Typhoid fever

Synergistic decontamination of Salmonella spp. in raw almonds using phytic acid and drying as an eco-friendly alternative to propylene oxide

Multistate Salmonella outbreaks involving raw almonds have led to U.S. FDA regulations requiring a minimum 4-log reduction in Salmonella during manufacturing processes. While propylene oxide fumigation is a common industrial pasteurization method, given the growing public concern about the use of synthetic chemicals, alternative methods with significant efficacy and minimal quality deterioration are needed. This study aimed to develop eco-friendly decontamination technology for raw almonds that includes natural-borne substance treatment and drying. The bactericidal effects of phytic acid (1, 2, 3 % (v/w)) and/or drying (6, 8 h at 75 °C) were investigated on Salmonella spp. (S. Enteritidis ATCC 13076, S. Enteritidis PT30, and S. Typhimurium DT104; ca. 3-4 or 6-7 log), which were artificially inoculated in raw almonds at moderate (ca. 3-4 log) or high (ca. 6-7 log) inoculum levels. Additionally, an enrichment test was conducted to validate the recovery of injured cells after treatment. The physicochemical, textural, and sensory attributes (color, pH, water activity, hardness; appearance, color, odor) of untreated/treated almonds were further analyzed. All individual treatments of 1-3 % phytic acid or 6-8 h of drying resulted in low antibacterial efficacies (< 1.0 log reduction from high inoculum and <2.1 log reduction from moderate inoculum; P < 0.05). For the high inoculum, 3 % phytic acid treatment followed by 8 h of drying achieved a >6.2 log reduction in Salmonella spp. in raw almonds (P < 0.05), and most of the injured bacterial cells (83.3 %) showed no recovery after enrichment. The equivalent treatment of almonds at a moderate inoculum level completely eliminated Salmonella spp. (> 3.1 log reduction; P < 0.05) without recovery. Moreover, the panelists indicated no significant differences (P > 0.05) in the tested sensory attributes (appearance, color, and odor) between the optimal treatment and the control, although some physicochemical properties were slightly affected. The results of this study suggest a novel decontamination method using a natural-borne substance that exerts a synergistic effect with drying against Salmonella spp. in raw almonds and ensures minimal deterioration in food quality. The developed method is expected to replace synthetic chemical decontamination methods in nuts and other low-moisture food industries.

Typhoid toxin causes neuropathology by disrupting the blood-brain barrier

Typhoid fever, primarily caused by Salmonella Typhi, can result in severe life-threatening complications such as encephalopathy. Here we elucidate the mechanisms by which typhoid toxin, a unique virulence factor of S. Typhi, mediates the neuropathology associated with typhoid fever. Utilizing mice engineered to have specific tissues protected from toxin action and an in vitro model of the blood-brain barrier (BBB), we demonstrate that, rather than direct action on neuronal or glial cells, typhoid toxin causes neuropathology by disrupting the BBB. Intravenous tracer studies confirmed significant BBB permeability changes following toxin exposure, an effect we found to be mediated by typhoid toxin's CdtB catalytic subunit. We demonstrate that corticosteroids are effective at mitigating BBB disruption in vivo, supporting their use for managing typhoid fever neurological complications. Our data reveal mechanistic insight into how typhoid toxin causes encephalopathy and suggest targeted therapeutic interventions to alleviate the severe neurological manifestations of typhoid fever.

Typhoid conjugate vaccines for preventing typhoid fever (enteric fever)

RATIONALE

Typhoid fever is a major cause of enteric disease-related morbidity and mortality. Vaccination reduces disease burden and prevents outbreaks, but policies and programmes should be informed by the most recent evidence as newer vaccines become available.

OBJECTIVES

To assess the benefits and harms of typhoid conjugate vaccines (TCVs) compared to no vaccine, placebo, typhoid-inactive agents (vaccines for another disease) or other typhoid vaccines for preventing morbidity and mortality associated with typhoid fever in adults and children.

SEARCH METHODS

In April 2024, we searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, CINAHL, Global Index Medicus, United States Advisory Committee on Immunization Practices and the World Health Organization vaccine repository for randomised controlled trials (RCTs), with no restrictions. We also searched clinical trial registries for ongoing trials (www.

CLINICALTRIALS

gov and the WHO International Clinical Trials Registry Platform), grey literature, bibliographic citations of reviews and key articles for additional studies. We contacted study authors for information about ongoing studies.

ELIGIBILITY CRITERIA

We included RCTs and cluster-RCTs of children and adults living in typhoid-endemic areas or travelling to typhoid-endemic areas. We included studies comparing TCVs to controls (i.e. no vaccine, placebo or vaccines for another disease), non-conjugated typhoid vaccines or other TCVs.

OUTCOMES

Outcomes included acute typhoid fever, defined by laboratory-confirmed isolation of Salmonella typhi, all-cause mortality, adverse events (AEs) and serious adverse events (SAEs).

RISK OF BIAS

Review authors independently assessed risk of bias for all outcomes, using the Cochrane RoB 2 tools. We resolved disagreements through discussion or adjudication. We assessed the intention-to-treat effect and used the overall RoB judgement to assess the certainty of evidence for each outcome.

SYNTHESIS METHODS

Three review authors independently screened titles and abstracts for eligible studies, followed by full-text assessment. Disagreements were resolved through discussion or adjudication by a fourth author. Four authors independently extracted characteristics of included studies and outcome data using a piloted, standardised data extraction form. We synthesised results for each outcome where possible, using the Mantel-Haenszel statistical method and random-effects analysis model. Where meta-analysis was not possible due to the nature of the data, we planned to synthesise results based on direction of effect. We used GRADE to assess the certainty of evidence for each outcome, assessing risk of bias, inconsistency, indirectness, imprecision and other bias.

INCLUDED STUDIES

We included 19 trials (17 RCTs and two cluster-RCTs). The 19 trials enrolled 395,650 participants, with ages ranging from six weeks to 60 years. Vaccines were delivered as a single dose in 14 studies; two doses, ranging from four to 24 weeks apart, in six studies; and three doses, four weeks apart, in one study. Comparators included: no vaccine, placebo and other vaccines. Seven studies compared TCV with non-conjugated typhoid vaccines. Six studies compared one TCV to another TCV.

SYNTHESIS OF RESULTS

TCV compared to control may result in a large reduction in acute typhoid fever (risk ratio (RR) 0.20, 95% confidence interval (CI) 0.12 to 0.32; I2 = 70%; 6 studies, 101,896 participants; low-certainty evidence) and probably results in little to no difference in all-cause mortality (RR 0.80, 95% CI 0.35 to 1.85; I2 = 52%; 4 studies, 100,337 participants; moderate-certainty evidence). TCV results in little to no difference in AEs when compared to control (RR 0.91, 95% CI 0.76 to 1.09; I2 = 0%; 3 studies, 29,465 participants; high-certainty evidence) and a slight reduction in SAEs compared to control (RR 0.82, 95% CI 0.71 to 0.95; I2 = 0%; 6 studies, 89,625 participants; high-certainty evidence). TCV compared to non-conjugated typhoid vaccines may result in little to no difference in acute typhoid fever (RR 0.90, 95% CI 0.48 to 1.69; 1 study, 78 participants; low-certainty evidence). There were no deaths in the included studies. When compared to non-conjugated typhoid vaccines, TCV likely results in little to no difference in AEs (RR 1.00, 95% CI 0.77 to 1.31; I2 = 0%; 3 studies, 244 participants; moderate-certainty evidence) and likely results in a slight reduction in SAEs (RR 0.30, 95% CI 0.05 to 1.88; I2 = 0%; 2 studies, 732 participants; moderate-certainty evidence). For TCV compared to another TCV, none of the studies reported on acute typhoid fever. Vi tetanus toxoid vaccine (Vi-TT) may result in little to no difference in all-cause mortality compared to a different TCV (RR 5.19, 95% CI 0.54 to 49.80; I2 = 0%; 2 studies, 2422 participants; low-certainty evidence). Vi-TT likely results in little to no difference in AEs compared to another TCV (RR 1.18, 95% CI 0.92 to 1.51; I2 = 39%; 4 studies, 2916 participants; moderate-certainty evidence) and may result in little to no difference in SAEs (RR 2.48, 95% CI 0.74 to 8.36; I2 = 0%; 3 studies, 2866 participants; low-certainty evidence). The certainty of evidence was consistently reduced due to imprecision, indirectness and bias.

