Cost-effectiveness and public health impact of typhoid conjugate vaccine introduction strategies in Bangladesh

PURPOSE

Typhoid fever causes substantial morbidity and mortality in Bangladesh. The government of Bangladesh plans to introduce typhoid conjugate vaccines (TCV) in its expanded program on immunization (EPI) schedule. However, the optimal introduction strategy in addition to the costs and benefits of such a program are unclear.

METHODS

We extended an existing mathematical model of typhoid transmission to integrate cost data, clinical incidence data, and recently conducted serosurveys in urban, semi-urban, and rural areas. In our primary analysis, we evaluated the status quo (i.e., no vaccination) and eight vaccine introduction strategies including routine and 1-time campaign strategies, which differed by age groups targeted and geographic focus. Model outcomes included clinical incidence, seroincidence, deaths, costs, disability-adjusted life years (DALYs), and incremental cost-effectiveness ratios (ICERs) for each strategy. We adopted a societal perspective, 10-year model time horizon, and 3 % annual discount rate. We performed probabilistic, one-way, and scenario sensitivity analyses including adopting a healthcare perspective and alternate model time horizons.

RESULTS

We projected that all TCV strategies would be cost saving compared to the status quo. The preferred strategy was a nationwide introduction of TCV at 9-12 months of age with a single catch-up campaign for children ages 1-15, which was cost saving compared to all other strategies and the status quo. In the 10 years following implementation, we projected this strategy would avert 3.77 million cases (95 % CrI: 2.60 - 5.18), 11.31 thousand deaths (95 % CrI: 3.77 - 23.60), and save $172.35 million (95 % CrI: -14.29 - 460.59) compared to the status quo. Our findings were broadly robust to changes in parameter values and willingness-to-pay thresholds.

CONCLUSIONS

We projected that nationwide TCV introduction with a catch-up campaign would substantially reduce typhoid incidence and very likely be cost saving in Bangladesh.

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.Communicated by Ramaswamy H. Sarma.

Dual immunization with CdtB protein and flagellin epitope offers augmented protection against enteric fever in mice

AIMS

Present study has explored the protective response of dual immunization using two different antigenic entities (i.e. flagellin epitope and cytolethal distending toxin subunit B (CdtB) protein) against lethal challenge of typhoidal serovars in a murine model.

MAIN METHODS

In-vitro immunogenicity of flagellin epitope-BSA conjugate and CdtB protein was confirmed using Indirect ELISA of typhoid positive patients' sera. Further, both entities were administered intraperitoneally in mice individually or in combination, followed by lethal challenge of typhoidal Salmonellae. Various parameters were analysed such as bacterial burden, mice survival, histopathological analysis, cytokine analysis and immunophenotyping. Serum samples obtained from the immunized mice were used for passive immunization studies, wherein mice survival and mechanism of action of the generated antibodies was studied.

KEY FINDINGS

Active immunization studies using the combination of both entities demonstrated improved mice survival after lethal challenge with typhoidal Salmonellae, reduced bacterial burden in organs, expression of immunophenotypic markers in splenocytes and restored tissue histoarchitecture. When used in combination, the effective doses of both the candidates reduced which may be attributed to multiprong approach used by the immune system to recognize Salmonella. Passive immunization studies further determined the protective efficacy of generated antibodies by different mechanisms such as complement mediated bactericidal action, swarming inhibition and increased phagocytic uptake.

SIGNIFICANCE

Present study is the first phase of the proof-of-concept which may prove to be beneficial in developing an effective bi-functional vaccine candidate to render protection against both Vi-positive as well as Vi-negative Salmonella strains.

Novel Heptaplex PCR-Based Diagnostics for Enteric Fever Caused by Typhoidal Salmonella Serovars and Its Applicability in Clinical Blood Culture

Enteric fever is caused by typhoidal Salmonella serovars (Typhi, Paratyphi A, Paratyphi B, and Paratyphi C). Owing to the importance of Salmonella serovars in clinics and public hygiene, reliable diagnostics for typhoidal serovars are crucial. This study aimed to develop a novel diagnostic tool for typhoidal Salmonella serovars and evaluate the use of human blood for clinically diagnosing enteric fever. Five genes were selected to produce specific PCR results against typhoidal Salmonella serovars based on the genes of Salmonella Typhi. Heptaplex PCR, including genetic markers of generic Salmonella, Salmonella enterica subsp. enterica, and typhoidal Salmonella serovars, was developed. Typhoidal Salmonella heptaplex PCR using genomic DNAs from 200 Salmonella strains (112 serovars) provided specifically amplified PCR products for each typhoidal Salmonella serovar. These results suggest that heptaplex PCR can sufficiently discriminate between typhoidal and nontyphoidal Salmonella serovars. Heptaplex PCR was applied to Salmonella-spiked blood cultures directly and provided diagnostic results after 12- or 13.5-h blood culture. Additionally, it demonstrated diagnostic performance with colonies recovered from a 6-h blood culture. This study provides a reliable DNA-based tool for diagnosing typhoidal Salmonella serovars that may be useful in clinical microbiology and epidemiology.

Increased antimicrobial resistance among non-typhoidal Salmonella infections in international travellers returning to the Netherlands

Highlights Increased fluoroquinolone resistance in the two most common non-typhoidal Salmonella (NTS) serotypes among travellers returning to the Netherlands.Resistant Salmonella Enteritidis infections are most likely to be acquired abroad, specifically outside Europe.This study highlights the importance of travel history when patients with NTS infections require empiric antimicrobial treatment.

Typhoid with pancytopenia: Revisiting a forgotten foe: Two case reports

BACKGROUND

Typhoid fever is a public health problem in Asia and Africa. Pancytopenia has been rarely reported during the 20^th century. Reports during the last 20 years are scarce.

CASE SUMMARY

Our first patient was a young adult male presenting with febrile neutropenia whose blood and bone marrow cultures grew Salmonella typhi. He recovered before discharge from the hospital. The second was a primigravida who had an abortion following a febrile illness and was found to have pancytopenia. The Widal test showed high initial titers, and she was presumptively treated for typhoid. Convalescence showed a doubling of Widal titers.

CONCLUSION

Typhoid fever continued to show up as a fever with cytopenia demanding significant effort and time in working up such patients. In developing countries, the liaison with typhoid continues.

Potential of a novel flagellin epitope as a broad-spectrum vaccine candidate against enteric fever

Relentless emergence of antibiotic resistant Salmonella strains, coupled with the drawbacks associated with currently available vaccines against enteric fever, warrants an urgent need to look for new vaccine candidates. Out of the multiple virulence factors harbored by Salmonella, flagella are regarded as one of the most important targets of innate as well as adaptive immune response. Individual Salmonella serotypes alternate between expression of two different antigenic forms encoded by fliC and fljB genes, respectively thereby employing this as a strategy to escape the host immune response. In the present study, using various immunoinformatic approaches, a flagellin epitope, present in both antigenic forms of typhoidal Salmonellae has been targeted. Following B-cell epitope and B-cell derived T-cell epitope prediction and interaction studies with major histocompatibility complexes using molecular docking, a peptide epitope was selected. Further, it was screened for its presence in majority of typhoidal serovars along with other useful attributes, in silico. Thereafter, safety studies were performed with the synthesized peptide. Subsequently, immunization studies were carried out using S. Typhi as well as S. Paratyphi A induced murine peritonitis model. Active immunization with peptide-BSA conjugate resulted in 75% and 80% mice survival following lethal challenge with S. Typhi and S. Paratyphi A respectively, along with a significant IgG antibody titer, thereby highlighting its immunogenic potential. Reduced bacterial burden in vital organs along with improved histoarchitecture and cytokine levels further substantiated the protective efficacy of the proposed candidate. Passive immunization studies with the candidate verified the protective efficacy of the generated antibodies against lethal challenge of bacteria in mice. Given the endemic nature of enteric fever and the antigenic variability observed in Salmonella serotypes, present study highlights the importance of using a vaccine candidate, which, along with generating a strong immune response, also exhibits a broad coverage against both, S. Typhi as well as S. Paratyphi A strains.

