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

Objective: This study aims to examine the frequency of Salmonella Paratyphi found in blood cultures and evaluate the antibiotic susceptibility pattern of Salmonella isolates to different antibiotics. Additionally, the study aims to assess the paradigm shift in the trend of enteric fever caused by Salmonella Typhi (S. Typhi) to Salmonella Paratyphi(S. Paratyphi) . Study Design: Retrospective study. Participant: The study enrolled patients aged 12 years and above diagnosed with enteric fever (positive blood culture) and admitted to Peelamedu Samanaidu Govindasamy Naidu (PSG) Hospital. Interventions: The study analyzed demographic and antibiotic susceptibility profiles of Salmonella isolates collected from 106 enteric fever patients in the hospital between 2010 and 2022. The susceptibility profiles of Salmonella isolates to multiple antibiotics were assessed. Results: There were 106 participants, and 95 (89.62%) of them had enteric fever linked to Salmonella Typhi, while only 11 (10.38%) had enteric fever linked to Salmonella Paratyphi A. From 2010 to 2022, the study discovered a general decline in the prevalence of enteric fever caused by Salmonella species. But between 2014 and 2022, the incidence of enteric fever linked to S. Typhi rapidly increased. Azithromycin (100% , n = 106) and ceftriaxone (99% , n = 105) were highly effective against the Salmonella isolates, whereas nalidixic acid was resisted by 3 isolates (4.72%, n = 3). Conclusion: The study observed a higher incidence of Salmonella Typhi in comparison to Paratyphi A and a greater susceptibility of males to enteric fever. Funding: None declared.

Molecular Detection of Salmonella typhi Isolated from Patients Undergoing Gallbladder Cholecystectomy in Baghdad.

BACKGROUND: Salmonella typhi is a specific strain of the Salmonella bacterium, responsible for triggering typhoid fever; a significant public health concern in developing nations. OBJECTIVE: The current study aimed to identify the bacteria from the gallbladder, taken during cholecystectomies of patients, by isolating Salmonella typhi and by using microscopic characteristics, biochemical and polymerase chain reaction (PCR) tests. METHODS: A total of 120 specimens were collected from the Baghdad Teaching Hospital, Iraq. A cross-sectional descriptive study was carried out from October, 2021, to July, 2022. During that study, 26 (54.2%) male patient tested positive for Salmonella typhias well as 22 (45.8%) female patients. The age of the patients varied from < 30 to > 60 years. p-value > 0.05 was considered significant to confirm a relationship between age and Salmonella typhi effect for patients. RESULTS: Out of the 120 blood samples taken for this study, 48 (40%) tested positive by use of PCR test, 40 (33.3%) tested positive by use of the Widal test, 35 (29.1%) were positive for biopsy culture, and 35 (29.1%) were positive for blood culture. All Salmonella typhi isolates were found to be sensitive to the imipenem, cefepime, and ceftriaxone, but were resistant to gentamycin, ciprofloxacin, amikacin, erythromycin, and tetracycline (72%, 29%, 43%, 100%, 100%, respectively). CONCLUSIONS: The real time polymerase chain reaction (RT-PCR) tests and the Vitek 2 compact system showed a high level of accuracy in the detection of Salmonella typhi. Multidrug resistance was observed, which should be a signal to reduce antibiotic consumption.

Extensively Drug-Resistant Salmonella Typhi: A National Disaster.

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The origins of haplotype 58 (H58) Salmonella enterica serovar Typhi.

Antimicrobial resistance (AMR) poses a serious threat to the clinical management of typhoid fever. AMR in Salmonella Typhi (S. Typhi) is commonly associated with the H58 lineage, a lineage that arose comparatively recently before becoming globally disseminated. To better understand when and how H58 emerged and became dominant, we performed detailed phylogenetic analyses on contemporary genome sequences from S. Typhi isolated in the period spanning the emergence. Our dataset, which contains the earliest described H58 S. Typhi organism, indicates that ancestral H58 organisms were already multi-drug resistant (MDR). These organisms emerged spontaneously in India in 1987 and became radially distributed throughout South Asia and then globally in the ensuing years. These early organisms were associated with a single long branch, possessing mutations associated with increased bile tolerance, suggesting that the first H58 organism was generated during chronic carriage. The subsequent use of fluoroquinolones led to several independent mutations in gyrA. The ability of H58 to acquire and maintain AMR genes continues to pose a threat, as extensively drug-resistant (XDR; MDR plus resistance to ciprofloxacin and third generation cephalosporins) variants, have emerged recently in this lineage. Understanding where and how H58 S. Typhi originated and became successful is key to understand how AMR drives successful lineages of bacterial pathogens. Additionally, these data can inform optimal targeting of typhoid conjugate vaccines (TCVs) for reducing the potential for emergence and the impact of new drug-resistant variants. Emphasis should also be placed upon the prospective identification and treatment of chronic carriers to prevent the emergence of new drug resistant variants with the ability to spread efficiently.

