L5 Tuberculosis

History and Evolution

Tuberculosis (TB), caused by Mycobacterium tuberculosis complex, has killed over 1 billion in 200 years, known historically as "White Death." Identified by Robert Koch in 1882, it evolved 2.5 million years ago, mirroring human mitochondrial genome changes. Seven major lineages show genomic reduction (6.2 to 4.5 million bp), with modern lineages (e.g., Lineage 2 & 4) dominating due to deletions like TbD1. M. bovis, impacting all warm-blooded vertebrates, caused 30% of European TB cases in the 1900s until controlled by pasteurization and BCG vaccine (1921).

Traditional Diagnosis and Surveillance

TB diagnosis involves physical exams, X-rays, sputum smears (acid-fast stain, low sensitivity/specificity), and culture (gold standard, >28 days). Molecular tests (e.g., Xpert MTB/RIF PCR) detect M. tuberculosis and resistance in <2 hours. Surveillance includes contact tracing, latent case finding (tuberculin skin test, interferon-gamma assays), and molecular typing (MIRU-VNTR, limited resolution). Whole-genome sequencing (WGS) identifies clonal relationships (<12 SNPs) and strain types (e.g., Beijing, Haarlem).

Case Study

TB diagnosis involves physical exams, X-rays, sputum smears (acid-fast stain, low sensitivity/specificity), and culture (gold standard, >28 days). Molecular tests (e.g., Xpert MTB/RIF PCR) detect M. tuberculosis and resistance in <2 hours. Surveillance includes contact tracing, latent case finding (tuberculin skin test, interferon-gamma assays), and molecular typing (MIRU-VNTR, limited resolution). Whole-genome sequencing (WGS) identifies clonal relationships (<12 SNPs) and strain types (e.g., Beijing, Haarlem).

Space

Space