1. Department of Health and Medical SciencesShinshu University Graduate School of Medicine3‐1‐1 AsahiMatsumotoNagano 390‐8621Japan
2. Department of BacteriologyNagoya University Graduate School of Medicine65 Tsurumai‐cho, Showa‐kuNagoyaAichi 466‐8550Japan
3. Department of Medical SciencesShinshu University Graduate School of MedicineScience and Technology3‐1‐1 AsahiMatsumotoNagano 390‐8621Japan