Microbiota of the Lung Tuberculoma: Paucibacillary Bacterial Community.

Caseum, the central necrotic material of tuberculous lesions, is a reservoir of drug-resistant persisting Mycobacterium tuberculosis (MTB). However, tubercle bacilli are not the only bacterial inhabitants of this necrosis. We discuss the available data on metagenomic and amplicon sequencing of 16S rRNA of caseous necrosis from surgically excised tuberculosis (TB) foci. This approach facilitated the characterization of the biodiversity and the potential biochemical pathways of these bacterial communities. We postulate that in terms of MTB content relative to satellite anaerobic lipophilic bacteria, caseum may present two distinct terminal states. "True" TB necrosis, containing 99.9% tubercle bacilli, and a polymicrobial community wherein anaerobic lipophilic bacteria predominate over MTB. Isolation from caseum and genomic characterization of several Corynebacterium and Staphylococcus species support this concept.