Shigella species and serotypes among clinical isolates in Thailand from 2001 to 2005.

Objective: To study the species and the serotypes of the clinical isolates of Shigella obtained from patients in Thailand.

Material And Method: The World Health Organization National Salmonella and Shigella Center Thailand, had confirmed the species and performed serotype identification of 1,913 clinical isolates of Shigella collected from the laboratory network of Department of Medical Sciences and the collaborated hospitals across Thailand from 2001 to 2005.

Results: Between the year 2001 and 2005, 728, 481, 160, 247, 297 clinical isolates were tested, respectively. There were 5 isolates of S. dysenteriae (group A), 416 isolates of S. flexneri (group B), 4 isolates of S. boydii (group C) and 1,488 isolates of S. sonnei (group D). A total of 21 Shigella serotypes were identified and there were 3 serotypes in group A, 11 serotypes in group B, 4 serotypes in group C, and 3 serotypes in group D. Throughout these five years, the five common serotypes were S. sonnei Phases I and II, 28.6% (548 isolates); S. sonnei Phase I, 24.6% (470 isolates); S. sonnei Phase II, 24.6% (470 isolates); S. flexneri Type 2a, 10.9% (208 isolates), and S. flexneri Type 3a, 6.3% (121 isolates), respectively.

Conclusion: At the national scale in Thailand from 2001 to 2005, S. sonnei was the most frequent Shigella spp. isolated from patients in Thailand. In addition, S. dysenteriae and S. boydii were extremely uncommon. These findings are important in future vaccine development.