Antimicrobial effects of cinnamon essential oil and cinnamaldehyde combined with EDTA against canine otitis externa pathogens

Abstract

Aims The antimicrobial activity of cinnamon essential oil and cinnamaldehyde against bacterial and fungal pathogens associated with canine otitis externa, as well as the effect of their combination with EDTA were investigated. Methods and Results Antimicrobial susceptibility testing was performed using the broth microdilution method while spot‐plating technique was used to determine their bactericidal activity. Time‐kill kinetics and checkerboard assays were performed to confirm the bactericidal activity and combination effects of the compounds. Cinnamon oil and cinnamaldehyde exhibited antimicrobial activity against Gram‐positive and Gram‐negative pathogens, as well as Malassezia pachydermatis. Synergistic interaction was shown when EDTA (672 μg ml−1) was combined with cinnamon oil (41 μg ml−1) and cinnamaldehyde (22 μg ml−1) against Pseudomonas aeruginosa. Cinnamaldehyde exhibited significantly stronger antimicrobial activity than cinnamon bark oil. Conclusions Cinnamon essential oil and cinnamaldehyde, either used alone or in combination with EDTA, were effective against the causative micro‐organisms of canine otitis externa. The data suggest that cinnamaldehyde could be a promising antimicrobial agent against canine otitis externa. Significance and Impact of the Study This study shows that cinnamon essential oil and cinnamaldehyde, especially the latter, could be used in combination with EDTA as novel treatment for sensitive and resistant bacterial and fungal pathogens involved in canine otitis externa.

Antimicrobial Activity of Essential Oils against Staphylococcus and Malassezia Strains Isolated from Canine Dermatitis

“…Another interesting feature is the high sensitivity of Malassezia to C. zeylanicum. These results are in agreement with findings reported by Bismarck et al [52] and Sim et al [56] in otologic canine isolates. This EO, in fact, although poorly effective against molds such as A. fumigatus [49] and dermatophytes [55], showed a strong antimicrobial activity versus Salmonella enterica serotype Typhimurium and Escherichia coli isolated from poultry [50].…”

Antifungal in vitro Activity of Essential Oils against Clinical Isolates of <b><i>Malassezia pachydermatis</i></b> from Canine Ears: A Report from a Practice Laboratory

“…Clary sage oil in a 10% solution exhibited no antifungal activity in microdilution in the study by Pistelli [35] nor tested with disc diffusion in our study. Cinnamon EO was effective against 20 M. pachydermatis isolates from canine otitis externa tested by microdilution [36]. MIC values of 0.008% indicate strong activity, which is in accordance with the antifungal activity of the 20% solution of this EO in our study.…”

“…The used study design is adapted to routine diagnostics and thus might not always keep up with university research procedures. Nevertheless, aromatograms were performed in duplicate, which is comparable to other published studies [36][37][38]. In addition, a higher effort was made to gain better insight into the efficacy of EOs by testing EO dilutions as well as performing the vapour assay, which is not part of daily routine.…”

“…Thus, another positive effect of EOs in treatment could be their additional antibacterial effect. This was already shown in vitro against several bacterial veterinary isolates [34,36,48,65,66]. In addition, EOs can exhibit anti-inflammatory potential [67], which might be another positive attribute for treatment of otitis externa.…”

“…For example, the activity of 12 EOs against 1 reference strain of M. pachydermatis, but also other pathogens, is described [34]. The activity of 11 EOs against 5 clinical isolates and 1 reference strain of M. pachydermatis or the activity of cinnamon oil against 20 M. pachydermatis isolates from canine otitis was analysed [35,36]. Eighteen M. pachydermatis isolates from healthy canine ears and 1 reference strain were screened against 14 EOs [37].…”