Typhoid fever

ANTIBIOTIC RESISTANCE OF SALMONELLA TYPHI CARRIER ASSOCIATED WITH GALL BLADDER CHRONIC INFECTION IN AL-NAJAF PROVINCE

OBJECTIVE

The aim: This study was undertaken to identify antibiotic resistance of Salmonella Typhi in specimens of gall bladder tissue after cholecystectomy.

PATIENTS AND METHODS

Materials and methods: Salmonella Typhi identification from the isolates have been depended on morphology of the colony and biochemical tests as a first step in identification while final identification has been achieved by the automated VITEK-2 compact system then PCR technique.

RESULTS

Results: Depending to finding via the VITEK tests and PCR technique and thirty-five Salmonella Typhi sample have been obtained. This research shown that about 35 (70%) positive result contains, 12 (34.3%) isolates was positive from stool and 23(65.7%) from gall bladder tissue. The results revealed difference in S. Typhi resistance to some antibiotics, where S. Typhi has wide-ranging sensitivity: 35 (100%) to Cefepime, Cefixime and Ciprofloxacin and revealed great sensitivity 22 (62.8%) to Ampicillin. S. Typhi isolates proved extremely resistant 19 (54.2%) and 25 (71.4%) to Trimethoprim/Sulphamethoxazole and Chloramphenicol respectively. Increment in the rate of Salmonella that has multidrug resistance to chloramphenicol, ampicillin, furazolidonecotrimoxazole, streptomycin, and tetracycline is a developing problem and worldwide worry matte.

CONCLUSION

Conclusions: Resistant forms of Salmonella enteric serotype Typhi were detected with increment in the rate of multidrug resistance to chloramphenicol, ampicillin, and tetracycline so currently, Cefepime, Cefixime and Ciprofloxacin and revealed great sensitivity and have become the mainstay of treatment. Challenging difficult which rises in this study is the extend of Multidrug resistant strain (MDR) of S. Typhi.

Mohammed A, Mohammed Flyyiah T. Whole-genome sequencing of Aminoglycoside nucleotidyltransferase aadA1 in patients with typhoid

S. typhi is causes typhoid in Iraq and developing countries. The abuse of antibiotics make the patient infected with S. typhi wich is resistant to many antibiotics. Aims of the study: Molecular and phylogenetic tree of genomic resistance genes associated Aminoglycoside nucleotidyltransferase (aad-A1), and detection mutation occur in aadA1 gene. Disc diffusion method and VITEK2 compact system to detect the resistance of S.typhi to 11 antibiotics and using the PCR technique to detect the prevalence of aadA1 resistance gene. The genomic DNA extracted from all S. typhi isolated harboring resistance gene. The prevalence of the aadA1 gene was 12(24%) from all S. typhi isolates and the presence of a silent mutation in sample number 2 Iraqi isolate. The first isolate (MW805237.1) was almost just like the isolates of each of the countries Korea, Iran Iran, India, and Madagascar, but The second Iraqi isolate (MW805238.1) was the share of congruence between them at 99% at position G. The aadA1 gene was present in S. typhi isolated from blood, the stool of human, and the detected mutation has no effect.

Affinity of cefotiam for the alternative penicillin binding protein PBP3SAL used by Salmonella inside host eukaryotic cells

BACKGROUND

Following the invasion of eukaryotic cells, Salmonella enterica serovar Typhimurium replaces PBP2/PBP3, main targets of β-lactam antibiotics, with PBP2SAL/PBP3SAL, two homologue peptidoglycan synthases absent in Escherichia coli. PBP3SAL promotes pathogen cell division in acidic environments independently of PBP3 and shows low affinity for β-lactams that bind to PBP3 such as aztreonam, cefepime, cefotaxime, ceftazidime, ceftriaxone, cefuroxime and cefalotin.

OBJECTIVES

To find compounds with high affinity for PBP3SAL to control Salmonella intracellular infections.

METHODS

An S. Typhimurium ΔPBP3 mutant that divides using PBP3SAL and its parental wild-type strain, were exposed to a library of 1520 approved drugs in acidified (pH 4.6) nutrient-rich LB medium. Changes in optical density associated with cell filamentation, a read-out of blockage in cell division, were monitored. Compounds causing filamentation in the ΔPBP3 mutant but not in wild-type strain-the latter strain expressing both PBP3 and PBP3SAL in LB pH 4.6-were selected for further study. The bactericidal effect due to PBP3SAL inhibition was evaluated in vitro using a bacterial infection model of cultured fibroblasts.

RESULTS

The cephalosporin cefotiam exhibited higher affinity for PBP3SAL than for PBP3 in bacteria growing in acidified LB pH 4.6 medium. Cefotiam also proved to be effective against intracellular Salmonella in a PBP3SAL-dependent manner. Conversely, cefuroxime, which has higher affinity for PBP3, showed decreased effectiveness in killing intracellular Salmonella.

CONCLUSIONS

Antibiotics with affinity for PBP3SAL, like the cephalosporin cefotiam, have therapeutic value for treating Salmonella intracellular infections.

Implementation of an outbreak response vaccination campaign with typhoid conjugate vaccine – Harare, Zimbabwe, 2019

Introduction

Typhoid fever is a public-health problem in Harare, the capital city of Zimbabwe, with seasonal outbreaks occurring annually since 2010. In 2019, the Ministry of Health and Child Care (MOHCC) organized the first typhoid conjugate vaccination campaign in Africa in response to a recurring typhoid outbreak in a large urban setting.

Method

As part of a larger public health response to a typhoid fever outbreak in Harare, Gavi approved in September 2018 a MOHCC request for 340,000 doses of recently prequalified Typbar-TCV to implement a mass vaccination campaign. To select areas for the campaign, typhoid fever surveillance data from January 2016 until June 2018 was reviewed. We collected and analyzed information from the MOHCC and its partners to describe the vaccination campaign planning, implementation, feasibility, administrative coverage and financial costs.

Results

The campaign was conducted in nine high-density suburbs of Harare over eight days in February–March 2019 and targeted all children aged 6 months–15 years; however, the target age range was extended up to 45 years in one suburb due to the past high attack rate among adults. A total of 318,698 people were vaccinated, resulting in overall administrative coverage of 85.4 percent. More than 750 community volunteers and personnel from the MOHCC and the Ministry of Education were trained and involved in social mobilization and vaccination activities. The MOHCC used a combination of vaccination strategies (i.e., fixed and mobile immunization sites, a creche and school-based strategy, and door-to-door activities). Financial costs were estimated at US$ 2.39 per dose, including the vaccine and vaccination supplies (US$ 0.79 operational costs per dose excluding vaccine and vaccination supplies).

Conclusion

A mass targeted campaign in densely populated urban areas in Harare, using the recently prequalified typhoid conjugate vaccine, was feasible and achieved a high overall coverage in a short period of time.

The evolutionary diversification of the Salmonella artAB toxin locus

Salmonella enterica is a diverse species of bacterial pathogens comprised of >2,500 serovars with variable host ranges and virulence properties. Accumulating evidence indicates that two AB₅-type toxins, typhoid toxin and ArtAB toxin, contribute to the more severe virulence properties of the Salmonella strains that encode them. It was recently discovered that there are two distinct types of artAB-like genetic elements in Salmonella: those that encode ArtAB toxins (artAB elements) and those in which the artA gene is degraded and the ArtB homolog, dubbed PltC, serves as an alternative delivery subunit for typhoid toxin (pltC elements). Here, we take a multifaceted approach to explore the evolutionary diversification of artAB-like genetic elements in Salmonella. We identify 7 subtypes of ArtAB toxins and 4 different PltC sequence groups that are distributed throughout the Salmonella genus. Both artAB and pltC are encoded within numerous diverse prophages, indicating a central role for phages in their evolutionary diversification. Genetic and structural analyses revealed features that distinguish pltC elements from artAB and identified evolutionary adaptations that enable PltC to efficiently engage typhoid toxin A subunits. For both pltC and artAB, we find that the sequences of the B subunits are especially variable, particularly amongst amino acid residues that fine tune the chemical environment of their glycan binding pockets. This study provides a framework to delineate the remarkably complex collection of Salmonella artAB/pltC-like genetic elements and provides a window into the mechanisms of evolution for AB₅-type toxins.

