Alanning numbers of pathogenic bacteria are now resistant to multiple antibiotics. This problem is perhaps most pressing for two common hospital-borne pathogens, vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). In the case of VRE, the resistance genes are encoded on large plasmids. Interestingly, through a survey of multiple VRE isolates we have discovered that these plasmids use toxin-antitoxin (TA) systems to maintain themselves in the bacterial host. In this system, if a plasmid-free daughter cell arises during cell division the labile antitoxin is degraded and the toxin kills the cell. We have pursued an antibacterial strategy based on the identification of small molecules that activate the latent toxin proteins in the bacterial cell;these compounds would thus induce cell death. Through surveys of VRE, MRSA, Staphylococcus sp., and P. aeruginosa, we have found that three particular TA systems are prevalent: CcdAB, RelBE, and MazEF. Through highthroughput cell-based screening we have now identified compounds that kill cells in a CcdAB-dependant fashion, and others that kill in a RelBE-dependent fashion. Described herein is a comprehensive plan designed to fully validate TA disruption as a tractable antibacterial target. This will involved chemical optimization of the lead compounds for CcdAB and RelBE, high-throughput screening to identify compounds that activate the toxins from these three TA pairs, and the use of peptides as TA disruptors.

Public Health Relevance

The alarming rise of multi-drug resistant bacteria, combined with the severe slowdown in the discovery and development of novel antibiotics, has led to a situation where increasingly large numbers of infections simply cannot be treated with antibiotics. Described herein is an antibacterial strategy based on the activation of latent toxin- antitoxin systems that we have found to reside within bacterial cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM068385-07
Application #
7924133
Study Section
Drug Discovery and Mechanisms of Antimicrobial Resistance Study Section (DDR)
Program Officer
Fabian, Miles
Project Start
2003-04-15
Project End
2012-08-31
Budget Start
2010-09-01
Budget End
2012-08-31
Support Year
7
Fiscal Year
2010
Total Cost
$299,524
Indirect Cost
Name
University of Illinois Urbana-Champaign
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
041544081
City
Champaign
State
IL
Country
United States
Zip Code
61820
Larson, Amy S; Hergenrother, Paul J (2014) Light activation of Staphylococcus aureus toxin YoeBSa1 reveals guanosine-specific endoribonuclease activity. Biochemistry 53:188-201
van Rensburg, Julia J; Hergenrother, Paul J (2013) Detection of endogenous MazF enzymatic activity in Staphylococcus aureus. Anal Biochem 443:81-7
Williams, Julia J; Hergenrother, Paul J (2012) Artificial activation of toxin-antitoxin systems as an antibacterial strategy. Trends Microbiol 20:291-8
Halvorsen, Elizabeth M; Williams, Julia J; Bhimani, Azra J et al. (2011) Txe, an endoribonuclease of the enterococcal Axe-Txe toxin-antitoxin system, cleaves mRNA and inhibits protein synthesis. Microbiology 157:387-97
Williams, Julia J; Halvorsen, Elizabeth M; Dwyer, Ellen M et al. (2011) Toxin-antitoxin (TA) systems are prevalent and transcribed in clinical isolates of Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus. FEMS Microbiol Lett 322:41-50
Williams, Julia J; Hergenrother, Paul J (2008) Exposing plasmids as the Achilles'heel of drug-resistant bacteria. Curr Opin Chem Biol 12:389-99
Thomas, Jason R; Hergenrother, Paul J (2008) Targeting RNA with small molecules. Chem Rev 108:1171-224
Wang, Nora R; Hergenrother, Paul J (2007) A continuous fluorometric assay for the assessment of MazF ribonuclease activity. Anal Biochem 371:173-83
Moritz, Elizabeth M; Hergenrother, Paul J (2007) Toxin-antitoxin systems are ubiquitous and plasmid-encoded in vancomycin-resistant enterococci. Proc Natl Acad Sci U S A 104:311-6
Hergenrother, Paul J (2006) Obtaining and screening compound collections: a user's guide and a call to chemists. Curr Opin Chem Biol 10:213-8

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