Phytochemical Profiling and Antibiofilm Efficacy of Myrtus communis Extract Against Multidrug-Resistant Pathogens: A Sustainable Biotherapeutic Approach Aligned with Circular Economy Principles

Abstract

The increasing prevalence of multidrug-resistant (MDR) bacteria and their ability to form persistent biofilms represent major challenges in the treatment of chronic and recurrent infections, highlighting the need for effective natural antimicrobial agents. This study evaluated the phytochemical composition and antibacterial and antibiofilm activities of methanolic leaf extract of Myrtus communis against clinical MDR isolates of Staphylococcus aureus and Klebsiella pneumoniae. The extract was prepared by maceration with methanol and characterized using gas chromatography–mass spectrometry (GC–MS). Antibacterial activity was assessed using agar well diffusion and resazurin-based broth microdilution assays to determine the minimum inhibitory concentration (MIC). Biofilm formation and inhibition were evaluated using the crystal violet microplate assay. GC–MS analysis identified 35 phytochemical compounds, with tert-butylhydroquinone (26.34%), a hypoxanthine-related compound (10.10%), and 5-hydroxymethylfurfural (8.76%) as major constituents. The extract demonstrated antibacterial activity against both MDR isolates, with S. aureus showing greater susceptibility (MIC 3.125 mg/mL) than K. pneumoniae (MIC 6.25 mg/mL). Both isolates exhibited strong biofilm formation before treatment. Following exposure to the extract, biofilm biomass decreased significantly from 0.1290 ± 0.0026 to 0.0287 ± 0.0015 in S. aureus (P = 0.0002) and from 0.1287 ± 0.0091 to 0.0293 ± 0.0038 in K. pneumoniae (P = 0.0027). These findings demonstrate that M. communis possesses considerable antibacterial and antibiofilm activities against clinically relevant MDR bacteria, supporting its potential as a natural source for developing alternative antimicrobial strategies.