Respiratory Bacterial Pathogens in the Nasopharynx and Lower Airways of Australian Indigenous Children with Bronchiectasis

Abstract

Objective To test the hypothesis that bacterial density, strain diversity, and concordance of pathogens between upper and lower airways are higher in children with bronchiectasis than in those with non-bronchiectatic conditions. Study design Nasopharyngeal (NP) swabs and bronchoalveolar lavage (BAL) fluid were cultured from 45 Indigenous children with bronchiectasis and 30 non-Indigenous children with non-bronchiectatic respiratory symptoms. Lower airway infection was defined as >104 colony-forming units of respiratory bacteria/mL of BAL fluid. Concordance was determined by phenotype or genotype. Results NP carriage of Streptococcus pneumoniae, nontypable Haemophilus influenzae (NTHi), and Moraxella catarrhalis, and lower airway infection by NTHi (47% vs 3%), were detected significantly more often in the children with bronchiectasis than in those without this condition. BAL specimens from the infected Indigenous children also showed greater strain diversity (71% vs 0%). Strain concordance in NP and BAL cultures was high in both infected subgroups. Conclusions The high density and diversity of respiratory bacteria, along with strain concordance between upper and lower airways, found in Indigenous children with bronchiectasis suggest a possible pathogenic role of recurrent aspiration of NP secretions.