TDK conference 2020

In companion animal practice, inflammation of the external auditory canal is one of the most common dermatological disorder. In veterinary and human practice alike, the development of suppurative otitis accompanied by perforated tympanic membrane is frequently observed, in which Gram-negative bacteria play a primary role, mainly Pseudomonas aeruginosa. This disorder is often followed by the inflammaton of the middle ear and chronic pathological changes, which can lead to hearing impairment. Microorganisms which are involved in the pathogenesis of otitis are tend to be susceptible to several different antibiotic agents, but not all of them can be applied safely, due to their ototoxic effects. The susceptibility of bacteria can also be affected by the presence of biofilms, which are able to form a protecting barrier around the pathogens which conduct to reduced penetration of the applied antibiotics, therefore increases antimicrobial resistance and clinical failure.

The aim of our study was to examine the ototoxic effect of antimicrobial and antibiofilm agents, that might be suitable for the treatment of otitis externa, also in the case of eardrum perforation without causing any hear loss. These substances are able to break down biofilms produced by bacteria and minimise the odds of the selection of resistant bacterial strains. In the course of our experiment we studied the ototoxicity of different components, notably a fluoroquinolone antibiotic, antibiofilm agents and antibacterial essential oils. We conducted our study in healthy conventional rabbits under general anesthesia utilizing the Otodynamics Otoport ABR device. By the means of the BAER hearing test we stated the integrity of the animals hearing, then in general anesthesia and analgesia a 2mm diameter punch hole was prepared on their eardrum with the help of the endoscope, which was followed by the completion of another hearing test. Thereupon we injected 1 ml per side of the solutions and their combination into the ears of the animals over 5 days. Throughout the study we monitored the onset of incidental irritation. After the last day of the treatment we performed a further hearing test.

Based on the results of our experiment, the antibiotic agent, the antibiofilm additives and the essential oils studied are safe to apply in the case of otitis accompanied by eardrum perforation, as they are not prove to be ototoxic neither independently, nor in combination.