Photodynamic Inactivation of Staphyloccus Aureus Biofilms by Carboxypterin

MIÑÁN, A; LORENTE, C; THOMAS, A; FERNANDEZ LORENZO DE MELE, M; SCHILARDI, P

Congreso; 16th International Congress on Photobiology; 2014

International Union of Photobiology

Staphylococcus aureus is a major cause of acquired nosocomial infections in surgical wounds and in those infections associated with indwelling medical devices [1]. Due to the development of multiresistant S. aureus strains that produce many therapeutic complications it is vital to design novel strategies for the treatment of these infections. Photodynamic inactivation (PDI) of bacteria has recently emerged as a promising and innovative approach for the erradication of pathogenic microorganisms [2]. The aim of this study was to evaluate the antibacterial photodinamic properties of carboxipterin (Cap) against S. aureus growing both as planktonic and as biofilms, since it is well known that biofilms are highly tolerant to antimicrobial agents. Planktonic and sessile bacteria were challenged in vitro with Cap (0,1 - 200 M) and UV-A radiation for 2 h at 28 ºC showing antimicrobial activity. The MBC (minimal bacterial concentration) of Cap was 0.1 M for irradiated planktonics cells, and a reduction of the bacterial viability, at least 5 orders of magnitude compared with the initial inocula, was found. Biofilms of S. aureus were grown in microtiters plates. After PDI treatment with 50 M of Cap the number of viable sessile cells was 3 orders of magnitude smaller than the control. The comparison of the MBC values for planktonic and sessile cells shows that sessile bacteria exhibited an increased resistance to PDI (near 500-fold). However, Cap at concentrations as low as 50 M has bactericidal activity on S. aureus biofilms. These results encourage further investigation on the potential use of PDI based on Cap for the treatment of localized infections.