Activity-based probes for targeted imaging and treatment of bacterial otitis media

PROJECT SUMMARY Otitis media (OM), or infection of the middle ear, is the one of most common illnesses diagnosed in children in the United States and is the leading reason for pediatric antibiotic prescriptions. Acute OM is most commonly caused by the bacteria Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus, while Pseudomonas aeruginosa is the most common cause of chronic OM. Diagnosis of OM currently relies on otoscopy, which has low sensitivity and specificity and is unable to differentiate bacterial infection from other causes of inflammation. These limitations result in over-diagnosis and over- prescription of antibiotics, contributing to increased antimicrobial resistance (AMR) and subsequent treatment failures. Therefore, there is a significant unmet need for improved diagnostic tools for OM that can enable faster and more effective treatment decisions and reduce the potential for AMR development. Photodynamic therapy (PDT), is a promising antimicrobial treatment option in which light-activated photosensitizers induce cell killing. However, prior applications of PDT to bacteria have been untargeted or used non-covalent methods of targeting, raising the risks of off-target toxicity and resistance development. Covalent targeting of enzyme active sites has the potential to address these current shortcomings and result in probes capable of both imaging and treatment applications. The overall objective of this proposal is to engineer a covalent theranostic probe targeting bacterial D,D-carboxypeptidases (DD-CPases) as a novel tool for imaging and treating bacterial OM using PDT. All five common OM-causing bacteria have a DD-CPase and humans lack homologs. Therefore, the primary aims of this project are to: (1) develop a covalent activity-based probe (ABP) suitable for imaging and treatment of the five primary OM-causing bacteria; (2) demonstrate that a single covalent probe can be used to image and kill the five most common OM-causing bacteria in vitro, and (3) use the top probe to confirm imaging and killing of the two most common OM-causing bacteria in vivo. Success with these aims will result in a strategy for diagnosis and treatment of OM that will reduce AMR development, reduce treatment failures, and prevent progression to chronic OM and its associated complications. In addition, the training plan outlines a comprehensive strategy for career advancement for the applicant, Dr. Emily Woods, under the mentorship of the sponsor, Dr. Matthew Bogyo. Dr. Woods will engage in a variety of seminars, courses, and experiences to develop her scientific and academic skills and enable her transition to independence. Overall, the proposed studies are expected to generate a novel tool for improved diagnosis and treatment of bacterial OM.