Components/Secretions Synergistically Enhance Pneumonia Caused by in Mice.

is an important causative organism of respiratory tract infections. Although periodontal bacteria have been shown to influence respiratory infections such as aspiration pneumonia, the synergistic effect of and , a periodontopathic bacterium, on pneumococcal infections is unclear. To investigate whether accelerates pneumococcal infections, we tested the effects of inoculating culture supernatant (PgSup) into -infected mice. Mice were intratracheally injected with and PgSup to induce pneumonia, and lung histopathological sections and the absolute number and frequency of neutrophils and macrophages in the lung were analyzed. Proinflammatory cytokine/chemokine expression was examined by qPCR and ELISA. Inflammatory cell infiltration was observed in -infected mice and and PgSup mixed-infected mice, and mixed-infected mice showed more pronounced inflammation in lung. The ratios of monocytes/macrophages and neutrophils were not significantly different between the lungs of -infected mice and those of mixed-infected mice. PgSup synergistically increased TNF-α expression/production and IL-17 production compared with infection alone. We demonstrated that PgSup enhanced inflammation in pneumonia caused by , suggesting that virulence factors produced by are involved in the exacerbation of respiratory tract infections such as aspiration pneumonia.