Objectives
To assess the effects of Pseudomonas aeruginosa (Pa) and Staphylococcus aureus (Sa) infection on lower airway inflammation and clinical status in young children with cystic fibrosis (CF).
Study design
We studied 111 children < 6 years of age who had two Pa positive oropharyngeal cultures within 12 months. We examined bronchoalveolar lavage fluid (BALF) inflammatory markers (cell count, differential, IL-8, IL-6, neutrophil elastase), CF-related bacterial pathogens, exotoxin A serology, and clinical indicators of disease severity.
Results
Young children with CF with both upper and lower airway Pa infection had higher neutrophil counts, IL-8 and free neutrophil elastase levels, increased likelihood of positive exotoxin A titers, and lower Shwachman scores compared with those with positive upper airway cultures only. Sa was associated with increased lower airway inflammation and the presence of both Pa and Sa had an additive effect on concentrations of lower airway inflammatory markers. BALF markers of inflammation increased with numbers of different bacterial pathogens detected.
Conclusions
Young children with CF with upper and lower airway Pa infection have heightened endobronchial inflammation and poorer clinical status compared with children with only upper airway Pa infection. The independent and additive effects of Sa on inflammation support the importance of polymicrobial infection in early CF lung disease.
Rationale: The conducting of clinical trials in infants with cystic fibrosis (CF) has been hindered by lack of sensitive outcome measures. Objectives: To evaluate safety, feasibility, and ability to detect abnormalities in lung function of serial pulmonary function tests (PFTs) in infants with CF. Methods: Multicenter observational study using a commercial device, rigorous training, ongoing quality control, and over-reading of data by an independent panel. Raised volume rapid thoracoabdominal compression technique and plethysmography were performed at enrollment and at 6 and 12 months, with an additional 1-month reproducibility visit. Measurements and Main Results: A total of 342 procedures were performed in 100 infants with CF at 10 centers. FRC measurements were acceptable at a higher proportion of study visits (89%) than raised volume (72%) or fractional lung volume (68%) measurements. Average Z scores for many parameters differed significantly from historical control values. Mean (95% confidence interval) Z scores were: 20.52 (20.78 to 20.25) for forced expiratory flow at 75% (FEF 75 ) for FVC; 1.92 (1.39-2.45) for FRC; 1.22 (0.68-1.76) for residual volume; 0.87 (0.60-1.13) for FRC/total lung capacity; and 0.66 (0.27-1.06) for residual volume/total lung capacity. For future multicenter clinical trials using infant PFTs as primary endpoints, minimum detectable treatment effects are presented for several sample sizes. Conclusions: In this 10-center study, key PFT measures were significantly different in infants with CF than in historical control subjects. However, infant PFTs do not yet appear ready as primary efficacy endpoints for multicenter clinical trials, particularly at inexperienced sites, based on acceptability rates, variability, and potentially large sample sizes required to detect reasonable treatment effects.
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