The frequency and associated factors of typhoid carriage in patients undergoing cholecystectomy for gallbladder disease in Pakistan: A cross-sectional study.

BACKGROUND: Enteric fever is caused by Salmonella enterica serovars Typhi (S. Typhi) and Paratyphi A, B, and C. It continues to be a significant cause of morbidity and mortality worldwide. In highly endemic areas, children are disproportionately affected, and antimicrobial resistance reduces therapeutic options. It is estimated that 2-5% of enteric fever patients develop chronic asymptomatic infection. These carriers may act as reservoirs of infection; therefore, the prospective identification and treatment of carriers are critical for long-term disease control. We aimed to find the frequency of Salmonella Typhi carriers in patients undergoing cholecystectomy. We also compared the detection limit of culturing versus qPCR in detecting S. Typhi, performed a geospatial analysis of the carriers identified using this study, and evaluated the accuracy of anti-Vi and anti-YncE in identifying chronic typhoid carriage. METHODS: We performed a cross-sectional study in two centers in Pakistan. Gallbladder specimens were subjected to quantitative PCR (qPCR) and serum samples were analyzed for IgG against YncE and Vi by ELISA. We also mapped the residential location of those with a positive qPCR result. FINDINGS: Out of 988 participants, 3.4% had qPCR-positive gallbladder samples (23 S. Typhi and 11 S. Paratyphi). Gallstones were more likely to be qPCR positive than bile and gallbladder tissue. Anti-Vi and YncE were significantly correlated (r = 0.78 p<0.0001) and elevated among carriers as compared to qPCR negative controls, except for anti-Vi response in Paratyphi A. But the discriminatory values of these antigens in identifying carriers from qPCR negative controls were low. CONCLUSION: The high prevalence of typhoid carriers observed in this study suggests that further studies are required to gain information that will help in controlling future typhoid outbreaks in a superior manner than they are currently being managed.

Transcriptional profiling links unique human macrophage phenotypes to the growth of intracellular Salmonella enterica serovar Typhi.

Macrophages provide a crucial environment for Salmonella enterica serovar Typhi (S. Typhi) to multiply during typhoid fever, yet our understanding of how human macrophages and S. Typhi interact remains limited. In this study, we delve into the dynamics of S. Typhi replication within human macrophages and the resulting heterogeneous transcriptomic responses of macrophages during infection. Our study reveals key factors that influence macrophage diversity, uncovering distinct immune and metabolic pathways associated with different stages of S. Typhi intracellular replication in macrophages. Of note, we found that macrophages harboring replicating S. Typhi are skewed towards an M1 pro-inflammatory state, whereas macrophages containing non-replicating S. Typhi exhibit neither a distinct M1 pro-inflammatory nor M2 anti-inflammatory state. Additionally, macrophages with replicating S. Typhi were characterized by the increased expression of genes associated with STAT3 phosphorylation and the activation of the STAT3 transcription factor. Our results shed light on transcriptomic pathways involved in the susceptibility of human macrophages to intracellular S. Typhi replication, thereby providing crucial insight into host phenotypes that restrict and support S. Typhi infection.

An Unusual Hematological Complication of Typhoid Fever Case Report.

Typhoid fever is caused by Salmonella species. The most common hematological complications described are anemia and disseminated intravascular coagulation. Splenic infarction is an unusual complication of typhoid fever, and this presentation is rarely described. We report the case of a young female who presented with complaints of severe left upper quadrant pain after being diagnosed with typhoid fever. Computed tomography (CT) revealed multiple wedge-shaped splenic infarcts. She was treated with antibiotics and was also started on antiplatelets. She had a complete recovery with this management, and antiplatelets were tapered off on subsequent visits.

