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Updated: Jul 13, 2026
Trans-Tympanic Drug Delivery for the Treatment of Ototoxicity
Published on: March 16, 2018
Effect of ototopical medications on tympanostomy tube biofilms
K Scott Oxley1, John G Thomas, Hassan H Ramadan
1Department of Otolaryngology-Head and Neck Surgery, West Virginia University, Morgantown, West Virginia, USA.
Objective:
Examine how ototopical medications affect biofilms on fluoroplastic tympanostomy tubes.
Study Design:
In vitro comparison of different ototopical medications against a clinical isolate of Pseudomonas aeruginosa biofilm on tympanostomy tubes treated for 5, 10, 14, and 21 days.
Methods:
Under sterile conditions 21 tympanostomy tubes were cut in half. These were attached to pegs of two Calgary Biofilm Devices via rubber cement. Device 1 evaluated microbial growth as colony forming units (CFUs). Device 2 evaluated presence of biofilms. Tubes were prepped for biofilm growth, incubated, and stressed for 72 hours. Afterward, one tube per device was removed and forcefully washed. One was sonificated for 5 minutes, serially diluted, and plated for CFUs. Formalin preserved the other for biofilm evaluation by scanning electron microscopy. Next, tubes were exposed to five drops of Ciprofloxacin, Ciprofloxacin/Dexamethasone, Dexamethasone, Ofloxacin, or saline for 1 hour. Afterward, the ototopicals were removed and sterile broth was placed in the wells as a nutrient. This was repeated every 12 hours for 5, 10, 14, and 21 days of treatment. Prior to the last dose of treatment intervals, a streak plate was performed to evaluate for microbial growth in the wells. The tubes were evaluated for CFUs and biofilms at each interval as previously described.
Results:
Microbial activity in CFUs decreased by day 5 and continued through day 21 for the antibiotic containing drops. Despite treatment, the biofilm was never eradicated and continued to progress.
Conclusions:
Infectivity of the biofilm is neutralized by antibiotic ototopicals; however, the biofilm will progress despite treatment.
Insights
Antibiotic ototopical medications reduce microbial activity in Pseudomonas aeruginosa biofilms on tympanostomy tubes. However, these biofilms continue to progress despite treatment, indicating incomplete eradication.
Area of Science:
- Otolaryngology
- Microbiology
- Biomaterials Science
Background:
- Tympanostomy tubes are prone to biofilm formation, often caused by Pseudomonas aeruginosa.
- Biofilms on medical devices can lead to persistent infections and treatment challenges.
Purpose of the Study:
- To investigate the in vitro efficacy of various ototopical medications against Pseudomonas aeruginosa biofilms on tympanostomy tubes.
- To assess the impact of antibiotic-containing ototopicals on biofilm progression over time.
Main Methods:
- An in vitro model using fluoroplastic tympanostomy tubes and a clinical isolate of Pseudomonas aeruginosa was established.
- Tubes were treated with Ciprofloxacin, Ciprofloxacin/Dexamethasone, Dexamethasone, Ofloxacin, or saline for up to 21 days.
- Microbial growth (CFUs) and biofilm presence were evaluated using scanning electron microscopy and culture methods at multiple time points.
Main Results:
- Antibiotic-containing ototopicals significantly reduced microbial activity (CFUs) starting from day 5 through day 21.
- Despite reductions in microbial load, complete eradication of the biofilm was not achieved.
- Biofilm progression was observed throughout the treatment duration, even with antibiotic intervention.
Conclusions:
- Antibiotic ototopical medications can neutralize the infectivity of Pseudomonas aeruginosa biofilms.
- The physical structure of the biofilm persists and progresses despite topical antibiotic treatment.
- Further strategies may be needed to fully eradicate biofilms on tympanostomy tubes.
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