Metabolic signatures of non-typeable Haemophilus influenzae from COPD sputum

People with COPD are susceptible to respiratory infections from bacteria including non-typeable <italic>Haemophilus influenzae</italic> (NTHi). NTHi isolates can persist for long periods during the stable state. There has been an interest in measuring gas soluble metabolites, volatile organic compounds (VOCs), for disease diagnostics by characterising bacterial species-specific signatures. NTHi strains isolated from COPD patient sputum samples (32 isolates, 18 patient visits) were cultured in vitro. VOCs released from NTHi were measured mass spectrometry. Assays were performed to assess biofilm quantity (crystal violet assay) and biofilm viability (LIVE/DEAD assay). NTHi cultures derived from COPD sputum had a distinct VOC profile. NTHi produced acetic acid, oxetane 3,3 dimethyl, dimethyl trisulfide and 2,4-di-tert-butylphenol (Figure 1). Indole production was high in some isolates but absent in others. Biofilm production and viability was variable between isolates, however specific VOCs correlated with both biofilm production (dimethyl trisulfide <italic>r</italic>=0.51, <italic>p</italic>=0.003) and biofilm viability (acetic acid <italic>r</italic>=0.36, <italic>p</italic>=0.043). NTHi isolates from COPD patients have a core VOC metabolite profile. Other VOCs are strain-specific and associate with bacterial phenotype, which may influence persistence in the lungs. Defining biomarkers of bacterial phenotypes may enable diagnostics to be developed that inform strain-specific therapeutics. <fig><object-id>erj;64/suppl_68/PA341/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>