The genomic characterization of Salmonella Paratyphi A from an outbreak of enteric fever in Vadodara, India

Salmonella enterica Typhi (S. Typhi) and Paratyphi A (S. Paratyphi A) are the causative agents of enteric fever, a systemic human disease with a burden of 300 000 cases per year in India. The majority of enteric fever cases are associated with S. Typhi, resulting in a paucity of data regarding S. Paratyphi A, specifically with respect to genomic surveillance and antimicrobial resistance (AMR). Here, we exploited whole-genome sequencing (WGS) to identify S. Paratyphi A genotypes and AMR determinants associated with an outbreak of S. Paratyphi A in Vadodara, India, from December 2018 to December 2019. In total 117 S. Paratyphi A were isolated and genome sequenced, most were genotype 2.4.2 (72.6 % of all cases), which is the globally dominant genotype. The remainder were genotype 2.3 (25.6 %), while only two isolates belonged to genotype 2.4.1. A single base-pair mutation in gyrA, associated with reduced susceptibility to fluoroquinolones, was present in all of the outbreak isolates; with 74.35 % of isolates having a S83F substitution and the remainder having an S83Y substitution. Our surveillance study suggests that S. Paratyphi A is an emergent pathogen in South Asia, which may become increasingly relevant with the introduction of Vi conjugate vaccines.

Immunoinformatic approach employing modeling and simulation to design a novel vaccine construct targeting MDR efflux pumps to confer wide protection against typhoidal Salmonella serovars

Overcoming multi drug resistance is one of the crucial challenges to control enteric typhoid fever caused by Salmonella typhi and Salmonella paratyphi. Overexpression of efflux pumps predominantly causes drug resistance in microorganisms. Therefore, immunotherapy targeting the various efflux pumps antigens could be a promising strategy to increase the success of vaccines. An immunoinformatic approach was employed to design a Salmonellosis multi-epitope subunit vaccine peptide consisting of linear B-cell and T-cell epitopes of multidrug resistance protein families including ATP Binding Cassette (ABC), major facilitator superfamily (MFS), resistance nodulation cell division (RND), small multidrug resistance (SMR), and multidrug and toxin extrusion (MATE). The selected epitopes exhibited conservation in both S. typhi and S. paratyphi and thus could be helpful for cross-protection. Further, the final vaccine construct encompassing the peptides, adjuvants and specific linker sequences showed high immunogenicity, solubility, non-allergenic, nontoxic, and wide population coverage due to strong binding affinity to maximum HLA alleles. The three-dimensional structure was predicted, and validated using various structure validation tools. Additionally, protein-protein docking of the chimeric vaccine construct with the TLR-2 protein and molecular dynamics demonstrated stable and efficient binding. Conclusively, the immunoinformatic study showed that the novel multi epitopic vaccine construct can simulate the both T-cell and B-cell immune responses in typhoidal Salmonella serovars and could potentially be used for prophylactic or therapeutic applications.Communicated by Ramaswamy H. Sarma.

Reverse engineering approach: a step towards a new era of vaccinology with special reference to Salmonella

INTRODUCTION

Salmonella is responsible for causing enteric fever, septicemia, and gastroenteritis in humans. Due to high disease burden and emergence of multi- and extensively drug-resistant Salmonella strains, it is becoming difficult to treat the infection with existing battery of antibiotics as we are not able to discover newer antibiotics at the same pace at which the pathogens are acquiring resistance. Though vaccines against Salmonella are available commercially, they have limited efficacy. Advancements in genome sequencing technologies and immunoinformatics approaches have solved the problem significantly by giving rise to a new era of vaccine designing, i.e. 'Reverse engineering.' Reverse engineering/vaccinology has expedited the vaccine identification process. Using this approach, multiple potential proteins/epitopes can be identified and constructed as a single entity to tackle enteric fever.

AREAS COVERED

This review provides details of reverse engineering approach and discusses various protein and epitope-based vaccine candidates identified using this approach against typhoidal Salmonella.

EXPERT OPINION

Reverse engineering approach holds great promise for developing strategies to tackle the pathogen(s) by overcoming the limitations posed by existing vaccines. Progressive advancements in the arena of reverse vaccinology, structural biology, and systems biology combined with an improved understanding of host-pathogen interactions are essential components to design new-generation vaccines.

Clinical manifestations and microbiological features between indigenous and imported enteric fever in Taiwan, 2010-2020

Previous studies had showed that indigenous clones of Salmonella Typhi and S. Paratyphi were originally imported from other countries in Taiwan. We presented the clinical manifestations and laboratory findings of indigenous and imported enteric fever cases in Taiwan in the current decade. We retrospectively reviewed typhoid and paratyphoid fever cases in two medical centers of Chang Gung Memorial Hospitals in 2010-2020. A total of 37 enteric fever cases including 24 typhoid fever and 13 paratyphoid fever were recorded. There were 20 indigenous cases, 16 imported cases, and one indetermined case. Splenomegaly and hepatitis were more frequent in typhoid fever than in paratyphoid fever (P < 0.05). Imported cases had more ciprofloxacin non-susceptibility rate (8/16, 50.0%) than indigenous cases (2/20, 10%). Indigenous ciprofloxacin non-susceptible S. Typhi isolates were found in 2018. One indigenous S. Paratyphi B isolate was multi-drug resistant (MDR) to chloramphenicol, ampicillin, and trimethoprim/sulfamethoxazole.

Outpatient management of uncomplicated enteric fever: A case series of 93 patients from the Hospital of Tropical Diseases, London

OBJECTIVES

Enteric fever is predominantly managed as an outpatient condition in endemic settings but there is little evidence to support this approach in non-endemic settings. This study aims to review the outcomes of outpatients treated for enteric fever at the Hospital of Tropical Diseases in London, UK.

METHODS

We conducted a retrospective analysis of all patients with confirmed enteric fever between August 2009 and September 2020. Demographic, clinical, laboratory and microbiological data were collected and compared between the inpatient and outpatient populations. Outcomes investigated were complicated enteric fever, treatment failure and relapse.

RESULTS

Overall, 93 patients (59% male, median age 31) were identified with blood and/or stool culture confirmed enteric fever and 49 (53%) of these were managed as outpatients. The commonest empirical treatment for outpatients was azithromycin (70%) and for inpatients was ceftriaxone (84%). Outpatients were more likely than inpatients to receive only one antibiotic (57% vs 19%, p < 0.01) and receive a shorter duration of antibiotics (median 7 vs 11 days, p <0.01). There were no cases of complicated disease or relapse in either the inpatient or outpatient groups. There was one treatment failure in the outpatient group. Azithromycin was well-tolerated with no reported side effects.

CONCLUSIONS

Our findings suggest that outpatient management of uncomplicated imported enteric fever is safe and effective with the use of oral azithromycin. Careful monitoring of patients is recommended as treatment failure can occur.

Etiological spectrum of persistent fever in the tropics and predictors of ubiquitous infections: a prospective four-country study with pooled analysis

BACKGROUND

Persistent fever, defined as fever lasting for 7 days or more at first medical evaluation, has been hardly investigated as a separate clinical entity in the tropics. This study aimed at exploring the frequencies and diagnostic predictors of the ubiquitous priority (i.e., severe and treatable) infections causing persistent fever in the tropics.

