Structural features of tympanostomy tube biofilm formation in ciprofloxacin-resistant Pseudomonas otorrhea

SummaryObjectiveBacterial biofilm formation has been implicated in the high rate of persistent otorrhea after tympanostomy tube insertion. In this study, we evaluated Pseudomonal biofilm formation from intractable post tympanostomy tube otorrhea in children.Materials and methodsTwelve patients (seven males, five females) with unilateral post tympanostomy tube P. aeruginosa otorrhea were evaluated prospectively. All patients were treated with ciprofloxacin otic drops but the otorrhea failed to resolve. Ear discharge for culture was collected from the external auditory canal using a swab. The tympanostomy tubes were removed and collected for evaluation of biofilm formation using a scanning electron microscopy.ResultsIn all cases, ciprofloxacin-resistant P. aeruginosa was the only organism grown. The surface of the silicone tube contained undulations or microfissures throughout. The thick biofilms present on most tube surfaces were densities with no intervening spaces, consistent with biofilms.ConclusionBiofilms can be directly observed by scanning electron microscopy. Therefore, our results demonstrate that bacterial aggregates called biofilms, that are resistant to treatment by antibiotics, can be detected by standard culture techniques, and may play a major etiologic role in posttympanostomy otorrhea.