Detection of cell-dissociated non-typeable haemophilus influenzae in the airways of patients with chronic obstructive pulmonary disease

Background: Non-typeable Haemophilus influenzae (NTHi) is the most commonly found pathogen in the lower respiratory airways of patients with COPD. NTHi is predominantly regarded as an intracellular pathogen; however, like most pathogens, it can exist and co-exist in two broad forms: cell-associated (intracellularly or adhered to cells) or cell-dissociated (biofilm dispersed or planktonic). We sought to investigate if cell-dissociated NTHi can be detected from the sputum of COPD patients and assess this relationship to disease severity and airway inflammation. Methods: DNA was extracted from the sputum plug and cell-free supernatant to quantify absolute (cell-associated and cell-dissociated NTHi) and cell-dissociated NTHi, respectively, from 87 COPD subjects attending an observational longitudinal COPD exacerbation study. NTHi was quantified using TaqMan hydrolysis probes, targeting the OMP P6 gene using qPCR. Results: At stable state cell-dissociated NTHi was detected 56% of subjects with a median (IQR) of 9.95x102 gene copies (1.26x102 to 1.90x104). Cell-dissociated NTHi correlated with absolute NTHi levels (r=0.34, p Conclusion: In patients with COPD, NTHi can exist in both cell-associated and cell-dissociated forms. Cell-dissociated NTHi is associated with neutrophilic airway inflammation during exacerbations of COPD and may be a driving factor in worsening lung function during these episodes.