Nuclear factor kappa B-dependent persistence of Salmonella Typhi and Paratyphi in human macrophages

Salmonella serovars Typhi and Paratyphi cause a prolonged illness known as enteric fever, whereas other serovars cause acute gastroenteritis. Mechanisms responsible for the divergent clinical manifestations of nontyphoidal and enteric fever Salmonella infections have remained elusive. Here, we show that S. Typhi and S. Paratyphi A can persist within human macrophages, whereas S. Typhimurium rapidly induces apoptotic macrophage cell death that is dependent on Salmonella pathogenicity island 2 (SPI2). S. Typhi and S. Paratyphi A lack 12 specific SPI2 effectors with pro-apoptotic functions, including nine that target nuclear factor κB (NF-κB). Pharmacologic inhibition of NF-κB or heterologous expression of the SPI2 effectors GogA or GtgA restores apoptosis of S. Typhi-infected macrophages. In addition, the absence of the SPI2 effector SarA results in deficient signal transducer and activator of transcription 1 (STAT1) activation and interleukin 12 production, leading to impaired TH1 responses in macrophages and humanized mice. The absence of specific nontyphoidal SPI2 effectors may allow S. Typhi and S. Paratyphi A to cause chronic infections.

IMPORTANCE

Salmonella enterica is a common cause of gastrointestinal infections worldwide. The serovars Salmonella Typhi and Salmonella Paratyphi A cause a distinctive systemic illness called enteric fever, whose pathogenesis is incompletely understood. Here, we show that enteric fever Salmonella serovars lack 12 specific virulence factors possessed by nontyphoidal Salmonella serovars, which allow the enteric fever serovars to persist within human macrophages. We propose that this fundamental difference in the interaction of Salmonella with human macrophages is responsible for the chronicity of typhoid and paratyphoid fever, suggesting that targeting the nuclear factor κB (NF-κB) complex responsible for macrophage survival could facilitate the clearance of persistent bacterial infections.

Clinical and antimicrobial susceptibility profile of typhoid fever in children in the era of antibiotic resistance

Enteric fever remains a significant public health problem in low- and middle-income countries with further challenges from emerging antimicrobial resistance. Our prospective study evaluated the current clinical and antimicrobial susceptibility profile of enteric fever in 88 children and compared it to previously established literature. Enteric fever usually presents with nonspecific signs and symptoms, with predominant respiratory complaints. A paradigm shift in the antimicrobial sensitivity pattern has been noted, with increasing resistance for first-line antibiotics and older antibiotics such as ampicillin, cotrimoxazole, and chloramphenicol showing good sensitivity. Thus, the introduction of the latter merits consideration.

Typhoid Conjugate Vaccine: A Boon for Endemic Regions

Typhoid fever has the highest disease burden in countries in low- and middle-income countries, primarily located in Asia and Sub-Saharan Africa. Previous typhoid vaccines such as the live attenuated typhoid (Ty21a) vaccine and Vi (virulence) capsular polysaccharide vaccine had the limitation that they could not be administered with other standard childhood immunizations and were ineffective in children under two years of age. To address these shortcomings of the previous vaccines, typhoid conjugate vaccines (TCVs) were developed and prequalified by the World Health Organization. Cross-reacting material and tetanus toxoid are widely used as carrier proteins in TCVs. According to various studies, TCV has higher efficacy, has a more extended protection period, and is safe and immunogenic in infants as young as six months. This review article aims to comprehensively appraise the data available on TCVs' efficacy, duration of protection, safety, and immunogenicity in endemic regions.

Enteric Fever Presenting With Complete Heart Block (CHB): A Rare Case of Reversible Arrhythmia

Salmonella enterica serovar Typhi is the causative agent of enteric fever, commonly called "typhoid". This fever can be mistaken for a variety of other febrile disorders. It is an endemic sickness, especially in developing nations. Enteric fever typically manifests with fever, abdominal pain, and constitutional symptoms, making it a diagnostic challenge due to its broad clinical spectrum. Enteric fever also affects various other systems, causing complications, amongst which the cardiovascular system is no exception. Complications in the cardiovascular system may range from myocarditis to cardiomyopathy and various arrhythmias. This case report describes a case of a 28-year-old male who presented to us with fever and giddiness. Examination revealed profound bradycardia and electrocardiography (ECG) revealed features of a complete heart block (CHB). Investigations for fever confirmed enteric fever. This case report highlights one of the rarest complications of enteric fever.

ASVAC2022 : 8th Asian Vaccine Conference

Aiming to further the Immunization Partners in Asia Pacific (IPAP)'s vision of a world where no one suffers from a vaccine preventable disease, the 8^th Asian Vaccine Conference (ASVAC 2022) was held in Colombo, Sri Lanka and virtually from 15 to 18, September 2022 (www.asianvaccine.com). This conference followed those held in Siem Reap, Cambodia (2009), Manila, Philippines (2010), Jakarta, Indonesia (2011), Cebu, Philippines (2013), Hanoi, Vietnam (2015), Singapore (2017) and Naypyidaw and Yangon, Myanmar (2019). The ASVAC2022 themed "Immunization: in Era of Pandemics," commenced with the EPI Managers' Workshop, followed by pre-conference workshops and Vaccinology Masterclass, followed by the main conference featuring 5 plenary lectures, 6 partner-led symposia, free paper and poster presentations, and industry-supported lunch and evening sessions. There were over 1830 registered participants, with 112 attending in person and 998 virtually from 63 countries. The conference was organized by IPAP and hosted by the Vaccine and Infectious Disease Forum of Sri Lanka, Sri Lanka College of Pediatricians, Sri Lanka College of Microbiologists and College of General Practitioners of Sri Lanka, with the support of the Ministry of Health, Sri Lanka. The 9^th ASVAC is scheduled to be held in Davao City, Philippines in late 2023.

Association Among Household Water, Sanitation, and Hygiene (WASH) Status and Typhoid Risk in Urban Slums: Prospective Cohort Study in Bangladesh

BACKGROUND

Typhoid fever, or enteric fever, is a highly fatal infectious disease that affects over 9 million people worldwide each year, resulting in more than 110,000 deaths. Reduction in the burden of typhoid in low-income countries is crucial for public health and requires the implementation of feasible water, sanitation, and hygiene (WASH) interventions, especially in densely populated urban slums.

OBJECTIVE

In this study, conducted in Mirpur, Bangladesh, we aimed to assess the association between household WASH status and typhoid risk in a training subpopulation of a large prospective cohort (n=98,087), and to evaluate the performance of a machine learning algorithm in creating a composite WASH variable. Further, we investigated the protection associated with living in households with improved WASH facilities and in clusters with increasing prevalence of such facilities during a 2-year follow-up period.

METHODS

We used a machine learning algorithm to create a dichotomous composite variable ("Better" and "Not Better") based on 3 WASH variables: private toilet facility, safe drinking water source, and presence of water filter. The algorithm was trained using data from the training subpopulation and then validated in a distinct subpopulation (n=65,286) to assess its sensitivity and specificity. Cox regression models were used to evaluate the protective effect of living in "Better" WASH households and in clusters with increasing levels of "Better" WASH prevalence.