METHODS

In six different health settings across four countries in Africa and Asia (Sudan, Democratic Republic of Congo [DRC], Nepal, and Cambodia), consecutive patients aged 5 years or older with persistent fever were prospectively recruited from January 2013 to October 2014. Participants underwent a reference diagnostic workup targeting a pre-established list of 12 epidemiologically relevant priority infections (i.e., malaria, tuberculosis, HIV, enteric fever, leptospirosis, rickettsiosis, brucellosis, melioidosis, relapsing fever, visceral leishmaniasis, human African trypanosomiasis, amebic liver abscess). The likelihood ratios (LRs) of clinical and basic laboratory features were determined by pooling all cases of each identified ubiquitous infection (i.e., found in all countries). In addition, we assessed the diagnostic accuracy of five antibody-based rapid diagnostic tests (RDTs): Typhidot Rapid IgM, Test-it^TM Typhoid IgM Lateral Flow Assay, and SD Bioline Salmonella typhi IgG/IgM for Salmonella Typhi infection, and Test-it^TM Leptospira IgM Lateral Flow Assay and SD Bioline Leptospira IgG/IgM for leptospirosis.

RESULTS

A total of 1922 patients (median age: 35 years; female: 51%) were enrolled (Sudan, n = 667; DRC, n = 300; Nepal, n = 577; Cambodia, n = 378). Ubiquitous priority infections were diagnosed in 452 (23.5%) participants and included malaria 8.0% (n = 154), tuberculosis 6.7% (n = 129), leptospirosis 4.0% (n = 77), rickettsiosis 2.3% (n = 44), enteric fever 1.8% (n = 34), and new HIV diagnosis 0.7% (n = 14). The other priority infections were limited to one or two countries. The only features with a positive LR ≥ 3 were diarrhea for enteric fever and elevated alanine aminotransferase level for enteric fever and rickettsiosis. Sensitivities ranged from 29 to 67% for the three RDTs targeting S. Typhi and were 9% and 16% for the two RDTs targeting leptospirosis. Specificities ranged from 86 to 99% for S. Typhi detecting RDTs and were 96% and 97% for leptospirosis RDTs.

CONCLUSIONS

Leptospirosis, rickettsiosis, and enteric fever accounted each for a substantial proportion of the persistent fever caseload across all tropical areas, in addition to malaria, tuberculosis, and HIV. Very few discriminative features were however identified, and RDTs for leptospirosis and Salmonella Typhi infection performed poorly. Improved field diagnostics are urgently needed for these challenging infections.

TRIAL REGISTRATION

NCT01766830 at ClinicalTrials.gov.

Epidemiology of Multidrug Resistance among Salmonella enterica serovars typhi and paratyphi A at a Tertiary Pediatric Hospital in India Over a Decade; In-silico Approach to Elucidate the Molecular Mechanism of Quinolone Resistance

BACKGROUND

Enteric fever caused by Salmonella enterica serovar typhi and Salmonella enterica serovar paratyphi A remains one of the most common causes of community-acquired bloodstream infection among children in India. Multidrug resistance is emerging and is a cause of concern as it affects the choice of treatment in enteric fever.

METHOD

In this study, a 10-year analysis of resistance patterns was done along with in-silico homology modeling and molecular docking to understand the commonly occurring quinolone resistance.

RESULTS

A total of 1010 cases of blood culture-confirmed enteric fevers (S. typhi n=849; S. paratyphi A n=161) were recorded at the study hospital during the period from 2011-2020. Multidrug resistance among cases of S. typhi was 2.12 %, whereas it was completely absent among cases of S. paratyphi A. Fluoroquinolone resistance was high (>95%) throughout the study period. Resistance to ampicillin, chloramphenicol and co-trimoxacole was low (<3%) among S. typhi cases. No deaths were observed among study participants. Molecular docking analysis showed that quinolone had less binding affinity to mutated gyrase A than to its wild type for both S. typhi and S. paratyphi A.

CONCLUSION

Quinolone resistance was high among cases of enteric fever, whereas no resistance was observed among third-generation cephalosporins. In-silico studies indicated that a mutation in gyrase A might be the cause of the gradual increase in ciprofloxacin resistance over the study period.

gyrA ser83 mutation among fluoroquinolone-resistant Salmonella enterica serovars from enteric fever patients in tertiary care hospital, Kathmandu

BACKGROUND

The management of enteric fever through antibiotics is difficult these days due to the emerging resistance of Salmonella to various antimicrobial agents. The development of antimicrobial resistance is associated with multiple factors including mutations in the specific genes. To know the current status of mutation-mediated fluoroquinolone-resistance among Salmonella enterica serovars; Typhi, Paratyphi A, B and C, this study was focused on detecting gyrA ser83 mutation by restriction digestion analysis of gyrA gene using HinfI endonuclease.

RESULTS

A total of 948 blood samples were processed for isolation of Salmonella spp. and 3.4% of them were found to be positive for Salmonella growth. Out of the 32 Salmonella isolates, 2.2% were S. Typhi and 1.2% were S. Paratyphi A. More interestingly, we observed less than 5% of isolates were resistant to first-line drugs including chloramphenicol, cotrimoxazole and ampicillin. More than 80% of isolates were resistant to fluoroquinolones accounting for 84.4% to levofloxacin followed by 87.5% to ofloxacin and 100% to ciprofloxacin by disc diffusion methods. However, the minimum inhibitory concentration method using agar dilution showed only 50% of isolates were resistant to ciprofloxacin. A total of 3.1% of isolates were multidrug-resistant. Similarly, 90.6% of the Salmonella isolates showed gyrA ser83 mutation with resistance to nalidixic acid.

CONCLUSIONS

The increased resistance to fluoroquinolones and nalidixic acid in Salmonella isolates in our study suggests the use of alternative drugs as empirical treatment. Rather, the treatment should focus on prescribing first-line antibiotics since we observed less than 5% of Salmonella isolates were resistant to these drugs.

Salmonellosis Including Enteric Fever

Salmonella is a gram-negative, motile, nonsporulating, facultative anaerobic bacillus, belongs to the family Enterobacteriaceae. The bacteria were first identified in 1884. It is transmitted through direct contact with an infected person or indirect contact by the consumption of contaminated food and water. More than 2500 serotypes of Salmonella enterica have been identified but less than 100 serotypes are known to cause infections in humans. S. enterica serovar typhi (S. typhi) and S. enterica serovar paratyphi (S. paratyphi A B C) cause enteric fever, whereas nontyphoidal Salmonella serotypes (NTS) cause diarrhea. NTS commonly presents with gastroenteritis and is a self-limiting disease. Enteric fever is a potentially life-threatening acute febrile systemic infection and is diagnosed by isolating a pathogen on culture. With the emergence of the extensive drug-resistant (XDR) S. typhi clone, limited treatment options are available. Vaccination of persons at risk, improvement of sanitation, promotion of food hygiene, and detection and control of chronic carriers are essential preventive control measures of enteric fever.

Analysis of Salmonella Typhi Pathogenesis in a Humanized Mouse Model

Efforts to understand molecular mechanisms of pathogenesis of the human-restricted pathogen Salmonella enterica serovar Typhi, the causative agent of typhoid fever, have been hampered by the lack of a tractable small animal model. This obstacle has been surmounted by a humanized mouse model in which genetically modified mice are engrafted with purified CD34+ stem cells from human umbilical cord blood, designated CD34+ Hu-NSG (formerly hu-SRC-SCID) mice. We have shown that these mice develop a lethal systemic infection with S. Typhi that is dependent on the presence of engrafted human hematopoietic cells. Immunological and pathological features of human typhoid are recapitulated in this model, which has been successfully employed for the identification of bacterial genetic determinants of S. Typhi virulence. Here we describe the methods used to infect CD34+ Hu-NSG mice with S. Typhi in humanized mice and to construct and analyze a transposon-directed insertion site sequencing S. Typhi library, and provide general considerations for the use of humanized mice for the study of a human-restricted pathogen.

Typhoid fever in travellers: estimating the risk of acquisition by country

BACKGROUND

Typhoid fever is a notifiable disease within Australia. Although studies in endemic regions give an indication of acquisition risk, many countries lack reliable data, and little is known of the absolute or relative risk in Australian travellers. By combining notified case data with travel statistics provided by the Australian Bureau of Statistics, the aim of this study was to give an indication of risk for typhoid acquisition among Australian travellers.

