Typhoid Fever Diagnosis in Endemic Countries: A Clog in the Wheel of Progress?

Environmental surveillance for Salmonella Typhi to detect the typhoid burden in Yogyakarta, Indonesia

BACKGROUND

In low and middle-income countries (LMICs), understanding the burden of typhoid disease has been challenging as clinical surveillance based on blood culture data alone often poorly represents the community burden. Underreported cases, unclear case definitions, the presence of a chronic carrier state and emerging antimicrobial resistance necessitate alternative approaches to assess disease prevalence and target public health interventions, such as vaccine introduction. This study aimed to assess the feasibility of wastewater and environmental surveillance (WES) in measuring the prevalence of typhoid infection in Indonesia.

METHODS

Between October 11, 2022, and August 31, 2023, WES was conducted in 18 locations across 3 districts in Yogyakarta province, Indonesia. Samples were collected fortnightly from wastewater treatment plants (WWTPs), manholes, a river, and public spaces, using grab and passive sampling methods. Salmonella Typhi (S. Typhi) detection was conducted using quantitative PCR for S. Typhi genes (ttr, tviB, and staG - all positive).

RESULTS

Of the 406 samples collected, 13 % (51/406) tested positive for S. Typhi, with monthly positivity rates ranging from 2 % (1/51) in March 2023 to 47 % (16/34) in October 2022. Mean concentrations (in log10) in ttr, tviB, and staG in grab samples were 0.67 (SD ± 0.99), 0.23 (SD ± 1.14), and -0.11 (SD ± 1.05). The highest detection rates were observed in samples from the river compared to central WWTPs (OR 12.68; 95 % CI 2.03-79.20, P = 0.007). No correlation was observed between rainfall and S. Typhi gene detection (P > 0.05 for all genes).

CONCLUSION

WES is feasible in Indonesia and can be used to monitor typhoid disease burden in an endemic region. High positivity rates from the river and septic tanks in traditional markets support a broad approach to sampling in LMICs where formal wastewater management systems may not accurately represent community disease prevalence due to its low population coverage. WES can be a valuable tool to inform public health responses, including vaccine introduction.

Enhancing Typhoid Fever Diagnosis Based on Clinical Data Using a Lightweight Machine Learning Metamodel

Background: Typhoid fever remains a significant public health challenge, especially in developing countries where diagnostic resources are limited. Accurate and timely diagnosis is crucial for effective treatment and disease containment. Traditional diagnostic methods, while effective, can be time-consuming and resource-intensive. This study aims to develop a lightweight machine learning-based diagnostic tool for the early and efficient detection of typhoid fever using clinical data. Methods: A custom dataset comprising 14 clinical and demographic parameters-including age, gender, headache, muscle pain, nausea, diarrhea, cough, fever range (°F), hemoglobin (g/dL), platelet count, urine culture bacteria, calcium (mg/dL), and potassium (mg/dL)-was analyzed. A machine learning metamodel, integrating Support Vector Machine (SVM), Gaussian Naive Bayes (GNB), and Decision Tree classifiers with a Light Gradient Boosting Machine (LGBM), was trained and evaluated using k-fold cross-validation. Performance was assessed using precision, recall, F1-score, and area under the receiver operating characteristic curve (AUC). Results: The proposed metamodel demonstrated superior diagnostic performance, achieving a precision of 99%, recall of 100%, and an AUC of 1.00. It outperformed traditional diagnostic methods and other standalone machine learning algorithms, offering high accuracy and generalizability. Conclusions: The lightweight machine learning metamodel provides a cost-effective, non-invasive, and rapid diagnostic alternative for typhoid fever, particularly suited for resource-limited settings. Its reliance on accessible clinical parameters ensures practical applicability and scalability, potentially improving patient outcomes and aiding in disease control. Future work will focus on broader validation and integration into clinical workflows to further enhance its utility.

Evaluating alternatives to the Widal test for typhoid fever diagnosis in developing countries: A targeted literature review

Background

Typhoid disease, caused by Salmonella typhi, is prevalent in developing countries with poor sanitation. The Widal test, despite its century-old history, has drawbacks in diagnostic capacity because of inherent characteristics, cross-reactivity and repeated exposure to the pathogen in endemic regions.

