Direct growth control of antibiotic‐resistant bacteria using visible‐light‐responsive novel photoswitchable antibiotics

Abstract

AbstractIn addition to the discovery of new (modified) potent antibiotics to combat antibiotic resistance, there is a critical need to develop novel strategies that would restrict their off‐target effects and unnecessary exposure to bacteria in our body and environment. We report a set of new photoswitchable arylazopyrazole‐modified norfloxacin antibiotics that present a high degree of bidirectional photoisomerization, impressive fatigue resistance and reasonably high cis half‐lives. The irradiated isomers of most compounds were found to exhibit nearly equal or higher antibacterial activity than norfloxacin against Gram‐positive bacteria. Notably, against norfloxacin‐resistant S. aureus bacteria, the visible‐light‐responsive p‐SMe‐substituted derivative showed remarkably high antimicrobial potency (MIC of 0.25 μg/mL) in the irradiated state, while the potency was reduced by 24‐fold in case of its non‐irradiated state. The activity was estimated to be retained for more than 7 hours. This is the first report to demonstrate direct photochemical control of the growth of antibiotic‐resistant bacteria and to show the highest activity difference between irradiated and non‐irradiated states of a photoswitchable antibiotic. Additionally, both isomers were found to be non‐harmful to human cells. Molecular modellings were performed to identify the underlying reason behind the high‐affinity binding of the irradiated isomer to topoisomerase IV enzyme.