Modifying and Delivering Antimicrobials to Prevent Orthopaedic Implant Infections

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 DESCRIPTION (provided by applicant): Infections after orthopaedic surgery are catastrophic. Implants are easily colonized by bacteria, and eradication of infection often requires surgical removal of the implant, a luxury not available for patients in whom the implant provides essential structural support. These infections are also a major public health expense, costing more than $8 billion of additional spending per year. Current implant coating technologies exist that locally deliver antibiotics, attempting to prevent bacterial infection from taking hold. These methods have achieved limited translation because of i) the inability to achieve sustained release above necessary minimum inhibitory concentrations of the antibiotic, ii) the addition of an additional inert scaffolding that is itself a surface for bacterial adhesion and biofilm formation, and iii) limited effectiveness of current antibiotics against slow-growing bacterial cells that comprise biofilm-state bacteria. In order to address these issues, this proposal will investigate two conceptually innovative hypotheses that probe the relationship of host and bacteria with the provocation of novel antimicrobials (active-release antibiotic coatings and re-engineered antibiotics targeting slow-replicating bacteria) using novel diagnostic tools that coincidentally assess the infection and the host immune response to the infection: 1] dual RNA sequencing; and 2] non-invasive in vivo bioluminescent imaging. The proposal aims to develop a combination passive-active-release polymer coating that will deposit additional antibiotic when challenged by the acidic environment of periprosthetic infection. This implant coating will be impregnated with i) commonly used antibiotics as well as ii) a novel, re-engineered antibiotic that specifically targets the senescent bacteria that comprise biofilms. These implants will be employed in a novel in vivo mouse model of implant infection 1] to assess efficacy and 2] in sub-inhibitory and inhibitory antibiotic doses to provoke a transcriptomic response from host PMNs and bacteria. Finally, coatings developed in the proposal will be assessed for biocompatibility using techniques of osseointegration analysis. Taken together, this proposal will capitalize on existing institutional infrastructure and human capital to undertake novel, coincidental and interdependent host immune cell: bacterium imaging and deep RNA sequencing technologies to investigate host immune and infecting bacterial responses to antimicrobials. If successful, this project will i) set the stage for longitudinal studies of PMN: bacteria interaction with other strans of bacteria, ii) provide a basis for large animal pre-clinical studies of a novel coating and novel antimicrobial agent, and iii) broaden our understanding of bacterial and host response to antibiotics, laying the groundwork for future antimicrobial therapies.