AUTHORS' CONCLUSIONS

This review highlights that TCVs, compared to controls, are effective in preventing typhoid fever, and may confer protection for up to four years. TCVs compared to non-conjugated typhoid vaccines may result in little to no difference in acute typhoid fever and AEs, and likely result in a slight reduction in SAEs. Vi-TT compared to another TCV may result in little to no difference in all-cause mortality or SAEs, and likely results in little to no difference in AEs.

FUNDING

NG, TL and TK were partly supported by, and the Cochrane Infectious Diseases Group (CIDG) editorial base is funded by, the Research, Evidence and Development Initiative (READ-It), funded by UK aid for the benefit of low- and middle-income countries (project number 300342-104). The views expressed in this review do not necessarily reflect the official policies of the UK government.

REGISTRATION

Protocol available via doi.org/10.1002/14651858.CD015746.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Assessing Salmonella Typhi Pathogenicity and Prevention: The Crucial Role of Vaccination in Combating Typhoid Fever

Enteric fever is caused by Salmonella enterica serovar Typhi (S. Typhi) and Salmonella enterica serovar Paratyphi (S. Paratyphi) A, B, and C. Globally, an estimated 11 to 21 million cases of typhoid and paratyphoid fever occur annually, with approximately 130,000-160,000 deaths, most of which are reported in South/Southeast Asia and sub-Saharan Africa. The antibiotic susceptibility of S. Typhi strains varies between countries within broad limits, from 3% to 97% for ampicillin, 9% to 95% for ciprofloxacin, 4% to 94% for chloramphenicol (India vs. Pakistan), and 0% to 99% for ceftriaxone (India vs. Iraq). With S. Typhi increasingly exhibiting resistance to antibiotics, vaccination becomes an essential preventive measure. Currently, three vaccines are licensed for typhoid fever: the typhoid conjugate vaccine (TCV), live-attenuated oral vaccine Ty21a (Ty21a), and Vi capsular polysaccharide vaccine (Vi-CPS). While no specific vaccine exists for paratyphoid fever, the genetic and antigenic similarities between S. Paratyphi and S. Typhi offer potential for the development of such a vaccine. Early studies show promising results, demonstrating both safety and immunogenicity in preclinical trials. Whole genome sequencing (WGS) provides a powerful tool for assigning genotypes, identifying plasmids, comparing genetic elements, and investigating molecular factors that contribute to antibiotic resistance and virulence.

Salmonella Surgical Site Infection After Cervical Spine Surgery: A Case Report

CASE

A 59-year-old man sustained a fall onto his head and was found to have dense bilateral upper extremity weakness worse than lower extremity and radiographic cervical cord compression. He underwent emergent decompression and presented a few days after discharge with a Salmonella surgical site infection (SSI).

CONCLUSION

Central cord syndrome is the most common type of incomplete spinal cord injury. Early decompression is associated with the best outcomes. However, infection represents a problematic complication, contributing to overall morbidity. Salmonella can be a very rare contributor to SSI. This is the first report of Salmonella SSI after spine surgery in an immunocompetent patient.

Virulence factors of Salmonella Typhi: interplay between the bacteria and host macrophages

Salmonella Typhi (S. Typhi) is a Gram-negative bacterium that exclusively infects humans and causes typhoid fever- a major global public health concern responsible for approximately 9 million infections and 110,000 deaths annually. Macrophages, a key component of the innate immune system, play essential roles in pathogen clearance, antigen presentation, immune regulation, and tissue repair. As one of the primary targets of S. Typhi infection, macrophages significantly influence disease onset and progression. S. Typhi expresses a range of virulence factors, including the virulence-associated (Vi) capsule, outer membrane proteins (OMPs), flagella, fimbriae, type III secretion systems (T3SSs) and other genes encoded on Salmonella pathogenicity islands (SPIs), as well as toxins, regulatory factors, and virulence plasmids. These virulence factors facilitate S. Typhi's intracellular survival within macrophages by mediating processes such as adhesion, invasion, nutrient acquisition and immune evasion, ultimately enabling systemic infection. This review explores the role and molecular mechanisms of S. Typhi virulence factors in counteracting macrophage antimicrobial functions, providing insights for future research on typhoid pathogenesis and the development of potential therapeutic interventions.

Intestinal Microbiota and Vaccinations: A Systematic Review of the Literature

Background: Vaccination constitutes a low-cost, safe, and efficient public health measure that can help prevent the spread of infectious diseases and benefit the community. The fact that vaccination effectiveness varies among populations, and that the causes of this are still unclear, indicates that several factors are involved and should be thoroughly examined. The "intestinal microbiota" is the most crucial of these elements. Numerous clinical studies demonstrate the intestinal microbiota's significance in determining the alleged "immunogenicity" and efficacy of vaccines. This systematic review aimed to review all relevant scientific literature and highlight the role of intestinal microbiota in COVID-19, Salmonella typhi, Vibrio cholerae, and rotavirus vaccinations. Materials and Methods: The MESH terms "vaccines" and "microbiota" were used to search the major scientific databases PubMed, SciVerse Scopus, Web of Knowledge, and the Cochrane Central Register of Controlled Clinical Trials. Results: Between February 2024 and October 2024, the analysis was conducted using electronic databases, yielding a total of 235 references. Finally, 24 RCTs were chosen after meeting all inclusion criteria: eight studies of COVID-19, two studies of Salmonella typhi, three studies of Vibrio cholerae, and eleven studies of rotavirus. Only six of these demonstrated good study quality with a Jadad score of three or four. Conclusions: According to the review's results, the intestinal microbiota surely plays a role in vaccinations' enhanced immunogenicity, especially in younger people. As it is still unclear what mechanisms underlie this effect, more research is needed to better understand the role of the intestinal microbiota.

Prolonged Fever in a Multidrug-Resistant Typhoid Fever Patient Despite Appropriate Antimicrobial Therapy: A Case Report

Typhoid fever, caused by Salmonella enterica serovar Typhi (S. Typhi), remains a significant global health concern. The emergence of multidrug-resistant (MDR) S. Typhi strains, including extended-spectrum beta-lactamase (ESBL) producers, has further complicated treatment by limiting the effectiveness of first-line and some second-line antibiotics. We present a case of a 10-year-old boy who developed a prolonged febrile illness after traveling to a typhoid-endemic region. Initial treatment with ceftriaxone proved ineffective due to the presence of ESBL-producing S. Typhi, necessitating a change to meropenem combined with azithromycin. Despite persistent fever, the patient showed clinical improvement by day five and became afebrile by day 11, and there was improvement of inflammatory markers and resolution of bacteremia, as confirmed by sterile blood cultures on day 12. This case underscores the challenges in managing MDR typhoid fever and highlights the critical need to maintain appropriate antibiotic regimens, even in the context of prolonged febrile responses. Furthermore, it draws attention to the global spread of MDR and extensively drug-resistant (XDR) S. Typhi, often facilitated by international travel, emphasizing the need for vigilant resistance monitoring and empiric treatment adjustments. Effective antibiotic stewardship, adherence to evidence-based guidelines, and heightened clinical awareness are essential to address the complex public health and clinical challenges posed by MDR and XDR S. Typhi.

Two cases with extensively drug-resistant Salmonella Typhi infection returning from Pakistan

We report two cases of patients with extensively drug-resistant Salmonella Typhi infection who had recently traveled to Pakistan. These cases suggest that obtaining a detailed travel history and considering the epidemiology of drug-resistant S. Typhi in the suspected area of acquisition is crucial for managing patients with typhoid fever.

Foodborne Infections and Salmonella: Current Primary Prevention Tools and Future Perspectives

Salmonella is considered the major zoonotic and foodborne pathogen responsible for human infections. It includes the serovars causing typhoid fever (S. typhi and S. paratyphi) and the non-typhoidal salmonella (NTS) serovars (S. enteritidis and S. typhimurium), causing enteric infections known as "Salmonellosis". NTS represents a major public health burden worldwide. The consumption of S. enteritidis-contaminated animal foods is the main source of this disease in humans, and eradicating bacteria from animals remains a challenge. NTS causes various clinical manifestations, depending on the quantity of bacteria present in the food and the immune status of the infected individual, ranging from localized, self-limiting gastroenteritis to more serious systemic infections. Salmonellosis prevention is based on hygienic and behavioral rules related to food handling that aim to reduce the risk of infection. However, no vaccine against NTS is available for human use. This aspect, in addition to the increase in multidrug-resistant strains and the high morbidity, mortality, and socioeconomic costs of NTS-related diseases, makes the development of new prevention and control strategies urgently needed. The success of the vaccines used to protect against S. typhi encouraged the development of NTS vaccine candidates, including live attenuated, subunit-based, and recombinant-protein-based vaccines. In this review, we discuss the epidemiological burden of Salmonellosis and its primary prevention, focusing on the current status and future perspectives of the vaccines against NTS.

