmission electron microscopy revealed the presence of obvious extracellular and intracellular changes after S. Typhi treatment by antibiotic (carbenicillin) or cLf alone, and in combination. The effects of antibiotics and Lf were synergistic, supporting the potential of the use of Lf-antibiotic combinations.

Morbidity and Mortality Associated with Typhoid Fever Among Hospitalized Patients in Hyderabad District, Pakistan, 2017-2018: Retrospective Record Review

BACKGROUND

Hyderabad, Pakistan, was the first city to witness an outbreak of extensively drug resistant (XDR) typhoid fever. The outbreak strain is resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, fluoroquinolones, and third-generation cephalosporin, thus greatly limiting treatment options. However, despite over 5000 documented cases, information on mortality and morbidity has been limited.

OBJECTIVE

To address the existing knowledge gap, this study aimed to assess the morbidity and mortality associated with XDR and non-XDR Salmonella serovar Typhi infections in Pakistan.

METHODS

We reviewed the medical records of culture-confirmed typhoid cases in 5 hospitals in Hyderabad from October 1, 2016, to September 30, 2018. We recorded data on age, gender, onset of fever, physical examination, serological and microbiological test results, treatment before and during hospitalization, duration of hospitalization, complications, and deaths.

RESULTS

A total of 1452 culture-confirmed typhoid cases, including 947 (66%) XDR typhoid cases and 505 (34%) non-XDR typhoid cases, were identified. Overall, ≥1 complications were reported in 360 (38%) patients with XDR typhoid and 89 (18%) patients with non-XDR typhoid (P<.001). Ileal perforation was the most commonly reported complication in both patients with XDR typhoid (n=210, 23%) and patients with non-XDR typhoid (n=71, 14%) (P<.001). Overall, mortality was documented among 17 (1.8%) patients with XDR S Typhi infections and 3 (0.6%) patients with non-XDR S Typhi infections (P=.06).

CONCLUSIONS

As this first XDR typhoid outbreak continues to spread, the increased duration of illness before hospitalization and increased rate of complications have important implications for clinical care and medical costs and heighten the importance of prevention and control measures.

Risk Factors of Extensively Drug Resistant Typhoid Fever Among Children in Karachi: Case-Control Study

Background

Extensively drug resistant typhoid fever (XDR-TF) has been responsible for an ongoing outbreak in Pakistan, which began in November 2016.

Objective

This study aimed to determine the risk factors associated with XDR-TF.

Methods

This age- and sex-matched case-control study was conducted during May-October 2018 in Karachi. All patients with XDR-TF were identified from the laboratory-based surveillance system data. Cases included patients aged <15 years living in Karachi with culture-positive Salmonella enterica serovar Typhi with resistance to chloramphenicol, ampicillin, trimethoprim/sulfamethoxazole, fluoroquinolones, and third-generation cephalosporins. Age- and sex-matched controls included children free from the symptoms of TF, aged under 15 years, and residing in Karachi. All controls were recruited from among those who attended outpatient clinics.

Results

A total of 75 cases and 75 controls were included in this study. On univariate analysis, the odds of having XDR-TF were 13-fold higher among participants who used piped municipal water than among those who did not (odds ratio [OR] 12.6, 95% CI 4.1-38.6). The use of bore water was significantly associated with XDR-TF (OR 5.1, 95% CI 1.4-19.0). Cases were more likely to report eating French fries with sauce (OR 13.5, 95% CI 3.9-47.0) and poppadum (OR 3.4, 95% CI 1.7-6.7) from street vendors than controls. Boiling water at home was negatively associated with XDR-TF (OR 0.3, 95% CI 0.2-0.7). On multivariate analysis, 2 factors were independently associated with XDR-TF. Using piped municipal water (OR 10.3, 95% CI 3.4-30.4) and eating French fries with sauce from street vendors (OR 8.8, 95% CI 2.1-36.2) were significantly associated with an increased odds of XDR-TF.

Conclusions

Community water supply and street food eating habits were implicated in the spread of the superbug S typhi outbreak, which continues to grow in Karachi. Therefore, it is recommended to improve the community water supply to meet recommended standards and to develop a policy to improve the safety of street food. In addition, health authorities are required to conduct mass vaccination for TF among high-risk groups.

Seroconfirmed Typhoid Fever and Knowledge, Attitude, and Practices among Febrile Patients Attending at Injibara General Hospital, Northwest Ethiopia

Introduction

Typhoid fever (TF) is a febrile global health problem caused by Salmonella enterica serovar Typhi (S. Typhi) with relatively high prevalence in low- and middle-income countries including Ethiopia. Identifying local prevalence and gaps in knowledge, attitude, and practice (KAP) towards TF is recommended by the World Health Organization to implement preventive measures. Therefore, this study determined the prevalence of S. Typhi and KAP of febrile patients towards TF in Injibara General Hospital, Northwest Ethiopia.

