Emergence of nalidixic acid resistant Shigella dysenteriae type 1 in Thailand: an outbreak associated with consumption of a coconut milk dessert.

BACKGROUND: Although Shigella dysenteriae type 1 has been responsible for large outbreaks of severe dysentery in many parts of Asia, relatively few cases of this disease have been reported from Thailand and have generally not involved nalidixic acid resistant strains. METHODS: Beginning March 1991, all patients with diarrhoea seen at the hospital outpatient department (OPD) in Suan Phung, Thailand (a western district near the Burmese border) were cultured for enteric pathogens. Shigella dysenteriae 1 was first recognized in July 1992, and an OPD-based case-control study was conducted to pinpoint the source of the outbreak in the community. For each case of culture confirmed S. dysenteriae 1, one control person without diarrhoea, matched by age and date of visit, was randomly selected from the OPD registry. RESULTS: Of 197 patients treated for diarrhoea at the hospital OPD in July and August 1992, 79 (40%) had bloody diarrhoea, compared with 86/561 (15%) patients seen during 16 months of previous surveillance (P < 0.0001). Shigella dysenteriae 1 was isolated from 33/197 (17%) patients. Compared to matched controls, patients with S. dysenteriae 1 were more likely to attend one of the local elementary schools (odds ratio = 6.74, P = 0.025), or live in the community surrounding this school (odds ratio for non-school age people = 18.0, P = 0.008). A cross-sectional study conducted at the school indicated that 50 (10%) of 485 students had dysentery in July. A coconut milk dessert prepared at the school was identified as the vehicle of transmission (relative risk = 24.9, P < 0.0001). CONCLUSIONS: Nalidixic acid resistant S. dysenteriae 1 emerged in a community in Thailand, and was traced to a point source outbreak at a local school.

PIP: Shigella dysenteriae type 1 has been responsible for large outbreaks of severe dysentery in many parts of Asia, but relatively few cases of the disease have been reported from Thailand and have generally not involved nalidixic acid resistant strains. Nalidixic acid resistant Shigella dysenteriae type 1, however, emerged in a community in Thailand and was traced to a point source outbreak at a local school. Beginning March 1991, as part of prospective surveillance for diarrheal disease in Suan Phung, all patients with diarrhea seen at the hospital outpatient department (OPD) in Suan Phung, Thailand, were cultured for enteric pathogens. 79 of the 197 patients treated for diarrhea at the hospital OPD in July and August 1992 had bloody diarrhea compared with 86/561 patients seen during 16 months of previous surveillance. Shigella dysenteriae type 1 was isolated from 33 of these 197 patients. Compared to matched controls, patients with Shigella dysenteriae type 1 were more likely to attend one of the local elementary schools or live in the community surrounding that school. A cross-sectional study conducted at the school found that 50 of 485 students had dysentery in July. A coconut milk dessert prepared at the school was identified as the vehicle of transmission.

Etiology of diarrhea in a rural community in western Thailand: importance of enteric viruses and enterovirulent Escherichia coli.

The etiology of gastroenteritis was determined in children and adults with diarrhea seen at a district hospital and three government health clinics in Suan Phung, western Thailand, in 1991. Enteric viruses (rotavirus and astrovirus) were identified in 40%, shigellae in 18%, attaching and effacing Escherichia coli in 13%, Campylobacter jejuni in 9%, and enterotoxigenic E. coli in 7% of children < 5 years old with diarrhea seen at the hospital. Enteric viruses were detected in 15% (24/156) of patients with diarrhea > or = 5 years old and were the only enteric pathogens identified in 12 patients ages 7-79 years (2 astrovirus, 10 rotavirus infections). Attaching and effacing E. coli, rotavirus, and astrovirus were potential causes of diarrhea in children and adults in this population.

Diagnosis of Helicobacter pylori infection in a developing country: comparison of two ELISAs and a seroprevalence study.

Serology to detect antibodies to Helicobacter pylori is not frequently used as a diagnostic tool in developing countries. When compared to a commercial ELISA, an ELISA constructed and validated in Thailand had a higher sensitivity (98% vs. 85%), specificity (76% vs. 66%), and negative predictive value (97% vs. 76%) for the detection of H. pylori infection among 104 patients with dyspepsia evaluated by endoscopy. The positive predictive value was 88% for both tests. Serum antibody levels fell significantly 5-8 months after eradication of infection in 8 Thai patients (P = .009). By 8 years of age, > 50% of Thai persons living in urban and rural locations were seropositive. The low negative predictive value of the commercial ELISA limits the usefulness of this assay as a diagnostic tool in Thailand and suggests a need to reevaluate H. pylori serologic tests when used in populations living in developing countries.