Oxospirochlorins as new promising photosensitizers against priority pathogens

Chlorins belong to a group of photosensitizers that are significant and promising for photodynamic therapy (PDT). The newly synthesized oxospirochlorins presented in this study revealed an outstanding ability to generate singlet oxygen and high photostability. The obtained porphyrinoids were incorporated into liposomes, and then their antimicrobial activity against priority pathogens: MRSA, E. coli (ESBL+), and fluconazole-resistant C. albicans was examined. The excellent activity against both Gram-positive and Gram-negative bacteria was observed. Moreover, the synergism between sublethal antibacterial PDT and antibiotics with limited efficacy against resistant strains was investigated. As a result of the photodynamic activity of chlorins, it was possible to partially restore the sensitivity of bacteria to antibiotics from the group of cephalosporins and carbapenems.