METHODS

Australian typhoid notifications between 1st January 2010 and 30th June 2017 were grouped by country of acquisition and age category (<15 or ≥15 years). Australian travel data were used to inform time at risk and incidence rate of Australian typhoid notifications pertaining to country and region of acquisition. Salmonella Paratyphi infections, though notifiable, were excluded as the focus was vaccine preventable illness. Data from New South Wales and Victoria were used to examine the incidence in those acquiring infection in their country of birth (COB) against travellers who did not.

RESULTS

Nine hundred twenty-three cases of typhoid were notified over the period of review, 96% of which were acquired overseas. The greatest determinant of risk was travel destination, with countries in south Asia associated with highest crude incidence rate (252 per 100 000 person-years), particularly Bangladesh. Younger age and immigrants returning to their COB were generally associated with higher risk of acquisition.

CONCLUSIONS

The risk of typhoid fever in Australian travellers to endemic regions is considerable. Immigrants returning to their COB appear to be at higher risk and it is likely that this risk extends to their traveling dependents. These findings help clinicians and public health officials to plan and advise pre-travel vaccination strategies with at-risk individuals and groups. Additional sociodemographic data collection with Australian typhoid notifications would enhance the surveillance of differing international travel risk groups leaving Australia.

Salmonella paratyphi-induced splenic vein thrombosis: A case report on infrequent cause of acute abdomen

Splenic vein thrombosis and splenic infarction are complications beyond the usual clinical spectrum of paratyphoid fever, and the presentation is rarely described. We report the case of a young female, who presented with high-grade fever and severe left upper quadrant pain. Her blood culture was positive for Salmonella paratyphi A, with Widal test suggesting 4-fold rise in titers. Computed tomography revealed splenic vein thrombosis and multiple splenic infarcts, for which antibiotic and anticoagulation were instituted simultaneously. She had a complete resolution with this management, and anticoagulation was tapered off on subsequent visits.

Incidence of Enteric Fever in a Pediatric Cohort in North India: Comparison with Estimates from 20 Years Earlier

BACKGROUND

An earlier cohort in 1995-1996 showed a very high burden of typhoid in Delhi. Our aim was to estimate the current overall and age-specific incidence of culture-confirmed enteric fever among children aged 6 months to 15 years in Delhi.

METHODS

We enrolled a cohort of 6000 children aged 6 months to <14 years in South Delhi and followed them up weekly for 24 months or until 15 completed years of child age, whichever was earlier. Blood culture to confirm enteric fever was done in children with ≥3 consecutive days of fever.

RESULTS

We recorded a total of 14 650 episodes of fever in the 11 510 person-years (PY) of follow-up. A total of 81 fever episodes were positive for enteric fever. The incidence (95% confidence interval) of all enteric fever was 703.7 (560.5-874.7) per 100 000 PY. The incidences of typhoid and paratyphoid fevers were 608.1 (95% confidence interval, 481.1-768.7) and 111.7 (59.5-191.1) per 100 000 PY, respectively, highest among children aged 10-15 years.

CONCLUSIONS

Despite a 35% reduction in incidence compared with the 1995-1996 cohort, our study suggested a substantial burden of enteric fever in the population. Continued efforts to improve water, sanitation, and hygiene parameters along with implementation of novel vaccination strategies and disease surveillance can help achieve the goal of disease elimination.

Azithromycin and cefixime combination versus azithromycin alone for the out-patient treatment of clinically suspected or confirmed uncomplicated typhoid fever in South Asia: a randomised controlled trial protocol

Background: Typhoid and paratyphoid fever (enteric fever) is a common cause of non-specific febrile infection in adults and children presenting to health care facilities in low resource settings such as the South Asia.  A 7-day course of a single oral antimicrobial such as ciprofloxacin, cefixime, or azithromycin is commonly used for its treatment. Increasing antimicrobial resistance threatens the effectiveness of these treatment choices. We hypothesize that combined treatment with azithromycin (active mainly intracellularly) and cefixime (active mainly extracellularly) will be a better option for the treatment of clinically suspected and culture-confirmed typhoid fever in South Asia. Methods: This is a phase IV, international multi-center, multi-country, comparative participant-and observer-blind, 1:1 randomised clinical trial. Patients with suspected uncomplicated typhoid fever will be randomized to one of the two interventions: Arm A: azithromycin 20mg/kg/day oral dose once daily (maximum 1gm/day) and cefixime 20mg/kg/day oral dose in two divided doses (maximum 400mg bd) for 7 days, Arm B: azithromycin 20mg/kg/day oral dose once daily (max 1gm/day) for 7 days AND cefixime-matched placebo for 7 days. We will recruit 1500 patients across sites in Bangladesh, India, Nepal, and Pakistan. We will assess whether treatment outcomes are better with the combination after one week of treatment and at one- and three-months follow-up. Discussion: Combined treatment may limit the emergence of resistance if one of the components is active against resistant sub-populations not covered by the other antimicrobial activity. If the combined treatment is better than the single antimicrobial treatment, this will be an important result for patients across South Asia and other typhoid endemic areas. Clinicaltrials.gov registration: NCT04349826 (16/04/2020).

A rare case report of enteric fever causing gallbladder perforation

Introduction and importance

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

Case presentation

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

Clinical discussion

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

Conclusions

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

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

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Gallbladder perforation is a very uncommon complication of enteric fever.

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

Association of quorum sensing and biofilm formation with Salmonella virulence: story beyond gathering and cross-talk

Enteric fever (typhoid and paratyphoid fever) is a public health concern which contributes to mortality and morbidity all around the globe. It is caused mainly due to ingestion of contaminated food and water with a gram negative, rod-shaped, flagellated bacterium known as Salmonella enterica serotype typhi (typhoid fever) or paratyphi (paratyphoid fever). Clinical problems associated with Salmonellosis are mainly bacteraemia, gastroenteritis and enteric fever. The bacteria undergo various mechanisms to escape itself from immune reaction of the host, modulating immune response at the site of infection leading to virulence factor production and anti-microbial resistance. Biofilm is one of the adaptation mechanisms through which Salmonella survives in unfavourable conditions and thus is considered as a major threat to public health. Another property of the bacteria is "Quorum Sensing", which is a cell-cell communication and most of the pathogenic bacteria use it to coordinate the production of several virulence factors and other behaviours such as swarming and biofilm formation. Earlier, quorum sensing was believed to be just a medium for communication but, later on, its role in virulence has been studied. However, there are negligible information relating to interaction between quorum sensing and biofilm formation and how these events play crucial role in Salmonella pathogenesis. The review is a summary of updated information regarding how Salmonella uses these properties to spread more and survive better, making a challenge for clinicians and public health experts. Therefore, this review would help bring an insight regarding how biofilm formation and quorum sensing are inter-related and their role in pathogenesis and virulence of Salmonella.

Can Triggering Receptors Expressed on Myeloid Cells be used for Diagnosis of Salmonella Typhi Infection?

BACKGROUND

There is a need for rapid and accurate diagnostic biomarker for diagnosis of Salmonella fever.

AIMS

The aim of the present study was to assess the importance of procalcitonin (PCT), Soluble Triggering Receptors expressed on Myeloid Cells 1 (sTREM1) and C- reactive protein (CRP) in the diagnosis of enteric fever with positive blood culture for S.typhi.

METHODS

Blood samples were withdrawn from 200 patients with suspected enteric fever and subjected for the determination of CRP, PCT and sTREM-1.

RESULTS

The sensitivity and specificity for PCT cut off were 97.7% & 82.5%, for CRP the sensitivity and specificity were 95.3% and 77% and for s-TREM-1 the sensitivity and specificity were 95.3% & 77%.

CONCLUSION

S-TREM-1 may be considered as a novel biomarker for the diagnosis of enteric fever with good sensitivity and specificity.

