COPD is characterized by increased detection ofHaemophilus influenzae,Streptococcus pneumoniaeand a deficiency ofBacillusspecies

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Background and objective:Chronic obstructive pulmonary disease (COPD) is characterized by progressive airflow limitation and inflammation. Airway bacterial colonization is increased in COPD; however, the role of potentially pathogenic and non-pathogenic bacteria in the pathogenesis of disease is unclear. This study characterized the presence of bacteria in a well-characterized cohort of adults with COPD and healthy controls.Methods:Adults with COPD (n= 70) and healthy controls (n= 51) underwent clinical assessment and sputum induction. Sputum was dispersed, and total and differential cell counts were performed. Bacteria were cultured, identified and enumerated. Supernatants were assessed for neutrophil elastase (NE) and IL-1β. Common respiratory pathogens were also determined using real-time PCR.Results:Participants with COPD had a typical neutrophilic inflammatory profile. The total load of bacteria was increased in COPD and was associated with poorer respiratory health status, as measured by the St George's Respiratory Questionnaire (Spearman's r = 0.336,P= 0.013). Significantly lower levels of culturableBacillusspecies were identified compared with healthy controls. PCR analyses revealed increased rates of detection of potentially pathogenic bacteria withHaemophilus influenzaedetection associated with higher sputum levels of NE and IL-1β, whileStreptococcus pneumoniaewas more common in male ex-smokers with emphysema and a deficit in diffusion capacity.Conclusion:Non-pathogenic and pathogenic bacteria were altered in the sputum of patients with COPD. These observations highlight the potential to identify treatment and management strategies that both target specific bacterial pathogens and restore the microbial balance, which may lead to reductions in inflammation and subsequent improvements in lung health.SUMMARY AT A GLANCEParticipants with COPD had increased bacterial load with reduced Bacillus colonization. The total load of bacteria was associated with reduced health status. Increased Haemophilus influenzae detection was linked to neutrophilic inflammation, particularly neutrophil elastase, interleukin-1-β and polybacterial detection. Increases in S. pneumoniae were linked to impaired diffusion capacity.

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