[Show abstract][Hide abstract] ABSTRACT: We characterized Salmonella enterica serovar Typhi isolates from Bangladesh, Indonesia, Taiwan, and Vietnam to investigate their genetic relatedness and antimicrobial
resistance. The isolates from Bangladesh and Vietnam were genetically closely related but were distant from those from Indonesia
and Taiwan. All but a few isolates from Indonesia and Taiwan were susceptible to all antimicrobials tested. The majority of
isolates from Bangladesh and Vietnam were multidrug resistant (MDR) and belonged to the widespread haplotype H58 clone. IncHI1
plasmids were detected in all MDR S. Typhi isolates from Vietnam but in only 15% of MDR isolates from Bangladesh. Resistance genes in the majority of MDR S. Typhi isolates from Bangladesh should reside in the chromosome. Among the isolates from Bangladesh, 82% and 40% were resistant
to various concentrations of nalidixic acid and ciprofloxacin, respectively. Several resistance mechanisms, including alterations
in gyrase A, the presence of QnrS, and enhanced efflux pumps, were involved in the reduced susceptibility and resistance to
fluoroquinolones. Intensive surveillance is necessary to monitor the spread of chromosome-mediated MDR and fluoroquinolone-resistant
S. Typhi emerging in Bangladesh.
Full-text · Article · Aug 2014 · Antimicrobial Agents and Chemotherapy
[Show abstract][Hide abstract] ABSTRACT: Aim: To compare cheaper and simpler once-daily regimens, with and without a proton pump inhibitor, with standard, twice-daily, triple therapy. Methods: A randomized, placebo-controlled, treatment trial in Vietnam allocated 296 Helicobacter pylori-infected patients with peptic ulcer of 5 mm to one of three regimens: (i) twice-daily: lansoprazole 30 mg, clarithromycin 250 mg and tinidazole 500 mg; (ii) once-daily: lansoprazole 60 mg, clarithromycin 500 mg and tinidazole 1000 mg; (iii) once-daily: pla-cebo, clarithromycin 500 mg and tinidazole 1000 mg. H. pylori status was assessed by culture and immunoblot, ulcer healing by endoscopy and side-effects by structured questionnaires. Results: Per protocol eradication (N ¼ 256) was higher with standard therapy (87%) than with once-daily therapy (72%), and both were better than once-daily therapy without proton pump inhibitor (39%). Per protocol ulcer healing after standard therapy (83%) was not significantly better than that after once-daily therapy (73%), but better than that after therapy without proton pump inhibitor (65%). Side-effects were reported at similar rates in all groups. Conclusions: Proton pump inhibitor was needed for optimal eradication and ulcer healing. Twice-daily administration showed improved success rates when compared with once-daily therapies. Peptic ulcer heal-ing was achieved even in patients treated with ant-ibiotics only, confirming the central role of H. pylori in the pathophysiology of peptic ulcer disease.
[Show abstract][Hide abstract] ABSTRACT: Aim: To assess the long-term Helicobacter pylori reinfec-tion rates, as well as the clinical outcome in peptic ulcer disease patients in Vietnam. Method: At a 1-year evaluation of H. pylori eradication treatment in 226 peptic ulcer patients, long-term H. pylori status was assessed with serology and/or culture, peptic ulcer status by gastroscopy, and DNA-fingerprinting performed with random amplified poly-morphic DNA and restriction fragment polymorphism. Result: Follow-up was performed a mean 11 months after the post-treatment evaluation on day 30 after beginning of treatment. The overall reinfection rate was 23.5%, with 58.8% of the strains being identical to the pre-treatment isolates and 41.2% being different. Peptic ulcer was found in 22.9% of the reinfected patients and in 6.3% of the non-reinfected. At the long-term follow-up of successful eradication cases, 89.8% of the patients were free of peptic ulcer disease. The corresponding result was 58.7% in patients in whom H. pylori eradication failed. Conclusion: Following successful H. pylori eradication, reinfection with H. pylori in patients in Vietnam was found to be higher than in industrialized countries but the long-term recurrence of peptic ulcer disease was still low. Helicobacter pylori eradication treatment is therefore of value also in developing countries as the rate of peptic ulcer disease was low at the 1-year follow-up.