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

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Super Shedding in Enteric Pathogens: A Review

Super shedding occurs when a small number of individuals from a given host population shed high levels of a pathogen. Beyond this general definition, various interpretations of the shedding patterns have been proposed to identify super shedders, leading to the description of the super shedding phenomenon in a wide range of pathogens, in particular enteric pathogens, which are of considerable interest. Several underlying mechanisms may explain this observation, including factors related to the environment, the gut microbiota, the pathogen itself (i.e., genetic polymorphism), and the host (including immune factors). Moreover, data suggest that the interplay of these parameters, in particular at the host-pathogen-gut microbiota interface, is of crucial importance for the determination of the super shedding phenotype in enteric pathogens. As a phenomenon playing an important role in the epidemics of enteric diseases, the evidence of super shedding has highlighted the need to develop various control strategies.

Comparison of Single vs Combination Drug Therapy in Extensively Drug Resistant Salmonella typhi: An Observational Study from Pakistan

Introduction

Antibiotic resistance has become a significant problem in typhoid fever due to the emergence of extensively drug resistant (XDR) Salmonella enterica serovar typhi. In Pakistan, an outbreak of ceftriaxone-resistant typhoid was first reported in November 2016.

Methods

A retrospective chart review was conducted at Liaquat National Hospital and Medical University, in Karachi, Pakistan. Patient records were identified from the microbiology laboratory data of all admitted patients who had blood culture positive for XDR Salmonella typhi from January 2017 to December 2019.

Results

Out of 254 patients, 179 (70%) were male with an average age of 11.7 ± 10.9 years. Around 190 (74%) patients were treated with combination therapy, 126 (49%) were given azithromycin and meropenem and 61 (24%) received azithromycin and imipenem. A total of 64 (25%) patients received single drug therapy, 33 (12%) were given azithromycin, 23 (9%) meropenem, and 8 (3%) imipenem. Analysis indicated that single drug therapy resulted in an earlier onset of defervescence compared with combination therapy (5.03±2.98 days vs 3.45±2.48 days; P <0.001), with a decreased occurrence of pancytopenia (P <0.001).

Conclusion

Single antimicrobial therapy achieved defervescence earlier than combination therapy, with carbapenems performing better than azithromycin.

Understanding the Mechanism of Antimicrobial Resistance and Pathogenesis of Salmonella enterica Serovar Typhi

Salmonella enterica serovar Typhi (S. Typhi) is a Gram-negative pathogen that causes typhoid fever in humans. Though many serotypes of Salmonella spp. are capable of causing disease in both humans and animals alike, S. Typhi and S. Paratyphi are common in human hosts only. The global burden of typhoid fever is attributable to more than 27 million cases each year and approximately 200,000 deaths worldwide, with many regions such as Africa, South and Southeast Asia being the most affected in the world. The pathogen is able to cause disease in hosts by evading defense systems, adhesion to epithelial cells, and survival in host cells in the presence of several virulence factors, mediated by virulence plasmids and genes clustered in distinct regions known as Salmonella pathogenicity islands (SPIs). These factors, coupled with plasmid-mediated antimicrobial resistance genes, enable the bacterium to become resistant to various broad-spectrum antibiotics used in the treatment of typhoid fever and other infections caused by Salmonella spp. The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains in many countries of the world has raised great concern over the rise of antibiotic resistance in pathogens such as S. Typhi. In order to identify the key virulence factors involved in S. Typhi pathogenesis and infection, this review delves into various mechanisms of virulence, pathogenicity, and antimicrobial resistance to reinforce efficacious disease management.

Distribution of Ciprofloxacin- and Azithromycin-Resistant Genes among Salmonella Typhi Isolated from Human Blood

Context

Salmonella Typhi has developed resistance to different groups of antibiotics.

Aims

The purpose of the present study was to assess the distribution of ciprofloxacin- and azithromycin-resistant genes among Salmonella Typhi isolated from human blood.

Settings and Design

This cross-sectional study was conducted in the Department of Microbiology of a tertiary care hospital in Bangladesh from July 2019-June 2020.

Subjects and Methods

Clinically suspected enteric fever patients, irrespective of age and gender, who attended the laboratory of the Department of Microbiology and outpatient department of Medicine of tertiary care hospital. Blood culture and sensitivity tests were done. The positive growth of Salmonella Typhi was identified by Gram staining, colony morphology, and biochemical test. Then, Salmonella Typhi was identified by using Salmonella-specific antisera. Final identification was made by using 16s rRNA by polymerase chain reaction (PCR). PCR was also done to detect quinolone and azithromycin resistance genes.

Results

A total number of 83 samples yielded positive cultures, of which 50 isolated organisms were identified as Salmonella species; however, among these isolates, Salmonella Typhi was detected in 40 (48.2%) isolates. Among 12 ciprofloxacin-resistant isolates, 8 (66.67%) were positive for the gyrA gene, 1 (8.33%) was positive for the qnrB gene and qnrS gene, 2 (16.67%) were positive for aac (6´)-Ib-cr. Among 12 azithromycin-resistant isolates, 2 (16.66%) were positive for mphA and mefA genes, respectively.

Conclusion

In conclusion, the gyrA, aac (6´)-Ib-cr, mphA, and mefA genes are found for the first time in tertiary care hospitals from the quinolones and azithromycin-resistant Salmonella Typhi.

Concurrent Typhoid Fever and Dengue Hemorrhagic Fever: A Case Report

Dengue virus can co-infect with a number of viruses, bacteria, and parasites of which dengue malaria co-infection is most well-known. We report a rare case of dengue virus co-infection with typhoid fever and the development of dengue hemorrhagic fever (DHF) during a dengue outbreak. The second spike of high-grade fever following initial defervescence with antibiotic therapy, hemorrhagic manifestations, new onset leucopenia and thrombocytopenia, and evidence of plasma leakage raised suspicion of DHF. Diagnosis of dengue co-infection was made by seroconversion for anti-dengue immunoglobulin M (IgM) antibodies by enzyme-linked immunosorbent assay (ELISA) on the seventh day of new-onset fever. Early recognition and judicious use of fluid therapy prevented the patient from developing shock and its complications. Prompt diagnosis, early recognition of plasma leakage, and appropriate management of DHF can reduce morbidity and mortality.

Lipopolysaccharides and outer membrane proteins as main structures involved in complement evasion strategies of non-typhoidal Salmonella strains

Non-typhoidal Salmonella (NTS) infections pose a serious public health problem. In addition to the typical course of salmonellosis, an infection with Salmonella bacteria can often lead to parenteral infections and sepsis, which are particularly dangerous for children, the elderly and immunocompromised. Bacterial resistance to serum is a key virulence factor for the development of systemic infections. Salmonella, as an enterobacterial pathogen, has developed several mechanisms to escape and block the antibacterial effects of the complement system. In this review, we discuss the relevance of outer membrane polysaccharides to the complement evasion mechanisms of NTS strains. These include the influence of the overall length and density of the lipopolysaccharide molecules, modifications of the O-antigen lipopolysaccharide composition and the role of capsular polysaccharides in opsonization and protection of the outer membrane from the lytic action of complement. Additionally, we discuss specific outer membrane protein complement evasion mechanisms, such as recruitment of complement regulatory proteins, blocking assembly of late complement components to form the membrane attack complex and the proteolytic cleavage of complement proteins.

