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Rethinking Pyogenic Flexor Tenosynovitis: Biofilm Formation on Tendons and New Treatment Strategies
Constantinos Ketonis, MD, PhD; Noreen Hickok, PhD; Asif Ilyas, MD
Thomas Jefferson University, Philadelphia, PA

Introduction: Pyogenic flexor tenosynovitis (PFT) of the hand remains a challenging problem that often requires surgical irrigation and parenteral or oral antibiotics. We hypothesize that the pathophysiology and microenvironment of PFT can be likened to that of periprosthetic joint infections (PJI), where bacteria thrive in a closed synovial space with limited blood supply. As such, we postulate that PFT is also facilitated by bacterial attachment and biofilm formation rendering standard treatments less effective. In this study, we evaluate infected tendons for the presence of biofilm and explore new treatment strategies, comparing corticosteroids in conjunction with antibiotics together or separately, as well as ultrasonication in their efficacy in eliminating bacterial colonization.

Methods: Fresh human cadaveric hand tendons were harvested and divided into 0.5cm segments. Samples were sterilized and inoculated with 1x104 cfu/ml Green Fluorescent Staphylococcus Aureus (GFP-SA) for 48hrs, 37?C. After saline washing to rid planktonic bacteria, samples were treated for 24 hours with: 1) Saline irrigation 2) antibiotics (Vancomycin), 3) corticosteroids, 4) Antibiotics/corticosteroid combined or 5) Ultrasonication in the presence of antibiotics. Samples were visualized using Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy (SEM), or sonicated, plated and counted. Three samples were plated from each condition and counts were expressed as means SE.

Results: Following bacterial challenge, CLSM revealed heterogeneous green fluorescence representing bacterial attachment with dense areas of signal, typical of biofilm formation. SEM at >3000X, demonstrated bacterial colonization in grape-like clusters that at higher magnifications, appear as colonies covered by a thick matrix characteristic of biofilm. Next we examined the efficacy of various treatments in decreasing bacterial load by direct colony counting. Irrigation with saline alone yielded a 18.5% decrease in bacteria burden as compared to 42.6% with steroids, 54.4% with antibiotics, and 77.3% with antibiotics/steroids combined. Adding ultrasonication eliminated any remaining bacteria. These findings were further demonstrated with confocal and electron microscopy.

Conclusions: To the best of our knowledge, this is the first study that demonstrates that Staphylococcus aureus can readily form biofilm on human tendons. This may render current PTF treatments less effective contributing to its typical sequale. The addition of both local antibiotics and corticosteroids results in considerable decrease in biofilm formation on flexor tendons while treatment with ultrasonication almost eliminates bacterial burden. We suggest re-thinking the current treatment of PFT and recommend considering a strategy more analogous to PJI management with the adjunctive use of local antibiotics, corticosteroids and mechanical agitation.

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