1. Enteric Laboratory, National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Tiwanonth Road, Amphur Muang Nonthaburi, 11000, Thailand 2Department of Human Nutrition, Faculty of Contemporary Sciences, Chugoku-Gakuen University, 83 Niwase, Okayama, 701-0197, Japan 3Department of Infection Biology, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, 305-8575, Japan