Latent class analysis to define radiological subgroups in pulmonary nontuberculous mycobacterial disease.

BACKGROUND: Nontuberculous mycobacterial (NTM) pulmonary disease has conventionally been classified on the basis of radiology into fibrocavitary and nodular-bronchiectatic disease. Whilst being of great clinical utility, this may not capture the full spectrum of radiological appearances present. The aim of this study was to use latent class analysis (LCA) as an unbiased method of grouping subjects with NTM-pulmonary disease based on their CT features and to compare the clinical characteristics of these groups. METHODS: Individuals with NTM-pulmonary disease were recruited and a contemporaneous CT scan obtained. This was scored using an NTM-specific scoring system. LCA was used to identify groups with common radiological characteristics. The analysis was then repeated in an independent cohort. RESULTS: Three classes were identified in the initial cohort of 85 subjects. Group 1 was characterised by severe bronchiectasis, cavitation and aspergillomas, Group 2 by relatively minor radiological changes, and Group 3 by predominantly bronchiectasis only. These findings were reproduced in an independent cohort of 62 subjects. Subjects in Group 1 had a lower BMI and serum albumin, higher serum CRP, and a higher mortality. CONCLUSIONS: These findings suggest that NTM-pulmonary may be divided into three radiological subgroups, and that important clinical and survival differences exist between these groups.

Mycobacterium abscessus pathogenesis identified by phenogenomic analyses.

The medical and scientific response to emerging and established pathogens is often severely hampered by ignorance of the genetic determinants of virulence, drug resistance and clinical outcomes that could be used to identify therapeutic drug targets and forecast patient trajectories. Taking the newly emergent multidrug-resistant bacteria Mycobacterium abscessus as an example, we show that combining high-dimensional phenotyping with whole-genome sequencing in a phenogenomic analysis can rapidly reveal actionable systems-level insights into bacterial pathobiology. Through phenotyping of 331 clinical isolates, we discovered three distinct clusters of isolates, each with different virulence traits and associated with a different clinical outcome. We combined genome-wide association studies with proteome-wide computational structural modelling to define likely causal variants, and employed direct coupling analysis to identify co-evolving, and therefore potentially epistatic, gene networks. We then used in vivo CRISPR-based silencing to validate our findings and discover clinically relevant M. abscessus virulence factors including a secretion system, thus illustrating how phenogenomics can reveal critical pathways within emerging pathogenic bacteria.

Regulation of phagocyte triglyceride by a STAT-ATG2 pathway controls mycobacterial infection.

Mycobacterium tuberculosis remains a global threat to human health, yet the molecular mechanisms regulating immunity remain poorly understood. Cytokines can promote or inhibit mycobacterial survival inside macrophages and the underlying mechanisms represent potential targets for host-directed therapies. Here we show that cytokine-STAT signalling promotes mycobacterial survival within macrophages by deregulating lipid droplets via ATG2 repression. In Drosophila infected with Mycobacterium marinum, mycobacterium-induced STAT activity triggered by unpaired-family cytokines reduces Atg2 expression, permitting deregulation of lipid droplets. Increased Atg2 expression or reduced macrophage triglyceride biosynthesis, normalizes lipid deposition in infected phagocytes and reduces numbers of viable intracellular mycobacteria. In human macrophages, addition of IL-6 promotes mycobacterial survival and BCG-induced lipid accumulation by a similar, but probably not identical, mechanism. Our results reveal Atg2 regulation as a mechanism by which cytokines can control lipid droplet homeostasis and consequently resistance to mycobacterial infection in Drosophila.