The Identification of Enteric Fever-Specific Antigens for Population-Based Serosurveillance.

Background: Enteric fever, caused by Salmonella enterica serovars Typhi and Paratyphi A, is a major public health problem in low- and middle-income countries. Moderate sensitivity and scalability of current methods likely underestimate enteric fever burden. Determining the serological responses to organism-specific antigens may improve incidence measures.

An age-stratified serosurvey against purified Salmonella enterica serovar Typhi antigens in the Lao People´s Democratic Republic.

The epidemiology of typhoid fever in Lao People`s Democratic Republic is poorly defined. Estimating the burden of typhoid fever in endemic countries is complex due to the cost and limitations of population-based surveillance; serological approaches may be a more cost-effective alternative. ELISAs were performed on 937 serum samples (317 children and 620 adults) from across Lao PDR to measure IgG antibody titers against Vi polysaccharide and the experimental protein antigens, CdtB and HlyE.

The Role of Maternally Acquired Antibody in Providing Protective Immunity Against Nontyphoidal Salmonella in Urban Vietnamese Infants: A Birth Cohort Study.

Background: Nontyphoidal Salmonella (NTS) organisms are a major cause of gastroenteritis and bacteremia, but little is known about maternally acquired immunity and natural exposure in infant populations residing in areas where NTS disease is highly endemic.

Methods: We recruited 503 pregnant mothers and their infants (following delivery) from urban areas in Vietnam and followed infants until they were 1 year old. Exposure to the dominant NTS serovars, Salmonella enterica serovars Typhimurium and Enteritidis, were assessed using lipopolysaccharide (LPS) O antigen-specific antibodies.

The Control of Typhoid Fever in Vietnam.

Typhoid fever, caused by serovar Typhi (. 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.

Diagnostic metabolite biomarkers of chronic typhoid carriage.

Background: Salmonella Typhi and Salmonella Paratyphi A are the agents of enteric (typhoid) fever; both can establish chronic carriage in the gallbladder. Chronic Salmonella carriers are typically asymptomatic, intermittently shedding bacteria in the feces, and contributing to disease transmission. Detecting chronic carriers is of public health relevance in areas where enteric fever is endemic, but there are no routinely used methods for prospectively identifying those carrying Salmonella in their gallbladder.

An evaluation of purified Salmonella Typhi protein antigens for the serological diagnosis of acute typhoid fever.

Objectives: The diagnosis of typhoid fever is a challenge. Aiming to develop a typhoid diagnostic we measured antibody responses against Salmonella Typhi (S. Typhi) protein antigens and the Vi polysaccharide in a cohort of Bangladeshi febrile patients.

Molecular epidemiology and antimicrobial resistance phenotypes of Acinetobacter baumannii isolated from patients in three hospitals in southern Vietnam.

Multidrug resistance in the nosocomial pathogen Acinetobacter baumannii limits therapeutic options and impacts on clinical care. Resistance against carbapenems, a group of last-resort antimicrobials for treating multidrug-resistant (MDR) A. baumannii infections, is associated with the expression (and over-expression) of carbapenemases encoded by the blaOXA genes.

The Molecular and Spatial Epidemiology of Typhoid Fever in Rural Cambodia.

Typhoid fever, caused by the bacterium Salmonella Typhi, is an endemic cause of febrile disease in Cambodia. The aim of this study was to better understand the epidemiology of pediatric typhoid fever in Cambodia. We accessed routine blood culture data from Angkor Hospital for Children (AHC) in Siem Reap province between 2007 and 2014, and performed whole genome sequencing (WGS) on the isolated bacteria to characterize the S.

A novel ciprofloxacin-resistant subclade of H58 Salmonella Typhi is associated with fluoroquinolone treatment failure.

The interplay between bacterial antimicrobial susceptibility, phylogenetics and patient outcome is poorly understood. During a typhoid clinical treatment trial in Nepal, we observed several treatment failures and isolated highly fluoroquinolone-resistant Salmonella Typhi (S. Typhi).

The transfer and decay of maternal antibody against Shigella sonnei in a longitudinal cohort of Vietnamese infants.

Background: Shigella sonnei is an emergent and major diarrheal pathogen for which there is currently no vaccine. We aimed to quantify duration of maternal antibody against S. sonnei and investigate transplacental IgG transfer in a birth cohort in southern Vietnam.

The Ecological Dynamics of Fecal Contamination and Salmonella Typhi and Salmonella Paratyphi A in Municipal Kathmandu Drinking Water.

One of the UN sustainable development goals is to achieve universal access to safe and affordable drinking water by 2030. It is locations like Kathmandu, Nepal, a densely populated city in South Asia with endemic typhoid fever, where this goal is most pertinent. Aiming to understand the public health implications of water quality in Kathmandu we subjected weekly water samples from 10 sources for one year to a range of chemical and bacteriological analyses.

