S145 The fungal burden in nontuberculous mycobacterial pulmonary disease

<h3>Introduction and Objectives</h3> Fungal lung infections may complicate the clinical trajectories of individuals with nontuberculous mycobacterial pulmonary disease (NTM-PD). It remains unclear whether NTM infection or therapies predispose to fungal disease. We hypothesised that there are differences in pulmonary fungal burden in NTM-PD according to NTM species, NTM treatment use and underlying structural lung diseases. We aimed to quantify this longitudinally in people with NTM-PD. <h3>Methods</h3> Sputum samples were acquired at baseline, weekly for 4 weeks and monthly up to 3 months from 37 participants who: had NTM-PD requiring treatment; had NTM-PD not requiring treatment; or did not have NTM-PD. Additional samples were collected monthly from those on NTM treatment until 12 months; then 3-monthly until 18 months. Sputum DNA was extracted using hexadecyl-trimethyl-ammonium bromide phenol chloroform. Total fungal burden was quantified using 18S rRNA gene quantitative polymerase chain reaction. <h3>Results</h3> There was no difference in pulmonary fungal burden at baseline or 3 months between: individuals with or without NTM-PD; those with <i>Mycobacterium avium</i> complex pulmonary disease (MAC-PD) or <i>Mycobacterium abscessus</i> pulmonary disease (MAB-PD); those on or off NTM treatment; or those with bronchiectasis, cystic fibrosis or chronic obstructive pulmonary disease. Fungal burden was higher in MAB-PD than MAC-PD (<i>P&lt;0.05</i>) following 6 months of NTM treatment; no difference was observed at 12 or 18 months. Among those on NTM treatment, there was no difference in the change in fungal burden that occurred between baseline and 6, 12 or 18 months according to NTM species or underlying lung disease. <h3>Conclusion</h3> No difference in pulmonary fungal burden between individuals with or without NTM-PD was found. In NTM-PD, no difference was observed in fungal burden according to underlying lung disease, NTM species (except at 6 months if on NTM treatment) or NTM therapy. NTM treatment was not associated with changes in fungal burden at 6, 12 or 18 months relative to baseline. Fungal burden alone is therefore unlikely to explain the clinical associations between NTM-PD and fungal sequelae. Using internal transcribed spacer 2 sequencing to evaluate the relationship between fungal diversity and NTM species, therapies and outcomes is therefore warranted. Please refer to page A288 for declarations of interest related to this abstract.