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

Trends in antimicrobial susceptibility pattern of Salmonella species isolated from bacteremia patients at a tertiary care center in Northern India

The study was done to assess the antimicrobial susceptibility pattern among Salmonella enterica serovars causing bacteremia in Northern India. In this observational study, blood samples positive for Salmonella enterica serovars from January 2021 to April 2023 were studied. Species identification was done using MALDI-ToF MS. Serotyping was done using slide agglutination method. Antimicrobial susceptibility was interpreted as per the CLSI guidelines. During the study period, 32 Salmonella enterica serovars were isolated. Salmonella enterica serovar Typhi was the predominant serovar, followed by Salmonella enterica serovar Paratyphi A. All isolates were susceptible to ceftriaxone, chloramphenicol, co-trimoxazole and cefotaxime. Pefloxacin showed 100% resistance. Resistance to nalidixic acid was found in 81.2% isolates. Of the isolates resistant to nalidixic acid, 19(73.08%) isolates were resistant to ciprofloxacin also. This changing susceptibility pattern necessitates continuous surveillance of antibiogram of Salmonella isolates to rationalize the treatment protocols for invasive salmonellosis and prevent emergence of resistant strains.

Clinical characteristics of enteric fever and performance of TUBEX TF IgM test in Indonesian hospitals

BACKGROUND

Accurate diagnosis of enteric fever is challenging, particularly in low- and middle-income countries, due to the overlap of clinical and laboratory features with other pathogens. To better understand the difficulties in enteric fever diagnosis, we evaluated the characteristics of patients clinically diagnosed with enteric fever and the real-world performance of TUBEX TF, one of the most used tests in Indonesia.

METHODOLOGY/PRINCIPAL FINDINGS

Patients were recruited through the AFIRE (Etiology of Acute Febrile Illness Requiring Hospitalization) study at eight Indonesian hospitals. Blood culture was performed for all patients, and TUBEX TF was performed for suspected enteric cases. Salmonella PCR and ELISA tests were performed at a reference lab. Sensitivity and specificity of TUBEX TF and IgM and IgG anti-S. Typhi ELISA were determined. Of 301 patients clinically diagnosed with enteric fever, 50 (16.6%) were confirmed by blood culture and/or PCR. Confirmed cases were mostly school-aged children presenting with fever, anorexia, dizziness and/or abdominal pain with normal leukocyte count or leukopenia. TUBEX TF demonstrated a sensitivity of 97.6% to 70.7% and specificity of 38.3% to 67.2% at cutoffs of 4 and 6, respectively. Acute IgG demonstrated the best sensitivity and specificity, at 90.7% and 82.7%, respectively, and the best ROC characteristics.

CONCLUSIONS/SIGNIFICANCE

A substantial proportion of enteric fever was misdiagnosed at all study hospitals, likely due to the overlap of clinical characteristics and lab parameters with those of other common pathogens. The TUBEX TF rapid serological assay demonstrated suboptimal performance in our setting and tended to over-diagnose enteric fever. The role of IgG from acute specimens for identification of enteric fever cases merits additional consideration.

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.

Concurrent infection of dengue virus with malaria parasites among outpatients attending healthcare facilities in Benin city, Nigeria

Background

Dengue virus (DENV) and malaria parasites (MP) are among the common febrile diseases affecting the tropics and subtropics of the world. Both are mosquito-borne pathogens affecting humans and other animals.

Methods

Blood samples were collected from 280 consented out-patients attending the selected hospitals and were analyzed. Malaria parasites were detected using microscopy and Malaria Ag Pf/Pan Rapid Test Device. Dengue virus was detected by serology and heminested reverse transcriptase PCR (hnRT-PCR) to target the flavivirus polymerase (NS5) gene.

Results

Malaria parasites recorded a total positivity of 151 patients (53.9%) using microscopy, while DENV antibodies (DENV IgM and DENV IgG) were positive in 16 (5.7%) and 39 (13.9%) patients, respectively. There was a concurrent infection between MP/DENV IgM in 13 (4.6%) patients and MP/DENV IgG in 27 (9.6%) patients. Molecular identification revealed DENV serotype 2 in circulation.

Conclusion

This study documents molecular evidence of dengue virus coexisting with malaria parasites in the study population, hence the need for efficient surveillance and control system.

Defying the odds: Determinants of the antimicrobial response of Salmonella Typhi and their interplay

Salmonella Typhi, the invasive serovar of S. enterica subspecies enterica, causes typhoid fever in healthy human hosts. The emergence of antibiotic-resistant strains has consistently challenged the successful treatment of typhoid fever with conventional antibiotics. Antimicrobial resistance (AMR) in Salmonella is acquired either by mutations in the genomic DNA or by acquiring extrachromosomal DNA via horizontal gene transfer. In addition, Salmonella can form a subpopulation of antibiotic persistent (AP) cells that can survive at high concentrations of antibiotics. These have reduced the effectiveness of the first and second lines of antibiotics used to treat Salmonella infection. The recurrent and chronic carriage of S. Typhi in human hosts further complicates the treatment process, as a remarkable shift in the immune response from pro-inflammatory Th1 to anti-inflammatory Th2 is observed. Recent studies have also highlighted the overlap between AP, persistent infection (PI) and AMR. These incidents have revealed several areas of research. In this review, we have put forward a timeline for the evolution of antibiotic resistance in Salmonella and discussed the different mechanisms of the same availed by the pathogen at the genotypic and phenotypic levels. Further, we have presented a detailed discussion on Salmonella antibiotic persistence (AP), PI, the host and bacterial virulence factors that can influence PI, and how both AP and PI can lead to AMR.

Mapping the incidence rate of typhoid fever in sub-Saharan Africa

BACKGROUND

With more than 1.2 million illnesses and 29,000 deaths in sub-Saharan Africa in 2017, typhoid fever continues to be a major public health problem. Effective control of the disease would benefit from an understanding of the subnational geospatial distribution of the disease incidence.

METHOD

We collated records of the incidence rate of typhoid fever confirmed by culture of blood in Africa from 2000 to 2022. We estimated the typhoid incidence rate for sub-Saharan Africa on 20 km × 20 km grids by exploring the association with geospatial covariates representing access to improved water and sanitation, health conditions of the population, and environmental conditions.

RESULTS

We identified six published articles and one pre-print representing incidence rate estimates in 22 sites in 2000-2022. Estimated incidence rates showed geospatial variation at sub-national, national, and regional levels. The incidence rate was high in Western and Eastern African subregions followed by Southern and Middle African subregions. By age, the incidence rate was highest among 5-14 yo followed by 2-4 yo, > 14 yo, and 0-1 yo. When aggregated across all age classes and grids that comprise each country, predicted incidence rates ranged from 43.7 (95% confidence interval: 0.6 to 591.2) in Zimbabwe to 2,957.8 (95% CI: 20.8 to 4,245.2) in South Sudan per 100,000 person-years. Sub-national heterogeneity was evident with the coefficient of variation at the 20 km × 20 km grid-level ranging from 0.7 to 3.3 and was generally lower in high-incidence countries and widely varying in low-incidence countries.