RESULTS

We found that residence in households with improved WASH facilities was associated with a 38% reduction in typhoid risk (adjusted hazard ratio=0.62, 95% CI 0.49-0.78; P<.001). This reduction was particularly pronounced in individuals younger than 10 years at the first census participation, with an adjusted hazard ratio of 0.49 (95% CI 0.36-0.66; P<.001). Furthermore, we observed an inverse relationship between the prevalence of "Better" WASH facilities in clusters and the incidence of typhoid, although this association was not statistically significant in the multivariable model. Specifically, the adjusted hazard of typhoid decreased by 0.996 (95% CI 0.986-1.006) for each percent increase in the prevalence of "Better" WASH in the cluster (P=.39).

CONCLUSIONS

Our findings demonstrate that existing variations in household WASH are associated with differences in the risk of typhoid in densely populated urban slums. This suggests that attainable improvements in WASH facilities can contribute to enhanced typhoid control, especially in settings where major infrastructural improvements are challenging. These findings underscore the importance of implementing and promoting comprehensive WASH interventions in low-income countries as a means to reduce the burden of typhoid and improve public health outcomes in vulnerable populations.

Early transcriptional responses to human enteric fever challenge

Enteric fever, caused by oral infection with typhoidal Salmonella serovars, presents as a non-specific febrile illness preceded by an incubation period of 5 days or more. The enteric fever human challenge model provides a unique opportunity to investigate the innate immune response during this incubation period, and how this response is altered by vaccination with the Vi polysaccharide or conjugate vaccine. We find that on the same day as ingestion of typhoidal Salmonella, there is already evidence of an immune response, with 199 genes upregulated in the peripheral blood transcriptome 12 hours post-challenge (false discovery rate <0.05). Gene sets relating to neutrophils, monocytes, and innate immunity were over-represented (false discovery rate <0.05). Estimating cell proportions from gene expression data suggested a possible increase in activated monocytes 12 hours post-challenge (P = 0.036, paired Wilcoxon signed-rank test). Furthermore, plasma TNF-α rose following exposure (P = 0.011, paired Wilcoxon signed-rank test). There were no significant differences in gene expression (false discovery rate <0.05) in the 12 hours response between those who did and did not subsequently develop clinical or blood culture confirmed enteric fever or between vaccination groups. Together, these results demonstrate early perturbation of the peripheral blood transcriptome after enteric fever challenge and provide initial insight into early mechanisms of protection.

Typhoid Intestinal Perforation Prognostic Score in Poor-Resource Settings

Background

Mortality from peritonitis due to typhoid intestinal perforation (TIP) in sub-Saharan Africa is high.

Objectives

This study aimed to determine the predictive factors of mortality, propose a prognostic score, and determine the appropriate surgical treatment for TIP in low-resource settings.

Materials and Methods

This was a retrospective data collection of peritonitis due to TIP admitted at Zinder National Hospital from 2014 to 2021. To build a typhoid intestinal perforation prognostic score (TIPPS), patients were randomised into two groups: a score-building group and a validation group. Univariate and multivariate analyses were performed to identify risk factors of mortality. The value of P <0.05 was assigned significant for all analyses.

Results

TIP accounted for 52.4% (n = 1132) of all cases of peritonitis (n = 2159). The median age was 12 years. Rural provenance represented 72.2% (n = 817). Deaths accounted for 10.5% (n = 119). The factors influencing mortality were respiratory rate ≥24/min (odds ratio [OR] = 2.6, P = 0.000), systolic blood pressure <90 mmHg (OR = 0.31, P = 0.002), serum creatinine >20 mg/L (OR = 2.6, P ≤ 0.009), haemoglobin (OR = 2.1, P = 0.000), comorbidity (OR = 3.5, P = 0.001), the American Society of Anesthesiologists score IV&V (OR = 3.3, P = 0.000), admission and management delay > 72 h (OR = 3.2, P = 0.001), and a number of perforations (OR = 2.4, P = 0.0001). These factors were used to build a "TIPPS" score, which ranged from 8 to 20. The risk of mortality was associated with increased TIPPS. The performance of this score was good in the two groups (area under receiver operating characteristic > 0.83). According to the severity and mortality risk of TIP, we classified TIPS into four grades: grade I (low risk: 8-10), grade II (moderate risk: 11-13), grade III (high risk: 14-16) and grade IV (very high risk: 17-20).

Conclusion

The TIPPS is simple. It can describe the severity of the disease and can predict the risk of death. The study highlights the importance and impact of timely and adequate perioperative resuscitation in more complicated cases.

Immunogenicity and protective efficacy of nanoparticle formulations of L-SseB against Salmonella infection

Salmonella enterica, a Gram-negative pathogen, has over 2500 serovars that infect a wide range of hosts. In humans, S. enterica causes typhoid or gastroenteritis and is a major public health concern. In this study, SseB (the tip protein of the Salmonella pathogenicity island 2 type III secretion system) was fused with the LTA1 subunit of labile-toxin from enterotoxigenic E. coli to make the self-adjuvanting antigen L-SseB. Two unique nanoparticle formulations were developed to allow multimeric presentation of L-SseB. Mice were vaccinated with these formulations and protective efficacy determined via challenging the mice with S. enterica serovars. The polysaccharide (chitosan) formulation was found to elicit better protection when compared to the squalene nanoemulsion. When the polysaccharide formulation was used to vaccinate rabbits, protection from S. enterica challenge was elicited. In summary, L-SseB in a particulate polysaccharide formulation appears to be an attractive candidate vaccine capable of broad protection against S. enterica.

Salmonella meningitis, an unusual complication of salmonella species: a case report from Nepal

Salmonella meningitis, caused by a Gram-negative bacillus of the Enterobacteriaceae family, is an uncommon but serious complication of Salmonella infection that can result in high mortality rates, significant neurological damage, and a high relapse rate, and has become a leading cause of Gram-negative bacterial meningitis in the developing world.

Case presentation

A 16-year-old boy presented with high-grade fever and altered sensorium for 2 days associated with vomiting, headache, and photophobia.

Case discussion

After invading the abdominal barrier, Salmonella can enter bloodstream and rarely present with meningitis. Cerebrospinal fluid analysis and culture supported with other investigations can diagnose bacterial meningitis and its causative agent. Adequate treatment is essential to completely cure and prevent relapse.

Conclusion

Given its invasive nature and potential serious consequences, such as relapse and antibiotic resistance, prompt, and appropriate treatment of Salmonella meningitis is essential.

Achieving Impact: Charting the Course to Meet the Challenges Ahead at the 12th International Conference on Typhoid and Other Invasive Salmonelloses

Typhoid fever and other invasive salmonelloses remain a major public health concern, primarily in low- and middle-income countries in Asia and Africa, where transmission occurs through contaminated food or water. However, recent developments in research, policy, and implementation offer newfound optimism for prevention and control. Now, more than ever, a coordinated and multisectoral global response is needed. To chart the course to meet the challenges ahead, the Coalition against Typhoid, housed at the Sabin Vaccine Institute, virtually organized the 12th International Conference on Typhoid and Other Invasive Salmonelloses from December 7 to 9, 2021. This commentary provides an overview of the conference's significant findings, highlighting barriers and opportunities for prevention and control. Topics covered include diagnostics advancements, improved data methodologies for a better understanding of the disease burden, the incorporation of environmental surveillance and genomics, the threat of drug resistance, and the use of typhoid conjugate vaccines alongside other integrated solutions.

