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1.
J Infect Dis ; 219(2): 295-304, 2019 01 07.
Article in English | MEDLINE | ID: mdl-30321351

ABSTRACT

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. Antibody dynamics, the role of maternally acquired antibodies, and NTS seroincidence rates were modeled using multivariate linear risk factor models and generalized additive mixed-effect models. Results: Transplacental transfer of NTS LPS-specific maternal antibodies to infants was highly efficient. Waning of transplacentally acquired NTS LPS-specific antibodies at 4 months of age left infants susceptible to Salmonella organisms, after which they began to seroconvert. High seroincidences of S. Typhimurium and S. Enteritidis LPS were observed, and infants born with higher anti-LPS titers had greater plasma bactericidal activity and longer protection from seroconversion. Conclusions: Although Vietnamese infants have extensive exposure to NTS, maternally acquired antibodies appear to play a protective role against NTS infections during early infancy. These findings suggest that prenatal immunization may be an appropriate strategy to protect vulnerable infants from NTS disease.


Subject(s)
Antibodies, Bacterial/immunology , Immunity, Maternally-Acquired/immunology , Immunity , Salmonella Infections/immunology , Adult , Antibodies, Bacterial/blood , Cohort Studies , Female , Humans , Infant , Infant, Newborn , Lipopolysaccharides/immunology , Male , Multivariate Analysis , O Antigens , Risk Factors , Salmonella enteritidis , Salmonella typhimurium , Seroepidemiologic Studies , Serogroup , Vietnam
2.
J Clin Microbiol ; 52(10): 3819-21, 2014 Oct.
Article in English | MEDLINE | ID: mdl-25122858

ABSTRACT

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.


Subject(s)
Bacteremia/diagnosis , Bacteremia/microbiology , Vibrio Infections/diagnosis , Vibrio Infections/microbiology , Vibrio cholerae non-O1/isolation & purification , Aged , Bacteremia/pathology , Female , Humans , Male , Middle Aged , Vibrio Infections/pathology , Vietnam
3.
J Trop Pediatr ; 58(1): 68-70, 2012 Feb.
Article in English | MEDLINE | ID: mdl-21508082

ABSTRACT

Typhoid fever was confirmed by positive blood culture in 5 (3.7%) of 134 febrile children hospitalized in Cambodia. Typhoid was suspected in an additional 25 (18.7 %) blood culture-negative children based on: a positive immunoglobulin M lateral flow assay (IgMFA) (16); a positive polymerase chain reaction (PCR) for Salmonella typhi (2); or clinical assessment (7). The specificity of the IgMFA and PCR assays requires further study.


Subject(s)
Child, Hospitalized , Typhoid Fever/blood , Typhoid Fever/epidemiology , Adolescent , Cambodia/epidemiology , Child , Child, Preschool , Female , Humans , Immunoglobulin M/blood , Infant , Male , Polymerase Chain Reaction , Sensitivity and Specificity
4.
BMC Infect Dis ; 10: 125, 2010 May 21.
Article in English | MEDLINE | ID: mdl-20492644

ABSTRACT

BACKGROUND: PCR amplification for the detection of pathogens in biological material is generally considered a rapid and informative diagnostic technique. Invasive Salmonella serovars, which cause enteric fever, can be commonly cultured from the blood of infected patients. Yet, the isolation of invasive Salmonella serovars from blood is protracted and potentially insensitive. METHODS: We developed and optimised a novel multiplex three colour real-time PCR assay to detect specific target sequences in the genomes of Salmonella serovars Typhi and Paratyphi A. We performed the assay on DNA extracted from blood and bone marrow samples from culture positive and negative enteric fever patients. RESULTS: The assay was validated and demonstrated a high level of specificity and reproducibility under experimental conditions. All bone marrow samples tested positive for Salmonella, however, the sensitivity on blood samples was limited. The assay demonstrated an overall specificity of 100% (75/75) and sensitivity of 53.9% (69/128) on all biological samples. We then tested the PCR detection limit by performing bacterial counts after inoculation into blood culture bottles. CONCLUSIONS: Our findings corroborate previous clinical findings, whereby the bacterial load of S. Typhi in peripheral blood is low, often below detection by culture and, consequently, below detection by PCR. Whilst the assay may be utilised for environmental sampling or on differing biological samples, our data suggest that PCR performed directly on blood samples may be an unsuitable methodology and a potentially unachievable target for the routine diagnosis of enteric fever.


