Each year in the United States thousands of people have medical implants removed due to bacterial biofilm infections obtained during implantation. These biofilms are notoriously difficult to treat for a variety of reasons, including transport resistance from the extracellular polymeric substance, changes in gene regulation, and decreased metabolism from nutrient limitations. Despite decades of work on antifouling surfaces and antimicrobial agents, these infections typically require invasive explantation and re-implantation surgeries coupled with long-term antibiotic treatments. One promising new approach to address this problem is in situ thermal mitigation. In this study, Pseudomonas aeruginosa biofilms were subjected to temperature shocks at 50°C, 60°C, 70°C, and 80°C with controls run at 37°C for an exposure times of 1, 2, 5, 10, 15, 20, and 30 minutes. To guarantee instant, uniform thermal exposure these shocks were performed by immersion and removal from pre-heated wells, though our lab is currently developing magnetic/polymer composite coatings which can supply the thermal shock using an externally applied magnetic field. Following thermal shock, the remaining viable colony forming units (CFU) were quantified by serial dilution and plating of the homogenized biofilm. The resulting bacterial load in CFU/cm2 fit the following equation:
log(CFU/cm2) = log(CFU/cm2)0 – [0.079 + 0.044 log(t)] * (T – 37)
where log(CFU/cm2)0 is the initial bacterial load, t is the exposure time, and T is the thermal shock temperature. However, biofilms cultured under different conditions showed a difference in susceptibility to the heating, indicating that different areas of the body could lead to different needs for successful treatment. This work is the first step in a new approach to the goal of eliminating a major liability of implanted medical devices and the billions of dollars spent on explantation, recovery, and re-implantation.
See more of this Group/Topical: Topical Conference: Chemical Engineers in Medicine