Clinical Characteristics and Antibiotics Sensitivity of Culture Positive Typhoid Fever Patients in Baghdad Teaching Hospital - A Single Center Study

BACKGROUND: Enteric fever caused by Salmonella Typhi is an endemic disease in Iraq. Variations in presentations make it a diagnostic challenge. If untreated or treated inappropriately then it is a serious disease with potentially life-threatening complications. The recent emergence of drug resistant strains of S. Typhi is a rising public health problem and a clinical concern to the physician. AIM: The objectives of the study were to assess and describe the patterns of antimicrobial resistance, clinical characteristics, epidemiological distribution, and complications of typhoid fever. PATIENTS AND METHODS: Fifty cases of typhoid fever (culture proven) were collected during the period from February 2019 to November 2019 in the medical wards of Baghdad Teaching Hospital. Detailed history, physical examination, and laboratory investigations were conducted and statistical analysis of the results was done, prospective observational study was conducted. RESULTS: During the study period, 50 cases of typhoid fever were documented, mean age of presentation was 30.7 ± 12.8, 60% of the cases were male gender, gastrointestinal complications were the most common (90%) followed by hematological complications (71%). Mortality of typhoid fever in our study was 2%. High percentage of resistance to third generation cephalosporins, ciprofloxacin, and azithromycin was found (96%, 56%, and 56%, respectively) while good sensitivity to trimethoprim and meropenem was found (94% and 76%, respectively). Significant association was also found between the development of typhoid fever complications and the presence of anemia, thrombocytopenia, lymphopenia, and eosinopenia. Significant association was also found between the complications and the infection with strains resistant to cephalosporins, ciprofloxacin, and azithromycin. CONCLUSIONS: There is a concerning increase in resistance toward cephalosporins, ciprofloxacin, and azithromycin while meropenem and trimethoprim are emerging as effective drugs. There was high incidence of complications found (84%).Lymphopenia, anemia, eosinopenia, and thrombocytopenia are independent risk factors for the development of complications of typhoid fever.

Outbreak of Typhoid Fever in Children of Urban Vellore: A Report from the Surveillance for Enteric Fever in India Cohort

We report an outbreak of typhoid fever between April and June 2019 in the Surveillance for Enteric Fever in India cohort, a pediatric cohort from four contiguous semi-urban settlements of Vellore in South India. This cohort of children 6 months to 15 years of age was under surveillance from October 2017 to December 2019. A clustering of typhoid cases in the cohort was noted with reference to time, place, and person. The overall typhoid attack rate in the cohort was 0.9%, with the highest attack rate of 1.7% being documented in one of the four areas. The rate of hospitalization and complications in children who were typhoid positive during the outbreak was 28% and 2%, respectively. Given the background of suboptimal water, sanitation, and hygiene, and the risk of typhoid fever outbreaks in these settings, it is imperative that a typhoid vaccine be considered for introduction as a pragmatic preventive approach.

Facility-based disease surveillance and Bayesian hierarchical modeling to estimate endemic typhoid fever incidence, Kilimanjaro Region, Tanzania, 2007–2018

Growing evidence suggests considerable variation in endemic typhoid fever incidence at some locations over time, yet few settings have multi-year incidence estimates to inform typhoid control measures. We sought to describe a decade of typhoid fever incidence in the Kilimanjaro Region of Tanzania. Cases of blood culture confirmed typhoid were identified among febrile patients at two sentinel hospitals during three study periods: 2007–08, 2011–14, and 2016–18. To account for under-ascertainment at sentinel facilities, we derived adjustment multipliers from healthcare utilization surveys done in the hospital catchment area. Incidence estimates and credible intervals (CrI) were derived using a Bayesian hierarchical incidence model that incorporated uncertainty of our observed typhoid fever prevalence, of healthcare seeking adjustment multipliers, and of blood culture diagnostic sensitivity. Among 3,556 total participants, 50 typhoid fever cases were identified. Of typhoid cases, 26 (52%) were male and the median (range) age was 22 (<1–60) years; 4 (8%) were aged <5 years and 10 (20%) were aged 5 to 14 years. Annual typhoid fever incidence was estimated as 61.5 (95% CrI 14.9–181.9), 6.5 (95% CrI 1.4–20.4), and 4.0 (95% CrI 0.6–13.9) per 100,000 persons in 2007–08, 2011–14, and 2016–18, respectively. There were no deaths among typhoid cases. We estimated moderate typhoid incidence (≥10 per 100 000) in 2007–08 and low (<10 per 100 000) incidence during later surveillance periods, but with overlapping credible intervals across study periods. Although consistent with falling typhoid incidence, we interpret this as showing substantial variation over the study periods. Given potential variation, multi-year surveillance may be warranted in locations making decisions about typhoid conjugate vaccine introduction and other control measures.

There is evidence that typhoid fever incidence may vary over time, but there are few longitudinal studies estimating incidence. This is especially true in Sub-Saharan Africa, where recent estimates show wide variation in incidence across different settings, but very limited longitudinal descriptions from those settings. Incidence estimates were generated using facility-based surveillance data from three study periods that was adjusted for health-seeking behavior established through healthcare utilization surveys performed in the catchment area. In addition to coupling facility-based surveillance data with healthcare utilization data, we utilized a Bayesian statistical methodology in order to estimate incidence and characterize uncertainty around the estimates. Our results demonstrate moderate typhoid incidence in 2007–08 and low incidence during 2012–14 and 2016–18, but with overlapping credible intervals across study periods. Our data are consistent with evidence that endemic typhoid may vary substantially over time. Given potential variation, multi-year surveillance may be warranted in locations making decisions about typhoid conjugate vaccine introduction and other control measures.

Genomic epidemiology of Salmonella Typhi in Central Division, Fiji, 2012 to 2016

BACKGROUND

Typhoid fever is endemic in some Pacific Island Countries including Fiji and Samoa yet genomic surveillance is not routine in such settings. Previous studies suggested imports of the global H58 clade of Salmonella enterica var Typhi (Salmonella Typhi) contribute to disease in these countries which, given the MDR potential of H58, does not auger well for treatment. The objective of the study was to define the genomic epidemiology of Salmonella Typhi in Fiji.

METHODS

Genomic sequencing approaches were implemented to study the distribution of 255 Salmonella Typhi isolates from the Central Division of Fiji. We augmented epidemiological surveillance and Bayesian phylogenomic approaches with a multi-year typhoid case-control study to define geospatial patterns among typhoid cases.

FINDINGS

Genomic analyses showed Salmonella Typhi from Fiji resolved into 2 non-H58 genotypes with isolates from the two dominant ethnic groups, the Indigenous (iTaukei) and non-iTaukei genetically indistinguishable. Low rates of international importation of clones was observed and overall, there were very low levels an antibiotic resistance within the endemic Fijian typhoid genotypes. Genomic epidemiological investigations were able to identify previously unlinked case clusters. Bayesian phylodynamic analyses suggested that genomic variation within the larger endemic Salmonella Typhi genotype expanded at discreet times, then contracted.

INTERPRETATION

Cyclones and flooding drove 'waves' of typhoid outbreaks in Fiji which, through population aggregation, poor sanitation and water safety, and then mobility of the population, spread clones more widely. Minimal international importations of new typhoid clones suggest that targeted local intervention strategies may be useful in controlling endemic typhoid infection. These findings add to our understanding of typhoid transmission networks in an endemic island country with broad implications, particularly across Pacific Island Countries.

FUNDING

This work was supported by the Coalition Against Typhoid through the Bill and Melinda Gates Foundation [grant number OPP1017518], the Victorian Government, the National Health and Medical Research Council Australia, the Australian Research Council, and the Fiji Ministry of Health and Medical Services.

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.