Subject(s)
Bacteriological Techniques/methods , Paratyphoid Fever/diagnosis , Polymerase Chain Reaction/methods , Salmonella paratyphi A/isolation & purification , Salmonella typhi/isolation & purification , Typhoid Fever/diagnosis , Adolescent , Adult , Aged , Aged, 80 and over , Blood/microbiology , Bone Marrow/microbiology , Humans , Middle Aged , Reproducibility of Results , Salmonella paratyphi A/genetics , Salmonella typhi/genetics , Sensitivity and Specificity , Young Adult
5.
Clin Infect Dis ; 49(9): 1387-92, 2009 Nov 01.
Article in English | MEDLINE | ID: mdl-19814625

ABSTRACT

Adjunctive treatment to improve outcome from bacterial meningitis has centered on dexamethasone. Among Vietnamese patients with bacterial meningitis, cerebrospinal fluid (CSF) opening pressure and CSF:plasma glucose ratios were significantly improved and levels of CSF cytokines interleukin (IL)-6, IL-8, and IL-10 and were all statistically significantly lower after treatment in patients who were randomized to dexamethasone, compared with levels in patients who received placebo.


Subject(s)
Dexamethasone/therapeutic use , Meningitis, Bacterial/cerebrospinal fluid , Meningitis, Bacterial/drug therapy , Adolescent , Adult , Anti-Inflammatory Agents/therapeutic use , Asian People , Child , Female , Humans , Interleukin-10/cerebrospinal fluid , Interleukin-6/cerebrospinal fluid , Interleukin-8/cerebrospinal fluid , Male , Middle Aged , Vietnam , Young Adult
7.
BMC Infect Dis ; 9: 204, 2009 Dec 15.
Article in English | MEDLINE | ID: mdl-20003464

ABSTRACT

BACKGROUND: Shigellosis remains considerable public health problem in some developing countries. The nature of Shigellae suggests that they are highly adaptable when placed under selective pressure in a human population. This is demonstrated by variation and fluctuations in serotypes and antimicrobial resistance profile of organisms circulating in differing setting in endemic locations. Antimicrobial resistance in the genus Shigella is a constant threat, with reports of organisms in Asia being resistant to multiple antimicrobials and new generation therapies. METHODS: Here we compare microbiological, clinical and epidemiological data from patients with shigellosis over three different periods in southern Vietnam spanning 14 years. RESULTS: Our data demonstrates a shift in dominant infecting species (S. flexneri to S. sonnei) and resistance profile of the organisms circulating in southern Vietnam. We find that there was no significant variation in the syndromes associated with either S. sonnei or S. flexneri, yet the clinical features of the disease are more severe in later observations. CONCLUSIONS: Our findings show a change in clinical presentation of shigellosis in this setting, as the disease may be now more pronounced, this is concurrent with a change in antimicrobial resistance profile. These data highlight the socio-economic development of southern Vietnam and should guide future vaccine development and deployment strategies. TRIAL REGISTRATION: Current Controlled Trials ISRCTN55945881.


Subject(s)
Dysentery, Bacillary/epidemiology , Dysentery, Bacillary/microbiology , Child, Preschool , Drug Resistance, Multiple, Bacterial , Female , Humans , Infant , Male , Microbial Sensitivity Tests , Seasons , Serotyping , Shigella flexneri/classification , Shigella flexneri/drug effects , Shigella flexneri/pathogenicity , Shigella sonnei/classification , Shigella sonnei/drug effects , Shigella sonnei/pathogenicity , Vietnam/epidemiology
8.
Clin Infect Dis ; 46(5): 659-67, 2008 Mar 01.
Article in English | MEDLINE | ID: mdl-19413493

