In vitro antibacterial properties of Cinnamomum zeylanicum essential oil against clinical extensively drug-resistant bacteria

Abstract Introduction The cinnamon is one of the most popular and the oldest spices used as a traditional herbal medicine. The aim of this study was to determine the antibacterial properties of Cinnamomum zeylanicum bark essential oil (EO) against some extensively drug-resistant (XDR) clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VR E. faecium), Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. Methods A total of 150 XDR isolates, which includes 30 MRSA, 30 VR E. faecium, 30 A. baumannii, 30 P. aeruginosa, and 30 E. coli were collected from different clinical samples. The XDR isolates were defined as resistance to ≥1 antibiotic in all but ≤2 classes using disc diffusion method. Antibacterial efficacy of cinnamon EO was performed by the agar disc diffusion and microdilution broth methods. Results In total, all studied XDR isolates were sensitive against C. zeylanicum EO. The most sensitive isolate was MRSA, followed by VR E. faecium, E. coli, P. aeruginosa, and A. baumannii. The MIC value ranges were as follows: MRSA 0.15–1.25 μl/mL, VR E. faecium 0.15–2.5 μl/mL, E. coli and P. aeruginosa 0.15−5 μl/mL, and A. baumannii 0.31−10 μl/mL. The MIC50, MIC90, MBC50, and MBC90 values of C. zeylanicum EO was 1.25 μl/mL, 5 μl/mL, 2.5 μl/mL, and 5 μl/mL, respectively. Conclusions The potent antibacterial effects of C. zeylanicum EO may be encouraging for further in vivo investigations of this essential oil to determine its effective ingredients for the synthesis of a new antimicrobial agent for treatment of human pathogens, particularly drug-resistant bacteria.