CONCLUSION

Our study provides estimates of 20 km × 20 km incidence rate of typhoid fever across sub-Saharan Africa based on data collected from 2000 through 2020. Increased understanding of the subnational geospatial variation of typhoid fever in Africa may inform more effective intervention programs by better targeting resources to heterogeneously disturbed disease risk.

Comparative Transcriptomic Analysis of Flagellar-Associated Genes in Salmonella Typhimurium and Its rnc Mutant

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a globally recognized foodborne pathogen that affects both animals and humans. Endoribonucleases mediate RNA processing and degradation in the adaptation of bacteria to environmental changes and have been linked to the pathogenicity of S. Typhimurium. Not much is known about the specific regulatory mechanisms of these enzymes in S. Typhimurium, particularly in the context of environmental adaptation. Thus, this study carried out a comparative transcriptomic analysis of wild-type S. Typhimurium SL1344 and its mutant (∆rnc), which lacks the rnc gene encoding RNase III, thereby elucidating the detailed regulatory characteristics that can be attributed to the rnc gene. Global gene expression analysis revealed that the ∆rnc strain exhibited 410 upregulated and 301 downregulated genes (fold-change > 1.5 and p < 0.05), as compared to the wild-type strain. Subsequent bioinformatics analysis indicated that these differentially expressed genes are involved in various physiological functions, in both the wild-type and ∆rnc strains. This study provides evidence for the critical role of RNase III as a general positive regulator of flagellar-associated genes and its involvement in the pathogenicity of S. Typhimurium.

Typhoid fever

Typhoid fever is an invasive bacterial disease associated with bloodstream infection that causes a high burden of disease in Africa and Asia. Typhoid primarily affects individuals ranging from infants through to young adults. The causative organism, Salmonella enterica subsp. enterica serovar Typhi is transmitted via the faecal-oral route, crossing the intestinal epithelium and disseminating to systemic and intracellular sites, causing an undifferentiated febrile illness. Blood culture remains the practical reference standard for diagnosis of typhoid fever, where culture testing is available, but novel diagnostic modalities are an important priority under investigation. Since 2017, remarkable progress has been made in defining the global burden of both typhoid fever and antimicrobial resistance; in understanding disease pathogenesis and immunological protection through the use of controlled human infection; and in advancing effective vaccination programmes through strategic multipartner collaboration and targeted clinical trials in multiple high-incidence priority settings. This Primer thus offers a timely update of progress and perspective on future priorities for the global scientific community.

Pangenome diversification and resistance gene characterization in Salmonella Typhi prioritized RfaJ as a significant therapeutic marker

BACKGROUND

Salmonella Typhi stands as the etiological agent responsible for the onset of human typhoid fever. The pressing demand for innovative therapeutic targets against S. Typhi is underscored by the escalating prevalence of this pathogen and the severe nature of its infections. Consequently, this study employs pangenome analysis to scrutinize 119 S. Typhi-resistant strains, aiming to identify the most promising therapeutic targets originating from its core genome.

RESULTS

Subtractive genomics was employed to systematically eliminate non-homologous (n=1147), essential (n=551), drug-like (n=80), and pathogenicity-related (n=18) proteins from the initial pool of 3351 core genome proteins. Consequently, lipopolysaccharide 1,2-glucosyltransferase RfaJ was designated as the optimal pharmacological target due to its potential versatility. Furthermore, a compendium of 9000 FDA-approved compounds was repurposed for evaluation against the RfaJ drug target, with the specific intent of prioritizing novel, high-potency therapeutic candidates for combating S. Typhi. Ultimately, four compounds, namely DB00549 (Zafirlukast), DB15637 (Fluzoparib), DB15688 (Zavegepant), and DB12411 (Bemcentinib), were singled out as potential inhibitors based on the ligand-protein binding affinity (indicated by the lowest anticipated binding energy) and the overall stability of these compounds. Notably, molecular dynamics simulations, conducted over a 50 nanosecond interval, convincingly demonstrated the stability of these compounds in the context of the RfaJ protein.

CONCLUSION

In summary, the present findings hold significant promise as an initial stride in the broader drug discovery endeavor against S. Typhi infections. However, the experimental validation of the identified drug target and drug candidate is further required to increase the effectiveness of the applied methodology.

Trends in antimicrobial resistance amongst Salmonella Paratyphi A isolates in Bangladesh: 1999-2021

BACKGROUND

Typhoid and paratyphoid remain common bloodstream infections in areas with suboptimal water and sanitation infrastructure. Paratyphoid, caused by Salmonella Paratyphi A, is less prevalent than typhoid and its antimicrobial resistance (AMR) trends are less documented. Empirical treatment for paratyphoid is commonly based on the knowledge of susceptibility of Salmonella Typhi, which causes typhoid. Hence, with rising drug resistance in Salmonella Typhi, last-line antibiotics like ceftriaxone and azithromycin are prescribed for both typhoid and paratyphoid. However, unlike for typhoid, there is no vaccine to prevent paratyphoid. Here, we report 23-year AMR trends of Salmonella Paratyphi A in Bangladesh.

METHODS

From 1999 to 2021, we conducted enteric fever surveillance in two major pediatric hospitals and three clinics in Dhaka, Bangladesh. Blood cultures were performed at the discretion of the treating physicians; cases were confirmed by culture, serological and biochemical tests. Antimicrobial susceptibility was determined following CLSI guidelines.

RESULTS

Over 23 years, we identified 2,725 blood culture-confirmed paratyphoid cases. Over 97% of the isolates were susceptible to ampicillin, chloramphenicol, and cotrimoxazole, and no isolate was resistant to all three. No resistance to ceftriaxone was recorded, and >99% of the isolates were sensitive to azithromycin. A slight increase in minimum inhibitory concentration (MIC) is noticed for ceftriaxone but the current average MIC is 32-fold lower than the resistance cut-off. Over 99% of the isolates exhibited decreased susceptibility to ciprofloxacin.

CONCLUSIONS

Salmonella Paratyphi A has remained susceptible to most antibiotics, unlike Salmonella Typhi, despite widespread usage of many antibiotics in Bangladesh. The data can guide evidence-based policy decisions for empirical treatment of paratyphoid fever, especially in the post typhoid vaccine era, and with the availability of new paratyphoid diagnostics.

Typhoid fever due to laboratory-acquired Salmonella Typhi, confirmed by core genome multi-locus sequence typing

We present a case of laboratory-acquired Salmonella Typhi, resulting in hospitalization of a technician. Blood and stool cultures revealed a S. Typhi strain, identical to the strain with which the employee had recently worked, confirmed using core-genome multilocus sequence typing. The incident occurred despite working in a biosafety cabinet.

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.

Whole-genome sequencing of multidrug resistance Salmonella Typhi clinical strains isolated from Balochistan, Pakistan

Introduction

Salmonella enterica serovar Typhi (S. Typhi) is a major cause of morbidity and mortality in developing countries, contributing significantly to the global disease burden.

Methods

In this study, S. Typhi strains were isolated from 100 patients exhibiting symptoms of typhoid fever at a tertiary care hospital in Pakistan. Antimicrobial testing of all isolates was performed to determine the sensitivity and resistance pattern. Three MDR strains, namely QS194, QS430, and QS468, were subjected to whole genome sequencing for genomic characterization.

Results and Discussion

MLST analysis showed that QS194, belonged to ST19, which is commonly associated with Salmonella enterica serovar typhimurium. In contrast, QS430 and QS468, belonged to ST1, a sequence type frequently associated with S. Typhi. PlasmidFinder identified the presence of IncFIB(S) and IncFII(S) plasmids in QS194, while IncQ1 was found in QS468. No plasmid was detected in QS430. CARD-based analysis showed that the strains were largely resistant to a variety of antibiotics and disinfecting agents/antiseptics, including fluoroquinolones, cephalosporins, monobactams, cephamycins, penams, phenicols, tetracyclines, rifamycins, aminoglycosides, etc. The S. Typhi strains possessed various virulence factors, such as Vi antigen, Agf/Csg, Bcf, Fim, Pef, etc. The sequencing data indicated that the strains had antibiotic resistance determinants and shared common virulence factors. Pangenome analysis of the selected S. Typhi strains identified 13,237 genes, with 3,611 being core genes, 2,093 shell genes, and 7,533 cloud genes. Genome-based typing and horizontal gene transfer analysis revealed that the strains had different evolutionary origins and may have adapted to distinct environments or host organisms. These findings provide important insights into the genetic characteristics of S. Typhi strains and their potential association with various ecological niches and host organisms.

Antimicrobial Resistance in Romania: Updates on Gram-Negative ESCAPE Pathogens in the Clinical, Veterinary, and Aquatic Sectors

Multidrug-resistant Gram-negative bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, and members of the Enterobacterales order are a challenging multi-sectorial and global threat, being listed by the WHO in the priority list of pathogens requiring the urgent discovery and development of therapeutic strategies. We present here an overview of the antibiotic resistance profiles and epidemiology of Gram-negative pathogens listed in the ESCAPE group circulating in Romania. The review starts with a discussion of the mechanisms and clinical significance of Gram-negative bacteria, the most frequent genetic determinants of resistance, and then summarizes and discusses the epidemiological studies reported for A. baumannii, P. aeruginosa, and Enterobacterales-resistant strains circulating in Romania, both in hospital and veterinary settings and mirrored in the aquatic environment. The Romanian landscape of Gram-negative pathogens included in the ESCAPE list reveals that all significant, clinically relevant, globally spread antibiotic resistance genes and carrying platforms are well established in different geographical areas of Romania and have already been disseminated beyond clinical settings.

Outbreak of Paratyphoid Fever Caused by Contaminated Street-Vended Food at Qingyang Town, China, 2016

In 2016, an outbreak of paratyphoid fever occurred in 40 cases at Qingyang town, in China. A case-control study was carried out to determine the source of this outbreak. Case-control study was conducted to identify the risk factors of this outbreak. The cases were identified as patients with isolation of S. Paratyphi, controls were confirmed cases' healthy classmates, colleagues or neighbors and matched by age (±5 y) and gender. Pulsed-field gel electrophoresis was performed to source tracking. Totally, 40 cases were reported: 24 cases were students, and 20 (20/24) of them were Qingyang High School students. For the case-control study, consuming Chinese egg pancakes was detected as a risk factor (OR_1:1 = 5.000; 95% CI: 1.710-14.640), and hand-washing before meals was protective behavior compared with seldom hand-washing (OR_1:1 = 23.256; 95% CI: 2.451-200.000). S. Paratyphi was cultured from a well water sample used for washing contents of the pancakes. Isolates from well water and paratyphoid cases showed the same PFGE patterns. Contaminated well water and Chinese egg pancakes were likely source and vehicle of this outbreak. Health education, especially handwashing, and food safety supervision should be promoted particularly in schools.

Host acid signal controls Salmonella flagella biogenesis through CadC-YdiV axis

Upon entering host cells, Salmonella quickly turns off flagella biogenesis to avoid recognition by the host immune system. However, it is not clear which host signal(s) Salmonella senses to initiate flagellum control. Here, we demonstrate that the acid signal can suppress flagella synthesis and motility of Salmonella, and this occurs after the transcription of master flagellar gene flhDC and depends on the anti-FlhDC factor YdiV. YdiV expression is activated after acid treatment. A global screen with ydiV promoter DNA and total protein from acid-treated Salmonella revealed a novel regulator of YdiV, the acid-related transcription factor CadC. Further studies showed that CadC_C, the DNA binding domain of CadC, directly binds to a 33 nt region of the ydiV promoter with a 0.2 μM K_D affinity. Furthermore, CadC could separate H-NS-ydiV promoter DNA complex to form CadC-DNA complex at a low concentration. Structural simulation and mutagenesis assays revealed that H43 and W106 of CadC are essential for ydiV promoter binding. No acid-induced flagellum control phenotype was observed in cadC mutant or ydiV mutant strains, suggesting that flagellum control during acid adaption is dependent on CadC and YdiV. The intracellular survival ability of cadC mutant strain decreased significantly compared with WT strain while the flagellin expression could not be effectively controlled in the cadC mutant strain when surviving within host cells. Together, our results demonstrated that acid stress acts as an important host signal to trigger Salmonella flagellum control through the CadC-YdiV-FlhDC axis, allowing Salmonella to sense a hostile environment and regulate flagellar synthesis during infection.

Molecular diagnostics and next-generation sequencing reveal real etiological characteristics of invasive Salmonella infection in febrile illness in Freetown, Sierra Leone

Invasive Salmonella infection, which can cause typhoid/paratyphoid fever and invasive non-typhoidal salmonellosis, is a public health burden in Africa. Accurate diagnosis and etiological characterization are required to conduct prevalence and risk estimations for Salmonella infection; however, the utilization of optimal techniques and surveillance data are still insufficient. In this study, we performed a laboratory-based survey in Freetown, which is the biggest city in Sierra Leone with a high burden of typhoid fever, by using blood culture and molecular methods but not the Widal test, to estimate the prevalence and aetiology of invasive Salmonella infection among fever patients. We found a very low prevalence of typhoid fever in patients with fever during the investigation period, and this prevalence was clearly overestimated by the Widal test. Genome sequencing of the S. Typhi isolate from this work revealed that the strain carried multiple antibiotic resistance genes, and an epidemic clone that has existed in West Africa for years was also detected in Sierra Leone. By using metagenomic sequencing, one patient with invasive non-typhoidal salmonellosis was identified as having bacterial co-infections. Our data highlight that Salmonella surveillance based on accurate laboratory diagnosis and genome sequencing needs to be strengthened to provide a better estimation of the real epidemics and enable potential risk assessment by etiological analysis in Africa. Even in a laboratory with only basic equipment, it is possible to conduct next-generation sequencing for pathogen discovery in bloodstream infections and to determine the etiological characteristics of pathogene without complex combinations of laboratory methods.