The CRISPR-Cas System Differentially Regulates Surface-Attached and Pellicle Biofilm in Salmonella enterica Serovar Typhimurium

The CRISPR-Cas mediated regulation of biofilm by Salmonella enterica serovar Typhimurium was investigated by deleting CRISPR-Cas components ΔcrisprI, ΔcrisprII, ΔΔcrisprI crisprII, and Δcas op. We determined that the system positively regulates surface biofilm while inhibiting pellicle biofilm formation. Results of real-time PCR suggest that the flagellar (fliC, flgK) and curli (csgA) genes were repressed in knockout strains, causing reduced surface biofilm. The mutants displayed altered pellicle biofilm architecture. They exhibited bacterial multilayers and a denser extracellular matrix with enhanced cellulose and less curli, ergo weaker pellicles than those of the wild type. The cellulose secretion was more in the knockout strains due to the upregulation of bcsC, which is necessary for cellulose export. We hypothesized that the secreted cellulose quickly integrates into the pellicle, leading to enhanced pellicular cellulose in the knockout strains. We determined that crp is upregulated in the knockout strains, thereby inhibiting the expression of csgD and, hence, also of csgA and bcsA. The conflicting upregulation of bcsC, the last gene of the bcsABZC operon, could be caused by independent regulation by the CRISPR-Cas system owing to a partial match between the CRISPR spacers and bcsC gene. The cAMP-regulated protein (CRP)-mediated regulation of the flagellar genes in the knockout strains was probably circumvented through the regulation of yddx governing the availability of the sigma factor σ²⁸ that further regulates class 3 flagellar genes (fliC, fljB, and flgK). Additionally, the variations in the lipopolysaccharide (LPS) profile and expression of LPS-related genes (rfaC, rfbG, and rfbI) in knockout strains could also contribute to the altered pellicle architecture. Collectively, we establish that the CRISPR-Cas system differentially regulates the formation of surface-attached and pellicle biofilm.

IMPORTANCE In addition to being implicated in bacterial immunity and genome editing, the CRISPR-Cas system has recently been demonstrated to regulate endogenous gene expression and biofilm formation. While the function of individual cas genes in controlling Salmonella biofilm has been explored, the regulatory role of CRISPR arrays in biofilm is less studied. Moreover, studies have focused on the effects of the CRISPR-Cas system on surface-associated biofilms, and comprehensive studies on the impact of the system on pellicle biofilm remain an unexplored niche. We demonstrate that the CRISPR array and cas genes modulate the expression of various biofilm genes in Salmonella, whereby surface and pellicle biofilm formation is distinctively regulated.

Salmonella enterica subsp. II serovar 4,5,12:a:- may cause gastroenteritis infections in humans

Some serovars of Salmonella are not or rare found to cause salmonellosis in human. In our clinic-based surveillance, three rare Salmonella 4,5,12:a:- strains were recovered from three patients with diarrhea. To explore their genetic and epidemiological characteristics and pathogenesis, we conducted whole-genome sequencing, in vitro invasion assays in mammalian cells, and in vivo virulence assays in an animal model. The three isolates had indistinguishable molecular patterns and similar genome sequences, and clustered together with an isolate from edible fish traded among countries. The isolates had biochemical reactions identical with those of Salmonella subspecies enterica but belonged to subspecies salamae according to genome phylogeny, revealing a new serovar, S. enterica subsp. II serovar 4,5,12:a:-. The strains contained multiple virulence genes, elicited temporary bacteremia and enteritidis and caused cell damage in the mouse liver and cecum. This study provides evidence that this new Salmonella salamae serovar can infect humans and cause clusters of cases, and whole-genome sequencing detection and surveillance of Salmonella can help to accurately define Salmonella classification and clonality, improve diagnosis, facilitate outbreak detection and aid in the source tracing of salmonellosis epidemics.

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

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

Typhoid toxin sorting and exocytic transport from Salmonella Typhi-infected cells

Typhoid toxin is an essential virulence factor for Salmonella Typhi, the cause of typhoid fever in humans. This toxin has an unusual biology in that it is produced by Salmonella Typhi only when located within host cells. Once synthesized, the toxin is secreted to the lumen of the Salmonella-containing vacuole from where it is transported to the extracellular space by vesicle carrier intermediates. Here, we report the identification of the typhoid toxin sorting receptor and components of the cellular machinery that packages the toxin into vesicle carriers, and exports it to the extracellular space. We found that the cation-independent mannose-6-phosphate receptor serves as typhoid toxin sorting receptor and that the coat protein COPII and the GTPase Sar1 mediate its packaging into vesicle carriers. Formation of the typhoid toxin carriers requires the specific environment of the Salmonella Typhi-containing vacuole, which is determined by the activities of specific effectors of its type III protein secretion systems. We also found that Rab11B and its interacting protein Rip11 control the intracellular transport of the typhoid toxin carriers, and the SNARE proteins VAMP7, SNAP23, and Syntaxin 4 their fusion to the plasma membrane. Typhoid toxin's cooption of specific cellular machinery for its transport to the extracellular space illustrates the remarkable adaptation of an exotoxin to exert its function in the context of an intracellular pathogen.

Identification of a Host-Targeted Compound to Control Typhoid Fever

Typhoid fever is caused primarily by the enteric microbe Salmonella enterica serovar Typhi and remains a major global health problem with approximately 14 million new infections and 136,000 fatalities annually. While there are antibiotic options available to treat the disease, the global increase in multidrug-resistant strains necessitates alternative therapeutic options. Host-targeted therapeutics present a promising anti-infective strategy against intracellular bacterial pathogens. A cell-based assay identified a compound that inhibits Salmonella proliferation in infected cells, 2-(3-hydroxypropyl)-1-(3-phenoxyphenyl)-1,2-dihydrochromeno[2,3-c]pyrrole-3,9-dione (KH-1), which is devoid of direct activity against Salmonella. The compound inhibits the growth of both antibiotic-sensitive and -resistant Salmonella strains inside macrophages and reduces lactate dehydrogenase (LDH) release from Salmonella-infected cells. Subsequent screening of KH-1 commercial analogs identified 2-(4-fluorobenzyl)-1-(3-phenoxyphenyl)-1,2-dihydrochromeno[2,3-c] pyrrole-3,9-dione (KH-1-2), which is more effective in controlling Salmonella growth inside macrophages. In vitro KH-1-2 treatment of Salmonella infection resulted in an 8- to 10-fold reduction in bacterial load in infected macrophages. In combination with suboptimal ciprofloxacin treatment, KH-1-2 further reduces Salmonella growth inside macrophages. The toxicity and efficacy of KH-1-2 in controlling Salmonella infection were examined in vivo using a mouse model of typhoid fever. No significant compound-related clinical signs and histological findings of the liver, spleen, or kidney were observed from uninfected mice that were intraperitoneally treated with KH-1-2. KH-1-2 significantly protected mice from a lethal dose of infection by an antibiotic-resistant Salmonella strain. Thus, our study provides support that this is a promising lead compound for the development of a novel host-targeted therapeutic agent to control typhoid fever.

IMPORTANCESalmonella spp. cause significant morbidity and mortality worldwide. Typhoidal spp. (e.g., S. Typhi) cause a systemic disease typically treated with antibiotics. However, growing antibiotic resistance is resulting in increased treatment failures. We screened a compound library for those that would reduce Salmonella-induced macrophage toxicity, identifying compound KH-1. KH-1 has no direct effects on the bacteria but limits Salmonella survival in macrophages and protects against lethal infection in a mouse model of typhoid fever. A suboptimal concentration of ciprofloxacin worked in conjunction with the compound to further decrease Salmonella survival in macrophages. An analog (KH-1-2) was identified that possessed increased activity in vitro in macrophages and in vivo against both antibiotic-sensitive and -resistant strains. Thus, we report the identification of a lead compound that may be a useful scaffold as a host-directed antimicrobial against typhoid fever.

