Gram positive bacteria photoinactivation by a new synthetic porphyrin

MAMONE L; DURANTINI E.; BATLLE A; CASAS A

Dusseldorf

Congreso; International Congress on Porphyrins and Porphyrias.; 2015

Staphylococci infections have become a major healthissue due to multiple antibiotic resistances reported on these strains inrecent years.The antimicrobial photodynamic therapy (APDT) appearsas an alternative treatment, to which microbial cells will not be able todevelop resistance. This therapeutic modality employs a molecule, calledphotosensitizer (PS), that is capable of generating reactive species in thepresence of molecular oxygen after absorbing light. Porphyrins and theirchemically modified derivatives are among the chemical species used as PSs.In this work, we studied the action of a newporphyrin:  5, 10, 15, 20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin(TAPP) as PS on S. aureus planktonicand biofilm cultures. The aliphatic spacer can provide a high mobility of theamine group, facilitating the binding to microbial cells.We evaluated TAPP toxicity in darkness and afterirradiation with white light (phototoxicity). In planktonic cultures, no toxiceffects in the dark were registered at concentrations lower than 5 µM TAPP.  Using 2.5 µM TAPP, total eradication (8 logsof reduction in the survival fraction vs. untreated control) of microorganismswas achieved after irradiation (165 J cm-2). S. aureus biofilms were less sensitive to photoinactivation ascompared to planktonic cultures. Toxicity in darkness was recorded from 30 µMTAPP onwards. Biofilm bacterial photoinactivation was achieved afterirradiation (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 bymeans 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 Grampositive clinical infections.