Seroepidemiology for Enteric Fever: Emerging Approaches and Opportunities

Safe and effective typhoid conjugate vaccines (TCVs) are available, but many countries lack the high-resolution data needed to prioritize TCV introduction to the highest-risk communities. Here we discuss seroepidemiology-an approach using antibody response data to characterize infection burden-as a potential tool to fill this data gap. Serologic tests for typhoid have existed for over a hundred years, but only recently were antigens identified that were sensitive and specific enough to use as epidemiologic markers. These antigens, coupled with new methodological developments, permit estimating seroincidence-the rate at which new infections occur in a population-from cross-sectional serosurveys. These new tools open up many possible applications for enteric fever seroepidemiology, including generating high-resolution surveillance data, monitoring vaccine impact, and integrating with other serosurveillance initiatives. Challenges remain, including distinguishing Salmonella Typhi from Salmonella Paratyphi infections and accounting for reinfections. Enteric fever seroepidemiology can be conducted at a fraction of the cost, time, and sample size of surveillance blood culture studies and may enable more efficient and scalable surveillance for this important infectious disease.

Taking on Typhoid: Eliminating Typhoid Fever as a Global Health Problem

Typhoid fever is a significant global health problem that impacts people living in areas without access to clean water and sanitation. However, collaborative international partnerships and new research have improved both knowledge of the burden in countries with endemic disease and the tools for improved surveillance, including environmental surveillance. Two typhoid conjugate vaccines (TCVs) have achieved World Health Organization prequalification, with several more in the development pipeline. Despite hurdles posed by the coronavirus disease 2019 pandemic, multiple TCV efficacy trials have been conducted in high-burden countries, and data indicate that TCVs provide a high degree of protection from typhoid fever, are safe to use in young children, provide lasting protection, and have the potential to combat typhoid antimicrobial resistance. Now is the time to double down on typhoid control and elimination by sustaining progress made through water, sanitation, and hygiene improvements and accelerating TCV introduction in high-burden locations.

Salmonella Combination Vaccines: Moving Beyond Typhoid

There is now a robust pipeline of licensed and World Health Organization (WHO)-prequalified typhoid conjugate vaccines with a steady progression of national introductions. However, typhoid fever is responsible for less than half the total global burden of Salmonella disease, and even less among children aged <5 years. Invasive nontyphoidal Salmonella disease is the dominant clinical presentation of Salmonella in Africa, and over a quarter of enteric fever in Asia is due to paratyphoid A. In this article, we explore the case for combination Salmonella vaccines, review the current pipeline of these vaccines, and discuss key considerations for their development, including geographies of use, age of administration, and pathways to licensure. While a trivalent typhoid/nontyphoidal Salmonella vaccine is attractive for Africa, and a bivalent enteric fever vaccine for Asia, a quadrivalent vaccine covering the 4 main disease-causing serovars of Salmonella enterica would provide a single vaccine option for global Salmonella coverage.

Typhoid Control in an Era of Antimicrobial Resistance: Challenges and Opportunities

Historically, typhoid control has been achieved with water and sanitation interventions. Today, in an era of rising antimicrobial resistance (AMR), two World Health Organization-prequalified vaccines are available to accelerate control in the shorter term. Meanwhile, water and sanitation interventions could be implemented in the longer term to sustainably prevent typhoid in low- and middle-income countries. This article first approaches typhoid control from a historical perspective, subsequently presents how vaccination could complement water and sanitation activities, and finally discusses the challenges and opportunities for impactful control of typhoid infection. It also addresses data blind spots and knowledge gaps to focus on for typhoid control and to ultimately progress towards elimination. This article presents a synthesis of discussions held in December 2021 during a roundtable session at the "12th International Conference on Typhoid and Other Invasive Salmonelloses".

Vi polysaccharide and conjugated vaccines afford similar early, IgM or IgG-independent control of infection but boosting with conjugated Vi vaccines sustains the efficacy of immune responses

Introduction

Vaccination with Vi capsular polysaccharide (Vi-PS) or protein-Vi typhoid conjugate vaccine (TCV) can protect adults against Salmonella Typhi infections. TCVs offer better protection than Vi-PS in infants and may offer better protection in adults. Potential reasons for why TCV may be superior in adults are not fully understood.

Methods and results

Here, we immunized wild-type (WT) mice and mice deficient in IgG or IgM with Vi-PS or TCVs (Vi conjugated to tetanus toxoid or CRM197) for up to seven months, with and without subsequent challenge with Vi-expressing Salmonella Typhimurium. Unexpectedly, IgM or IgG alone were similarly able to reduce bacterial burdens in tissues, and this was observed in response to conjugated or unconjugated Vi vaccines and was independent of antibody being of high affinity. Only in the longer-term after immunization (>5 months) were differences observed in tissue bacterial burdens of mice immunized with Vi-PS or TCV. These differences related to the maintenance of antibody responses at higher levels in mice boosted with TCV, with the rate of fall in IgG titres induced to Vi-PS being greater than for TCV.

Discussion

Therefore, Vi-specific IgM or IgG are independently capable of protecting from infection and any superior protection from vaccination with TCV in adults may relate to responses being able to persist better rather than from differences in the antibody isotypes induced. These findings suggest that enhancing our understanding of how responses to vaccines are maintained may inform on how to maximize protection afforded by conjugate vaccines against encapsulated pathogens such as S. Typhi.

Typhoid Fever Complicated by Rhabdomyolysis with Acute Hepatitis, Splenic Infarct, Pancreatitis, and Acute Kidney Injury

Typhoid fever is a potentially life-threatening infectious disease that presents itself with a wide array of symptoms ranging from uncomplicated fever to sepsis with multiorgan dysfunction syndrome. An 18-year-old male college student presented with progressively increasing fever with abdominal discomfort, anorexia, and persistent vomiting. Typhoid fever was suspected in view of clinical findings along with leukopenia, grossly elevated transaminases, and acute kidney injury. He was managed with intravenous (IV) antibiotics, which resulted in the resolution of fever and other symptoms. Rhabdomyolysis is an extremely rare complication in typhoid fever, which is a very common cause of fever in tropical countries, leading to acute renal failure, causing very high morbidity and mortality.