Surface-enhanced Raman spectroscopy for characterization of filtrate portions of blood serum samples of typhoid patients

BACKGROUND

Surface-enhanced Raman spectroscopy (SERS) is explored to design a rapid screening method for the characterization and diagnosis of typhoid fever by employing filtrate fractions of blood serum samples obtained by centrifugal filtration with 50 KDa filters.

OBJECTIVES

The purpose of this study, to separate the filtrate portions of blood serum samples in this way contain proteins smaller than 50 kDa and removal of bigger size protein which allows to acquire the SERS spectral features of smaller proteins more effectively which are probably associated with typhoid disease. Disease caused by Salmonella typhi diagnose more effectively by using surface-enhanced Raman spectroscopy (SERS) and multivariate data analysis tools.

METHODS

SERS was used as a diagnostic tool for typhoid fever by comparison between healthy and diseased samples. For this purpose, all the samples were analyzed by comparing their SERS spectral features. Over the spectral range of 400-1800cm^-1, multivariate data analysis techniques such as Principal Component Analysis (PCA) and Partial Least Squares-Discriminant Analysis (PLS-DA) are applied to diagnose and differentiate different filtrate fractions of blood serum samples of patients of typhoid fever and healthy ones.

RESULTS

By comparing SERS spectra of healthy filtrate with that of filtrate of typhoid sample, the SERS spectral features associated with disease development are identified including PCA is found to be efficient for the qualitative differentiation of all of the samples analyzed. Moreover, PLS-DA successfully identified and classified healthy and typhoid positive blood serum samples with 97 % accuracy, 99 % specificity, 91 % sensitivity and 0.78 area under the receiver operating characteristic (AUROC) curve.

CONCLUSIONS

Surface enhanced Raman spectroscopy using silver nanoparticles SERS substrate, is found to be useful technique for the quick identification and evaluation of filtrate fractions of the blood serum samples of healthy and typhoid samples for disease diagnosis.

The subversion of toll-like receptor signaling by bacterial and viral proteases during the development of infectious diseases

Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) that respond to pathogen-associated molecular patterns (PAMPs). The recognition of specific microbial ligands by TLRs triggers an innate immune response and also promotes adaptive immunity, which is necessary for the efficient elimination of invading pathogens. Successful pathogens have therefore evolved strategies to subvert and/or manipulate TLR signaling. Both the impairment and uncontrolled activation of TLR signaling can harm the host, causing tissue destruction and allowing pathogens to proliferate, thus favoring disease progression. In this context, microbial proteases are key virulence factors that modify components of the TLR signaling pathway. In this review, we discuss the role of bacterial and viral proteases in the manipulation of TLR signaling, highlighting the importance of these enzymes during the development of infectious diseases.

A new potential risk: The impacts of Klebsiella pneumoniae infection on the histopathology, transcriptome and metagenome of Chinese mitten crab (Eriocheir sinensis)

Klebsiella pneumoniae is a common conditional pathogen found in natural soil water sources and vegetation and can infect invertebrates, vertebrates, and plants. In this study, we isolated K. pneumoniae from the hepatopancreas of the Chinese mitten crab (Eriocheir sinensis) for the first time and then we analysed its effects of on the histopathological changes, the transcriptome of the hepatopancreas, and the gut microbiota of this crab species. The findings of this study showed that K. pneumoniae infection has led to significant structural changes in the hepatopancreas, such as the production of vacuolated tissue structures, disorganized cell arrangement, and lysis of some hepatopancreatic cells. Also, the infection caused activation of the antioxidant-related enzymes such as SOD and CAT by inducing oxidative stress. The transcriptome of the hepatopancreas identified 10,940 differentially expressed genes (DEGs) in the susceptible (SG) groups and control (CG) groups, and 8495 DEGs in the SG groups and anti-infective (AI) groups. The KEGG pathway revealed upregulated DEGs caused by K. pneumoniae infection that involved in the immune response and apoptotic functional pathways, and also downregulated DEGs involved in the digestive absorption, metabolic, and biosynthetic signaling pathways. Meanwhile, metagenics sequencing revealed that at the phylum, class, order, family, and genus levels, K. pneumoniae infection altered the composition of the gut microbiota of E. sinensis, through increasing the abundance of Prolixibacteraceae, Enterobacterales, and Roseimarinus and decreasing the abundance of Alphaproteobacteria. The flora structure has also been changed between the SG and AI groups, with the abundance of Firmicutes, Erysipelotrichales, and Erysipelotrichaceae that were significantly decreased in the SG groups than in the AI groups. But, the abundance of Acinetobacter was considerably higher than in the AI group. In summary, K. pneumoniae infection induced oxidative stress in E. sinensis, triggered changes in immune-related gene expression, and caused structural changes in the gut microbiota. This study provides data to support the analysis of bacterial infection probes in several crustacean species.

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.

Treatment of enteric fever (typhoid and paratyphoid fever) with cephalosporins

BACKGROUND

Typhoid and paratyphoid (enteric fever) are febrile bacterial illnesses common in many low- and middle-income countries. The World Health Organization (WHO) currently recommends treatment with azithromycin, ciprofloxacin, or ceftriaxone due to widespread resistance to older, first-line antimicrobials. Resistance patterns vary in different locations and are changing over time. Fluoroquinolone resistance in South Asia often precludes the use of ciprofloxacin. Extensively drug-resistant strains of enteric fever have emerged in Pakistan. In some areas of the world, susceptibility to old first-line antimicrobials, such as chloramphenicol, has re-appeared. A Cochrane Review of the use of fluoroquinolones and azithromycin in the treatment of enteric fever has previously been undertaken, but the use of cephalosporins has not been systematically investigated and the optimal choice of drug and duration of treatment are uncertain.

OBJECTIVES

To evaluate the effectiveness of cephalosporins for treating enteric fever in children and adults compared to other antimicrobials.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, Embase, LILACS, the WHO ICTRP and ClinicalTrials.gov up to 24 November 2021. We also searched reference lists of included trials, contacted researchers working in the field, and contacted relevant organizations.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in adults and children with enteric fever that compared a cephalosporin to another antimicrobial, a different cephalosporin, or a different treatment duration of the intervention cephalosporin. Enteric fever was diagnosed on the basis of blood culture, bone marrow culture, or molecular tests.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were clinical failure, microbiological failure and relapse. Our secondary outcomes were time to defervescence, duration of hospital admission, convalescent faecal carriage, and adverse effects. We used the GRADE approach to assess certainty of evidence for each outcome.

