Development of LpxC Inhibitors Based on the Mechanism of Action of Colistin in Acinetobacter baumannii

Area of Science:

• Microbiology
• Drug Discovery
• Biochemistry

Background:

• Multidrug-resistant (MDR) *Acinetobacter baumannii* poses a significant clinical challenge due to limited treatment options, primarily relying on polymyxins like colistin.
• Current antibiotic discovery efforts targeting the lipopolysaccharide (LPS) biosynthetic pathway often utilize enzyme-based assays that may not accurately reflect cellular physiology.
• Developing new therapeutic strategies against MDR Gram-negative bacteria is crucial.

Purpose of the Study:

• To develop a novel cell-based screening strategy for identifying inhibitors of LPS biogenesis in *A. baumannii*.
• To discover new chemical scaffolds effective against MDR *A. baumannii* by targeting LPS synthesis.
• To establish a phenotypic platform linking colistin resistance to inhibition of lipooligosaccharide (LOS) synthesis.

Main Methods:

• A phenotypic screening platform was established using colistin to identify compounds that restore bacterial growth by inhibiting LOS synthesis.
• A library of approximately 7000 small molecules was screened to find non-hydroxamate compounds that alleviate colistin-induced growth inhibition.
• Hit compounds were validated using LpxC enzyme assays, protein-compound binding assays, and molecular docking studies.

Main Results:

• A novel cell-based screening strategy was successfully developed, linking colistin resistance to inhibition of LOS biogenesis in *A. baumannii*.
• Screening identified non-hydroxamate compounds that restore bacterial growth under colistin stress, indicating inhibition of essential LPS enzymes like LpxC.
• Molecular docking suggested that the identified hit compounds bind to the LpxC catalytic pocket in a manner similar to known inhibitors.

Conclusions:

• The developed phenotypic screening strategy offers a new approach for discovering LPS-targeted inhibitors.
• The study provides novel chemical scaffolds with potential for developing new antibiotics against *A. baumannii* and other Gram-negative pathogens.
• This work highlights the utility of cell-based assays for identifying inhibitors of essential bacterial pathways.