1. Laboratory of Enteric Microbiology, Laboratory Sciences Division; International Center for Diarrhoeal Disease Research; Bangladesh (ICDDR, B), Mohakhali Dhaka 1212 Bangladesh
2. Department of Microbiology; University of Dhaka; Dhaka 1000 Bangladesh
3. National Institute of Cholera and Enteric Diseases (NICED); Calcutta India
4. Department of Bacteriology; National Institute of Infectious Diseases; Shinjuku-ku Tokyo 162-8640 Japan
5. Faculty of Pharmaceutical Sciences; Okayama University; Okayama Okayama 700-8530 Japan