Tuberculosis is a serious airborne disease for which drug resistance has become a major issue. The long treatment time (6-24 months) is particularly problematic because it creates difficulties in maintaining patient adherence to therapy. Sporadic treatment then fosters the emergence of antimicrobial-resistant Mycobacterium tuberculosis, the causative agent of tuberculosis. Long treatment times are needed, presumably because even active infections contain some non-growing (dormant) bacilli that are not readily killed by most antimicrobials. Our goal is to obtain new fluoroquinolones that rapidly kill non-growing M. tuberculosis and would thereby reduce treatment time radically. As part of their mechanism of action, quinolones trap DNA gyrase as drug-enzyme-DNA complexes in which the DNA is broken but held together by protein. Formation of these complexes, which are thought to block bacterial growth, is reversed by chelation of magnesium ion. Recent work leads us to propose that at lethal quinolone concentrations, which are higher than required to block growth, additional drug binding generates a new complex that is not reversed by chelation of magnesium. We propose that the new complex leads to chromosome fragmentation, which in growing cells is followed by a lethal cascade of reactive oxygen species. Only a quinolone subset kills non-growing cells. These quinolones are proposed to stimulate chromosome fragmentation that causes death directly, without requiring a cascade of reactive oxygen species. The above scenario will be tested by designing, synthesizing, and characterizing new quinolones and quinolone- derived structures for interactions with gyrase and for killing non-growing cells.
In aim 1, tests with cultured cells will examine relationships between experimental compounds and gyrase structure, using gyrase mutants, in-vivo crosslinking, drug structure variation, and molecular modeling. The primary readout will be cell death when protein synthesis is inhibited to eliminate the lethal pathway operating with growing cells.
In aim 2, experiments will focus on biochemical properties of the newly discovered quinolone-gyrase-DNA complex formed at the elevated drug concentrations required to kill bacteria. Attention will focus on drug structures that facilitate release of DNA breaks from gyrase-mediated constraint.
In aim 3, drug structure- lethal activity relationships will be determined with computational analyses (eg. 3-dimensional quantitative structure-activity relationship models) that do not rely on knowledge of drug-gyrase interactions. Superior compounds from work on each of the three aims will be examined for lethality with three mycobacterial growth-arrest systems. The expected outcomes are lead compounds and novel rules for developing new quinolone-type inhibitors that rapidly kill non-growing, persister cells.

Public Health Relevance

New fluoroquinolones will be developed to kill non-growing bacterial subpopulations thought to be responsible for the long treatment times needed to cure tuberculosis. The work will test a new molecular explanation for how fluoroquinolones kill non-growing bacteria. The products of the work will be 1) a molecular understanding of quinolone-mediated killing of non-growing cells, and 2) a new type of quinolone that will help restrict the emergence of quinolone resistance with many bacterial infections.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
Project #
Application #
Study Section
Drug Discovery and Mechanisms of Antimicrobial Resistance Study Section (DDR)
Program Officer
Boyce, Jim P
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Medicine & Dentistry of NJ
Public Health & Prev Medicine
Schools of Medicine
United States
Zip Code
Li, Liping; Hong, Yuzhi; Luan, Gan et al. (2014) Ribosomal elongation factor 4 promotes cell death associated with lethal stress. MBio 5:e01708
Zhao, Xilin; Drlica, Karl (2014) Reactive oxygen species and the bacterial response to lethal stress. Curr Opin Microbiol 21:1-6
Mustaev, Arkady; Malik, Muhammad; Zhao, Xilin et al. (2014) Fluoroquinolone-gyrase-DNA complexes: two modes of drug binding. J Biol Chem 289:12300-12
Dorsey-Oresto, Angella; Lu, Tao; Mosel, Michael et al. (2013) YihE kinase is a central regulator of programmed cell death in bacteria. Cell Rep 3:528-37
Metzler, Kelli; Drlica, Karl; Blondeau, Joseph M (2013) Minimal inhibitory and mutant prevention concentrations of azithromycin, clarithromycin and erythromycin for clinical isolates of Streptococcus pneumoniae. J Antimicrob Chemother 68:631-5
Mosel, Michael; Li, Liping; Drlica, Karl et al. (2013) Superoxide-mediated protection of Escherichia coli from antimicrobials. Antimicrob Agents Chemother 57:5755-9
Marks, Kevin R; Malik, Muhammad; Mustaev, Arkady et al. (2011) Synthesis and evaluation of 1-cyclopropyl-2-thioalkyl-8-methoxy fluoroquinolones. Bioorg Med Chem Lett 21:4585-8
Wu, Xiangli; Wang, Xiuhong; Drlica, Karl et al. (2011) A toxin-antitoxin module in Bacillus subtilis can both mitigate and amplify effects of lethal stress. PLoS One 6:e23909
Malik, Muhammad; Marks, Kevin R; Mustaev, Arkady et al. (2011) Fluoroquinolone and quinazolinedione activities against wild-type and gyrase mutant strains of Mycobacterium smegmatis. Antimicrob Agents Chemother 55:2335-43
Liang, Beibei; Bai, Nan; Cai, Yun et al. (2011) Mutant prevention concentration-based pharmacokinetic/pharmacodynamic indices as dosing targets for suppressing the enrichment of levofloxacin-resistant subpopulations of Staphylococcus aureus. Antimicrob Agents Chemother 55:2409-12

Showing the most recent 10 out of 27 publications