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Rethinking Pyogenic Flexor Tenosynovitis: Biofilm formation on Tendons and Considering New Treatment Strategies
Constantinos Ketonis, MD, PhD; Asif Ilyas, MD
Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, PA
Introduction: Pyogenic flexor tenosynovitis (PFT) of the hand remains a challenging problem that often requires surgical irrigation and antibiotics. We hypothesize that due to the tendons limited blood supply and the closed-space nature of the sheath, PFT shares many similarities to peri-prosthetic joint infections (PJI), and as such, facilitated by bacterial attachment and biofilm formation on tendons, renders standard treatments less effective. Furthermore, previous studies have demonstrated that local administration of corticosteroids in conjunction with antibiotics can improve treatment outcomes in patients with septic arthritis and in animal models of PFT. We hypothesize that the local administration of corticosteroids and antibiotics, either together or separately, can act directly on the adherent bacteria resulting in decreased colonization and biofilm formation.
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, 37ūC. 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. 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 magnifications, demonstrated bacterial colonization in grape-like clusters, typical of Staphylococcus aureus, that at higher magnifications, reveal dense colonies covered by a thick slimy veil characteristic of biofilm (Figure 1). 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 (Figure 2). These findings were further demonstrated with confocal and electron microscopy.
Conclusion: Staphylococcus aureus readily forms biofilm on human flexor tendons analogous to PJI, which may render current PTF with local irrigation less effective contributing to its typical sequale. The addition of both local antibiotics and corticosteroids resulted in considerable decrease in biofilm formation and bacterial burden on flexor tendons. 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 in combination with corticosteroids to decrease the bacterial burden and biofilm formation on flexor tendons
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