A study of typhoid fever in five Asian countries: disease burden and implications for controls

Achieving accurate laboratory diagnosis of typhoid fever: a review and meta-analysis of TUBEX® TF clinical performance

This review discusses currently available serological diagnostic methods for typhoid fever with a focus on the clinical utility of TUBEX® TF as an alternative to the Widal or Typhidot test. A literature search was conducted in PubMed for related publications written in English. A qualitative analysis was done to determine various serological tests used for typhoid fever diagnosis with emphasis on TUBEX® TF in comparison to the Widal of Typhidot test. Further, a meta-analysis was performed to obtain a pooled estimate of diagnostic accuracy (sensitivity and specificity) using different analysis models. A total of sixteen studies was included in the qualitative analysis. Further screening of these studies yielded ten studies that were used for the meta-analysis. The sensitivity/specificity range of different commonly used serological tests in typhoid patients is between 55-100%/58-100% for TUBEX® TF, 54-67%/54-95% for Typhidot, and 32-95%/4-98% for the Widal test. As for the pooled meta-analysis estimates, the TUBEX® TF showed superior results when differentiating individuals with febrile illness of unknown origin from those with typhoid fever. Overall, the results of this review and meta-analysis suggest that the TUBEX® TF is more advantageous to use as a serological test for typhoid fever diagnosis due its accuracy and simplicity. However, further studies are still needed to validate our results.

Determining the Best Immunization Strategy for Protecting African Children Against Invasive Salmonella Disease

Background

The World Health Organization recently prequalified a typhoid conjugate vaccine (TCV), recommending its use in persons ≥6 months to 45 years residing in typhoid fever (TF)-endemic areas. We now need to consider how TCVs can have the greatest impact in the most vulnerable populations.

Methods

The Typhoid Fever Surveillance in Africa Program (TSAP) was a blood culture-based surveillance of febrile patients from defined populations presenting at healthcare facilities in 10 African countries. TF and invasive non-typhoidal Salmonella (iNTS) disease incidences were estimated for 0-10 year-olds in one-year age increments.

Results

Salmonella Typhi and iNTS were the most frequently isolated pathogens; 135 and 94 cases were identified, respectively. Analysis from three countries was excluded (incomplete person-years of observation (PYO) data). Thirty-seven of 123 TF cases (30.1%) and 71/90 iNTS disease cases (78.9%) occurred in children aged <5 years. No TF and 8/90 iNTS infections (8.9%) were observed in infants aged <9 months. The TF incidences (/100 000 PYO) for children aged <1 year and 1 to <2 years were 5 and 39, respectively; the highest incidence was 304 per 100 000 PYO in 4 to <5 year-olds. The iNTS disease incidence in the defined age groups ranged between 81 and 233 per 100 000 PYO, highest in 1 to <2 year-olds. TF and iNTS disease incidences were higher in West Africa.

Conclusions

High burden of TF detected in young children strengthens the need for TCV introduction. Given the concurrent iNTS disease burden, development of a trivalent vaccine against S. Typhi, S. Typhimurium, and S. Enteritidis may be timely in this region.

Sensitivity Pattern Of Salmonella typhi And Paratyphi A Isolates To Chloramphenicol And Other Anti-Typhoid Drugs: An In Vitro Study

Purpose

To investigate the antimicrobial sensitivity pattern of commonly prescribed antimicrobials (chloramphenicol, cefixime, ofloxacin, azithromycin, and ceftriaxone) against Salmonella enterica isolates.

Methods

Blood culture positive isolates of S. typhi and S. paratyphi A (N = 251) received at Metropolis Healthcare Limited (Mumbai, India) from four zones of India (North, South, West, and East) between April and August 2018 were tested for antimicrobial susceptibility by E-test method. Based on the minimum inhibitory concentration (MIC), the organism was categorized as sensitive, intermediate, and resistant against the respective antibiotics as per Clinical and Laboratory Standards Institute criteria 2018.

Results

Out of 251 Salmonella isolates, 192 (76.5%) were S. typhi and 59 (23.5%) were S. paratyphi A. All 251 (100%) Salmonella isolates were sensitive to cefixime, ceftriaxone, and azithromycin; 237/251 (94.4%) isolates to chloramphenicol and only 9/251 (3.6%) isolates were sensitive to ofloxacin. Based on average MIC and MIC breakpoints, Salmonella isolates were found to be sensitive to chloramphenicol (MIC: 3.89±6.94 µg/mL), cefixime (MIC: 0.13±0.11 µg/mL), azithromycin (MIC: 3.32±2.19 µg/mL), and ceftriaxone (MIC: 0.11±0.18 µg/mL) and resistant to ofloxacin (MIC: 2.95±6.06 µg/mL). More than 20% of Salmonella isolates had MICs of chloramphenicol as 1.5 µg/mL (27.85% isolates) and 2 µg/mL (29.53% isolates).

Conclusion

Our study confirms the re‑emergence of susceptibility of Salmonella isolates to chloramphenicol. Further, the concern about fluoroquinolone-decreased susceptibility as indicated by the intermediate susceptibility or resistance was reiterated in this study. Though cefixime, azithromycin, and ceftriaxone showed susceptibility, the possibility of antibiotic resistance with the irrational use of these antibiotics cannot be deterred. This study thus emphasizes the need for continuous evaluation and judicious use of antimicrobials, considering the ever-changing landscape.

Immunogenicity, safety and reactogenicity of a Phase II trial of Vi-DT typhoid conjugate vaccine in healthy Filipino infants and toddlers: A preliminary report

BACKGROUND

Typhoid fever remains an important public health problem in developing countries and is endemic in many parts of Asia and Africa where the incidence of disease typically peaks in school-aged children. Age restrictions and other limitations of existing oral live-attenuated typhoid and parenteral Vi polysaccharide vaccines have triggered the development of Vi conjugate vaccines with improved immunological properties, use in younger age range, and longer durability of protection. We present the safety, reactogenicity, and immunogenicity data from a Phase II study after a single dose of Vi polysaccharide conjugated to diphtheria toxoid (Vi-DT) conducted in 6-23-month old Filipino children.

METHODS

This is a randomized, observer-blinded Phase II study to assess the immunogenicity, safety and reactogenicity of Vi-DT compared to placebo, conducted in Muntinlupa City, The Philippines. Participants aged 6-23 months were enrolled and randomized to Vi-DT (25 µg) or placebo (0.9% sodium chloride) and evaluated for immunogenicity and overall safety 28 days post vaccination.

RESULTS

A total of 285 participants were enrolled and age-stratified: 6 to < 9 months, 9-12 months, and 13-23 months. Seventy-six (76) participants received Vi-DT and 19 received placebo per each strata. All participants seroconverted after a single dose of Vi-DT versus 7% of placebo recipients. Anti-Vi IgG GMT was 444.38 [95% CI (400.28; 493.34)] after a single dose of Vi-DT; there was no change in GMT after placebo administration, 0.41 [95% CI (0.33; 0.51), p < 0.0001]. A similar pattern of immunogenicity was reported across all age strata. The vaccine reported to be safe and well tolerated.

CONCLUSIONS

Vi-DT vaccine was immunogenic, safe, and well tolerated in children aged 6-23 months. ClinicalTrials.gov registration number: NCT03527355.

High Rates of Enteric Fever Diagnosis and Lower Burden of Culture-Confirmed Disease in Peri-urban and Rural Nepal

Background

In South Asia, data on enteric fever are sparse outside of urban areas. We characterized enteric fever diagnosis patterns and the burden of culture-confirmed cases in peri-urban and rural Nepal.

Methods

We used national reports to estimate enteric fever diagnosis rates over 20 years (1994-2014) and conducted a prospective study of patients presenting with a >72-hour history of fever to 4 peri-urban and rural healthcare facilities (during August 2013-June 2016). We compared clinical characteristics of patients with culture-confirmed Salmonella Typhi or Paratyphi infection to those of patients without enteric fever. We used generalized additive models with logistic link functions to evaluate associations of age and population density with culture positivity.

Results

National rates of enteric fever diagnosis were high, reaching 18.8 cases per 1000 during 2009-2014. We enrolled 4309 participants with acute febrile illness. Among those with a provisional clinical diagnosis, 55% (1334 of 2412) received a diagnosis of enteric fever; however, only 4.1% of these had culture-confirmed typhoidal Salmonella infection. Culture positivity was highest among young adults and was strongly associated with higher population density (P < .001).

Conclusions

Enteric fever diagnosis rates were very high throughout Nepal, but in rural settings, few patients had culture-confirmed disease. Expanded surveillance may inform local enteric fever treatment and prevention strategies.