[Show abstract][Hide abstract] ABSTRACT: Low Helicobacter pylori eradication rates are common in pediatric trials especially in developing countries. The aim of the study was to investigate the role of antibiotic resistance, drug dosage, and administration frequency on treatment outcome for children in Vietnam.
Antibiotics resistance of H. pylori was analyzed by the Etest in 222 pretreatment isolates from children 3-15 years of age who were originally recruited in a randomized trial with two treatment regiments: lansoprazole with amoxicillin and either clarithromycin (LAC) or metronidazole (LAM) in two weight groups with once- or twice-daily administration. The study design was an observational study embedded in a randomized trial.
The overall resistance to clarithromycin, metronidazole, and amoxicillin was 50.9%, 65.3%, and 0.5%, respectively. In LAC, eradication was linked to the strains being susceptible to clarithromycin (78.2% vs 29.3%, p = .0001). Twice-daily dosage of proton-pump inhibitor (PPI) and clarithromycin was more effective for eradication than once-daily dosage for resistant strains (50.0% vs 14.7%, p = .004) and tended to be so also for sensitive strains (87.5% vs 65.2%, p = .051). Exact antibiotic dose per body weight resulted in more eradication for resistant strains (45.3% vs 8.0%, p = .006). These differences were less pronounced for the LAM regimen, with twice-daily PPI versus once daily for resistant strains resulting in 69.2% and 50.0% eradication (p = .096), respectively. CONClUSIONS: Helicobacter pylori clarithromycin resistance was unexpectedly high in young children in Vietnam. Clarithromycin resistance was an important cause for eradication treatment failure. Twice-daily administration and exact antibiotic dosing resulted in more eradicated infections when the strains were antibiotic resistant, which has implications for the study design in pediatric H. pylori eradication trials.
[Show abstract][Hide abstract] ABSTRACT: The determinants for acquisition of Helicobacter pylori infection remain incompletely understood. The study aim was to investigate risk factors for recurrence in children in Vietnam during 1 year immediately following successful H. pylori eradication.
In a prospective longitudinal study, 136 children, 3-15 years of age, were seen every 3 months for a total of four visits. Helicobacter pylori infection status was determined by an antigen-in-stool test (Premier Platinum HpSA PLUS) on samples obtained at each visit. A questionnaire was filled out at the start of the study.
After 1 year, 30 children had become H. pylori positive, while 17 were lost to follow-up. Low age was the most prominent independent risk factor for recurrence: adjusted hazard ratio (HR) among children aged 3-4, 5-6, and 7-8 years, relative to those aged 9-15 years, were, respectively, 14.3 [95% CI 3.8-53.7], 5.4 [1.8-16.3] and 2.6 [0.7-10.4]. Surprisingly, female sex tended to be associated with increased risk (adjusted HR among girls relative to boys 2.5 [95% CI 1.1-5.9]). No other factors such as sibship size, birth order, bed sharing, sanitary standards, or factual antibiotic dose per kilo bodyweight in the eradication trial were found to be significant risk factors for re-infection.
The main risk factor for recurrence with H. pylori was found to be age, with the youngest children running the greatest risk. The finding lends support to the observation that early childhood may be the main age of acquisition of H. pylori infection and for postponing attempts of eradication in high-prevalence areas unless motivated for medical reasons.
[Show abstract][Hide abstract] ABSTRACT: To investigate global epidemiology of Shigella sonnei, we performed multilocus variable number tandem repeat analysis of 1,672 isolates obtained since 1943 from 50 countries on 5 continents and the Pacific region. Three major clonal groups were identified; 2 were globally spread. Type 18 and its derivatives have circulated worldwide in recent decades.
Full-text · Article · Oct 2011 · Emerging Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: Shigella flexneri is one of the causative agents of shigellosis, a major cause of childhood mortality in developing countries. Multilocus variable-number tandem repeat (VNTR) analysis (MLVA) is a prominent subtyping method to resolve closely related bacterial isolates for investigation of disease outbreaks and provide information for establishing phylogenetic patterns among isolates. The present study aimed to develop an MLVA method for S. flexneri and the VNTR loci identified were tested on 242 S. flexneri isolates to evaluate their variability in various serotypes. The isolates were also analyzed by pulsed-field gel electrophoresis (PFGE) to compare the discriminatory power and to evaluate the usefulness of MLVA as a tool for phylogenetic analysis of S. flexneri.