Primary Aortoenteric Fistula Due to Salmonella typhi-related Mycotic Aneurysm.

Primary aortoenteric fistulas (AEF) are rare. The majority of these are due to atherosclerotic aortic aneurysms. Mycotic aortic aneurysms leading to primary AEF are exceedingly uncommon. Here we report a rare case of primary AEF secondary to Salmonella-related mycotic aneurysm and discuss the diagnostic and therapeutic issues.

Single missense mutations in Vi capsule synthesis genes confer hypervirulence to Salmonella Typhi.

Many bacterial pathogens, including the human exclusive pathogen Salmonella Typhi, express capsular polysaccharides as a crucial virulence factor. Here, through S. Typhi whole genome sequence analyses and functional studies, we found a list of single point mutations that make S. Typhi hypervirulent. We discovered a single point mutation in the Vi biosynthesis enzymes that control Vi polymerization or acetylation is enough to result in different capsule variants of S. Typhi. All variant strains are pathogenic, but the hyper Vi capsule variants are particularly hypervirulent, as demonstrated by the high morbidity and mortality rates observed in infected mice. The hypo Vi capsule variants have primarily been identified in Africa, whereas the hyper Vi capsule variants are distributed worldwide. Collectively, these studies increase awareness about the existence of different capsule variants of S. Typhi, establish a solid foundation for numerous future studies on S. Typhi capsule variants, and offer valuable insights into strategies to combat capsulated bacteria.

Spatial and temporal clustering of typhoid fever in an urban slum of Dhaka City: Implications for targeted typhoid vaccination.

BACKGROUND: Salmonella enterica serotype Typhi (Salmonella Typhi) causes severe and occasionally life-threatening disease, transmitted through contaminated food and water. Humans are the only reservoir, inadequate water, sanitation, and hygiene infrastructure increases risk of typhoid. High-quality data to assess spatial and temporal relationships in disease dynamics are scarce. METHODS: We analyzed data from a prospective cohort conducted in an urban slum area of Dhaka City, Bangladesh. Passive surveillance at study centers identified typhoid cases by microbiological culture. Each incident case (index case) was matched to two randomly selected index controls, and we measured typhoid incidence in the population residing in a geographically defined region surrounding each case and control. Spatial clustering was evaluated by comparing the typhoid incidence in residents of geometric rings of increasing radii surrounding the index cases and controls over 28 days. Temporal clustering was evaluated by separately measuring incidence in the first and second 14-day periods following selection. Incidence rate ratios (IRRs) were calculated using Poisson regression models. RESULTS: We evaluated 141 typhoid index cases. The overall typhoid incidence was 0.44 per 100,000 person-days (PDs) (95% CI: 0.40, 0.49). In the 28 days following selection, the highest typhoid incidence (1.2 per 100,000 PDs [95% CI: 0.8, 1.6]) was in the innermost cluster surrounding index cases. The IRR in this innermost cluster was 4.9 (95% CI: 2.4, 10.3) relative to the innermost control clusters. Neither typhoid incidence rates nor relative IRR between index case and control populations showed substantive differences in the first and second 14-day periods after selection. CONCLUSION: In the absence of routine immunization programs, geographic clustering of typhoid cases suggests a higher intensity of typhoid risk in the population immediately surrounding identified cases. Further studies are needed to understand spatial and temporal trends and to evaluate the effectiveness of targeted vaccination in disrupting typhoid transmission.

The cost of typhoid illness in low- and middle-income countries, a scoping review of the literature.