A Rare and Life-Threatening Complication of Salmonella Typhi Infection: A Case Report From India Highlighting Diagnostic and Therapeutic Challenges in Salmonella Sepsis

Salmonella infections are widely known to cause gastroenteritis, especially in areas of poor hygiene and sanitation. Common symptoms include sustained fever, chills, and abdominal pain. Sepsis, disseminated intravascular coagulation (DIC), various neurological manifestations, and multiorgan failure are other uncommon presentations. Raising appropriate awareness about its clinical spectrum is therefore crucial, even in the absence of typical symptoms. The following case of a 34-year-old Indian female who developed Salmonella Typhi-induced sepsis addresses various challenges involved in diagnosing and treating the condition. The case was successfully managed with rapid diagnostics, targeted antibiotic therapy, and supportive care. Recognizing the condition early and providing necessary treatment is therefore vital to preventing substantial morbidity and mortality. To improve outcomes for critically ill patients, it is important that the causative organism be identified quickly and appropriate treatment be commenced. Here, we present a case of Salmonella sepsis complicated by DIC, its clinical course, and the diagnostic and treatment modalities we have followed.

Salmonella Typhi Haplotype 58 biofilm formation and genetic variation in isolates from typhoid fever patients with gallstones in an endemic setting in Kenya

Although typhoid fever has largely been eliminated in high-income countries, it remains a major global public health concern especially among low- and middle-income countries. The causative agent, Salmonella enterica serovar Typhi (S. Typhi), is a human restricted pathogen with a limited capacity to replicate outside the human host. Human carriers, 90% of whom have gallstones in their gallbladder, continue to shed the pathogen for an ill-defined period of time after treatment. The genetic mechanisms involved in establishing the carrier state are poorly understood, but S. Typhi is thought to undergo specific genetic changes within the gallbladder as an adaptive mechanism. In the current study, we aimed to identify the genetic differences in longitudinal clinical S. Typhi isolates from asymptomatic carriers with gallstones in a typhoid endemic setting in Nairobi, Kenya. Whole-genome sequences were analyzed from 22 S. Typhi isolates, 20 from stool samples, and 2 from blood samples, all genotype 4.3.1 (H58). Out of this, 19 strains were from four patients also diagnosed with gallstones, of whom three had typhoid symptoms and continued to shed S. Typhi after treatment. All isolates had point mutations in the quinolone resistance-determining region (QRDR), and only sub-lineage 4.3.1.2.EA3 encoded multidrug resistance genes. There was no variation in antimicrobial resistance patterns among strains from the same patient/household. Non-multidrug resistant (MDR) isolates formed significantly stronger biofilms in vitro than the MDR isolates, p<0.001. A point mutation within the treB gene (treB A383T) was observed in strains isolated after clinical resolution from patients living in 75% of the households. For missense mutations in Vi capsular polysaccharide genes, tviE P263S was also observed in 18% of the isolates. This study provides insights into the role of typhoid carriage, biofilm formation, AMR genes, and genetic variations in S. Typhi during asymptomatic carriage.

The global burden of enteric fever, 2017-2021: a systematic analysis from the global burden of disease study 2021

Background

Enteric fever is a major public health challenge in developing countries. We conducted a systematic analysis from the Global Burden of Diseases 2021 Study to provide updated estimates of enteric fever's burden.

Methods

We presented estimates for incident cases and deaths, age-standardized incidence and mortality rates, years of life lost (YLLs), and case-fatality rates spanning the study period of 2017-2021, stratified by region, country, socio-demographic index (SDI), and age group. Random-effects Poisson regression for longitudinal data was used to estimate the association between SDI and case-fatality rates, adjusting for antimicrobial resistance patterns.

Findings

In 2021, there were 9.3 million global cases of enteric fever (95% uncertainty interval: 7.3-11.9) and 107.5 thousand deaths (56.1-180.8). The age-standardized incidence rate decreased from 152/100,000 person-years (118-195) in 2017 to 128/100,000 person-years (100-163) in 2021, and the mortality rate decreased from 1.87/100,000 person-years (0.95-3.18) to 1.50/100,000 person-years (0.78-2.54). There were wide geographical differences, with South Asia contributing the most cases and deaths. Age-standardized incidence exceeded the threshold for "high burden" of enteric fever (100/100,000 person-years) in 23 countries in 2021.Children under five accounted for 40% of deaths and 47% of YLLs, with incidence and mortality peaking during the second year. Case-fatality was highest in low SDI countries and showed a global trend toward reduction, except among children aged 1-4 years. After adjusting for the prevalence of multidrug resistance, fluoroquinolone non-susceptibility, and third-generation cephalosporin resistance, a higher SDI was associated with a lower case-fatality rate, with a 1.1% (0.7-1.7) reduction for each percentage point increase in SDI.

Interpretation

Despite notable improvements, several countries still showed a high burden of enteric fever, which remains a significant global health concern, especially among children under five. Although enhancing water and sanitation systems is crucial, the most significant reductions in the global disease burden are likely to be achieved through broader vaccine coverage. This includes the use of typhoid conjugate vaccines, which are effective in infants and young children and offer extended protection, along with improved data collection and surveillance to guide vaccine distribution efforts across high-incidence areas.

Funding

This work was partially supported by "Ricerca Corrente" funding from Italian Ministry of Health to IRCCSHumanitas Research Hospital.

Salmonella associated with agricultural animals exhibit diverse evolutionary rates and show evidence of recent clonal expansion

Most foodborne salmonellosis outbreaks are linked to agricultural animal products with a few serovars accounting for most Salmonella isolated from specific animal products, suggesting an adaptation to the corresponding animal hosts and their respective environments. Here, we utilized whole-genome sequence (WGS) data to analyze the evolution and population genetics of seven serovars frequently isolated from ground beef (Montevideo, Cerro, and Dublin), chicken (Kentucky, Infantis, and Enteritidis), and turkey (Reading) in the United States. In addition, publicly available metadata were used to characterize major clades within each serovar with regard to public health significance. Except for Dublin, all serovars were polyphyletic, comprising 2-6 phylogenetic groups. Further partitioning of the phylogenies identified 25 major clades, including 12 associated with animal or environmental niches. These 12 clades differed in evolutionary parameters (e.g., substitution rates) as well as public health relevant characteristics (e.g., association with human illness, antimicrobial resistance). Overall, our results highlight several critical trends: (i) the Salmonella generation time appears to be more dependent on source than serovar and (ii) all serovars contain clades and sub-clades that are estimated to have emerged after the year 1940 and that are enriched for isolates associated with humans, agricultural animals, antimicrobial resistance (AMR), and/or specific geographical regions. These findings suggest that serotyping alone does not provide enough resolution to differentiate isolates that may have evolved independently, present distinct geographic distribution and host association, and possibly have distinct public health significance.

IMPORTANCE

Non-typhoidal Salmonella are major foodborne bacterial pathogens estimated to cause more than one million illnesses, thousands of hospitalizations, and hundreds of deaths annually in the United States. More than 70% of Salmonella outbreaks in the United States have been associated with agricultural animals. Certain serovars include persistent strains that have repeatedly contaminated beef, chicken, and turkey, causing outbreaks and sporadic cases over many years. These persistent strains represent a particular challenge to public health, as they are genetically clonal and widespread, making it difficult to differentiate distinct outbreak and contamination events using whole-genome sequence (WGS)-based subtyping methods (e.g., core genome allelic typing). Our results indicate that a phylogenetic approach is needed to investigate persistent strains and suggest that the association between a Salmonella serovar and an agricultural animal is driven by the expansion of clonal subtypes that likely became adapted to specific animals and associated environments.

Cytolysin A is an intracellularly induced and secreted cytotoxin of typhoidal Salmonella

Typhoidal Salmonella enterica serovars, such as Typhi and Paratyphi A, cause severe systemic infections, thereby posing a significant threat as human-adapted pathogens. This study focuses on cytolysin A (ClyA), a virulence factor essential for bacterial dissemination within the human body. We show that ClyA is exclusively expressed by intracellular S. Paratyphi A within the Salmonella-containing vacuole (SCV), regulated by the PhoP/Q system and SlyA. ClyA localizes in the bacterial periplasm, suggesting potential secretion. Deletion of TtsA, an essential Type 10 Secretion System component, completely abolishes intracellular ClyA detection and its presence in host cell supernatants. Host cells infected with wild-type S. Paratyphi A contain substantial ClyA, with supernatants capable of lysing neighboring cells. Notably, ClyA selectively lyses macrophages and erythrocytes while sparing epithelial cells. These findings identify ClyA as an intracellularly induced cytolysin, dependent on the SCV environment and secreted via a Type 10 Secretion System, with specific cytolytic activity.

