Efficiency of clove essential oil against planktonic cells and biofilms of Malassezia pachydermatis isolated from canine dermatitis

This study investigated the ability of clove oil and eugenol to inhibit biofilm production and eradicate canine Malassezia pachydermatis in biofilm form. Biofilm formation was studied using a crystal violet assay and was quantified by optical density (OD) at 595 nm. Killing time was assessed by time-kill assay. All 17 isolates of canine M. pachydermatis were capable of biofilm formation, however, 6 isolates formed more extensive biofilms than the other isolates and were selected for susceptibility testing. Clove essential oil and eugenol showed effectiveness against both planktonic and biofilm cells with identical minimum planktonic inhibitory concentration (MPIC50) and minimum planktonic fungicidal concentration (MPFC50), 0.156 and 0.312 mg/ml, respectively. The minimum biofilm inhibitory concentration (MBIC50) and the minimum biofilm eradication concentration (MBEC50) were 0.312 and 0.625 mg/ml, respectively. These studies indicate that biofilms of M. pachydermatis are more resistant to clove essential oil and eugenol. In addition, eugenol is the component of clove essential oil responsible for its antifungal activity. The results of the time-kill study showed that the antimicrobial activity of clove essential oil was time and concentration-dependent.