Implant-associated infections are a serious and cost-intensive clinical problem because antibiotic therapies alone are usually not successful. In most cases, a combined surgical (implant exchange) and antimicrobial approach (long, combined antibiotic therapies) are necessary. For the patient, this means a considerable reduction in quality of life due to pain, prolonged treatments, and restricted mobility. The therapy causes high costs due to long hospital stays, change operations, and care measures. The Working Group is concerned with new strategies for the prevention/retardation of biofilm formation on implants, as well as the validation of test methods. The focus is on the exchange of experiences of practitioners on the influence of the manifold parameters in the biological testing of the antimicrobial effect of materials.
Biofilm formation is a ubiquitous phenomenon that we encounter every day in the kitchen and bathroom. Through hygiene, we are used to successfully keeping this phenomenon in check. However, experience teaches us that this is not always successful and that biofilms occur not only in food but also on a wide variety of materials. This is a completely natural process, as bacteria that are found individually (planktonic) in water, for example, require a biofilm to multiply. Different stages are distinguished in their formation. First, the bacteria bind to the surface of the material, but this is reversible. In the second stage, the binding is irreversible. An extracellular matrix is formed, the bacteria are immobile, further bacteria accumulate, they multiply until a mature biofilm is formed, from which bacteria detach and in turn spread in a planktonic state. A major problem with implant materials is that bacteria inside a biofilm can hardly be reached by antibiotics. The conclusion is that, if possible, control of the biofilm takes place in the first two stages, i.e., for example, the material properties hinder the irreversible binding of the bacteria.
Now, it must be taken into account that - for evolutionary reasons - bacteria have or develop adaptation strategies to ultimately bind to any material surface. On the other hand, the growth of tissue, a cellular biofilm so to speak, is desirable in implants. From a materials science point of view, the aim is therefore to retard the formation of a bacterial biofilm as far as possible so that tissue formation takes place on the implant and the body's mechanisms prevent the formation of biofilms. In this context, reproducible quantitative testing of efficacy is a major challenge.
For example, the working group has shown in an interlaboratory study with identical samples and identical bacterial strains that uniform results were not achieved at different laboratories despite compliance with the specifications of the test method according to ISO 22196 (C. Wiegand et. al: Critical physiological factors influencing the outcome of antimicrobial testing according to ISO 22196 / JIS Z 2801, PLOS ONE, DOI: 10.1371/journal.pone.0194339.
The focus of the Working Group is therefore the practice-oriented exchange of experience in characterizing and evaluating the antimicrobial properties of biomaterials. This includes, in particular, the assessment of a wide variety of parameters in biological testing, the performance of further interlaboratory tests, and the development of standardized test methods.
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