ABSTRACT

BACKGROUND: Streptococcus suis infection is an emerging zoonosis in Asia. We determined the detailed epidemiological, clinical, and microbiological characteristics of S. suis meningitis in adults. METHODS: We prospectively studied 450 patients with suspected bacterial meningitis. Four hundred thirty-five (96.7%) of the patients participated in a trial to determine the effect of adjunctive dexamethasone treatment. For patients with S. suis infection, bacterial DNA load at hospital admission and during treatment was analyzed in cerebrospinal fluid specimens using quantitative real-time polymerase chain reaction. S. suis strains were characterized using pulsed-field gel electrophoresis and multilocus sequence typing. Putative virulence factors, including extracellular protein factor, suilysin, and muramidase released protein, were detected using polymerase chain reaction and Western blot assay. Predictors of outcome were identified using logistic regression analysis. RESULTS: S. suis was the most common pathogen and was detected in 151 (33.6%) of the patients. Fifty (33.1%) of these 151 patients reported exposure to pigs or pork. Mortality was low (2.6%; 4 of 151 patients died), but mild to severe hearing loss occurred in 93 (66.4%) of 140 patients. Severe deafness at hospital discharge was associated with age >50 years (odds ratio, 3.65; 95% confidence interval, 1.15-11.6), a strain carrying the epf gene (odds ratio, 3.42; 95% confidence interval, 1.02-11.4), and dexamethasone therapy (odds ratio, 0.23; 95% confidence interval, 0.06-0.78) but was not associated with cerebrospinal fluid bacterial DNA load. Bacterial DNA was still detectable in 58 (63%) of 92 cerebrospinal fluid samples after 6-10 days of antimicrobial treatment. Ninety-one of 92 S. suis strains had serotype 2. Thirty-three (36%) of these epidemiologically unrelated strains belonged to 1 pulsed-field gel electrophoresis cluster of multilocus sequence type 1, indicating clonal spread. CONCLUSION: S. suis serotype 2 is the most frequent cause of bacterial meningitis in adults in southern Vietnam and is associated with substantial morbidity attributable to hearing loss.


Subject(s)
DNA, Bacterial/isolation & purification , Meningitis, Bacterial/epidemiology , Streptococcal Infections/epidemiology , Streptococcus suis/genetics , Adult , Aged , Aged, 80 and over , Analysis of Variance , Animals , DNA, Bacterial/genetics , Dexamethasone/therapeutic use , Female , Glasgow Coma Scale , Humans , Male , Middle Aged , Neisseria meningitidis/genetics , Neisseria meningitidis/isolation & purification , Streptococcus pneumoniae/genetics , Streptococcus pneumoniae/isolation & purification , Streptococcus suis/isolation & purification , Treatment Outcome , Vietnam/epidemiology , Young Adult , Zoonoses/epidemiology
9.
Am J Trop Med Hyg ; 99(3_Suppl): 72-78, 2018 09.
Article in English | MEDLINE | ID: mdl-30047368

ABSTRACT

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.


Subject(s)
Anti-Bacterial Agents/pharmacology , Typhoid Fever/epidemiology , Typhoid Fever/prevention & control , Adolescent , Child , Child, Preschool , Genotype , Humans , Public Health Administration , Salmonella typhi/drug effects , Salmonella typhi/genetics , Typhoid-Paratyphoid Vaccines/immunology , Vaccination , Vietnam/epidemiology
10.
J Med Microbiol ; 66(1): 46-53, 2017 Jan.
Article in English | MEDLINE | ID: mdl-28198682

