In Vitro Activity of Farnesol against Malassezia pachydermatis Isolates from Otitis Externa Cases in Dogs

Chronic otitis externa of dogs is a significant problem due to the prevalence and complexity of the treatment of such animals. There is evidence that in 60–80% of cases of infectious diseases microorganisms located in the biofilm phenotype play the main role. Microorganisms in the biofilm phenotype have a number of advantages, the most significant of which is considered to be increased resistance to various external factors. Among them, a special place is occupied by resistance to antibiotics. In recent decades, research has been conducted at an increasing scale on the role of biofilm infections in various pathologies in veterinary medicine. The etiology and therapy of dog otitis externa caused by Malassezia pachydermatis biofilm has not been fully studied. This is why we consider relevant the scientific and practical aspects of research on the etiology and therapy of dog otitis externa from the position of biofilm infection. In this work, it has been statistically proven that there is a relationship between the optical density of Malassezia pachydermatis biofilms and their sensitivity to drugs, and this relationship is statistically significant. In addition, we have demonstrated that Farnesol has a good antibiofilm effect at a concentration of more 1.6 μM/mL (24% OD decrease of biofilm), and its highest antibiofilm effect (71–55%—more than a half) was observed at a concentration of 200–12.5 μM/mL.