Biofilm formation in cochlear implants with cochlear drug delivery channels in an in vitro model

Dual Drug Delivery in Cochlear Implants: In Vivo Study of Dexamethasone Combined with Diclofenac or Immunophilin Inhibitor MM284 in Guinea Pigs

Cochlear implants are well established to treat severe hearing impairments. Despite many different approaches to reduce the formation of connective tissue after electrode insertion and to keep electrical impedances low, results are not yet satisfying. Therefore, the aim of the current study was to combine the incorporation of 5% dexamethasone in the silicone body of the electrode array with an additional polymeric coating releasing diclofenac or the immunophilin inhibitor MM284, some anti-inflammatory substances not yet tested in the inner ear. Guinea pigs were implanted for four weeks and hearing thresholds were determined before implantation and after the observation time. Impedances were monitored over time and, finally, connective tissue and the survival of spiral ganglion neurons (SGNs) were quantified. Impedances increased in all groups to a similar extent but this increase was delayed in the groups with an additional release of diclofenac or MM284. Using Poly-L-lactide (PLLA)-coated electrodes, the damage caused during insertion was much higher than without the coating. Only in these groups, connective tissue could extend to the apex of the cochlea. Despite this, numbers of SGNs were only reduced in PLLA and PLLA plus diclofenac groups. Even though the polymeric coating was not flexible enough, MM284 seems to especially have potential for further evaluation in connection with cochlear implantation.

Intracochlear drug delivery in combination with cochlear implants : Current aspects

Local drug application to the inner ear offers a number of advantages over systemic delivery. Local drug therapy currently encompasses extracochlear administration (i. e., through intratympanic injection), intracochlear administration (particularly for gene and stem cell therapy), as well as various combinations with auditory neurosensory prostheses, either evaluated in preclinical or clinical studies, or off-label. To improve rehabilitation with cochlear implants (CI), one focus is the development of drug-releasing electrode carriers, e. g., for delivery of glucocorticosteroids, antiapoptotic substances, or neurotrophins to the inner ear. The performance of cochlear implants may thus be improved by protecting neuronal structures from insertion trauma, reducing fibrosis in the inner ear, and by stimulating growth of neuronal structures in the direction of the electrodes. Controlled drug release after extracochlear or intracochlear application in conjunction with a CI can also be achieved by use of a biocompatible, resorbable controlled-release drug-delivery system. Two case reports for intracochlear controlled release drug delivery in combination with cochlear implants are presented. In order to treat progressive reduction in speech discrimination and increased impedance, two cochlear implant patients successfully underwent intracochlear placement of a biocompatible, resorbable drug-delivery system for controlled release of dexamethasone. The drug levels reached in inner ear fluids after different types of local drug application strategies can be calculated using a computer model. The intracochlear drug concentrations calculated in this way were compared for different dexamethasone application strategies.

Developments in delivery of medications for inner ear disease

INTRODUCTION

Hearing loss, tinnitus and balance disturbance represent common diseases that have tremendous impact on quality of life. Despite the high incidence of inner ear disease in the general population, there are currently no dedicated pharmacologic interventions available to treat these problems.

AREAS COVERED

This review will focus on how treatment of inner ear disease is moving toward local delivery at the end organ level. The authors will discuss current practice, ongoing clinical trials and potential areas of development such as hair cell regeneration and neurotrophin therapy.

EXPERT OPINION

The inner ear is accessible through the middle ear via the oval and round windows allowing diffusion of drugs into the perilymph. With a better understanding of the physiology of the inner ear and the underlying molecular causes of inner ear disease there is great potential for the development of novel therapeutics that can be locally administered. At present, there is a rapid development of drugs to target diverse inner ear diseases that cause sensorineural hearing loss and balance dysfunction.

Novel rat model of methicillin-resistant Staphylococcus aureus-infected silicone breast implants: a study of biofilm pathogenesis

BACKGROUND

Clinical infection of breast implants occurs in 7 to 24 percent of breast reconstructions. It may persist over time in the form of biofilm without overt manifestation and is extremely difficult to eradicate. The authors' aim was to establish a novel model for biofilm infection of silicone breast implants in rats.

METHODS

Fifty-six rats underwent implantation of miniature silicone breast implants and/or methicillin-resistant Staphylococcus aureus (MRSA) bacteria. Group A received implants covered with MRSA biofilm. Group B received implants and free planktonic MRSA. Group C received free planktonic MRSA without implants. A control group received sterile implants without MRSA. Each group was divided to receive either saline or vancomycin injections between days 4 and 11. Clinical evaluation, bacterial counts, and scanning electron microscopy were performed.

RESULTS

The mortality rate in group B (implants infected with free planktonic MRSA) was significantly higher than that in all other groups [37 percent versus groups A and D (0 percent) and group C (7 percent)]. Treatment with vancomycin lowered temperature in groups B and C (p < 0.05) and improved wound healing in group B (p < 0.01). Vancomycin treatment reduced wound bacterial counts in free planktonic MRSA groups B and C but had no significant effect on biofilm MRSA-infected group A.

CONCLUSIONS

The model successfully induced persistent breast implant infection. Free planktonic MRSA produced in situ biofilm on silicone implants. Biofilm infection has milder manifestations than free planktonic MRSA infection, which has higher rates of systemic infections and death when compared with either isolated biofilm infection or free planktonic MRSA infection without implant. Vancomycin has limited effect against mature biofilm.

Revision cochlear implantation in children

Revision cochlear implant (RCI) surgery has become an important tool for the management of cochlear implantation complications. This review encompasses both common and uncommon indications of RCI, diagnostic and management considerations, outcomes, surgical principles, and emerging applications. In summary, early identification of complications and suboptimal device performance is imperative for children who are in critical periods of communicative development. Independent of indications, most RCI achieve a successful restoration of sound. Although rare, it is prudent to discuss the potential complications of revision surgery and their implications with patients and their families.