MAIN RESULTS

We included 27 RCTs with 2231 total participants published between 1986 and 2016 across Africa, Asia, Europe, the Middle East and the Caribbean, with comparisons between cephalosporins and other antimicrobials used for the treatment of enteric fever in children and adults. The main comparisons are between antimicrobials in most common clinical use, namely cephalosporins compared to a fluoroquinolone and cephalosporins compared to azithromycin. Cephalosporin (cefixime) versus fluoroquinolones Clinical failure, microbiological failure and relapse may be increased in patients treated with cefixime compared to fluoroquinolones in three small trials published over 14 years ago: clinical failure (risk ratio (RR) 13.39, 95% confidence interval (CI) 3.24 to 55.39; 2 trials, 240 participants; low-certainty evidence); microbiological failure (RR 4.07, 95% CI 0.46 to 36.41; 2 trials, 240 participants; low-certainty evidence); relapse (RR 4.45, 95% CI 1.11 to 17.84; 2 trials, 220 participants; low-certainty evidence). Time to defervescence in participants treated with cefixime may be longer compared to participants treated with fluoroquinolones (mean difference (MD) 1.74 days, 95% CI 0.50 to 2.98, 3 trials, 425 participants; low-certainty evidence). Cephalosporin (ceftriaxone) versus azithromycin Ceftriaxone may result in a decrease in clinical failure compared to azithromycin, and it is unclear whether ceftriaxone has an effect on microbiological failure compared to azithromycin in two small trials published over 18 years ago and in one more recent trial, all conducted in participants under 18 years of age: clinical failure (RR 0.42, 95% CI 0.11 to 1.57; 3 trials, 196 participants; low-certainty evidence); microbiological failure (RR 1.95, 95% CI 0.36 to 10.64, 3 trials, 196 participants; very low-certainty evidence). It is unclear whether ceftriaxone increases or decreases relapse compared to azithromycin (RR 10.05, 95% CI 1.93 to 52.38; 3 trials, 185 participants; very low-certainty evidence). Time to defervescence in participants treated with ceftriaxone may be shorter compared to participants treated with azithromycin (mean difference of -0.52 days, 95% CI -0.91 to -0.12; 3 trials, 196 participants; low-certainty evidence). Cephalosporin (ceftriaxone) versus fluoroquinolones It is unclear whether ceftriaxone has an effect on clinical failure, microbiological failure, relapse, and time to defervescence compared to fluoroquinolones in three trials published over 28 years ago and two more recent trials: clinical failure (RR 3.77, 95% CI 0.72 to 19.81; 4 trials, 359 participants; very low-certainty evidence); microbiological failure (RR 1.65, 95% CI 0.40 to 6.83; 3 trials, 316 participants; very low-certainty evidence); relapse (RR 0.95, 95% CI 0.31 to 2.92; 3 trials, 297 participants; very low-certainty evidence) and time to defervescence (MD 2.73 days, 95% CI -0.37 to 5.84; 3 trials, 285 participants; very low-certainty evidence). It is unclear whether ceftriaxone decreases convalescent faecal carriage compared to the fluoroquinolone gatifloxacin (RR 0.18, 95% CI 0.01 to 3.72; 1 trial, 73 participants; very low-certainty evidence) and length of hospital stay may be longer in participants treated with ceftriaxone compared to participants treated with the fluoroquinolone ofloxacin (mean of 12 days (range 7 to 23 days) in the ceftriaxone group compared to a mean of 9 days (range 6 to 13 days) in the ofloxacin group; 1 trial, 47 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

Based on very low- to low-certainty evidence, ceftriaxone is an effective treatment for adults and children with enteric fever, with few adverse effects. Trials suggest that there may be no difference in the performance of ceftriaxone compared with azithromycin, fluoroquinolones, or chloramphenicol. Cefixime can also be used for treatment of enteric fever but may not perform as well as fluoroquinolones.  We are unable to draw firm general conclusions on comparative contemporary effectiveness given that most trials were small and conducted over 20 years previously. Clinicians need to take into account current, local resistance patterns in addition to route of administration when choosing an antimicrobial.

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.

Immune non-interference and safety study of Vi-DT typhoid conjugate vaccine with a measles, mumps and rubella containing vaccine in 9-15 months old Nepalese infants

BACKGROUND

Typhoid fever is a common disease in developing countries especially in the Indian subcontinent and Africa. The available typhoid conjugate vaccines (TCV) have been found to be highly immunogenic in infants and children less than 2 years of age. Many countries are planning to adopt TCV in their routine EPI programs around 9 months of age when measles containing vaccines are given. Therefore, Vi-DT TCV was tested in 9-15 months aged healthy infants in Nepal to demonstrate non-interference with a measles containing vaccine.

METHODS

This was a randomized, open label, phase III study to assess the immune non-interference, safety, and reactogenicity of Vi-DT typhoid conjugate vaccine when given concomitantly with measles, mumps and rubella (MMR) vaccine. A total of 360 participants aged 9-15 months were enrolled and randomized equally into Vi-DT + MMR (180 participants) or MMR alone (180 participants) group and were evaluated for immunogenicity and safety 28 days post vaccination.

RESULTS

Using the immunogenicity set, difference between proportions (95% CI) of the Vi-DT + MMR group vs MMR alone group were -2.73% (-8.85, 3.38), -3.19% (-11.25, 4.88) and 2.91% (-3.36, 9.18) for sero-positivity rate of anti-measles, anti-mumps and anti- rubella, respectively. Only the lower bound of the range in difference of the proportions for sero-positivity rate of anti-mumps did not satisfy the non-inferiority criteria as it was above the -10% limit, which may not be of clinical significance. These results were confirmed in the per protocol set. There were no safety concerns reported from the study and both Vi-DT + MMR and MMR alone groups were comparable in terms of solicited and unsolicited adverse events .

CONCLUSIONS

Results indicated that there is non-interference of MMR vaccine with Vi-DT and Vi-DT conjugate vaccine could be considered as an addition to the EPI schedule among children at risk of contracting typhoid.

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.

Typhoid Fever among Patients Diagnosed with Dengue in a Tertiary Care Centre: A Descriptive Cross-sectional Study

Introduction

Dengue and typhoid fever are different entities with overlapping signs and symptoms which are indistinguishable and there have been few reports of co-infections from endemic areas. The resemblance of symptoms makes accurate clinical diagnosis and treatment difficult. Both are major health problems mainly during monsoon and co-infection, if not timely diagnosed and treated can be fatal. The aim of this study was to find out the prevalence of typhoid fever among patients diagnosed with dengue at a tertiary care centre.

Methods

A descriptive cross-sectional study was done among patients of age >15 years with dengue fever attending the medicine outpatient department in a tertiary care centre from 1 July 2021 to 30 June 2022. Ethical approval was taken from the Institutional Review Committee (Reference number: 466/2020). Convenience sampling was used. Patients with other risk factors for febrile illness were excluded from the study. Point estimate and 90% Confidence Interval were calculated.

Results

Among 95 dengue cases, typhoid fever was observed in 18 (18.95%) (12.36-25.54, 90% Confidence Interval). The mean age of presentation was 35±9 years with a male to female ratio of 0.8:1. Fever was the most common presentation with a mean temperature of 100.8±2.1°F.

Conclusions

The prevalence of typhoid fever among dengue-positive cases was higher as compared to other studies done in similar settings.

Keywords

dengue; fever; typhoid fever.

