This case-control study detected and characterized Shigella and diarrheagenic Escherichia coli (DEC) types among Vietnamese children less than 5 years old. In 249 children with diarrhea and 124 controls, Shigella spp. was an important cause of diarrhea (P < 0.05). We used multiplex PCR and DNA probes to detect enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAggEC), enteropathogenic E. coli (EPEC), attaching and effacing E. coli (A/EEC), verocytotoxin-producing E. coli (VTEC), and enterotoxigenic E. coli (ETEC). The prevalences of DEC in the diarrhea and control groups were 25.7 and 10.5%, respectively. In 62 children with diarrhea, 64 DEC strains included 22 EAggEC (8.8%), 2 EIEC (0.8%), 23 A/EEC (9.2%), 7 EPEC (2.8%), and 10 ETEC strains (4.0%). Among controls, 13 DEC strains included 5 EAggEC strains (4.0%), 7 A/EEC strains (5.6%), and 1 EPEC strain. The characterization of DEC by serotypes, antimicrobial susceptibility patterns, virulence genes, and pulsed-field gel electrophoresis showed the occurrence of many different and highly heterogenic DEC subtypes, but common serotypes were found among ETEC, EIEC and EPEC, respectively. Serotyping was used to distinguish between A/EEC and EPEC. However, A/EEC, EPEC, and EAggEC were isolated at high frequency from both cases and controls. Further in-depth studies are needed to better understand important virulence factors of DEC, especially A/EEC, EPEC, and EAggEC.

We prospectively studied diarrhoea incidence among 1655 children < 5 years of age in northern Vietnam for 1 year using primarily passive surveillance. Standard culture methods were used to detect bacterial pathogens. Overall 2160 cases occurred (1·3 cases/child per year). Peak rates of diarrhoea occurred in children < 12 months old. Rates ranged from 3·3 cases/child per year in children < 1 year old, to 0·7 cases/child per year in 4-year-olds. Campylobacter, shigella and enterotoxigenic Escherichia coli were most commonly isolated. Rates detected by active surveillance were about twice those detected passively. S. flexneri was the most common shigella serogroup (65%). S. flexneri serotypes 6, 4, 1 and Y were most common, but 40% were untypable using commercial antisera. The data illustrate important regional differences in pathogen prevalence and shigella serotype distribution. Shigella vaccine development strategies, commonly targeting S. flexneri 2a, S. sonnei and S. dysenteriae 1, will have little impact on diarrhoea rates in Vietnam.

A case-control study was conducted to identify the aetiology of diarrhoeal diseases in pre-school children in a suburban area of Hanoi where the use of untreated wastewater in agriculture and aquaculture is a common practice. Stool specimens and clinical information were collected from 111 pairs of children with diarrhoea and healthy controls. A total of 73 cases (66 %) and 41 controls (36 %) had an enteric pathogen. The pathogens most often associated with diarrhoea were rotavirus (17 % of cases) and Entamoeba histolytica (15 %), followed by Shigella (5 %). Diarrhoeagenic Escherichia coli (DEC) was found in 23 % of both patients and controls. Characterization of DEC by serotyping, antimicrobial susceptibility test and PFGE showed that DEC represented by different pathotypes belonged to various serotypes. Except for three enterotoxigenic E. coli strains, typing by PFGE revealed no correlation between pathotype and serotype of DEC strains. This suggests a high prevalence of a variety of DEC subtypes in this area. For this particular region, vaccine development strategies targeting rotavirus and Shigella are likely to be of public health benefit, whereas the role of DEC and preventive measures need to be further elaborated. INTRODUCTIONDiarrhoeal disease is a major problem throughout the world, and is responsible for high morbidity and mortality among children, especially in developing countries. Some aetiological studies of diarrhoeal diseases have been carried out in Vietnam (Isenbarger et al., 2001;Nguyen et al., 2005a), but not in areas where untreated wastewater is used in agriculture and aquaculture. The association of wastewater use and risks to human health has been assessed in various countries such as Israel, Morocco, Mexico and Pakistan, where wastewater is also commonly used for irrigation (Shuval et al., 1989;Feenstra et al., 2000;Habbari et al., 2000; Blumenthal et al., 2001; WHO, 2006). Some studies have highlighted a high risk of being infected with intestinal parasites and of getting diarrhoeal diseases, especially in small children who live in the wastewaterusing areas (Cifuentes, 1998;Cifuentes et al., 2000).In a hospital study, the prevalences of diarrhoeagenic Escherichia coli (DEC) were 22.5 and 12 % in the diarrhoea and control groups, respectively, but mainly due to a high frequency of enteroaggregative E. coli (EAggEC) (Nguyen et al., 2005a). Using dot-blot hybridization in another hospital-based study, eae-positive E. coli were found at a significantly higher prevalence in children with diarrhoea than in asymptomatic controls (Bodhidatta et al., 2007). In a study outside Hanoi, Campylobacter and Shigella were found to be associated with diarrhoea, and enterotoxigenic E. coli (ETEC) was the prevalent group of DEC (Isenbarger et al., 2001). None of these studies included detailed characterization of DEC.The aim of the present study was to determine the aetiology of diarrhoeal diseases in children from families engaged in Abbreviations: A/EEC, attaching and effacing Escherichia coli; DEC, di...