Phase I of the Surveillance for Enteric Fever in Asia Project (SEAP): An Overview and Lessons Learned

Objective

The objective of Phase I of the Surveillance for Enteric Fever in Asia Project (SEAP), a multiphase surveillance study characterizing the burden of disease in South Asia, was to inform data collection for prospective surveillance and to capture clinical aspects of disease.

Methods

Through a retrospective record review conducted at hospitals in Bangladesh, India, Nepal, and Pakistan, we examined laboratory and clinical records to assess the culture positivity rate for Salmonella Typhi and Salmonella Paratyphi, age and sex distribution, and antimicrobial susceptability in each country.

Results

Of all blood cultures performed in Bangladesh, India, Nepal, and Pakistan, 1.5%, 0.43%, 2%, and 1.49%, respectively, were positive for S. Typhi and 0.24%, 0.1%, 0.5%, and 0.67%, respectively, were positive for S. Paratyphi. A higher proportion of laboratory-confirmed infections in Bangladesh and Pakistan were aged ≤5 years, while India and Nepal had a higher proportion of participants aged 15–25 years. In all countries, the sex of the majority of participants was male. The majority of isolates in all countries were resistant to fluoroquinolones, with a high proportion also resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole.

Discussion

Enteric fever remains endemic in South Asia. Data generated by this study can help inform strategies for implementation and evaluation of prevention and control measures.

A Retrospective Review of Hospital-Based Data on Enteric Fever in India, 2014-2015

Background

Enteric fever remains a threat to many countries with minimal access to clean water and poor sanitation infrastructure. As part of a multisite surveillance study, we conducted a retrospective review of records in 5 hospitals across India to gather evidence on the burden of enteric fever.

Methods

We examined hospital records (laboratory and surgical registers) from 5 hospitals across India for laboratory-confirmed Salmonella Typhi or Salmonella Paratyphi cases and intestinal perforations from 2014–2015. Clinical data were obtained where available. For laboratory-confirmed infections, we compared differences in disease burden, age, sex, clinical presentation, and antimicrobial resistance.

Results

Of 267536 blood cultures, 1418 (0.53%) were positive for S. Typhi or S. Paratyphi. Clinical data were available for 429 cases (72%); a higher proportion of participants with S. Typhi infection were hospitalized, compared with those with S. Paratyphi infection (44% vs 35%). We observed resistance to quinolones among 82% of isolates, with cases of cephalosporin resistance (1%) and macrolide resistance (9%) detected. Of 94 participants with intestinal perforations, 16 (17%) had a provisional, final, or laboratory-confirmed diagnosis of enteric fever.

Discussion

Data show a moderate burden of enteric fever in India. Enteric fever data should be systematically collected to facilitate evidence-based decision-making by countries for typhoid conjugate vaccines.

A Retrospective Study of Laboratory-Based Enteric Fever Surveillance, Pakistan, 2012-2014

Introduction

The Surveillance for Enteric Fever in Asia Project (SEAP) is a multisite surveillance study designed to capture morbidity and mortality burden of enteric fever (typhoid and paratyphoid) in Bangladesh, Nepal, and Pakistan. We aim to describe enteric fever disease burden, severity of illness, and antimicrobial resistance trends in Pakistan.

Methods

In this retrospective, cross-sectional study, laboratory records of hospitalized patients who received a blood culture in any of 3 Aga Khan University hospitals in Karachi and Hyderabad, Pakistan, from 2012 to 2014 were reviewed. A case was defined as having a positive blood culture for Salmonella Typhi (S. Typhi) or Salmonella Paratyphi (S. Paratyphi). Antimicrobial sensitivity patterns were characterized for all S. Typhi and S. Paratyphi isolates. Medical records were available for abstraction (demographics, clinical features, complications) only among hospitalized cases.

Results

Of the 133017 blood cultures completed during the study period, 2872 (2%) were positive—1979 (69%) for S. Typhi and 893 (31%) for S. Paratyphi. Fluoroquinolone resistance was present in >90% of both the S. Typhi and the S. Paratyphi isolates; almost none of the isolates were resistant to cephalosporins. Multidrug resistance (resistance to ampicillin, chloramphenicol, and cotrimoxazole) was observed in 1035 (52%) S. Typhi isolates and 14 (2%) S. Paratyphi isolates. Among S. Typhi and S. Paratyphi isolates, 666 (23%) were linked to hospitalized patients with medical records. Of the 537 hospitalized S. Typhi cases, 280 (52%) were aged 5–15 years, 133 (25%) were aged 2–4 years, 114 (21%) were aged >15 years, and 10 (2%) were aged 0–1 years. Among the 129 hospitalized S. Paratyphi cases, 73 (57%) were aged >15 years, 41 (32%) were aged 5–15 years, 13 (10%) were aged 2–4 years, and 2 (2%) were aged 0–1 years. Significant differences in symptomology between S. Typhi and S. Paratyphi cases were observed for nausea/vomiting, diarrhea, loss of appetite, and headache. Leukopenia, thrombocytopenia, and encephalopathy were the most commonly reported complications among enteric fever cases. No deaths were reported.

Conclusion

Evidence of high antimicrobial resistance levels and disease severity support the need for continued surveillance and improved diagnostics for typhoid. Further prospective studies on vaccination as a tool for prevention of enteric fever in Pakistan are needed to inform disease intervention strategies.

Evaluation of a Salmonella Strain Isolated from Honeybee Gut as a Potential Live Oral Vaccine Against Lethal Infection of Salmonella Typhimurium

In this research, Salmonella species were isolated from the animal, insect and human enteric sources in Faisalabad, Punjab, Pakistan. These species were characterized by different microbiological and molecular techniques including polymerase chain reaction (PCR) by amplification of the 16S rRNA gene. Furthermore, sequencing of the amplicons confirmed all ten isolates as Salmonella strains. The antigenic cross-reactivity was found maximum between the HB1 (strain isolated from honeybee) antiserum and its antigen with an antibody titer of 1:128, while the HB1 antiserum showed a cross-reactive titer range of 1:8 to 1:64. On the basis of the highest geometric mean titer (GMT) shown by the antiserum of the HB1 antigen, it was selected as the best candidate for a cross-reactive live Salmonella oral antigen. Moreover, the HB1 antigen was used a live oral antigen (1 × 10¹⁰ CFU/ml) in a safety test in rabbits and proved to be avirulent. During the animal trial, three different oral doses of the HB1 live oral antigen were evaluated in four different rabbits' groups (R1, R2, R3, and R4). The dose number 2 of 0.5 ml (two drops orally and repeated after one week) gave the best GMT measured by indirect hemagglutination (IHA) as compared to the other two doses, while R4 group was kept as control. Results of the challenge protection test also validated the efficacy of the double dose of the HB1 live vaccine, which gave the highest survival percentage. Results of this study lay the foundation for a potential cross-reactive live oral Salmonella vaccine that has proved to be immunogenic in rabbits.

In this research, Salmonella species were isolated from the animal, insect and human enteric sources in Faisalabad, Punjab, Pakistan. These species were characterized by different microbiological and molecular techniques including polymerase chain reaction (PCR) by amplification of the 16S rRNA gene. Furthermore, sequencing of the amplicons confirmed all ten isolates as Salmonella strains. The antigenic cross-reactivity was found maximum between the HB1 (strain isolated from honeybee) antiserum and its antigen with an antibody titer of 1:128, while the HB1 antiserum showed a cross-reactive titer range of 1:8 to 1:64. On the basis of the highest geometric mean titer (GMT) shown by the antiserum of the HB1 antigen, it was selected as the best candidate for a cross-reactive live Salmonella oral antigen. Moreover, the HB1 antigen was used a live oral antigen (1 × 10¹⁰ CFU/ml) in a safety test in rabbits and proved to be avirulent. During the animal trial, three different oral doses of the HB1 live oral antigen were evaluated in four different rabbits’ groups (R1, R2, R3, and R4). The dose number 2 of 0.5 ml (two drops orally and repeated after one week) gave the best GMT measured by indirect hemagglutination (IHA) as compared to the other two doses, while R4 group was kept as control. Results of the challenge protection test also validated the efficacy of the double dose of the HB1 live vaccine, which gave the highest survival percentage. Results of this study lay the foundation for a potential cross-reactive live oral Salmonella vaccine that has proved to be immunogenic in rabbits.

Diversity of infectious aetiologies of acute undifferentiated febrile illnesses in south and Southeast Asia: a systematic review

BACKGROUND

Acute undifferentiated febrile illness (AUFI) is caused by a multitude of diverse pathogens, with significant morbidity and mortality in the developing world. The objective of this review was to characterise the diversity and relative importance of common infectious aetiologies of AUFI in South and Southeast Asia.

METHODS

We conducted a comprehensive literature review to identify common aetiologies of AUFI in Asian countries. Four medical and life sciences databases including PubMed, Medline, Embase and Cochrane Central, and Google Scholar were searched for articles published from January 1998 to March 2019.