Methods

Hospital-based cross-sectional study was conducted from January to March 2020. A total of 237 patients were included conveniently. Data on KAP and demographic variables were collected using a structured questionnaire by face-to-face interview. After the interview, 5 ml venous blood was collected and processed using the Widal test following the manufacturer's instruction. Mean scores and percentages were used to determine the level of KAP. Multivariable analysis was done to correlate KAPs with TF. P value < 0.05 was considered statistically significant.

Results

The overall prevalence of S. Typhi was 25.7%. The highest seroprevalence was observed among the age group of 30-34 years (33.3%) and patients with no education. The majority of participants know the major ways of TF transmission (59.1-90.7%) and prevention (81.4%) methods. However, the misconception on the route of TF transmission was observed in 13.5-36.7% of participants. About 65.4% and 67.5% of study participants were considered knowledgeable and had good preventive practice towards TF, respectively. Being a student (AOR = 0.227, CI = 0.053 − 0.965) and considering mosquito bite as transmission routes (AOR = 2.618, CI = 1.097 − 6.248) were significantly associated with TF.

Conclusion

High S. Typhi prevalence was observed in the study area. Moreover, the misconception on the transmission of typhoid fever and educational level was a risk factor for TF. Thus, health facilities should incorporate topics on typhoid fever as part of their health education system within health facilities and in the community.

Salmonella Typhi and Salmonella Paratyphi prevalence, antimicrobial susceptibility profile and factors associated with enteric fever infection in Bahir Dar, Ethiopia

Enteric fever (EF) is caused by Salmonella enterica serovars Typhi (S. Typhi) and Paratyphi (S. Paratyphi) causing significant health problems in developing countries including Ethiopia. Thus present study aimed to determine prevalence and antimicrobial resistance profile of S. Typhi and S. Paratyphi among EF suspected patients at Felege-Hiwot comprehensive specialized hospital, Bahir Dar, Ethiopia. Hospital based cross-sectional study was conducted from March-to-May 2020. Totally, 150 patients were included conveniently. Data were collected using questionnaires by face-to-face interview. Concurrently, venous blood and stool specimens were collected and processed following standard bacteriological technique. Antimicrobial susceptibility test (AST) was performed by disc diffusion method. Logistic regression was performed to identify factors associated with EF infection. The study indicated 5.3% EF prevalence where S. Typhi accounted 75%. S. Typhi and S. Paratyphi isolates were 100% sensitive to cephalosporins but at least 83.3% showed resistance against chloramphenicol and tetracycline. At least 66.7% of isolates were multidrug resistance (MDR). Using well water for drinking (AOR = 6.22, CI 1.4-27.5) and previous EF history (AOR = 10.74, CI 2.01-55.9) were significantly associated with EF infection. Thus high bacterial prevalence and MDR isolates was observed. Therefore, health professionals should consider AST and use antibiotics with cautions for EF patient management.

Evaluation of Typhoid Conjugate Vaccine Effectiveness in Ghana (TyVEGHA) Using a Cluster-Randomized Controlled Phase IV Trial: Trial Design and Population Baseline Characteristics

Typhoid fever remains a significant health problem in sub-Saharan Africa, with incidence rates of >100 cases per 100,000 person-years of observation. Despite the prequalification of safe and effective typhoid conjugate vaccines (TCV), some uncertainties remain around future demand. Real-life effectiveness data, which inform public health programs on the impact of TCVs in reducing typhoid-related mortality and morbidity, from an African setting may help encourage the introduction of TCVs in high-burden settings. Here, we describe a cluster-randomized trial to investigate population-level protection of TYPBAR-TCV^®, a Vi-polysaccharide conjugated to a tetanus-toxoid protein carrier (Vi-TT) against blood-culture-confirmed typhoid fever, and the synthesis of health economic evidence to inform policy decisions. A total of 80 geographically distinct clusters are delineated within the Agogo district of the Asante Akim region in Ghana. Clusters are randomized to the intervention arm receiving Vi-TT or a control arm receiving the meningococcal A conjugate vaccine. The primary study endpoint is the total protection of Vi-TT against blood-culture-confirmed typhoid fever. Total, direct, and indirect protection are measured as secondary outcomes. Blood-culture-based enhanced surveillance enables the estimation of incidence rates in the intervention and control clusters. Evaluation of the real-world impact of TCVs and evidence synthesis improve the uptake of prequalified/licensed safe and effective typhoid vaccines in public health programs of high burden settings. This trial is registered at the Pan African Clinical Trial Registry, accessible at Pan African Clinical Trials Registry (ID: PACTR202011804563392).

Geographical distribution of Typhoid using Geographic Information System (GIS) during 2009-2014 in Iran

Background: Salmonella induced infections remain one of the most important health problems worldwide. The purpose of this study is to investigate the incidence and geographical distribution of typhoid using GIS and to predict its incidence in Iran in 2021.

