Assessment of Bacteriophage Pharmacokinetic Parameters After Intra-Articular Delivery in a Rat Prosthetic Joint Infection Model

Prosthetic joint infections (PJIs) are a serious complication of orthopedic surgery. Bacteriophage (phage) therapy shows promise as an adjunctive treatment but requires further study, particularly in its pharmacokinetics. Consequently, we performed a pharmacokinetic assessment of phage therapy for PJIs using a <i>Staphylococcus epidermidis</i> Kirschner wire-based prosthesis rat model. We used 52 male Sprague-Dawley rats in four groups: negative controls (no phage, sterile implant), PJI controls (bacteria, no phage), sterile phage (phages given, sterile implant), and PJI (bacteria, phages given). The PJI groups were inoculated with ~10⁶ CFU of <i>S. epidermidis</i>. The groups receiving phage were intra-articularly injected with ~10⁸ PFU of vB_SepM_Alex five days post-implantation. The rats were euthanized between 30 min and 48 h post-injection. The measured phage concentrations between the PJI rats and the sterile controls in periarticular tissues were not significantly different. In a noncompartmental pharmacokinetic analysis, the estimated phage half-lives were under 6 h (combined: 3.73 [IQR, 1.45, 10.07]). The maximum phage concentrations were reached within 2 h after administration (combined: 0.75 [0.50, 1.75]). The estimated phage mean residence time was approximately three hours (combined: 3.04 [1.44, 4.19]). Our study provides a preliminary set of pharmacokinetic parameters that can inform future phage dosing studies and animal models of phage therapy for PJIs.