RESULTS

Forty-three studies met the inclusion criteria. Among AUFI cases, viral aetiologies at 18.5% (14888) were more common than bacterial aetiologies (12.9% [10384]). From 80,554 cases, dengue fever was the most common aetiology (11.8%, 9511), followed by leptospirosis (4.4%, 3549), typhoid (4.0%, 3258), scrub typhus (4.0%, 3243) and influenza other than H1N1 (3.1%, 2514). In both adults and children: dengue fever was the leading cause of AUFI with 16.6% (1928) and 18.7% (1281) of the total cases. In admitted patients, dengue fever was the main cause of AUFI at 16.4% (2377), however leptospirosis at 13.9% (2090) was the main cause of AUFI for outpatients. In South Asia, dengue fever was the main cause of AUFI, causing 12.0% (6821) of cases, whereas in Southeast Asia, leptospirosis was the main diagnosis, causing 12.1% (2861) of cases.

CONCLUSIONS

In this study the most common causes of AUFI were viral, followed by bacterial and protozoal (malaria) infections. Dengue was the commonest virus that caused AUFI while leptospirosis and typhoid were important bacterial infectious causes. Therefore, it is imperative to maintain a sound epidemiological knowledge of AUFI so that evidence-based diagnostic criteria and treatment guidelines can be developed.

Evaluation of a Salmonella Strain Isolated from Honeybee Gut as a Potential Live Oral Vaccine Against Lethal Infection of Salmonella Typhimurium

In this research, Salmonella species were isolated from the animal, insect and human enteric sources in Faisalabad, Punjab, Pakistan. These species were characterized by different microbiological and molecular techniques including polymerase chain reaction (PCR) by amplification of the 16S rRNA gene. Furthermore, sequencing of the amplicons confirmed all ten isolates as Salmonella strains. The antigenic cross-reactivity was found maximum between the HB1 (strain isolated from honeybee) antiserum and its antigen with an antibody titer of 1:128, while the HB1 antiserum showed a cross-reactive titer range of 1:8 to 1:64. On the basis of the highest geometric mean titer (GMT) shown by the antiserum of the HB1 antigen, it was selected as the best candidate for a cross-reactive live Salmonella oral antigen. Moreover, the HB1 antigen was used a live oral antigen (1 × 10¹⁰ CFU/ml) in a safety test in rabbits and proved to be avirulent. During the animal trial, three different oral doses of the HB1 live oral antigen were evaluated in four different rabbits’ groups (R1, R2, R3, and R4). The dose number 2 of 0.5 ml (two drops orally and repeated after one week) gave the best GMT measured by indirect hemagglutination (IHA) as compared to the other two doses, while R4 group was kept as control. Results of the challenge protection test also validated the efficacy of the double dose of the HB1 live vaccine, which gave the highest survival percentage. Results of this study lay the foundation for a potential cross-reactive live oral Salmonella vaccine that has proved to be immunogenic in rabbits.

Invasive Salmonella infections among children in Bintulu, Sarawak, Malaysian Borneo: a 6-year retrospective review

Background

Invasive Salmonella infections result in significant morbidity and mortality in developing countries. In Asia, typhoid and paratyphoid fever are reported to be the major invasive Salmonella infections, while invasive non-typhoidal Salmonella (iNTS) infections are believed to be uncommon. Data from Sarawak, in Malaysian Borneo, are limited.

Methods

A retrospective study identifying all children aged < 15 years with invasive Salmonella infections from 2011 to 2016 was conducted in Bintulu Hospital in Sarawak. Population incidences, clinical and bacterial characteristics were examined.

Results

Forty-four patients were identified during the 6-year study period: 43 had iNTS infection and 1 had typhoid fever. The average annual iNTS incidence was 32.4 per 100,000 children aged < 5 years. None of the children had malaria or HIV infection, and only 7% were severely malnourished. Salmonella Enteritidis and Salmonella Java were the commonest NTS serovars identified. Pneumonia was the most common manifestation of iNTS disease, present in 20 (47%) children. Other manifestations included gastroenteritis, fever without a source, septic arthritis and meningitis. Salmonella Enteritidis was identified in 76% of those with pneumonia, significantly more frequently than in children with other manifestations. Over 25% of children with iNTS developed severe disease and nearly 10% suffered long term morbidity or mortality. While 78% of Salmonella Java isolates were multi-drug resistant, nearly all other isolates were susceptible to most antimicrobials, including ampicillin.

Conclusions

Bintulu Division in Sarawak observed a very high incidence of childhood iNTS infections. Enteric fever was uncommon. The epidemiology of invasive Salmonella infections in Malaysian Borneo differs considerably from that of neighbouring countries in Asia.

Antimicrobial Susceptibility Patterns of Salmonella Species in Southern Pakistan

Introduction

Typhoid fever is a major infectious disease among the pediatric population of Pakistan. With inappropriate use of antibiotics and rising trends of multidrug-resistant (MDR) and extended drug-resistant (XDR) typhoid, it is becoming a public health emergency. This study evaluated the current trends in antibiotic susceptibilities to Salmonella (S) typhi and paratyphi A, B, and C in southern Pakistan.

Materials and methods

This cross-sectional study, conducted in the Pediatrics Department, Civil Hospital, Jamshoro from July to December 2018, included children with S. typhi and S. paratyphi A and B strains isolated from the laboratory-based culture of blood samples.

Results

There were 223 (81.1%) children with S. typhi and 52 (18.9%) with S. paratyphi isolates. Their mean age was 5 ± 3 years. The most common age group with S. typhi strains was two to five years (n = 102; 37.1%). Previous trials of antibiotics were taken by 162 (58.9%) children; 65 (40.1%) of these were physician-prescribed. Cefixime was most commonly taken (66.6%), followed by ciprofloxacin (33.3%). Cefixime and ceftriaxone showed 60.9% and 65.8% sensitivity, respectively. Ciprofloxacin sensitivity was seen in 50.1% S. typhi isolates. There were six (2.6%) cases of MDR typhoid and two (0.9%) cases of XDR typhoid.

Conclusion

Resistance to second-line antityphoid agents is increasing. Therefore, there is a need to modify prescribing behavior. The outbreak of XDR typhoid among children is an alarming public health concern for Pakistan. Widespread antibiotic stewardship programs must be conducted.

Global Typhoid Fever Incidence: A Systematic Review and Meta-analysis

BACKGROUND

Contemporary incidence estimates of typhoid fever are needed to guide policy decisions and control measures and to improve future epidemiological studies.

METHODS

We systematically reviewed 3 databases (Ovid Medline, PubMed, and Scopus) without restriction on age, country, language, or time for studies reporting the incidence of blood culture-confirmed typhoid fever. Outbreak, travel-associated, and passive government surveillance reports were excluded. We performed a meta-analysis using a random-effects model to calculate estimates of pooled incidence, stratifying by studies that reported the incidence of typhoid fever and those that estimated incidence by using multipliers.

RESULTS

Thirty-three studies were included in the analysis. There were 26 study sites from 16 countries reporting typhoid cases from population-based incidence studies, and 17 sites in 9 countries used multipliers to account for underascertainment in sentinel surveillance data. We identified Africa and Asia as regions with studies showing high typhoid incidence while noting considerable variation of typhoid incidence in time and place, including in consecutive years at the same location. Overall, more recent studies reported lower typhoid incidence compared to years prior to 2000. We identified variation in the criteria for collecting a blood culture, and among multiplier studies we identified a lack of a standardization for the types of multipliers being used to estimate incidence.

CONCLUSIONS

Typhoid fever incidence remains high at many sites. Additional and more accurate typhoid incidence studies are needed to support country decisions about typhoid conjugate vaccine adoption. Standardization of multiplier types applied in multiplier studies is recommended.

Incidence of Typhoid and Paratyphoid Fevers Among Adolescents and Adults in Yangon, Myanmar

BACKGROUND

Accurate estimates of typhoid disease burden are needed to guide policy decisions, including on vaccine use. Data on the incidence of enteric fever in Myanmar are scarce. We estimated typhoid and paratyphoid fever incidence among adolescents and adults in Yangon, Myanmar, by combining sentinel hospital surveillance with a healthcare utilization survey.

METHODS

We conducted a population-based household health care utilization survey in the Yangon Region 12 March through 5 April 2018. Multipliers derived from this survey were then applied to hospital-based surveillance of Salmonella Typhi and Paratyphi A bloodstream infections from 5 October 2015 through 4 October 2016 at Yangon General Hospital (YGH) to estimate the incidence of typhoid and paratyphoid fevers among person ≥12 years of age.

