Gram positive bacteria photoinactivation by a new synthetic porphyrin

MAMONE L; FERREYRA D; DI VENOSA G; SAENZ D; CALVO G; ROSSETTI MV; ALCIRA BATLLE; BUZZOLA F; DURANTINI E; CASAS A

Dusseldorf

Congreso; INTERNATIONAL CONGRESS ON PORPHYRINS AND PORPHYRIAS 2015; 2015

Staphylococci infections have become a major health issue due to multiple antibiotic resistances reported on these strains in recent years. The antimicrobial photodynamic therapy (APDT) appears as an alternative treatment, to which microbial cells will not be able to develop resistance. This therapeutic modality employs a molecule, called photosensitizer (PS), that is capable of generating reactive species in the presence of molecular oxygen after absorbing light. Porphyrins and their chemically modified derivatives are among the chemical species used as PSs. In this work, we studied the action of a new porphyrin: 5, 10, 15, 20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin (TAPP) as PS on S. aureus planktonic and biofilm cultures. The aliphatic spacer can provide a high mobility of the amine group, facilitating the binding to microbial cells. We evaluated TAPP toxicity in darkness and after irradiation with white light (phototoxicity). In planktonic cultures, no toxic effects in the dark were registered at concentrations lower than 5 µM TAPP. Using 2.5 µM TAPP, total eradication (8 logs of reduction in the survival fraction vs. untreated control) of microorganisms was achieved after irradiation (165 J cm-2). S. aureus biofilms were less sensitive to photoinactivation as compared to planktonic cultures. Toxicity in darkness was recorded from 30 µM TAPP onwards. Biofilm bacterial photoinactivation was achieved after irradiation (165 J cm-2) with 20 µM TAPP. Under these conditions, APDT led to a 2 logs reduction in the survival fraction. We have also observed TAPP induced phototoxicity by means of the LIVE/DEAD BacLight Bacterial Viability Kit and fluorescence confocal microscopy analysis. Our results highlight the potential use of the synthetic porphyrin TAPP-APDT against Gram positive clinical infections.