Quantitative detection of periodontopathic bacteria in lower respiratory tract specimens by real-time PCR

The presence of common periodontopathic bacteria, the Fusobacterium nucleatum-periodonticum-simiae group, Prevotella intermedia, and Porphyromonas gingivalis was determined from respiratory tract specimens of bacterial pneumonia by real-time PCR using universal and species-specific TaqMan probe/primer sets. 42 patients with infectious pneumonia and 45 patients without infectious pneumonia were retrospectively enrolled in clinical studies. Periodontopathic bacterial DNA was found in 57.1% cases of infectious pneumonia and 31.1% cases of noninfectious pulmonary disease. However, the proportion of periodontopathic bacterial DNA did not differ between the two groups, and the presence or proportion of periodontopathic bacterial DNA was not related to any clinical index of pneumonia. Only two pneumonia cases consisted of >30% Fusobacterium DNA, suggesting that Fusobacterium was the causal pathogen in these cases. Our findings suggest that the periodontopathic bacteria rarely proliferate and be etiological pathogen in lower airway tract. However, further study is necessary, focusing on the pathogenicity of F. nucleatum in pulmonary infectious disease.