Porphyrin-apidaecin conjugate as a new broad spectrum antibacterial agent.

The conjugation of the cationic antimicrobial peptide, apidaecin Ib, to the anionic photosensitizer, 5(4'-carboxyphenyl)-10,15,20-triphenylporphyrin (cTPP), afforded a new antibacterial agent effective, under light activation, against both Gram-positive and Gram-negative bacteria. At low concentrations (1.5-15 μM) the conjugate was able to reduce the survival of Escherichia coli cells by 3-4 log10, and most notably, it resulted photoactive also against hard-to-treat Pseudomonas aeruginosa, although at higher concentration (60 μM).