[ODP25] 5. Pathogenicity -e. Infection models

[ODP-159] Mechanism of exacerbation of pneumonia by oral commensals in HOMA mouse model

Manami Hayashi^1,2, Momoe Itsumi¹, Mina Mori¹, Haruka Fukamachi¹, Hirotaka Kuwata¹ (¹Dept. Oral. Microbiol. Immunol., Sch. Dent., Showa Univ., ²Div. Anesth., Sch. Dent. Showa Univ.)

Aspiration pneumonia occurs when bacteria increase in the oral cavity and enter the respiratory tract due to impaired swallowing function in the immunocompromised host. Although the involvement of pathogenic bacteria such as S. pneumoniae as causative agents of pneumonia has already been clarified, the involvement of non-pathogenic bacteria is not clear. To investigate the mechanism of pneumonia induction by oral non-pathogenic bacteria, we used human oral microbiota associated (HOMA) mice and investigated the relationship between oral commensals and the pathogenesis of aspiration pneumonia. HOMA mice were generated using oral bacterial of two healthy individuals in germ-free mice and LPS was administered intraperitoneally. Bacteria in the lung was cultured on BHI agar and infection was confirmed in the lung of septic HOMA mice, while no bacteria were detected in the normal HOMA mice. Comprehensive analysis of the bacterial genome in the lung using a next-generation sequencer showed that the composition of bacterial species was not uniform. Lung immune profiles were examined by ‍flow cytometry, and we found alveolar macrophages (CD11b^midGr-1^high) disappeared and tissue macrophages (CD11b^highGr-1^mid) increased, which was thought to be associated with exacerbation of lung infection. These indicate that pneumonia can be caused by oral commensals in immunocompromised conditions.