PROJECT SUMMARY: Central line associated bloodstream infections (CLABSI), now considered a medical error, remain a significant contributor to healthcare associated infections (HAIs) and associated morbidity and mortality. Despite ongoing initiatives to adopt or adhere to specific recommendations and increased use of antibiotic impregnated catheters, the incidence trend for CLABSIs has remained flat or increasing. The underlying pathophysiology is related to biofilm formation on catheter surfaces which offer significant protection from host response and antimicrobial therapy. Thus, definitive therapy often requires removal and replacement of catheters. However, the patients at greatest risk for CLABSI (i.e., hemodialysis patients) also have high risk associated with catheter replacement owing to: limited other vascular access points; life-sustaining nature of hemodialysis; and significant co-morbidity increasing complication risk of instrumentation procedures. Our long-term goal is to develop an effective catheter salvage strategy that removes biofilms from catheters in situ in patients whose condition precludes device removal and replacement. We have found that modest elevations in temperature: (1) soften biofilms, making them more likely to be mechanically dispersed; (2) reduce the total biomass from a surface; and (3) augment antibiotic killing of constituent bacteria within a biofilm. Our preliminary data also show that biomass dispersed by heat retains significant viability that can be completely mitigated by traditional antibiotics. In a proof-of-principle experiment, we have shown that in-and-out cycling of a heated perfusate reduces catheter-adhered biomass in a rat model of CLABSI. This work suggests that the application of heat in conjunction with antibiotics is a promising catheter-salvage treatment strategy that could be quickly translated to clinical practice. The objective of this study is to optimize the treatment parameters for the application of heat and antibiotics for in situ CLABSI therapy in preparation for phase 1 human clinical trials. We hypothesize that the addition of heat in combination with catheter lock and system antibiotics will reduce bacterial load on the catheter and systemic dissemination. Our aims are to: (1) Determine the dose and duration of heat therapy that maximizes biofilm dispersal and minimizes thermal injury; (2) Define a generalizable description of the heat delivery required for biofilm eradication to allow translation from the rat to the human setting; and (3) Determine the appropriate antibiotic regimen to be used in combination with the heat therapy developed in Aim 1. Completion of these aims will provide a robust description of the heat flux required to achieve biofilm eradication without thermal injury and the parameters required to administer that treatment in a human dialysis catheter infection application. These parameters will form the basis for future phase 1 clinical testing.