Methods: This study is a descriptive analytical study. Information on pertussis was obtained from the Center for Communicable Diseases Control during 2009-2015. In the next step, ArcGIS 9.3 was used to prepare geographic maps of the disease incidence and frequency Therefore, using the Raster Calculator tool, the disease prediction map was drawn.

Results: The results showed that the highest incidence of typhoid during 2009-2014 was in Kermanshah, Lorestan, Hamadan, Kurdistan, and Ilam provinces. The incidence of typhoid in Iran increased during 2009-2010. The annual incidence of typhoid decreased from 0.85 per 100,000 in 2010 to 0.5 in 2014. Based on the modeling results for Iran, Kermanshah, Lorestan, Kurdistan, Ilam and Hamadan provinces with 92.17%, 46.56%, 31.74%, 25.62% and 22.96% of their areas (Km2) are at high risk for typhoid in the coming years, respectively.

Conclusion: Considering that the provinces of Kermanshah, Lorestan, Kurdistan, Ilam, and Hamadan are at risk of typhoid incidence in the coming years in Iran, and given that salmonella infections have a direct relationship with the individual’s health status and individual’s environmental health and socioeconomic status, improving the health status and disease control in carriers as well as improving the socio-economic status of the population living in these areas can prevent the disease in the years to come.

Extensively drug-resistant Salmonella Typhi in a patient returning from Pakistan, complicated by relapse with meropenem monotherapy

In developing countries, typhoid fever is a common cause of febrile illness accompanied by abdominal pain and weakness. It is caused by Salmonella enterica serovar Typhi. Humans are the only known reservoir of infection, and typhoid fever is common in regions where access to clean water and sanitation is limited. The antimicrobials of choice for a case of typhoid fever acquired outside Pakistan are third generation cephalosporins. Lately, cases of extensively drug-resistant (XDR) Salmonella Typhi have been reported in people with a travel history to Pakistan. We present a case of XDR typhoid fever which relapsed after treatment with meropenem.

Analysis of existence of multidrug-resistant H58 gene in Salmonella enterica serovar Typhi isolated from typhoid fever patients in Makassar, Indonesia

The surveillance of multidrug-resistant (MDR) H58 typhoid is highly important, especially in endemic areas. MDR strain detection is needed by using a simple PCR technique that only uses a pair of primers. This is conducted considering the detection of Salmonella Typhi strains that have been carried out so far are only using antimicrobial sensitivity tests to determine microbial resistance phenotypically and to determine genotypically using complex molecular techniques. We aimed to analyse the existence of Salmonella Typhi MDR H58 in patients with typhoid fever in Makassar, Indonesia. A total of 367 blood samples of typhoid fever patients were collected from April 2018 until April 2019. The blood sample was cultured, then confirmed via simple PCR. All of the confirmed samples were tested for susceptibility against antibiotics and molecularly analysed for MDR H58 existence using a simple PCR technique. We found 7% (27/367) of the samples to be positive by both blood culture and PCR. All 27 isolates were found to be sensitive to sulfamethoxazole/trimethoprim. The lowest drug sensitivities were to amoxicillin, at one (3.7%) of 27 isolates, and ampicillin, at 13 (48.1%) of 27 isolates. Salmonella Typhi H58 PCR results showed that one (3.7%) of 27 isolates carried a positive fragment of 993 bp that led to the H58 strain, since the deletion flanks this fragment. The isolate was also found to be resistant to amoxicillin and fluoroquinolone according to a sensitivity test. Further molecular analysis needs to be conducted to examine the single isolate that carried the 933 bp fragment.

Antimicrobial Sensitivity Pattern of Salmonella Typhi: Emergence of Resistant Strains

Background

Typhoid fever is still an important public health problem in developing countries. Increasing resistance of Salmonella Typhi to antibiotics is alarming. New extensively drug-resistant strains of Salmonella reported first time in Pakistan, resistant not only to first-line drugs and ciprofloxacin but also resistant to ceftriaxone, had spread globally, including the USA. Due to this continuously changing pattern of antimicrobial resistance in typhoid fever due to Salmonella Typhi, there is a substantial need to study the resistance pattern of Salmonella Typhi frequently in different areas to detect the new resistant strains timely. The objective of this study was to evaluate the current trends in the resistance pattern of Salmonella Typhi in a tertiary care hospital in Northern Punjab.

Methods

This cross-sectional study was conducted at the Department of Medicine, Pakistan Ordnance Factories (POF) Hospital Wah Cant in collaboration with the Department of Pathology, from 1^st January 2019 to 30^th September 2019. Culture-positive patients of typhoid fever age more than 12 years, either male or female, were included in the study. The antimicrobial susceptibility of the isolates was determined by the disc diffusion method of Kirby Bauer on Mueller-Hinton agar using Clinical Laboratory Standards Institute (CLSI) guidelines. The antimicrobial agents tested were ampicillin (10 μg), chloramphenicol (30 μg), trimethoprim/sulfamethoxazole (1.25/23.75 μg), ciprofloxacin (5 μg), ceftriaxone (30μg), azithromycin (15μg), imipenem (10μg) and meropenem (10μg).