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

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

Laboratory Diagnosis of Tropical Infections

Highlights

(1) Blood culture is the gold standard for the diagnosis of bacterial infections. (2) Bone marrow culture is more sensitive than blood culture even in patients with enteric fever receiving antibiotics. (3) Microscopic agglutination test is considered the gold standard for diagnosing leptospirosis; however, now IgM ELISA and polymerase chain reaction (PCR) are more frequently used for diagnosis. (4) Tuberculosis is diagnosed with the help of nucleic acid amplification tests like Xpert MTB/RIF Ultra which also detects rifampicin resistance. Other tests include microscopy, Lowenstein-Jensen and mycobacteria growth indicator tube culture, line probe assay. (5) Tropical rickettsial infections are diagnosed by serological reactions (Weil-Felix, ELISA for antibodies) and PCR. (6) For Brucellosis culture from blood, bone marrow or tissue specimens remain the mainstay in diagnosis. (7) Dengue, Zika, Crimean-Congo hemorrhagic fever, Ebola, hantavirus, rabies are diagnosed with reverse transcriptase-polymerase chain reaction. Serological tests like IgM ELISA or paired sera samples for IgG are also used for diagnosis.

How to cite this article

Basu S, Shetty A. Laboratory Diagnosis of Tropical Infections. Indian J Crit Care Med 2021;25(Suppl 2):S122-S126.

Salmonella Paratyphi Infection: Use of Nanopore Sequencing as a Vivid Alternative for the Identification of Invading Bacteria

In our study we present an overview of the use of Oxford Nanopore Technologies (ONT) sequencing technology on the background of Enteric fever. Unlike traditional methods (e.g., qPCR, serological tests), the nanopore sequencing technology enables virtually real-time data generation and highly accurate pathogen identification and characterization. Blood cultures were obtained from a 48-year-old female patient suffering from a high fever, headache and diarrhea. Nevertheless, both the initial serological tests and stool culture appeared to be negative. Therefore, the bacterial isolate from blood culture was used for nanopore sequencing (ONT). This technique in combination with subsequent bioinformatic analyses allowed for prompt identification of the disease-causative agent as Salmonella enterica subsp. enterica serovar Paratyphi A. The National Reference Laboratory for Salmonella (NIPH) independently reported this isolate also as serovar Paratyphi A on the basis of results of biochemical and agglutination tests. Therefore, our results are in concordance with certified standards. Furthermore, the data enabled us to assess some basic questions concerning the comparative genomics, i.e., to describe whether the isolated strain differs from the formerly published ones or not. Quite surprisingly, these results indicate that we have detected a novel and so far, unknown variety of this bacteria.

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.

Robust immunity induced by multi-epitope DnaK peptides, potential vaccine candidates against Salmonella: An in vitro study

Enteric fever is a common yet serious issue, most troublesome in underdeveloped and developing nations affecting all age group primarily children. Pitfalls of existing vaccines along with rapidly rising Multi-Drug-Resistant Salmonella strains necessitate the need for the development of new vaccine candidates having potential to provide complete protection. Several vaccine strategies are being pursued to stimulate protective immunity against typhoid, including conjugate vaccines for the elicitation of cellular and humoral responses as both arms of immunity are essential for complete protection. Bacterial HSPs are highly immunogenic to produce humoral and cellular immune responses. In this study, we are reporting in vitro immunostimulatory activity of immunodominant multi-epitope protective antigenic DnaK peptides identified earlier by immunoinformatics approach. Remarkable increase in antibody titer, lymphocyte proliferation, cytokines and NO level with individual /mixture of DnaK peptides as compared to control demonstrate immunogenic potential of these peptides that effectively augments both humoral and cellular immune responses. None of the peptides cause any hemolysis in human RBCs. Overall; our findings strongly elucidate the immune-stimulatory potential of DnaK peptides to be explored as potent vaccine candidates against multiple pathogens.

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.

Typhoid and paratyphoid fever: a clinical seminar

Rationale for review: Enteric fever (EF) caused by Salmonella enterica subspecies enterica serovar Typhi (Salmonella Typhi) and S. Paratyphi (Salmonella Paratyphi) remains an important cause of infectious morbidity and mortality in many low-income countries and, therefore, still poses a major infectious risk for travellers to endemic countries. Main findings: Although the global burden of EF has decreased over the past two decades, prevalence of EF remains high in Asia and Africa, with the highest prevalence reported from the Indian subcontinent. These statistics are mirrored by data on travel-related EF. Widespread and increasing antimicrobial resistance has narrowed treatment options for travel-related EF. Ceftriaxone- and azithromycin-based therapies are commonly used, even with the emergence of extremely drug-resistant typhoid in Pakistan. Preventive measures among locals and travellers include provision of safe food and water and vaccination. Food and water precautions offer limited protection, and the efficacy of Salmonella Typhi vaccines is only moderate signifying the need for travellers to be extra cautious. Recommendations: Improvement in the diagnosis of typhoid with high degree of clinical suspicion, better diagnostic assays, early and accurate detection of resistance, therapy with appropriate drugs, improvements in hygiene and sanitation with provision of safe drinking water in endemic areas and vaccination among travellers as well as in the endemic population are keys to controlling typhoid. While typhoid vaccines are recommended for travellers to high-risk areas, moderate efficacy and inability to protect against Salmonella Paratyphi are limitations to bear in mind. Improved Salmonella Typhi vaccines and vaccines against Salmonella Paratyphi A are required.

Glycoconjugate vaccines against Salmonella enterica serovars and Shigella species: existing and emerging methods for their analysis

The global spread of enteric disease, the increasingly limited options for antimicrobial treatment and the need for effective eradication programs have resulted in an increased demand for glycoconjugate enteric vaccines, made with carbohydrate-based membrane components of the pathogen, and their precise characterisation. A set of physico-chemical and immunological tests are employed for complete vaccine characterisation and to ensure their consistency, potency, safety and stability, following the relevant World Health Organization and Pharmacopoeia guidelines. Variable requirements for analytical methods are linked to conjugate structure, carrier protein nature and size and O-acetyl content of polysaccharide. We investigated a key stability-indicating method which measures the percent free saccharide of Salmonella enterica subspecies enterica serovar Typhi capsular polysaccharide, by detergent precipitation, depolymerisation and HPAEC-PAD quantitation. Together with modern computational approaches, a more precise design of glycoconjugates is possible, allowing for improvements in solubility, structural conformation and stability, and immunogenicity of antigens, which may be applicable to a broad spectrum of vaccines. More validation experiments are required to establish the most effective and suitable methods for glycoconjugate analysis to bring uniformity to the existing protocols, although the need for product-specific approaches will apply, especially for the more complex vaccines. An overview of current and emerging analytical approaches for the characterisation of vaccines against Salmonella Typhi and Shigella species is described in this paper. This study should aid the development and licensing of new glycoconjugate vaccines aimed at the prevention of enteric diseases.

Drug-resistant Salmonella Typhi induced kidney injury with rhabdomyolysis: A case report, and literature review

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AKI secondary to Salmonella Typhi can present with rhabdomyolysis.

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Patients may require temporary dialysis with a prolonged hospital stay.

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The prognosis of ST induced rhabdomyolysis is excellent.

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We present an extensive literature review of all reported ST bacteremia cases with AKI secondary to rhabdomyolysis.

Salmonella Typhi (ST) is a rod-shaped gram-negative bacterium that infects humans via contaminated food or water. Humans are the only reservoirs for the bacteria. Infection usually manifests as fever, abdominal pain, and diarrhea. However, complications such as intestinal perforation, hepatosplenomegaly, and renal injury can occasionally occur. Acute kidney injury (AKI) is associated more commonly with ST than other bacteria causing gastrointestinal (GI) infections. The exact pathophysiology of AKI in ST infection is unknown. One of the rarely reported mechanisms is rhabdomyolysis. We present a similar case of resistant ST infection leading to AKI with rhabdomyolysis. This article also contains an extensive literature reviews of all reported ST bacteremia cases with AKI secondary to rhabdomyolysis.