ABSTRACT

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 aim of this study was to determine the prevalence of antimicrobial-resistant A. baumannii associated with infection in three hospitals in southern Vietnam and to characterize the genetic determinants associated with resistance against carbapenems. We recovered a total of 160 A. baumannii isolates from clinical samples collected in three hospitals in southern Vietnam from 2012 to 2014. Antimicrobial resistance was common; 119/160 (74 %) of isolates were both MDR and extensively drug resistant (XDR). High-level imipenem resistance (>32 µg ml-1) was determined for 109/117 (91.6 %) of the XDR imipenem-nonsusceptible organisms, of which the majority (86.7 %) harboured the blaOXA-51 and blaOXA-23 genes associated with an ISAba1 element. Multiple-locus variable number tandem repeat analysis segregated the 160 A. baumannii into 107 different multiple-locus variable number tandem repeat analysis types, which described five major clusters. The biggest cluster was a clonal complex composed mainly of imipenem-resistant organisms that were isolated from all three of the study hospitals. Our study indicates a very high prevalence of MDR/XDR A. baumannii causing clinically significant infections in hospitals in southern Vietnam. These organisms commonly harboured the blaOXA-23 gene with ISAba1 and were carbapenem resistant; this resistance phenotype may explain their continued selection and ongoing transmission within the Vietnamese healthcare system.


Subject(s)
Acinetobacter Infections/epidemiology , Acinetobacter baumannii/genetics , Bacterial Proteins/genetics , Cross Infection/epidemiology , Drug Resistance, Multiple, Bacterial/genetics , Acinetobacter Infections/microbiology , Acinetobacter baumannii/isolation & purification , Adult , Aged , Aged, 80 and over , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/metabolism , Carbapenems/pharmacology , Cluster Analysis , Cross Infection/microbiology , DNA, Bacterial/genetics , Female , Hospitals , Humans , Imipenem/pharmacology , Longitudinal Studies , Male , Middle Aged , Molecular Epidemiology , Multilocus Sequence Typing , Phenotype , Prevalence , Tandem Repeat Sequences , Vietnam/epidemiology , Young Adult , beta-Lactamases/genetics , beta-Lactamases/metabolism
11.
Am J Trop Med Hyg ; 92(5): 1045-52, 2015 May.
Article in English | MEDLINE | ID: mdl-25802437

ABSTRACT

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 (75.2%) children with diarrhea and from 81/609 (13.3%) children without diarrhea. Rotavirus predominated in the symptomatic children (664/1,419; 46.8%), followed by norovirus (293/1,419; 20.6%). The bacterial pathogens Salmonella, Campylobacter, and Shigella were cumulatively isolated from 204/1,419 (14.4%) diarrheal children and exhibited extensive antimicrobial resistance, most notably to fluoroquinolones and third-generation cephalosporins. We suggest renewed efforts in generation and implementation of policies to control the sale and prescription of antimicrobials to curb bacterial resistance and advise consideration of a subsidized rotavirus vaccination policy to limit the morbidity due to diarrheal disease in Vietnam.


Subject(s)
Bacterial Infections/epidemiology , Caliciviridae Infections/epidemiology , Diarrhea/complications , Norovirus/isolation & purification , Rotavirus Infections/epidemiology , Anti-Infective Agents/pharmacology , Bacteria/drug effects , Bacterial Infections/complications , Bacterial Infections/microbiology , Caliciviridae Infections/complications , Caliciviridae Infections/microbiology , Child, Preschool , Cross-Sectional Studies , Demography , Diarrhea/epidemiology , Diarrhea/microbiology , Female , Hospitalization , Humans , Infant , Male , Microbial Sensitivity Tests , Norovirus/drug effects , Prospective Studies , Rotavirus/drug effects , Rotavirus/isolation & purification , Rotavirus Infections/complications , Rotavirus Infections/microbiology , Seasons , Vietnam/epidemiology
12.
Am J Trop Med Hyg ; 90(1): 114-120, 2014 Jan.
Article in English | MEDLINE | ID: mdl-24218407

ABSTRACT

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. There were 32 cases of TF (10 BC- and PCR-positive cases, 14 BC-positive and PCR-negative cases, and 8 BC-negative and PCR-positive cases). IgMFA sensitivity was 59.4% (95% confidence interval = 41-76), and specificity was 97.8% (95% confidence interval = 96-99). The model estimate sensitivity for BC was 81.0% (95% credible interval = 54-99). The model estimate sensitivity for PCR was 37.8% (95% credible interval = 26-55), with a specificity of 98.2% (95% credible interval = 97-99). The model estimate sensitivity for IgMFA (≥ 2+) was 77.9% (95% credible interval = 58-90), with a specificity of 97.5% (95% credible interval = 95-100). The model estimates of IgMFA sensitivity and specificity were comparable with BCs and better than estimates using conventional analysis.


