Exploration of quorum sensing inhibition in gram positive bacterial pathogens using mass spectrometry

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Daniel A. Todd (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Nadja Cech

Abstract: Antibiotics have been used as the primary treatment for bacterial infections since the 1940’s. Unfortunately, the use and misuse of antibiotics has led to the proliferation of antibiotic-resistant bacteria and resulted in the loss of antibiotic efficacy. Alternative strategies for fighting bacterial infections are needed to preserve our ability to cure bacterial infections. One strategy that has shown promise in in vitro and animal studies is the anti-virulence approach. Unlike the traditional antibiotic approach, which focuses on inhibiting bacterial growth, the anti-virulence approach focuses on disrupting bacteria pathogenesis. Inhibition of bacteria pathogenesis results in a less invasive infection that can be cleared by the innate immune system. Anti-virulence compounds have proven to be less susceptible to resistance development, which suggests their potential for long term therapeutic development. Unfortunately, only a limited number of anti-virulence compounds have been discovered and none have made it to the clinical setting. One goal of this research was to develop a new biological screening method to identify new anti-virulence compounds, particularly aimed at treating Gram-positive bacterial infections. In Gram-positive bacteria such as Staphylococcus aureus, virulence is regulated by the accessory gene regulator (agr) system. The agr system is a quorum sensing system activated by a small cyclic peptide known as AIP. The inhibition of the quorum sensing system results in the inhibition of bacterial virulence, making this system an ideal target for anti-virulent therapeutics. With this research, we developed a liquid chromatography-mass spectrometry (LC-MS) method to measure the activity of potential quorum sensing inhibitors based on their ability to inhibit AIP production. Prior to applying this method, it was necessary to develop approaches to detect the AIPs of interest directly from bacterial cultures, and to elucidate the structures of unknown AIPs. Mass spectrometry was employed to achieve both of these goals, and we detected eight AIPs directly from bacterial cultures. In addition, we elucidated the structures of two previously unidentified AIPs, that of Listeria monocytogenes and Staphylococcus saprophyticus. The newly developed assay was then utilized to identify a new quorum sensing inhibitor, 8-oxotetrahydrothalifendine, which was shown to act as a quorum sensing signal biosynthesis inhibitor in Staphylococcus aureus. Future experiments will involve employing the newly developed assay to screen natural product extract libraries for novel quorum sensing inhibitors.

Additional Information

Language: English
Date: 2015
Autoinducing Peptides, Mass Spectrometry, Quorum Sensing, Staphylococcus aureus
Quorum sensing (Microbiology)
Listeria monocytogenes
Staphylococcus aureus
Bacterial diseases $x Treatment
Drug resistance in microorganisms
Virulence (Microbiology) $x Molecular aspects

Email this document to