Environmental surveillance for Salmonella Typhi in rivers and wastewater from an informal sewage network in Blantyre, Malawi

Environmental surveillance for Salmonella Typhi may provide information on the community-level dynamics of typhoid fever in resource poor regions experiencing high disease burden. Many knowledge gaps concerning the feasibility of ES remain, especially in areas lacking formal sewage systems. We implemented protocols for S. Typhi ES, including site selection and catchment population estimation, sample concentration and testing using qPCR for S. Typhi specific gene targets. Between May 2021 and May 2022, we collected grab samples and Moore swabs from 43 sites in Blantyre, Malawi. Catchment characteristics, water quality, and human faecal contamination (qPCR for Bacteroides HF183) were also recorded. Their association with S. Typhi detection was investigated using a logistic mixed-effects regression analysis. Prevalence of S. Typhi in ES samples was 2.1% (1.1-4.0%) and 3.9% (1.9-7.9%) for grab and Moore swab samples, respectively. HF183 was associated S. Typhi positivity, with a unit increase in log genome copies/microlitre increasing the odds of detection of S. Typhi by 1.56 (95% CI: 1.29-1.89) and 1.33 (1.10-1.61) in Moore swabs and grab samples, respectively. The location and timing of S. Typhi detection through ES was not associated with the incidence of typhoid fever reported in associated catchment populations. During this period of relatively low typhoid fever incidence, wastewater surveillance continued to detect S. Typhi in human sewage and wastewater suggesting that ES using natural river systems can be a sensitive indicator of transmission.

Salmonella typhi and endocarditis: a systematic review of case reports

Introduction

Salmonella typhi, a gram-negative bacterium responsible for typhoid fever, can infect the inner lining or valves of the heart and cause endocarditis. This systematic review aimed to report cases of S. typhi-associated endocarditis and its clinical features.

Methods

This systematic review was reported as per the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) checklist. Only case reports and case series of endocarditis caused by S. typhi, irrespective of age, gender, and demographics, were considered eligible for inclusion. To identify relevant studies, a literature search was conducted using relevant keywords on PubMed, Google Scholar, and the Cochrane Library from inception to 31 December 2023. After selecting the studies, the relevant data were extracted and pooled in terms of frequencies and percentages. A quality assessment was performed using the Joanna Briggs Institute Critical Appraisal Checklist for Case Reports.

Results

This review included seven case reports, comprising 22.2% female and 77.8% male patients. The mean age of patients was 27.9 + 12.0 years. Regarding past medical history, 33.3% (3/9) of patients had a previous cardiac pathology. Fever remained the most common complaint, occurring in 88.9% of cases. Transthoracic and transesophageal echocardiography were used to diagnose all cases, with 33.3% identifying vegetation on the mitral, aortic, and tricuspid valves. Ceftriaxone, with or without gentamycin, remained the choice of antibiotic for 88.9% of cases, and all patients responded to the offered treatment.

Conclusion

S. typhi-associated endocarditis, though rare, presents unique challenges and requires timely diagnosis. This systematic review of seven cases highlights a predominantly male population affected, with a mean age in the third decade, suggesting a higher invasiveness than other causes. The findings from this study underscore the importance of early recognition and appropriate management, primarily with antibiotic therapy. Further research with larger cohorts is crucial to refine understanding and guide policymaking for this rare but life-threatening condition.

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

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

Salmonella Typhi Haplotype 58 (H58) Biofilm Formation and Genetic Variation in Typhoid Fever Patients with Gallstones in an Endemic Setting in Kenya

The causative agent of typhoid fever, Salmonella enterica serovar Typhi, is a human restricted pathogen. Human carriers, 90% of whom have gallstones in their gallbladder, continue to shed the pathogen after treatment. The genetic mechanisms involved in establishing the carrier state are poorly understood, but S. Typhi is thought to undergo specific genetic changes within the gallbladder as an adaptive mechanism. In the current study, we aimed to identify biofilm forming ability and the genetic differences in longitudinal clinical S. Typhi isolates from asymptomatic carriers with gallstones in Nairobi, Kenya. Whole genome sequences were analyzed from 22 S. Typhi isolates, 20 from stool and 2 from blood samples, all genotype 4.3.1 (H58). Nineteen strains were from four patients also diagnosed with gallstones, of whom, three had typhoid symptoms and continued to shed S. Typhi after treatment. All isolates had point mutations in the quinolone resistance determining region (QRDR) and only sub-lineage 4.3.1.2EA3 encoded multidrug resistance genes. There was no variation in antimicrobial resistance patterns among strains from the same patient/household. Non-multidrug resistant (MDR), isolates formed significantly stronger biofilms in vitro than the MDR isolates, p<0.001. A point mutation within the treB gene (treB A383T) was observed in strains isolated after clinical resolution from patients living in 75% of the households. Missense mutations in Vi capsular polysaccharide genes, tviE P263S was also observed in 18% of the isolates. This study provides insights into the role of typhoid carriage, biofilm formation, AMR genes and genetic variations in S. Typhi from asymptomatic carriers.

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

BACKGROUND

Salmonella enterica serotype Typhi (Salmonella Typhi) causes severe and occasionally life-threatening disease, transmitted through contaminated food and water. Humans are the only reservoir, inadequate water, sanitation, and hygiene infrastructure increases risk of typhoid. High-quality data to assess spatial and temporal relationships in disease dynamics are scarce.

METHODS

We analyzed data from a prospective cohort conducted in an urban slum area of Dhaka City, Bangladesh. Passive surveillance at study centers identified typhoid cases by microbiological culture. Each incident case (index case) was matched to two randomly selected index controls, and we measured typhoid incidence in the population residing in a geographically defined region surrounding each case and control. Spatial clustering was evaluated by comparing the typhoid incidence in residents of geometric rings of increasing radii surrounding the index cases and controls over 28 days. Temporal clustering was evaluated by separately measuring incidence in the first and second 14-day periods following selection. Incidence rate ratios (IRRs) were calculated using Poisson regression models.

RESULTS

We evaluated 141 typhoid index cases. The overall typhoid incidence was 0.44 per 100,000 person-days (PDs) (95% CI: 0.40, 0.49). In the 28 days following selection, the highest typhoid incidence (1.2 per 100,000 PDs [95% CI: 0.8, 1.6]) was in the innermost cluster surrounding index cases. The IRR in this innermost cluster was 4.9 (95% CI: 2.4, 10.3) relative to the innermost control clusters. Neither typhoid incidence rates nor relative IRR between index case and control populations showed substantive differences in the first and second 14-day periods after selection.

CONCLUSION

In the absence of routine immunization programs, geographic clustering of typhoid cases suggests a higher intensity of typhoid risk in the population immediately surrounding identified cases. Further studies are needed to understand spatial and temporal trends and to evaluate the effectiveness of targeted vaccination in disrupting typhoid transmission.

Evolving Epidemiology and Antibiotic Resistance in Enteric Fever: A Comprehensive Review

Enteric fever, predominantly caused by Salmonella enterica serovar Typhi and Salmonella enterica serovar Paratyphi, remains a significant global health challenge. This comprehensive review examines the evolving epidemiology and antibiotic resistance associated with enteric fever. We provide an overview of the disease's definition and historical context, highlighting the substantial impact of antibiotic resistance on treatment efficacy. The review details the global burden, incidence trends, and risk factors of enteric fever while elucidating the pathogenesis and clinical manifestations of the disease. A critical analysis of antibiotic resistance mechanisms reveals the alarming rise of multi-drug resistant (MDR) and extensively drug-resistant (XDR) strains, complicating treatment regimens and underscoring the need for novel therapeutic strategies. Current treatment protocols, the role of empirical therapy, and the rational use of antibiotics are discussed in depth. Additionally, we explore prevention and control strategies, emphasizing the importance of vaccination programs, sanitation improvements, and effective public health interventions. The review concludes with recommendations for future actions, including enhanced surveillance, research and development of new antibiotics, expansion of vaccination efforts, and improved public health infrastructure. The findings highlight the necessity for updated clinical guidelines and sustained global efforts to address the challenges of enteric fever and its evolving antibiotic resistance patterns. Through coordinated action and continued innovation, it is possible to mitigate the impact of this enduring public health threat.

