Bacterial biofilms may contribute to persistent cochlear implant infection

Objectives: To determine if bacterial biofilms are present on the surface of extruding or persistently infected cochlear implants. Methods: Scanning electron microscopy was performed on cochlear implants removed from two patients because of recalcitrant infection, two implants removed secondary to device failure, and two devices that had never been implanted. Preparations were examined by experienced microbiologists for the presence of bacterial biofilms. Results: Microorganisms and amorphous extracellular debris were found on the surface of the infected cochlear implants and the implants removed because of device failure. Biofilm formation was deemed definite in one infected device and possible in the other explanted devices. The never-implanted controls demonstrated microbial contamination without exopolymeric matrix, inconsistent with biofilms. Conclusion: Bacterial biofilm formation may play a role in recalcitrant cochlear implant infections. This may have profound implications for the treatment of cochlear implant infections.