A Phase 3, Multicenter, Randomized, Controlled Trial to Evaluate Immune Equivalence and Safety of Multidose and Single-dose Formulations of Vi-DT Typhoid Conjugate Vaccine in Healthy Filipino Individuals 6 Months to 45 Years of Age

Trial Design

Phase 3, randomized, controlled, multicenter, equivalence trial.

Methods

Recruitment of participants occurred between 04Februray2020 and 15July2020 at four centers in the Philippines: University of the East - Ramon Magsaysay Memorial Medical Center Inc., Quezon City; University of Philippines Manila - National Institute of Health, Ermita Manila; Asian Hospital and Medical Center, Metro Manila, Philippines Study; and Medical Research Unit, Tropical Disease Foundation, Makati City, Metro Manila, Philippines.

Participants

1800 adults and children 6-months to 45-years of age.

Interventions

Participants received a single injection of multidose (MD) or single dose (SD) Vi-DT as test vaccines or meningococcal conjugate vaccine as a comparator.

Objective

To evaluate immune equivalence of SD and MD formulations of Vi-DT, and to assess the safety of both formulations compared with comparator vaccine.

Outcome Measurement

Blood draw for immunogenicity was performed at baseline prior to vaccine receipt and at four weeks after vaccination for a subset of participants to determine anti-Vi IgG geometric mean titers (GMT) and seroconversion rates. The primary outcome was comparison of anti Vi-IgG seroconversion and GMT between the two formulations of Vi-DT at 4 weeks following vaccine administration. Immune equivalence of MD and SD formulations was confirmed when the two-tailed 95% confidence interval (CI) of the GMT ratio is within [0.67, 1.5] at a two-sided significance level of 0.05. All participants were followed for safety events for six months after vaccine administration.

Randomization

Participants were randomized to receive SD Vi-DT, MD Vi-DT, or meningococcal conjugate vaccines in 2.5:2.5:1 allocation ratio.

Blinding

Study participants and observers were blinded to treatment assignment.

Findings

Immune equivalence of SD (n=252) and MD (n=247) formulations was confirmed by anti-Vi IgG GMT ratio of 1.14 (95%CI: 0.91, 1.43) with respective GMTs in the MD and SD groups of 640.62 IU/mL (95%CI: 546.39, 751.11) and 562.57 IU/mL (95%CI: 478.80, 661.00) (p=0.259). Similarly, anti-Vi IgG seroconversion rate difference between the two formulations of ‒0.43% (95%CI: -4.42, 3.56) confirmed immune equivalence with corresponding seroconversion rates of 98.38% (95%CI: 95.91, 99.37) and 98.81% (95%CI: 96.56, 99.59) in MD and SD Vi-DT formulations, respectively (p=0.722). Both formulations of Vi-DT had a satisfactory safety profile - all five serious adverse events reported during the study were unrelated to the investigational product.

Interpretation

The MD and SD formulations of Vi-DT elicited robust and equivalent immune responses following one dose vaccination, and both formulations demonstrated a favorable safety profile.

Trial Registration

ClinicalTrials.gov: NCT04204096.

Funding

This study was funded by the Bill & Melinda Gates Foundation (OPP 1115556).

Antimicrobial susceptibility and genomic profiling of Salmonella enterica from bloodstream infections at a tertiary referral hospital in Lusaka, Zambia, 2018–2019

•

Salmonella enterica Typhi found to be most prevalent, with genetic diversity

•

Low prevalence of invasive non-typhoidal Salmonella infections

•

Salmonella enterica Typhimurium isolated, belonging to serotype 313

•

High prevalence of multidrug-resistant strains

•

Emergence of fluoroquinolone and cephalosporin resistance

Objectives

This study investigated antimicrobial susceptibility and genomic profiling of S. enterica isolated from bloodstream infections at a tertiary referral hospital in Lusaka, Zambia, 2018–2019.

Method

This was a prospective hospital-based study involving routine blood culture samples submitted to the microbiology laboratory at the University Teaching Hospital. Identification of S. enterica and determination of antimicrobial susceptibility profiles was achieved through conventional and automated methods. Whole-genome sequencing (WGS) was conducted, and the sequence data outputs were processed for species identification, serotype determination, multilocus sequence typing (MLST) profile determination, identification of antimicrobial resistance determinants, and phylogeny.

Results

Seventy-six Salmonella enterica were isolated and 64 isolates underwent WGS. Salmonella Typhi (72%) was the most prevalent serotype. Notable was the occurrence of invasive non-typhoidal Salmonella Typhimurium ST313 (3%), resistance to cephalosporins (4%) and ciprofloxacin (5%), multidrug resistance (46%), and reduced susceptibility to ciprofloxacin (30%) and imipenem (3%). Phylogenetic cluster analysis showed multiple Salmonella serovars with a wide range of genetic diversity.

Conclusion

The genetic diversity of Salmonella Typhi, high prevalence of multidrug resistance, and the emergence of ciprofloxacin and cephalosporin resistance warrants improved hygiene and water and sanitation provision, continued surveillance to apprise antibiograms and inform policy, and the introduction of the typhoid conjugate vaccine.

MODELING THE ROLE OF VACCINATION, ENVIRONMENTAL SANITATION, AND SATURATED TREATMENT ON THE SPREAD OF TYPHOID FEVER

A deterministic nonlinear mathematical model is developed for typhoid transmission dynamics in human hosts, coupled with multiple transmission routes. The model aims to examine the role of control interventions such as vaccination, environmental sanitation, and saturated treatment on the prevalence of typhoid. First, the qualitative analysis of the model with constant control interventions is performed. The model exhibits a backward bifurcation phenomenon. Sensitivity analysis is also conducted to identify impactful parameters for effective control of the disease. Then, the model is extended to a corresponding optimal control problem to investigate the optimum intervention strategies by assessing their effects on typhoid prevalence and economic load. The characterization of the optimal controls is determined using Pontryagin’s Maximum Principle, and the optimality system is developed. Numerical results suggest that, in the absence of treatment, the combination of vaccination and environmental sanitation controls plays an important role in reducing the typhoid burden and economic load. Moreover, the comprehensive use of the three control interventions is more effective than using any single or two combined control interventions. It reduces the number of infective humans and environmental bacteria as well as the cost burden associated with applied controls and opportunity loss. Thus, the comprehensive effect of the three control interventions is found to be more economical during typhoid outbreaks.