A Systemic Review on Fitness and Survival of Salmonella in Dynamic Environment and Conceivable Ways of Its Mitigation

Gastroenteritis caused by non-typhoidal Salmonella still prevails resulting in several recent outbreaks affecting many people worldwide. The presence of invasive non-typhoidal Salmonella is exemplified by several characteristic symptoms and their severity relies on prominent risk factors. The persistence of this pathogen can be attributed to its broad host range, complex pathogenicity and virulence and adeptness in survival under challenging conditions inside the host. Moreover, a peculiar aid of the ever-changing climatic conditions grants this organism with remarkable potential to survive within the environment. Abusive use of antibiotics for the treatment of gastroenteritis has led to the emergence of multiple drug resistance, making the infections difficult to treat. This review emphasizes the importance of early detection of Salmonella, along with strategies for accomplishing it, as well as exploring alternative treatment approaches. The exceptional characteristics exhibited by Salmonella, like strategies of infection, persistence, and survival parallelly with multiple drug resistance, make this pathogen a prominent concern to human health.

Loss of function of metabolic traits in typhoidal Salmonella without apparent genome degradation

Salmonella enterica serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars are exclusively adapted to the human host, where they can cause life-long persistent infection. A distinct feature of these serovars is the presence of a relatively high number of degraded coding sequences coding for metabolic pathways, most likely a consequence of their adaptation to a single host. As a result of convergent evolution, these serovars shared many of the degraded coding sequences although often affecting different genes in the same metabolic pathway. However, there are several coding sequences that appear intact in one serovar while clearly degraded in the other, suggesting differences in their metabolic capabilities. Here, we examined the functionality of metabolic pathways that appear intact in S. Typhi but that show clear signs of degradation in S. Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in S. Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. Thus, the inability of S. Typhi to metabolize Glucose-6-Phosphate or 3-phosphoglyceric acid is due to the silencing of the expression of the genes encoding the transporters for these compounds due to point mutations in the transcriptional regulatory proteins. In contrast, its inability to utilize glucarate or galactarate is due to the presence of point mutations in the transporter and enzymes necessary for the metabolism of these sugars. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted S. enterica serovars and highlight a limitation of bioinformatic approaches to predict metabolic capabilities.

IMPORTANCE

Salmonella enterica serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars can only infect the human host, where they can cause life-long persistent infection. Because of their adaptation to the human host, these bacterial pathogens have changed their metabolism, leading to the loss of their ability to utilize certain nutrients. In this study we examined the functionality of metabolic pathways that appear intact in S. Typhi but that show clear signs of degradation in S. Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in S. Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted S. enterica serovars.

Acute Abdominal Pain and Rapidly Accumulating Ascites as an Unusual Presentation of Salmonella Typhi: A Case Report

Salmonella typhi (S. typhi) infections typically present with fever and gastrointestinal symptoms. This case report on S. typhi enteritis documents atypical clinical, radiological, and endoscopic findings raising diagnostic challenges. A 31-year-old male in the Kingdom of Saudi Arabia (KSA) presented with severe abdominal pain, vomiting, bloody diarrhea, and no fever. Initial diagnosis included amebiasis and other gastroenteritis infections. Despite treatment with ciprofloxacin and metronidazole, the patient's condition did not improve, and he kept having intractable abdominal pain and vomiting. Subsequent investigations, including abdominal ultrasound and esophagogastroduodenoscopy, revealed extensive and rapidly progressive intestinal inflammation with wall thickening and ascites. Stool culture eventually identified a multidrug-resistant strain of S. typhi, sensitive only to ceftriaxone. Treatment with ceftriaxone and continuous infusion of proton pump inhibitor (PPI) led to significant improvement. The absence of fever in the context of bloody diarrhea, and the rapid development of ascites not improving with first-line treatment of gastroenteritis, led to the search for other diagnoses such as inflammatory bowel syndromes or tuberculosis. The presentation of diffuse intestinal wall thickening with intractable vomiting, bloody diarrhea, and progressively increasing ascites is not frequently encountered with S. typhi. The case also underscores the growing concern of antibiotic-resistant S. typhi strains. The patient's response to targeted antibiotic therapy emphasizes the importance of accurate microbial identification and susceptibility testing in managing infectious diseases. This case report illustrates an atypical presentation of S. typhi enteritis with progressively increasing ascites and increased intestinal wall thickening. The uncommon complicated clinical picture led to challenges in diagnosis and management. It emphasizes the need for high clinical suspicion and comprehensive diagnostic approaches in atypical cases of common infections, especially in the context of increasing antibiotic resistance.

Acute non-immune hemolytic anemia in enteric fever due to nalidixic acid-resistant Salmonella enterica serotype Typhi: A case report

Nalidixic acid-resistant Salmonella enterica serotype Typhi is a well-known cause of enteric fever, and its prevalence is increasing worldwide. However, the incidence of enteric fever complicated by non-immune hemolytic anemia without co-existing thalassemia or glucose-6-phosphate dehydrogenase deficiency is rare. In this case report, we present a case of acute non-immune hemolytic anemia in enteric fever caused by nalidixic acid-resistant Salmonella enterica serotype Typhi.

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

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

IMPORTANCE

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

Nutcracker syndrome unveiled by severe Typhoid fever: A rare case report

Typhoid fever, caused by Salmonella Typhi, is a severe bacterial infection prevalent in developing countries, and can result in life-threatening complications if untreated. Nutcracker Syndrome is a rare vascular disorder involving compression of the left renal vein between the aorta and the superior mesenteric artery. It can lead to various symptoms and poses diagnostic and management challenges. We present a case study of a patient diagnosed with typhoid fever in a Unit of Critical Emergency Care. Coincidentally, the evaluation through CT-scan revealed the presence of Nutcracker Syndrome. This report underscores the incidental discovery of Nutcracker Syndrome during the assessment of a patient with typhoid fever in a critical emergency care setting.

Predominance of multidrug-resistant Salmonella Typhi genotype 4.3.1 with low-level ciprofloxacin resistance in Zanzibar

BACKGROUND

Typhoid fever is a common cause of febrile illness in low- and middle-income countries. While multidrug-resistant (MDR) Salmonella Typhi (S. Typhi) has spread globally, fluoroquinolone resistance has mainly affected Asia.

METHODS

Consecutively, 1038 blood cultures were obtained from patients of all age groups with fever and/or suspicion of serious systemic infection admitted at Mnazi Mmoja Hospital, Zanzibar in 2015-2016. S. Typhi were analyzed with antimicrobial susceptibility testing and with short read (61 strains) and long read (9 strains) whole genome sequencing, including three S. Typhi strains isolated in a pilot study 2012-2013.

RESULTS

Sixty-three S. Typhi isolates (98%) were MDR carrying blaTEM-1B, sul1 and sul2, dfrA7 and catA1 genes. Low-level ciprofloxacin resistance was detected in 69% (43/62), with a single gyrase mutation gyrA-D87G in 41 strains, and a single gyrA-S83F mutation in the non-MDR strain. All isolates were susceptible to ceftriaxone and azithromycin. All MDR isolates belonged to genotype 4.3.1 lineage I (4.3.1.1), with the antimicrobial resistance determinants located on a composite transposon integrated into the chromosome. Phylogenetically, the MDR subgroup with ciprofloxacin resistance clusters together with two external isolates.

CONCLUSIONS

We report a high rate of MDR and low-level ciprofloxacin resistant S. Typhi circulating in Zanzibar, belonging to genotype 4.3.1.1, which is widespread in Southeast Asia and African countries and associated with low-level ciprofloxacin resistance. Few therapeutic options are available for treatment of typhoid fever in the study setting. Surveillance of the prevalence, spread and antimicrobial susceptibility of S. Typhi can guide treatment and control efforts.

Foodborne pathogens and their association with well-known enteric infections and emerging non-communicable disorders

Annually, numerous new cases of communicable and non-communicable diseases are diagnosed, and consumption of food/water contaminated with different levels of microbial and chemical agents is responsible for a considerable portion of this burden. Generally, acute foodborne diseases are readily identified, while chronic deleterious effects are often neglected and rarely blamed for health consequences. The present work narrates a journey from consuming foods containing bacteria/bacterial toxins to developing chronic diseases, making humans more susceptible to emerging diseases. We aim to shed light on the chronic effects of foodborne diseases, particularly gastrointestinal disorders (GIDs) and inflammatory bowel diseases (IBDs), which are common chronic symptoms of most foodborne diseases.