Typhoid fever is responsible for a substantial health burden in low- and middle-income countries (LMICs). New means of prevention became available with the prequalification of typhoid conjugate vaccines (TCV) by the World Health Organization (WHO) in 2018. Policymakers require evidence to inform decisions about TCV. The economic burden related to typhoid fever can be considerable, both for healthcare providers and households, and should be accounted for in the decision-making process. We aimed to understand the breadth of the evidence on the cost of typhoid fever by undertaking a scoping review of the published literature. We searched scientific databases with terms referring to typhoid fever cost of illness to identify published studies for the period January 1st 2000 to May 24th 2024. We also conferred with stakeholders engaged in typhoid research to identify studies pending completion or publication. We identified 13 published studies reporting empirical data for 11 countries, most of them located in Asia. The total cost of a typhoid episode ranged from $23 in India to $884 in Indonesia (current 2022 United States Dollar [USD]). Household expenditures related to typhoid fever were characterized as catastrophic in 9 studies. We identified 5 studies pending completion or publication, which will provide evidence for 9 countries, most of them located in Africa. Alignment in study characteristics and methods would increase the usefulness of the evidence generated and facilitate cross-country and regional comparison. The gap in evidence across regions should be mitigated when studies undertaken in African countries are published. There remains a lack of evidence on the cost to treat typhoid in the context of increasing antimicrobial resistance. Decision-makers should consider the available evidence on the economic burden of typhoid, particularly as risk factors related to antimicrobial resistance and climate change increase typhoid risk. Additional studies should address typhoid illness costs, using standardized methods and accounting for the costs of antimicrobial resistance.

Enteric Fever in Children: An Epidemiological and Clinical Review of Cases in Southeast Texas.

Extensively drug-resistant (XDR) strains of Salmonella enterica serotype Typhi have emerged in Pakistan and Iraq. We report 13 children with enteric fever in Southeast Texas seen over 3.5 years, of whom 23.1% had XDR isolates.

Ultrasensitive detection of Salmonella typhi using a PAM-free Cas14a-based biosensor.

The effectiveness of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas14a1, widely utilized for pathogenic microorganism detection, has been limited by the requirement of a protospacer adjacent motif (PAM) on the target DNA strands. To overcome this limitation, this study developed a Single Primer isothermal amplification integrated-Cas14a1 biosensor (SPCas) for detecting Salmonella typhi that does not rely on a PAM sequence. The SPCas biosensor utilizes a novel primer design featuring an RNA-DNA primer and a 3'-biotin-modified primer capable of binding to the same single-stranded DNA (ssDNA) in the presence of the target gene. The RNA-DNA primer undergoes amplification and is blocked at the biotin-modified end. Subsequently, strand replacement is initiated to generate ssDNA assisted by RNase H and Bst enzymes, which activate the trans-cleavage activity of Cas14a1 even in the absence of a PAM sequence. Leveraging both cyclic chain replacement reaction amplification and Cas14a1 trans-cleavage activity, the SPCas biosensor exhibits a remarkable diagnostic sensitivity of 5 CFU/mL. Additionally, in the assessment of 20 milk samples, the SPCas platform demonstrated 100% diagnostic accuracy, which is consistent with the gold standard qPCR. This platform introduces a novel approach for developing innovative CRISPR-Cas-dependent biosensors without a PAM sequence.

Uncovering the growing burden of enteric fever: A molecular analysis of Salmonella Typhi antimicrobial resistance.

Enteric fever, a persistent public health challenge in developing regions, is exacerbated by suboptimal socioeconomic conditions, contaminated water and food sources, and insufficient sanitation. This study delves into the antimicrobial susceptibility of Salmonella Typhi, uncovering the genetic underpinnings of its resistance. Analyzing 897 suspected cases, we identified a significant prevalence of typhoid fever, predominantly in males (58.3 %) and younger demographics. Alarmingly, our data reveals an escalation in resistance to both primary and secondary antibiotics, with cases of multi-drug resistant (MDR) and extensively drug-resistant (XDR) S. Typhi reaching 14.7 % and 43.4 %, respectively, in 2021. The Multiple Antibiotic Resistance (MAR) index exceeded 0.2 in over half of the isolates, signaling widespread antibiotic misuse. The study discerned 47 unique antibiotic resistance patterns and pinpointed carbapenem and macrolide antibiotics as the remaining effective treatments against XDR strains, underlining the critical need to preserve these drugs for severe cases. Molecular examinations identified blaTEM, blaSHV, and blaCTX-M genes in ceftriaxone-resistant strains, while qnrS was specific to ciprofloxacin-resistant variants. Notably, all examined strains exhibited a singular mutation in the gyrA gene, maintaining wild-type gyrB and parC genes. The erm(B) gene emerged as the primary determinant of azithromycin resistance. Furthermore, a distressing increase in resistance genes was observed over three years, with erm(B), blaTEM and qnrS showing significant upward trends. These findings are a clarion call for robust antimicrobial stewardship programs to curtail inappropriate antibiotic use and forestall the burgeoning threat of antibiotic resistance in S. Typhi.