Safety and immunogenicity of the Vi-DT typhoid conjugate vaccine in healthy volunteers in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial

Background

Methods

Findings

Interpretation

Funding

Translation

Paediatric enteric fever in Brussels: a case series over 16 years

Enteric fever (EF) is a major public health problem and a witness of the global health disparities. It is caused by Salmonella enterica serovar Typhi (Salmonella ser. Typhi) and Salmonella enterica serovar Paratyphi A, B, C (Salmonella ser. Paratyphi) and is estimated to infect 12-26 million persons yearly. Paediatric data on enteric fever in Europe are scarce. A case series of EF was analysed to describe the clinical presentation, laboratory characteristics and diagnostic challenges identified in a paediatric population in Brussels. We performed a retrospective study of all lab-confirmed cases of enteric fever in children aged 0-15 years at two Brussels teaching hospitals, between January 2005 and December 2020. We reviewed age, gender, travel history, consultations before diagnosis, hospitalisation duration, clinical symptoms and laboratory findings. There were 34 positive isolates of S. typhi and S. paratyphi: 31 patients had positive blood culture, 1 patient had positive bone aspirate and 2 patients had positive stool culture (one was excluded for missing data). There were 20 girls (60%). Median age was 3.5 years (range 5 months to 14 years). Travel to EF endemic areas was present in 55% of patients. Diagnosis was delayed in 80% of children. Eosinopenia was present in 93% of the cohort. The patients had not received any preventive travel education or vaccination.  Conlusion: Enteric fever poses diagnostic challenges to clinicians. Eosinopenia in a febrile patient coming from the tropics should raise suspicion of EF. Travellers to endemic areas should be better educated about EF risks, and typhoid fever vaccination must be promoted. What is Known: • Enteric fever is a global public health problem and includes typhoid and paratyphoid fever. • Typhoid fever is vaccine preventable disease. Paratyphoid fever is not vaccine preventable. What is New: • Enteric fever diagnosis is very challenging in non-endemic settings, and a large proportion of patients may develop serious complications if they receive delayed management. Occurrence of small family clusters is possible and mandates education and monitoring of the families of enteric fever affected children. • We report that the widest majority of our enteric fever affected patients (69%) had aneosinophilia (zero eosinophil count), and almost all patients (93%) had eosinopaenia (less than 50 eosinophil count) during their bacteriaemic phase.

One-step synthesis of carbonaceous adsorbent from soybean bio-residue by microwave heating: Adsorptive, antimicrobial and antifungal behavior

In this work, the transformation of soybean industrial bio-residue with limited practical applications, into a multifunctional carbonaceous adsorbent (SBAC) via one-step microwave-irradiation has been succeeded. The surface porosity, chemical compositions, functionalities and surface chemistry were featured by microscopic pore-textural analysis, elemental constitution analysis, morphological characterization and Fourier transform infra-red spectroscopy. The adsorptive performance of SBAC was evaluated in a batch experiment by adopting different classes of water pollutants, specifically methylene blue (MB), acetaminophen and 2,4-dichlorophenoxyacetic acid (2,4-D). The equilibrium uptakes were analyzed with respect to the non-linearized Langmuir, Freundlich and Temkin isotherm equations. The unique features of SBAC, specifically the antimicrobial and antifungal efficacies were examined against gram-positive/negative bacteria and fungi species. An ordered microporous-mesoporous structure of SBAC, with the BET surface area and total pore volume of 1696 m2/g and 0.94 m3/g, respectively, has been achieved. The equilibrium data of MB and acetaminophen were found to be in good agreement with the Langmuir isotherm model, with the monolayer adsorption capacities (Qo) of 434.57 mg/g and 393.31 mg/g, respectively. The adsorptive experiment of 2,4-D was best fitted to the Freundlich isotherm equation, with the Qo of 253.17 mg/g. The regeneration performance of the spent SBAC under microwave-irradiation could maintain at 69.42-79.31%, even after five (5) adsorption-regeneration cycles. SBAC exhibited excellent inhibition efficiencies against gram-positive/negative bacteria and fungi species, with the inhibition zones at 14.0-28.0 mm. This newly developed SBAC appears to be a new powerful candidate for the remediation of different classes of water contaminants, and novel antibacterial and antifungal agents against biological contaminations. The novel concept of "turn waste into wealth" in a cost-effective and energy saving manner for environmental preservation has been successfully accomplished.

Genomic Investigation Reveals a Community Typhoid Outbreak Caused by Contaminated Drinking Water in China, 2016

Typhoid fever is a life-threatening disease caused by Salmonella enterica serovar Typhi (S. Typhi) and remains a significant public health burden in developing countries. In China, typhoid fever is endemic with a limited number of reported outbreaks. Recently, Chinese local Center for Disease Prevention and Control is starting to apply whole genome sequencing for tracking the source of outbreak isolates. In this study, we conducted a retrospective investigation into a community outbreak of typhoid fever in Lanling, China, in 2016. A total of 26 S. Typhi isolates were recovered from the drinking water (n = 1) and patients' blood (n = 24) and stool (n = 1). Phylogenetic analysis indicated the persistence of the outbreak isolates in drinking water for more than 3 months. The genomic comparison demonstrated a high similarity between the isolate from water and isolates from patients in their genomic content, virulence gene profiles, and antimicrobial resistance gene profile, indicating the S. Typhi isolate from drinking water was responsible for the examined outbreak. The result of pulsed-field gel electrophoresis (PFGE) revealed these isolates had identical PFGE pattern, indicating they are clonal variants. Additionally, phylogeographical analysis of global S. Typhi isolates suggested the outbreak isolates are evolutionarily linked to the isolates from the United Kingdom and Vietnam. Taken together, this study highlights the drinking water and international travel as critical control points of mitigating the outbreak, emphasizing the necessity of regular monitoring of this pathogen in China.

Host acid signal controls Salmonella flagella biogenesis through CadC-YdiV axis

Upon entering host cells, Salmonella quickly turns off flagella biogenesis to avoid recognition by the host immune system. However, it is not clear which host signal(s) Salmonella senses to initiate flagellum control. Here, we demonstrate that the acid signal can suppress flagella synthesis and motility of Salmonella, and this occurs after the transcription of master flagellar gene flhDC and depends on the anti-FlhDC factor YdiV. YdiV expression is activated after acid treatment. A global screen with ydiV promoter DNA and total protein from acid-treated Salmonella revealed a novel regulator of YdiV, the acid-related transcription factor CadC. Further studies showed that CadC_C, the DNA binding domain of CadC, directly binds to a 33 nt region of the ydiV promoter with a 0.2 μM K_D affinity. Furthermore, CadC could separate H-NS-ydiV promoter DNA complex to form CadC-DNA complex at a low concentration. Structural simulation and mutagenesis assays revealed that H43 and W106 of CadC are essential for ydiV promoter binding. No acid-induced flagellum control phenotype was observed in cadC mutant or ydiV mutant strains, suggesting that flagellum control during acid adaption is dependent on CadC and YdiV. The intracellular survival ability of cadC mutant strain decreased significantly compared with WT strain while the flagellin expression could not be effectively controlled in the cadC mutant strain when surviving within host cells. Together, our results demonstrated that acid stress acts as an important host signal to trigger Salmonella flagellum control through the CadC-YdiV-FlhDC axis, allowing Salmonella to sense a hostile environment and regulate flagellar synthesis during infection.

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.

Geographic Pattern of Typhoid Fever in India: A Model-Based Estimate of Cohort and Surveillance Data

Background

Typhoid fever remains a major public health problem in India. Recently, the Surveillance for Enteric Fever in India program completed a multisite surveillance study. However, data on subnational variation in typhoid fever are needed to guide the introduction of the new typhoid conjugate vaccine in India.

