Respiratory bacterial pathogens in the nasopharynx and lower airways of Australian indigenous children with bronchiectasis

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 >10(4) 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.