Thirty-six VNTR loci were identified by exploring the repeat sequence loci in genomic sequences of Shigella species and by testing the loci on nine isolates of different subserotypes. The VNTR loci in different serotype groups differed greatly in their variability. The discriminatory power of an MLVA assay based on four most variable VNTR loci was higher, though not significantly, than PFGE for the total isolates, a panel of 2a isolates, which were relatively diverse, and a panel of 4a/Y isolates, which were closely-related. Phylogenetic groupings based on PFGE patterns and MLVA profiles were considerably concordant. The genetic relationships among the isolates were correlated with serotypes. The phylogenetic trees constructed using PFGE patterns and MLVA profiles presented two distinct clusters for the isolates of serotype 3 and one distinct cluster for each of the serotype groups, 1a/1b/NT, 2a/2b/X/NT, 4a/Y, and 6. Isolates that had different serotypes but had closer genetic relatedness than those with the same serotype were observed between serotype Y and subserotype 4a, serotype X and subserotype 2b, subserotype 1a and 1b, and subserotype 3a and 3b.
The 36 VNTR loci identified exhibited considerably different degrees of variability among S. flexneri serotype groups. VNTR locus could be highly variable in a serotype but invariable in others. MLVA assay based on four highly variable loci could display a comparable resolving power to PFGE in discriminating isolates. MLVA is also a prominent molecular tool for phylogenetic analysis of S. flexneri; the resulting data are beneficial to establish clear clonal patterns among different serotype groups and to discern clonal groups among isolates within the same serotype. As highly variable VNTR loci could be serotype-specific, a common MLVA protocol that consists of only a small set of loci, for example four to eight loci, and that provides high resolving power to all S. flexneri serotypes may not be obtainable.
[Show abstract][Hide abstract] ABSTRACT: A panel of 916 isolates, including 703 closely related IST1 isolates, were characterized by inter-IS1 spacer typing (IST), pulsed-field gel electrophoresis (PFGE), and multilocus variable-number tandem-repeat (VNTR) analysis
(MLVA) to evaluate the utility of MLVA as a molecular tool for the phylogenetic analysis of Shigella sonnei. The global phylogenetic patterns determined by IST, PFGE, and MLVA were concordant. MLVA was carried out using 26 VNTR loci
with a range of degrees of variability. MLVA data for the 703 IST1 isolates revealed that diversification among the closely
related isolates was attributed mainly to four highly variable loci. The phylogenetic pattern for the closely related isolates
determined using MLVA profiles of 8 highly variable loci was in agreement with that determined using the 26-locus profiles.
A clustering analysis using the profiles of 18 loci with limited variability established clear phylogenetic relationships
among IST clonal groups. Accordingly, MLVA is a useful tool for the phylogenetic analysis of S. sonnei. Combined VNTR loci with higher variability are useful markers for resolving closely related isolates, whereas combined loci
with lower variability are suitable for establishing clear phylogenetic relationships between strains or clones that have
evolved over a longer timescale.
Full-text · Article · Mar 2009 · Journal of clinical microbiology
[Show abstract][Hide abstract] ABSTRACT: Eradication of Helicobacter pylori infection in children in developing countries needs further investigations upon which to base treatment recommendations. The aim of the study was to compare two 2-week triple therapies in a randomized double-blind trial.
In order not to exceed recommended dosages, the 238 H. pylori-infected children, aged 3 to 15 years (mean 8.6), were divided in two weight categories receiving at weights 13-22 kg: lansoprazole 15 mg once-daily and amoxicillin 500 mg twice-daily with metronidazole 250 mg twice-daily or clarithromycin 250 mg once-daily; at weights 23-45 kg: lansoprazole 15 mg and amoxicillin 750 mg with metronidazole 500 mg or clarithromycin 250 mg, all administered twice daily. H. pylori status was assessed by culture and a monoclonal-based antigen-in-stool test (Premier Platinum HpSA PLUS) and side effects by structured questionnaires.
The overall per-protocol eradication (n = 233) was similar in the two treatment regimens, 62.1% for the metronidazole and 54.7% for the clarithromycin-containing therapy. Eradication rate was higher in children >or= 23 kg (70.9%) than in children < 23 kg (45.7%). In children >or= 23 kg (n = 117) that received twice-daily administration of all drugs, efficacy of the metronidazole and clarithromycin-containing treatments were 69.5% and 72.4%, respectively.