Results

A total of 81 culture-positive patients were included in the study. Out of these, 59% were male, and 41 % were female. Mean age was 23.8±19.1 years ranging from 12 to 91 years. Salmonella Typhi showed the highest sensitivity to imipenem 100% and azithromycin 95%; the lowest sensitivity was to ciprofloxacin 3.7%. Almost 50% of patients were resistant to ceftriaxone, and 48% were resistant to meropenem. The number of multidrug-resistant cases reported was 20%, whereas 47% of strains were extensively drug-resistant.

Conclusion

Resistance to antimicrobial agents is increasing in patients with typhoid fever due to Salmonella Typhi; especially the extensively drug-resistant strains of Salmonella Typhi are increasing rapidly. New emerging strains resistant to carbapenems found in our study are a big threat. Prescription of antibiotics according to culture and sensitivity for sufficient duration in patients of typhoid fever due to Salmonella Typhi is necessary to prevent the emergence of new resistant strains.

Time series analysis of cumulative incidences of typhoid and paratyphoid fevers in China using both Grey and SARIMA models

Typhoid and paratyphoid fevers are common enteric diseases causing disability and death in China. Incidence data of typhoid and paratyphoid between 2004 and 2016 in China were analyzed descriptively to explore the epidemiological features such as age-specific and geographical distribution. Cumulative incidence of both fevers displayed significant decrease nationally, displaying a drop of 73.9% for typhoid and 86.6% for paratyphoid in 2016 compared to 2004. Cumulative incidence fell in all age subgroups and the 0–4 years-old children were the most susceptible ones in recent years. A cluster of three southwestern provinces (Yunnan, Guizhou, and Guangxi) were the top high-incidence regions. Grey model GM (1,1) and seasonal autoregressive integrated moving average (SARIMA) model were employed to extract the long-term trends of the diseases. Annual cumulative incidence for typhoid and paratyphoid were formulated by GM (1,1) as x^(t)=−14.98(e−0.10(t−2004)−e−0.10(t−2005)) and x^(t)=−4.96(e−0.19(t−2004)−e−0.19(t−2005)) respectively. SARIMA (0,1,7) × (1,0,1)₁₂ was selected among a collection of constructed models for high R² and low errors. The predictive models for both fevers forecasted cumulative incidence to continue the slightly downward trend and maintain the cyclical seasonality in near future years. Such data-driven insights are informative and actionable for the prevention and control of typhoid and paratyphoid fevers as serious infectious diseases.

Safety and immunogenicity of Vi-DT conjugate vaccine among 6-23-month-old children: Phase II, randomized, dose-scheduling, observer-blind Study

BACKGROUND

Typhoid causes significant mortality among young children in resource-limited settings. Conjugate typhoid vaccines could significantly reduce typhoid-related child deaths, but only one WHO-prequalified typhoid conjugate vaccine exists for young children. To address this gap, we investigated the safety, immunogenicity and dose-scheduling of Vi-DT typhoid conjugate vaccine among children aged 6-23 months.

METHODS

In this single center, observer blind, phase II trial, participants were randomly assigned (2:2:1) to receive one or two doses of Vi-DT or comparator vaccine. Anti-Vi IgG titer and geometric mean titers (GMT) were determined at 0, 4, 24 and 28 weeks. Data were analyzed using per-protocol and immunogenicity (a subset of intention-to-treat analysis) sets. The trial is registered with ClinicalTrials.gov (NCT03527355).

FINDINGS

Between April and July 2018, 285 children were randomized; 114 received one or two doses of Vi-DT while 57 received comparator. 277 completed the study follow-up per protocol; 112 and 110 from single- and two-dose Vi-DT schedules, respectively and 55 from the placebo group were included in the per protocol analysis. Safety profile is satisfactory. Thirteen serious adverse events were reported during the 28-week follow-up, none of which were related to Vi-DT. The seroconversion rate four weeks after the first dose was 100% (95% CI 98·3-100) in Vi-DT recipients and 7·0% (95% CI 2·8-16·7) in comparator recipients (p<0·0001). Similarly, the seroconversion rate 4 weeks after the second dose was 98·2% (95% CI 93· 6-99·5) and 21·8% (95% CI 13·0-34·4) among Vi-DT and comparator groups, respectively (p<0·0001). Anti-Vi IgG GMT was significantly higher in Vi-DT than in control group at all post-vaccination visits (p<0·0001).

INTERPRETATION

Both single and two doses of Vi-DT vaccine are safe, well tolerated, and immunogenic for infants and toddlers in a moderately endemic setting.

Spatial and Temporal Patterns of Typhoid and Paratyphoid Fever Outbreaks: A Worldwide Review, 1990-2018

BACKGROUND

Analyses of the global spatial and temporal distribution of enteric fever outbreaks worldwide are important factors to consider in estimating the disease burden of enteric fever disease burden.