Cryo-EM structure of the bacterial effector protein SipA bound to F-actin reveals a unique mechanism for filament stabilization

The bacterial pathogen Salmonella spp. modulates cellular processes by delivering effector proteins through its type III secretion systems. Among these effectors, SipA facilitates bacterial invasion and promotes intestinal inflammation. The mechanisms by which this effector carries out these functions are incompletely understood although SipA's ability to modulate actin dynamics is central to some of these activities. Here we report the cryo-EM structure of SipA bound to filamentous actin. We show that this effector stabilizes actin filaments through unique interactions of its carboxy terminal domain with four actin subunits. Furthermore, our structure-function studies revealed that SipA's actin-binding activity is independent from its ability to stimulate intestinal inflammation. Overall, these studies illuminate critical aspects of Salmonella pathogenesis, and provide unique insight into the mechanisms by which a bacterial effector modulates actin dynamics.

Typhoid Conjugate Vaccine: A Boon for Endemic Regions

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

Estimating the subnational prevalence of antimicrobial resistant Salmonella enterica serovars Typhi and Paratyphi A infections in 75 endemic countries, 1990-2019: a modelling study

BACKGROUND

Enteric fever, a systemic infection caused by Salmonella enterica serovars Typhi and Paratyphi A, remains a major cause of morbidity and mortality in low-income and middle-income countries. Enteric fever is preventable through the provision of clean water and adequate sanitation and can be successfully treated with antibiotics. However, high levels of antimicrobial resistance (AMR) compromise the effectiveness of treatment. We provide estimates of the prevalence of AMR S Typhi and S Paratyphi A in 75 endemic countries, including 30 locations without data.

METHODS

We used a Bayesian spatiotemporal modelling framework to estimate the percentage of multidrug resistance (MDR), fluoroquinolone non-susceptibility (FQNS), and third-generation cephalosporin resistance in S Typhi and S Paratyphi A infections for 1403 administrative level one districts in 75 endemic countries from 1990 to 2019. We incorporated data from a comprehensive systematic review, public health surveillance networks, and large multicountry studies on enteric fever. Estimates of the prevalence of AMR and the number of AMR infections (based on enteric fever incidence estimates by the Global Burden of Diseases study) were produced at the country, super-region, and total endemic area level for each year of the study.

FINDINGS

We collated data from 601 sources, comprising 184 225 isolates of S Typhi and S Paratyphi A, covering 45 countries over 30 years. We identified a decline of MDR S Typhi in south Asia and southeast Asia, whereas in sub-Saharan Africa, the overall prevalence increased from 6·0% (95% uncertainty interval 4·3-8·0) in 1990 to 72·7% (67·7-77·3) in 2019. Starting from low levels in 1990, the prevalence of FQNS S Typhi increased rapidly, reaching 95·2% (91·4-97·7) in south Asia in 2019. This corresponded to 2·5 million (1·5-3·8) MDR S Typhi infections and 7·4 million (4·7-11·3) FQNS S Typhi infections in endemic countries in 2019. The prevalence of third-generation cephalosporin-resistant S Typhi remained low across the whole endemic area over the study period, except for Pakistan where prevalence of third-generation cephalosporin resistance in S Typhi reached 61·0% (58·0-63·8) in 2019. For S Paratyphi A, we estimated low prevalence of MDR and third-generation cephalosporin resistance in all endemic countries, but a drastic increase of FQNS, which reached 95·0% (93·7-96·1; 3·5 million [2·2-5·6] infections) in 2019.

INTERPRETATION

This study provides a comprehensive and detailed analysis of the prevalence of MDR, FQNS, and third-generation cephalosporin resistance in S Typhi and S Paratyphi A infections in endemic countries, spanning the last 30 years. Our analysis highlights the increasing levels of AMR in this preventable infection and serves as a resource to guide urgently needed public health interventions, such as improvements in water, sanitation, and hygiene and typhoid fever vaccination campaigns.

FUNDING

Fleming Fund, UK Department of Health and Social Care; Wellcome Trust; and Bill and Melinda Gates Foundation.

Loss of function of metabolic traits in typhoidal Salmonella without apparent genome degradation

Salmonella enterica serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars are exclusively adapted to the human host, where they can cause life-long persistent infection. A distinct feature of these serovars is the presence of a relatively high number of degraded coding sequences coding for metabolic pathways, most likely a consequence of their adaptation to a single host. As a result of convergent evolution, these serovars shared many of the degraded coding sequences although often affecting different genes in the same metabolic pathway. However, there are several coding sequences that appear intact in one serovar while clearly degraded in the other, suggesting differences in their metabolic capabilities. Here, we examined the functionality of metabolic pathways that appear intact in S . Typhi but that show clear signs of degradation in S . Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in S. Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. Thus, the inability of S . Typhi to metabolize Glucose-6-Phosphate or 3-phosphoglyceric acid is due to the silencing of the expression of the genes encoding the transporters for these compounds due to point mutations in the transcriptional regulatory proteins. In contrast, its inability to utilize glucarate or galactarate is due to the presence of point mutations in the transporter and enzymes necessary for the metabolism of these sugars. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted Salmonella enterica serovars and highlight a limitation of bioinformatic approaches to predict metabolic capabilities.

Large outbreak of typhoid fever on a river cruise ship used as accommodation for asylum seekers, the Netherlands, 2022

On 6 April 2022, the Public Health Service of Kennemerland, the Netherlands, was notified about an outbreak of fever and abdominal complaints on a retired river cruise ship, used as shelter for asylum seekers. The diagnosis typhoid fever was confirmed on 7 April. An extensive outbreak investigation was performed. Within 47 days, 72 typhoid fever cases were identified among asylum seekers (n = 52) and staff (n = 20), of which 25 were hospitalised. All recovered after treatment. Consumption of food and tap water on the ship was associated with developing typhoid fever. The freshwater and wastewater tanks shared a common wall with severe corrosion and perforations, enabling wastewater to leak into the freshwater tank at high filling levels. Salmonella Typhi was cultured from the wastewater tank, matching the patient isolates. In the freshwater tank, Salmonella species DNA was detected by PCR, suggesting the presence of the bacterium and supporting the conclusion of contaminated freshwater as the probable source of the outbreak. Outbreaks of uncommon infections may occur if persons from endemic countries are accommodated in crowded conditions. Especially when accommodating migrants on ships, strict supervision on water quality and technical installations are indispensable to guarantee the health and safety of the residents.

A phase II clinical trial of a Vi-DT typhoid conjugate vaccine in healthy Indonesian adolescents and adults: one-month evaluation of safety and immunogenicity

BACKGROUND

Typhoid fever is commonly found until today, especially in developing countries. It has fatal complications and measures must be taken to reduce the incidence of typhoid. Vaccinations are a key factor in prevention. This is a phase II randomized observer-blind clinical trial on a novel Vi-DT conjugate vaccine on 200 subjects 12 to 40 years of age.

METHODS

Subjects were screened for eligibility after which a blood sample was taken and one dose of vaccine was administered. Investigational vaccine used was Vi-DT and control was Vi-PS. Twenty-eight days after vaccination, subjects visited for providing blood sample to assess immunogenicity and were asked about local and systemic adverse reactions that occurred in the first 28 days.

RESULTS

Subjects had minor adverse reactions. Pain was the most common local reaction. Muscle pain was the most common systemic reaction. There were no serious adverse events up to 28 days post vaccination. Seroconversion rates were 100% in the Vi-DT group and 95.96% in the Vi-PS group. Post vaccination GMTs were increased in both groups but it was significantly higher in the Vi-DT group (p < 0.001).

CONCLUSIONS

Vi-DT typhoid conjugate vaccine is safe and immunogenic in healthy Indonesian subjects 12 to 40 years.

TRIAL REGISTRATION

Approved by ClinicalTrials.gov.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03460405. Registered on 09/03/2018. URL: https://clinicaltrials.gov/ct2/show/NCT03460405 .

A description of a pre-emptive typhoid Vi capsular polysaccharide vaccination campaign after the 2015 earthquake in Nepal and vaccine effectiveness evaluation

BACKGROUND

A 7.8 R scale earthquake hit Nepal in April 2015 and caused about 9000 deaths along with damage to infrastructure, including the water and sewage system. Bhaktapur was one of the highly affected districts. A typhoid vaccination campaign (pre-emptive) was carried out among children who were living in the temporary shelters in this district. The assessment of vaccine effectiveness after a pre-emptive typhoid vaccine campaign following an earthquake has previously not been attempted in Nepal.

OBJECTIVE

To describe the pre-emptive typhoid Vi capsular polysaccharide vaccination campaign and an evaluation of the vaccine effectiveness.

