Antibacterial activities of ethanol extracts of Philippine medicinal plants against multidrug-resistant bacteria

Objective: To investigate the antibacterial activities of crude ethanol extracts of 12 Philippine medicinal plants. Methods: Crude ethanol extracts from 12 Philippine medicinal plants were evaluated for their antibacterial activity against methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, extended spectrum β-lactamase-producing, carbapenem-resistant Enterobacteriaceae and metallo-β-lactamase-producing Pseudomonas aeruginosa and Acinetobacter baumannii. Results: The leaf extracts of Psidium guajava, Phyllanthus niruri, Ehretia microphylla and Piper betle (P. betle) showed antibacterial activity against the Gram-positive methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. P. betle showed the highest antibacterial activity for these bacteria in the disk diffusion (16–33 mm inhibition diameter), minimum inhibitory concentration (19–156 μg/mL) and minimum bactericidal concentration (312 μg/mL) assays. P. betle leaf extracts only showed remarkable antibacterial activity for all the Gram-negative multidrug-resistant bacteria (extended spectrum β-lactamase-producing, carbapenem-resistant Enterobacteriaceae and metallo-β-lactamase-producing) in the disk diffusion (17–21 mm inhibition diameter), minimum inhibitory concentration (312–625 μg/mL) and minimum bactericidal concentration (312–625 μg/mL) assays. Conclusions: P. betle had the greatest potential value against both Gram-negative and Gram-positive multidrug-resistant bacteria. Favorable antagonistic activities were also exhibited by the ethanol extracts of Psidium guajava, Phyllanthus niruri and Ehretia microphylla