DksA inhibitors against intracellular and persistent Salmonella are effective in acute models of infection.

We are in dire need of antibiotics endowed with new mechanisms of action. The DksA protein regulates the transcription of genes involved in metabolism, translation, and virulence in Gram-negative bacteria. DksA is evolutionarily conserved among Gram-negative pathogens but is absent in humans. Here, we identified a conserved acidic pocket at the tip of the coiled-coil domain of DksA that is amenable for drug development. Our bioinformatics and experimental approaches identified N-(3,4-dimethoxyphenyl)-1H-1,2,4-triazole-3-carboxamide as a DksA inhibitor with moderate antimicrobial activity. Derivatization of the dimethoxyphenyl functionality and aliphatic linker of N-(3,4-dimethoxyphenyl)-1H-1,2,4-triazole-3-carboxamide generated several new chemical entities with excellent IC50 values against DksA-regulated in vitro transcription and improved antimicrobial activity against Salmonella and several other Gram-negative bacteria. Our pharmacokinetic and pharmacodynamic evaluations indicate that the N-(4-phenylbutyl)-1H-1,2,4-triazole-3-carboxamide analog is absorbed in the gastrointestinal tract of rats and is distributed into viscera. The systemic administration of the N-(4-phenylbutyl)-1H-1,2,4-triazole-3-carboxamide analog protected mice against oral and systemic Salmonella infections while practically preventing the formation of microabscesses and necrotic foci in Salmonella-infected mice. Our investigations have identified a previously unknown class of antibiotics against the transcriptional regulator DksA that is endowed with antimicrobial activity against Gram-negative pathogens.