COPD is characterized by increased detection of Haemophilus influenzae, Streptococcus pneumoniae and a deficiency of Bacillus species

Abstract 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 S t G eorge's R espiratory Q uestionnaire (Spearman's r = 0.336, P = 0.013). Significantly lower levels of culturable Bacillus species were identified compared with healthy controls. PCR analyses revealed increased rates of detection of potentially pathogenic bacteria with H aemophilus influenzae detection associated with higher sputum levels of NE and IL ‐1β, while S treptococcus pneumoniae was 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.