BACKGROUND: Based on surface brushings and BAL fluid Hilty, et al. demonstrated microbiomes in the human lung characteristic of asthma and chronic obstructive pulmonary disease (COPD), which have now been confirmed by others. The present study extends these findings to human lung tissue samples.
METHODS: DNA from lung tissue samples were obtained from non-smokers (n=8), smokers without COPD (n=8), very severe COPD (GOLD 4) patients (n=8), and patients with cystic fibrosis (n=8). The latter served as a positive control, with sterile water as a negative control. All bacterial community analyses were based on PCR amplified 16S rRNA gene fragments. Total bacterial populations were measured by quantitative PCR (QPCR) and bacterial community composition was assessed by terminal restriction fragment length polymorphism (TRFLP) analysis and pyrotag sequencing.
RESULTS: Total bacterial populations within lung tissue were small (20-1252 bacterial cells/1000 human cells) but greater in all four sample groups versus the negative control (P<0.001). TRFLP analysis and sequencing distinguished three distinct bacterial community compositions: one common to the non-smoker and smoker groups, a second to the GOLD 4 group, and the third to the cystic fibrosis positive control group. Pyrotag sequencing identified greater than 1400 unique bacterial sequences and showed an increase in the firmicute phylum in GOLD 4 patients versus all other groups (P<0.003) attributable to an increase in the Lactobacillus genus (P<0.0007).
CONCLUSION: There is a detectable bacterial community within human lung tissue that changes in patients with very severe COPD.
Authors: Sze MA, Dimitriu PA, Hayashi S, Elliott WM, McDonough JE, Gosselink JV, Cooper J, Sin DD, Mohn WW, Hogg JC
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