Aim

The study evaluates the utility of the Widal test for the diagnosis of typhoid infections and emphasises the need for a better diagnostic modality in endemic regions.

Setting

The study included research conducted in developing countries where typhoid fever is endemic.

Method

A targeted literature review was conducted utilising the MEDLINE and Embase databases on 19 October 2022, encompassing publications from the preceding 10 years. Manual searches were executed using Google Scholar and the Google Search Engine on 02 November 2022. The initial search yielded 657 articles, of which 20 met the inclusion criteria and were subsequently incorporated into the final review.

Results

The mean sensitivity, specificity, positive predictive value and negative predictive value of the Widal test in this study were 62.94 ± 17.83 (95% confidence interval [CI]: 49.23-76.64); 73.31 ± 18.75 (95% CI: 58.89-87.73); 58.85 ± 40.07 (95% CI: 16.80-100.90) and 75.96 ± 25.93 (95% CI: 46.08-100.45), respectively.

Conclusion

The different studies in this review have shown that the Widal test performs poorly in identifying typhoid infections compared to other rapid diagnostic tests (RDTs). In addition, the current alternative RDTs are not accurate enough to reliably identify or rule out typhoid infection.

Contributions

A shift in diagnostic approach for typhoid fever in developing countries is required and an accurate and feasible point-of-care test is urgently needed.

Seroprevalence of Typhoid Fever and Its Associated Risk Factors Among Clinically Diagnosed Febrile Patients Visiting the Outpatient Department at Debark Hospital and Drug Susceptibility Patterns of Isolates

Typhoid fever is caused by the bacterium Salmonella Typhi, which poses major health problems in developing countries, including Ethiopia. However, there is limited information regarding typhoid fever, contributing factors with it, and its drug susceptibility pattern in the research area. The aim of this study was to determine the seroprevalence of typhoid fever and its associated risk factors among clinically diagnosed febrile patients at Debark Hospital and evaluate the drug susceptibility patterns of the isolates. A hospital-based cross-sectional study was conducted among 158 febrile patients from December 2022 to April 2023. Blood and stool samples were collected from each febrile patient. The Widal test was used to test Salmonella Typhi O and H antigens sera from blood, and bacteria were cultured from the stool. Gram staining and biochemical analyses were carried out for each isolate. Antibiotic susceptibility testing was performed for the isolates using Kirby-Bauer disk diffusion techniques. Descriptive statistics and logistic regression were used for analysis. In this study, the seroprevalence of typhoid fever among febrile patients at Debark Hospital was 22.8%. Gender (adjusted odds ratio (AOR): 95% confidence interval (CI): 0.02, 0.31, p ≤ 0.001), marital status (AOR: 95% CI: 2.63, 4.66, p ≤ 0.001), family size (AOR: 95% CI: 0.01, 0.31, p ≤ 0.001), residence (AOR: 95% CI: 0.09, 0.83, p = 0.021), practice of using toilet (AOR: 95% CI: 0.08, 0.086, p = 0.027), washing fruits and vegetables before eating (AOR: 95% CI: 0.12, 0.87, p = 0.025), and awareness of typhoid fever transmission and prevention (AOR: 95% CI: 0.12, 0.91, p = 0.032) are the associated risk factors for typhoid fever. Fifty percent of the isolates showed multidrug resistance to two or more antibiotics. It was suggested that improving personal hygiene, providing safe drinking water, and careful use of antibiotics could considerably reduce the prevalence of typhoid fever in the study area.

Diagnostic performance of Typhidot RDT in diagnosis of typhoid fever and antibiotic resistance characterisation in a cross-sectional study in Southern Ghana

BACKGROUND

Typhoid fever remains a significant public health problem contributing to significant misapplication of antibiotics in Ghana. However, there is little data on the accuracy of the commonly used serology based rapid diagnostic Typhidot test kit (Typhidot RDT) for confirming typhoid fever.

METHODS

We conducted a study to assess the diagnostic accuracy of Typhidot RDT in seven clinical facilities across five regions in Southern Ghana. A total of 258 participants, clinically diagnosed with typhoid fever, were enrolled in this study. Blood and stool samples were obtained for culture, Typhidot and PCR assays. Disc diffusion antibiotic sensitivity was performed to determine the resistance pattern of Salmonella enterica isolates from positive blood and stool cultures.