The two treatments gave similar eradication rates. Significant differences for both treatments were found by weight, which could be the result of the once-daily proton pump inhibitor and clarithromycin and/or more antibiotic resistant strains in younger children.
[Show abstract][Hide abstract] ABSTRACT: To determine the occurrence of and risk factors for diarrhoea in an adult population exposed to wastewater used for agricultural and aquacultural productions.
An open cohort of 636 adults aged 15-70 years living in a wastewater-irrigated area in Hanoi was followed by weekly visit for 18 months. The aetiology and risk factors for diarrhoeal diseases were determined in a nested case-control study. Stool specimens and exposure information related to wastewater, hygiene, water and food consumption were collected from 163 unmatched pairs of cases and controls.
The incidence rate of diarrhoeal diseases was 28.1 episodes per 100 person-years at risk. Of the 326 stool specimens, 47 cases and 24 controls were identified with enteric pathogens, of which diarrhoeagenic Escherichia coli and Entamoeba histolytica were the most common. Risk factors for diarrhoeal diseases included contact with wastewater [odds ratio (OR) = 1.98, attributable fraction of the population (AF) 35%], not washing hands after defecation (OR = 3.34, AF 3%), drinking water from a well (OR = 6.21, AF 6%), consumption of raw or undercooked foods (OR = 2.45, AF 6%), and contact with persons with diarrhoea (OR = 4.22, AF 5%).
Wastewater contact was the principal risk factor for diarrhoea in this population. As the local economy depends on the use of wastewater for agriculture and aquaculture, it is important to find ways to mitigate the public health risks associated with this use, in addition to promotions of personal, domestic and food hygiene.
Full-text · Article · Jan 2008 · Tropical Medicine & International Health
[Show abstract][Hide abstract] ABSTRACT: To identify the level of contamination with thermotolerant coliforms (ThC), intestinal helminth eggs and protozoan parasites in water spinach (Ipomoea aquatica) cultivated in a wastewater-fed lake in Phnom Penh, Cambodia.
The investigation was carried out from July 2004 to May 2005 in Boeng Cheung Ek lake, a main recipient of wastewater from the city of Phnom Penh. Water spinach samples were collected near two wastewater entry points in the northern part of the lake and near a wastewater exit point in the southern part of the lake, where water is discharged from the lake into a stream. Water spinach samples were harvested at each of the three locations with and without wastewater contact according to the normal practices of farmers, and analysed for ThC, protozoan parasites (Giardia, Cryptosporidium and Cyclospora), and helminth eggs (Ascaris lumbricoides, Trichuris trichura and hookworm) using standard methods. Wastewater samples were also collected at each of the three locations and analysed for ThC and helminth eggs.
High concentrations of ThC (approximately 10(5)-10(7)/g) were found in water spinach samples. ThC mean counts did not differ significantly, neither between sample types at each location, nor between locations. ThC mean concentration of water spinach samples collected in the rainy season of 2005 was higher than that in the dry season of 2004. Protozoan parasites were detected in the samples from all three locations and in water spinach harvested with and without wastewater contact. Giardia spp. were present in 56% (20) of samples with an average cyst concentration of 6.6/g. Mean counts of Giardia were not significantly associated with wastewater contact status of water spinach. Cryptosporidium oocysts were found in 17% (six) of samples with an average concentration of 0.5 oocyst per gram of water spinach. Cyclospora oocysts were detected in 8% (three) of samples. Four (11%) water spinach samples contained helminth eggs (average concentration: 0.1 egg per gram). Water samples contained approximately 10(4)-10(7) ThC per 100 ml and a mean of 27.4 helminth eggs per litre. There was a 2-3 log reduction of ThC between the water samples collected at the wastewater entry and exit point(s) of the lake.
Water spinach cultivated in the lake was highly contaminated with feces, as indicated by high ThC concentrations and the presence of protozoan parasites. A reduction in ThC numbers almost to WHO guideline levels for irrigation water occurred through natural biological and physical processes in the lake, as shown by differences in ThC counts at wastewater entry and exit points.
Full-text · Article · Jan 2008 · Tropical Medicine & International Health
[Show abstract][Hide abstract] ABSTRACT: To assess the prevalence of helminth infections and their associated risks in a community using both wastewater and human excreta in agriculture and aquaculture.