The Prevalence of Multi-Drug Resistant Salmonella typhi Isolated From Blood Sample

Typhoid is a major public health concern. Even though antibiotics are usually used to treat typhoid fever, the spread of multi drug resistant Salmonella typhi is making antibiotics much less effective. This study was conducted to assess the prevalence of multidrug-resistant Salmonella typhi from the clinical samples. During this study, 154 blood samples of suspected typhoid patients were collected from the hospital and diagnostic center located in Chattogram City, Bangladesh. Isolation and identification of Salmonella typhi was done by both biochemical tests. PCR analysis was also done for the confirmation of biochemical result. Antimicrobial susceptibility test was performed according to the Kirby-Bauer disk diffusion method against ampicillin, chloramphenicol, cefepime, cotrimoxazole, ceptriaxone, ciprofloxacin, nalidixic acid, and azithtomycin. Out of 154, 21 (13.64%) isolates were identified as Salmonella typhi and the prevalence of typhoid in Chattogram, Bangladesh was 13.64% (n = 21). It was also found that children under the age of 5 are the more vulnerable target of Salmonella typhi infection. Antibiotic resistance profiling revealed 85% isolates were Multi-Drug Resistant (MDR) and highest resistance was found in case of Nalidixic acid. Although, most of the isolated Salmonella typhi were MDR, first generation antibiotics Co-trimoxazile, Chloramphenicol, and Ampicillin were found effective against Salmonella typhi.

Comparative Analysis of Commercially Available Typhoid Point-of-Care Tests: Results of a Prospective and Hybrid Retrospective Multicenter Diagnostic Accuracy Study in Kenya and Pakistan

Blood and bone marrow cultures are considered the gold standard for the diagnosis of typhoid, but these methods require infrastructure and skilled staff that are not always available in low- and middle-income countries where typhoid is endemic. The objective of the study is to evaluate the sensitivity and specificity of nine commercially available Salmonella Typhi rapid diagnostic tests (RDTs) using blood culture as a reference standard in a multicenter study. This was a prospective and retrospective multicenter diagnostic accuracy study conducted in two geographically distant areas where typhoid is endemic (Pakistan and Kenya; NCT04801602). Nine RDTs were evaluated, including the Widal test. Point estimates for sensitivity and specificity were calculated using the Wilson method. Latent class analyses were performed using R to address the imperfect gold standard. A total of 531 serum samples were evaluated (264 blood culture positive; 267 blood culture negative). The sensitivity of RDTs varied widely (range, 0 to 78.8%), with the best overall performance shown by Enterocheck WB (72.7% sensitivity, 86.5% specificity). In latent class modeling, CTK IgG was found to have the highest sensitivity (79.1%), while the highest overall accuracy was observed with Enterocheck (73.8% sensitivity, 94.5% specificity). All commercially available Salmonella Typhi RDTs evaluated in the study had sensitivity and specificity values that fell below the required levels to be recommended for an accurate diagnosis. There were minimal differences in RDT performances between regions of endemicity. These findings highlight the clear need for new and more-accurate Salmonella Typhi tests.

Disparities in Coverage of Adult Immunization among Older Adults in India

A lack of a universal adult immunization scheme in India poses a challenge to achieve universal health coverage. Healthcare disparity is one of the biggest challenges in low- and middle-income countries such as India. We aimed to estimate the disparities in coverage of various adult vaccines among older adults in India using nationally representative data. An observational analysis among 31,464 participants aged ≥60 years from the Longitudinal Ageing Study in India, 2017-2018, was conducted. Vaccination coverage across wealth quintiles and selected non-communicable diseases were reported as frequencies and weighted proportions along with their 95% confidence intervals as a measure of uncertainty. The highest coverage was of the diphtheria and tetanus vaccine (2.75%) followed by typhoid (1.84%), hepatitis B (1.82%), influenza (1.59%), and pneumococcal (0.74%). The most affluent groups had a higher coverage of all vaccines. Participants having high cholesterol, psychiatric conditions, and cancer had the highest coverage of all vaccines. Overall, a very low coverage of all vaccines was observed. The coverage was influenced by social determinants of health, depicting a disparity in accessing immunization. Hence, at-risk groups such as the deprived and multimorbid patients need to be covered under the ambit of free immunization to achieve universal health coverage.

The Effect of the Gallbladder Environment during Chronic Infection on Salmonella Persister Cell Formation

Typhoid fever is caused by Salmonella enterica serovar Typhi (S. Typhi). Around 3-5% of individuals infected become chronic carriers, with the gallbladder (GB) as the predominant site of persistence. Gallstones (GS) aid in the development and maintenance of GB carriage, serving as a substrate to which Salmonellae attach and form a biofilm. This biofilm matrix protects bacteria from the host immune system and environmental stress. This shielded environment is an ideal place for the development of persister cells, a transient phenotype of a subset of cells within a population that allows survival after antibiotic treatment. Persisters can also arise in response to harsh environments such as the GB. Here we investigate if GB conditions affect the number of persisters in a Salmonella population. To simulate the chronic GB environment, we cultured biofilms in cholesterol-coated 96-well plates in the presence of ox or human bile. We then treated planktonic or biofilm Salmonella cultures with high concentrations of different antibiotics. This study suggests that biofilms provide a niche for persister cells, but GB conditions either play no role or have a negative influence on persister formation, especially after kanamycin treatment. The antibiotic target was important, as antimicrobials directed against DNA replication or the cell wall had no effect on persister cell formation. Interestingly, repeated treatment with ciprofloxacin increased the percentage of S. Typhimurium persisters in a biofilm, but this increase was abolished by GB conditions. On the other hand, repeated ciprofloxacin treatment of S. Typhi biofilms in GB conditions slightly increased the fraction of persisters. Thus, while the harsh conditions in the GB would be thought to give rise to increased persisters, therefore contributing to the development of chronic carriage, these data suggest persister cell formation is dampened in this environment.

Detection of Salmonella Typhi in Bile by Quantitative Real-Time PCR

In countries where the incidence of typhoid fever is high, fecal material from short-term carriers of Salmonella Typhi contaminates inadequately treated water supplies. As treated water supplies and improved sanitation become available, chronic (mainly gallbladder) carriers of S. Typhi become important. The objective of this study was to develop a method for detection of S. Typhi in bile by quantitative real-time PCR (qPCR) in patients undergoing cholecystectomy. We evaluated sensitivity and specificity of probesets that target oriC, viaB, fliC-d, STY0201, and stoD. We optimized DNA extraction from bile and compared the sensitivity of culture and our qPCR method to detect S. Typhi in bile samples containing various cephalosporins. With the use of an optimized DNA extraction technique, our limit of detection of S. Typhi in spiked human bile samples was 7.4 × 102 CFU/mL. We observed that S. Typhi could be detected by qPCR in samples containing cefazolin, cefotaxime, or ceftriaxone whereas culture could only detect Typhi in samples containing cefazolin but not cefotaxime or ceftriaxone. Our qPCR detection method for S. Typhi in bile should be preferred in areas where antibiotic usage is common. IMPORTANCE New Salmonella Typhi conjugate vaccines have been deployed, which will potentially lead to a fall in incidence rates of typhoid fever in endemic areas. Identification of chronic carriers of S. Typhi will be important as these individuals can be a potential source of transmission to susceptible persons. To address this public health concern, we have developed a novel method to detect S. Typhi in bile using real-time PCR. Our method can be used to identify carriers of S. Typhi among patients undergoing cholecystectomy (gallbladder removal surgery). The sensitivity of our molecular-based assay was superior to culture when performed in the presence of antibiotics commonly used during surgery. Our methodology will complement efforts to eliminate typhoid disease.

