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.

The target of the CD8+ T cell-dependent immunity that protects mice immunized with irradiation-attenuated malaria sporozoites has not been established. Immune BALB/c mice were shown to develop malaria-specific, CD8+ T cell-dependent inflammatory infiltrates in their livers after challenge with Plasmodium berghei sporozoites. Spleen cells from immune BALB/c and C57BL/6 mice eliminated hepatocytes infected with the liver stage of P. berghei in vitro. The activity against infected hepatocytes is not inhibited by antibodies to interferon-gamma and is not present in culture supernatants. It is genetically restricted, an indication that malaria antigens on the hepatocyte surface are recognized by immune T effector cells. Subunit vaccine development will require identification of the antigens recognized by these T cells and a method of immunization that induces such immunity.

Abstract. Campylobacter is a leading cause of traveler's diarrhea in Thailand. Since resistance to quinolones is high among Campylobacter isolates, empiric therapy with quinolones for traveler's diarrhea may be ineffective in this region. We conducted an observational study among 169 U.S. military personnel with acute diarrhea and compared their microbiologic findings to those of 77 asymptomatic personnel deployed to Thailand in May 1998. Of 146 pathogenic bacterial isolates, the most common were nontyphoidal Salmonella (n ‫ס‬ 31), enterotoxigenic Escherichia coli (n ‫ס‬ 24), and C. jejuni/coli (n ‫ס‬ 23). Campylobacter was strongly associated with disease (odds ratio ‫ס‬ 5.9; 95% confidence interval ‫ס‬ 1.3−37.3), with a more severe clinical presentation, and with a reduced functional ability at presentation (P ‫ס‬ 0.02). In vitro resistance to ciprofloxacin was observed in 96% of the Campylobacter isolates. Sub-optimal treatment response to ciprofloxacin was observed in 17% of the cases of Campylobacter infection versus 6% due to other causes. These results highlight the importance of Campylobacter as a cause of severe traveler's diarrhea in Thailand and illustrates the ongoing problem with antibiotic-resistant strains and associated treatment problems.

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.

To make a comprehensive study of tetracycline resistance determinant distribution in the genus Shigella, a collection of 577 clinical isolates of Shigella spp. and enteroinvasive Escherichia coli (EIEC) from a variety of geographical locations was screened to identify tetracycline-resistant strains. The 459 tetracycline-resistant isolates identified were then screened by PCR analysis to determine the distribution in these strains of tetracycline efflux resistance determinants belonging to classes A to E, G, and H that have been identified in gram-negative bacteria. Only classes A to D were represented in these strains. Although Tet B was the predominant determinant in all geographical locations, there were geographical and species differences in the distribution of resistance determinants. An allele of tet(A), designated tet(A)-1, was identified and sequenced, and the 8.6-kb plasmid containing determinant Tet A-1, designated pSSTA-1, was found to have homologies to portions of a Salmonella enterica cryptic plasmid and the broad-host-range resistance plasmid RSF1010. This allele and pSSTA-1 were used as epidemiological markers to monitor clonal and horizontal transmission of determinant Tet A-1. An analysis of serotype, distribution of tetracycline resistance determinants, and resistance profiles indicated that both clonal spread and horizontal transfer had contributed to the spread of specific tetracycline resistance determinants in these populations and demonstrated the use of these parameters as an epidemiological tool to follow the transmission of determinants and strains.

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Abstract. To evaluate the hypothesis that gastric infection with Helicobacter pylori increases risk for diarrheal disease in children, we conducted a yearlong prospective study among 160 orphanage children Ͻ 5 years of age in Nonthaburi, Thailand. Serum samples collected at six-month intervals were examined by ELISA for antibodies to H. pylori, and children were followed daily for the development of diarrhea. Seven percent of children were seropositive on enrollment, 59% were seronegative, and 34% were indeterminate. Among the seronegative children, seroconversion occurred at a rate of 7% per six months. Forty-six percent of children developed 214 total episodes of diarrhea. By age group, children Ͻ 18 months, 18-24 months and Ͼ 24 months of age experienced 2.6, 1.1, and 0.2 mean diarrhea episodes per six months. The incidence of diarrhea was not significantly different between children by H. pylori serostatus. We conclude that H. pylori infection was not associated with an increased risk of diarrheal disease.In 1983, Warren and Marshall identified Helicobacter pylori in gastric biopsies from patients in Australia.1 This organism has subsequently been shown to play an important role in gastritis and peptic ulcer disease in industrialized and developing countries worldwide. 2,3 Acute infection is associated with hypochlorhydria, which persists for several months after exposure. [3][4][5] In addition, there is strong evidence that chronic H. pylori infection is associated with atrophic gastritis and gastric carcinoma. 3,6 Antibodies to H. pylori are more prevalent and are acquired at a younger age among people in developing countries than among people living in industrialized countries. 7,8 In a recent study in rural and urban communities in Thailand, Ͼ50% of children had serologic evidence of infection by eight years of age. 7 At an orphanage in Bangkok, Thailand, where enteric infections were hyperendemic, 74% of the children between one and four years of age were seropositive for H. pylori. 9 The high prevalence of H. pylori among children in developing countries and the association with hypochlorhydria have suggested that this infection may predispose to acute or persistent diarrheal disease. 10 In a retrospective study from the Gambia, infants with chronic diarrhea and malnutrition were significantly more likely to have serologic evidence of H. pylori infection compared to agematched healthy controls and malnourished children without diarrhea.11 Additionally, in a retrospective study from Bangladesh, the odds of H. pylori seropositivity among subjects with severe cholera were significantly higher than in agematched controls. 12 Prospective studies correlating the incidence of diarrhea with H. pylori infection have not been published. To determine if H. pylori infection increases the risk of diarrheal disease, we conducted a prospective study of the correlation between this infection and diarrheal disease in an orphanage in Nonthaburi, Thailand. MATERIALS AND METHODSThis study was conducted in the Pakkred Babi...