Pseudomonas biofilm formation after Haemophilus infection

OBJECTIVES

Tympanostomy tube (TT) biofilm formation may lead to refractory otorrhea and occlusion. Biofilms are commonly composed of multiple microbial species. One species may promote or inhibit biofilm formation by other species.The aim of this study was to determine if Haemophilus influenzae(HI) promotes the development of Pseudomonas aeruginosa(PA) biofilm on TTs.

STUDY DESIGN

Controlled, in vitro.

SETTING

Academic research laboratory.

SUBJECTS AND METHODS

Fluoroplastic TTs (20 per group) were exposed to plasma, allowed to dry, and cultured with HI for 7 days. TTs were either gas sterilized or treated for 24 hours with 10 or 3000 μg/mL ciprofloxacin. Half of the TTs from each treatment group underwent bacterial counts or scanning electron microscopy. The remainder, as well as TTs not exposed to HI, were cultured with PA for 4 days and treated with gentamicin to kill planktonic PA. Biofilm formation was quantified with bacterial counts.

RESULTS

TTs treated with ciprofloxacin 3000 μg/mL had lower HI counts than TTs treated with 10 μg/mL (P = .0001), but viable HI persisted. PA biofilm formation on TTs with prior HI biofilm and treated with ciprofloxacin 10 μg/mL or gas sterilization was not different than TTs without HI. Less PA biofilm formed on TTs with HI treated with 3 mg/mL ciprofloxacin(P = .002).

CONCLUSIONS

HI biofilm does not promote PA biofilm formation on TTs. Use of high-dose ototopical therapy to clear HI may reduce subsequent PA biofilm formation.

Corticosteroid-releasing cochlear implant: a novel hybrid of biomaterial and drug delivery system

In this study, drug-eluting cochlear implant (CI) electrodes were prepared, and the amount of drug released was determined. Dexamethasone (DEX) (0.25-2% w/w, the weight percent of the final cured polymer) was used as a bioactive agent to suppress postsurgical inflammations upon mixing with a two-part nonrestricted pourable medical-grade silicone elastomer. Batch reproducibility analysis was performed on three consecutive batches. Drug release experiments were accomplished in normal saline medium, where DEX was analyzed via a validated HPLC method. The drug loading percentage and the device surface area were the most dominant parameters explored to monitor the drug release behavior from CI coatings. Total cumulative amount of DEX released from various loaded samples was in the order of 2 > 1 > 0.5 > 0.35 > 0.25% w/w, but the cumulative percentage of drug released showed a reverse order. The DEX dosages between 0.1 and 1 microg were released from samples of smallest to highest loadings during the initial 24 h, and dosages <1-5 microg were released from similar samples of various loadings at the first patency 2 weeks. The extent of crosslinking was only effective on release profile at lower drug loadings of 0.25% w/w relative to 0.5%. It was also found that release profile was not affected by postcuring. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010.

Localized cell and drug delivery for auditory prostheses

Localized cell and drug delivery to the cochlea and central auditory pathway can improve the safety and performance of implanted auditory prostheses (APs). While generally successful, these devices have a number of limitations and adverse effects including limited tonal and dynamic ranges, channel interactions, unwanted stimulation of non-auditory nerves, immune rejection, and infections including meningitis. Many of these limitations are associated with the tissue reactions to implanted auditory prosthetic devices and the gradual degeneration of the auditory system following deafness. Strategies to reduce the insertion trauma, degeneration of target neurons, fibrous and bony tissue encapsulation, and immune activation can improve the viability of tissue required for AP function as well as improve the resolution of stimulation for reduced channel interaction and improved place-pitch and level discrimination. Many pharmaceutical compounds have been identified that promote the viability of auditory tissue and prevent inflammation and infection. Cell delivery and gene therapy have provided promising results for treating hearing loss and reversing degeneration. Currently, many clinical and experimental methods can produce extremely localized and sustained drug delivery to address AP limitations. These methods provide better control over drug concentrations while eliminating the adverse effects of systemic delivery. Many of these drug delivery techniques can be integrated into modern auditory prosthetic devices to optimize the tissue response to the implanted device and reduce the risk of infection or rejection. Together, these methods and pharmaceutical agents can be used to optimize the tissue-device interface for improved AP safety and effectiveness.

The role of biofilms in otolaryngologic infections: update 2007

PURPOSE OF REVIEW

Biofilms have been shown to play a role in otitis media, sinusitis, cholesteatoma, tonsillitis, adenoiditis, and device infections. This article is written to review recent advances in the field.

RECENT FINDINGS

The role of biofilms in the persistence of chronic, mucosal-based ENT-related infections was first recognized in otitis media. Definitive proof was lacking until the demonstration of bacterial biofilms on the middle-ear mucosa of children, not only with chronic otitis media with effusion, but also with recurrent otitis media. Strains of Pseudomonas aeruginosa isolated from cholesteatoma are avid biofilm formers. Biofilms have been reported in the adenoids of children with chronic rhinosinusitis, helping to explain the clinical observation that adenoidectomy can be beneficial to children with chronic otitis or chronic rhinosinusiti. Additional studies have confirmed the presence of biofilms in chronic tonsillitis. Biofilms have also been shown to be involved in infected cochlear implants and tracheotomy tubes.

SUMMARY

The recognition that chronic otolaryngologic bacterial infections are biofilm related has been the impetus for the development of new technologies for the study of biofilms and their prevention and treatment. Understanding that chronic bacterial infections are biofilm related is fundamental to developing rationale strategies for treatment and prevention.