Detecting and Comparing Bacteria in the Lower Airways of Children with Persistent Bacterial Bronchitis and a Healthy Population

Lower airway sampling in paediatrics is challenging and often invasive. The role of infection in persistent bacterial bronchitis (PBB) is well established but there has been no microbiological comparison with PBB and a completely normal host. Bioaerosol sampling systems can non-invasively access the lungs. A proof of concept study was carried out in 20 healthy adults who breathed for two minutes and then coughed ten times into an exhalation filter device. 15 grew Staphylococcus, five Streptococcus and five had no growth. This may represent upper airway contamination. Bronchoalveolar lavage from 13 children with PBB and five controls were compared in the EPISTREP study. Significant recruitment problems were encountered. 12 with PBB had a positive bacterial culture compared to two healthy controls growing bacteria expected in PBB, namely Haemophilus influenzae, Haemophilus parainfluenzae, Streptrococcus pneumoniae and Moraxella catarrhalis. Bronchial brushings, an easier and quicker alternative to bronchoalveolar lavage, were compared in PBB and controls. Blind bronchial brushings were taken from 24 with PBB and 18 controls, with an additional non-blind brushing taken in PBB. DNA extraction, quantitative PCR and 16S rRNA gene sequencing were done. Bacterial diversity was reduced in PBB compared to controls (p<0.001). Haemophilus was the most commonly cultured organism in PBB (n=17) yet it was only dominant by sequencing in nine children. No one cultured Neisseria but it was dominant by sequencing in five patients. There was no difference in microbiome detection using blind and non-blind brushings. Bacteria considered significant in PBB can be cultured from the lower airways of healthy children. In PBB there is a significant reduction in microbiome diversity, similar to other lung diseases such as cystic fibrosis. The equivalence of blind and non-blind brushings enables simpler lower airway sampling although using the exhalation filter as a non-invasive sampling method requires further development.