The Complex Mechanism of the Salmonella typhi Biofilm Formation That Facilitates Pathogenicity: A Review

Salmonella enterica serovar Typhi (S. typhi) is an intracellular pathogen belonging to the Enterobacteriaceae family, where biofilm (aggregation and colonization of cells) formation is one of their advantageous traits. Salmonella typhi is the causative agent of typhoid fever in the human body and is exceptionally host specific. It is transmitted through the fecal-oral route by consuming contaminated food or water. This subspecies is quite intelligent to evade the innate detection and immune response of the host body, leading to systemic dissemination. Consequently, during the period of illness, the gallbladder becomes a harbor and may develop antibiotic resistance. Afterwards, they start contributing to the continuous damage of epithelium cells and make the host asymptomatic and potential carriers of this pathogen for an extended period. Statistically, almost 5% of infected people with Salmonella typhi become chronic carriers and are ready to contribute to future transmission by biofilm formation. Biofilm development is already recognized to link with pathogenicity and plays a crucial role in persistency within the human body. This review seeks to discuss some of the crucial factors related to biofilm development and its mechanism of interaction causing pathogenicity. Understanding the connections between these things will open up a new avenue for finding therapeutic approaches to combat pathogenicity.

In vitro and in silico screening of novel typhoid drugs from endangered herb (Enicostema axillare)

In the present study, antibacterial activity of swertiamarin from Enicostema axillare (Lam) was checked against three different human gram-negative pathogens namely Salmonella typhi, Klebsiella pneumoniae and Shigella flexneri. Minimum inhibitory concentration assay revealed low dose and efficient activity of swertiamarin on the above said pathogens. Though swertiamarin is a well-studied and characterized compound, there is no experimental proof available for its antibacterial activity. To gain more insight about the antibacterial efficiency of swertiamarin against typhoid causing S. typhi, a comparative molecular docking of S. typhi OmpF (3NSG) was performed with swertiamarin and other typhoid drugs available in the market which exposed better activity strength of swertiamarin compared with that of the other drugs. Further, molecular dynamics of S. typhi OmpF-swertiamarin shows good flexibility and stability at 100 ns. The outcome of this work will definitely provide an idea of using very low dose of swertiamarin as a potent and promising drug against typhoid fever. Communicated by Ramaswamy H. Sarma.

Climate and Disease vulnerability analysis in blocks of Kalahandi District of Odisha, India

BACKGROUND

Diarrhea and typhoid, ancient water-borne diseases which are highly connected to rainfall are serious public health challenges in the blocks of Kalahandi district of Odisha, India.

OBJECTIVES

Corroboration of rainfall and waterborne diseases are available in abundance; therefore, the objective of this article is to calculate the climate and disease vulnerability index (CDVI) value for each block of Kalahandi.

METHODS

We have applied the livelihood vulnerability index with some modifications and classify the three major categories, i.e., exposure, sensitivity, and adaptive capacity into six subcategories. These six subcategories are further divided into 26 vulnerability indicators based on a detailed literature review.

RESULTS

The result indicated that the Thuamul Rampur block, the southernmost part of the district is highly exposed to the annual and seasonal mean rainfall, and the Madanpur Rampur block lies in the northernmost part of the district is highly exposed to diarrhea and typhoid. Based on the calculation of the final CDVI value, nearly 50% of blocks of the Kalahandi district fall in the category of very high to high vulnerable zones. Furthermore, it has been observed that factors such as rainfall and disease distribution, vulnerable population and infrastructure, and education and health-care capacities had a notable influence on vulnerability.

CONCLUSION

It is rare to find a health vulnerability-related study in India at this microlevel based on the suitable indicators selected for a tribal and backward region.

Surge of Typhoid Intestinal Perforations as Possible Result of COVID-19-Associated Delays in Seeking Care, Madagascar

During the coronavirus disease pandemic, we observed a 6.4-fold increase in typhoid intestinal perforation incidence in Antananarivo, Madagascar. Thirteen perforations occurred within 6 months (February 2020–July 2020), compared with 13 perforations during the previous 41 months (August 2016–January 2020). The increase may be attributable to delayed healthcare seeking during the pandemic.

Water, Sanitation, and Hygiene Practices in Urban Slums of Eastern India

Background

The Sustainable Development Goals identified universal access to water and sanitation facilities as key components for improving health. We assessed water, sanitation, and hygiene (WASH) practices and associated determinants among residents of urban slums in Kolkata, India.

Methods

Information on WASH practices was collected in 2 surveys (2018 and 2019) from participants of a prospective enteric fever surveillance conducted in 2 municipal wards of Kolkata. A composite WASH practice score was computed and a hierarchical stepwise multiple linear regression model constructed to identify key determinants of improved WASH score.

Results

Over 90% of households had access to piped water; 6% reported access to continuous supply. Adult women (61% in 2018; 45% in 2019) spent 20 minutes daily to fetch water. Access to improved latrines was almost universal, although 80% used shared facilities. Unhealthy disposal of children’s stools was reported in both rounds. Food hygiene practices were high, with most (>90%) washing uncooked items before eating; frequent consumption of street food items was reported.

Conclusions

The study area reported high WASH coverage. Unhygienic behavioral patterns predisposing to food- or water-borne diseases were also noted. Awareness building and sustainable community mobilization for food hygiene needs to be emphasized to ensure community well-being.

Case-Control Study of Household and Environmental Transmission of Typhoid Fever in India

Background

Typhoid fever causes substantial morbidity and mortality in low- and middle-income countries. We conducted a case-control study in Vellore, southern India, to understand risk factors for transmission of typhoid.

Methods

From April 2018 to October 2019, households of blood culture-confirmed typhoid cases that occurred within a fever surveillance cohort aged 6 months–15 years, and controls matched for age, sex, geographic location, and socioeconomic status, were recruited. Information on risk factors was obtained using standard questionnaires. Household and environmental samples were collected for detection of Salmonella Typhi using real-time polymerase chain reaction. Multivariable analysis was used to evaluate associations between risk factors and typhoid.

Results

One hundred pairs of cases and controls were recruited. On multivariable regression analysis, mothers eating food from street vendors during the previous week (odds ratio [OR] = 2.04; 95% confidence interval [CI], 1.03–4.12; P = .04) was independently associated with typhoid, whereas treatment of household drinking water (OR = 0.45; 95% CI, 0.25–0.80; P = .007) was protective. There was no significant difference in S Typhi detection between the environmental samples from case and control households.

Conclusions

Street-vended food is a risk factor for typhoid in densely populated urban communities of Vellore. Improved sanitation facilities and awareness about point-of-use water treatment are likely to contribute to typhoid control.