RESULTS

A total of 336 households representing 1598 persons were enrolled in the health care utilization survey, and multipliers were derived based on responses to questions about healthcare seeking in the event of febrile illness. Of 671 Yangon residents enrolled over a 1-year period at YGH, we identified 33 (4.9%) with Salmonella Typhi and 9 (1.3%) with Salmonella Paratyphi A bloodstream infection. After applying multipliers, we estimated that the annual incidence of typhoid was 391 per 100 000 persons and paratyphoid was 107 per 100 000 persons.

CONCLUSIONS

Enteric fever incidence is high in Yangon, Myanmar, warranting increased attention on prevention and control, including consideration of typhoid conjugate vaccine use as well as nonvaccine control measures. Research on incidence among infants and children, as well as sources and modes of transmission is needed.

Progress in Typhoid Fever Epidemiology

Salmonella enterica subspecies enterica serovar Typhi (Salmonella Typhi) is the cause of typhoid fever and a human host-restricted organism. Our understanding of the global burden of typhoid fever has improved in recent decades, with both an increase in the number and geographic representation of high-quality typhoid fever incidence studies, and greater sophistication of modeling approaches. The 2017 World Health Organization Strategic Advisory Group of Experts on Immunization recommendation for the introduction of typhoid conjugate vaccines for infants and children aged >6 months in typhoid-endemic countries is likely to require further improvements in our understanding of typhoid burden at the global and national levels. Furthermore, the recognition of the critical and synergistic role of water and sanitation improvements in concert with vaccine introduction emphasize the importance of improving our understanding of the sources, patterns, and modes of transmission of Salmonella Typhi in diverse settings.

Six-month follow up of a randomized clinical trial-phase I study in Indonesian adults and children: Safety and immunogenicity of Salmonella typhi polysaccharide-diphtheria toxoid (Vi-DT) conjugate vaccine

Introduction

There is a high global incidence of typhoid fever, with an annual mortality rate of 200,000 deaths. Typhoid fever also affects younger children, particularly in resource-limited settings in endemic countries. Typhoid vaccination is an important prevention tool against typhoid fever. However, the available polysaccharide typhoid vaccines are not recommended for children under 2 years of age. A new typhoid conjugate Vi-diphtheria toxoid (Vi-DT) vaccine has been developed for infant immunization. We aimed to define the safety and immunogenicity of the Vi-DT vaccine among adults and children in Indonesia.

Methods

An observational, blinded, comparative, randomized, phase I safety study in two age de-escalating cohorts was conducted in East Jakarta, Indonesia, from April 2017 to February 2018. We enrolled 100 healthy subjects in 2 age groups: adults and children (18–40 and 2–5 years old). These groups were randomized into study groups (Vi-DT vaccine), and comparator groups (Vi-polysaccharide (Vi-PS) vaccine and another additional vaccine) which was administered in 4 weeks apart. Subjects were followed up to six months.

Result

One hundred healthy adults and children subjects completed the study. The Vi-DT and Vi-PS vaccines showed no difference in terms of intensity of any immediate local and systemic events within 30 minutes post-vaccination. Overall, pain was the most common local reaction, and muscle pain was the most common systemic reaction in the first 72 hours. No serious adverse events were deemed related to vaccine administration. The first and second doses of the Vi-DT vaccine induced seroconversion and higher geometric mean titers (GMT) in all subjects compared to that of baseline. However, in terms of GMT, the second dose of Vi-DT did not induce a booster response.

Conclusion

The Vi-DT vaccine is safe and immunogenic in adults and children older than two years. A single dose of the vaccine is able to produce seroconversion and high GMT in all individuals.

Prevalence and molecular characterization of Salmonella enterica serovar Typhimurium from ice and beverages in Jakarta, Indonesia

OBJECTIVE

The presence of Salmonella enterica serovar Typhimurium becomes a concern in relation to the safety of drinking water and ice. We detected and enumerated the bacteria from ice and beverages collected from several areas in Jakarta. Most Probable Number (MPN) and multiplex PCR method were used. Three sets of primers were used rfbJ, fliC, and fljB. Two Multiplex PCR's were performed, the first is to detect the presence of Salmonella and the second is to confirm the positive isolate of S. enterica serovar Typhimurium.

RESULTS

A total of 50 beverages and 50 ices were collected MPN result ranged from < 3 to > 11,000 MPN/ml. The highest MPN value > 11,000 MPN/ml. The first Multiplex PCR result from beverages, 58% positively contained Salmonella spp. with amplification of fliB gene and no amplification of rfbJ and fliC genes. For ice samples, 2% positively contained Salmonella spp. with rfbJ gene amplification, 62% fliB gene and no amplification of fliC gene. The second Multiplex PCR results from beverages identified 21 positive isolates of S. enterica serovar Typhimurium. In which, 17 isolates contained fljB gene and 4 isolates contained both fljB and rfbJ genes. From ice, 17 isolates having both rfbJ and fljB genes.

Vaccines for preventing invasive salmonella infections in people with sickle cell disease

BACKGROUND

Salmonella infections are a common bacterial cause of invasive disease in people with sickle cell disease especially children, and are associated with high morbidity and mortality rates. Although available in some centres, people with sickle cell anaemia are not routinely immunized with salmonella vaccines. This is an update of a previously published Cochrane Review.

OBJECTIVES

To determine whether routine administration of salmonella vaccines to people with sickle cell disease reduces the morbidity and mortality associated with infection.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which comprises of references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.We also conducted a search of the LILACS database and the World Health Organization International Clinical Trials Registry Platform (www.who.int/trialsearch) and ClinicalTrials.gov (www.clinicaltrials.gov).Date of most recent searches: 17 October 2018.

SELECTION CRITERIA

We planned to select all randomized controlled trials that compared the use of either the inactivated vaccine or an oral attenuated vaccine with a placebo among people with sickle cell disease. Equally, studies that compared the efficacy of one vaccine type over another were to be selected for the review.

DATA COLLECTION AND ANALYSIS

No trials of salmonella vaccines in people with sickle cell disease were found.

MAIN RESULTS

There is an absence of randomized controlled trial evidence relating to the scope of this review.

AUTHORS' CONCLUSIONS

It is expected that salmonella vaccines may be useful in people with sickle cell disease, especially in resource-poor settings where the majority of those who suffer from the condition are found. Unfortunately, there are no randomized controlled trials on the efficacy and safety of the different types of salmonella vaccines in people with sickle cell disease. We conclude that there is a need for a well-designed, adequately-powered, randomized controlled trial to assess the benefits and risks of the different types of salmonella vaccines as a means of improving survival and decreasing mortality from salmonella infections in people with sickle cell disease. However, we believe that there are unlikely to be any trials published in this area, therefore, this review will no longer be regularly updated.

Modelling the cost-effectiveness of a rapid diagnostic test (IgMFA) for uncomplicated typhoid fever in Cambodia

Typhoid fever is a common cause of fever in Cambodian children but diagnosis and treatment are usually presumptive owing to the lack of quick and accurate tests at an initial consultation. This study aimed to evaluate the cost-effectiveness of using a rapid diagnostic test (RDT) for typhoid fever diagnosis, an immunoglobulin M lateral flow assay (IgMFA), in a remote health centre setting in Cambodia from a healthcare provider perspective. A cost-effectiveness analysis (CEA) with decision analytic modelling was conducted. We constructed a decision tree model comparing the IgMFA versus clinical diagnosis in a hypothetical cohort with 1000 children in each arm. The costs included direct medical costs only. The eligibility was children (≤14 years old) with fever. Time horizon was day seven from the initial consultation. The number of treatment success in typhoid fever cases was the primary health outcome. The number of correctly diagnosed typhoid fever cases (true-positives) was the intermediate health outcome. We obtained the incremental cost effectiveness ratio (ICER), expressed as the difference in costs divided by the difference in the number of treatment success between the two arms. Sensitivity analyses were conducted. The IgMFA detected 5.87 more true-positives than the clinical diagnosis (38.45 versus 32.59) per 1000 children and there were 3.61 more treatment successes (46.78 versus 43.17). The incremental cost of the IgMFA was estimated at $5700; therefore, the ICER to have one additional treatment success was estimated to be $1579. The key drivers for the ICER were the relative sensitivity of IgMFA versus clinical diagnosis, the cost of IgMFA, and the prevalence of typhoid fever or multi-drug resistant strains. The IgMFA was more costly but more effective than the clinical diagnosis in the base-case analysis. An IgMFA could be more cost-effective than the base-case if the sensitivity of IgMFA was higher or cost lower. Decision makers may use a willingness-to-pay threshold that considers the additional cost of hospitalisation for treatment failures.