A case of spastic quadriparesis secondary to enteric fever

Enteric fever is a systemic disease characterised predominantly by fever and abdominal pain, caused by dissemination of Salmonella Typhi or Salmonella Paratyphi. Enteric fever can affect many organ systems including liver, gastrointestinal tract, kidney and brain. Neurological manifestations occur in 2%-40% of patients and include meningitis, Gullian-Barré syndrome, neuritis and neuro-psychiatric symptoms. Spastic quadriparesis is a rare complication.

Susceptibility pattern of Salmonella enterica against commonly prescribed antibiotics, to febrile-pediatric cases, in low-income countries

BACKGROUND

In most low-income countries, febrile-pediatric-cases are often treated empirically with accessible antibiotics without periodic epidemiological surveillance, susceptibility testing, or minimal lethal dose calculations. With this backdrop, the study was undertaken to evaluate the susceptibility trend of Salmonella enterica against the commonly prescribed antibiotics.

METHODS

All isolates of Salmonella enterica were identified by standard protocols of biotyping and serotyping, then tested against antibiotics by the modified Kirby disk-diffusion method. Minimum Inhibitory Concentration (MIC) of isolates was determined by the agar-dilution method and compared with disk diffusion results and on nalidixic-acid sensitive/resistant strains.

RESULTS

Among 1815 febrile-pediatric patients, 90(4.9%) isolates of Salmonella enterica [serovar: Salmonella Typhi 62(68.8%) and Salmonella Paratyphi A 28(31.1%)] were recovered. The incidence of infection was higher among males, age groups 5 to 9, and patients enrolling in the out-patient department (OPD). On the disk-diffusion test, most isolates were sensitive against first-line drugs i.e.cephalosporins, and macrolides. However, against quinolones, a huge percentile 93.3%, of isolates were resistant [including 58 Typhiand 26 Paratyphiserovar] while nearly 14% were resistant against fluoroquinolones. When MICs breakpoint were adjusted as follows: 4 μg/ml for azithromycin, ≥1 μg/ml for ciprofloxacin, 2 μg/ml for ofloxacin, 8 μg/ml for nalidixic acid, and 1 μg/ml for cefixime, higher sensitivity and specificity achieved. Compared to other tested antibiotics, a low rate of azithromycin resistance was observed. Nevertheless, higher resistance against fluoroquinolones was observed on NARS strain.

CONCLUSION

Higher susceptibility of Salmonella enterica to the conventional anti-typhoidal drugs (amoxicillin, chloramphenicol, cotrimoxazole, cephotaxime) advocates for its reconsideration. Although, the lower susceptibility against fluoroquinolones among nalidixic-acid-resistant Salmonella (NARS) strain negates its empirical use among the study age group.

Typhoid and Enteric Fevers in Intensive Care Unit

Enteric fever (typhoid and paratyphoid)is caused by Salmonella typhi and Salmonella paratyphi. It is spread by fecal-oral route, largely through contamination of water and foodstuff. Developing countries are the worst affected. It takes 7 – 21 days from ingestion of the organism to manifestation of symptoms which are generally Fever, relative bradycardia, and pain abdomen. Hepatosplenomegaly, intestinal bleeding, and perforation are the features at various stages of the disease. The bacteria invade the submucous layer and proliferate in the Payer's patches. Blood culture is the gold standard for diagnosis but it is only rarely positive. Fluroquinolones, cephalosporins, and azithromycin are antibiotics of choice. There is increasing evidence of the development of resistance to all antibiotics. Salmonella sepsis, though uncommon, can occur. Intestinal perforation, peritonitis, and secondary sepsis are complications that may require intensive care unit management.

How to cite this article: Ray B, Raha A. Typhoid and Enteric Fevers in Intensive Care Unit. Indian J Crit Care Med 2021;25(Suppl 2):S144–S149.

Diagnostic Value of Clinical Features to Distinguish Enteric Fever From Other Febrile Illnesses in Bangladesh, Nepal, and Pakistan

BACKGROUND

Enteric fever, a bacterial infection caused by Salmonella enterica serotypes Typhi and Paratyphi A, frequently presents as a nonlocalizing febrile illness that is difficult to distinguish from other infectious causes of fever. Blood culture is not widely available in endemic settings and, even when available, results can take up to 5 days. We evaluated the diagnostic performance of clinical features, including both reported symptoms and clinical signs, of enteric fever among patients participating in the Surveillance for Enteric Fever in Asia Project (SEAP), a 3-year surveillance study in Bangladesh, Nepal, and Pakistan.

METHODS

Outpatients presenting with ≥3 consecutive days of reported fever and inpatients with clinically suspected enteric fever from all 6 SEAP study hospitals were eligible to participate. We evaluated the diagnostic performance of select clinical features against blood culture results among outpatients using mixed-effect regression models with a random effect for study site hospital. We also compared the clinical features of S. Typhi to S. Paratyphi A among both outpatients and inpatients.

RESULTS

We enrolled 20 899 outpatients, of whom 2116 (10.1%) had positive blood cultures for S. Typhi and 297 (1.4%) had positive cultures for S. Paratyphi A. The sensitivity of absence of cough was the highest among all evaluated features, at 65.5% (95% confidence interval [CI], 55.0-74.7), followed by measured fever at presentation at 59.0% (95% CI, 51.6-65.9) and being unable to complete normal activities for 3 or more days at 51.0% (95% CI, 23.8-77.6). A combined case definition of 3 or more consecutive days of reported fever and 1 or more of the following (a) either the absence of cough, (b) fever at presentation, or (c) 3 or more consecutive days of being unable to conduct usual activity--yielded a sensitivity of 94.6% (95% CI, 93.4-95.5) and specificity of 13.6% (95% CI, 9.8-17.5).

CONCLUSIONS

Clinical features do not accurately distinguish blood culture-confirmed enteric fever from other febrile syndromes. Rapid, affordable, and accurate diagnostics are urgently needed, particularly in settings with limited or no blood culture capacity.

Burden of Culture Confirmed Enteric Fever Cases in Karachi, Pakistan: Surveillance For Enteric Fever in Asia Project (SEAP), 2016-2019

BACKGROUND

The Surveillance for Enteric Fever in Asia Project (SEAP) is a multicenter, multicountry study conducted in Pakistan, Nepal, and Bangladesh. The objectives of the study were to characterize disease incidence among patients with enteric fever. We report the burden of enteric fever at selected sites of Karachi, Pakistan.

METHODS

During September 2016 to September 2019, prospective surveillance was conducted at inpatient, outpatient, surgical departments, and laboratory networks of Aga Khan University Hospital, Kharadar General Hospital, and surgery units of National Institute of Child Health and Jinnah Postgraduate Medical Centre. Socio-demographic, clinical, and laboratory data were obtained from all suspected or confirmed enteric fever cases.

RESULTS

Overall, 22% (2230/10 094) of patients enrolled were culture-positive for enteric fever. 94% (2093/2230) of isolates were Salmonella Typhi and 6% (137/2230) were S. Paratyphi. 15% of isolates multi-drug resistant (MDR) to first-line antibiotics and 60% were extensively drug-resistant (XDR), resistant to first-line antibiotics, fluoroquinolones and third generation cephalosporin.

CONCLUSION

Enteric fever cases have increased during the last 3 years with large proportion of drug resistant S. Typhi cases. However, the burden of paratyphoid is still relatively low. Strengthening the existing surveillance system for enteric fever and antimicrobial resistance at the national level is recommended in Pakistan to inform prevention measures. While typhoid vaccination can significantly decrease the burden of typhoid and may also impact antimicrobial resistance, water, sanitation, and hygiene improvement is highly recommended to prevent the spread of enteric fever.