Genomic Epidemiology and Antimicrobial Resistance Mechanisms of Imported Typhoid in Australia

Typhoid fever is an invasive bacterial disease of humans that disproportionately affects low- and middle-income countries. Antimicrobial resistance (AMR) has been increasingly prevalent in recent decades in Salmonella enterica serovar Typhi (S. Typhi), the causative agent of typhoid fever, limiting treatment options. In Australia, most cases of typhoid fever are imported due to travel to regions where typhoid fever is endemic. Here, all 116 isolates of S. Typhi isolated in Victoria, Australia, between 1 July 2018 and 30 June 2020, underwent whole-genome sequencing and antimicrobial susceptibility testing. Genomic data were linked to international travel data collected from routine case interviews. Travel to South Asia accounted for most cases, with 92.2% imported from seven primary countries (the top two were India, n = 87, and Pakistan, n = 12). A total of 17 S. Typhi genotypes were detected in the 2-year cohort, with 48.2% genotyped as part of global AMR lineages. Ciprofloxacin resistance was detected in two lineages, 3.3 and 4.3.1.2, all from cases with reported travel to India. Nearly all multidrug and extensively drug resistant isolates (90%) were from cases with reported travel to Pakistan in genotypes 4.3.1.1 and 4.3.1.1.P1. Extended spectrum beta-lactamases, blaCTX-M-15 and blaSHV-12, were detected in cases with travel to Pakistan and India, respectively. Linking epidemiological data with genomic studies of S. Typhi provides an opportunity to improve understanding of the emergence, spread and risk of drug-resistant S. Typhi infections and to better inform empirical treatment guidelines in returned travelers.

Whole Genome Sequencing Analysis of Salmonella enterica Serovar Typhi: History and Current Approaches

In recent years, the advance in whole-genome sequencing technology has changed the study of infectious diseases. The emergence of genome sequencing has improved the understanding of infectious diseases, which has revamped many fields, such as molecular microbiology, epidemiology, infection control, and vaccine production. In this review we discuss the findings of Salmonella enterica serovar Typhi genomes, publicly accessible from the initial complete genome to the recent update of Salmonella enterica serovar Typhi genomes, which has greatly improved Salmonella enterica serovar Typhi and other pathogen genomic research. Significant information on genetic changes, evolution, antimicrobial resistance, virulence, pathogenesis, and investigation from the genome sequencing of S. Typhi is also addressed. This review will gather information on the variation of the Salmonella enterica serovar Typhi genomes and hopefully facilitate our understanding of their genome evolution, dynamics of adaptation, and pathogenesis for the development of the typhoid point-of-care diagnostics, medications, and vaccines.

Revisiting Persistent Salmonella Infection and the Carrier State: What Do We Know?

One characteristic of the few Salmonella enterica serovars that produce typhoid-like infections is that disease-free persistent infection can occur for months or years in a small number of individuals post-convalescence. The bacteria continue to be shed intermittently which is a key component of the epidemiology of these infections. Persistent chronic infection occurs despite high levels of circulating specific IgG. We have reviewed the information on the basis for persistence in S. Typhi, S. Dublin, S. Gallinarum, S. Pullorum, S. Abortusovis and also S. Typhimurium in mice as a model of persistence. Persistence appears to occur in macrophages in the spleen and liver with shedding either from the gall bladder and gut or the reproductive tract. The involvement of host genetic background in defining persistence is clear from studies with the mouse but less so with human and poultry infections. There is increasing evidence that the organisms (i) modulate the host response away from the typical Th1-type response normally associated with immune clearance of an acute infection to Th2-type or an anti-inflammatory response, and that (ii) the bacteria modulate transformation of macrophage from M1 to M2 type. The bacterial factors involved in this are not yet fully understood. There are early indications that it might be possible to remodulate the response back towards a Th1 response by using cytokine therapy.

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.

Traditional Widal Agglutination Test Versus Rapid Immunochromatographic Test in the Diagnosis of Enteric Fever: A Prospective Study From South India

Introduction Early diagnosis and treatment are crucial to reducing the morbidity of patients with enteric fever/typhoid fever. Among the available diagnostic tests, the blood culture is considered a gold standard. However, in most of the developing and resource-limited settings, the diagnosis is made utilizing the traditional Widal test and rapid immunochromatographic test (ICT). This study was aimed to compare the diagnostic value and efficacy of ICT and traditional Widal test in the diagnosis of typhoid fever. Methods A prospective study was conducted, and 40 patients were included in the study. The Widal test and Salmonella enterica serovar Typhi IgM/IgG immunochromatographic test were performed for all the patients. The Widal is a tube agglutination test, and the rapid ICT utilizes the principle of enzyme-linked immunosorbent assay (ELISA). All the samples were also tested for the presence of antibodies (IgG and IgM) against the S. enterica serovar Typhi and the titers against 'O' and 'H' antigens of S. enterica serovar Typhi. An antibody titer of 1:80 or more against the 'O' and 'H' antigen was considered positive. Results In the ICT, 24 samples (60%) tested positive for the IgM antibodies, and only 15 samples tested positive and for IgG antibodies. In the Widal test, 27 samples (67.6%) returned positive for antibodies against the S. enterica serovar Typhi 'O' antigen. The sensitivity (90% vs 72.73%), specificity (81.25% vs 64%), and accuracy (82.12% vs 64.87%) for the Widal test were found to be more when compared to the ICT. Conclusion The results indicate that the traditional Widal agglutination test is superior to the rapid ICT in the diagnosis of enteric fever. However, both these tests cannot be considered as gold standards for the diagnosis owing to their low positive predictive values.

Typhoid Conjugate Vaccine - an urgent tool to combat typhoid, and tackle antimicrobial resistance

Typhoid is endemic in many countries in South Asia and sub-Saharan Africa. The high burden of this age-old, preventable disease exacerbates constraints on the health systems of these countries. Currently, most patients are treated effectively in the community or outpatient departments, however, with rising antimicrobial resistance and the dearth of novel antimicrobials in the horizon, we risk losing our primary defense against typhoid. Extensively drug-resistant Salmonella Typhi is spreading, and azithromycin is the last oral drug to continue treating typhoid in the community. With increasing azithromycin resistance, emergence of pan-oral drug resistant Salmonella Typhi is imminent. The high burden of typhoid is also an underlying cause of the unnecessary use of antimicrobials. In addition to implementing water sanitation and hygiene interventions to prevent typhoid, it is imperative to rapidly roll out typhoid conjugate vaccines in endemic countries. This will not only reduce the burden of typhoid, but also aid in interrupting the trend of increasing antimicrobial resistance.

Performance of Immunodiagnostic Tests for Typhoid Fever: A Systematic Review and Meta-Analysis

Typhoid fever, also known as typhoid, is a life-threatening bacterial infection that remains a global health concern. The infection is associated with a significant morbidity and mortality rate, resulting in an urgent need for specific and rapid detection tests to aid prevention and management of the disease. The present review aims to assess the specificity and sensitivity of the available literature on the immunodiagnostics of typhoid fever. A literature search was conducted using three databases (PubMed, ProQuest and Scopus) and manual searches through the references of identified full texts to retrieve relevant literature published between 1 January 2011 and 31 December 2020. Of the 577 studies identified in our search, 12 were included in further analysis. Lipopolysaccharides (LPS) and hemolysin E (HlyE) were the most frequently studied antigens. The specimens examined in these studies included serum and saliva. Using blood culture as the gold standard, anti-LPS IgA gave the highest sensitivity of 96% (95% CI: 93–99) and specificity of 96% (95% CI: 93–99) for distinguishing between typhoid cases and healthy controls, whereas the combination of anti-LPS and anti-flagellin total IgGAM gave the highest sensitivity of 93% (95% CI: 86–99) and specificity of 95% (95% CI: 89–100) for distinguishing typhoid cases and other febrile infections. A comparably high sensitivity of 92% (95% CI: 86–98) and specificity of 89% (95% CI: 78–100) were shown in testing based on detection of the combination of anti-LPS (IgA and IgM) and anti-HlyE IgG as well as a slightly lower sensitivity of 91% (95% CI: 74–100) in the case of anti-50kDa IgA. Anti-50kDa IgM had the lowest sensitivity of 36% (95% CI: 6–65) against both healthy and febrile controls. The development of a rapid diagnostic test targeting antibodies against lipopolysaccharides combined with flagellin appeared to be a suitable approach for the rapid detection test of typhoid fever. Saliva is added benefit for rapid typhoid diagnosis since it is less invasive. As a result, further studies could be done to develop additional approaches for adopting such samples.

