Middle Ear Irrigations Decrease the Density of Mucosal Biofilms in an Animal Model of Acute Otitis Media

Abstract

Objective: Bacteria in biofilms are extremely resistant to antibiotics. Recurrent acute otitis media appears to be a disease related to biofilm formation. The goal of this study is to determine if middle ear irrigations with saline or baby shampoo could eradicate mucosal biofilms in a chinchilla model of acute otitis media. Method: After a baseline ABR, middle ears of 10 chinchillas were inoculated with Haemophilus influenzae. On day 5, the ears were irrigated with saline or 1% baby shampoo using a syringe or hydrodebrider. A final ABR was obtained before the animals were euthanized and middle ear mucosa were harvested for SEM analysis. Results: Biofilm formation on middle ear mucosa in chinchillas was in nonuniform distribution. SEM analysis by a blinded microscopist showed a statistically significant decrease in biofilm densities of middle ear mucosa after normal saline or 1% baby shampoo irrigations when compared with nonirrigated ears using Wilcoxon/Kruskal-Wallis Tests ( P < .01). No statistically significant difference in biofilm densities between normal saline and 1% baby shampoo irrigations was seen. The hearing thresholds on auditory brainstem responses (ABR) at frequencies 16 kHz, 4 kHz, 1 kHz, and 500 Hz were unchanged two days after normal saline or 1% baby shampoo irrigations. Conclusion: Middle ear irrigations with 1% baby shampoo or normal saline lead to a statistically significant decrease in biofilm densities. One percent baby shampoo or normal saline are non-ototoxic and can be safely used for middle ear irrigations. Future work in our laboratory will study the effect of a hydrodebrider prototype.