METHODS

We conducted a pre-emptive typhoid Vi capsular polysaccharide vaccination campaign among children between 2 and 15 years of age dwelling in 23 temporary shelters in Bhaktapur district after the earthquake. Surveillance of clinical typhoid was carried out from 2014 to 2017 in Siddhi Memorial Hospital, the only hospital for children in the district. We calculated vaccine effectiveness using a case-control study design (clinical typhoid as cases and chest x-ray confirmed pneumonia as controls).

RESULTS

Three thousand nine hundred sixteen children of age 2-15 years residing in the 23 temporary shelters in Bhaktapur received the typhoid Vi capsular polysaccharide vaccine between July and December 2015. 2193 children of age 2-15 years were admitted to the hospital during the study period and 260 (11.9%) were diagnosed with clinical typhoid. The numbers of children admitted with clinical typhoid decreased over the study period (105 in 2014 and 47 in 2017; P = 0.001). Overall vaccine effectiveness was calculated at 52% (95% CI -46 to 85%), and it was 87% (95% CI -25 to 99) among children less than 5 years of age.

CONCLUSIONS

We successfully conducted a pre-emptive vaccination campaign against typhoid after the 2015 Nepal earthquake. The pre-emptive vaccination campaign appeared to be more effective among children less than 5 years of age. Further studies are needed to assess the effectiveness of pre-emptive use of typhoid vaccines in the emergency situations. We highlight the challenges of calculating vaccine effectiveness of a typhoid vaccine in an emergency setting.

Salmonellosis: An Overview of Epidemiology, Pathogenesis, and Innovative Approaches to Mitigate the Antimicrobial Resistant Infections

Salmonella is a major foodborne pathogen and a leading cause of gastroenteritis in humans and animals. Salmonella is highly pathogenic and encompasses more than 2600 characterized serovars. The transmission of Salmonella to humans occurs through the farm-to-fork continuum and is commonly linked to the consumption of animal-derived food products. Among these sources, poultry and poultry products are primary contributors, followed by beef, pork, fish, and non-animal-derived food such as fruits and vegetables. While antibiotics constitute the primary treatment for salmonellosis, the emergence of antibiotic resistance and the rise of multidrug-resistant (MDR) Salmonella strains have highlighted the urgency of developing antibiotic alternatives. Effective infection management necessitates a comprehensive understanding of the pathogen's epidemiology and transmission dynamics. Therefore, this comprehensive review focuses on the epidemiology, sources of infection, risk factors, transmission dynamics, and the host range of Salmonella serotypes. This review also investigates the disease characteristics observed in both humans and animals, antibiotic resistance, pathogenesis, and potential strategies for treatment and control of salmonellosis, emphasizing the most recent antibiotic-alternative approaches for infection control.

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

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

[Modern concept of differential diagnosis of colitis: from G.F. Lang to the present day. A review]

The aim of the article is to improve the differential diagnosis of specific and nonspecific inflammatory bowel diseases. In Russia, this scientific direction is associated with the name of G.F. Lang, who performed in 1901-1902 the study "On ulcerative inflammation of the large intestine caused by balantidiasis". The etiology of specific colitis is associated with infection with parasites, bacteria and viruses that cause inflammation of the intestinal wall, diarrhea, often with an admixture of mucus, pus and blood. Specific colitis (SC) may be accompanied by fever, abdominal pain, and tenesmus. Bacterial colitis is commonly caused by Salmonella, Shigella, Escherichia coli, Clostridium difficile, Campylobacter jejuni, Yersinia enterocolitica, and Mycobacterium tuberculosis. Viral colitis is caused by rotavirus, adenovirus, cytomegalovirus, and norovirus. Parasitic colitis can be caused by Entamoeba histolytica and balantidia. In gay people, SC can cause sexually transmitted infections: Neisseria gonorrhoeae, Chlamydia trachomatis, and treponema pallidum, affecting the rectum. Stool microscopy, culture, and endoscopy are used to establish the diagnosis. Stool culture helps in the diagnosis of bacterial colitis in 50% of patients, and endoscopic studies reveal only nonspecific pathological changes. Differential diagnosis of SC should be carried out with immune-inflammatory bowel diseases (ulcerative colitis, Crohn's disease, undifferentiated colitis), radiation colitis and other iatrogenic bowel lesions. The principles of diagnosis and therapy of inflammatory bowel diseases associated with various etiological.

Typhoid fever

Typhoid fever is an invasive bacterial disease associated with bloodstream infection that causes a high burden of disease in Africa and Asia. Typhoid primarily affects individuals ranging from infants through to young adults. The causative organism, Salmonella enterica subsp. enterica serovar Typhi is transmitted via the faecal-oral route, crossing the intestinal epithelium and disseminating to systemic and intracellular sites, causing an undifferentiated febrile illness. Blood culture remains the practical reference standard for diagnosis of typhoid fever, where culture testing is available, but novel diagnostic modalities are an important priority under investigation. Since 2017, remarkable progress has been made in defining the global burden of both typhoid fever and antimicrobial resistance; in understanding disease pathogenesis and immunological protection through the use of controlled human infection; and in advancing effective vaccination programmes through strategic multipartner collaboration and targeted clinical trials in multiple high-incidence priority settings. This Primer thus offers a timely update of progress and perspective on future priorities for the global scientific community.

The diverse landscape of AB5-type toxins

AB5-type toxins are a group of secreted protein toxins that are central virulence factors for bacterial pathogens such as Shigella dysenteriae, Vibrio cholerae, Bordetella pertussis, and certain lineages of pathogenic Escherichia coli and Salmonella enterica. AB5 toxins are composed of an active (A) subunit that manipulates host cell biology in complex with a pentameric binding/delivery (B) subunit that mediates the toxin's entry into host cells and its subsequent intracellular trafficking. Broadly speaking, all known AB5-type toxins adopt similar structural architectures and employ similar mechanisms of binding, entering and trafficking within host cells. Despite this, there is a remarkable amount of diversity amongst AB5-type toxins; this includes different toxin families with unrelated activities, as well as variation within families that can have profound functional consequences. In this review, we discuss the diversity that exists amongst characterized AB5-type toxins, with an emphasis on the genetic and functional variability within AB5 toxin families, how this may have evolved, and its impact on human disease.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pangenome diversification and resistance gene characterization in Salmonella Typhi prioritized RfaJ as a significant therapeutic marker

BACKGROUND

Salmonella Typhi stands as the etiological agent responsible for the onset of human typhoid fever. The pressing demand for innovative therapeutic targets against S. Typhi is underscored by the escalating prevalence of this pathogen and the severe nature of its infections. Consequently, this study employs pangenome analysis to scrutinize 119 S. Typhi-resistant strains, aiming to identify the most promising therapeutic targets originating from its core genome.

RESULTS

Subtractive genomics was employed to systematically eliminate non-homologous (n=1147), essential (n=551), drug-like (n=80), and pathogenicity-related (n=18) proteins from the initial pool of 3351 core genome proteins. Consequently, lipopolysaccharide 1,2-glucosyltransferase RfaJ was designated as the optimal pharmacological target due to its potential versatility. Furthermore, a compendium of 9000 FDA-approved compounds was repurposed for evaluation against the RfaJ drug target, with the specific intent of prioritizing novel, high-potency therapeutic candidates for combating S. Typhi. Ultimately, four compounds, namely DB00549 (Zafirlukast), DB15637 (Fluzoparib), DB15688 (Zavegepant), and DB12411 (Bemcentinib), were singled out as potential inhibitors based on the ligand-protein binding affinity (indicated by the lowest anticipated binding energy) and the overall stability of these compounds. Notably, molecular dynamics simulations, conducted over a 50 nanosecond interval, convincingly demonstrated the stability of these compounds in the context of the RfaJ protein.

CONCLUSION

In summary, the present findings hold significant promise as an initial stride in the broader drug discovery endeavor against S. Typhi infections. However, the experimental validation of the identified drug target and drug candidate is further required to increase the effectiveness of the applied methodology.

