An integrative in silico and in vitro synergy of Cinnamomum verum essential oil and cinnamaldehyde with imipenem against extensively drug-resistant Gram-negative bacteria

Acinetobacter baumannii and Klebsiella pneumoniae bacterial pathogens are associated with multidrug-resistant hospital-acquired infections. This study aimed to assess the phytochemical composition, antibacterial efficacy, synergistic interactions, molecular docking, and molecular dynamics of the essential oil Cinnamomum verum (Civ-EO) and its major compound. Cinnamaldehyde was identified as the major component of Civ-EO (70.15%). Disc diffusion and MBC/MIC showed advanced antibacterial activity of Civ-EO against extensively drug-resistant (XDR) strains of Acinetobacter baumannii and Klebsiella pneumoniae. Synergism between Cinn-EO and imipenem was revealed by combined disc diffusion and confirmed by checkerboard assays against all XDR Acinetobacter baumannii and Klebsiella pneumoniae isolates (FICI˂0.5). Cinnamaldehyde displayed important antibacterial effects alone and in combination with imipenem (FICI˂0.5) against all used XDR and susceptible strains. Molecular docking demonstrated the highest interaction between cinnamaldehyde and undecaprenyl pyrophosphate synthase enzymes and D-alanine: D-alanine ligase. According to molecular dynamics simulations, the stabilizing effects of ligand binding on the target enzyme reduce its activity. The current study demonstrates the highly antibacterial effects of cinnamaldehyde in combination with imipenem against XDR Acinetobacter baumannii and Klebsiella pneumoniae, which could constitute an interesting strategy for combating these bacteria.