The Relationship Between Blood Sample Volume and Diagnostic Sensitivity of Blood Culture for Typhoid and Paratyphoid Fever: A Systematic Review and Meta-Analysis

Background

Blood culture is the standard diagnostic method for typhoid and paratyphoid (enteric) fever in surveillance studies and clinical trials, but sensitivity is widely acknowledged to be suboptimal. We conducted a systematic review and meta-analysis to examine sources of heterogeneity across studies and quantified the effect of blood volume.

Methods

We searched the literature to identify all studies that performed blood culture alongside bone marrow culture (a gold standard) to detect cases of enteric fever. We performed a meta-regression analysis to quantify the relationship between blood sample volume and diagnostic sensitivity. Furthermore, we evaluated the impact of patient age, antimicrobial use, and symptom duration on sensitivity.

Results

We estimated blood culture diagnostic sensitivity was 0.59 (95% confidence interval [CI], 0.54-0.64) with significant between-study heterogeneity (I2, 76% [95% CI, 68%-82%]; P < .01). Sensitivity ranged from 0.51 (95% CI, 0.44-0.57) for a 2-mL blood specimen to 0.65 (95% CI, 0.58-0.70) for a 10-mL blood specimen, indicative of a relationship between specimen volume and sensitivity. Subgroup analysis showed significant heterogeneity by patient age and a weak trend towards higher sensitivity among more recent studies. Sensitivity was 34% lower (95% CI, 4%-54%) among patients with prior antimicrobial use and 31% lower after the first week of symptoms (95% CI, 19%-41%). There was no evidence of confounding by patient age, antimicrobial use, symptom duration, or study date on the relationship between specimen volume and sensitivity.

Conclusions

The relationship between the blood sample volume and culture sensitivity should be accounted for in incidence and next-generation diagnostic studies.

Epidemiological and Clinical Features of Salmonella Typhi Infection Among Adult Patients in Qatar: A Hospital-based Study

Objectives

We sought to describe the epidemiological and clinical features of typhoid fever in Qatar.

Methods

We conducted a retrospective study of adult patients treated for typhoid fever at Hamad General Hospital and Alkhor Hospital between 2005 and 2012.

Results

The mean age of the 354 patients enrolled in the study was 28.4±9.3 years; 296 (83.6%) were males. There were 42, 48, 39, 44, 46, 47, 52, and 36 cases of adults with typhoid fever in 2005, 2006, 2007, 2008, 2009, 2010, 2011, and 2012, respectively. Overall, 343 (96.9%) patients had a history of travel to endemic areas. Among them, 93.0% acquired typhoid fever in the Indian subcontinent. Fever was observed in all cases, and the other predominant symptoms were abdominal pain (38.1%), diarrhea (35.6%), and headache (33.1%). Salmonella typhi, showed high resistance to ciprofloxacin (n = 163; 46.0%), and low resistance to ceftriaxone (n = 2; 0.6%). Four patients developed intestinal perforation, which was surgically repaired in two cases. Two patients (0.6%) died.

Conclusions

Typhoid fever was frequent among immigrants to endemic areas. Travelers returning from endemic areas with suspected typhoid fever should be treated empirically with third-generation cephalosporin after obtaining appropriate cultures. Moreover, preventive measurements such as education on food and water hygiene, and effective vaccination of travelers should be practiced widely among travelers to endemic areas to reduce morbidity and mortality.

Microbiological features of indigenous typhoid cases in Taiwan and relatedness to imported cases, 2001-2014: A cross-sectional analysis

BACKGROUND

Typhoid fever was rare in Taiwan but approximately two-thirds of the cases were indigenous. The transmission source of the indigenous cases and the relatedness to the imported cases remained unknown.

METHODS

Patients with any site culture positive for Salmonella enterica serovar Typhi were identified in a teaching hospital during 2001-2014. The isolates were determined for antibiotic susceptibilities, pulsed-field gel electrophoresis (PFGE) types and single nucleotide polymorphisms (SNP) types.

RESULTS

A total of 64 typhoid episodes were identified in 63 patients. Seventeen episodes (26.6%) were imported and a majority (10, 58.8%) of them were from Indonesia. The clinical manifestations, outcomes of patients and antibiograms of isolates were similar between indigenous and imported cases. 63.3% of the isolates were ciprofloxacin-resistant. The distributions of PFGE and SNP types did not differ significantly between indigenous and imported isolates, either (P = 0.191 and 0.124, respectively). Identical PFGE pattern could be identified in indigenous isolates appearing at certain time frames, indicating outbreaks due to local transmission of certain Typhi strains.

CONCLUSIONS

The imported cases of typhoid fever from Southeast Asia were the major sources of indigenous S. Typhi infections in Taiwan. Small-scale outbreaks occurred due to local transmission of the strains after their importation.

The Clean India Mission: Public and animal health benefits

The Clean India Mission is a national campaign that aims for complete elimination of open defecation from the country. In India, 564 million people do not have access to toilets and defecate in the open environment. The 'Millennium development goals' have given increased weightage to elimination of open defecation for improving health, nutrition and productivity of developing country populations. The Indian economy bears an estimated annual total loss (in terms of health, education, access time and tourism) of US$ 54 billion due to lack of toilets, poor hygiene and over US$ 38.5 billion in treatment costs for diseases occurring due to poor hygiene. Out of 1415 human pathogens, at least more than 10% of pathogens are transmitted through the faecal-oral route. The practice of open defecation helps pathogens persist in the environment and cause diseases. This review focuses on the current status and harms of open defecation, as well as the public and animal health benefits of implementing 'The Clean India Mission' in India.

Changing trends of culture-positive typhoid fever and antimicrobial susceptibility in a tertiary care North Indian Hospital over the last decade

Purpose

The present study was undertaken to analyse the trend in prevalence of culture-positive typhoid fever during the last decade and to determine antimicrobial susceptibility profile of Salmonella Typhi and Salmonella Paratyphi A isolated from patients of enteric fever presenting to our hospital.

Methods

All the culture-positive enteric fever cases during 2005-2016 presenting to our Hospital were included in the study. Antimicrobial susceptibility was done against chloramphenicol, amoxicillin, co-trimoxazole, ciprofloxacin, ofloxacin, levofloxacin, pefloxacin, ceftriaxone and azithromycin as per corresponding CLSI guidelines for each year. We also analysed the proportion of culture positivity during 1993-2016 in light of the antibiotic consumption data from published literature.

Results

A total of 1066 strains-S. Typhi (772) and S. Paratyphi A (294) were isolated from the blood cultures during the study. A maximum number of cases were found in July-September. Antimicrobial susceptibility for chloramphenicol, amoxicillin and co-trimoxazole was found to be 87.9%, 75.5%, 87.3% for S. Typhi and 94.2%, 90.1% and 94.2% for S. Paratyphi A, respectively. Ciprofloxacin, ofloxacin and levofloxacin susceptibility were 71.3%, 70.8% and 70.9% for S. Typhi and 58.1%, 57.4% and 57.1% for S. Paratyphi A, respectively. Azithromycin susceptibility was 98.9% in S. Typhi. Although susceptibility to ceftriaxone and cefixime was 100% in our isolates, there is a continuous increase in ceftriaxone minimum inhibitory concentration (MIC)₅₀and MIC₉₀values over the time. The proportion of blood culture-positive cases during 1993-2016 ranged from a minimum of 0.0006 in 2014 to a maximum of 0.0087 in 1999.

Conclusion

We found that the most common etiological agent of enteric fever is S. Typhi causing the majority of cases from July to October in our region. MIC to ceftriaxone in typhoidal salmonellae is creeping towards resistance and more data are needed to understand the azithromycin susceptibility.

Typhoid fever in Santiago, Chile: Insights from a mathematical model utilizing venerable archived data from a successful disease control program

Typhoid fever is endemic in many developing countries. In the early 20^th century, newly industrializing countries including the United States successfully controlled typhoid as water treatment (chlorination/sand filtration) and improved sanitation became widespread. Enigmatically, typhoid remained endemic through the 1980s in Santiago, Chile, despite potable municipal water and widespread household sanitation. Data were collected across multiple stages of endemicity and control in Santiago, offering a unique resource for gaining insight into drivers of transmission in modern settings. We developed an individual-based mathematical model of typhoid transmission, with model components including distinctions between long-cycle and short-cycle transmission routes. Data used to fit the model included the prevalence of chronic carriers, seasonality, longitudinal incidence, and age-specific distributions of typhoid infection and disease. Our model captured the dynamics seen in Santiago across endemicity, vaccination, and environmental control. Both vaccination and diminished exposure to seasonal amplified long-cycle transmission contributed to the observed declines in typhoid incidence, with the vaccine estimated to elicit herd effects. Vaccines are important tools for controlling endemic typhoid, with even limited coverage eliciting herd effects in this setting. Removing the vehicles responsible for amplified long-cycle transmission and assessing the role of chronic carriers in endemic settings are additional key elements in designing programs to achieve accelerated control of endemic typhoid.

