DISCUSSION:
It is uncommon for cochlear implants to be complicated by microbial infection. However, when infections occur, sometimes it can be difficult to treat with antibiotic therapy, and may require explanting the cochlear implant.3 there are studies demonstrating that infection of cochlear implants is due to biofilm formation.
The biofilms act as reservoirs, capable of releasing individual bacteria into the surrounding tissue, thereby causing recurrent episodes of infection which may persist, despite intensive antimicrobial therapy, until the device is removed. In addition, as the role of biofilm formation in human infections becomes more clearly defined, cochlear implant surgeons should be prepared to deal with the unique demands of biofilm-related infection as they arise.4
Till date there are no straightforward guidelines to deal with biofilm infection and no standardized treatment to salvage the implant.
We made our protocol regarding the management of biofilm (Figure 4 ). No form of debridement or cleansing is likely to remove all biofilm and it still has the potential to regrow and form a layer again within days. The novel technique of using surfactant properties of polyhexanide and surfactant component (Betaine) reduces surface tension and aids in the removal of debris and bacteria. Applying the gel on the bed and flap cover prevents the regrowth of biofilm. We now routinely give a wash of the antimicrobial solution before taking sutures.7
Common microorganisms isolated and reported are Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa.5, 6, 7
We suspected biofilms in our patients due to the recurrence of infections, despite antibiotic therapy. Macroscopically, rubbery, poorly vascularized granulomatous tissue is the hallmark of such infections.8 Their growth rate and sharing of antibiotic resistance genes within the bacteria makes them refractory to most aggressive antibiotic regimens. They can be demonstrated on the device surface using scanning electron microscopy.9 To the best of our knowledge no other study has reported an in vitro/in vivo use of polyhexanide for cochlear implant infections. An antibacterial effective amount of polyhexanide is adsorbed on the surface of titanium alloy and it is eligible method for preventing implant associated pseudomonas aeruginosa, staphylococcus aureus and staphylococcus epidermidis.10
In our Indian setup there are financial difficulties in obtaining new implant devices and the patient gets into auditory deprivation which is a matter of concern Our first aim was to salvage the functioning implant so the financial burden would be lesser than getting a new device.
In a study, 1 percent tea tree oil failed to eradicate biofilm growth at one hour; 5 percent tea tree oil proved sufficient to completely eradicate the biofilm formed by the cochlear implant Methicillin-sensitive S aureus isolate.4 However, there are other organisms being isolated from biofilms and polyhexanide can work against them.5, 6
In a study it is said that early explantation is necessary for wound healing 3 however, we had to explant one implant for wound healing after reinfection with biofilm. Infection with pseudomonas and late presentation could be the reason for explantation.
After extensive search of literature, we found Polyhexanide and Betaine are safe to use for the management of biofilm infection in implants made of titanium alloy. This suggested that it is safe to use in biofilms in cochlear implants. 7, 10