Dispersion Inhibits Thermal Mitigation of Pseudomonas aeruginosa Biofilms on Self-Heating Surfaces

Bacterial biofilms on medical implants are a major problem, typically requiring explantation and replacement of the biofilm-colonized implant. Thermal mitigation of these biofilms in situ has shown great promise in the laboratory, where the thermal shock can be most precisely delivered by immersion in hot media. Clinical implementation requires delivering the shock from the implant surface, however, leaving the surroundings at a cooler temperature. This study hypothesized that bacteria may rapidly, reversibly disperse into the cooler surroundings to partially evade the shock and tested this hypothesis by thermally shocking Pseudomonas aeruginosa biofilms on thermoelectric devices under media with different heat sink conditions. The time scale and equilibrium constant of this dispersion were investigated in ambient temperature immersion studies, and the effect of thermal shock on bacterial dispersion rate was investigated in a flow cell using biofilms grown on thermoelectric devices. The results showed that biofilms equilibrate with surrounding media in seconds, that a small fraction of bacteria in the biofilm are much less prone to dispersion, that thermal shock triggers an immediate increase in dispersion, and that shocking biofilms via their substrate in cooler surrounding decreases shock efficacy compared to shocks where the surrounding's temperature approaches that of the substrate.