Pathogen genomic surveillance of typhoidal Salmonella infection in adults and children reveals no association between clinical outcomes and infecting genotypes

BACKGROUND

India is endemic for enteric fever, and it is not known whether the variations in clinical manifestations between patients are due to host, environmental or pathogen factors.Blood culture surveillance was conducted at St. John's Medical College Hospital, Bangalore, between July 2016 and June 2017. Clinical, laboratory and demographic data were collected from each case, and bacterial isolates were subjected to whole genome sequencing. Comparative analysis between adults and paediatric patients was carried out to ascertain differences between adult and paediatric disease.

RESULTS

Among the 113 cases of blood culture-confirmed enteric fever, young adults (16-30 years) and children < 15 years accounted for 47% and 37% of cases, respectively. Anaemia on presentation was seen in 46% of cases, and 19% had an abnormal leucocyte count on presentation. The majority received treatment as inpatients (70%), and among these, adults had a significantly longer duration of admission when compared with children (p = 0.002). There were atypical presentations including arthritis, acute haemolysis and a case of repeated typhoid infection with two separate S. Typhi genotypes. There was no association between infecting genotype/serovar and treatment status (outpatient vs inpatient), month of isolation, duration of admission, patient age (adult or child), antimicrobial susceptibility, Widal positivity or haematologic parameters.

CONCLUSIONS

Amidst the many public health concerns of South India, enteric fever continues to contribute substantially to hospital burden with non-specific as well as uncommon clinical features in both paediatric and adult populations likely driven by host and environmental factors. Robust clinical surveillance as well monitoring of pathogen population structure is required to inform treatment and preventive strategies.

Diagnostic dilemma in a case of Salmonella Typhi sacroiliitis

Sacroiliitis is a rare complication of enteric fever, seen in <1% of the cases and its concomitant presence with hepatitis has been reported only once. Incorrect or delayed diagnosis of enteric fever may lead to serious complications. Here, we present a complicated case of enteric fever in a 15 years old female who was misdiagnosed elsewhere to be a case of dengue fever owing to thrombocytopenia at presentation along with a weak positive dengue IgM immunochromatography test. The patient eventually developed a rare combination of complications (sacroiliitis, hepatitis, ascites and pleural effusion) and was transferred to our hospital where specific antimicrobial treatment was instituted after isolation of Salmonella Typhi from the clinical samples. This case demonstrates the importance of establishing the correct diagnosis by optimum utilization of the diagnostic services at the time of admission to prevent potentially life threatening complications in an otherwise treatable condition.

Salmonella Typhi and Paratyphi A infections in Cambodian children, 2012-2016

OBJECTIVES

Enteric fever remains an important diagnostic and treatment challenge in febrile children living in the tropics. In the context of a national Salmonella enterica serovar Paratyphi A outbreak, the objective of this retrospective study was to compare features of S. Typhi and S. Paratyphi A infections in Cambodian children.

METHODS

Clinical and laboratory features were reviewed for 192 blood culture-confirmed children with S. Typhi and S. Paratyphi A infections presenting to a paediatric referral hospital in Siem Reap, 2012-2016.

RESULTS

Children with S. Typhi infections were younger, were more likely to have chills and/or diarrhoea, and were more frequently hospitalized than those with S. Paratyphi A infections. Over three quarters (88.3%) of S. Typhi isolates were multidrug-resistant, compared to none of the S. Paratyphi A.

CONCLUSIONS

In this small study of Cambodian children, S. Typhi infections were more severe than S. Paratyphi A infections. Antibiotic resistance limits treatment options for enteric fever in this population.

Drug-resistant enteric fever worldwide, 1990 to 2018: a systematic review and meta-analysis

BACKGROUND

Antimicrobial resistance (AMR) is an increasing threat to global health. There are > 14 million cases of enteric fever every year and > 135,000 deaths. The disease is primarily controlled by antimicrobial treatment, but this is becoming increasingly difficult due to AMR. Our objectives were to assess the prevalence and geographic distribution of AMR in Salmonella enterica serovars Typhi and Paratyphi A infections globally, to evaluate the extent of the problem, and to facilitate the creation of geospatial maps of AMR prevalence to help targeted public health intervention.

METHODS

We performed a systematic review of the literature by searching seven databases for studies published between 1990 and 2018. We recategorised isolates to allow the analysis of fluoroquinolone resistance trends over the study period. The prevalence of multidrug resistance (MDR) and fluoroquinolone non-susceptibility (FQNS) in individual studies was illustrated by forest plots, and a random effects meta-analysis was performed, stratified by Global Burden of Disease (GBD) region and 5-year time period. Heterogeneity was assessed using the I2 statistics. We present a descriptive analysis of ceftriaxone and azithromycin resistance.

FINDINGS

We identified 4557 articles, of which 384, comprising 124,347 isolates (94,616 S. Typhi and 29,731 S. Paratyphi A) met the pre-specified inclusion criteria. The majority (276/384; 72%) of studies were from South Asia; 40 (10%) articles were identified from Sub-Saharan Africa. With the exception of MDR S. Typhi in South Asia, which declined between 1990 and 2018, and MDR S. Paratyphi A, which remained at low levels, resistance trends worsened for all antimicrobials in all regions. We identified several data gaps in Africa and the Middle East. Incomplete reporting of antimicrobial susceptibility testing (AST) and lack of quality assurance were identified.

INTERPRETATION

Drug-resistant enteric fever is widespread in low- and middle-income countries, and the situation is worsening. It is essential that public health and clinical measures, which include improvements in water quality and sanitation, the deployment of S. Typhi vaccination, and an informed choice of treatment are implemented. However, there is no licenced vaccine for S. Paratyphi A. The standardised reporting of AST data and rollout of external quality control assessment are urgently needed to facilitate evidence-based policy and practice.

TRIAL REGISTRATION

PROSPERO CRD42018029432.

Draft genome of a macrolide resistant XDR Salmonella enterica serovar Paratyphi A strain using a shotgun sequencing approach

OBJECTIVES

Salmonella enterica serovar Paratyphi A, the causative pathogen of enteric fever, is a major public-health concern affecting millions of people around the world. We conducted whole-genome sequencing and analysis of a novel macrolide-resistant Salmonella Paratyphi A strain isolated from Karachi, Pakistan.

METHODS

Genomic DNA of Salmonella Paratyphi A strain JRCGR-AK14 was sequenced on a MiSeq platform. Read quality was evaluated and paired-end reads were assembled into contigs and scaffolds. The quality of contigs and scaffolds was evaluated and assembled contigs were annotated. Virulence genes, antimicrobial resistance genes (ARGs), tRNAs, rRNAs, coding sequences and clustered regularly interspaced short palindromic repeats (CRISPRs) were identified. ARGs and mutations in quinolone-resistance determining regions (QRDRs) were identified by Antimicrobial Resistance Identification By Assembly (ARIBA) and ResFinder. Known and unknow mutations in the QRDRs were predicted.

RESULTS

The genome of Salmonella Paratyphi A was calculated at 4529866 bp with 4381 genes and 1088 hypothetical proteins. Several putative genes coding for multidrug efflux pumps were identified. In addition, gene mutations conferring resistance to nitrofurantoin (e.g. marA, mdsC, Escherichia coli soxS), pulvomycin (e.g. H-NS, cpxA, E. coli EF-Tu) and fosfomycin (CRP, kdpE, E. coli glpT) were also identified. Several ARGs along with the mobile genetic element transposon Tn10 were also identified. It is evident from the results that diverse redundant mechanisms are involved in regulation of drug resistance in this strain.

CONCLUSION

The current findings provide valuable data for understanding the multidrug resistance and pathogenic characteristics of clinical Salmonella Paratyphi A isolates.