Summaryobjectives To determine the occurrence of and risk factors for diarrhoea in an adult population exposed to wastewater used for agricultural and aquacultural productions.methods 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.results 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%).conclusion 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.

Serum specimens (n = 1899) were assayed for infections with HTLV-I, HTLV-II, and HIV-1 in seven classified groups of normal healthy controls, children, pregnant women, prostitutes, intravenous drug abusers, patients under going hemodialysis, and hemophiliacs in South and North Vietnam. Surprisingly, 125 of 954 samples from South Vietnam exhibited seropositivity for HTLV-II and 119 of these belonged to the group of IVDAs (n = 200). The remaining six positives were a healthy control, a prostitute, two children, and two patients under going hemodialysis. Two IVDAs who were seropositive for HTLV-I and 10 of 15 seropositives for HIV-1 were also positive for HTLV-II in this population. In contrast, no seropositives to any of the viruses were detected in the North Vietnamese samples (0 of 945). The HTLV-II-seropositive IVDAs exhibited increased seropositivity with age compared with HIV-1 seropositivity in the population, and there was no statistical relation between seropositivity for HTLV-II and HIV-1. The HTLV-IIs in South Vietnam IVDAs appeared, by subtype-specific peptide ELISA, to be a mixture of both subtypes a and b, with subtype a predominant. It seems possible that HTLV-II may have been introduced into this population from IVDAs from the United States during the Vietnam conflict, but in a period prior to, or early in, the introduction of HIV-1 to IVDAs.

Blood donors in two cities in Vietnam were tested for markers of hepatitis C virus (HCV) and hepatitis B virus infections. Antibody to HCV was detected by passive hemagglutination with antigens of the second generation in 101 (20.6%) of 491 donors in Ho Chi Minh City; it was detected less frequently (P < 0.001) in donors in hanoi (4 [0.8%] of 499). HCV RNA was tested for in donors with antibody by PCR with nested primers from the 5'-noncoding region and detected in 79 donors in Ho Chi Minh City and 4 donors in Hanoi. HCV RNA was genotyped by PCR with type-specific primers from the core gene. Of 83 HCV carriers from Vietnam, 24 (29%) were infected with HCV of genotype I/1a 19 (23%) were infected with II/1b, 4 (5%) were infected with III/2a, and 2 (2%) were infected with mixed genotypes (I/1a and II/1b); HCV genotypes in the remaining 34 (41%) donors, including all 4 donors in Hanoi, were not classifiable into I/1a, II/2a, IV/2b, or V/3a. Of the 10 isolates with unclassifiable genotypes, 2 showed substantial sequence divergence within the 5'-noncoding region from reported isolates with known genotypes (I/1a to 6a). An analysis of part of the core gene sequence indicated that six of the remaining isolates most likely represented new HCV genotypes. Hepatitis B surface antigen and the corresponding antibody, respectively, were detected in 15 (3.1%) and 234 (47.7%) donors in Ho Chi Minh City as well as 15 (3.0%) and 248 (49.7%) donors in Hanoi. These results indicate an extensive spread of HCV among Ho Chi Minh City donors and HCV of novel genotypes in vietnam.

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In the production of astaxanthin from Haematococcus pluvialis, the process of growing algal biomass in the vegetative green stage is an indispensable step in both suspended and immobilized cultivations. The green algal biomass is usually cultured in a suspension under a low light intensity. However, for astaxanthin accumulation, the microalgae need to be centrifuged and transferred to a new medium or culture system, a significant difficulty when upscaling astaxanthin production. In this research, a small-scale angled twin-layer porous substrate photobioreactor (TL-PSBR) was used to cultivate green stage biomass of H. pluvialis. Under low light intensities of 20–80 µmol photons m−2·s−1, algae in the biofilm consisted exclusively of non-motile vegetative cells (green palmella cells) after ten days of culturing. The optimal initial biomass density was 6.5 g·m−2, and the dry biomass productivity at a light intensity of 80 µmol photons m−2·s−1 was 6.5 g·m−2·d−1. The green stage biomass of H. pluvialis created in this small-scale angled TL-PSBR can be easily harvested and directly used as the source of material for the inoculation of a pilot-scale TL-PSBR for the production of astaxanthin.