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