Antibacterial and Antibiotic-Potentiation Activities of Levisticum officinale L. Extracts on Pathogenic Bacteria

Background Multidrug resistant (MDR) Gram-negative bacteria have resistance to many antimicrobial compounds by multiple mechanisms including reduced outer membrane permeability, and active efflux mechanisms by efflux pumps. Objectives The current study was planned to search the antibacterial activities of the ethanol and chloroform extracts of Levisticum officinale L., and their synergistic effects with ciprofloxacin against some Gram-negative pathogenic bacteria; also to analyze the extracts if they contain inhibitors of efflux pumps of the examined bacteria. Materials and Methods After grinding, the resulting powder of Levisticum officinale L. was extracted with 85% ethanol and chloroform by maceration method. The studied microorganisms included the reference strains of Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli and Salmonella enteritidis. Broth micro-dilution methods were used to determine the minimum inhibitory concentrations (MICs) of the extracts alone or in association with ciprofloxacin and phenylalanine-arginine-β-naphtylamide (PAβN) as an efflux pump inhibitor (EPI). The presumptive efflux activity was detected by the ethidium bromide (EB) well diffusion method. Results MIC determination indicated that the Levisticum officinale L. extracts inhibited the growth of all the studied bacteria within a concentration range of 3125 to 25000 μg/mL. The synergistic effects were noted between the Levisticum officinale L. extracts and ciprofloxacin on all tested bacteria. In S. enertidis and E. coli both extracts of L. officinale, but in P. aeruginosa and A. baumannii only ethanolic extract increased the amount of EB accumulation (i e, reduced efflux). Conclusion The overall results of the current study provided information for the possible use of the Levisticum officinale L. extracts to control bacterial infections caused by the examined bacteria.