Objectives: To determine and compare microbial community structures using cough swabs collected from non-expectorating CF patients and healthy control (HC) participants.
Methods: Cough swabs were collected during outpatient appointments at the adult and paediatric CF Centres of the Belfast Health and Social Care Trust (Belfast City Hospital and Royal Belfast Hospital for Sick Children). Healthy, age matched, control (HC) subjects were invited to attend a single study visit by means of e-mail circulation among work colleagues at Queen’s University Belfast and Belfast Health and Social Care Trust. Extended qualitative microbial culture (absence/presence) was performed under aerobic, microaerophilic (5%CO2) and anaerobic conditions at 37°C for 24-72 hrs.
Results: Groups (CF vs HC) were well matched for median [range] age (CF, 13 [6-48] years; HC, 15 [6-44] years), gender (female: CF, 56.9%; HC, 42.9%), mean [SD] FEV1 (CF, 86.7 [19.6] pp; HC, 90.2 [11.3] pp) and mean [SD] BMI (CF, 19.9 [4.0] kg/m2; HC, 20.8 [4.7] kg/m2). The median [range] of the cough swab community richness of the CF group (n=50: 7 [0-12]) was greater compared to the HC group (n=30: 6 [0-10]) (P=0.01). Permutational multivariate analysis (Adonis) showed differences in microbial communities between the CF and HC groups (R2=0.035; P=0.01) and between age groups (6-18 vs ≥18 years: R2=0.036; P=0.01) but not gender (R2=0.015; P=0.30). However, the percentage of variation in distances explained by group (3.5%) and age (3.6%) was small. A Bray-Curtis dissimilarity index indicated that there was significant intra-clustering within each of the two groups.
Conclusion: Similar to results from previous studies using induced sputum, culture of cough swabs revealed differences in microbial community signatures between CF patients and HC participants.
Funding: HSC R&D, Public Health Agency (Northern Ireland), the MRC and the US NIH (HL092964, HL084934, 5R01 HL092964-04) through a US-Ireland Partnership Grant.