RESULTS

Recovery of S. enterica isolates was higher from stool samples (14.7%) in comparison to blood samples (1.6%). The sensitivity and specificity of Typhidot compared to blood and stool cultures was 35% (19.94%-52.65%) and 45% (38.67%-51.45%), respectively. Compared to PCR, the Typhidot had a sensitivity and a specificity of 61% and 53%, respectively. Resistance phenotyping of isolates showed broad sensitivity to the front-line antibiotics used. Resistance to ampicillin (10%), cotrimoxazole (7%), azithromycin and ciprofloxacin (< 5%) was found in some isolates.

CONCLUSIONS

These findings suggest sub-optimal performance of the Typhidot RDT for diagnosis of typhoid in Ghana with a higher chance for misdiagnosis and misapplication of antibiotics. The high proportion of isolates recovered from stool culture is consistent with the pathophysiology of bacterial shedding during the acute phase of infection, which provides a window of opportunity to control typhoid transmission.

Prevalence of Salmonella Typhi, its associated factors and antimicrobial susceptibility profile among patients attending Hawassa University Comprehensive Specialized Hospital, Hawassa, Ethiopia

INTRODUCTION

Salmonella Typhi infections cause significant morbidity and mortality worldwide, especially in developing countries including Ethiopia. This study aimed to determine the prevalence of Salmonella Typhi, its associated factors and antibiotic susceptibility profile among suspected typhoid patients.

METHODS

A cross-sectional study was conducted on 270 typhoid fever suspected patients at Hawassa University Comprehensive Specialized Hospital from June 2022 to September 2022. Data were collected using questionnaires by face-to-face interview. Stool samples for microbiological culture, blood samples for S. Typhi IgM/Entero-check WB rapid test and isolates for antimicrobial susceptibility tests were used through standard procedures and according to the reagents manufactures' instructions. Hygiene implementation of patients was also assessed using interview. Sociodemographic and clinical characteristics of the patient's were considered. Descriptive statistics were used to summarize the data, and logistic regression model analysis was performed to assess associations between S. Typhi infection and the associated sociodemographic and clinical factors.

RESULTS

The prevalence of S. Typhi IgM/Entero-check WB rapid test and stool culture results were 3.3%; (95% CI: 1.5-5.6) and 3.7%; (95% CI: 1.9-6.3) respectively. Not washing hands after latrine [AOR = 0.85, 95% CI (0.15-4.79), p = 0.05] is not significant but, not washing hands before meal [AOR = 0.053, 95% CI (0.08-0.36), p = 0.03], eating raw vegetables [AOR = 0.024, 95% CI (0.001-0.48), p = 0.015] and drinking water from a stream [AOR = 0.12, 95% CI (0.19-0.70), p = 0.001] were significantly associated with S. Typhi infection, but in terms of AOR, all are preventive. Susceptibility of isolates was 9/10 (90%), 8/10 (80%), and 8/10 (80%) to ciprofloxacin, ceftriaxone, and chloramphenicol, respectively. The majorities 100% and 80% of the isolates were resistant to ampicillin and cotrimoxazole, respectively. About 40% of the isolates were MDR.

CONCLUSION

The prevalence of Salmonella Typhi with MDR has been observed. Therefore, health programmers and stakeholders should make efforts to improve the habit of sanitation, strengthen the capacity of laboratory diagnostic methods and increase awareness of the misprescription and misuse of antibiotics to reduce the impact of MDR bacteria.

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.

β-lactam-induced OMV release promotes polymyxin tolerance in Salmonella enterica sv. Typhi