Multiple introductions of multidrug-resistant typhoid associated with acute infection and asymptomatic carriage, Kenya

Background:

Understanding the dynamics of infection and carriage of typhoid in endemic settings is critical to finding solutions to prevention and control.

Methods:

In a 3-year case-control study, we investigated typhoid among children aged <16 years (4670 febrile cases and 8549 age matched controls) living in an informal settlement, Nairobi, Kenya.

Results:

148 S. Typhi isolates from cases and 95 from controls (stool culture) were identified; a carriage frequency of 1 %. Whole-genome sequencing showed 97% of cases and 88% of controls were genotype 4.3.1 (Haplotype 58), with the majority of each (76% and 88%) being multidrug-resistant strains in three sublineages of the H58 genotype (East Africa 1 (EA1), EA2, and EA3), with sequences from cases and carriers intermingled.

Conclusions:

The high rate of multidrug-resistant H58 S. Typhi, and the close phylogenetic relationships between cases and controls, provides evidence for the role of carriers as a reservoir for the community spread of typhoid in this setting.

Funding:

National Institutes of Health (R01AI099525); Wellcome Trust (106158/Z/14/Z); European Commission (TyphiNET No 845681); National Institute for Health Research (NIHR); Bill and Melinda Gates Foundation (OPP1175797).

Optimized methods for detecting Salmonella Typhi in the environment using validated field sampling, culture and confirmatory molecular approaches

AIMS

This study evaluated detection methods for Salmonella Typhi (S. Typhi) in the environment, to establish a novel pathway from field sampling to isolation of viable organisms and molecular confirmation from complex environmental samples, thus enabling environmental surveillance of typhoid.

METHODS AND RESULTS

Multiple media were assessed using clinical isolates from the Public Health England's (PHE) Culture collection. The culture pathway selected consisted of a primary 2% bile broth and secondary Selenite F broth, followed by modified Chromogenic Agar for Salmonella Esterase (mCASE). A qPCR assay was adapted from a validated S. Typhi PCR panel for confirmation of isolates, with comparison to biochemical and serological tests showing good specificity. Sampling locations in Blantyre, Malawi were used to compare sampling methods. Viable S. Typhi were isolated from a mixture of trap and grab river water samples on six occasions.

CONCLUSIONS

Culture of viable S. Typhi from environmental samples was possible using effective capture and culture techniques.

SIGNIFICANCE AND IMPACT OF STUDY

Whilst several studies have attempted to detect S. Typhi from the environment, this is the first successful attempt to isolate the organism from river water since the 1980s. Supplementing clinical data with environmental screening offers the potential for enhanced surveillance, which might inform interventions and assess vaccination programmes.

Miller Fisher Syndrome and Boomerang Sign: A Rare Presentation of Typhoid Fever

Miller Fischer syndrome (MFS) is a variant of Guillain-Barré syndrome which is characterized by a triad of ataxia, ophthalmoplegia, and areflexia. It is uncommonly associated with systemic illnesses. We present the case of a young boy who came back after a trip to New Delhi in India, who developed MFS. MRI showed a callosal splenial hyperintensity which is called the boomerang sign. The evaluation revealed typhoid fever. This is probably the first such report of MFS associated with this infection.

Enteric fever presenting as catatonia syndrome - Case report

Enteric or typhoid fever is an emerging tropical infectious disease and a global public health problem with a documented spectrum of neuro-psychiatric manifestations especially from endemic countries. Although neuro-psychiatric manifestations are reported in nearly 50-75% of patients at any phase of enteric fever, the chance of their misdiagnosis and deferred diagnosis of the prime illness is quite common. Atypical symptoms are commonly attributed to be a part of 'typhoid toxaemia', the acute febrile phase of the illness. We report a case of young male presenting with catatonia in the aftermath of such.

Estimation of Baseline Widal Antibody Titers among Apparently Healthy Urban Population of District Jammu

Introduction:

Definitive diagnosis of Enteric fever is by blood culture for Salmonella enterica serotype Typhi, Paratyphi A, and Paratyphi B which takes long turnaround time and is costly, whereas Widal test is simple, rapid, and cost-effective test whose interpretation depends on the baseline Widal titers among healthy individuals in a defined population.

Objectives:

To determine the baseline Widal titers among apparently healthy urban population of district Jammu (J&K).

Materials and Methods:

302 individuals in the age group of 18–50 years were recruited. A pretested questionnaire was used to collect demographic and clinical details. The Widal testing was done using commercial Salmonella antigen kit.

Results:

A total of 302 samples were screened by Widal test. 138 samples (45.69%) were reactive for TO antigen and 64 (21.19%) tested reactive for TH antigen, 3 (0.01%) samples showed agglutination for AH antigen and 3 (0.01%) were positive for BH antigen. Majority of seropositive samples were in dilutions of 1:40 for both TO and TH antigens.

Conclusions:

Hence, next higher dilutions showing positivity for both TO and TH antigens, i.e., ≥1:80 may be considered diagnostic for enteric fever in the urban population of Jammu district.

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.

Detection of Salmonella genes in stool samples of children aged 5 years and younger in urban and rural areas of Bangladesh

INTRODUCTION

Typhoid incidence in children is higher in urban areas than in rural areas of Bangladesh. This study examined whether healthy urban children harboured higher levels of Salmonella genes than healthy rural children.

METHODOLOGY

Stool samples from 140 children were studied: 70 from rural areas and 70 from urban metropolitan areas.

RESULTS

The stool samples of urban children contained more Salmonella genes (median 4, IQR 3-4) than those of rural children (median 3, IQR 3-4). This suggests that urban Bangladeshi children have more Salmonella genes in their guts than rural children. Especially, in those under 12 months of age, the Salmonella gene prevalence in urban children was unique. They had more Salmonella genes (median 4, IQR 4-5) than rural children in the same age group (median 3, IQR 2.5-4). We also found more Salmonella genes in urban children who drank tap water (median 4, IQR 3-5) than in rural children whose water source was tube well water (median 3, IQR 2-4) and boiled pond water (median 3, IQR 3-3.5). However, there was no significant difference of Salmonella genes between urban children who drank tap-water and children whose water source was a tube well (median 4, IQR 3-4).

