Synergistic antimicrobial action of trans-cinnamaldehyde with last resort antibiotics against Escherichia coli

Abstract

Antibiotic resistance emergence in bacterial pathogens is a global issue and to control it, government enforce strict drug usage regulations and researchers trying to search new antibiotics and explore the paradigm of combinational therapy with other antimicrobials and herbal drugs. Trans-cinnamaldehyde (TC) is the main component of cinnamon oil, which has antimicrobial properties and used as herbal medicine. The present investigation was carried out to explore the interaction of TC with few last resort antibiotic drugs for its synergistic potential. The antibiotic resistance pattern of selected antibiotics against E. coli was also determined to access the level of antimicrobial resistance among different species of animals. A total 430 isolates of Escherichia coli were tested for antibiotic resistance and their MICs were calculated. Checkerboard assay and FICIs were used to determine the synergy between TC and imipenem. Resistant was observed in 20.9%, 3.25%, 8.13%, 5.81% and 9.06% to colistin (CL), imipenem (IPM), nitrofurantoin (F/M), polymixin B (PB) and TC, respectively in E. coli isolates (430), while all isolates were sensitive for tigecycline (TGC). Further, 80 E. coli isolates revealed synergy between TC and any of the five selected antibiotics. TC showed synergistic antimicrobial effect with IPM in 72 E. coli isolates, with CL in 39 isolates, and with F/M in 28 isolates. While no synergistic action was observed with TGC and PB. Present work showed the potential of synergistic effect of the TC with antibiotics in combating the antibiotic resistance by combinational therapy.