The rise of multidrug-resistant bacteria is a global concern, leading to a renewed reliance on older antibiotics like polymyxins as a last resort. Polymyxins, cationic cyclic peptides synthesized nonribosomally, feature a hydrophobic acyl tail and positively charged residues. Their antimicrobial mechanism involves initial interaction with Gram-negative bacterial outer-membrane components through polar and hydrophobic interactions. Outer membrane vesicles (OMVs), nano-sized proteoliposomes secreted from the outer membrane of Gram-negative bacteria, play a crucial role in tolerating harmful molecules, including cationic peptides such as polymyxins. Existing literature has documented environmental changes' impact on modulating OMV properties in Salmonella Typhimurium. However, less information exists regarding OMV production and characteristics in Salmonella Typhi. A previous study in our laboratory showed that S. Typhi ΔmrcB, a mutant associated with penicillin-binding protein (PBP, a β-lactam antibiotic target), exhibited hypervesiculation. Consequently, this study investigated the potential impact of β-lactam antibiotics on promoting polymyxin tolerance via OMVs in S. Typhi. Our results demonstrated that sub-lethal doses of β-lactams increased bacterial survival against polymyxin B in S. Typhi. This phenomenon stems from β-lactam antibiotics inducing hypervesiculation of OMVs with higher affinity for polymyxin B, capturing and diminishing its biologically effective concentration. These findings suggest that β-lactam antibiotic use may inadvertently contribute to decreased polymyxin effectivity against S. Typhi or other Gram-negative bacteria, complicating the effective treatment of infections caused by these pathogens. This study emphasizes the importance of evaluating the influence of β-lactam antibiotics on the interaction between OMVs and other antimicrobial agents.

Epidemiology and Performances of Typhidot Immunoassay and Widal Slide Agglutination in the Diagnosis of Typhoid Fever in Febrile Patients in Bafoussam City, Cameroon: A Cross-Sectional Comparative Study

Background

Enteric fever is a great public health problem associated with significant illness and death in many endemic countries, and its clinical diagnosis is still daunting. The aim of this study was to determine the prevalence and risk factors of S. Typhi among febrile patients in Bafoussam and to evaluate the diagnostic performances of Widal and Typhidot tests.

Methods

This was a cross-sectional study among 336 participants visiting three hospitals in Bafoussam from August 1, 2021, to November 31, 2021. Widal test, Typhidot assay, and stool culture were used to screen for salmonellosis with the help of a structured questionnaire.

Results

The prevalence of S. Typhi and S. Paratyphi was found to be 62.85% and 37.14%, respectively. The overall prevalence of typhoid fever using stool culture was 20.86%. The significant risk factors associated with enteric fever were lack or insufficient knowledge of typhoid fever, poor hand hygiene, and anorexia. Typhidot immunoassay was more sensitive (100%) and specific (82.3%) than the Widal test. Both were analytically inferior to stool culture.

Conclusions

High prevalence of typhoid fever (20.86%) was observed which was largely associated with lack or insufficient knowledge of typhoid fever, poor hygiene measure, and anorexia as risk factors. The performances of the Widal and Typhidot test against a stool culture were inferior but with Typhidot better than the Widal slide agglutination.

Computational study of the piperidine and FtsZ interaction in Salmonella Typhi: implications for disrupting cell division machinery

FtsZ, a bacterial cell division protein, is essential for assembling the contractile Z-ring crucial in bacterial cytokinesis. Consequently, inhibiting FtsZ could impede proto-filaments, disrupting FtsZ and other associated proteins vital for cell division machinery. Conduct an in-silico drug interaction study to identify novel drug candidates that inhibit the FtsZ protein, aiming to prevent Multi-Drug Resistant (MDR) Salmonella Typhi. Data mining was performed based on piperidine compounds, which were subsequently screened for safe pharmacokinetic profiles. Compounds that met favorable drug-likeness criteria underwent virtual screening against the FtsZ drug target. Two compounds were chosen for molecular docking and molecular dynamic simulation to verify the binding affinity and stability between the target protein and the potential compounds. The 400 isoforms of piperidine analogues were curated, among them potent compound ZINC000000005416 found to possess high binding affinity (-8.49 kcal/mol) and low dissociation constant (0.597 µM). The highest binding affinity shown by ZINC000000005416 was validated by hydrogen bonds, hydrophobic interaction, and salt bridges with the functional domain of the cell division regulatory protein. Docking profiles, when correlated with molecular dynamic simulation (MDS) depicted stable trajectories and compatible conformational changes in the FtsZ-ZINC000000005416 complex. The stable simulated trajectories were validated through free-energy calculations using the Molecular Mechanics-Poisson Boltzmann Surface Area (MM/PBSA) module. Low energy conformations, although the simulation trajectory confirmed the stable ZINC000000005416-FtsZ interaction, which encouraged experimental validations. This study encourages further exploration of the compound ZINC000000005416 as a drug candidate inhibiting FtsZ protein against MDR Salmonella Typhi.

