Cinnamaldehyde: A plant-derived antimicrobial for overcoming multidrug-resistant Acinetobacter baumannii infection

Multidrug resistant (MDR) -Acinetobacter baumannii has emerged as a nosocomial pathogen that is difficult to treat. The aim of this study was to investigate the efficacy of cinnamaldehyde against MDR- A. baumannii , and its potential in combination with other antibiotics. The effects of cinnamaldehyde on MDR- A. baumannii were assessed using antimicrobial susceptibility test, time-kill kinetic assay, and checkerboard assay. The post-antibiotic effect (PAE), a pharmacodynamics parameter, was also determined. Scanning electron microscopy was used to study the morphological changes in MDR- A. baumannii . Cinnamaldehyde exerted potent antibacterial activity against all clinical MDR- A. baumannii isolates in a dose-dependent manner. This compound exhibited additional effects when used in combination with all the tested antibiotics for most isolates. With the exception of colistin and imipenem, the synergistic effects were observed in some isolates. Cinnamaldehyde in combination with other antibiotics had no adverse effects on the sensitivity of MDR- A. baumannii to all the tested antibiotics. In terms of the time interval for drug administration, the mean PAE values of cinnamaldehyde were lower than those of colistin but higher than those of aminoglycosides and carbapenems. Interestingly, the bacterial cells continuously elongated, and cell separation was disrupted after treatment with cinnamaldehyde. This is the first direct report on the effect of cinnamaldehyde on clinically isolated MDR- A. baumannii . The efficacy of cinnamaldehyde was demonstrated by its minimum inhibitory concentration values and additional effects with some synergism when applied with other antibiotics. Cinnamaldehyde is a plant-derived antimicrobial compound that can be an alternative to control infectious diseases.