Typhoid in Pakistan: Challenges, Efforts, and Recommendations

Typhoid, and its extra drug resistant form which is highly prevalent Pakistan, is increasing the burden on healthcare through multiple factors. These range from lack of sanitation, the collapsing economy, and poor access to clean drinking water which have made it arduous for the government and various other organizations in containing it. With the COVID-19 pandemic, treatment of typhoid became a challenge as focus was driven towards limiting the COVID-19 spread, and hence preferential use of antibiotics such as azithromycin may limit future empirical antibiotic therapy for typhoid. Socioeconomic disparities and geographical as well as demographic barriers further limit access to appropriate typhoid management. Lastly, illiteracy and self-medication with antibiotics may predispose Pakistan to another outbreak of typhoid. These concerns, although largely unaddressed effectively, need immediate action. Previously, the government and international organizations have made efforts to control the spread through the introduction of TCV as a part of EPI and awareness, additional improvements are needed. These include: improving access to telemedicine in rural areas, extensive vaccination programs, and routine awareness programs especially in schools.

Repurposing of FDA approved drugs against Salmonella enteric serovar Typhi by targeting dihydrofolate reductase: an in silico study

Drug-resistant Salmonella enteric serovar Typhi (S. Typhi) poses a vital public health issue. To overcome drug resistance issues, the development of effective drugs with novel mechanism(s) of action is required. In this regard, drug repurposing is a viable alternative approach to find novel drugs to overcome drug resistance. Therefore, a FDA-approved-drug-library containing 1930 drugs was analyzed against the dihydrofolate reductase (DHFR) of S. Typhi using deep learning regression algorithms. Initially, a total of 500 compounds were screened, followed by rescreening by molecular docking. Further, from screened compounds by molecular docking, the top eight compounds were subjected to molecular dynamics (MD) simulation. Analysis of MD simulation resulted in four potential compounds, namely; Duvelisib, Amenamevir, Lifitegrast and Nilotinib against the DHFR enzyme. During the MD simulation, these four drugs achieved good stability during the 100 ns trajectory period at 300 K. Further to know the insights of the complex's stability, we calculated RMSF, RG, SASA and interaction energy for the last 60 ns trajectory period because all complexes showed the stability after 40 ns trajectory period. MM-PBSA analysis of the last 10 ns of MD trajectories showed the stability of the complexes. From our results, we conclude that these drugs can also be useful for treating typhoid fever and can inhibit S. Typhi by interfering with the function of the DHFR enzyme. Communicated by Ramaswamy H. Sarma.

HEPATIC DYSFUNCTION IN MEDICAL INTENSIVE CAREUNIT PATIENTS PREDICTS POOR OUTCOME

BACKGROUND

A large number of patients admitted to the medical intensive care unit (MICU) have abnormal liver function tests (LFT). This includes patients with critical illness with or without preexisting liver disease and patients with acute primary liver injury. There are very few studies which have investigated the spectrum of liver disease, clinical profile and outcome in patients admitted to the MICU.

OBJECTIVE

To evaluate the occurrence, etiology, clinical profile, laboratory profile and outcome of hepatic dysfunction in patients admitted to the MICU. To evaluate the utility of model for end-stage liver disease (MELD) score on admission as a predictor of adverse short term outcome in patients with hepatic dysfunction admitted in MICU.

METHODS

It was a prospective observational study, conducted from December 2017 to December 2018 in a tertiary care hospital. Two hundred and two patients admitted to the MICU with LFTs as per the inclusion criteria were analyzed and their short-term outcome at 7 days was studied in relation to various parameters.

RESULTS

LFT abnormalities were present in 202/1126 (17.9%) of the patients admitted to MICU. Critical illness associated liver dysfunction was found in 172 (85.2%) patients, chronic liver disease in 11 (5.4%) patients and acute viral hepatitis in 19 (9.4%) patients. Most common symptom was fever (68.3%) followed by vomiting (48.0%). Among LFT abnormalities, elevated transaminases, raised international normalized ratio and high MELD score on admission correlated with poor short-term outcome. Requirement for inotropes and mechanical ventilation correlated with poor short-term outcome. Mortality did not differ significantly between patients with chronic liver disease, patients with acute viral hepatitis and patients with critical illness associated hepatic dysfunction. Hepatic dysfunction in MICU was associated with poor outcome and a high short-term mortality of 56.4% (114/202).

CONCLUSION

Liver function abnormality is common in patients who are admitted to the MICU and its presence is an indicator of poor short-term outcome.

Toward Typhoid Fever Elimination

Salmonella enterica serotype Typhi (S Typhi) causes typhoid fever and is responsible for an estimated 9 million cases and 110,000 deaths globally per annum. Typhoid fever is endemic in areas where water, sanitation, and hygiene (WaSH) infrastructure is poor. Serious complications develop in approximately 10%-15% of patients if left untreated, and this is driven by inadequate diagnostic methods and the high burden of antibiotic-resistant strains, complicating clinical management and ultimately prognosis. Asymptomatic chronic carriers, in addition to acutely infected patients, contribute to continued transmission through the shedding of the organism in the feces. The high morbidity and mortality of typhoid fever in low- and middle-income countries reinforce the need for an integrated control approach, which may ultimately lead to elimination of the disease in the 21^st century. Here we discuss the challenges faced in pursuit of typhoid fever elimination.

Typhoid fever presenting with gastric ulcer bleeding

Background

Enteric fever is a systemic disease caused by Salmonella enterica serovar Typhi or Salmonella enterica serovar Paratyphi, characterized by high fever and abdominal pain. Most patients with enteric fever improve within a few days after antibiotic treatment. However, some patients do not recover as easily and develop fatal life-threatening complications, including intestinal hemorrhage. Lower gastrointestinal bleeding has been reported in 10% of cases. However, upper gastrointestinal bleeding has rarely been reported in patients with enteric fever. We present a case of gastric ulcer hemorrhage caused by enteric fever.

Case presentation

A 32-year-old woman, complaining of fever lasting four days and right upper quadrant pain and melena that started one day before admission, consulted our hospital. Abdominal computed tomography revealed mild hepatomegaly and gastroscopy revealed multiple active gastric ulcers with flat black hemorrhagic spots. The melena of the patient stopped on the third day. On the fifth admission day, she developed hematochezia. At that time, Salmonella enterica serovar Typhi was isolated from the blood culture. The antibiotic regimen was switched to ceftriaxone. Her hematochezia spontaneously resolved the following day. Finally, the patient was discharged on the 12th admission day without clinical symptoms. However, her fever recurred one month after discharge, and she was readmitted and Salmonella enterica serovar Typhi was confirmed again via blood culture. She was treated with ceftriaxone for one month, and was discharged without complications.

Conclusion

Our case showed that although rare, active gastric ulcers can develop in patients with enteric fever. Therefore, upper and lower gastrointestinal bleeding should be suspected in patients with enteric fever, especially showing relapsing bacteremia.

Whole genome sequence analysis of Salmonella Typhi in Papua New Guinea reveals an established population of genotype 2.1.7 sensitive to antimicrobials

BACKGROUND

Typhoid fever, a systemic infection caused by Salmonella enterica serovar Typhi, remains a considerable public health threat in impoverished regions within many low- and middle-income settings. However, we still lack a detailed understanding of the emergence, population structure, molecular mechanisms of antimicrobial resistance (AMR), and transmission dynamics of S. Typhi across many settings, particularly throughout the Asia-Pacific islands. Here we present a comprehensive whole genome sequence (WGS) based overview of S. Typhi populations circulating in Papua New Guinea (PNG) over 30 years.

PRINCIPLE FINDINGS

Bioinformatic analysis of 86 S. Typhi isolates collected between 1980-2010 demonstrated that the population structure of PNG is dominated by a single genotype (2.1.7) that appears to have emerged in the Indonesian archipelago in the mid-twentieth century with minimal evidence of inter-country transmission. Genotypic and phenotypic data demonstrated that the PNG S. Typhi population appears to be susceptible to former first line drugs for treating typhoid fever (chloramphenicol, ampicillin and co-trimoxazole), as well as fluoroquinolones, third generation cephalosporins, and macrolides. PNG genotype 2.1.7 was genetically conserved, with very few deletions, and no evidence of plasmid or prophage acquisition. Genetic variation among this population was attributed to either single point mutations, or homologous recombination adjacent to repetitive ribosomal RNA operons.

