Partial Depletion of Pth Increases Susceptibility to Macrolide Drug Treatment in M. Tuberculosis

Abstract

The goal of this work was to investigate whether a ubiquitous bacterial protein, peptidyl-tRNA hydrolase (Pth), would be an appropriate candidate for target-based drug discovery research directed against pathogenic M. tuberculosis. Many successful antibiotics target protein synthesis machinery to arrest bacterial growth. Hydrolysis of peptidyl-tRNA by Pth is an important action during recovery from stalled protein synthesis. To determine whether an attack on Pth would damage M. tuberculosis, several Pth depletion strains were created. A tightly regulated knockdown strain confirmed essentiality of the protein for normal growth. Loosely regulated partial knockdown (hypomorph) strains were created for use in drug-susceptibility testing which showed that depletion of Pth induced hypersensitivity to macrolide antibiotics erythromycin, clarithromycin, and azithromycin. These drugs are comparatively ineffective against M. tuberculosis and are not used in first line treatment regimens. Pth was shown to be an attractive candidate for drug discovery research not only because it is essential but because abrogation of Pth function may sensitize this pathogen to an entire class of well-characterized drugs not typically used to combat M. tuberculosis.