In vivo resistance to bacterial biofilm formation on tympanostomy tubes asa function of tube material

Adherent bacterial biofilms have been implicated in the irreversible contam ination of implanted medical devices. We evaluated the resistance of variou s tympanostomy (pressure equalization (PE)) tube materials to biofilm forma tion using an in vivo model. PE tubes of silicone, silver oxide-impregnated silicone, fluoroplastic, silver oxide-impregnated fluoroplastic, and ion-b ombarded silicone were inserted into the tympanic membranes of 18 Hartley g uinea pigs. Staphylococcus aureus was than inoculated into the middle ears. An additional 8 guinea pigs were used as controls; the PE tubes were inser ted without middle ear inoculation. All PE tubes were removed on day 10 and analyzed for bacterial contamination using culture, immunofluorescence, an d scanning electron microscopy (SEM). All infected ears developed otitis me dia with otorrhea, but none of the animal control ears drained. Fluorescenc e imaging of the animal control tubes showed large cellular components cons istent with inflammation. The infected tubes showed heavy DNA fluorescence consistent with bacteria and inflammatory cells. All animal control tubes e xcept the ion-bombarded silicone tubes showed adherent inflammatory firm on SEM. Also, all tubes placed in infected ears except the ion-bombarded sili cone tubes showed adherent bacterial and inflammatory films on SEM. Nonadhe rent surface properties such as the ion-bombarded silicone may be helpful i n preventing chronic PE tube contamination.