1. Division of Otorhinolaryngology, Kawagoe Ear Institute, Kawagoe, Japan
2. Department of Microbiology, Fukushima Medical University School of Medicine, Fukushima, Japan
3. Department of Otorhinolaryngology, Head and Neck Surgery, School of Medicine, Keio University, Tokyo, Japan
4. National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan