1. Institute of Preventive Medicine, National Defense Medical Center, New Taipei City 23742, Taiwan, ROC
2. Department and Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei City 11490, Taiwan, ROC
3. Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei City 11490, Taiwan, ROC
4. School of Dentistry and Graduate Institute of Dental Science, National Defense Medical Center, Taipei City 11490, Taiwan, ROC
5. Department of Dentistry, Tri-Service General Hospital, Taipei City 11490, Taiwan, ROC