METHODS

We conducted a global literature review of enteric fever outbreak data by systematically using multiple databases from 1 January 1990 to 31 December 2018 and classified them by time, place, diagnostic methods, and drug susceptibility, to illustrate outbreak characteristics including spatial and temporal patterns.

RESULTS

There were 180 940 cases in 303 identified outbreaks caused by infection with Salmonella enterica serovar Typhi (S. Typhi) and Salmonella enterica serovar Paratyphi A or B (S. Paratyphi). The size of outbreak ranged from 1 to 42 564. Fifty-one percent of outbreaks occurred in Asia, 15% in Africa, 14% in Oceania, and the rest in other regions. Forty-six percent of outbreaks specified confirmation by blood culture, and 82 outbreaks reported drug susceptibility, of which 54% had multidrug-resistant pathogens. Paratyphoid outbreaks were less common compared to typhoid (22 vs 281) and more prevalent in Asia than Africa. Risk factors were multifactorial, with contaminated water being the main factor.

CONCLUSIONS

Enteric fever outbreak burden remains high in endemic low- and middle-income countries and, despite its limitations, outbreak data provide valuable contemporary evidence in prioritizing resources, public health policies, and actions. This review highlights geographical locations where urgent attention is needed for enteric fever control and calls for global action to prevent and contain outbreaks.

A Multicenter Cost-of-Illness and Long-term Socioeconomic Follow-up Study in the Severe Typhoid Fever in Africa Program: Study Protocol

Background

There are limited data on typhoid fever cost of illness (COI) and economic impact from Africa. Health economic data are essential for measuring the cost-effectiveness of vaccination or other disease control interventions. Here, we describe the protocol and methods for conducting the health economic studies under the Severe Typhoid Fever in Africa (SETA) program.

Methods

The SETA health economic studies will rely on the platform for SETA typhoid surveillance in 4 African countries—Burkina Faso, Ethiopia, Ghana, and Madagascar. A COI and long-term socioeconomic study (LT-SES) will be its components. The COI will be assessed among blood culture–positive typhoid fever cases, blood culture–negative clinically suspected cases (clinical cases), and typhoid fever cases with pathognomonic gastrointestinal perforations (special cases). Repeated surveys using pretested questionnaires will be used to measure out-of-pocket expenses, quality of life, and the long-term socioeconomic impact. The cost of resources consumed for diagnosis and treatment will be collected at health facilities.

Results

Results from these studies will be published in peer-reviewed journals and presented at scientific conferences to make the data available to the wider health economics and public health research communities.

Conclusions

The health economic data will be analyzed to estimate the average cost per case, the quality of life at different stages of illness, financial stress due to illness, and the burden on the family due to caregiving during illness. The data generated are expected to be used in economic analysis and policy making on typhoid control interventions in sub-Saharan Africa.

Generation and Characterization of Typhoid Toxin-Neutralizing Human Monoclonal Antibodies

Typhoid toxin is a virulence factor of Salmonella enterica serovar Typhi, the causative agent of typhoid fever, and is thought to be responsible for the symptoms of severe disease. This toxin has a unique A2B5 architecture with two active subunits, the ADP ribosyl transferase PltA and the DNase CdtB, linked to a pentameric B subunit, which is alternatively made of PltB or PltC. Here, we describe the generation and characterization of typhoid toxin-neutralizing human monoclonal antibodies by immunizing genetically engineered mice that have a full set of human immunoglobulin variable region genes. We identified several monoclonal antibodies with strong in vitro and in vivo toxin-neutralizing activity and different mechanisms of toxin neutralization. These antibodies could serve as the basis for the development of novel therapeutic strategies against typhoid fever.

Emergence of Resistance to Fluoroquinolones and Third-Generation Cephalosporins in Salmonella Typhi in Lahore, Pakistan

Extensively drug-resistant (XDR) Salmonella Typhi has been reported in Sindh province of Pakistan since 2016. The potential for further spread is of serious concern as remaining treatment options are severely limited. We report the phenotypic and genotypic characterization of 27 XDR S. Typhi isolated from patients attending Jinnah Hospital, Lahore, Pakistan. Isolates were identified by biochemical profiling; antimicrobial susceptibility was determined by a modified Kirby–Bauer method. These findings were confirmed using Illumina whole genome nucleotide sequence data. All sequences were compared to the outbreak strain from Southern Pakistan and typed using the S. Typhi genotyping scheme. All isolates were confirmed by a sequence analysis to harbor an IncY plasmid and the CTX-M-15 ceftriaxone resistance determinant. All isolates were of the same genotypic background as the outbreak strain from Sindh province. We report the first emergence of XDR S. Typhi in Punjab province of Pakistan confirmed by whole genome sequencing.

