evaluation of enoyl-ACP reductase II (FabK) Inhibition by phenylimidazole unveils a promising narrow-spectrum antimicrobial strategy.

infection (CDI) is a leading cause of hospital-acquired diarrhea, which often stem from disruption of the gut microbiota by broad-spectrum antibiotics. The increasing prevalence of antibiotic-resistant strains, combined with disappointing clinical trials results for recent antibiotic candidates, underscore the urgent need for novel CDI antibiotics. To this end, we investigated enoyl ACP reductase (FabK), a crucial enzyme in fatty acid synthesis, as a drug target for microbiome-sparing antibiotics. To test this concept, we evaluated the efficacy and spectrum of activity of the phenylimidazole analog 296, which is validated to inhibit intracellular FabK. Against major CDI-associated ribotypes 296 had an MIC of 2 μg/ml, which was comparable to vancomycin (1 μg/ml), a standard of care antibiotic. In addition, 296 achieved high colonic concentrations and displayed dosed-dependent efficacy in mice with colitis CDI. Mice that were given 296 retained colonization resistance to and had microbiomes that resembled the untreated mice. Conversely, both vancomycin and fidaxomicin induced significant changes to mice microbiomes, in a manner consistent with prior reports. FabK therefore represents a potential target for microbiome-sparing CDI antibiotics, with phenylimidazoles providing a good chemical starting point for designing such agents.