CONCLUSIONS

These data suggest that the urban environment, including the drinking water supply system, increases the likelihood of healthy children in urban areas harbouring more potentially pathogenic Salmonella organisms in their gut than found in rural healthy children.

Antibiotic Use Prior to Hospital Presentation Among Individuals With Suspected Enteric Fever in Nepal, Bangladesh, and Pakistan

Background

Antibiotic use prior to seeking care at a hospital may reduce the sensitivity of blood culture for enteric fever, with implications for both clinical care and surveillance. The Surveillance for Enteric Fever in Asia Project (SEAP) is a prospective study of enteric fever incidence in Nepal, Bangladesh, and Pakistan. Nested within SEAP, we evaluated the accuracy of self-reported antibiotic use and investigated the association between antibiotic use and blood culture positivity.

Methods

Between November 2016 and April 2019, we collected urine samples among a subset of SEAP participants to test for antibiotic use prior to the hospital visit using an antibacterial activity assay. All participants were asked about recent antibiotic use and had a blood culture performed. We used mixed-effect logit models to evaluate the effect of antimicrobial use on blood culture positivity, adjusted for markers of disease severity.

Results

We enrolled 2939 patients with suspected enteric fever. Antibiotics were detected in 39% (1145/2939) of urine samples. The correlation between measured and reported antibiotic use was modest (κ = 0.72). After adjusting for disease severity, patients with antibiotics in their urine were slightly more likely to be blood culture positive for enteric fever; however, the effect was not statistically significant (prevalence ratio, 1.22 [95% confidence interval, .99–1.50]).

Conclusions

The reliability of self-reported prior antibiotic use was modest among individuals presenting with fever to tertiary hospitals. While antibiotics are likely to reduce the sensitivity of blood culture, our findings indicate that there is still considerable value in performing blood culture for individuals reporting antibiotic use.

Early Insights From Clinical Trials of Typhoid Conjugate Vaccine

Clinical trials of typhoid conjugate vaccine (TCV) are ongoing in 4 countries. Early data confirm safety, tolerability, and immunogenicity of typhoid conjugate vaccine, and early efficacy results are promising. These data support World Health Organization recommendations and planned country introductions. Forthcoming trial data will continue to inform programmatic use of typhoid conjugate vaccine.

Decision Making and Implementation of the First Public Sector Introduction of Typhoid Conjugate Vaccine-Navi Mumbai, India, 2018

BACKGROUND

Typhoid fever prevention and control efforts are critical in an era of rising antimicrobial resistance among typhoid pathogens. India remains one of the highest typhoid disease burden countries, although a highly efficacious typhoid conjugate vaccine (TCV), prequalified by the World Health Organization in 2017, has been available since 2013. In 2018, the Navi Mumbai Municipal Corporation (NMMC) introduced TCV into its immunization program, targeting children aged 9 months to 14 years in 11 of 22 areas (Phase 1 campaign). We describe the decision making, implementation, and delivery costing to inform TCV use in other settings.

METHODS

We collected information on the decision making and campaign implementation in addition to administrative coverage from NMMC and partners. We then used a microcosting approach from the local government (NMMC) perspective, using a new Microsoft Excel-based tool to estimate the financial and economic vaccination campaign costs.

RESULTS

The planning and implementation of the campaign were led by NMMC with support from multiple partners. A fixed-post campaign was conducted during weekends and public holidays in July-August 2018 which achieved an administrative vaccination coverage of 71% (ranging from 46% in high-income to 92% in low-income areas). Not including vaccine and vaccination supplies, the average financial cost and economic cost per dose of TCV delivery were $0.45 and $1.42, respectively.

CONCLUSION

The first public sector TCV campaign was successfully implemented by NMMC, with high administrative coverage in slums and low-income areas. Delivery cost estimates provide important inputs to evaluate the cost-effectiveness and affordability of TCV vaccination through public sector preventive campaigns.

Environmental Surveillance as a Tool for Identifying High-risk Settings for Typhoid Transmission

Enteric fever remains a major cause of morbidity in developing countries with poor sanitation conditions that enable fecal contamination of water distribution systems. Historical evidence has shown that contamination of water systems used for household consumption or agriculture are key transmission routes for Salmonella Typhi and Salmonella Paratyphi A. The World Health Organization now recommends that typhoid conjugate vaccines (TCV) be used in settings with high typhoid incidence; consequently, governments face a challenge regarding how to prioritize typhoid against other emerging diseases. A key issue is the lack of typhoid burden data in many low- and middle-income countries where TCV could be deployed. Here we present an argument for utilizing environmental sampling for the surveillance of enteric fever organisms to provide data on community-level typhoid risk. Such an approach could complement traditional blood culture-based surveillance or even replace it in settings where population-based clinical surveillance is not feasible. We review historical studies characterizing the transmission of enteric fever organisms through sewage and water, discuss recent advances in the molecular detection of typhoidal Salmonella in the environment, and outline challenges and knowledge gaps that need to be addressed to establish environmental sampling as a tool for generating actionable data that can inform public health responses to enteric fever.

Methodological Considerations for Cost of Illness Studies of Enteric Fever

This article presents a selection of practical issues, questions, and tradeoffs in methodological choices to consider when conducting a cost of illness (COI) study on enteric fever in low- to lower-middle-income countries. The experiences presented are based on 2 large-scale COI studies embedded within the Surveillance for Enteric Fever in Asia Project II (SEAP II), in Bangladesh, Nepal, and Pakistan; and the Severe Typhoid Fever Surveillance in Africa (SETA) Program in Burkina Faso, Ethiopia, Ghana, and Madagascar. Issues presented include study design choices such as controlling for background patient morbidity and healthcare costs, time points for follow-up, data collection methods for sensitive income and spending information, estimating enteric fever-specific health facility cost information, and analytic approaches in combining patient and health facility costs. The article highlights the potential tradeoffs in time, budget, and precision of results to assist those commissioning, conducting, and interpreting enteric fever COI studies.

Typhoid Conjugate Vaccines and Enteric Fever Control: Where to Next?

After the unprecedented success and acceleration of the global agenda towards typhoid fever control with a strong World Health Organization recommendation and the approval of funding from Gavi, the Vaccine Alliance (Gavi), for the use of a new typhoid conjugate vaccine (TCV), we should turn our minds to the challenges that remain ahead. Despite the evidence showing the safety and clinical efficacy of TCV in endemic populations in developing countries, we should remain vigilant and explore hurdles for the full public health impact of TCV, including vaccine supply for the potential global demand, immunization strategies to optimize the effectiveness and long-term protection provided by the vaccines, potential use of TCV in outbreak settings, and scenarios for addressing chronic carriers. Finally, challenges face endemic countries with poor surveillance systems concerning awareness of the need for TCV and the extent of the issue across their populations, and how to target immunization strategies appropriately.

Enteric fever and COVID-19 co-infection in a teenager returning from Pakistan

As SARS-CoV-2 has become widespread around the globe, co-infection with other endemic infectious diseases will occur. Here we present the first reported case of enteric fever and COVID-19 co-infection, in a teenager returning from travel to Pakistan and describe his clinical course.