Antibacterial and anti-biofilm activity of plumbagin against multi-drug resistant clinical bacterial isolates

Objectives: To evaluate the antibacterial activity of plumbagin (PGN) against multidrug resistance (MDR) clinical isolates. Methods: This study was carried out at the Department of Clinical Lab Sciences, King Khalid University from October 6, 2021 to December 14, 2021. We investigated the antibacterial and anti-virulence activity of PGN against MDR Gramnegative (Escherichia coli, Klebsiella pneumoniae, Salmonella Typhi, and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus [S. aureus], Staphylococcus saprophyticus [S. saprophyticus], Streptococcus pyogenes, and Enterococcus faecalis) clinical bacterial isolates. Agar well diffusion, microdilution assay, colony count method, biofilm formation, and time-kill kinetics were employed to probe the MIC, MBC, and anti-virulence activity of PGN. Results: Plumbagin inhibited the growth of all tested isolates, with S. saprophyticus exhibiting the highest sensitivity. MIC values ranged from 0.029 to 0.117 mu g/mL whereas MBC ranged from 0.235 to 0.94 mu g/mL, with 79% to 99% growth inhibition. Moreover, all tested isolates showed a marked decrease in biofilm formation, with S. saprophyticus and S. aureus being the most sensitive. Conclusion: Plumbagin is a stand-alone, broad spectrum antibacterial with promising potential against the rising threat of antimicrobial resistance.