Laboratory diagnosis of typhoid fever requires isolation and identification of Salmonella enterica serotype Typhi. In many areas where this disease is endemic, laboratory capability is limited. Recent advances in molecular immunology have led to the identification of sensitive and specific markers for typhoid fever and technology to manufacture practical and inexpensive kits for their rapid detection. We evaluated three commercial kits for serologic diagnosis of typhoid fever. Patients presenting with > 4 days of fever were enrolled at two hospitals in Southern Vietnam. Cases were patients with serotype Typhi isolated from blood samples, and controls were patients with other laboratory-confirmed illnesses. Serotype Typhi isolates were confirmed and tested for antimicrobial susceptibility at the Pasteur Institute in Ho Chi Minh City. The Widal test was run at the hospitals and the Pasteur Institute. Sera were shipped frozen to the Centers for Disease Control and Prevention and tested by using Multi-Test Dip-S-Ticks, TyphiDot, and TUBEX to detect immunoglobulin G (IgG), IgG and IgM, and IgM, respectively. Package insert protocol instructions were followed. We enrolled 59 patients and 21 controls. The sensitivity and specificity findings were as follows: 89 and 53% for Multi-Test Dip-S-Ticks, 79 and 89% for TyphiDot, 78 and 89% for TUBEX, and 64 and 76% for Widal testing in hospitals and 61% and 100% for Widal testing at the Pasteur Institute. For all assays, the sensitivity was highest in the second week of illness. The Widal test was insensitive and displayed interoperator variability. Two rapid kits, TyphiDot and TUBEX, demonstrated promising results.

Antimicrobial resistance rates for shigella, campylobacter, nontyphoidal salmonella, and enterotoxigenic Escherichia coli were compared for Vietnam and Thailand from 1996 to 1999. Resistance to trimethoprim-sulfamethoxazole, ampicillin, chloramphenicol, and tetracycline was common. Quinolone resistance remains low in both countries, except among campylobacter and salmonella organisms in Thailand. Nalidixic acid resistance among salmonellae has more than doubled since 1995 (to 21%) in Thailand but is not yet documented in Vietnam. Resistance to quinolones correlated with resistance to azithromycin in both campylobacter and salmonella in Thailand. This report describes the first identification of this correlation and its epidemiologic importance among clinical isolates. These data illustrate the growing magnitude of antibiotic resistance and important differences between countries in Southeast Asia.

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Microsporidiosis cases due to Enterocytozoon bieneusi and Encephalitozoon intestinalis are emerging opportunistic infections associated with a wide range of clinical syndromes in humans. The aim of this study was to specify microsporidial epidemiology in two different geographical areas. From November 2004 to August 2005, 228 and 42 stool samples were collected in Niamey, Niger, and Hanoi, Vietnam, respectively. Screening for microsporidia was performed using UV-light microscopy. Detection was confirmed by molecular biology using two methods specific for E. bieneusi and E. intestinalis. All samples positive for E. bieneusi were subjected to genotyping. In this study, we found high prevalences of microsporidiosis among human immunodeficiency virus-infected patients, 10.5% and 9.5%, respectively, in Niamey and Hanoi. These levels of prevalence are similar to those recorded in European countries before highly active antiretroviral therapy was introduced. In the samples positive for E. bieneusi, we found seven distinct genotypes, including two genotypes not previously described. The E. bieneusi genotype distributions in the two geographical areas suggest different routes of infection transmission, person-to-person in Niger and zoonotic in Vietnam.

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.

BackgroundEntamoeba histolytica is an important protozoan intestinal infection in resource-poor settings, including Vietnam. The study objective was to assess risk factors of E. histolytica infection in a community in Vietnam, where wastewater and human excreta are used in agriculture. A case-control study was conducted among residents of Hanam province, Northern Vietnam. Cases (n = 46) infected with E. histolytica and non-infected controls (n = 138) were identified in a cross-sectional survey among 794 randomly selected individuals and matched for age, sex and place of residence. Potential risk factors including exposure to human and animal excreta and household wastewater were assessed with a questionnaire.ResultsPeople from households with an average socio-economic status had a much higher risk of E. histolytica infection (odds ratio [OR]=4.3, 95% confidence interval [CI]: 1.3-14.0) compared with those from households with a good socioeconomic status. Those individuals who never or rarely used soap for hand washing had a 3.4 times higher risk for infection (OR=3.4, 95% CI: 1.1-10.0), compared to those who used always soap. In contrast, none of the factors related to use of human or animal excreta was statistically significant associated with E. histolytica infection. People having close contact with domestic animals presented a greater risk of E. histolytica infection (OR = 5.9, 95% CI: 1.8-19.0) than those without animal contact. E. histolytica infection was not associated with direct contact with Nhue river water, pond water and household's sanitary conditions, type of latrine or water source used.ConclusionsOur study suggests that in settings where human and animal excreta and Nhue River water are intensively used in agriculture, socio-economic and personal hygiene factors determine infection with E. histolytica, rather than exposure to human and animal excreta in agricultural activities.

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.

The number of cholera cases and the mortality rates reported from different regions of Vietnam varied considerably in the period from 1979 to 1996, with between 2,500 and 6,000 cases reported annually from 1992 to 1995. Annual mortality rates ranged from 2.0 to 9.6% from 1979 to 1983 to less than 1.8% after 1983. Major cholera outbreaks were reported from the High Plateau region for the first time in 1994 and 1995; this is an area with limited access to health services and safe drinking-water supplies. All cases were associated with Vibrio cholerae O1. Using ribotyping, cholera toxin (CT) genotyping, and characterization of antibiotic susceptibility patterns and antibiotic resistance genes by PCR, we show that strains isolated after 1990 were clearly different from strains isolated before 1991. In contrast to strains isolated before 1991, 94% of 104 strains isolated after 1990 showed an identical ribotype R1, were resistant to sulfamethoxazole and streptomycin, and showed a different CT genotype. Furthermore, PCR analysis revealed that sulfamethoxazole-resistant strains harbored class I integrons containing a gene cassette ant(3")-1aencoding resistance to streptomycin and spectinomycin. This is, to our knowledge, the first report of class I integrons in V. cholerae. The development of cholera and the changes in the phenotypic and genotypic properties of V. cholerae O1 shown in the present study highlight the importance of monitoring V. cholerae O1 in Vietnam as in other parts of the world. In particular, the emergence of the new ribotype R1 strain containing class I integrons should be further studied.