Novel isatin-chalcone molecular hybrids endowed with potent antistaphylococcal properties: In vitro and mechanistic...

Antimicrobial resistance (AMR) is the prevailing life-threatening challenge worldwide. Bacteria adopt multiple strategies to overcome the biocidal potential of antibiotics. Persistent infections are mostly related to undesirable treatment outcomes, putting an enormous burden on the healthcare system. This overgrowing issue demands effective treatment alternatives to combat this menace. The present study demonstrates isatin-linked chalcones as an effective antibacterial agent against methicillin-sensitive and -resistant Staphylococcus aureus strains. The identified analogs 1c, 1d, and 1j presented remarkable antibacterial activity with low MIC values and a high safety profile. Further, time-kill kinetics demonstrated bactericidal action in a time-dependent manner. These potent hits provided synergistic potential in combination with vancomycin and rifampicin. Next, ex vivo studies in RAW 264.7 cell lines displayed effective intracellular bactericidal potential, which highlights the therapeutic potential of active hits in clearing intracellular infection. Furthermore, mechanistic insight revealed the antibiofilm nature, presenting the curative nature of the potent hits in treating biofilm-related infections. Microscopic studies visualizing morphological alterations in response to treatment with potent hits revealed membrane-based morphological changes. These outcomes were further validated by experiments such as the membrane integrity and membrane permeabilization study, which emphasized the membrane targeting potential of the hits. Also, it was found that these potent hits were involved in disturbing the bioenergetics of the tested pathogen, which was validated by an ATP quantification assay. Moreover, the potent hits exhibited antibacterial potential against MRSA isolates, assuring curative properties against clinically encountered bacterial pathogens. Overall, our study highlights isatin-linked chalcones as effective treatment options against S. aureus-related deadliest infections.