1. From the Department of Urology, Faculty of Medicine, Kyoto University, Kyoto, Department of Microbiology, Institute of Basic Medical Science, University of Tsukuba, Tsukuba, Research Laboratories, Animal Science Division, Dainippon Pharmaceutical Co. Ltd., Ikeda and Department of Medical Technology, School of Health Science, Okayama University, Okayama, Japan, and National Institute of Cholera and Enteric Diseases, Calcutta, India