SIGNIFICANCE

Antimicrobials remain an effective option for the treatment of typhoid fever in PNG, along with other intervention strategies including improvements to water, sanitation and hygiene (WaSH) related infrastructure and potentially the introduction of Vi-conjugate vaccines. However, continued genomic surveillance is warranted to monitor for the emergence of AMR within local populations, or the introduction of AMR associated genotypes of S. Typhi in this setting.

The Burden of Typhoid Fever in Sub-Saharan Africa: A Perspective

While typhoid fever has largely been eliminated in high-income regions which have developed modern water, sanitation, and hygiene facilities, it remains a significant public health burden resulting in morbidity and mortality among millions of individuals in resource-constrained settings. Prevention and control efforts are needed that integrate several high-impact interventions targeting facilities and infrastructure, including those addressing improvements in sanitation, access to safe water, and planned urbanization, together with parallel efforts directed at effective strategies for use of typhoid conjugate vaccines (TCV). The use of TCVs is a critical tool with the potential of having a rapid impact on typhoid fever disease burden; their introduction will also serve as an important strategy to combat evolving antimicrobial resistance to currently available typhoid fever treatments. Well-designed epidemiological surveillance studies play a critical role in establishing the need for, and monitoring the impact of, typhoid fever control and prevention strategies implemented by public health authorities. Here, we present a perspective based on a narrative review of the impact of typhoid fever on morbidity and mortality in sub-Saharan Africa and discuss ongoing surveillance activities and the role of vaccination in prevention and control efforts.

Bacterial infection disrupts established germinal center reactions through monocyte recruitment and impaired metabolic adaptation

Consecutive exposures to different pathogens are highly prevalent and often alter the host immune response. However, it remains unknown how a secondary bacterial infection affects an ongoing adaptive immune response elicited against primary invading pathogens. We demonstrated that recruitment of Sca-1⁺ monocytes into lymphoid organs during Salmonella Typhimurium (STm) infection disrupted pre-existing germinal center (GC) reactions. GC responses induced by influenza, plasmodium, or commensals deteriorated following STm infection. GC disruption was independent of the direct bacterial interactions with B cells and instead was induced through recruitment of CCR2-dependent Sca-1⁺ monocytes into the lymphoid organs. GC collapse was associated with impaired cellular respiration and was dependent on TNFα and IFNγ, the latter of which was essential for Sca-1⁺ monocyte differentiation. Monocyte recruitment and GC disruption also occurred during LPS-supplemented vaccination and Listeria monocytogenes infection. Thus, systemic activation of the innate immune response upon severe bacterial infection is induced at the expense of antibody-mediated immunity.

Cooperative defenses during enteropathogenic infection

During their co-evolution with pathogens, hosts acquired defensive health strategies that allow them to maintain their health or promote recovery when challenged with infections. The cooperative defense system is a largely unexplored branch of these evolved defense strategies. Cooperative defenses limit physiological damage and promote health without having a negative impact on a pathogen's ability to survive and replicate within the host. Here, we review recent discoveries in the new field of cooperative defenses using the model pathogens Citrobacter rodentium and Salmonella enterica. We discuss not only host-encoded but also pathogen-encoded mechanisms of cooperative defenses. Cooperative defenses remain an untapped resource in clinical medicine. With a global pandemic exacerbated by a lack of vaccine access and a worldwide rise in antibiotic resistance, the study of cooperative defenses offers an opportunity to safeguard health in the face of pathogenic infection.

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.

An observational study to compare the diagnostic accuracy of rapid antigen test and rapid antibody tests in various periods of enteric fever

A cross-sectional observational study was done on 180 fever patients to assess the diagnostic accuracy of rapid serological tests in early detection (<5 days of fever) of S. typhi and S. paratyphi in comparison to blood culture and Widal test Blood culture was positive in 58 (32.22%) cases. The diagnostic accuracy (<5 days of fever) of rapid antigen test, rapid antibody test, and Widal test was 45.56%, 42.22%, and 41.11% (p = 0.675) while sensitivity was 68.97%, 48.28%, and 46.55%, respectively. In conclusion, rapid antigen test holds moderately higher sensitivity in the first five days of fever as compared to rapid antibody and Widal tests. It is recommended that the antigen detection tests should be used for screening enteric fever in the first week of presentation.

British Infection Association Guidelines for the Diagnosis and Management of Enteric Fever in England

Enteric fever (EF) is an infection caused by the bacteria called Salmonella Typhi or Paratyphi. Infection is acquired through swallowing contaminated food or water. Most EF in England occurs in people returning from South Asia and other places where EF is common; catching EF in England is rare. The main symptom is fever, but stomach pain, diarrhoea, muscle aches, rash and other symptoms may occur. EF is diagnosed by culturing the bacteria from blood and/or stool in a microbiology laboratory. EF usually responds well to antibiotic treatment. Depending on how unwell the individual is, antibiotics may be administered by mouth or by injection. Over the past several years, there has been an overall increase in resistance to antibiotics used to treat enteric fever, in all endemic areas. Additionally, since 2016, there has been an ongoing outbreak of drug-resistant EF in Pakistan. This infection is called extensively drug-resistant, or XDR, EF and only responds to a limited number of antibiotics. Occasionally individuals develop complications of EF including confusion, bleeding, a hole in the gut or an infection of the bones or elsewhere. Some people may continue to carry the bacteria in their stool for a longtime following treatment for the initial illness. These people may need treatment with a longer course of antibiotics to eradicate infection. Travellers can reduce their risk of acquiring EF by following safe food and water practices and by receiving the vaccine at least a few weeks before travel. These guidelines aim to help doctors do the correct tests and treat patients for enteric fever in England but may also be useful to doctors and public health professionals in other similar countries.

Typhoid Fever and Helminth Coinfection: A Pediatric Case Report

Enteric fever and helminth infestation coinfection is commonly seen among children below the age of 5, living in areas with poor sanitation in Africa. These can be explained due to the fact that both enteric fever and ascariasis, are contracted via fecal-oral routes. Although the immune system of children is presumed to be stronger and capable of eliminating several infectious agents, it is not applicable to children below the age of 5. Balanced nutrition also plays a vital role in sustaining strong immunity in children of all age groups and so, it could be one of the contributing factors to high susceptibility to co-infectious diseases among children living in poor countries. Soil-transmitted helminths (STH) are very common in developing countries. They are caused by infection with roundworm, hookworm, or whipworm. Both typhoid fever and helminth infestation in children presents with almost similar clinical symptoms. We present a case of coinfection with typhoid fever caused by Salmonella typhi bacteria and helminth in a 4-year-old child from Nigeria.

Antimicrobial-resistant foodborne pathogens in the Middle East: a systematic review

Foodborne pathogens are known as significant public health hazards worldwide, particularly in the Middle East region. Antimicrobial resistance (AMR) among foodborne pathogens becomes one of the top challenges for the environment, public health, and food safety sectors. However, less is known about antimicrobial-resistant foodborne pathogens in the Middle East region. Possibly because of the lack of surveillance, documentation, and reporting. This review focuses on the current status of antimicrobial resistance profiling among foodborne pathogens in the Middle East. Therefore, PubMed and other relevant databases were searched following PRISMA guidelines. Subject heading and texts were searched for "antimicrobial resistances," "foodborne," and "Middle East" to identify observational studies on AMR foodborne pathogens published during the last 10 years (2011 to 2020). Article retrieval and screening were done using a structured search string and strict inclusion/exclusion criteria. Median and interquartile ranges of percent resistance were calculated for each antibiotic-bacterium combination. A total of 249 articles were included in the final analysis from ten countries, where only five countries had more than 85% of the included articles. The most commonly reported pathogens were Escherichia coli, Salmonella spp. Staphylococcus aureus, and Listeria spp. An apparent rise in drug resistance among foodborne pathogens was recorded particularly against amoxicillin-clavulanic acid, ampicillin, nalidixic acid, streptomycin, and tetracycline that are commonly prescribed in most countries in the Middle East. Besides, there is a lack of standardization and quality control for microbiological identification and susceptibility testing methods in many of the Middle East countries.

