S43 The lung mycobiome in nontuberculous mycobacterial pulmonary disease

<h3>Introduction</h3> The clinical course of nontuberculous mycobacterial pulmonary disease (NTM-PD) may be complicated by fungal lung infection. There are limited data on the lung mycobiome in NTM-PD. We hypothesised that there are differences in pulmonary fungal communities in NTM-PD depending on the NTM species, use of NTM treatment and the underlying lung disease. We sought to examine this longitudinally in individuals with <i>Mycobacterium avium</i> complex pulmonary disease (MAC-PD) and<i> M. abscessus</i> pulmonary disease (MAB-PD). <h3>Methods</h3> Sputum samples were acquired at baseline, weekly for 4 weeks and monthly up to 3 months from 37 participants who either had NTM-PD requiring treatment; or had NTM-PD not requiring treatment; or did not have NTM-PD. Additional samples were collected periodically from those on NTM treatment up to 18 months. DNA extracted from samples underwent 18S rRNA gene quantitative polymerase chain reaction to quantify total fungal burden; and internal transcribed space 2 sequencing on an Illumina MiSeq™ Next Generation Sequencer to characterise the fungal communities. <h3>Results</h3> No significant differences in pulmonary fungal biomass were identified between MAC-PD or MAB-PD. At baseline, alpha diversity analysis showed that fungal richness was higher in MAC-PD compared to MAB-PD (<i>P&lt;0.05</i>) and non-NTM controls (<i>P&lt;0.05</i>); and there was no difference in Shannon index, Simpson index or Pielou’s evenness index between groups. At 3 months, no differences in alpha diversity measures were identified. Among those on NTM treatment followed up until 18 months, there was a tendency towards higher Shannon index, Simpson index and Pielou’s evenness index in MAC-PD compared to MAB-PD at 12 months (<i>P=0.06</i> for all three measures); but not at 18 months. Beta diversity measured using the Bray-Curtis dissimilarity index was not different between groups according to underlying lung disease, NTM species or NTM treatment at baseline, 3 months or when assessed longitudinally across all timepoints. Sputum samples were dominated by <i>Candida</i>. The most prevalent genera thereafter were <i>Aspergillus</i> and <i>Exophiala</i>. <h3>Conclusions</h3> Differences in lung mycobiome composition between individuals with NTM-PD are limited. Pulmonary fungal communities do not appear to be perturbed by NTM treatment. Studies evaluating the impact on clinical outcomes appear warranted.