Subject(s)
Immunoglobulin M/blood , Typhoid Fever/diagnosis , Bayes Theorem , Cambodia/epidemiology , Child , Child, Preschool , Female , Humans , Male , Polymerase Chain Reaction/methods
13.
J Med Microbiol ; 63(Pt 10): 1386-1394, 2014 Oct.
Article in English | MEDLINE | ID: mdl-25038137

ABSTRACT

Ventilator-associated pneumonia (VAP) is a serious healthcare-associated infection that affects up to 30 % of intubated and mechanically ventilated patients in intensive care units (ICUs) worldwide. The bacterial aetiology and corresponding antimicrobial susceptibility of VAP is highly variable, and can differ between countries, national provinces and even between different wards in the same hospital. We aimed to understand and document changes in the causative agents of VAP and their antimicrobial susceptibility profiles retrospectively over an 11 year period in a major infectious disease hospital in southern Vietnam. Our analysis outlined a significant shift from Pseudomonas aeruginosa to Acinetobacter spp. as the most prevalent bacteria isolated from quantitative tracheal aspirates in patients with VAP in this setting. Antimicrobial resistance was common across all bacterial species and we found a marked proportional annual increase in carbapenem-resistant Acinetobacter spp. over a 3 year period from 2008 (annual trend; odds ratio 1.656, P = 0.010). We further investigated the possible emergence of a carbapenem-resistant Acinetobacter baumannii clone by multiple-locus variable number tandem repeat analysis, finding a blaOXA-23-positive strain that was associated with an upsurge in the isolation of this pathogen. We additionally identified a single blaNDM-1-positive A. baumannii isolate. This work highlights the emergence of a carbapenem-resistant clone of A. baumannii and a worrying trend of antimicrobial resistance in the ICU of the Hospital for Tropical Diseases in Ho Chi Minh City, Vietnam.


Subject(s)
Acinetobacter Infections/microbiology , Acinetobacter baumannii/drug effects , Carbapenems/pharmacology , Pneumonia, Ventilator-Associated/microbiology , beta-Lactam Resistance , Acinetobacter Infections/epidemiology , Acinetobacter baumannii/isolation & purification , Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Female , Genotype , Hospitals , Humans , Intensive Care Units , Male , Middle Aged , Molecular Epidemiology , Multilocus Sequence Typing , Pneumonia, Ventilator-Associated/epidemiology , Prevalence , Retrospective Studies , Vietnam/epidemiology , Young Adult
14.
J Infect Dev Ctries ; 7(12): 922-8, 2013 Dec 15.
Article in English | MEDLINE | ID: mdl-24334938

ABSTRACT

BACKGROUND: Extended-spectrum ß-lactamases (ESBLs) are enzymes capable of hydrolyzing oxyimino-ß-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. coli and Klebsiella pneumoniae causing nosocomial infections in hospitals in Ho Chi Minh City, Vietnam. METHODOLOGY: Thirty-two non-duplicate isolates of E. coli and Klebsiella pneumoniae causing nosocomial infections, isolated between March and June 2010, were subjected to antimicrobial susceptibility testing. All isolates were PCR-amplified to detect the blaSHV, blaTEM and blaCTX-M ESBL genes and subjected to plasmid analysis. RESULTS: We found that co-resistance to multiple antimicrobials was highly prevalent, and we report the predominance of the blaCTX-M-15 and blaCTX-M-27 genes, located on highly transmissible plasmids ranging from 50 to 170 kb in size. CONCLUSIONS: Our study represents a snap shot of ESBL-producing enteric bacteria causing nosocomial infections in this setting. We suggest that antimicrobial resistance in nosocomial E. coli and Klebsiella pneumoniae is rampant in Vietnam and ESBL organisms are widespread. In view of these data and the dramatic levels of antimicrobial resistance reported in Vietnam we advocate an urgent review of antimicrobial use in the Vietnamese healthcare system.


