Antibacterial activity and synergistic interaction between Artemisia roxburghiana Wall. ex Besser extracts and synthetic antibiotics against resistant clinical isolates

Abstract

Antimicrobial resistance has imposed a huge challenge by complicating the treatment with existing antibiotics, so searching for novel sources to combat antibacterial resistance is crucial. Therefore, the current study was designed to explore Artemisia roxburghiana Wall. ex Besser as a possible solution to reform antimicrobial resistance. Leaf and stem n-hexane (nH), ethyl acetate (EA), methanol (M), and distilled water (DW) extracts were prepared by successive solvent extraction using ultrasonication-assisted maceration. Chromogenic assays estimated phenolic and flavonoid content along with antioxidant capacitance. Therapeutically significant polyphenols were quantified by reverse-phase high-pressure liquid chromatography (RP-HPLC). Preliminary resistance screening of antibiotics and antibacterial activity of the extracts was executed by disc diffusion and microbroth dilution methods. The checkerboard method, time-kill kinetics, and protein content determination validated the synergistic activity of extracts. Results showed maximum percentage yield in stem DW extract (7.705 %), and highest phenolic and flavonoid content in leaf EA extract with values of 67.47 ± 1.39 and 64.68 ± 1.09 μg gallic acid and quercetin equivalent/ mg extract respectively. Stem DW and M showed the highest antioxidant power and reducing potential with values of 129.34 ± 1.49 and 135.25 ± 0.02 μg ascorbic acid equivalent/ mg extract respectively. Noteworthy quantities of syringic acid (0.539 ± 0.035–16.557±0.38 µg/mg), plumbogen (11.330 ± 0.12 µg/mg) and emodin (0.103 ± 0.002–1.373 ± 0.023 µg/mg) were assessed in extracts through RP-HPLC. Primary profiling of antibiotics revealed resistance of pathogens towards cefixime. Synergistic studies showed total and partial synergy between extracts and clinical isolates. Moreover, a potentiation in the susceptibility of cefixime (2-8-fold reduction in concentration) was observed in time-kill kinetic studies. There was a significant decline in bacterial growth and protein content when treated in combinations at fractional inhibitory concentration index (FICI) compared to cefixime/extracts alone treated isolates. This research has appraised A. roxburghiana as a potential novel candidate for combating bacterial resistance.