Antibacterial and Synergistic Effects of Herbal Extracts in Combination with Amikacin and Imipenem Against Multidrug-Resistant Isolates of Acinetobacter

Abstract

Acinetobacter species are defined as multidrug-resistant pathogens and the development of resistance against antimicrobials is a major problem in the treatment of infections caused by them. This study aimed to evaluate the antibacterial activity of aqueous and methanol extracts of Salvia chorassanica and Artemisia khorassanica on multidrug-resistant Acinetobacter isolates and also examining the interaction of the methanol extract of the plants with the combination of amikacin and imipenem. First, the presence of adeI and adeB genes in bacterial isolates was investigated. The aqueous and methanol extracts of the leaves of the plants were prepared by ‏Maceration method. Minimum Inhibition Concentration (MIC) values were determined to evaluate the antibacterial activities of plant extracts and antibiotics. Combined effects of the antibiotics with plant extracts were performed using the checkerboard method. The accumulation assay was used to examine the inhibitory effects of plant extracts on the bacterial efflux pump. MIC results indicated that the methanol extracts were effective against Acinetobacter species. FICI values indicated that the combination of antibiotics with methanol plant extracts improves bacterial sensitivity to antibiotics. The extracts also exhibited efflux pump inhibitory activities. Consequently, combination of the plant extracts with antibiotics could enhance the antibiotic susceptibility of resistant pathogens.