New research from Switzerland has delved into the much-utilized antibiotic, vancomycin. Dr. Fintan Moriarity is manager of Musculoskeletal Infection at the AO Research Institute Davos. Dr. Moriarity was a co-author on a recent study entitled, “Vancomycin displays time-dependent eradication of mature Staphylococcus aureus biofilms,” which appears online in the February 2017 edition of the Journal of Orthopaedic Research.
Vancomycin: Concentration and Duration Matter
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The authors write, “The aim of this study was to identify the minimum concentration and duration required for vancomycin-mediated eradication of in vitro Staphylococcus aureus biofilm from titanium-7% aluminium-6% niobium (TAN) discs, a common implant metal.”
Dr. Moriarity told OTW, “We have been actively pursuing antimicrobial strategies for orthopaedic device associated infections for some years now. One question we never fully understood was how much antibiotic we actually needed to deliver to predictably treat an infection. We know that bacteria are resistant to antimicrobials when growing as a biofilm, but we did not have any metrics on the scale of this increased resistance in terms of concentrations or durations. If we are ever to develop antimicrobial strategies that can predictably treat an established infection, this information is crucial. The key point was working with existing techniques to answer a new question that had not been asked in exactly this way in the past.”
The authors wrote, “Firstly, under static conditions, complete eradication of S. aureus biofilm can be achieved by vancomycin alone. Secondly, biofilm eradication was not possible under conditions of fluid flow.”
Dr. Moriarity commented to OTW, “We were surprised to learn that actually achieving super-high concentrations of vancomycin did not improve its killing activity. Many of the currently available materials for local antibiotic delivery achieve very high concentrations of antibiotic locally for a short period of time. Our data showed us that these super high concentrations do not provide any measurable benefit in terms of bacterial killing. What we need to do is to extend our duration of antibiotic exposure, and that we can achieve a good outcome even with comparatively low antibiotic concentrations.”
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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