Variations of blood viscosity in acute typhoid fever: A cross-sectional study

Typhoid fever (TF) is a systemic infection caused by Salmonella Typhi (Salmonella Enterica) transmitted through contaminated water, food, or contact with infected individuals. In various infectious diseases, blood viscosity (BV) is affected by changes in hemoglobin concentrations and acute phase reactants. Inflammatory responses can lead to elevated plasma protein levels and further affect BV. This study aimed to investigate BV changes in patients with acute TF. A cross-sectional study was performed involving 55 patients with acute TF compared to 38 healthy controls. BV and inflammatory parameters were measured in both groups. TF patients showed reduced blood cells compared to healthy controls (p=0.001). Additionally, plasma total protein (TP) levels significantly increased to 10.79±1.05 g/L in TF patients compared to 7.035±1.44 g/L in healthy controls (p=0.03). Hematocrit (HCT) levels were 11.67±2.89% in TF patients and 12.84±2.02% in healthy controls (p=0.07), suggesting a trend towards increased BV in TF patients. Elevated BV is involved in the pathogenesis of different inflammatory and infectious diseases. The increased BV in TF patients may raise the risk of complications. Therefore, monitoring BV might be a crucial tool in TF patients, mainly in the high-risk group, for early detection of cardiovascular complications.

Surface plasmon resonance-based oligonucleotide biosensor for Salmonella Typhi detection

Due to high mortality rates, typhoid fever still is one of the major health problems in the world, particularly in developing countries. The lack of highly specific and sensitive diagnostic tests and the great resemblance of typhoid fever symptoms to other diseases made the false-negative diagnosis a major challenge in typhoid fever management. Hence, we decided to design a Surface Plasmon Resonance (SPR) based biosensor for specific detection of Salmonella typhi through DNA hybridization. The results showed that the 10 nM of the synthetic target sequence, as well as 1 nM of PCR product, were the lowest feasible detected concentrations by the designed biosensor. This genosensor was also found to significantly distinguish the complementary sequence with the accuracy of one base mismatch sequence. The surface of the chip can be regenerated with NaOH solution and used for consecutive diagnosis. Therefore, the function of the designed biosensor indicates its high potential for Salmonella typhi detection practice.

Diagnostics for Typhoid Fever: Current Perspectives and Future Outlooks for Product Development and Access

Typhoid is an enteric disease caused by Salmonella Typhi. Like many febrile illnesses, typhoid presents with nonspecific symptoms. In routine healthcare settings in low- and middle-income countries, typhoid fever is suspected and treated empirically. Though many diagnostic tests are available for typhoid diagnosis, there are currently no diagnostic tests that meet ideal requirements for sensitivity, specificity, speed, and cost-effectiveness. With introduction of typhoid conjugate vaccine, it is essential to explore the current and future typhoid approach in the context of use case and access to ensure their utilization for disease control.

Safety and immunogenicity of a typhoid conjugate vaccine among children aged 9 months to 12 years in Malawi: a nested substudy of a double-blind, randomised controlled trial

BACKGROUND

Typhoid fever is a substantial public health problem in Africa, yet there are few clinical trials of typhoid conjugate vaccine (TCV). We assessed immunogenicity and safety of Typbar TCV in Malawi.

METHODS

This substudy was nested within a phase 3, double-blind, parallel design, randomised controlled trial of TCV in children from Ndirande Health Centre in Ndirande township, Blantyre, Malawi. To be eligible, participants had to be aged between 9 months and 12 years with no known immunosuppression or chronic health conditions, including HIV or severe malnutrition; eligible participants were enrolled into three strata of approximately 200 children (9-11 months, 1-5 years, and 6-12 years), randomly assigned (1:1) to receive TCV or control (meningococcal serogroup A conjugate vaccine [MCV-A]) intramuscularly. Serum was collected before vaccination and at 28 days and 730-1035 days after vaccination to measure anti-Vi antibodies by ELISA. Because of COVID-19, day 730 visits were extended up to 1035 days. This nested substudy evaluated reactogenicity, safety, and immunogenicity by age stratum. Safety outcomes, analysed in the intention-to-treat population, included solicited adverse events within 7 days of vaccination (assessed on 3 separate days) and unsolicited adverse events within 28 days of vaccination. This trial is registered with ClinicalTrials.gov, NCT03299426.