Development, confirmation, and application of a seeded Escherichia coli process control organism to validate Salmonella enterica serovar Typhi environmental surveillance methods.

Salmonella enterica serovar Typhi (S. Typhi) is the causative agent of Typhoid fever. Blood culture is the gold standard for clinical diagnosis, but this is often difficult to employ in resource limited settings. Environmental surveillance of waste-impacted waters is a promising supplement to clinical surveillance, however validating methods is challenging in regions where S. Typhi concentrations are low. To evaluate existing S. Typhi environmental surveillance methods, a novel process control organism (PCO) was created as a biosafe surrogate. Using a previous described qPCR assay, a modified PCR amplicon for the staG gene was cloned into E. coli. We developed a target region that was recognized by the Typhoid primers in addition to a non-coding internal probe sequence. A multiplex qPCR reaction was developed that differentiates between the typhoid and control targets, with no cross-reactivity or inhibition of the two probes. The PCO was shown to mimic S. Typhi in lab-based experiments with concentration methods using primary wastewater: filter cartridge, recirculating Moore swabs, membrane filtration, and differential centrifugation. Across all methods, the PCO seeded at 10 CFU/mL and 100 CFU/mL was detected in 100% of replicates. The PCO is detected at similar quantification cycle (Cq) values across all methods at 10 CFU/mL (Average = 32.4, STDEV = 1.62). The PCO was also seeded into wastewater at collection sites in Vellore (India) and Blantyre (Malawi) where S. Typhi is endemic. All methods tested in both countries were positive for the seeded PCO. The PCO is an effective way to validate performance of environmental surveillance methods targeting S. Typhi in surface water.

Trends in typhoid fever during the COVID-19 pandemic in Pakistan.

INTRODUCTION: Pakistan has been experiencing an extensively drug-resistant (XDR) outbreak of typhoid for some years. We sought to evaluate how the COVID-19 pandemic impacted typhoid epidemiology in Pakistan, from the beginning of the pandemic in 2020 through the end of 2022, and the reduction of COVID-19 cases. METHODOLOGY: We compared national public COVID-19 data with retrospectively obtained patient data of confirmed S. Typhi isolates between January 2019 and December 2022 from Shaukat Khanum Memorial Cancer Hospital and Research Centre and the hospital's extended network of laboratory collection centers across Pakistan. RESULTS: We observed that during the early onset of the COVID-19 pandemic and COVID-19 peaks, typhoid positivity generally decreased. This suggests that restrictions and non-pharmaceutical interventions that limited social interactions and promoted good sanitation and hygiene practices had a positive secondary effect on typhoid. This led to an overall yearly decrease in typhoid positivity between 2019 to 2021. However, the percentage of S. Typhi cases isolated that were ceftriaxone-resistant continued to increase, suggesting the continued dominance of XDR typhoid in Pakistan. In 2022, with the alleviation of pandemic restrictions, we observed increased typhoid positivity and COVID-19 and typhoid positivity started to follow similar trends. CONCLUSIONS: Given the continued presence of COVID-19 along with XDR typhoid in Pakistan, it will be imperative to use differential testing to ensure that the epidemiology of each reported is accurate, the spread of each it contained, and that antibiotics are not misused. The use of approved vaccinations will lessen the burden of both diseases.

A TLR4 ligand-based adjuvant for promoting the immunogenicity of typhoid subunit vaccines.