Eyedrop vaccination: an immunization route with promises for effective responses to pandemics

INTRODUCTION

Mucosal vaccines have several advantages over parenteral vaccines. They induce both systemic and mucosal antigen-specific immune responses, allow easy administration, and bypass the need for trained medical personnel.

AREAS COVERED

Eye mucosa is a novel route of mucosal vaccine administration. Eyedrop vaccination induces systemic and mucosal immune responses similar to other forms of mucosal vaccines such as oral and intranasal vaccines.

EXPERT OPINION

Eyedrop vaccines are free of serious adverse side effects like the infiltration of CNS by pathogens. Studies over the years have shown promising results for eye drop vaccines against infectious agents like the influenza virus, Salmonella typhi, and Escherichia coli in animal models. Such efficacy and safety of eyedrop vaccination enable the application of eyedrop vaccines against other infectious diseases as well as chronic diseases. In this review of published literature, we examine the mechanism, efficacy, and safety of eyedrop vaccines and contemplate their role in times of a pandemic.

Salmonella Typhi Shedding and Household Transmission by Children With Blood Culture-Confirmed Typhoid Fever in Vellore, South India

BACKGROUND

Children suffer the highest burden of the typhoid fever, with a considerable proportion shedding Salmonella Typhi in stool, potentially resulting in transmission of S Typhi.

METHODS

We enrolled 70 children with blood culture-confirmed typhoid fever (index cases), from 63 households, during community-based fever surveillance in India. The index cases and their household contacts were followed up with stool samples at multiple time points over 3 weeks and 1 week, respectively. S Typhi was detected using quantitative real-time polymerase chain reaction.

RESULTS

Fifteen of 70 (21.4%) children with culture-confirmed typhoid fever shed S Typhi in stool after onset of fever. Ten of 15 children shed S Typhi for a median of 11.5 (range, 3-61) days from the day of completion of antibiotics. Of 172 household contacts from 56 of the 63 index case households, 12 (7%) contacts in 11 (19.6%) households had S Typhi in stool. Five of the 12 contacts who were shedding S Typhi were asymptomatic, whereas 7 reported recent fever.

CONCLUSIONS

One in 5 children with typhoid fever shed S Typhi, with shedding persisting even after antibiotics. One in 5 households had at least 1 contact of the child shedding S Typhi, highlighting potential concurrent typhoid infections in households in settings with poor water and sanitation.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A Bayesian approach for estimating typhoid fever incidence from large-scale facility-based passive surveillance data

Decisions about typhoid fever prevention and control are based on estimates of typhoid incidence and their uncertainty. Lack of specific clinical diagnostic criteria, poorly sensitive diagnostic tests, and scarcity of accurate and complete datasets contribute to difficulties in calculating age‐specific population‐level typhoid incidence. Using data from the Strategic Typhoid Alliance across Africa and Asia program, we integrated demographic censuses, healthcare utilization surveys, facility‐based surveillance, and serological surveillance from Malawi, Nepal, and Bangladesh to account for under‐detection of cases. We developed a Bayesian approach that adjusts the count of reported blood‐culture‐positive cases for blood culture detection, blood culture collection, and healthcare seeking—and how these factors vary by age—while combining information from prior published studies. We validated the model using simulated data. The ratio of observed to adjusted incidence rates was 7.7 (95% credible interval [CrI]: 6.0‐12.4) in Malawi, 14.4 (95% CrI: 9.3‐24.9) in Nepal, and 7.0 (95% CrI: 5.6‐9.2) in Bangladesh. The probability of blood culture collection led to the largest adjustment in Malawi, while the probability of seeking healthcare contributed the most in Nepal and Bangladesh; adjustment factors varied by age. Adjusted incidence rates were within or below the seroincidence rate limits of typhoid infection. Estimates of blood‐culture‐confirmed typhoid fever without these adjustments results in considerable underestimation of the true incidence of typhoid fever. Our approach allows each phase of the reporting process to be synthesized to estimate the adjusted incidence of typhoid fever while correctly characterizing uncertainty, which can inform decision‐making for typhoid prevention and control.

Prevalence, probability, and outcomes of typhoidal/non-typhoidal Salmonella and malaria co-infection among febrile patients: a systematic review and meta-analysis

The geographical overlaps of malaria parasites and Salmonella spp. can lead to co-infection of these two pathogens, especially in the tropics where malaria is endemic. Moreover, few literatures suggested that malaria infection was associated with Salmonella bacteremia. Therefore, this study quantified pooled prevalence of typhoidal/non-typhoidal Salmonella (NTS) and probability of typhoidal/NTS and malaria co-infection among febrile patients. The systematic review protocol was registered at PROSPERO (CRD42021252322). Studies on co-infection of typhoidal/NTS and malaria were searched in PubMed, Scopus, and Web of Science. The risk of bias of the included studies was assessed using the checklist for analytical cross-sectional studies developed by the Joanna Briggs Institute. Meta-analyses on the following criteria were performed: (1) pooled prevalence of typhoidal/NTS and malaria co-infection among febrile patients, (2) pooled prevalence of typhoidal/NTS among malaria patients, (3) pooled prevalence of malaria infections among patients with Salmonella spp. infection, and (4) probability of typhoidal/NTS and malaria co-infection among febrile patients. Additionally, the case fatality rate and mean difference of malarial parasitemia between typhoidal/NTS and malaria co-infection and Plasmodium monoinfection were also determined. The subgroup analyses of typhoidal/NTS, regions (Africa and Asia), countries, time (publication year), characteristics of participants, and diagnostic tests for identifying Salmonella spp. were also conducted. A sensitivity test was performed to determine the robustness of the study outcomes. Publication bias among the included studies was evaluated using the funnel plot and Egger’s test. All analyses were performed using Stata version 15 (StataCorp LLC, Texas, USA) with a p-value < 0.05 indicating statistical significance. Eighty-one studies that met the eligibility criteria were included in the analyses. Of the 73,775 study participants, 4523 had typhoidal/NTS and malaria co-infections. The pooled prevalence rates of typhoidal/NTS and malaria co-infection among febrile patients were 14% (95% confidence interval [CI], 9–19%; I², 99.4%; 2971/17,720 cases) and 1% (95% CI 1–1%; I², 89.9%; 252/29,081 cases) using the Widal test and culture methods for identifying Salmonella spp., respectively. The pooled prevalence rates of typhoidal/NTS infection among patients with malaria were 31% (95% CI 23–39%; I², 99.5%; 3202/19,208 cases) and 3% (95% CI 2–3%; I², 86.8%; 407/40,426 cases) using the Widal test and culture methods for identifying Salmonella spp., respectively. The pooled prevalence rates of malaria infection among patients with typhoidal/NTS were 17% (95% CI 6–29%; I², 33.3%; 13/75 cases) and 43% (95% CI 32–53%; I², 89.1%; 287/736 cases), respectively. Malaria infection was associated with typhoidal/NTS in children aged < 15 years (p < 0.0001; odds ratio, 0.36; 95% CI 0.23–0.58; I², 73.9%; 3188/43,212 cases). The case fatality rate in patients with malaria and NTS co-infections was 16% (95% CI 9–24%; I², 89.1%; 18/103 cases). From the view of the present study, the inappropriate use of the Widal test for Salmonella spp. diagnosis can overestimate the prevalence of typhoidal/NTS and malaria co-infections. Malaria infection associated with typhoidal/NTS in children and the high case fatality rates among few patients with co-infections were highlighted. Future prospective longitudinal studies using the appropriate and confirmatory dsiagnosis for Salmonella spp. infections are highly recommended to ensure the real prevalence of co-infection and highlight the outcome of co-infection for providing adequate treatment in febrile patients who live in areas where malaria is endemic, such as tropical Africa and India.

