335 - Using high temperatures to eradicate prosthetic joint associated biofilms on metal implants using alternating magnetic field: Efficacy and safety implications

Background: Prosthetic joint infection (PJI) is a significant complication of modern arthroplasty. Revision surgery is frequently required due to the formation pf biofilm. The presence of biofilm makes non surgical treatment difficult in part because traditional antibiotics are unable to penetrate this structure. 

We have developed a noninvasive way to eradicate biofilm off the outer surface of metal implant utilizing alternating magnetic fields (AMF). AMF creates focused surface heating on metal lic implants and can be delivered in a fashion spares significant heating of surrounding tissue. The study was to determine efficacy and safety of AMF when combined with traditional antibiotics in animal models of implant infection.

Methods: Pseudomonas aeruginosa (PA) and staphylococcus aureus (SA) were grown individually on stainless steel ball that were implanted into the thigh muscle of the mice. Mice placed in a custom built solenoid coil for AMF treatments. AMD exposures generating peak temperature of 80 or 65 C on the implant were delivered once a day. Treatment groups included AMF alone, antibiotic alone, and combination therapy. Antibiotics tested included ciprofloxacin, ceftraixone and rifampin.  Residual biofilm was measured by CFU counts. Histopathology was analyzed to determine area of damage in response to AMF treatment.

Results: Combination of a single AMF pulse with antibiotics lead to a greater biofilm reduction than either treatment alone. PA with AMD (80 C peak) and ciprofloxacin resulted in >2 log reduction of biofilm (p< 0.0001) compared to minimal reduction (AMF or ciprofloxacin alone) at Day 4. Similar treatment outcome was seen with SA and ceftraixone with combination treatment resulting on multi log reduction. Combined treatment effects were seen at lower temperatures (65 C). Histopathologic analysis demonstrates a small area of tissue damage at the end of treatment (Day 4). In mice that were survived fro additional 28-days after the final treatment, the tissue showed no signs of damage.

Conclusion: AMF combined with antibiotics leads to enhanced reduction of biofilm on metallic implants in vivo. This non invasive approach to eradicating biofilm could serve as a new paradigm in treating these challenging infections.