Typhoid fever was successfully controlled in Santiago, Chile, after a series of interventions including vaccination with a live oral vaccine (Ty21a), and an environmental sanitation improvement, when a ban was put on the irrigation of salad vegetable crops with untreated sewage. Data collected during this period inform seasonality, age distribution and longitudinal trends of disease. We developed an individual-based, mathematical model to both simulate the dynamics of typhoid seen in Santiago, as well as to investigate relative impacts of the vaccine and sanitation interventions. We found that herd immunity resulted from field trials of the Ty21a vaccine and that chronic carriers were a likely driver of sustained transmission at low incidence levels. Modeling typhoid fever in areas that have demonstrated successful control provides insight for control strategies in modern settings.

Typhoid conjugate vaccines: a new tool in the fight against antimicrobial resistance

Typhoid fever is an acute systemic infectious disease responsible for an estimated 12-20 million illnesses and over 150 000 deaths annually. In March, 2018, a new recommendation was issued by WHO for the programmatic use of typhoid conjugate vaccines in endemic countries. Health economic analyses of typhoid vaccines have informed funding decisions and national policies regarding vaccine rollout. However, by focusing only on averted typhoid cases and their associated costs, traditional cost-effectiveness analyses might underestimate crucial benefits of typhoid vaccination programmes, because the potential effect of typhoid vaccines on the treatment of patients with non-specific acute febrile illnesses is not considered. For every true case of typhoid fever, three to 25 patients without typhoid disease are treated with antimicrobials unnecessarily, conservatively amounting to more than 50 million prescriptions per year. Antimicrobials for suspected typhoid might therefore be an important selective pressure for the emergence and spread of antimicrobial resistance globally. We propose that large-scale, more aggressive typhoid vaccination programmes-including catch-up campaigns in children up to 15 years of age, and vaccination in lower incidence settings-have the potential to reduce the overuse of antimicrobials and thereby reduce antimicrobial resistance in many bacterial pathogens. Funding bodies and national governments must therefore consider the potential for broad reductions in antimicrobial use and resistance in decisions related to the rollout of typhoid conjugate vaccines.

Why Is Eradicating Typhoid Fever So Challenging: Implications for Vaccine and Therapeutic Design

Salmonella enterica serovar Typhi (S. Typhi) and S. Paratyphi, namely typhoidal Salmonellae, are the cause of (para) typhoid fever, which is a devastating systemic infectious disease in humans. In addition, the spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) S. Typhi in many low and middle-income countries poses a significant risk to human health. While currently available typhoid vaccines and therapeutics are efficacious, they have some limitations. One important limitation is the lack of controlling individuals who chronically carry S. Typhi. However, due to the strict host specificity of S. Typhi to humans, S. Typhi research is hampered. As a result, our understanding of S. Typhi pathogenesis is incomplete, thereby delaying the development and improvement of prevention and treatment strategies. Nonetheless, to better combat and contain S. Typhi, it is vital to develop a vaccine and therapy for controlling both acutely and chronically infected individuals. This review discusses how scientists are trying to combat typhoid fever, why it is so challenging to do so, which approaches show promise, and what we know about the pathogenesis of S. Typhi chronic infection.

Introductory Article on Global Burden and Epidemiology of Typhoid Fever

This article is the introduction to a 12-paper supplement on global trends in typhoid fever. The Tackling Typhoid (T2) project was initiated in 2015 to synthesize the existing body of literature on typhoidal salmonellae and study national and regional typhoid fever trends. In addition to a global systematic review, eight case studies were undertaken to examine typhoid and paratyphoid fever trends in endemic countries alongside changes in relevant contextual factors. Incidence variations exist both within and between regions with large subnational differences as well, suggesting that public health changes impacting typhoid and paratyphoid fevers in one setting may not have similar impacts in another. This supplement also brings to light the lack of national typhoid fever surveillance systems, inconsistencies in diagnostics, and the lack of typhoid fever associated morbidity and mortality data in many countries, making it difficult to accurately quantify and track burden of disease. To better understand typhoid fever there is a need for more high-quality data from resource-poor settings. The implementation of typhoid surveillance systems alongside the transition to blood-culture confirmation of cases, where possible, would aid in the improvement of data quality in low-income settings. The following supplement includes the results of our global systematic review, eight-country case study articles, a qualitative article informed by semistructured interviews, and a conclusion article on potential ways forward for typhoid control.

Longitudinal Typhoid Fever Trends in India from 2000 to 2015

A very high incidence of typhoid was described in studies conducted in urban locations on the Indian subcontinent at the end of the twentieth century. Despite their availability, licensed immunogenic conjugate typhoid vaccines have not been introduced in the national immunization program, in part, because of a lack of understanding of where and for whom prevention is most necessary. Uncertainty regarding the burden of disease is based on the lack of reliable, recent estimates of culture-confirmed typhoid and an observed trend of low isolations of Salmonella Typhi and fewer complications at large referral hospitals in India. In this article, we examine the trends of S. Typhi isolation at three large tertiary care centers across India over 15 years and describe trends of recognized risk factors for typhoid from published literature. There appears to be a decline in the isolation of S. Typhi in blood cultures, which is more apparent in the past 5 years. These trends are temporally related to economic improvement, female literacy, and the use of antibiotics such as cephalosporins and azithromycin. The analysis of trends of culture-confirmed typhoid may not accurately capture the typhoid incidence trends if antibiotic use confounds the burden of disease presenting to larger facilities. Emerging antimicrobial resistance may result in a resurgence of disease if the underlying incidence and transmission of typhoid are not adequately addressed through public health approaches.

The Control of Typhoid Fever in Vietnam

Typhoid fever, caused by Salmonella enterica serovar Typhi (S. Typhi), is a diminishing public health problem in Vietnam, and this process may represent a prototype for typhoid elimination in Asia. Here, we review typhoid epidemiology in Vietnam over 20 years and assess the potential drivers associated with typhoid reduction. In the 1990s, multidrug resistant S. Typhi were highly prevalent in a sentinel hospital in southern Vietnam. A national typhoid incidence rate of 14.7/100,000 population per year was estimated around the new millennium. The Vietnamese government recognized the public health issue of typhoid in the 1990s and initiated vaccine campaigns to protect the most vulnerable members of the population. At their peak, these campaigns immunized approximately 1,200,000 children in 35 provinces. Concurrently, Vietnam experienced unprecedented economic development from 1998 to 2014, with the gross national income per capita increasing from $360 to $1,890 over this period. More recent typhoid incidence data are not available, but surveillance suggests that the current disease burden is negligible. This trajectory can be considered a major public health success. However, a paucity of systematic data makes it difficult to disaggregate the roles of immunization and water, sanitation, and hygiene (WASH) interventions in typhoid reduction in Vietnam. Given the limitations of typhoid vaccines, we surmise the practical elimination of typhoid was largely driven by economic development and improvement in general population living standards. Better designed WASH intervention studies with clinical endpoints and systematic incidence data are essential to glean a greater understanding of contextual factors that impact typhoid incidence reduction.

Trends, Associations, and Antimicrobial Resistance of Salmonella Typhi and Paratyphi in Pakistan

Typhoid remains a major cause of morbidity and mortality in endemic countries. This review analyzed typhoid burden changes in Pakistan and its association with contextual factors. A retrospective cohort study on blood culture–positive typhoid and antibiotic resistance was conducted from three tertiary hospitals and contextual factor data obtained from primary household surveys. Salmonella Typhi/Paratyphi positivity rates were estimated and trend analysis was carried out using positive cases out of total number of blood cultures performed. Contextual factors’ associations were determined through bivariate correlation analysis, using STATA (SataCorp, College Station, TX). We report a total of 17,387 S. Typhi–positive and 8,286 S. Paratyphi A and B–positive specimens from 798,137 blood cultures performed. The results suggest an overall decline in typhoid incidence as S. Typhi positivity rates declined from 6.42% in 1992 to 1.32% in 2015 and S. Paratyphi (A and B) from 1.29% to 0.39%. Subgroup analysis suggests higher S. Typhi prevalence in adults older than 18 years, whereas S. Paratyphi is greater in children aged 5–18 years. The relative contribution of S. Paratyphi to overall confirmed cases increased from 16.8% in 1992 to 23% in 2015. The analysis suggests high burden of fluoroquinolone resistance and multidrug-resistant S. Typhi strains. Statistically significant associations of water, sanitation indicators, and literacy rates were observed with typhoid positivity. Despite some progress, typhoid remains endemic and a strong political will is required for targeted typhoid control strategies. A multipronged approach of improving water, sanitation and hygiene in combination with large-scale immunization in endemic settings of Pakistan could help reduce burden and prevent epidemics.