Typhoid Outbreaks, 1989-2018: Implications for Prevention and Control

Typhoid fever remains an important public health problem in low- and middle-income countries, with large outbreaks reported from Africa and Asia. Although the WHO recommends typhoid vaccination for control of confirmed outbreaks, there are limited data on the epidemiologic characteristics of outbreaks to inform vaccine use in outbreak settings. We conducted a literature review for typhoid outbreaks published since 1990. We found 47 publications describing 45,215 cases in outbreaks occurring in 25 countries from 1989 through 2018. Outbreak characteristics varied considerably by WHO region, with median outbreak size ranging from 12 to 1,101 cases, median duration from 23 to 140 days, and median case fatality ratio from 0% to 1%. The largest number of outbreaks occurred in WHO Southeast Asia, 13 (28%), and African regions, 12 (26%). Among 43 outbreaks reporting a mode of disease transmission, 24 (56%) were waterborne, 17 (40%) were foodborne, and two (5%) were by direct contact transmission. Among the 34 outbreaks with antimicrobial resistance data, 11 (32%) reported Typhi non-susceptible to ciprofloxacin, 16 (47%) reported multidrug-resistant (MDR) strains, and one reported extensively drug-resistant strains. Our review showed a longer median duration of outbreaks caused by MDR strains (148 days versus 34 days for susceptible strains), although this difference was not statistically significant. Control strategies focused on water, sanitation, and food safety, with vaccine use described in only six (13%) outbreaks. As typhoid conjugate vaccines become more widely used, their potential role and impact in outbreak control warrant further evaluation.

The Current Status of Enteric Fever Diagnostics and Implications for Disease Control

Enteric (typhoid) fever remains a problem in low- and middle-income countries that lack the infrastructure to maintain sanitation and where inadequate diagnostic methods have restricted our ability to identify and control the disease more effectively. As we move into a period of potential disease elimination through the introduction of typhoid conjugate vaccine (TCV), we again need to reconsider the role of typhoid diagnostics in how they can aid in facilitating disease control. Recent technological advances, including serology, transcriptomics, and metabolomics, have provided new insights into how we can detect signatures of invasive Salmonella organisms interacting with the host during infection. Many of these new techniques exhibit potential that could be further explored with the aim of creating a new enteric fever diagnostic to work in conjunction with TCV. We need a sustained effort within the enteric fever field to accelerate, validate, and ultimately introduce 1 (or more) of these methods to facilitate the disease control initiative. The window of opportunity is still open, but we need to recognize the need for communication with other research areas and commercial organizations to assist in the progression of these diagnostic approaches. The elimination of enteric fever is now becoming a real possibility, but new diagnostics need to be part of the equation and factored into future calculations for disease control.

Review on the Recent Advances on Typhoid Vaccine Development and Challenges Ahead

Control of Salmonella enterica serovar typhi (S. typhi), the agent of typhoid fever, continues to be a challenge in many low- and middle-income countries. The major transmission route of S. typhi is fecal-oral, through contaminated food and water; thus, the ultimate measures for typhoid fever prevention and control include the provision of safe water, improved sanitation, and hygiene. Considering the increasing evidence of the global burden of typhoid, particularly among young children, and the long-term horizon for sustained, effective water and sanitation improvements in low-income settings, a growing consensus is to emphasize preventive vaccination. This review provides an overview of the licensed typhoid vaccines and vaccine candidates under development, and the challenges ahead for introduction.

Salmonella Persistence and Host Immunity Are Dictated by the Anatomical Microenvironment

The intracellular bacterial pathogen Salmonella is able to evade the immune system and persist within the host. In some cases, these persistent infections are asymptomatic for long periods and represent a significant public health hazard because the hosts are potential chronic carriers, yet the mechanisms that control persistence are incompletely understood. Using a mouse model of chronic typhoid fever combined with major histocompatibility complex (MHC) class II tetramers to interrogate endogenous, Salmonella-specific CD4⁺ helper T cells, we show that certain host microenvironments may favorably contribute to a pathogen's ability to persist in vivo We demonstrate that the environment in the hepatobiliary system may contribute to the persistence of Salmonella enterica subsp. enterica serovar Typhimurium through liver-resident immunoregulatory CD4⁺ helper T cells, alternatively activated macrophages, and impaired bactericidal activity. This contrasts with lymphoid organs, such as the spleen and mesenteric lymph nodes, where these same cells appear to have a greater capacity for bacterial killing, which may contribute to control of bacteria in these organs. We also found that, following an extended period of infection of more than 2 years, the liver appeared to be the only site that harbored Salmonella bacteria. This work establishes a potential role for nonlymphoid organ immunity in regulating chronic bacterial infections and provides further evidence for the hepatobiliary system as the site of chronic Salmonella infection.

Prevalence, serotypes, and antimicrobial resistance of Salmonella isolates from patients with diarrhea in Shenzhen, China

BACKGROUND

Salmonella is one of the main causative agents of diarrhea which results in substantial disease burden. To determine the prevalence, serotype distribution, and antimicrobial resistance profiles of clinical Salmonella isolates in Shenzhen, a 6-year surveillance study was conducted.