Subject(s)
Cross Infection/microbiology , Escherichia coli Infections/microbiology , Escherichia coli/enzymology , Klebsiella Infections/microbiology , Klebsiella pneumoniae/enzymology , beta-Lactamases/genetics , Anti-Bacterial Agents/pharmacology , DNA, Bacterial/genetics , Escherichia coli/genetics , Escherichia coli/isolation & purification , Genes, Bacterial , Humans , Klebsiella pneumoniae/genetics , Klebsiella pneumoniae/isolation & purification , Microbial Sensitivity Tests , Plasmids/analysis , Polymerase Chain Reaction , Vietnam , beta-Lactam Resistance
15.
Sci Rep ; 3: 1043, 2013.
Article in English | MEDLINE | ID: mdl-23304434

ABSTRACT

Current serological diagnostic assays for typhoid fever are based on detecting antibodies against Salmonella LPS or flagellum, resulting in a high false-positive rate. Here we used a protein microarray containing 2,724 Salmonella enterica serovar Typhi antigens (>63% of proteome) and identified antibodies against 16 IgG antigens and 77 IgM antigens that were differentially reactive among acute typhoid patients and healthy controls. The IgG target antigens produced a sensitivity of 97% and specificity of 80%, whereas the IgM target antigens produced 97% and 91% sensitivity and specificity, respectively. Our analyses indicated certain features such as membrane association, secretion, and protein expression were significant enriching features of the reactive antigens. About 72% of the serodiagnostic antigens were within the top 25% of the ranked antigen list using a Naïve bayes classifier. These data provide an important resource for improved diagnostics, therapeutics and vaccine development against an important human pathogen.


Subject(s)
Antibodies, Bacterial/analysis , Antigens/immunology , Protein Array Analysis , Salmonella typhi/metabolism , Typhoid Fever/diagnosis , Antigens/genetics , Antigens/metabolism , Biomarkers/analysis , Cloning, Molecular , Humans , Immunoglobulin G/analysis , Immunoglobulin M/analysis , Proteome/immunology , Proteome/metabolism , ROC Curve , Sensitivity and Specificity
16.
Elife ; 2: e01229, 2013 Dec 10.
Article in English | MEDLINE | ID: mdl-24327559

ABSTRACT

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. Using in vitro competition experiments, we assayed the fitness of eleven isogenic S. Typhi strains with resistance mutations in the FQ target genes, gyrA and parC. In the absence of antimicrobial pressure, 6 out of 11 mutants carried a selective advantage over the antimicrobial-sensitive parent strain, indicating that FQ resistance in S. Typhi is not typically associated with fitness costs. Double-mutants exhibited higher than expected fitness as a result of synergistic epistasis, signifying that epistasis may be a critical factor in the evolution and molecular epidemiology of S. Typhi. Our findings have important implications for the management of drug-resistant S. Typhi, suggesting that FQ-resistant strains would be naturally maintained even if fluoroquinolone use were reduced. DOI: http://dx.doi.org/10.7554/eLife.01229.001.


Subject(s)
Anti-Bacterial Agents/pharmacology , Fluoroquinolones/pharmacology , Salmonella typhi/drug effects , Drug Resistance, Microbial/genetics , Epistasis, Genetic/drug effects , Microbial Sensitivity Tests , Mutation , Salmonella typhi/genetics
17.
PLoS Negl Trop Dis ; 7(8): e2335, 2013.
Article in English | MEDLINE | ID: mdl-23936575

