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Selected Publication:
Laschkolnig, E.
Influence of sonication on bacterial regrowth from antibiotic loaded PMMA scaffolds
Humanmedizin; [ Diplomarbeit ] Graz Medical University; 2016. pp. 56
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- Authors Med Uni Graz:
- Advisor:
- Kühn Klaus-Dieter
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- Abstract:
- Periprosthetic joint infection (PJI) is a major complication after total joint replacement and causes additional surgery, impairment of function and high costs. For the clinical treatment of PJI, the detection of the causative bacteria growing in a biofilm attached to the implant`s surface, is crucial. Tissue samples, which have been regarded the gold standard in the diagnosis, are not able to dislodge the causative germs growing in the biofilm. Therefore additional techniques have been developed to remove the biofilm from the implant, like Dithiothreitol (DTT) or sonication. Nowadays sonication of removed prostheses to sample the surface itself is a widely spread method in the diagnostics of PJI and has shown a high sensitivity and specificity. Bone cement (PMMA) is a well established material for anchoring artificial joints to the bone and can be used in combination with antibiotics added to the cement, to prevent infections. Antibiotics, which are located on the outer surface layer, are released over a long time period, otherwise the diffusion path would be too long. But still 90% remain inside the cement. In the literature there has been some evidence that these remaining antibiotics can be released out of PMMA during sonication, what might lead to false negative sonication results during the diagnostics of PJI. In this study we analysed the effect of sonication on further antibiotic release and it’s possible influence on bacterial regrowth of biofilms attached to standardized antibiotic loaded PMMA scaffolds (Copal G+C). Therefore appropriate bacterial strains are inoculated onto standardized PMMA scaffolds with added antibiotics. We imitated the in-vivo antibiotic release of the bone cement, by storing the scaffolds for 10 days in Falcon Tubes filled with 10mL PBS, which was daily changed. Additionally we performed inhibitor tests twice during this period, to control the antibiotic release. After 10 days we added a mixture of TBS and a specific bacterial stock solution out of Staphylococcus aureus (MRSA), Enterococcus faecalis, Streptococcus sanguinis and Propionibacterium acnes to form biofilm on the scaffolds. After overnight culture we performed sonication and plated the sonication fluid on agar plates after 0, 1, 2, 4 and 8 hours and stored them under suitable conditions for 24 hours. In addition blood culture bottles were inoculated with 3mL of sonication fluid 8 hours after sonication. Positive controls with scaffolds without added antibiotics (Palacos R) and negative controls with Copal G+C PMMA scaffolds without added bacteria were done in the same way. After overnight incubation all samples of MRSA, Enterococcus faecalis and Streptococcus sanguinis showed normal bacterial re-growth without any inhibition. Also all blood culture bottles were positive the day after sonication had been performed. We could not perform sonication with Propionibacterium acnes- scaffolds, because these samples were contaminated or showed no bacterial growth after 48 hours. We can conclude from this study, that a possible antibiotic release triggered by sonication has no influence on bacterial re-growth of MRSA, Enterococcus faecalis and Streptococcus sanguinis. To make a conclusive statement about Propionibacterium acnes, further experiments are necessary.