Anti-Biofilm Action of Cineole and <i>Hypericum perforatum</i> to Combat Pneumonia-Causing Drug-Resistant <i>P. aeruginosa</i>

Hospital-acquired antibiotic-resistant pneumonia is one of the major causes of mortality around the world that pose a catastrophic threat. <i>Pseudomonas aeruginosa</i> is one of the most significant opportunistic pathogens responsible for hospital-acquired pneumonia and gained resistance to the majority of conventional antibiotics. There is an urgent need for antibiotic alternatives to control drug-resistant pneumonia and other related respiratory infections. In the present study, we explored the antibacterial potential of cineole in combination with homeopathic medicines against biofilm-forming drug-resistant <i>P. aeruginosa</i>. Out of 26 selected and screened homeopathic medicines, <i>Hypericum Perforatum</i> (HyPer) was found to eradicate biofilm-forming drug-resistant <i>P. aeruginosa</i> most effectively when used in combination with cineole. Interestingly, the synergistic action of HyPer and cineole was also found to be similarly effective against planktonic cells of <i>P. aeruginosa</i>. Further, the potential synergistic killing mechanisms of cineole and HyPer were determined by analyzing zeta membrane potential, outer membrane permeability, and DNA release from <i>P. aeruginosa</i> cells upon treatment with cineole and HyPer. Additionally, molecular docking analysis revealed strong binding affinities of hypericin (an active ingredient of HyPer) with the PqsA (a quorum sensing protein) of <i>P. aeruginosa</i>. Overall, our findings revealed the potential synergistic action of cineole and HyPer against biofilm-forming drug-resistant <i>P. aeruginosa</i>. Cineole and HyPer could be used in combination with other bronchodilators as inhalers to control the biofilm-forming drug-resistant <i>P. aeruginosa</i>.