Introduction: Bronchopulmonary dysplasia (BPD) is a major complication of prematurity, marked by heterogeneous pulmonary phenotypes and variable clinical outcomes. The airway microbiome may influence disease severity and progression, yet quantitative associations between airway pathogens and clinically relevant outcomes remain poorly understood.
Methods: We conducted a retrospective analysis of 204 neonates who underwent flexible bronchoscopy with quantitative bronchoalveolar lavage (BAL) cultures in the NICU at the Children's Hospital of Philadelphia. Cultures yielding ≥ 10,000 colony-forming units per milliliter for a single bacterial species were classified as positive. Respiratory severity score (RSS), calculated as the product of mean airway pressure and fraction of inspired oxygen, served as the primary indicator of respiratory status. Linear, logistic, and negative binomial regression models were used to assess associations between bacterial species and clinical outcomes, adjusted for sex and race, with standard errors clustered at the patient level.
Results: No bacterial species were significantly associated with RSS after correction for multiple testing. Klebsiella pneumoniae was associated with a diagnosis of BPD (adjusted p = 0.026), but no organisms were significantly associated with prolonged time to extubation. In secondary analyses, the presence of several organisms was significantly associated with higher MAP, including K. pneumoniae (β = 2.66, FDR-adjusted p = 0.014).
Conclusions: Multiple bacterial species identified on quantitative BAL culture were associated with higher mean airway pressure, and K. pneumoniae was additionally associated with BPD diagnosis. These findings support the potential utility of quantitative microbiologic data in risk stratification and management of neonatal respiratory disease.
Keywords: Klebsiella pneumoniae; bronchoscopy; microbiology; prematurity.
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