ABSTRACT

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. Typhi carriage. METHODOLOGY/PRINCIPAL FINDINGS: To study host-pathogen interactions in the biliary tract during S. Typhi carriage, we applied an immunoscreening technique called in vivo-induced antigen technology (IVIAT), to identify potential biomarkers unique to carriers. IVIAT identifies humorally immunogenic bacterial antigens expressed uniquely in the in vivo environment, and we hypothesized that S. Typhi surviving in the biliary tract of humans may express a distinct antigenic profile. Thirteen S. Typhi antigens that were immunoreactive in carriers, but not in healthy individuals from a typhoid endemic area, were identified. The identified antigens included a number of putative membrane proteins, lipoproteins, and hemolysin-related proteins. YncE (STY1479), an uncharacterized protein with an ATP-binding motif, gave prominent responses in our screen. The response to YncE in patients whose biliary tract contained S. Typhi was compared to responses in patients whose biliary tract did not contain S. Typhi, patients with acute typhoid fever, and healthy controls residing in a typhoid endemic area. Seven of 10 (70%) chronic carriers, 0 of 8 bile culture-negative controls (0%), 0 of 8 healthy Bangladeshis (0%), and 1 of 8 (12.5%) Bangladeshis with acute typhoid fever had detectable anti-YncE IgG in blood. IgA responses were also present. CONCLUSIONS/SIGNIFICANCE: Further evaluation of YncE and other antigens identified by IVIAT could lead to the development of improved diagnostic assays to identify asymptomatic S. Typhi carriers.


Subject(s)
Antigens, Bacterial/analysis , Biliary Tract/microbiology , Carrier State/microbiology , Host-Pathogen Interactions , Salmonella typhi/immunology , Typhoid Fever/microbiology , Adult , Antigens, Bacterial/immunology , Child , Child, Preschool , Gene Expression Profiling , Humans , Nepal
18.
J Virol Methods ; 187(1): 138-43, 2013 Jan.
Article in English | MEDLINE | ID: mdl-23046990

ABSTRACT

Rotavirus (RoV) and Norovirus (NoV) are the main causes of viral gastroenteritis. Currently, there is no validated multiplex real-time PCR that can detect and quantify RoV and NoV simultaneously. The aim of the study was to develop, validate, and internally control a multiplex one-step RT real-time PCR to detect and quantify RoV and NoV in stool samples. PCR sensitivity was assessed by comparing amplification against the current gold standard, enzyme immunoassay (EIA), on stool samples from 94 individuals with diarrhea and 94 individuals without diarrhea. PCR detected 10% more RoV positive samples than EIA in stools samples from patients with diarrhea. PCR detected 23% more NoV genogroup II positive samples from individuals with diarrhea and 9% more from individuals without diarrhea than EIA, respectively. Genotyping of the PCR positive/EIA negative samples suggested the higher rate of PCR positivity, in comparison to EIA, was due to increased sensitivity, rather than nonspecific hybridization. Quantitation demonstrated that the viral loads of RoV and NoV in the stools of diarrheal patients were an order of magnitude greater than in individuals without diarrhea. This internally controlled real-time PCR method is robust, exhibits a high degree of reproducibility, and may have a greater utility and sensitivity than commercial EIA kits.


Subject(s)
Caliciviridae Infections/diagnosis , Multiplex Polymerase Chain Reaction , Norovirus/isolation & purification , Real-Time Polymerase Chain Reaction , Rotavirus Infections/diagnosis , Rotavirus/isolation & purification , Caliciviridae Infections/virology , Child, Preschool , Diarrhea/diagnosis , Diarrhea/virology , Feces/virology , Gastroenteritis/diagnosis , Gastroenteritis/genetics , Genotype , Humans , Infant , Infant, Newborn , Norovirus/genetics , RNA, Viral/analysis , Reproducibility of Results , Reverse Transcriptase Polymerase Chain Reaction , Rotavirus/genetics , Rotavirus Infections/virology
19.
PLoS One ; 7(8): e42919, 2012.
Article in English | MEDLINE | ID: mdl-22937000

