A novel bacteria-specific pro-photosensitizer

Abstract This proposal aims to explore the innovative potential of a new bacteria-specific “pro-photosensitizer” (pro- PS) in combatting multidrug-resistant (MDR) bacteria found in open and chronic wounds. As antibiotic resistance poses a growing threat to the already overburdened U.S. healthcare system, the search for non- antibiotic treatments and combination therapies to address MDR microbes has become a top priority. We recently showed robust and synergistic microbicidal activity by combining 405 nm blue light (BL) with phytochemical carvacrol or thymol. The combinatory treatment killed MDR bacterial species commonly seen in hospital-acquired infections as high as 7.0 CFU log10 within 30 min, including Acinetobacter baumannii (Ab), Pseudomonas aeruginosa (Pa), and methicillin-resistant Staphylococcus aureus (MRSA), which was demonstrated in planktonic culture and biofilms, both in vitro and in vivo, for standard strains and clinical isolates, irrespective of antibiotic susceptibility. In this proposal, we will broaden the killing to the BL- refractory family Enterobacterales such as Escherichia coli (E. coli) and Klebsiella pneumoniae (Kp), which are commonly responsible for hospital-acquired infections and often co-infecting with BL-susceptible pathogens above. They are also listed as an urgent or serious threat by CDC. These species are not sensitive to BL-mediated bactericides owing to their relatively low levels of biosynthetic porphyrins that act as endogenous photosensitizers. To target this issue specifically, we will search for bacteria-specific intermediates capable of increasing porphyrin biosynthesis exclusively in bacteria, thereby sensitizing the BL-refractory pathogens to BL-medicated bactericides. The potential intermediate will undergo scrutiny for its selectivity, safety, antibiotic potentiation, and efficacy in killing standard and clinical isolates of E. coli and Kp in pairing BL. Moreover, the combinatory modality will be combined with red light and antibiotics to address deep-seated infections. Possible resistance will be also assessed. Aim 2 will validate the efficiency of the bacteria-specific phototherapy in eliminating superficial and deep-seated biofilms in open wounds of ex vivo porcine skin and in mice. Due to the increased porphyrin production, the bacteria- specific intermediate will be also evaluated for its potential as a novel theranostic agent capable of enhancing killing and real-time detection of bacterial biofilm infections by a cellphone. Over the years, numerous photosensitizers have been developed for photodynamic therapy (PDT), but none of them are bacteria-specific. The discovery of a bacteria-specific pro-PS marks a paradigm shift in the treatment of MDR pathogens, offering distinct advantages in terms of safety, specificity, and efficacy over conventional PDT.