FINDINGS

Between Feb 22 and Sept 6, 2018, 664 participants were screened, and 631 participants were enrolled and randomly assigned (320 to the TCV group and 311 to the MCV-A group). 305 participants in the TCV group and 297 participants in the MCV-A group were vaccinated. Among TCV recipients, anti-Vi IgG geometric mean titres increased more than 500 times from 4·2 ELISA units (EU)/mL (95% CI 4·0-4·4) at baseline to 2383·7 EU/mL (2087·2-2722·3) at day 28, then decreased to 48·0 EU/mL (39·9-57·8) at day 730-1035, remaining more than 11 times higher than baseline. Among MCV-A recipients, anti-Vi IgG titres remained unchanged: 4·3 EU/mL (4·0-4·5) at baseline, 4·4 EU/mL (4·0-4·7) on day 28, and 4·6 EU/mL (4·2-5·0) on day 730-1035. TCV and MCV-A recipients had similar solicited local (eight [3%] of 304, 95% CI 1·3-5·1 and three [1%] of 293, 0·4-3·0) and systemic (27 [9%] of 304, 6·2-12·6 and 27 [9%] of 293, 6·4-13·1) reactogenicity. Related unsolicited adverse events occurred similarly in TCV and MCV-A recipients in eight (3%) of 304 (1·3-5·1) and eight (3%) of 293 (1·4-5·3).

INTERPRETATION

This study provides evidence of TCV safety, tolerability, and immunogenicity up to 730-1035 days in Malawian children aged 9 months to 12 years.

FUNDING

Bill & Melinda Gates Foundation.

Prevalence and antimicrobial susceptibility level of typhoid fever in Ethiopia: A systematic review and meta-analysis

Typhoid fever continues to be a health challenge in low-and middle-income countries where access to clean water and sanitation infrastructure is scarce. The non-confirmatory diagnostic method continues to hinder effective diagnosis and treatment, ensuring in a high antimicrobial resistance. This systematic review and meta-analysis aimed to estimate the pooled prevalence and antimicrobial susceptibility level of typhoid fever in Ethiopia. The review was designed based on the condition-context-population review approach. Fifteen eligible articles were identified from PubMed, Google Scholar, and Science Direct databases. Risk of bias and quality of studies were assessed using the Joanna Briggs Institute's appraisal criteria. Heterogeneity was assessed using Cochran's Q test and I2 statistics. The review protocol was registered in PROSPERO (registration number CRD42021224478). The estimated pooled prevalence of typhoid fever from blood and stool culture diagnosis was 3% (95% CI: 2%-4%, p < 0.01) (I2  = 82.25) and Widal test examination 33% (95% CI: 22%-44%) (I2  = 99.14). The sub-group analyses identified a lower detection of typhoid fever of 2% (95% CI: 1%-3%) among febrile patients compared to typhoid suspected cases of 6% (95% CI: 2%-9%). The stool culture test identified was twofold higher, value of 4% (95% CI: 2%-7%) salmonella S. Typhi infection than blood culture test of 2% (95% CI: 1%-4%). The antimicrobial susceptibility of salmonella S. Typhi for antibiotics was 94%, 80% and 65% for ceftriaxone, ciprofloxacin, and gentamycin respectively. Low susceptibility of salmonella S. Typhi isolates against nalidixic acid 22% (95% CI: 2%-46%) and chloramphenicol 11% (95% CI: 2%-20%) were observed. The diagnosis of typhoid fever was under or overestimated depending on the diagnostic modality. The Widal test which identified as nonreliable has long been used in Ethiopia for the diagnosis of salmonella S. Typhi causing high diagnosis uncertainties. Antimicrobial susceptibility of salmonella S. Typhi was low for most nationally recommended antibiotics. Ethiopian Food and Drug Authority must strengthen its continued monitoring and enhanced national antimicrobial surveillance system using the best available state-of-the-art technology and or tools to inform the rising resistance of salmonella S. Typhi towards the prescription of standard antibiotics. Finally, it is crucial to develop an evidence-based clinical decision-making support system for the diagnosis, empiric treatment and prevention of antimicrobial resistance.

