Changes in sputum bacterial density in people with bronchiectasis: BRONCH UK Study data

Abstract

<b>Introduction:</b> We investigated (i) changes in total bacterial density in sputum during clinical stability and PEx and (ii) the relationship between total bacterial density, inflammation and FEV₁. <b>Methods:</b> Two subgroups from the BRONCH-UK cohort study (n=74) were analysed; A) clinically stable patients (n=54) who provided sputum at baseline and one further visit within 12 months; B) PEx patients (n=20) who provided sputum at baseline, pre- and post-Abx treatment of an PEx and one further visit within 12 months when clinically stable. Total bacterial density (16S rRNA) was determined by qPCR and patients were stratified as having moderate (10⁵- &lt;10⁷ copies/ml) or high bacterial (≥10⁷ copies/ml) density. Non-parametric tests were used for analysis. <b>Results:</b> Of 74 patients, 58% female, mean (SD) age 66 (8.7) years, FEV₁ 67 (20.5) %. At baseline, 23/54 patients (43%) in the stable group had high bacterial density vs. 7/20 patients (35%) in the PEx group. No difference was observed in age, FEV₁ or CRP in patients with moderate vs. high bacterial density (p&gt;0.05). Between baseline and final stable visit, there was no difference in bacterial density (median Log₁₀ 16S rRNA 6.8 [4.9-7.9]&nbsp;vs. 6.7 [5.2-8.0] copies/ml, respectively; p= 0.58) and no significant change in the number of patients with high or moderate bacterial density. No difference was observed in bacterial density pre and post Abx treatment (median Log₁₀ 16S rRNA 6.9 [5.4-8.0] vs 7.1 [5.7-8.1] copies/ml, respectively; p=0.28). Bacterial density did not correlate with FEV₁ (r=0.11; p=0.37) or CRP (r=0.10; p=0.40) at baseline. <b>Conclusion:</b> Bacterial density was stable during clinical stability and did not change following Abx therapy of a PEx.