Antimicrobial Properties of Cinnamon Essential Oil on Salmonella Typhimurium

Abstract

Essential oils have a wide range of properties due to various chemical compounds in their composition. Potential applications have been identified in areas such as food preservation, natural alternatives to antibiotics, and disease prevention and treatments. More specifically, the antimicrobial properties of cinnamon (Cinnamomum sp.) oil have been established against foodborne bacteria, but the effectiveness has not yet been defined at various concentrations under standardized conditions. Therefore, the main objective of this study was to evaluate the effect of cinnamon essential oil on Salmonella enterica ser. Typhimurium (Salmonella Typhimurium) using the disc diffusion procedure.The Salmonella Typhimurium (ATCC® 53648™) inoculum was prepared by growing the bacteria in tryptic soy broth for 24 hours at 37°C, yielding 6.9 × 108 CFU/ml. One hundred microliters of the starting bacterial culture were spread onto Mueller Hinton agar plates and left to dry for 15 minutes. Treatments were formed by creating cinnamon essential oil solutions (EO) of 0, 0.5, 1, 2 and 4% using 70% ethyl alcohol as the diluent. Each EO was vortexed and filtered using a 0.2 microliter sterile syringe filter. Twenty microliters of each EO was pipetted into a sterile paper disc (weight ranged of 0.0086–0.009g) and left to dry for one hour. Five paper discs of each treatment containing the EO were placed on standardized locations on each inoculated plate in duplicate. The plates were then incubated at 37°C for 24 hours. Additionally, three manufactured standard antibiotic paper discs of 5 mcg Ciprofloxacin, 10 mcg Ampicillin, and 10 mcg Streptomycin were placed on separate plates in duplicate as controls. The zone of inhibition created by each EO or antibiotic was measured using a calibrated digital caliper. All data were analyzed using the general linear model procedure for analysis of variance (ANOVA).The antimicrobial property of the EO observed as the zone of inhibition increased as the concentration of the EO increased (R= 0.884, P < 0.0001). EO at 4% showed the greatest antimicrobial effect against Salmonella Typhimurium compared to 2.0, 1.0, and 0.5% (10.5, 6.0, 4.2 and 4.6 mm, respectively; P < 0.0001). There was no significant difference (P=0.4) between the zone of inhibition of 0.5% and 1% EO. However, 2% EO showed a significantly larger zone of inhibition than 0.5% and 1% EO (P<0.01). The 2% EO concentration showed a greater zone of inhibition against Salmonella than ampicillin and streptomycin treatments (6.0 versus 4.7 and 3.4 mm respectively; P< 0.0001). All antibiotics had some effect against Salmonella where ciprofloxacin had the greatest effect; its effect was even greater than the 4% EO (14.0 vs. 10.5 mm, P< 0.0001).In conclusion, cinnamon EO showed increasing antimicrobial properties against Salmonella Typhimurium as the concentration of oil increased. It proved to be more effective than two of the antibiotic controls as low as 2% concentration. Further evaluation of the effects of cinnamon EO is needed to determine the extent of its effectiveness against additional foodborne pathogens.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.