Case Report: Near-Fatal Intestinal Hemorrhage and Acute Acalculous Cholecystitis due to Vi-Negative and Fluoroquinolone-Insensitive Salmonella enterica Serovar Typhi Infection: A Rare Entity

Typhoid fever is usually a mild clinical disease. Typhoid fever with massive intestinal hemorrhage is rare in the antibiotic era. Acute acalculous cholecystitis (AAC) is also rare in adults. Here, we describe the first adult case of typhoid fever with both complications due to Vi-negative and fluoroquinolone-insensitive Salmonella enterica serovar Typhi (S. Typhi) infection. We aim to alert physicians to this rare condition.

"One for All": Functional Transfer of OMV-Mediated Polymyxin B Resistance From Salmonella enterica sv. Typhi ΔtolR and ΔdegS to Susceptible Bacteria

The appearance of multi-resistant strains has contributed to reintroducing polymyxin as the last-line therapy. Although polymyxin resistance is based on bacterial envelope changes, other resistance mechanisms are being reported. Outer membrane vesicles (OMVs) are nanosized proteoliposomes secreted from the outer membrane of Gram-negative bacteria. In some bacteria, OMVs have shown to provide resistance to diverse antimicrobial agents either by sequestering and/or expelling the harmful agent from the bacterial envelope. Nevertheless, the participation of OMVs in polymyxin resistance has not yet been explored in S. Typhi, and neither OMVs derived from hypervesiculating mutants. In this work, we explored whether OMVs produced by the hypervesiculating strains Salmonella Typhi ΔrfaE (LPS synthesis), ΔtolR (bacterial envelope) and ΔdegS (misfolded proteins and σ ^E activation) exhibit protective properties against polymyxin B. We found that the OMVs extracted from S. Typhi ΔtolR and ΔdegS protect S. Typhi WT from polymyxin B in a concentration-depending manner. By contrast, the protective effect exerted by OMVs from S. Typhi WT and S. Typhi ΔrfaE is much lower. This effect is achieved by the sequestration of polymyxin B, as assessed by the more positive Zeta potential of OMVs with polymyxin B and the diminished antibiotic's availability when coincubated with OMVs. We also found that S. Typhi ΔtolR exhibited an increased MIC of polymyxin B. Finally, we determined that S. Typhi ΔtolR and S. Typhi ΔdegS, at a lesser level, can functionally and transiently transfer the OMV-mediated polymyxin B resistance to susceptible bacteria in cocultures. This work shows that mutants in genes related to OMVs biogenesis can release vesicles with improved abilities to protect bacteria against membrane-active agents. Since mutations affecting OMV biogenesis can involve the bacterial envelope, mutants with increased resistance to membrane-acting agents that, in turn, produce protective OMVs with a high vesiculation rate (e.g., S. Typhi ΔtolR) can arise. Such mutants can functionally transfer the resistance to surrounding bacteria via OMVs, diminishing the effective concentration of the antimicrobial agent and potentially favoring the selection of spontaneous resistant strains in the environment. This phenomenon might be considered the source for the emergence of polymyxin resistance in an entire bacterial community.

Food Safety Challenges in Refugee Camps: What Do We Know?

ABSTRACT

Refugee camps provide basic necessities such as food, water, shelter, and medical treatment for displaced persons. Unsanitary conditions in refugee camps due to overcrowding, poor sanitation systems, lack of clean water, and minimal ways to cook and store food can lead to an increased risk of foodborne illness. This article reviews the limited literature on the epidemiology of foodborne illness in refugee camps, effective risk mitigation strategies, and opportunities for future research. Eleven relevant articles were identified, suggesting that research in this area is limited. Identified research focused on three pathogens-Vibrio cholerae, Salmonella, and hepatitis E virus-that can cause serious diseases such as cholera, salmonellosis, typhoid fever, and hepatitis E. Storage and handling of clean water for personal hygiene and food preparation were critical components for ensuring food safety. Knowledge pertaining to best practices for hygiene and food preparation also were identified as important. Gaps in current research include determination of the prevalence of pathogens in food sold in refugee camps and development of culturally relevant food safety supply chain quality management systems. More research that focuses on burden and attribution of foodborne illness and food safety interventions in refugee camps is necessary.