In vitro activity of colistin in antimicrobial combination against carbapenem-resistant Acinetobacter baumannii isolated from patients with ventilator-associated pneumonia in Vietnam.

Acinetobacter baumannii has become one of the major infection threats in intensive care units (ICUs) globally. Since 2008, A. baumannii has been the leading cause of ventilator-associated pneumonia (VAP) in our ICU at an infectious disease hospital in southern Vietnam.

A prospective multi-center observational study of children hospitalized with diarrhea in Ho Chi Minh City, Vietnam.

We performed a prospective multicenter study to address the lack of data on the etiology, clinical and demographic features of hospitalized pediatric diarrhea in Ho Chi Minh City (HCMC), Vietnam. Over 2,000 (1,419 symptomatic and 609 non-diarrheal control) children were enrolled in three hospitals over a 1-year period in 2009-2010. Aiming to detect a panel of pathogens, we identified a known diarrheal pathogen in stool samples from 1,067/1,419 (75.

Two cases of bacteriemia caused by nontoxigenic, non-O1, non-O139 Vibrio cholerae isolates in Ho Chi Minh City, Vietnam.

The toxigenic bacterium Vibrio cholerae belonging to the O1 and O139 serogroups is commonly associated with epidemic diarrhea in tropical settings; other diseases caused by this environmental pathogen are seldom identified. Here we report two unassociated cases of nonfatal, nontoxigenic V. cholerae non-O1, non-O139 bacteremia in patients with comorbidities in Ho Chi Minh City, Vietnam, that occurred within a 4-week period.

The characterization of ESBL genes in Escherichia coli and Klebsiella pneumoniae causing nosocomial infections in Vietnam.

Background: Extended-spectrum β-lactamases (ESBLs) are enzymes capable of hydrolyzing oxyimino-β-lactams and inducing resistance to third generation cephalosporins. The genes encoding ESBLs are widespread and generally located on highly transmissible resistance plasmids. We aimed to investigate the complement of ESBL genes in E.

Fitness benefits in fluoroquinolone-resistant Salmonella Typhi in the absence of antimicrobial pressure.

Fluoroquinolones (FQ) are the recommended antimicrobial treatment for typhoid, a severe systemic infection caused by the bacterium Salmonella enterica serovar Typhi. FQ-resistance mutations in S. Typhi have become common, hindering treatment and control efforts.

Evaluation of the diagnostic accuracy of a typhoid IgM flow assay for the diagnosis of typhoid fever in Cambodian children using a Bayesian latent class model assuming an imperfect gold standard.

Rapid diagnostic tests are needed for typhoid fever (TF) diagnosis in febrile children in endemic areas. Five hundred children admitted to the hospital in Cambodia between 2009 and 2010 with documented fever (≥ 38°C) were investigated using blood cultures (BCs), Salmonella Typhi/Paratyphi A real-time polymerase chain reactions (PCRs), and a Typhoid immunoglobulin M flow assay (IgMFA). Test performance was determined by conventional methods and Bayesian latent class modeling.

Tracking the establishment of local endemic populations of an emergent enteric pathogen.

Shigella sonnei is a human-adapted pathogen that is emerging globally as the dominant agent of bacterial dysentery. To investigate local establishment, we sequenced the genomes of 263 Vietnamese S. sonnei isolated over 15 y.

Differential epidemiology of Salmonella Typhi and Paratyphi A in Kathmandu, Nepal: a matched case control investigation in a highly endemic enteric fever setting.

Background: Enteric fever, a systemic infection caused by the bacteria Salmonella Typhi and Salmonella Paratyphi A, is endemic in Kathmandu, Nepal. Previous work identified proximity to poor quality water sources as a community-level risk for infection. Here, we sought to examine individual-level risk factors related to hygiene and sanitation to improve our understanding of the epidemiology of enteric fever in this setting.

Identification of immunogenic Salmonella enterica serotype Typhi antigens expressed in chronic biliary carriers of S. Typhi in Kathmandu, Nepal.

Background: Salmonella enterica serotype Typhi can colonize and persist in the biliary tract of infected individuals, resulting in a state of asymptomatic chronic carriage. Chronic carriers may act as persistent reservoirs of infection within a community and may introduce infection to susceptible individuals and new communities. Little is known about the interaction between the host and pathogen in the biliary tract of chronic carriers, and there is currently no reliable diagnostic assay to identify asymptomatic S.

Identification of Salmonella enterica serovar Typhi genotypes by use of rapid multiplex ligation-dependent probe amplification.

Salmonella enterica serovar Typhi, the causative agent of typhoid fever, is highly clonal and genetically conserved, making isolate subtyping difficult. We describe a standardized multiplex ligation-dependent probe amplification (MLPA) genotyping scheme targeting 11 key phylogenetic markers of the S. Typhi genome.