Salmonella osteomyelitis: A rare extraintestinal manifestation of an endemic pathogen

Salmonella enterica serovar Typhi and Paratyphi usually cause enteric fever in humans characterized by fever and gastrointestinal symptoms such as diarrhea. Bacteremia is a constant feature of enteric fever, and occasionally, dissemination of bacilli throughout the body results in the establishment of one or more localized foci of persisting infection. This happens especially in patients with preexisting conditions such as hemoglobinopathies, previous joint trauma, surgery, connective tissue diseases, lymphoma, diabetes, alcoholism, immunosuppressive state, and extremes of ages. Rarely, these extraintestinal Salmonella infection cases have also been reported in immunocompetent individuals without any obvious predisposing factors. Salmonella osteomyelitis, a rare sequelae of typhoid, may occur as a result of hematogenous seeding of the bone or joints due to a bacteremic episode. It may also spread from nearby areas of infection or penetrating trauma. Timely diagnosis and treatment of this condition are necessary because if left untreated, it can lead to permanent functional deficits later on. We hereby present a case series with brief review of literature on Salmonella osteomyelitis in immunocompetent patients without any known predisposing conditions over a period of 1 year (2017-2018) from a Tertiary Care Teaching Hospital in Uttarakhand, India.

Myositis associated with Salmonella paratyphi A bacteremia appears to be common

Background

Fever and severe myalgia in a tropical country like India bring to mind leptospirosis, rickettsioses, dengue, and other viral fevers. Enteric fever is widely prevalent in Asia, but myositis has not been previously described in Salmonella paratyphi A bacteremia.

Materials and Methods

Retrospectively, we recruited patients with enteric fever admitted to our treating unit over a 6-month period. Demography, historical, clinical, and laboratory data were obtained. Data of culture-positive S. paratyphi A patients were analyzed and were compared with those patients with culture-negative enteric fever.

Results

Forty-three cases were found in total with 19 of S. paratyphi A bacteremia. Elevations in creatine kinase (CK) ranged from one-and-half to six times normal. Forty-seven percent had thrombocytopenia and alanine transaminase elevations, while aspartate transaminase elevations were seen in 17 patients, which corresponded to those with elevated CK levels.

Conclusions

Myositis associated with S. typhi and S. paratyphi is very rare and is more often due to non-typhoidal Salmonellae. Elevated creatine kinase was seen in most of our patients with S. paratyphi A bacteremia. Such myositis has not been described previously and hence, myalgia with fever in a tropical country could be a harbinger of paratyphoid fever.

A cross-sectional study of enteric fever among febrile patients at Ambo hospital: prevalence, risk factors, comparison of Widal test and stool culture and antimicrobials susceptibility pattern of isolates

Background

Enteric fever is one of the common infectious diseases of humans. The objectives of this study were to:1) estimate the prevalence of enteric fever among febrile patients visiting Ambo hospital; 2) comparison of Widal test and stool culture;3) evaluation of the antimicrobial susceptibility of isolates; and 4) assess potential risk factors to acquire enteric fever infection.

Methods

Blood and stool samples were collected from 372 febrile patients with symptoms clinically similar to enteric fever. Widal test was used for testing sera while stool culturing and bacterial identification was done using WHO standard methods. Susceptibility testing was done using Kirby-Bauer disc diffusion method. Chi-Square test and Logistic Regression analysis were used to analyze the data.

Results

The apparent and true prevalence of enteric fever were 56.2% (95% confidence interval [CI]: 50.97–61.29%) and 57.52% (95% CI: 52.3–62.6%) respectively, while, the culture prevalence was 2.7% (95% CI: 1.30–4.89%). Isolation rates of S. Typhi and S. Paratyphi were 0.8% (95% CI: 0.17–2.34%) and 1.9% (95% CI: 0.76–3.84%) respectively. The isolates showed 100% resistance to amoxicillin, bacitracin, erythromycin, 80%resistance to cefotaxime and streptomycin and 20% for chloramphenicol. The sensitivity, specificity, positive and negative predictive values of Widal test was 80.0, 44.5, 3.8 and 98.8% respectively. Multivariable logistic regression analysis revealed that age (adjusted odds ratio [aOR] = 2.45; 95% CI: 1.38–4.37; P = 0.002), religion (aOR = 15.57, 95% CI: 3.01–80.64; P = 0.001), level of education (aOR = 2.60, 95% CI: 1.27–5.28; P = 0.009), source of water (aOR = 2.20, 95% CI: 1.21–3.98; P = 0.009), raw milk (aOR =2.19, 95% CI:1.16–4.16; P = 0.016) and raw meat consumption (aOR = 1.80, 95% CI: 1.07–3.01; P = 0.026) are the predictors of enteric fever seropositivity.

Conclusions

Patients were wrongly diagnosed and treated for enteric fever by Widal test. Therefore, rapid tests with better sensitivity and specificity are needed for the diagnosis of enteric fever. Provision of safe water and health education are vital to bring behavioral change towards raw food consumption.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3917-3) contains supplementary material, which is available to authorized users.

First report on antimicrobial resistance and molecular characterisation of Salmonella enterica serotype Typhi isolated from human specimens in Luanda, Angola

OBJECTIVES

Typhoid fever is a common infection in Africa and, despite scarce surveillance reports, its incidence is commonly considered high by the Angolan health system. Drug-resistant Salmonella enterica serotype Typhi has emerged, making antimicrobial susceptibility testing essential to provide clinical guidance. This is the first report analysing the antimicrobial resistance patterns and population structure of the few S. enterica ser. Typhi isolated from patients with typhoid fever in Luanda, Angola.

METHODS

Isolates were collected by the Angolan National Institute of Public Health between September 2013 and May 2014. Ten isolates were identified by the API 20E system and serotyping, and the genus was confirmed by PCR. All isolates were tested for antibiotic susceptibility, and the presence of resistance genes [bla_CTX-M, bla_SHV, bla_TEM, bla_OXA-1, several plasmid-borne genes encoding AmpC β-lactamases, sul and qnr genes, dfrIa, dfrA12, aac(6')-Ib, cmlA and floR] were screened by PCR. Isolates were typed by PFGE and MLST.

RESULTS

Several isolates were identified with resistance to trimethoprim/sulfamethoxazole (n=6), β-lactams (n=5) and chloramphenicol (n=1) and reduced susceptibility to ciprofloxacin (n=2). PFGE revealed eight closely related restriction patterns, and MLST grouped these into three sequence types (ST1, ST2 and ST8), with ST2 being predominant.

CONCLUSION

This first epidemiological report provides a preliminary description of S. enterica ser. Typhi strains circulating in Luanda and emphasises the need for continuous monitoring of this pathogen to provide information in order to implement better epidemiological strategies for the control of typhoid fever in Angola.

The impact of new national guidance for the public health management of enteric fever in England

OBJECTIVES

New guidance was published in England in February 2012 to support the public health management of enteric fever and reduce the risks of secondary transmission. The new guidance was evaluated to assess: STUDY DESIGN: Quantitative and qualitative evaluation of the implementation of new public health guidance.

METHODS

A qualitative review of all non-travel-related cases from February 2010 to January 2014 to compare the risk of secondary transmission before and after the guidance introduction; an audit of clearance sampling for each case and their contacts reported in London from February 2012-January 2015 to compare with a previous London audit; and an online user survey in November 2014.

RESULTS

The proportions of non-travel cases reported before and after the introduction of the new guidance were similar, 6% in 2010-2012 compared to 7% in 2012-2014 (P = 0.33). There was a 32% reduction in the number of clearance samples required for cases and the estimated period of exclusion from work or school was reduced from 54 days to 16 days. Compliance in case clearance improved from 53% to 90% and contact screening compliance improved from 42% to 80%. The targeted screening of contacts led to a significantly higher positive yield (3.6% from 1.5%, P = 0.003). All symptomatic co-travellers presented to a healthcare professional, suggesting that screening could be restricted to those in risk groups for transmission. Feedback from users highlighted additional areas, such as management of large organised groups of co-travellers and those diagnosed abroad, which has informed the update of the national guidance.

CONCLUSIONS

The new guidance has not led to an increase in secondary transmission of enteric fever in England and findings have been used to inform an update of the guidance. The new guidance also represents a reduced burden of investigation and thus a likely reduced cost to patients, healthcare professionals, laboratories and environmental health officers.