Potential Effects of Selected Plant Extracts on Multidrug Resistant Bacteria

Due to rapid development of microbial resistance against chemotherapeutic agents, mostly antibiotics, it has become essential currently to screen effective, safe, cheap, and available therapeutics from various medicinal plants for their potential antimicrobial effect. In this study, we aimed to evaluate antimicrobial potential of leaf extracts of three medicinal plants- Ocimum tenuiflorum, Terminalia arjuna and Camellia sinensis on 8 drug-resistant bacteria (Klebsiella pneumonia, Enterobacter hormaechei, Strenotrophomonas maltiphilia, Bacillus anthracis, Aeromonas hydrophila, Shewanella seohaensis Comamonas aquatica, Aeromonas Veronii. Antibacterial activity of leaf extracts was calculated based on the minimum inhibitory concentration using Mueller–Hinton broth in a disc diffusion method following CLSI guidelines. Between the plants, O. tenuiflorum displayed a broad spectrum of inhibitory zones varying from 8 mm to 21.83 mm against eight bacterial isolates where the maximum ZOI were observed against K. pneumonia (21.67 ±1.63 mm) followed by B. anthracis (20.17 ±2.15 mm) and E. hormaechei (19.16 ±2.15 mm). The extracts were then subjected to qualitative phytochemical screening through HPLC to determine the potential flavonoids present in the extracts. We used 16 secondary metabolites as standard compounds and identified eight potential flavonoids from both extracts which have antimicrobial properties. Among them, (-) Epicatechin and Myricetin were found in both extracts. Syringic acid, Rutin hydrate and p-Coumaric acid were present in O. tenuiflorum and trans-ferulic acid, quercetin and kaempferol were present in T. arjuna. Further, molecular docking analysis revealed the strongest binding interactions (-9.9 kcal/mol) between Rutin hydrate & one of the bacterial key protein OmpK35 porin proteins. The findings of the present work indicates that O. tenuiflorum has the potential to be developed as antibacterial agent, especially against multidrug-resistant bacteria. However, further in vivo & in vitro research on extracted compounds and discovery of the mode of their action are still needed to shed light on the effects.

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