(229a) Combined Treatment of Heat and Antibiotics to Mitigate Biofilms on Implanted Devices

Thousands of people in the United States each year require the removal of their implanted device due to bacterial biofilm infections. Biofilms are notoriously difficult to treat due to many reasons including changes in gene regulation, decreased diffusivity of antibiotics to the bacteria from the extracellular polymeric substance, and decreased metabolism from nutrient limitations. Infected implants typically require invasive surgery to remove the implant followed by a long-term antibiotic treatment before re-implantation can occur. The use of an in situ thermal mitigation process in combination with antibiotic treatment could mitigate the biofilm without invasive surgery. To better understand the effect of the combined treatment, Pseudomonas aeruginosa biofilms were subjected to heat shocks at from 37 to 80 °C for 1 to 30 minutes all while exposed to either ciprofloxacin, tobramycin, or erythromycin at concentrations between 0.125 and 128 µg/mL. The biofilms were exposed to antibiotics for a total of 24 hours and heat shocked 4 hours into the antibiotic exposure to demonstrate the effect of a brief heat shock integrated with sustained antibiotic treatment. Following the complete antibiotic exposure time the remaining viable colony forming units (CFU) were quantified by serial dilution and plating of the homogenized biofilm. High temperatures and exposure times were successful at completely eradicating the 10⁷ CFU biofilms on their own, however, biofilms subjected to milder heat shocks largely recovered by the end of the treatment time. The combined treatment of the heat and antibiotics proved to be synergistic in nature for a select window of temperatures and exposure times for all three antibiotics even at concentrations with no observable effect on their own. At 60 °C for 5 minutes and 70 °C for 1 minute the heat and any of the three antibiotics had multiple orders of magnitude reduction in viable bacteria with the most notable being erythromycin reducing the viable population by six orders of magnitude when neither heat nor antibiotic had an effect on their own. Through inductive heating on an implant device’s surface heat could be applied without invasive surgery. The synergic effect of heat and antibiotics could obviate thousands of surgeries and greatly improve patient quality of life.