Antibiofilm and anti-quorum properties of ethanolic leaf extracts of Syzygium jambos and Psidium guajava and their gel formulation for wound healing applications

Most bacterial species today have evolved with time and gained resistance to a wide range of antibiotics, primarily due to formation of biofilms and ?lactamases. Many phytochemicals have been explored for their ability to inhibit bacterial biofilms. The present study sheds light on antibiofilm properties of two such plants viz. Psidium guajava and Syzygium jambos, of the Myrtaceae family. They were found to be effective against four different biofilm forming pathogens - Chromobacterium violaceum, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. Synergistic use of the plant extracts showed slightly better antibacterial activity than a single extract. Quorum sensing being one of the key factors required for biofilm formation, the isolate Chromobacterium violaceum was used as the indicator organism to study the anti-quorum properties of the plant extracts. At 10 mg/mL, ethanolic extract of S. jambos inhibited violacein pigment the most (78.84%) and therefore can be considered as a quorum sensing inhibitor (QSI). Since silver nanoparticles (AgNPs) have become increasingly significant in the field of drug delivery, they may be utilized to coat implants to avoid subsequent infections in patients who have had implant surgery and to reduce biofilm development in pathogens. In the present study, five gels were formulated using plant extracts and AgNPs, of which two showed promising results in wound healing assay. The non-toxic nature of the synthesized gels has been verified by studies on L-929 mouse fibroblast cell lines, which opens the door for their prospective application as topical treatments to accelerate the healing process in both acute and chronic wounds. Given that S. aureus and P. aeruginosa are the most commonly isolated bacteria from diabetic foot ulcers, the resulting gels can considerably curb the spread of infection and gangrene and thus prevent amputation.