A cross-sectional study was conducted in a peri-urban area in Hanoi, Vietnam. Data on the demography, socioeconomics and sanitation were collected from a survey of 400 agricultural households. Parasitological examination for the eggs of Ascaris sp., Trichuris sp. and hookworm was performed on single stool specimens obtained from study household members' 15-70 years and 0-72 months of age.
Of 807 stool samples collected from 620 adults and 187 children, 39% were infected with helminths. The prevalence of infections with Ascaris sp., Trichuris sp. and hookworm was 21.6%, 9.8% and 21.8%, respectively. Univariate and multivariate analyses showed that being an adult, female gender, living in a household without a latrine, excreta composted for less than 1 month and use of fresh human excreta were significantly associated with co-infection with all three helminths. Being an adult was an independent determinant for infections with individual helminths. The absence of a latrine and use of stored urine for irrigation were associated with an increased risk of Ascaris infection. Risk factors for Trichuris infection were inadequately composted excreta and year-round wastewater contact; risk factors for hookworm infection were female gender, household without a latrine and use of fresh human excreta.
Wastewater exposure did not pose a major risk for helminth infection in this community. Instead, lack of sanitation facilities and use of fresh or inadequately composted human excreta in agriculture were important risk factors.
Full-text · Article · Jan 2008 · Tropical Medicine & International Health
[Show abstract][Hide abstract] ABSTRACT: To assess whether exposure to wastewater is a risk factor for dermatitis (eczema) among farmers engaged in peri-urban aquatic food production in Hanoi, Vietnam.
A cross-sectional study with two follow-ups was conducted from April to December 2005 in two peri-urban communes in Hanoi, one using wastewater and another using river, rain and well water for aquatic food production. In each commune, 100 households were randomly selected and adult household members engaged in farming field work were interviewed in three surveys. Farmers who reported skin problems at the time of interviews were examined and treated by a dermatologist. Data were analysed for one farmer per household.
The overall prevalence of dermatitis from 592 interviews was 6.3%. The commune which used wastewater had a much higher overall prevalence of dermatitis (10.4%) than the commune that did not (2.1%; P-value < 0.001). Multivariable logistic regression analyses showed that occupational wastewater contact was an important risk factor for dermatitis (odds ratio [OR] 3.0; 95% confidence interval [CI] 1.1-7.7). Duration of daily wastewater contact was not significantly associated with dermatitis. Aquaculture work in the wet season carried an increased risk of dermatitis in both communes (OR 2.8; 95% CI 1.02-7.6). The use of personal protective measures during field work and washing hands and feet after work did not reduce the risk for dermatitis. However, observations showed that these practices were applied in such a way that they were unlikely to provide effective protection against wastewater contact.
Contact with wastewater is an important risk factor for dermatitis among farmers engaged in wastewater-fed peri-urban aquatic food production. Additional studies should test preventive and mitigating measures such as improved personal protection and hygiene.
Full-text · Article · Dec 2007 · Tropical Medicine & International Health
[Show abstract][Hide abstract] ABSTRACT: To assess the risk of skin disease among farmers occupationally exposed to wastewater.
One-year follow-up study with monthly assessments of wastewater exposure and skin disease in Nam Dinh, northern Vietnam, in two adjacent communes with contrasting levels of wastewater use. In each commune, 200 households were randomly selected.
Of the 1103 individuals aged > or =15 years, 381 reported a skin problem at baseline or at any of the monthly visits, primarily dermatitis (eczema) and superficial fungal infections. Among the 874 subjects who were free from skin disease at baseline and who could be followed up > or =11 months, 183 developed a new skin disease (cumulative incidence 21%). Exposure to wastewater was a major risk factor for skin disease with a relative risk (RR) of 1.89 [95% confidence interval (CI) 1.39-2.57] in multivariable analysis. Other risk factors for skin disease were involvement in agriculture in general (RR = 2.59, 95% CI 1.11-6.02), flower cultivation (RR = 1.36, 95% CI 1.01-1.83), vegetable farming (RR = 1.47, 95% CI 1.04-2.08), and a history of eczema (RR = 1.47, 95% CI 1.05-2.05).
Exposure to wastewater is a major risk factor for skin disease. In future studies, an attempt should be made to link specific chemical or biological agents in the wastewater to specific skin diseases.
Full-text · Article · Dec 2007 · Tropical Medicine & International Health