Anti-biofilm Bioactivity of Propolis Essential Oil on Multi-resistant Strains of P. aeruginosa, S. aureus and E. coli

Abstract

Several multidrug-resistant bacterial strains use biofilm formation to evade antimicrobial therapies. This study aimed to characterise the anti-biofilm bioactivity of Propolis essential oil against multidrug-resistant strains. A total of ninety (90) strains, including S. aureus (30), E. coli (30), and P. aeruginosa (30), from clinical and food sources, were included in this study. The antibacterial activity of Propolis essential oil and the resistance profile were determined using the Muller Hinton agar diffusion method. The phenotypic detection of biofilms and the anti-biofilm activity of Propolis essential oil were performed using the tube method. In P. aeruginosa and S. aureus, the respective resistance to ceftazidime, cefepime, and imipenem in clinical strains (16.2%; 25.7%; 32.8%) was twice that in food strains (7.3%; 13%; 16.1%). Resistance to aztreonam in clinical (78.1%) and foodborne (16.1%) P. aeruginosa strains was greater than 60%. All clinical (9.4% to 33.7%) and foodborne (8.2% to 31.3%) E. coli strains exhibited virtually the same levels of antibiotic resistance. Propolis essential oil showed bactericidal (E. coli and S. aureus) and bacteriostatic (P. aeruginosa) activity against both foodborne and clinical strains. Median biofilm formation ranged from 0.7 ± 0.3 to 1.2 ± 0.4 (clinical strains) and from 0.7 ± 0.3 to 0.9 ± 0.3 (foodborne strains). The significant reduction in cell adhesion in clinical and foodborne S. aureus and E. coli strains ranged from 32.3% to 84.8% (P < 0.01). A significant increase exceeding 100% (109.3% to 142.7%) (P < 0.01) was observed in foodborne P. aeruginosa with Propolis oil at concentrations between 0.1% and 0.5%. Between 0.1% and 1% Propolis oil, this increase ranged from 94.2% to 98.8% in clinically sourced P. aeruginosa strains. This study demonstrates the potential of Propolis oil in combating bacterial biofilms.