Evaluation of Phytochemicals and Synergistic Interaction Between Plant Extracts and Antibiotics for Efflux Pump Inhibitory Activity Against Salmonella Enterica Serovar Typhimurium Strains

Abstract

Objective: Traditional antibiotics are increasingly suffering from the emergence of efflux related multidrug resistance (MDR) amongst pathogenic bacteria that led to novel approaches to control microbial infections being investigated as potential alternative treatments. Synergism between natural sources and antibiotics has received much attention and efforts have been put in to identify compounds that can act as efflux pump inhibitors. Methods:Methanol and ethyl acetate extracts of important medicinal plant species widely used in traditional remedies for various ailments were screened for their synergism with ciprofloxacin and tetracycline antibiotics using the agar well diffusion method. Phytochemical analysis was also done by standard methods. In addition, to evaluate the potential of synergistic extracts as efflux pump inhibitors against Salmonella enterica serovar Typhimurium (S. Typhimurium) strains, including wild-type (NKS70), overexpressed AcrAB (NKS773) as well as against knockout TolC (NKS174), berberine uptake and ethidium bromide inhibition assays were done. Results:In vitro synergistic activity were confirmed for methanolic extracts of all five plants, namely, Allium sativum (Amaryllidaceae), Syzygium aromaticum (Myrtaceae), Berberis aristata (Berberidaceae), Rhus cotinus (Anacardiaceae), and Phyllanthus emblica (Phyllanthaceae). Agar well diffusion method confirmed the greatest synergistic activity of P. emblica with used antibiotics. The phytochemical analysis of medicinal plants showed that the terpenoids and reducing sugar were found to be present in all synergistic extracts. Phytochemicals have great potential as antimicrobial agents. Further efflux inhibition assays confirmed maximum efflux pump inhibition through Phyllanthus emblica extract against S. Typhimurium when extracted with methanol solvent. Conclusion:It is hypothesized that phyto compounds present in these plants might be following the same mechanism of action responsible for synergistic interaction as well as efflux inhibition. These data provide bioactive compounds for possible clinical utility as efflux inhibitors.

Total Phenolic Content and Free Radical Scavenging Activity of Representative Medicinal Plants of Thailand

“…have been reported for its antioxidant, antipyretic, antimicrobial, anticancer, anti-inflammatory, immunomodulatory, hypolipidemic, and hepatoprotective properties [20][21][22][23][24][25][26][27]. The methanolic extract of P. emblica has been reported for the bacterial efflux pump inhibiting activity [28]. The aqueous extract of P. emblica exhibited the antidepressant activity at higher doses in mice [29].…”

Berberine Hydrochloride Could Prove to Be a Promising Bullet Against Clostridium Difficile Infection: A Preliminary Study From South India

“…The combination therapy of antibiotics with phytochemicals derived from plants maybe promising in the management of the multidrug-resistant enteric pathogens as evidenced from published literature [28]. Extensive studies are, therefore, warranted for proper characterization of the natural compounds to explore their therapeutic/chemical effects in the host, which in turn will enhance patient care through the production of safe and effective drugs [29].…”

Enteric Fever in Travelers: An Updated Insight

“…Also, methanolic extract of gyrocarpus asiaticus willd showed an effect in reducing the salmonella species [42]. A combination of plant extracts which includes Allium sativum (Amaryllidaceae), Szygium aromaticum (Myrtaceae), Berberis aristata (berberidace), Rhus cotinus (Anacardiaceae) and phyllanthus emblica (Phyllanthaceae) also showed a positive effect in restricting Salmonella species [43].…”