ANALYZING THE MODE OF ACTION OF CARBAZOLES AS POTENTAL ANTIBIOTICS FOR MULTI-DRUG RESISTANT TUBERCULOSIS

TB Alliance discovered 1,302 compounds that inhibited growth of TB and XDR-TB, the Keiler Lab further analyzed them to see if any of them specifically targeted trans-translation. Sixteen showed to target trans-translation; one of them being KKL-896. It is unknown exactly how KKL-896 inhibits growth of M. tuberculosis, specifically within the trans-translation pathway. In an attempt to define the mode of action for KKL-896, resistant mutants were isolated using drug pressure. The genomic sequences of these resistant mutants were then collected and analyzed to compare to that of E. coli ∆tolC. There were three specific genes of interest, mdtO, ybhF, and ybiH. mdtO encodes for the MdtO efflux pump, ybiH encodes for the YbiH efflux pump, and ybhF regulates the YbiH efflux pump. E. coli ∆tolC cells were obtained and single gene deletions were carried out to determine if an individual gene or a combination potentially lead to the observed resistance to KKL-896 in the mutants. With the knowledge of KKL-896’s target, the mode of action for how the compound works in the cell will also be discovered. Understanding every aspect of how KKL-896 interacts with M. tuberculosis cells is vital for drug development to advance in order to combat XDR-TB. Antibiotics resistance is an ever-growing issue in today’s world. In 2017, the CDC estimated that one-fourth of the world’s population has been infected with Tuberculosis (TB), many antibiotic resistant. TB Alliance, a non-profit organization, has discovered many compounds known to inhibit growth of Mycobacterium tuberculosis cells to help fight the TB epidemic. The Keiler Lab has teamed up with TB Alliance to help in the fight. The Keiler Lab has discovered a novel pathway, trans-translation, which has many promises in the antibiotic field since it is only found in bacteria. The Keiler Lab ran a high-throughput screen of TB Alliance’s compounds and discovered that sixteen compounds, one being KKL-896, did in fact inhibit trans-translation. KKL-896 is classified as a carbazole due to the fact that it has a benzene ring on either side of a five-membered nitrogen ring. Not much else is known, therefore numerous assays were run to understand its various characteristics and modes of action within the bacterial cell. The minimum concentration of KKL-896 needed to inhibit growth of E. coli ∆tolC was found to be 3 μM. Inhibitory profiles showed that there is a lag phase of growth when E. coli ∆tolC is in the presence of high concentrations of KKL-896. KKL-896 was also tested in combination with other antibiotics and compounds. Lastly, resistant mutants to KKL-896 were isolated in hopes of determining KKL-896’s molecular target. It was found that ybiH, a DNA-binding transcription regulator, was responsible for the survival of the mutants at high concentrations of KKL-896. KKL-896’s target is still unknown; however, with knowledge of how KKL-896 acts within the bacterial cell, drug development to advance. Prior to any antibiotic being put onto the market, it is vital to understand any effects, positive and negative, that it may have on a patient. Once the specific mechanism in which KKL-896 inhibits growth of MDR-TB is understood, it may ultimately lead to a new antibiotic to treat TB that is resistant to those currently being used today.

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Work Title ANALYZING THE MODE OF ACTION OF CARBAZOLES AS POTENTAL ANTIBIOTICS FOR MULTI-DRUG RESISTANT TUBERCULOSIS
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Creators
  1. Isabel L Hunsberger
Keyword
  1. antibiotic resistance
  2. Keiler
  3. tuberculosis
  4. trans-translation
License Attribution 4.0 International (CC BY 4.0)
Work Type Research Paper
Publication Date 9 November 2019
Deposited November 09, 2019

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