Molecular analysis of the lower respiratory tract microbiota
It was proposed that the lower airways of patients with asthmas and Chronic Obstructive Pulmonary Disease (COPD) might possess uncharacterised bacterial components absent from the healthy respiratory tract.;Total genomic DNA was extracted from induced sputum and broncho-alveolar lavage samples from healthy volunteers, mild asthmatics and COPD patients. Following this, clones containing bacterial 16S rDNA amplicons were produced using broad-range bacterial primers and the Polymerase Chain Reaction (PCR). These were grouped using restriction analysis and characterised by selective sequencing. The bacterial composition of each sample was then determined and the distribution of individual groups and overall sample group diversities derived and compared across the volunteer groups. Such analyses have not previously been applied to samples from humans.;Bacterial populations of surprising complexity were present, not only in respiratory disease, but also in respiratory health. This raises questions about the natural sterility of the lower respiratory tract and whether there is a genuine resident microbiota. While no single predominant organism showed a strong association, several organisms represented by low clone frequencies were differentially associated with health or disease. Moreover, the Bacterial diversity present in samples from healthy volunteers was significantly greater than that detected in samples from patients. Molecular characterisation of the bacteria present in lower airways revealed novel and potentially important aspects of the human-associated microbiota.