Methods

We applied a geospatial statistical model to estimate typhoid fever incidence across India, using data from 4 cohort studies and 6 hybrid surveillance sites from October 2017 to March 2020. We collected geocoded data from the Demographic and Health Survey in India as predictors of typhoid fever incidence. We used a log linear regression model to predict a primary outcome of typhoid incidence.

Results

We estimated a national incidence of typhoid fever in India of 360 cases (95% confidence interval [CI], 297–494) per 100 000 person-years, with an annual estimate of 4.5 million cases (95% CI, 3.7–6.1 million) and 8930 deaths (95% CI, 7360–12 260), assuming a 0.2% case-fatality rate. We found substantial geographic variation of typhoid incidence across the country, with higher incidence in southwestern states and urban centers in the north.

Conclusions

There is a large burden of typhoid fever in India with substantial heterogeneity across the country, with higher burden in urban centers.

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.

A rare case report of enteric fever causing gallbladder perforation

Introduction and importance

Enteric fever is one of the major public health problems mainly in developing countries. Gallbladder perforation is very unusual. Enteric fever rarely causes gallbladder perforation. We report a case of gallbladder perforation due to enteric fever in an adult patient.

Case presentation

A 50-year-old female without any medical illness presented with a history of intermittent fever for two weeks and three days duration of severe abdominal pain. Upper abdominal tenderness and guarding were found in the abdominal examination. Ultrasonography showed thickening of the gallbladder wall and pericholecystic fluid collection. Magnetic resonance cholangiopancreatography revealed a distended gallbladder with sludge, diffuse wall thickening, and contained perforation with a mild amount of free fluid seen in the abdomen. With the diagnosis of type II gallbladder perforation, percutaneous ultrasonography-guided drainage was done. The culture of bile revealed positivity for Salmonella Typhi. Intra-venous antibiotic (ceftriaxone and gentamicin) was administered for 14 days. Four weeks later, cholecystectomy with peritoneal lavage was done. She was discharged on the 8th postoperative day.

Clinical discussion

Preoperative diagnosing of gallbladder perforation is challenging. The accurate treatment and precise timing of the surgery remain important. In most cases, cholecystectomy and abdominal lavage are adequate to treat gallbladder perforation.

Conclusions

Gallbladder perforation is a life-threatening surgical problem. The clinician should have a high index of awareness about this unusual surgical entity due to enteric fever and early diagnosis with prompt surgical intervention is necessary to improve patient outcomes.

•

Enteric fever is one of the major public health problems mainly in developing countries.

•

Gallbladder perforation is a very uncommon complication of enteric fever.

•

Awareness of this rare entity due to enteric fever is important for prompt timely management for better patient outcomes.

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.

Persistence of Antibody After a Vi-Tetanus Toxoid Conjugate Vaccine and Effect of Boosting With a Plain Polysaccharide Vaccine on Vi Antibody and Antigen-Specific B Cells

Background

Salmonella enterica serovar Typhi is estimated to cause 9 to 13 million cases of typhoid fever annually. Typhoid conjugate vaccines represent a promising prophylactic measure to prevent disease, but there are few data assessing persistence of immunity. The effect of a Vi polysaccharide booster vaccine in individuals previously vaccinated with the Vi-tetanus toxoid typhoid conjugate vaccine has not been assessed previously.

Methods

Thirty five healthy adult volunteers received a single dose of the Vi conjugate vaccine (Vi-TT) and 37 received a single dose of Vi polysaccharide vaccine (Vi-PS) prior to oral challenge with live S. Typhi bacteria as part of a randomised controlled, phase 2b study. In addition to data previously published showing persistence of Vi IgG and IgA antibodies for 7 months after Vi vaccination, titres were measured at intervals until 13 months post-vaccination. Ten participants who received Vi-TT (both challenged and unchallenged) were re-vaccinated with Vi-PS at an interval of 19-23 months post-prime. Anti-Vi IgG and IgA titres, and Vi-specific antibody secreting cells and memory B cells were measured at seven days and one month post-boost.

Findings

Vi IgG and IgA antibody titres remained significantly elevated above baseline levels 13 months after priming with Vi-TT, with a 4-fold rise retained in 90% and 88% of recipients (Vi IgG and IgA, respectively). Anti-Vi IgG and IgA antibody titres were found to persist at higher levels in participants who received a single dose of Vi-TT than in those who received Vi-PS. No significant boost in Vi-antibody titre was observed in response to oral challenge with S. Typhi bacteria, one month after vaccination. Following a Vi-PS booster vaccination in those previously vaccinated with Vi-TT, anti-Vi IgG and IgA titres were significantly elevated, with similar titres observed at one month post-boost compared with one month after primary vaccination. The frequency of Vi-specific IgA antibody secreting cells increased significantly 7 days post-boost compared with pre-boost. No memory B cell response was observed following Vi-PS booster vaccination.

Interpretation

Strong persistence of anti-Vi IgG and IgA following Vi-TT vaccination suggests that the conjugate vaccine may offer durable protection, supporting its use in endemic settings.

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.

IFN-alpha receptor deficiency enhances host resistance to oral Salmonella enterica serovar Typhimurium infection during murine pregnancy

PROBLEM

Maternal tolerance during pregnancy increases the risk of infection with certain intracellular pathogens. Systemic Salmonella enterica serovar Typhimurium (S.Tm) infection during pregnancy in normally resistant 129X1/SvJ mice leads to severe placental infection, as well as fetal and maternal deaths. However, the effect of oral infection with S.Tm in pregnant mice and the roles of infection-induced inflammation and cell death pathways in contributing to susceptibility to infection are unclear.

METHOD OF STUDY

Non-pregnant and pregnant C57BL/6J wild-type (WT) and cell death pathway-altered mice (IFNAR1^-/- , Caspase-1, 11^-/- , RIP3^-/- ) were infected orally with S.Tm. Host survival and fetal resorption were determined. Bacterial burden in mesenteric lymph nodes (MLNs), spleen, liver, and placentas was enumerated at various time points post-infection. Serum cytokine expression was measured through cytometric bead array.

RESULTS

Oral infection of WT mice with S.Tm on days 9-10 of gestation resulted in systemic dissemination of the bacteria, substantial placental colonization, and fetal loss 5 days post-infection. Histopathological examination of the placentas indicated that infection-induced widespread focal necrosis and neutrophil infiltration throughout the spongiotrophoblast (SpT) layer. In the non-pregnant state, IFNAR1^-/- mice exhibited increased survival following oral S.Tm infection relative to Caspase-1, 11^-/- , RIP3^-/- , and WT mice. The increased resistance to S.Tm infection in IFNAR1^-/- mice was seen during pregnancy as well, with decreased bacterial burden within MLNs, spleen, and placenta, which correlated with the decreased resorptions relative to WT and Caspase-1, 11^-/- mice.

CONCLUSION

Oral S.Tm exposure leads to placental infection, inflammation, and resorption, whereas IFNAR1 deficiency enhances host resistance both in the non-pregnant and pregnant states.