Evaluation of alum-based adjuvant on the immunogenicity of salmonella enterica serovar typhi conjugates vaccines

The function of adjuvant in maintaining the long-term immune response to Typhoid conjugate vaccine (TCV) was evaluated in. Two TCV products, Vi-DT and Vi-TT, were formulated in either aluminum phosphate (AlPO₄) or aluminum hydroxide (AlOH) as adjuvants and TCV formulated in phosphate buffer saline were used as controls. In each case, a group of Balb/c mice was injected intramuscularly with two doses of the formulated vaccine at two-week intervals. The anti-Vi IgG responses were monitored by Enzyme-Linked Immunosorbent Assay and the levels of CD4⁺ T-cells expressing cytokine were characterized using intracellular cytokine staining. All mice immunized by TCV formulated in adjuvant elicited anti-Vi response to a higher level than the group receiving TCV formulated in PBS. The extent of adsorption of TCV in AlOH was greater than that in AlPO₄, and this finding correlated well with the observation that the mice immunized with two doses of Vi-DT(AlOH) elicited anti-Vi IgG to a level higher than that seen with Vi-DT(AlPO₄). The mice primed with Vi-TT(AlOH) produced lower anti-Vi IgG (25.901 GM) compared to those receiving Vi-TT(AlPO₄) (49.219 GM). However, after the second injection, the former raised the antibody level significantly to 137.008 GM while the latter provided a value of only 104.966 GM. The groups of mice vaccinated by TCV formulated in AlOH expressed IL4 at higher levels than the other groups, which correlated positively with the high Anti-Vi IgG in these animals. In conclusion, AlOH could be recommended as an effective adjuvant for TCV to provide a long-term immune response.

Vaccines for preventing typhoid fever

BACKGROUND

Typhoid fever and paratyphoid fever continue to be important causes of illness and death, particularly among children and adolescents in south-central and southeast Asia. Two typhoid vaccines are widely available, Ty21a (oral) and Vi polysaccharide (parenteral). Newer typhoid conjugate vaccines are at varying stages of development and use. The World Health Organization has recently recommended a Vi tetanus toxoid (Vi-TT) conjugate vaccine, Typbar-TCV, as the preferred vaccine for all ages.

OBJECTIVES

To assess the effects of vaccines for preventing typhoid fever.

SEARCH METHODS

In February 2018, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, Embase, LILACS, and mRCT. We also searched the reference lists of all included trials.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials (RCTs) comparing typhoid fever vaccines with other typhoid fever vaccines or with an inactive agent (placebo or vaccine for a different disease) in adults and children. Human challenge studies were not eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied inclusion criteria and extracted data, and assessed the certainty of the evidence using the GRADE approach. We computed vaccine efficacy per year of follow-up and cumulative three-year efficacy, stratifying for vaccine type and dose. The outcome addressed was typhoid fever, defined as isolation of Salmonella enterica serovar Typhi in blood. We calculated risk ratios (RRs) and efficacy (1 - RR as a percentage) with 95% confidence intervals (CIs).

MAIN RESULTS

In total, 18 RCTs contributed to the quantitative analysis in this review: 13 evaluated efficacy (Ty21a: 5 trials; Vi polysaccharide: 6 trials; Vi-rEPA: 1 trial; Vi-TT: 1 trial), and 9 reported on adverse events. All trials but one took place in typhoid-endemic countries. There was no information on vaccination in adults aged over 55 years of age, pregnant women, or travellers. Only one trial included data on children under two years of age.Ty21a vaccine (oral vaccine, three doses)A three-dose schedule of Ty21a vaccine probably prevents around half of typhoid cases during the first three years after vaccination (cumulative efficacy 2.5 to 3 years: 50%, 95% CI 35% to 61%, 4 trials, 235,239 participants, moderate-certainty evidence). These data include patients aged 3 to 44 years.Compared with placebo, this vaccine probably does not cause more vomiting, diarrhoea, nausea or abdominal pain (2 trials, 2066 participants; moderate-certainty evidence), headache, or rash (1 trial, 1190 participants; moderate-certainty evidence); however, fever (2 trials, 2066 participants; moderate-certainty evidence) is probably more common following vaccination.Vi polysaccharide vaccine (injection, one dose)A single dose of Vi polysaccharide vaccine prevents around two-thirds of typhoid cases in the first year after vaccination (year 1: 69%, 95% CI 63% to 74%; 3 trials, 99,979 participants; high-certainty evidence). In year 2, trial results were more variable, with the vaccine probably preventing between 45% and 69% of typhoid cases (year 2: 59%, 95% CI 45% to 69%; 4 trials, 194,969 participants; moderate-certainty evidence). These data included participants aged 2 to 55 years of age.The three-year cumulative efficacy of the vaccine may be around 55% (95% CI 30% to 70%; 11,384 participants, 1 trial; low-certainty evidence). These data came from a single trial conducted in South Africa in the 1980s in participants aged 5 to 15 years.Compared with placebo, this vaccine probably did not increase the incidence of fever (3 trials, 132,261 participants; moderate-certainty evidence) or erythema (3 trials, 132,261 participants; low-certainty evidence); however, swelling (3 trials, 1767 participants; moderate-certainty evidence) and pain at the injection site (1 trial, 667 participants; moderate-certainty evidence) were more common in the vaccine group.Vi-rEPA vaccine (two doses)Administration of two doses of the Vi-rEPA vaccine probably prevents between 50% and 96% of typhoid cases during the first two years after vaccination (year 1: 94%, 95% CI 75% to 99%; year 2: 87%, 95% CI 56% to 96%, 1 trial, 12,008 participants; moderate-certainty evidence). These data came from a single trial with children two to five years of age conducted in Vietnam.Compared with placebo, both the first and the second dose of this vaccine increased the risk of fever (1 trial, 12,008 and 11,091 participants, low-certainty evidence) and the second dose increase the incidence of swelling at the injection site (one trial, 11,091 participants, moderate-certainty evidence).Vi-TT vaccine (two doses)We are uncertain of the efficacy of administration of two doses of Vi-TT (PedaTyph) in typhoid cases in children during the first year after vaccination (year 1: 94%, 95% CI -1% to 100%, 1 trial, 1625 participants; very low-certainty evidence). These data come from a single cluster-randomized trial in children aged six months to 12 years and conducted in India. For single dose Vi-TT (Typbar-TCV), we found no efficacy trials evaluating the vaccine with natural exposure.There were no reported serious adverse effects in RCTs of any of the vaccines studied.

AUTHORS' CONCLUSIONS

The licensed Ty21a and Vi polysaccharide vaccines are efficacious in adults and children older than two years in endemic countries. The Vi-rEPA vaccine is just as efficacious, although data is only available for children. The new Vi-TT vaccine (PedaTyph) requires further evaluation to determine if it provides protection against typhoid fever. At the time of writing, there were only efficacy data from a human challenge setting in adults on the Vi-TT vaccine (Tybar), which clearly justify the ongoing field trials to evaluate vaccine efficacy.

Diagnosis and Treatment of Human Salmonellosis in Addis Ababa City, Ethiopia

BACKGROUND

Diagnosis using reliable tools and treatment following in vitro antimicrobial susceptibility tests are critical to proper addressing of antibiotic-resistant Salmonella infection.

METHODOLOGY

A cross-sectional study was conducted to assess the practice of diagnosis and treatment of salmonellosis in Addis Ababa. Tube Widal test (for blood samples only), culture, biochemical and carbohydrate fermentation, serotyping, and antimicrobial susceptibility tests were employed for both blood and stool samples.

RESULTS

Of all the diseases listed in the diagnosis, nontyphoidal (n = 72, 13.71%) and typhoidal (n = 47, 8.95%) salmonellosis were the second and third common diseases. Among the 288 blood samples, almost half were positive for O, H, or both antigens. However, only 1 (0.68%) of the positive blood samples yielded Salmonella isolate during culture. The study demonstrated low specificity (0.68%) and positive predictive value (48.78%) of Widal test. Conversely, the test showed 100% sensitivity and negative predictive values. Salmonella isolates were identified from 7 (7.07%) of 99 stool samples. Two-thirds of salmonellosis suspected patients received antibiotic treatment. However, only half of the confirmed salmonellosis patients were treated with appropriate antibiotics. All of the isolates were susceptible to ciprofloxacin and ceftriaxone but resistant to ampicillin.

CONCLUSIONS

Majority of the patients who participated in this study were wrongly diagnosed using symptoms, clinical signs, and tube Widal test. Consequently, most of the patients received inappropriate treatment.

