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Updated: Jun 15, 2026
A High-throughput Shigella-specific Bactericidal Assay
Published on: February 27, 2019
High-throughput screening of the virulence regulator VirF: a novel antibacterial target for shigellosis
Julie K Hurt1, Thomas J McQuade, Anthony Emanuele
1Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109-1065, USA.
Abstract:
Shigella flexneri is a human enteropathogen that infects about 165 million people and claims more than 1 million lives per year worldwide. Although shigellosis has been considered a disease of the "Third World," like many other contagious diseases, it does occur in developed countries. The emergence of drug and multidrug-resistant strains of Shigella emphasizes the need for novel antibiotic development. VirF, an AraC-type transcriptional regulator, is responsible for the expression of all downstream virulence factors that control intracellular invasion and cell-to-cell spread of Shigella. Gene knockout studies have validated that inhibition of VirF expression is sufficient to block the normal life cycle of Shigella in the host and thereby increase susceptibility to the host immune system. The authors have developed a high-throughput, cell-based assay to monitor inhibition of VirF using beta-galactosidase as a reporter protein. Using an avirulent strain of Shigella, they have screened libraries containing approximately 42,000 small molecules. Following confirmation and dose-response analysis, they have identified 7 compounds that demonstrate VirF inhibition in vivo >or=55% in comparison with the controls and little general antibacterial activity (measured by cell growth, OD(600)). The authors are in the process of confirming these "hits" in several secondary assays to assess the mechanism of action.
Insights
Researchers screened 42,000 compounds to find new ways to fight Shigella flexneri. They identified 7 compounds that inhibit VirF, a key virulence regulator, offering potential for novel antibiotic development against drug-resistant strains.
Area of Science:
- Microbiology
- Infectious Diseases
- Drug Discovery
Background:
- Shigella flexneri causes significant global mortality, with increasing drug resistance necessitating new treatments.
- VirF, an AraC-type transcriptional regulator, is crucial for Shigella's virulence, controlling invasion and cell spread.
- Inhibiting VirF can disrupt Shigella's life cycle and enhance host immune response.
Purpose of the Study:
- To develop a high-throughput screening assay to identify inhibitors of VirF.
- To discover novel small molecules that target VirF and exhibit potential as new antibiotics against Shigella.
Main Methods:
- A cell-based assay using beta-galactosidase as a reporter was developed to monitor VirF inhibition.
- Approximately 42,000 small molecules were screened using an avirulent Shigella strain.
- Hit compounds underwent confirmation and dose-response analysis for VirF inhibition and general antibacterial activity.
Main Results:
- Seven compounds were identified that demonstrated significant VirF inhibition (>=55%) in vivo.
- The identified compounds exhibited minimal general antibacterial activity, suggesting targeted action.
- These "hits" are undergoing secondary assays to elucidate their mechanism of action.
Conclusions:
- The study successfully identified novel small molecules targeting VirF, a critical Shigella virulence factor.
- These compounds represent promising leads for developing new therapeutics against multidrug-resistant Shigella infections.
- Further validation is required to confirm their therapeutic potential and mechanism of action.
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