Imaging studies of bacterial biofilms on cochlear implants-Bioactive glass (BAG) inhibits mature biofilm.

Lisa Kirchhoff,Joerg Steinmann,Timon Hussain,Diana Arweiler-Harbeck,Ralph Bertram,Judith Arnolds,Benedikt Höing,Stefan Hansen,Stephan Lang,Jan Buer,Amitava Mukherjee

doi:10.1371/journal.pone.0229198

Lisa Kirchhoff, Joerg Steinmann + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0229198

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Abstract

The capability of Pseudomonas aeruginosa and Staphylococcus aureus to form biofilm on varying CI component materials differs in the presence and absence of bioactive glass (BAG). The application of BAG induces significant changes in biofilm morphology which can be visualized via scanning electron microscopy (SEM). Bacterial biofilm formation on medical devices, such as cochlear implants (CI), can lead to chronic infections. Interestingly, BAG of type S53P4 seems to be a promising tool for use in the reduction of biofilm development. Primarily, four bacterial species known to cause implant-related infections, P.aeruginosa (ATCC9027), S. aureus (ATCC6538), Staphylococcus epidermidis (ATCC12228) and Streptococcus pyogenes (ATCC19615) were analyzed regarding their capacity to form biofilm on CI components manufactured from three kinds of material: silicone, platinum and titanium. Subsequently, P. aeruginosa and S. aureus biofilms were visualized using scanning electron microscopy, comparing BAG-treated biofilm with non-treated biofilm. The four bacterial species presented biofilm-forming capabilities in a species and surface dependent manner. Metal CI components allowed for the greatest proliferation of biofilm. S. aureus and P. aeruginosa showed the highest rate of biofilm formation on polystyrene surfaces. For both species, SEM revealed altered biofilm morphology after treatment of S53P4 BAG. This study indicates that bacterial biofilm formation and structure on CI components is dependent on the surface composition, altering between metal and silicone surfaces. After application of BAG, changes in biofilm morphology on CI components were observed. These data highlight the impact of BAG on bacterial biofilm morphology.

Highlights

In cochlear implants (CIs), sound is transduced via an externally located microphone to internal parts of the implant, which are located under the temporal skin
This study indicates that bacterial biofilm formation and structure on CI components is dependent on the surface composition, altering between metal and silicone surfaces
Four different bacterial species were used for the evaluation of biofilm formation on CI components: S. pyogenes (ATCC 19615), P. aeruginosa (ATCC 9027), S. aureus (ATCC 6538) and S. epidermidis (ATCC 12228)

Summary

Introduction

In cochlear implants (CIs), sound is transduced via an externally located microphone to internal parts of the implant, which are located under the temporal skin. Imaging of bacterial biofilms on CIs electrode located in the cochlea directly stimulates the hair cells in the organ of Corti in a frequency-dependent manner [1] Implanting exogenous material such as prostheses or technical devices in a human body is often associated with complications such as perioperative infections. Microorganisms are embedded in an extracellular matrix (ECM), leading to resistance against immune cells and antibiotic therapy [4,5] These biomaterial-associated infections are frequently caused by staphylococci (Staphylococcus aureus and Staphylococcus epidermidis), by streptococci, e.g. Streptococcus pyogenes as well as by Gram-negative bacteria such as Pseudomonas aeruginosa [6]. The aim of this investigation was to identify the surface-specific bacterial preferences and to understand biology, morphology and potential surface—bacteria interactions of a biofilm forming matrix on implant materials, leading eventually to the development of clinical tools to reduce the risk of peri- and postoperative infections.

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