Review of current typhoid fever vaccines, cross-protection against paratyphoid fever, and the European guidelines

INTRODUCTION

Typhoid and paratyphoid fever remain a global health problem, which - in non-endemic countries - are mainly seen in travelers, particularly in VFRs (visiting friends and relatives), with occasional local outbreaks occurring. A rise in anti-microbial resistance emphasizes the role of preventive measures, especially vaccinations against typhoid and paratyphoid fever for travelers visiting endemic countries. Areas covered: This state-of-the-art review recapitulates the epidemiology and mechanisms of disease of typhoid and paratyphoid fever, depicts the perspective of non-endemic countries and travelers (VFRs), and collectively presents current European recommendations for typhoid fever vaccination. We provide a brief overview of available (and developmental) vaccines in Europe, present current data on cross-protection to S. Paratyphi, and aim to provide a background for typhoid vaccine decision-making in travelers. Expert commentary: European recommendations are not harmonized. Experts must assess vaccination of travelers based on current country-specific recommendations. Travel health practitioners should be aware of the issues surrounding vaccination of travelers and be motivated to increase awareness of typhoid and paratyphoid fever risks.

Estimating the incidence of enteric fever in children in India: a multi-site, active fever surveillance of pediatric cohorts

Background

Salmonella Typhi is responsible for about 20 million episodes of illness and over 140,000 deaths annually globally. South Asia has the highest documented burden of typhoid and is home to the multi-drug resistant H58 strain that makes treatment more challenging. The WHO recommends the use of Typhoid Conjugate Vaccines in typhoid endemic countries. Decisions on the preferred immunization strategy should be based on an analysis of disease burden, availability, affordability, and operational feasibility. Typhoid vaccines have so far remained unimplemented as public health measures because of a perceived decline in typhoid burden in recent years. The apparent decline, based on hospital reports, may be a result of rampant antimicrobial use in the community and therefore estimation of disease incidence at the community is necessary to better measure disease incidence and transmission.

Methods

Age-specific incidence of typhoid fever in children between 6 months and 15 years will be estimated in four community based cohorts in varied settings across India using standardized protocols for active fever surveillance in the community. Data will be collected on secured cloud infrastructure using a combination of android and web-based real-time data collection tools. Blood cultures will be done for children with fever lasting 3 or more consecutive days using automated blood culture systems. Those with blood-culture confirmed typhoid fever will be followed up till 90 days to estimate costs and clinical outcomes of the illness episodes. Environmental factors, access to safe water, sanitation, hygiene, food hygiene, demography, population density and socioeconomic status will be assessed periodically to characterise risk factors and permit extrapolation of burden to similar risk settings.

Discussion

With the availability of licensed typhoid conjugated vaccines in India, it is important to consider whether the burden of disease is present and sufficient to require the use of vaccine in addition to other interventions. Active case finding in the community permits the detection of cases that would be missed in facility-based surveillance systems. Understanding the age distribution, burden, cost-of-illness and transmission of disease is essential to plan interventions and predict their potential impact.

Trial registration

The surveillance has been prospectively registered in the Clinical Trial Registry of India (CTRI/2017/09/009719) on 12 September 2017.

Typhoid Vaccination among Japanese Travelers to South Asia and the Factors Associated with Compliance

Objective In 2010, candid advice concerning the low rate of typhoid vaccination among Japanese travelers was received from Nepal. Recently, progressive Japanese travel clinics have encouraged Japanese travelers to be vaccinated against typhoid fever in conjunction with officially approved vaccines, such as hepatitis A vaccine. We herein report the status of typhoid vaccinations for Japanese travelers to the most endemic area (South Asia) and describe the factors associated with compliance. Methods In the travel clinic at Kurume University Hospital, we used the following criteria to retrospectively extract the records of new pre-travel Japanese clients between January 2011 and March 2015: hepatitis A vaccine administered, traveling to South Asian countries, and ≥2 years of age. We first summarized the participants and then divided them into typhoid-vaccinated and typhoid non-vaccinated groups for a comparative analysis. Results This study included 160 clients. A majority (70.0%) of these clients traveled for business. The duration of trips was long (≥1 month) (75.0%), and India was a popular destination (90.6%). A comparative study between the vaccinated group (n=122) and the non-vaccinated group (n=38) revealed that the two factors most positively associated with typhoid vaccination were business trips [adjusted odds ratio (aOR) 3.59, 95% confidence interval (CI) 1.42-9.06] and coverage by a company/organization payment plan (aOR 7.14, 95% CI 2.67-20.3). Conclusion The trend toward typhoid vaccination among Japanese travelers to South Asia with pre-travel consultation is correlated with business trips and coverage by a company/organization payment plan. If problems concerning the cost of vaccines were resolved, more travelers would request typhoid vaccination.

Infection-associated Hemophagocytic Lymphohistiocytosis: An Unusual Clinical Masquerader

Hemophagocytic lymphohistiocytosis (HLH) secondary to an infection is a great impersonator. It is caused by hyperimmune activation, which leads to a wide array of hematological abnormalities. If the disease is untreated, it is usually fatal. We report the case of a four-year-old girl who presented to our tertiary care hospital with high-grade fever, frequent loose stools, and bleeding from the lips and gums. Investigations showed pancytopenia, hyperferritinemia, hypofibrinogenemia, and hypertriglyceridemia whereas the bone marrow biopsy revealed hemophagocytosis with trilineage suppression. Blood cultures grew Salmonella typhi. After ruling out other possibilities, the diagnosis of HLH was made as per the HLH-2004 diagnostic criteria. The patient responded well to culture-sensitive antibiotics and supportive treatment. We discuss the diagnosis and clinical course of this unique case and strive to create awareness about secondary HLH induced by common diseases, such as typhoid fever.

Clinical profile, antibiotic susceptibility pattern of bacterial isolates and factors associated with complications in culture-proven typhoid patients admitted to an urban hospital in Bangladesh

OBJECTIVES

Typhoid fever is one of the major causes of morbidity and mortality in typhoid endemic countries like Bangladesh. However, data on the clinical and microbiological profile as well as factors associated with complications of typhoid in Bangladesh are scarce. We intended to characterise the clinical and microbiological profile of culture-proven typhoid fever and to identify factors associated with complications.

METHODOLOGY

Retrospective analysis of clinical data from 431 patients with culture-confirmed typhoid fever admitted to Dhaka hospital of International Centre for Diarrhoeal Disease Research, Bangladesh, between January 2010 and December 2014. Clinical and microbiological profiles of the patients including age, sex, and duration of illness prior to hospital admission, haematological parameters and the antimicrobial resistance profile of the infecting isolate, duration of hospital stay and defervescence time were examined by logistic regression to identify the factors associated with complications.

RESULT

About one of three patients were children under 5 years, and 21.5% of them were severely malnourished. During hospitalisation, 17.4% patients developed complications; mainly encephalopathy (6.7%), ileus (6.5%) and pneumonia (3.5%). Among culture-positive cases, 28.3% isolates showed multidrug resistant (MDR) and more than 90% of isolates were resistant to nalidixic acid and had intermediate sensitivity to ciprofloxacin. Five isolates were resistant to azithromycin; all isolates were sensitive to cefixime and ceftriaxone. Complication was independently associated with duration of fever before admission (adjusted odds ratio: 0.85; 95% CI: 0.074-0.97; P < 0.05), thrombocytopenia on admission (AOR: 2.84; 95% CI: 01.06-7.57; P < 0.05), duration of hospital stay (AOR: 1.34; 95% CI: 1.15-1.57; P < 0.01) and defervescence time (AOR: 0.83; 95% CI: 0.70-0.99; P < 0.05).

CONCLUSION

The high prevalence of typhoid fever among under-five children and complications among hospitalised patients are matters of concern. Sensitivity of Salmonella Typhi to ceftriaxone and cefixime was better than to other conventional antibiotics. Shorter duration of fever and thrombocytopenia on admission can be considered as early signs of complications.

Typhoid Fever due to Extended Spectrum β-Lactamase-Producing Salmonella enterica Serovar Typhi: A Case Report and Literature Review

Emergence of cephalosporin-resistant strains of Salmonella enterica serovar Typhi is a cause of concern in the management of enteric fever. Cephalosporin resistance in Salmonella species is mainly due to the production of extended-spectrum β-lactamases (ESBLs). The majority of ESBLs in Salmonella enterica serovar Typhi are derivatives of the TEM, SHV, and CTX-M β-lactamase families. Of these, CTX-M appears to be predominant. This paper discusses the detection and molecular characterization of an ESBL-producing Salmonella enterica serovar Typhi strain isolated from a patient who was admitted to a private hospital in Sri Lanka. The three main types of β-lactamases such as TEM, SHV, and CTX-M were identified in this isolate. This case report from Sri Lanka contributes to the knowledge of the increasingly reported cases of typhoid fever due to Salmonella enterica serovar Typhi resistant to β-lactamase by ESBL production.