More than Mycobacterium tuberculosis : specific site-of-disease microbial communities, functional capacities, and their distinct clinical profiles in tuberculous lymphadenitis
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Lymphadenitis is the most common extrapulmonary tuberculosis (EPTB) manifestation and a major cause of death. The microbiome is important to human health but uninvestigated in EPTB. We profiled the site-of-disease lymph node microbiome in tuberculosis lymphadenitis (TBL).
Fine needle aspiration biopsies (FNABs) were collected from 159 pre-treatment presumptive TBL patients in Cape Town, South Africa. 16S Illumina MiSeq rRNA gene sequencing was done.
We analysed 89 definite TBLs (dTBLs) and 61 non-TBLs (nTBLs), which had similar α-but different β-diversities (p=0.001). Clustering identified five lymphotypes prior to TB status stratification: Mycobacterium-, Prevotella - and Streptococcus -dominant lymphotypes were more frequent in dTBLs whereas a Corynebacterium-dominant lymphotype and a fifth lymphotype (no dominant taxon) were more frequent in nTBLs. When restricted to dTBLs, clustering identified a Mycobacterium-dominant lymphotype with low α-diversity and other non- Mycobacterium -dominated lymphotypes (termed Prevotella-Corynebacterium and Prevotella-Streptococcus ). The Mycobacterium dTBL lymphotype was associated with HIV-positivity and clinical features characteristic of severe lymphadenitis (e.g., node size). dTBL microbial communities were enriched with potentially proinflammatory microbial short chain fatty acid metabolic pathways (propanoate, butanoate) vs. those in nTBLs. 11% (7/61) of nTBLs had Mycobacterium reads.
TBL at the site-of-disease is not microbially homogenous and distinct microbial community clusters exist that are associated with different immunomodulatory potentials and clinical characteristics. Non- Mycobacterium -dominated dTBL lymphotypes, which contain taxa potentially targeted by TB treatment, represent less severe potentially earlier stage disease. These investigations lay foundations for studying the microbiome’s role in lymphatic TB and the long-term clinical significance of lymphotypes requires prospective evaluation.