Vaccine value profile for Salmonella enterica serovar Paratyphi A

In Asia, there are an estimated 12 million annual cases of enteric fever, a potentially fatal systemic bacterial infection caused by Salmonella enterica serovars Typhi (STy) and Paratyphi A (SPA). The recent availability of typhoid conjugate vaccines (TCV), an increasing incidence of disease caused by SPA and growing antimicrobial resistance (AMR) across the genus Salmonella makes a bivalent STy/SPA vaccine a useful public health proposition. The uptake of a stand-alone paratyphoid vaccine is likely low thus, there is a pipeline of bivalent STy/SPA candidate vaccines. Several candidates are close to entering clinical trials, which if successful should facilitate a more comprehensive approach for enteric fever control. Additionally, the World Health Organization (WHO) has made advancing the development of vaccines that protect young children and working aged adults against both agents of enteric fever a priority objective. This "Vaccine Value Profile" (VVP) addresses information related predominantly to invasive disease caused by SPA prevalent in Asia. Information is included on stand-alone SPA candidate vaccines and candidate vaccines targeting SPA combined with STy. Out of scope for the first version of this VVP is a wider discussion on the development of a universal Salmonella combination candidate vaccine, addressing both enteric fever and invasive non-typhoidal Salmonella disease, for use globally. This VVP is a detailed, high-level assessment of existing, publicly available information to inform and contextualize the public health, economic, and societal potential of pipeline vaccines and vaccine-like products for SPA. Future versions of this VVP will be updated to reflect ongoing activities such as vaccine development strategies and "Full Vaccine Value Assessment" that will inform the value proposition of an SPA vaccine. This VVP was developed by an expert working group from academia, non-profit organizations, public-private partnerships, and multi-lateral organizations as well as in collaboration with stakeholders from the WHO South-East Asian Region. All contributors have extensive expertise on various elements of the VVP for SPA and collectively aimed to identify current research and knowledge gaps.

Assessing the global risk of typhoid outbreaks caused by extensively drug resistant Salmonella Typhi

Since its emergence in 2016, extensively drug resistant (XDR) Salmonella enterica serovar Typhi (S. Typhi) has become the dominant cause of typhoid fever in Pakistan. The establishment of sustained XDR S. Typhi transmission in other countries represents a major public health threat. We show that the annual volume of air travel from Pakistan strongly discriminates between countries that have and have not imported XDR S. Typhi in the past, and identify a significant association between air travel volume and the rate of between-country movement of the H58 haplotype of S. Typhi from fitted phylogeographic models. Applying these insights, we analyze flight itinerary data cross-referenced with model-based estimates of typhoid fever incidence to identify the countries at highest risk of importation and sustained onward transmission of XDR S. Typhi. Future outbreaks of XDR typhoid are most likely to occur in countries that can support efficient local S. Typhi transmission and have strong travel links to regions with ongoing XDR typhoid outbreaks (currently Pakistan). Public health activities to track and mitigate the spread of XDR S. Typhi should be prioritized in these countries.

The pregnant traveller: An overview of common preventable infections

Pregnant travellers are often unaware of the various infections that can be acquired during travel and that pregnant people may be at increased risk of severe disease compared to their non-pregnant counterparts. Pregnant people often seek pre-travel counselling from their obstetrician or primary care physicians, who may not be well versed in travel medicine. This paper aims to provide information for maternity care providers regarding important travel-related food, water and mosquito-borne illnesses, including their prevention and treatment methods, equipping maternity care providers to confidently counsel prospective travellers during pregnancy.

Antimicrobial resistant strains of Salmonella typhi: The role of illicit antibiotics sales, misuse, and self-medication practices in Pakistan

Typhoid fever, caused by the bacterium Salmonella typhi, is an often-fatal illness prevalent in Africa and South Asia. The illness has seen an alarming rise in multi-drug-resistant (MDR) and extensive drug-resistant (XDR) strains, particularly in Pakistan. The MDR strain links to the H58 haplotype, and its XDR variant exhibits fluoroquinolone resistance due to an IncY plasmid. The increasing prevalence of these resistant strains is concerning, given the global antimicrobial resistance (AMR) issue. Causes include misuse of antibiotics in self-limiting infections and an unregulated drug market. Pakistan's Sindh province first reported the XDR typhoid strain, highlighting the urgent need to investigate the relationship between AMR development and external factors. This narrative review intends to scrutinize the state of AMR in Pakistan, considering illicit drug sales, healthcare worker education gaps, and self-medication behaviors.

Salmonella infection among the pediatric population at a tertiary care children's hospital in central Nepal: a retrospective study

Background

Typhoid fever, an infective bacterial disease, is capable of causing fatal systemic infection in humans, and in an era of antimicrobial resistance, it has become of public health importance. This study aimed to investigate the laboratory diagnosis of Salmonella bloodstream infection, its serotype, antimicrobial resistance pattern, and seasonal variation at a tertiary care children's hospital.

Methods

We undertook a retrospective, cross-sectional study by reviewing hospital-based laboratory records of patients whose blood culture samples were submitted from the outpatient department to the laboratory of a tertiary care children's hospital in Kathmandu, Nepal, from January 2017 to January 2019.

Results

Among the total blood culture samples obtained (n = 39,771), bacterial isolates (n = 1,055, 2.65%) belonged either to the Genus Enterobacteriaceae or Genus Acinetobacter. Altogether (n = 91, 8.63%), isolates were positive for Salmonella spp., which were further identified as Salmonella enterica subsp. enterica ser. Typhi (n = 79, 7.49%), Salmonella enterica subsp. enterica ser. Paratyphi A (n = 11, 1.04%), and Salmonella enterica subsp. enterica ser. Paratyphi B (n = 1, 0.1%). The median age of patients was 6  years (IQR: 4-9), with male and female patients constituting (n = 53, 58.24%; OR, 1.0; 95% CI, 0.60-1.67) and (n = 38, 41.76%; OR, 0.98; 95% CI, 0.49-2.05) cases, respectively. The disease was observed throughout the year, with a high prevalence toward the spring season (March-May). An antibiogram showed resistance more toward nalidixic acid with S. Typhi, comprising half the isolates (n = 52, 65.82%; p = 0.11). Resistance toward β-lactams with β-lactamase inhibitors (amoxicillin/clavulanate; 1.27%) was seen in a single isolate of S. Typhi. The multidrug resistance pattern was not pronounced. The multiple antibiotic resistance (MAR) index was in the range between 0.14 and 0.22 in S. Typhi and 0.22 and 0.23 in S. Paratyphi.

Conclusion

Salmonella Typhi was the predominant ser. Infection was common among children between 1 and 5 years of age, showing male predominance and with the spring season contributing to a fairly higher number of cases. Antimicrobial susceptibility testing of S. Typhi showed more resistance toward nalidixic acid, with only a single isolate resistant to β-lactamase inhibitors (amoxicillin/clavulanate). Alarming multidrug resistance patterns were not observed. The MAR index in this study indicates the importance of the judicious use of antimicrobials and hospital infection prevention and control practices.

Clinical and microbiological characterization of Salmonella spp. isolates from patients treated in a university hospital in South America between 2012-2021: a cohort study

BACKGROUND

Salmonellosis is a major cause of morbidity and mortality and one of the most frequent etiologies of diarrhea in the world. Mortality due to Salmonellosis in Latin America still poorly understood, and there is a lack of studies that evaluate resistance and clinical manifestations. The aims of this study were to characterize patients infected with Salmonella spp. seen in a university hospital in Colombia between 2012 and 2021, to evaluate trends in antibiotic resistance and to determine the proportion of overall mortality and related factors.

METHODS

Retrospective observational study. All patients with microbiological diagnosis of Salmonella spp. were included. The sociodemographic, clinical and microbiological characteristics were described, and the proportion of antibiotic resistant isolates per year was estimated. The prevalence of mortality according to age groups was calculated. Log binomial regression models were used to establish factors associated with mortality.

RESULTS

Five hundred twenty-two patients were analyzed. Salmonellosis accounted for 0.01% of all medical consultations. The median age was 16 years old. The most common clinical presentation was gastroenteric syndrome (77.1%) and symptoms included diarrhea (79.1%), fever (66.7%), abdominal pain (39.6%) and vomiting (35.2%). Of the Salmonella spp. isolates, 78.2% were not classified, 19.1% corresponded to non-typhoidal Salmonella and 2.7% to Salmonella typhi. Mortality occurs in 4.02% of the patients and was higher in patients with hematologic malignancy (11.6%). When analyzing by age group, the proportion of deaths was 2.8% in patients aged 15 years or younger, while in those older than 15 years it was 5.4%. Factors associated to mortality where bacteremia (aPR = 3.41 CI95%: 1.08-10.76) and to require treatment in the ICU (aPR = 8.13 CI95%: 1.82-37.76). In the last 10 years there has been a steady increase in resistance rates to ciprofloxacin, ampicillin, ampicillin/sulbactam and ceftriaxone, reaching rates above 60% in recent years.

CONCLUSIONS

Despite improved availability of antibiotics for the treatment of salmonellosis in the past decades, mortality due to salmonellosis continues occurring in children and adults, mainly in patients with hematological malignancies and bacteremia. Antibiotic resistance rates have increased significantly over the last 10 years. Public health strategies for the control of this disease should be strengthened, especially in vulnerable populations.