"Identification of curcumin and pyrazole as potential inhibitors of Klebsiella pneumoniae S-ribosylhomocysteinase (LuxS): An integrated computational and experimental approach".

Multidrug-resistant (MDR) Klebsiella pneumoniae (K. pneumoniae) represents a significant global threat to public health. Its ability to form robust biofilms controlled by quorum-sensing (QS) mechanisms and their ability to acquire new virulence factors and resistance mechanisms leads to urgent need for the development of new antimicrobial strategies and discovering novel therapeutic targets like S-ribosylhomocysteinase (LuxS). The enzyme LuxS is critical for autoinducer-2 (AI-2) generation which functions as a main signaling molecule between interspecies and intraspecies communication through QS regulated pathways, thereby making it an excellent target for anti-virulence interventions. The aim of this study was to assess whether combined use of the curcumin, a naturally occurring polyphenol, and the pyrazole bioactive heterocyclic scaffold would have an anti-virulence effect on K. pneumoniae using both in silico and in vitro approaches. The molecular docking experiments revealed that both compounds exhibited high binding affinities and favorable interaction profiles within the active site of LuxS. Antimicrobial susceptibility testing as well as biofilm inhibition trials using fluorescence spectrophotometry and field emission scanning electron microscopy (FESEM) indicated that these compounds exert significant antibacterial activity and biofilm disruption. Checkerboard assay-based combinatorial analysis revealed an additive interaction for curcumin-pyrazole (FICI = 0.53), curcumin-gentamicin (FICI = 0.73) and pyrazole-gentamicin (FICI = 0.93). The targeting of LuxS-mediated QS reduces biofilm production and may limit resistance selection pressure, highlighting curcumin-pyrazole as a promising therapeutic strategy.