None of the typhoid Vi Polysaccharide (ViPS) subunit vaccines incorporate adjuvants, and the immunogenicity of ViPS vaccines (e.g. Typbar TCV® and Typhim Vi®) is in part due to associated TLR4 ligands such as endotoxin present in these vaccines. Since endotoxin content in vaccines is variable and kept very low due to inherent toxicity, it was hypothesized that incorporating a defined amount of a non-toxic TLR4-ligand such as monophosphoryl lipid A in ViPS vaccines would improve their immunogenicity. To test this hypothesis, a monophosphoryl lipid A-based adjuvant formulation named Turbo was developed. Admixing Turbo with Typbar TCV® (ViPS-conjugated to tetanus toxoid) increased the levels of anti-ViPS IgM, IgG1, IgG2b, IgG2a/c, and IgG3 in inbred and outbred mice. In infant mice, a single immunization with Turbo adjuvanted Typbar TCV® resulted in a significantly increased and durable IgG response and improved the control of bacterial burden compared to mice immunized without Turbo. Similarly, when adjuvanted with Turbo, the antibody response and control of bacteremia were also improved in mice immunized with Typhim Vi®, an unconjugated vaccine. The immunogenicity of unconjugated ViPS is inefficient in young mice and is lost in adult mice when immunostimulatory ligands in ViPS are removed. Nevertheless, when adjuvanted with Turbo, poorly immunogenic ViPS induced a robust IgG response in young and adult mice, and this was observed even under antigen-limiting conditions. These data suggest that incorporation of Turbo as an adjuvant will make typhoid vaccines more immunogenic regardless of their intrinsic immunogenicity or conjugation status and maximize the efficacy across all ages.

The Salmonella typhi Cell Division Activator Protein StCAP Impacts Pathogenesis by Influencing Critical Molecular Events.

Conserved molecular signatures in multidrug-resistant Salmonella typhi can serve as novel therapeutic targets for mitigation of infection. In this regard, we present the S. typhi cell division activator protein (StCAP) as a conserved target across S. typhi variants. From in silico and fluorimetric assessments, we found that StCAP is a DNA-binding protein. Replacement of the identified DNA-interacting residue Arg34 of StCAP with Ala34 showed a dramatic (15-fold) increase in Kd value compared to the wild type (Kd 546 nm) as well as a decrease in thermal stability (10 °C shift). Out of the two screened molecules against the DNA-binding pocket of StCAP, eltrombopag, and nilotinib, the former displayed better binding. Eltrombopag inhibited the stand-alone S. typhi culture with an IC50 of 38 µM. The effect was much more pronounced on THP-1-derived macrophages (T1Mac) infected with S. typhi where colony formation was severely hindered with IC50 reduced further to 10 µM. Apoptotic protease activating factor1 (Apaf1), a key molecule for intrinsic apoptosis, was identified as an StCAP-interacting partner by pull-down assay against T1Mac. Further, StCAP-transfected T1Mac showed a significant increase in LC3 II (autophagy marker) expression and downregulation of caspase 3 protein. From these experiments, we conclude that StCAP provides a crucial survival advantage to S. typhi during infection, thereby making it a potent alternative therapeutic target.

Enteric Fever-Associated Hemophagocytic Lymphohistiocytosis: A Systematic Review of Clinical Characteristics and Outcomes.

Enteric fever is a major contributor to rising health care costs in developing countries. Associated disease-related complications and drug resistance further compound this problem. Hemophagocytic lymphohistiocytosis (HLH) is an uncommon complication of enteric fever with high morbidity and mortality. This systematic review aimed to evaluate the clinical characteristics and treatment outcomes in enteric fever-associated HLH syndrome. We searched major electronic databases (PubMed, Google Scholar, and Scopus) to identify the cases of enteric fever associated with HLH from inception until June 2023. Prespecified data regarding clinical presentation, outcomes, and HLH therapy were collected. A total of 53 cases of enteric fever with HLH were included in the final analysis. The mean age of patients was 20 years, and the proportions of female and pediatric patients were 52.8% and 45.3%, respectively. The mean duration of illness was 10.4 days. A total of 39.6% of patients had enteric fever-associated complications; coagulopathy and encephalopathy were the most common (23.1% and 13.5%). The overall mortality rate was 9.4% in HLH. A total of 51% of patients received HLH-specific therapy (corticosteroids in 41.5% and intravenous immunoglobulin in 20.8% of patients). On multivariate analysis, high ferritin levels (≥5,000 ng/mL) were significantly associated with mortality (hazard ratio, 3.01; 95% CI = 0.62-14.12, P = 0.041). Enteric fever with secondary HLH is associated with high mortality. This review reveals the potential role of ferritin in disease prognosis. In cases with significantly elevated ferritin levels, the role of immunosuppressants or combination antibiotics should be explored.