Mycobacterium tuberculosis programs mesenchymal stem cells to establish dormancy and persistence.

Tuberculosis (TB) remains a major infectious disease worldwide. TB treatment displays a biphasic bacterial clearance, in which the majority of bacteria clear within the first month of treatment, but residual bacteria remain nonresponsive to treatment and eventually may become resistant. Here, we have shown that Mycobacterium tuberculosis was taken up by mesenchymal stem cells (MSCs), where it established dormancy and became highly nonresponsive to isoniazid, a major constituent of directly observed treatment short course (DOTS). Dormant M. tuberculosis induced quiescence in MSCs and promoted their long-term survival. Unlike macrophages, where M. tuberculosis resides in early-phagosomal compartments, in MSCs the majority of bacilli were found in the cytosol, where they promoted rapid lipid synthesis, hiding within lipid droplets. Inhibition of lipid synthesis prevented dormancy and sensitized the organisms to isoniazid. Thus, we have established that M. tuberculosis gains dormancy in MSCs, which serve as a long-term natural reservoir of dormant M. tuberculosis. Interestingly, in the murine model of TB, induction of autophagy eliminated M. tuberculosis from MSCs, and consequently, the addition of rapamycin to an isoniazid treatment regimen successfully attained sterile clearance and prevented disease reactivation.

Linezolid Induced Adverse Drug Reactions - An Update.

Treatment regimen recommended for resistant tuberculosis consists of various drugs and these drugs are prescribed for at least 12-15 months. Such a long duration therapy and high dose of antibiotics result in adverse drug reactions (ADRs). ADRs may lead to various complications in disease management like replacement of drugs, dose increment, therapy withdrawal, etc. Linezolid is one of those drugs, practiced as an anti-mycobacterial agent and it is an important member of drug regimen for MDR and XDR tuberculosis. Linezolid is a broad spectrum antibiotic known for its unique mechanism of inhibition of resistant pathogenic strains. However, it causes serious adverse effects like thrombocytopenia, optic neuropathy, peripheral neuropathy, lactic acidosis, etc. Literature suggests that Linezolid can cause severe ADRs which affect patient compliance and hinder in therapy to a larger extent. Recent studies confirm the possibility of ADRs to be predicted with genetic make-up of individuals. To effectively deliver the available treatment regimen and ensure patient compliance, it is important to manage ADRs more efficiently. The role of pharmacogenomics in reducing adverse drug effects has been recently explored. In the present review, we discussed about Linezolid induced adverse drug reactions, mechanisms and genetic associations.