Interactive Antimicrobial Profiles of Astragalus membranaceus (Fisch.) Bunge Extracts and Conventional Antibiotics against Pathogenic and Non-pathogenic Gastrointestinal Bacteria

Abstract

Background: The aim of this project was to investigate the efficacy of Astragalus membranaceus (Astragalus) extracts, alone and in combination with conventional antibiotics, against diarrhoea-and dysentery-causing pathogens, as well as against non-pathogenic gastrointestinal bacterial strains. The study sought to validate the chemotherapeutic potential of a traditional Chinese medicinal plant and to identify combinational therapies with increased efficacy compared to either the extracts or conventional antibiotics alone. Methods: Astragalus root powder was extracted with solvents of varying polarity and screened for inhibition of bacterial growth. Susceptibility was assessed by disc diffusion techniques, whilst the minimum inhibitory concentrations (MICs) were quantified by liquid dilution assays. To screen for combinatorial effects, the Astragalus root extracts were combined with a range of conventional antibiotics and tested against each bacterial strain using liquid dilution assays. ΣFIC values were determined and used to determine the class of interaction. Results: Aqueous Astragalus root extracts did not significantly inhibit the growth of the non-pathogenic or beneficial gut microflora bacteria E. cloacae, E. coli or E. faecalis, but possessed mild inhibitory activity against pathogenic A. faecalis, A. hydrophila, B. cereus, S. newport and S. sonnei bacteria. Combinations of the Astragalus extracts and conventional antibiotics generally produced additive or indifferent interactions, indicating that they are safe to use concomitantly without compromising the efficacy of either component. Two cases of antagonistic combinations were detected against B. cereus and S. sonnei. Conclusion: Mild inhibition of 5 pathogenic bacteria occurred with aqueous Astragalus extracts, with a number of additive and antagonistic interactions arising when tested in combination with conventional antibiotics. Astragalus may be used safely in the presence of normal gut bacteria and in most combinations with conventional antibiotics.

Astragalus (Astragalus membranaceus Bunge): botanical, geographical, and historical aspects to pharmaceutical components and beneficial role

“…The antiviral activity of A. membranaceus against influenza virus was shown in infected mouse Raw 264.7 cells by influencing the cell proliferating cycle, and by affecting the TLR3 signaling pathway, by reducing the malondialdehyde level, and increasing the superoxide dismutase level (Liang et al 2019). Antibacterial activity of the aqueous Astragalus extract was demonstrated, as this could mildly inhibit bacterial responsible by dysentery and diarrhea while not affecting normal gut bacteria (Lai et al 2018).…”

Astragalus species: Insights on its chemical composition toward pharmacological applications

“…‐ Antimicrobial activity against Bacillus coagulans (isoflavane glycoside from the ethanol extract, root) (Wang, Han, Dai, Wang, & Ao, 2014), Bacillus dysenteriae (lecitin extract) (Bai et al, 2018), B. subtilis (ethanol powder extract, bacteriostatic) (Arjoon, Saylor, & May, 2012), Campylobacter spp. (ethanol and methanol extracts) (Balachandar, Jagadeeswari, & Dhanabalan, 2012), E. coli (ethanol, lecitin and methanol extracts) (Bai et al, 2018; Lai, Cock, & Cheesman, 2018), Mycoplasma mycoides (ethanol powder extract, bactericidal) (Arjoon et al, 2012), Salmonella enteritidis , Shigella spp. (ethanol and methanol extracts) (Balachandar et al, 2012) including Shigella sonnei (weak activity, aqueous extracts) (Lai et al, 2018), S. aureus (lecitin extract) (Bai et al, 2018), Alcaligenes faecalis , Aeromonas hydrophila , B. cereus , Salmonella newport (Lai et al, 2018), and against clinical multidrug‐resistant isolates of E. coli , MRSA, methicillin‐resistant S. epidermidis (MRSE), and P. aeruginosa , and their respective susceptible reference strains (silver nanoparticles of water‐soluble polysaccharides isolated from the root extract) (Ma et al, 2017).…”

“…(ethanol and methanol extracts) (Balachandar, Jagadeeswari, & Dhanabalan, 2012), E. coli (ethanol, lecitin and methanol extracts) (Bai et al, 2018; Lai, Cock, & Cheesman, 2018), Mycoplasma mycoides (ethanol powder extract, bactericidal) (Arjoon et al, 2012), Salmonella enteritidis , Shigella spp. (ethanol and methanol extracts) (Balachandar et al, 2012) including Shigella sonnei (weak activity, aqueous extracts) (Lai et al, 2018), S. aureus (lecitin extract) (Bai et al, 2018), Alcaligenes faecalis , Aeromonas hydrophila , B. cereus , Salmonella newport (Lai et al, 2018), and against clinical multidrug‐resistant isolates of E. coli , MRSA, methicillin‐resistant S. epidermidis (MRSE), and P. aeruginosa , and their respective susceptible reference strains (silver nanoparticles of water‐soluble polysaccharides isolated from the root extract) (Ma et al, 2017). Combinations of the aqueous extracts and conventional antibiotics (including chloramphenicol, ciprofloxacin, erythromycin, penicillin G, and tetracycline) were either synergistic or indifferent (Lai et al, 2018).…”

“…-Antiviral activity of astragaloside IV isolated from Radix Astragali against hepatitis B Virus (Wang, Li, et al, 2009) and adenovirus (Shang et al, 2011), of aqueous and methanol (root) extracts against avian (Arjoon et al, 2012;Bai et al, 2018;Balachandar et al, 2012;Fu et al, 2014;Han et al, 2017;J. Huang et al, 2019;Khan et al, 2019;Lai et al, 2018;Ma et al, 2017;Shang et al, 2011;Wang et al, 2014;Wang, Li, et al, 2009) T A B L E 4 (Continued)…”