Isotopic tracing in Mycobacterium tuberculosis-infected alveolar epithelial cells indicates metabolic specificity to their virulence and drug-resistance status.

Virulent and drug-resistant Mycobacterium tuberculosis strains exhibit distinct metabolic dependencies, with the multidrug-resistant S6 showing 18-fold higher intracellular growth in alveolar cells.

• Why it matters: Understanding strain-specific metabolic interactions within alveolar epithelial cells is crucial, as these cells are a primary infection site and may influence disease progression and treatment resistance.
• What they did: The study combined intracellular growth and viability assays with carbon isotope tracing of amino acids in A549 cells infected by various strains, including virulent, avirulent, drug-sensitive, and drug-resistant isolates.
• The result: Findings reveal that virulent strains rely more on central carbon pathways, with increased 13 C enrichment in host amino acids, especially alanine, while drug-resistant strains show unique enrichment patterns, suggesting potential targets for host-directed therapies.