RESULTS

A total of 297 (5.7%) Salmonella strains were isolated from stool samples from 5239 patients. Among the 42 serotypes identified, serotype Typhimurium was the most common one which represented 39.7% of the isolates (118), followed by serotype Enteritidis (71, 23.9%), London (12, 4.0%), 4, 5, 12: i: - (11, 3.7%), and Senftenberg (8, 2.7%). A high frequency of resistance was found in ampicillin (70.6%), piperacillin (64.5%), tetracycline (63.5%), and streptomycin (54.3%). Resistance to ampicillin and tetracycline was observed in 95.3% of S. Typhimurium isolates; and nalidixic acid in 93.1% of S. Enteritidis isolates. Resistance to 5 or more antimicrobial agents was found in 78.8% of S. Typhimurium and 69.0% of S. Enteritidis isolates. A decreased susceptibility to ciprofloxacin and levofloxacin was associated with amino acid alteration in gyrA gene. Point mutations without amino acid changes were seen in gyrB, parC, and parE genes.

CONCLUSIONS

A broad range of serotypes are responsible for Salmonellosis in Shenzhen, with Enteritidis and Typhimurium being the most common serotypes. The high level of antibiotic resistance is of public health significance and ongoing monitoring combined with rational use of antibiotics are recommended. Point mutations in gyrA gene might play an important role in the resistance to fluoroquinolones.

Metabolic Activation of CsgD in the Regulation of Salmonella Biofilms

Among human food-borne pathogens, gastroenteritis-causing Salmonella strains have the most real-world impact. Like all pathogens, their success relies on efficient transmission. Biofilm formation, a specialized physiology characterized by multicellular aggregation and persistence, is proposed to play an important role in the Salmonella transmission cycle. In this manuscript, we used luciferase reporters to examine the expression of csgD, which encodes the master biofilm regulator. We observed that the CsgD-regulated biofilm system responds differently to regulatory inputs once it is activated. Notably, the CsgD system became unresponsive to repression by Cpx and H-NS in high osmolarity conditions and less responsive to the addition of amino acids. Temperature-mediated regulation of csgD on agar was altered by intracellular levels of RpoS and cyclic-di-GMP. In contrast, the addition of glucose repressed CsgD biofilms seemingly independent of other signals. Understanding the fine-tuned regulation of csgD can help us to piece together how regulation occurs in natural environments, knowing that all Salmonella strains face strong selection pressures both within and outside their hosts. Ultimately, we can use this information to better control Salmonella and develop strategies to break the transmission cycle.

The Impact of Vaccination and Prior Exposure on Stool Shedding of Salmonella Typhi and Salmonella Paratyphi in 6 Controlled Human Infection Studies

BACKGROUND

Shedding of Salmonella Typhi or Paratyphi in the stool or urine leads to contamination of food or water, which is a prerequisite for transmission of enteric fever. Currently, there are limited data on the effect of vaccination or prior exposure on stool shedding.

METHODS

Six Salmonella Typhi or Paratyphi human challenge studies were conducted between 2011 and 2017. Participants were either unvaccinated or vaccinated with 1 of 4 vaccines: Vi-polysaccharide (Vi-PS), Vi-tetanus-toxoid conjugate vaccine (Vi-TT), live oral Ty21a vaccine, or an experimental vaccine (M01ZH09). Daily stool cultures were collected for 14 days after challenge.

RESULTS

There were 4934 stool samples collected from 430 volunteers. Participants who received Vi-PS or Vi-TT shed less than unvaccinated participants (odds ratio [OR], 0.34; 95% confidence interval [CI], 0.15-0.77; P = .010 and OR, 0.41; 95% CI, 0.19-0.91, P = .029 for Vi-PS and Vi-TT, respectively). Higher anti-Vi immunoglobulin G titers were associated with less shedding of S. Typhi (P < .0001). A nonsignificant reduction in shedding was associated with Ty21a vaccine (OR, 0.57; 95% CI, 0.27-1.20; P = .140). Individuals previously exposed to S. Typhi shed less than previously unexposed individuals (OR, 0.30; 95% CI, 0.1-0.8; P = .016). Shedding of S. Typhi was more common than S. Paratyphi.

CONCLUSIONS

Prior vaccination with Vi vaccines, or natural infection, reduces onward transmission of S. Typhi. Field trials of Vi-TT should be designed to detect indirect protection, reflecting the consequence of reduced stool shedding observed in the human challenge model.

