Synergistic Antibacterial Effect of Ethyl Acetate Fraction of Vernonia amygdalina Delile Leaves with Tetracycline against Clinical Isolate Methicillin-Resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa
Multidrug-resistant bacteria have raised global concern about the inability to fight deadly infectious diseases. Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa are the most common resistant bacteria that are causing hospital infections. Te present study was undertaken to investigate the synergistic antibacterial efect of the ethyl acetate fraction of
Vernonia amygdalina Delile leaves (EAFVA) with tetracycline against the clinical isolates MRSA and P. aeruginosa. Microdilution
was used to establish the minimum inhibitory concentration (MIC). A checkerboard assay was conducted for the interaction
efect. Bacteriolysis, staphyloxanthin, and a swarming motility assay were also investigated. EAFVA exhibited antibacterial activity
against MRSA and P. aeruginosa with a MIC value of 125 μg/mL. Tetracycline showed antibacterial activity against MRSA and
P. aeruginosa with MIC values of 15.62 and 31.25 μg/mL, respectively. Te interaction between EAFVA and tetracycline showed
a synergistic efect against MRSA and P. aeruginosa with a Fractional Inhibitory Concentration Index (FICI) of 0.375 and 0.31,
respectively. Te combination of EAFVA and tetracycline induced the alteration of MRSA and P. aeruginosa, leading to cell death.
Moreover, EAFVA also inhibited the quorum sensing system in MRSA and P. aeruginosa. Te results revealed that EAFVA
enhanced the antibacterial activity of tetracycline against MRSA and P. aeruginosa. Tis extract also regulated the quorum sensing
system in the tested bacteria.