ABSTRACT

Antimicrobial consumption is one of the major contributing factors facilitating the development and maintenance of bacteria exhibiting antimicrobial resistance. Plasmid-mediated quinolone resistance (PMQR) genes, such as the qnr family, can be horizontally transferred and contribute to reduced susceptibility to fluoroquinolones. We performed an observational study, investigating the copy number of PMQR after antimicrobial therapy. We enrolled 300 children resident in Ho Chi Minh City receiving antimicrobial therapy for acute respiratory tract infections (ARIs). Rectal swabs were taken on enrollment and seven days subsequently, counts for Enterobacteriaceae were performed and qnrA, qnrB and qnrS were quantified by using real-time PCR on metagenomic stool DNA. On enrollment, we found no association between age, gender or location of the participants and the prevalence of qnrA, qnrB or qnrS. Yet, all three loci demonstrated a proportional increase in the number of samples testing positive between day 0 and day 7. Furthermore, qnrB demonstrated a significant increase in copy number between paired samples (p<0.001; Wilcoxon rank-sum), associated with non-fluoroquinolone combination antimicrobial therapy. To our knowledge, this is the first study describing an association between the use of non-fluoroquinolone antimicrobials and the increasing relative prevalence and quantity of qnr genes. Our work outlines a potential mechanism for the selection and maintenance of PMQR genes and predicts a strong effect of co-selection of these resistance determinants through the use of unrelated and potentially unnecessary antimicrobial regimes.


Subject(s)
Anti-Bacterial Agents/pharmacology , Fluoroquinolones/pharmacology , Gastrointestinal Tract/microbiology , Bacterial Proteins/genetics , Child, Preschool , Citrobacter/drug effects , Citrobacter/genetics , Drug Resistance, Bacterial/immunology , Enterobacteriaceae/drug effects , Enterobacteriaceae/genetics , Escherichia coli/drug effects , Escherichia coli/genetics , Female , Humans , Infant , Klebsiella/drug effects , Klebsiella/genetics , Male , Microbial Sensitivity Tests , Pantoea/drug effects , Pantoea/genetics , Plasmids/genetics , Proteus/drug effects , Proteus/genetics , Real-Time Polymerase Chain Reaction , Shigella/drug effects , Shigella/genetics
20.
Trans R Soc Trop Med Hyg ; 106(12): 718-24, 2012 Dec.
Article in English | MEDLINE | ID: mdl-23122884

ABSTRACT

Infections with Salmonella enterica serovar Typhi isolates that are multidrug resistant (MDR: resistant to chloramphenicol, ampicillin, trimethoprim-sulphamethoxazole) with intermediate ciprofloxacin susceptibility are widespread in Asia but there is little information from Cambodia. We studied invasive salmonellosis in children at a paediatric hospital in Siem Reap, Cambodia. Between 2007 and 2011 Salmonella was isolated from a blood culture in 162 children. There were 151 children with enteric fever, including 148 serovar Typhi and three serovar Paratyphi A infections, and 11 children with a non-typhoidal Salmonella infection. Of the 148 serovar Typhi isolates 126 (85%) were MDR and 133 (90%) had intermediate ciprofloxacin susceptibility. Inpatient antimicrobial treatment was ceftriaxone alone or initial ceftriaxone followed by a step-down to oral ciprofloxacin or azithromycin. Complications developed in 37/128 (29%) children admitted with enteric fever and two (1.6%) died. There was one confirmed relapse. In a sample of 102 serovar Typhi strains genotyped by investigation of a subset of single nucleotide polymorphisms, 98 (96%) were the H58 haplotype, the majority of which had the common serine to phenylalanine substitution at codon 83 in the DNA gyrase. We conclude that antimicrobial-resistant enteric fever is common in Cambodian children and therapeutic options are limited.


Subject(s)
Anti-Infective Agents/pharmacology , Ciprofloxacin/pharmacology , Drug Resistance, Multiple, Bacterial , Hospitals, Pediatric , Salmonella typhi/genetics , Typhoid Fever/microbiology , Adult , Age Distribution , Anti-Infective Agents/therapeutic use , Azithromycin/pharmacology , Azithromycin/therapeutic use , Cambodia/epidemiology , Ceftriaxone/pharmacology , Ceftriaxone/therapeutic use , Child , Child Mortality , Child, Preschool , Ciprofloxacin/therapeutic use , Cross-Sectional Studies , Female , Haplotypes , Humans , Male , Microbial Sensitivity Tests , Polymorphism, Single Nucleotide , Retrospective Studies , Salmonella typhi/drug effects , Salmonella typhi/isolation & purification , Treatment Outcome , Typhoid Fever/drug therapy , Typhoid Fever/epidemiology
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