Use of Typhoid Vi-Polysaccharide Vaccine as a Vaccine Probe to Delineate Clinical Criteria for Typhoid Fever

Blood cultures (BCs) detect an estimated 50% of typhoid fever cases. There is need for validated clinical criteria to define cases that are BC negative, both to help direct empiric antibiotic treatment and to better evaluate the magnitude of protection conferred by typhoid vaccines. To derive and validate a clinical rule for defining BC-negative typhoid fever, we assessed, in a cluster-randomized effectiveness trial of Vi-polysaccharide (ViPS) typhoid vaccine in Kolkata, India, 14,797 episodes of fever lasting at least 3 days during 4 years of comprehensive, BC-based surveillance of 70,865 persons. A recursive partitioning algorithm was used to develop a decision rule to predict BC-proven typhoid cases with a diagnostic specificity of 97–98%. To validate this rule as a definition for BC-negative typhoid fever, we assessed whether the rule defined culture-negative syndromes prevented by ViPS vaccine. In a training subset of individuals, we identified the following two rules: rule 1: patients aged < 15 years with prolonged fever accompanied by a measured body temperature ≥ 100°F, headache, and nausea; rule 2: patients aged ≥ 15 years with prolonged fever accompanied by nausea and palpable liver but without constipation. The adjusted protective efficacy of ViPS against clinical typhoid defined by these rules in persons aged ≥ 2 years in a separate validation subset was 33% (95% CI: 4–53%). We have defined and validated a clinical rule for predicting BC-negative typhoid fever using a novel vaccine probe approach. If validated in other settings, this rule may be useful to guide clinical care and to enhance typhoid vaccine evaluations.

Typhoid Vaccine Acceleration Consortium Malawi: A Phase III, Randomized, Double-blind, Controlled Trial of the Clinical Efficacy of Typhoid Conjugate Vaccine Among Children in Blantyre, Malawi

BACKGROUND

Typhoid fever is an acute infection characterized by prolonged fever following the ingestion and subsequent invasion of Salmonella enterica serovar Typhi (S. Typhi), a human-restricted pathogen. The incidence of typhoid fever has been most reported in children 5-15 years of age, but is increasingly recognized in children younger than 5 years old. There has been a recent expansion of multidrug-resistant typhoid fever globally. Prior typhoid vaccines were not suitable for use in the youngest children in countries with a high burden of disease. This study aims to determine the efficacy of a typhoid conjugate vaccine (TCV) that was recently prequalified by the World Health Organization, by testing it in children 9 months through 12 years of age in Blantyre, Malawi.

METHODS

In this Phase III, individually randomized, controlled, double-blind trial of the clinical efficacy of TCV, 28 000 children 9 months through 12 years of age will be enrolled and randomized in a 1:1 ratio to receive either Vi-TCV or a meningococcal serogroup A conjugate vaccine. A subset of 600 of these children will be further enrolled in an immunogenicity and reactogenicity sub-study to evaluate the safety profile and immune response elicited by Vi-TCV. Recruiting began in February 2018.

RESULTS

All children will be under passive surveillance for at least 2 years to determine the primary outcome, which is blood culture-confirmed S. Typhi illness. Children enrolled in the immunogenicity and reactogenicity sub-study will have blood drawn before vaccination and at 2 timepoints after vaccination to measure their immune response to vaccination. They will also be followed actively for adverse events and serious adverse events.

CONCLUSIONS

The introduction of a single-dose, efficacious typhoid vaccine into countries with high burden of disease or significant antimicrobial resistance could have a dramatic impact, protecting children from infection and reducing antimicrobial usage and associated health inequity in the world's poorest places. This trial, the first of a TCV in Africa, seeks to demonstrate the impact and programmatic use of TCVs within an endemic setting.

CLINICAL TRIALS REGISTRATION

NCT03299426.

Salmonella Typhi From Blood Cultures in the Democratic Republic of the Congo: A 10-Year Surveillance

Background

This study gives an overview of a decade (2007–2017) of hospital-based Salmonella Typhi bloodstream infection (BSI) surveillance in the Democratic Republic of the Congo (DRC), at 4 main sampling sites.

Methods

Blood cultures were sampled in hospital-admitted patients with suspected BSI, according to standardized clinical indications. The results of the surveillance period 2015–2017 were compiled with those of previous surveillance periods (2007–2010 and 2011–2014). Whole genome sequencing of isolates with decreased ciprofloxacin susceptibility (DCS) was performed.

Results

Salmonella Typhi was isolated in 1.4% (531/37 388) and 10.3% (531/5177) of suspected and culture-confirmed BSI episodes, respectively. Salmonella Typhi ranked first among the BSI pathogens in adults (n = 220), but was mostly (n = 301 [56.7%]) isolated from children, of which 72.1% (217/301) and 31.6% (95/301) were <10 years and <5 years old, respectively. Multidrug resistance (MDR), DCS, and combined MDR/DCS were found in 38.3% (n = 180), 24.5% (n = 115), and 11.9% (n = 56) of 470 first isolates, respectively. MDR and DCS rates had increased since 2007, but remained stable during 2015–2017 with no geographical clustering at the province level. Most (91/93 [97.8%]) DCS isolates sequenced belonged to Genotyphi genotype 2.5.1, and gyr S83 was the most frequent DCS mutation (76/93 [81.7%]). Infections occurred perennially, but increased during the rainy season.

Conclusions

Salmonella Typhi was a frequent cause of BSI in adults and children in DRC, with high rates of antibiotic resistance. Sustainable surveillance and implementation of vaccination are compelling.