HIGHLIGHTS

Typhoid fever infection - Antibiotic resistance and vaccination strategies: A narrative review

Typhoid fever is a bacterial infection caused by the Gram-negative bacterium Salmonella enterica subspecies enterica serovar Typhi (S. Typhi), prevalent in many low- and middle-income countries. In high-income territories, typhoid fever is predominantly travel-related, consequent to travel in typhoid-endemic regions; however, data show that the level of typhoid vaccination in travellers is low. Successful management of typhoid fever using antibiotics is becoming increasingly difficult due to drug resistance; emerging resistance has spread geographically due to factors such as increasing travel connectivity, affecting those in endemic regions and travellers alike. This review provides an overview of: the epidemiology and diagnosis of typhoid fever; the emergence of drug-resistant typhoid strains in the endemic setting; drug resistance observed in travellers; vaccines currently available to prevent typhoid fever; vaccine recommendations for people living in typhoid-endemic regions; strategies for the introduction of typhoid vaccines and stakeholders in vaccination programmes; and travel recommendations for a selection of destinations with a medium or high incidence of typhoid fever.

How Can the Typhoid Fever Surveillance in Africa and the Severe Typhoid Fever in Africa Programs Contribute to the Introduction of Typhoid Conjugate Vaccines?

Background

The World Health Organization now recommends the use of typhoid conjugate vaccines (TCVs) in typhoid-endemic countries, and Gavi, the Vaccine Alliance, added TCVs into the portfolio of subsidized vaccines. Data from the Severe Typhoid Fever in Africa (SETA) program were used to contribute to TCV introduction decision-making processes, exemplified for Ghana and Madagascar.

Methods

Data collected from both countries were evaluated, and barriers to and benefits of introduction scenarios are discussed. No standardized methodological framework was applied.

Results

The Ghanaian healthcare system differs from its Malagasy counterpart: Ghana features a functioning insurance system, antimicrobials are available nationwide, and several sites in Ghana deploy blood culture–based typhoid diagnosis. A higher incidence of antimicrobial-resistant Salmonella Typhi is reported in Ghana, which has not been identified as an issue in Madagascar. The Malagasy people have a low expectation of provided healthcare and experience frequent unavailability of medicines, resulting in limited healthcare-seeking behavior and extended consequences of untreated disease.

Conclusions

For Ghana, high typhoid fever incidence coupled with spatiotemporal heterogeneity was observed. A phased TCV introduction through an initial mass campaign in high-risk areas followed by inclusion into routine national immunizations prior to expansion to other areas of the country can be considered. For Madagascar, a national mass campaign followed by routine introduction would be the introduction scenario of choice as it would protect the population, reduce transmission, and prevent an often-deadly disease in a setting characterized by lack of access to healthcare infrastructure. New, easy-to-use diagnostic tools, potentially including environmental surveillance, should be explored and improved to facilitate identification of high-risk areas.

Extensively Drug-Resistant (XDR) Typhoid: Evolution, Prevention, and Its Management

Typhoid fever is the result of a human host-restricted Salmonella enteric serotype typhi infection that causes enteric fever. Around 21 million people contract typhoid annually, with Pakistan's inhabitants at most risk amongst Asian countries where typhoid remains prevalent. Decades of indiscriminate antibiotic usage has driven the evolution of multidrug-resistant strains and more recently, extensively drug-resistant (XDR) strains of Salmonella enteric serotype typhi. Current reports of extensively drug-resistant typhoid fever outbreak in Pakistan are not only a major concern for Pakistan but also for health authorities worldwide: intercontinental transmission, spread, and replacement of native strains in neighboring countries and a major impediment to Pakistani health care management. The WHO records that there are 5274 cases of extensively drug-resistant (XDR) typhoid fever out of a total of 8188 total cases of typhoid fever reported in Pakistan. The last remaining feasible oral antibiotic that XDR typhoid remains susceptible to is azithromycin; this is a cause of major concern. Additionally, several cases of XDR typhoid fever have also been reported in patients travelling from Pakistan to the USA, UK, and Canada. This review article attempts to raise the issue of XDR typhoid with respect to its epidemiology, prevention, management, and future outlook and stresses a better understanding of antimicrobial stewardship and general surveillance of the disease. Although progress is being made to combat XDR typhoid locally, efficient, unified efforts on a national and international scale are required to contain the XDR outbreak before it is no longer manageable and leads us back to the preantibiotic era.