Salmonella Typhimurium and inflammation: a pathogen-centric affair

Microbial infections are controlled by host inflammatory responses that are initiated by innate immune receptors after recognition of conserved microbial products. As inflammation can also lead to disease, tissues that are exposed to microbial products such as the intestinal epithelium are subject to stringent regulatory mechanisms to prevent indiscriminate signalling through innate immune receptors. The enteric pathogen Salmonella enterica subsp. enterica serovar Typhimurium, which requires intestinal inflammation to sustain its replication in the intestinal tract, uses effector proteins of its type III secretion systems to trigger an inflammatory response without the engagement of innate immune receptors. Furthermore, S. Typhimurium uses a different set of effectors to restrict the inflammatory response to preserve host homeostasis. The S. Typhimurium-host interface is a remarkable example of the unique balance that emerges from the co-evolution of a pathogen and its host.

CD4+ T cell immunity to Salmonella is transient in the circulation

While Salmonella enterica is seen as an archetypal facultative intracellular bacterial pathogen where protection is mediated by CD4⁺ T cells, identifying circulating protective cells has proved very difficult, inhibiting steps to identify key antigen specificities. Exploiting a mouse model of vaccination, we show that the spleens of C57BL/6 mice vaccinated with live-attenuated Salmonella serovar Typhimurium (S. Typhimurium) strains carried a pool of IFN-γ⁺ CD4⁺ T cells that could adoptively transfer protection, but only transiently. Circulating Salmonella-reactive CD4⁺ T cells expressed the liver-homing chemokine receptor CXCR6, accumulated over time in the liver and assumed phenotypic characteristics associated with tissue-associated T cells. Liver memory CD4⁺ T cells showed TCR selection bias and their accumulation in the liver could be inhibited by blocking CXCL16. These data showed that the circulation of CD4⁺ T cells mediating immunity to Salmonella is limited to a brief window after which Salmonella-specific CD4⁺ T cells migrate to peripheral tissues. Our observations highlight the importance of triggering tissue-specific immunity against systemic infections.

Helper T cells are essential for controlling infections by bacterial pathogens, such as Salmonella enterica var Typhimurium (S. Typhimurium). While it is well-established that this role is related to their provision of IFN-γ, when and where helper T cells elicit their protective function in vivo remains unresolved. We identified a protective helper T cell population in the circulation of mice early after inoculation with growth-attenuated S. Typhimurium strains; this population waned overtime. We observed that circulating helper T cell immunity can adoptively protect naïve recipient mice against lethal S. Typhimurium infection when harvested from a short time-window. In comparing helper T cell responses between spleen and liver in Salmonella-infected mice, we have observed a previously uncharacterized trafficking of helper T cells to the liver followed by the residence of S. Typhimurium-specific T cell memory in the organ. Taken together these findings identify that protective immunity to Salmonella infections is transient in the circulation and the liver as a preferential site of helper T memory cells.

Gut-microbiota derived bioactive metabolites and their functions in host physiology

Every individual harbours a complex, diverse and mutualistic microbial flora in their intestine and over the time it became an integral part of the body, affecting a plethora of activities of the host. Interaction between host and gut-microbiota affects several aspects of host physiology. Gut-microbiota affects host metabolism by fermenting unabsorbed/undigested carbohydrates in the large intestine. Not only the metabolic functions, any disturbances in the composition of the gut-microbiota during first 2-3 years of life may impact on the brain development and later affects cognition and behaviour. Thus, gut-dysbiosis causes certain serious pathological conditions in the host including metabolic disorders, inflammatory bowel disease and mood alterations, etc. Microbial-metabolites in recent times have emerged as key mediators and are responsible for microbiota induced beneficial effects on host. This review provides an overview of the mechanism of microbial-metabolite production, their respective physiological functions and the impact of gut-microbiome in health and diseases. Metabolites from dietary fibres, aromatic amino acids such as tryptophan, primary bile acids and others are the potential substances and link microbiota to host physiology. Many of these metabolites act as signalling molecules to a number of cells types and also help in the secretion of hormones. Moreover, interaction of microbiota derived metabolites with their host, immunity boosting mechanisms, protection against pathogens and modulation of metabolism is also highlighted here. Understanding all these functional attributes of metabolites produced from gut-microbiota may lead to the opening of a new avenue for preventing and developing potent therapies against several diseases.

Bacteria-Cancer Interface: Awaiting the Perfect Storm

Epidemiological evidence reveal a very close association of malignancies with chronic inflammation as a result of persistent bacterial infection. Recently, more studies have provided experimental evidence for an etiological role of bacterial factors disposing infected tissue towards carcinoma. When healthy cells accumulate genomic insults resulting in DNA damage, they may sustain proliferative signalling, resist apoptotic signals, evade growth suppressors, enable replicative immortality, and induce angiogenesis, thus boosting active invasion and metastasis. Moreover, these cells must be able to deregulate cellular energetics and have the ability to evade immune destruction. How bacterial infection leads to mutations and enriches a tumour-promoting inflammatory response or micro-environment is still not clear. In this review we showcase well-studied bacteria and their virulence factors that are tightly associated with carcinoma and the various mechanisms and pathways that could have carcinogenic properties.

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

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

Incidence and Risk Factors for Notifiable Typhoid and Paratyphoid in Taiwan during the Period 2011-2020

The risk of the geographic transmission of emerging infectious diseases through air travel varies greatly. In this study, we collected data on cases of food-borne diseases between the years 2011 and 2020 in Taiwan to access the epidemiological features, differences, and trends in domestic and imported cases of typhoid and paratyphoid in terms of patient sex, age, month of confirmation, and area of residence. In this study, we made use of the open data website provided by Taiwan’s Centers for Disease Control (TCDC) to extract the reported numbers of cases of typhoid and paratyphoid between January and December from 2011 to 2020 for comparison. Univariate analysis was performed using the Chi-square test for categorical variables. Fisher’s exact test was performed if an expected frequency was less than 5. A total of 226 typhoid cases and 61 paratyphoid cases were analyzed from the database. The incidences of typhoid and paratyphoid per million of the population were 0.42–2.11 and 0–0.39, respectively. There was a significant difference in the incidence of the diseases between the age groups (p = 0.019), with a gradual increase in the 20–40 years group. A distinct seasonal (between fall and spring) variation was also observed (p = 0.012). There were 34 cases of children with typhoid in the period 2011–2015 and 12 cases of children with typhoid in the period 2016–2020. During these periods, there were two cases of paratyphoid. This study indicated that the risk of children suffering from typhoid has been significantly reduced in the last five years. Furthermore, we found that more women have acquired typhoid and paratyphoid than men, and that living in the Taipei metropolitan area and the northern area was a potential risk factor. Furthermore, the number of imported cases of typhoid (n = 3) and paratyphoid (n = 0) reported during the COVID-19 pandemic was lower than that reported for the same disease from 2011 to 2020. More typhoid and paratyphoid cases were imported from Indonesia, India, Myanmar, and Cambodia. This study represents the first report on confirmed cases of acquired typhoid and paratyphoid from surveillance data from Taiwan’s CDC for the period 2011–2020. This study also demonstrates that the cases of typhoid and paratyphoid decreased in Taiwan during the COVID pandemic. Big data were used in this study, which may inform future surveillance and research efforts in Taiwan.

Salmonella Typhi stool shedding by enteric fever patients and asymptomatic chronic carriers in an endemic urban setting

The burden of Salmonella Typhi shedding in stool and its contribution to transmission in endemic settings is unknown. During passive surveillance S. Typhi shedding was seen during convalescence in 332 bacteremic typhoid patients although none persisted at one-year follow-up. Anti-Vi-IgG titres were measured in age-stratified cohort of serosurveillance participants. Systematic stool sampling of 303 participants with high anti-Vi-IgG titres identified one asymptomatic carrier shedding. These findings suggest ongoing S. Typhi transmission in this setting is more likely to occur from acute convalescent cases although better approaches are needed to identify true chronic carriers in the community to enable typhoid elimination.