Quantitative analysis of potentially pathogenic microbes (PPMs) in the induced sputum of non-smoker COPD (NS-COPD) subjects

Background: We have previously reported that both tobacco-smoke associated COPD (TS-COPD) and NS-COPD subjects exhibit a decline in lung function and progressive airway inflammation. The association between load of PPMs and lung function tests is well demonstrated among TS-COPD subjects. However, there is lack of knowledge with respect to NS-COPD subjects. We aimed to investigate the load of PPMs in the lower respiratory tract of NS-COPD subjects among the rural Indian population and its association with lung function. Methods: Induced sputum samples were collected from 19 healthy-nonsmoker (H-Nonsmokers), 8 healthy-smokers (H-smokers), 9 TS-COPD, and 12 NS-COPD to assess the load of P. aeruginosa (PA), S. pneumoniae (SP), H. influenzae (HI), and M. catarrhalis (MC) using SYBR-Green qPCR assay. Results: The load of PA, SP and HI was significantly higher in both TS-COPD and NS-COPD than healthy subjects (Figure 1). The load of MC was similar among all the groups. The load of PA and HI negatively correlated with FEV₁ %predicted (PA: r=-0.136, P=0.02; HI: r=-0.326, P=0.03), and FVC %predicted (PA: r=-0.153, P=0.03; HI: r=-0.432; P=0.048). Conclusion: To the best of our knowledge, this is the first study to report that load of PA, SP and HI is higher among NS-COPD subjects as compared to healthy non-smokers. Also, this bacterial load negatively correlates with lung function data.