DOI: 10.5061/dryad.m0cfxpp37
title: Chlorhexidine oral rinses for symptomatic COPD: a randomized, blind, placebo-controlled preliminary study

description: Background: Chlorhexidine oral rinses decrease ventilator-associated
 pneumonia but its effect on COPD is unknown. Research Question: Will a
 preliminary study of the effect of twice-daily chlorhexidine oral rinses
 on oral and lung microbiota biomass and respiratory symptoms, compared to
 placebo, support the conduct of a larger clinical trial? Study Design and
 Methods: Participants aged 40-85 with COPD and chronic respiratory
 symptoms were randomized 1:1 to twice-daily 0.12% chlorhexidine oral
 rinses vs. placebo. Results: Forty-four participants were recruited
 between September 8, 2014 and May 30, 2019. Our primary outcome was a
 change in oral and sputum microbiota biomass during the study as assessed
 by 16S rRNA copy numbers. Neither the oral microbiota nor the sputum
 microbiota biomass decreased significantly in those using chlorhexidine
 compared with placebo (oral microbiota mean log10 difference [SE] = -0.103
 [0.23], 95% CI: -0.59, 0.38, p=0.665; sputum microbiota 0.80 [0.46], 95%
 CI: -0.15, 1.75, p=0.096). Chlorhexidine decreased both oral and sputum
 microbiota alpha (Shannon) diversity (linear regression estimate [SE]
 oral: -0.349 [0.091], p=0.001; sputum -0.622 [0.169], p=0.001).
 Chlorhexidine use did not decrease systemic inflammatory markers compared
 to placebo (CRP [chlorhexidine 1.8 ± 7.5 vs. placebo 0.4 ± 6.8, p=0.467],
 fibrinogen [22.5 ± 77.8 vs. 10.0 ± 77.0, p=0.406], or leukocytes [0.2 ±
 1.8 vs. 0.5 ± 1.8, p=0.560]). Chlorhexidine use decreased St. George’s
 Respiratory Questionnaire scores compared to placebo (chlorhexidine -4.7 ±
 8.0 vs. placebo 1.7 ± 8.9, p=0.032). Interpretation: We did not detect a
 significant difference in microbiota biomass due to chlorhexidine use.
 Chlorhexidine decreased oral and sputum microbiota alpha diversity and
 improved respiratory health-related quality of life compared to placebo.
 Our results support the performance of a larger clinical trial.
description: At visit 1, participants provided medical history, performed
 spirometry, completed the St. George’s Respiratory Questionnaire (SGRQ),
 were instructed on how to complete the Breathlessness, Cough, and Sputum
 Scale (BCSS) daily diaries, and provided blood, oral, and induced sputum
 samples prior to randomization. Oral and sputum sample volumes were
 recorded. Participants returned 8 weeks later to return BCSS diaries,
 complete the SGRQ, assess outcomes, and provide blood, oral, and sputum
 samples. The clinical laboratories at the MVAMC
 determined WBC and differential, fibrinogen, CRP levels, and sputum gram
 stain and culture results. All oral rinses, sputum samples, and unused
 sterile water (control samples) were frozen immediately and until DNA
 extraction. 16S rRNA quantification and 16S rRNA V4 MiSeq sequencing was
 performed at the University of Minnesota Genomics Center as previously
 described. The primary outcome was change in oral and
 sputum microbiota biomass after 8 weeks of chlorhexidine vs. placebo use,
 compared to baseline values as assessed by 16S rRNA quantification. The
 primary outcome was chosen based on the mechanism of action of
 chlorhexidine, however sample size calculations were based on a change in
 alpha diversity (a secondary outcome) due to data availability at study
 initiation. At a sample size of 20 per group and across a plausible range
 of effect sizes, our study had 67-94% power to detect a change in alpha
 diversity associated with chlorhexidine use. Sample size calculations are
 available in the online supplement. Secondary outcomes included: sputum
 and oral microbiota Shannon and Simpson diversity; sputum and oral
 microbiota taxonomy; inflammatory markers (WBC, fibrinogen, and CRP); BCSS
 scores; SGRQ score; and assessment of adverse events.
 Baseline variables were compared using Fisher's Exact Test
 for categorical variables or the Wilcoxon Two-Sample Test for continuous
 variables. Means are presented with standard deviations (SD); mean
 differences and parameter estimates are presented with their associated
 standard error (SE). All analyses were performed using
 SAS version 9.4 (SAS Institute) and the intention-to-treat principle. A
 two-sided type I error of 0.05 was used. Correction of the Type I error
 rate for multiple testing was performed using the Step-down Bonferroni
 method. For the primary analysis of both
 normalized oral wash and normalized sputum biomass count, values
 were transformed to the log<sub>10</sub>
 scale and the mean
 difference between treatment groups was compared using the two-sample
 t-test. A multiple imputation procedure was used to impute
 each unavailable sputum weight. Linear regression was
 used to examine the effect of treatment group on the 8-week change in the
 Shannon and Simpson biodiversity indices, BCSS, SGRQ and inflammatory
 markers separately, with each model adjusted for the baseline value of the
 measure. Subgroup analyses of participants who did not
 receive antibiotics during the study were also performed for the outcomes
 of biomass and biodiversity. For taxa abundance analyses,
 treatment effects on abundance were examined by modeling the 8-week change
 using linear regression, adjusted for baseline count. Analysis was
 restricted to genera with &lt;20% of values equal to zero. Fisher’s
 Exact Test was used to determine the proportion with a genus detected at
 Week 8 vs. baseline compared between treatment groups. Results were
 corrected for multiple comparisons.