Protective role of the staphyloxanthin pigment against photoinactivation of Staphylococcus aureus.

SULIGOY M; QUIROGA, E; CASAS, A; DIAZ, R; CALVO, G; BUZZOLA, FR; SAENZ, D; SORDELLI DO

Barcelona

Congreso; 17th International Congress on Photobiology and 18th Congress of the European Society for Photobiology.; 2019

International Union of Photobiology, European Society for Photobiology

Staphylococcus aureus is the causative agent of a diverse array of acute and chronic infections. This pathogen has acquired resistance to virtually all of the antimicrobial agents available, and in recent years, the worldwide emergence of multiresistant clones in hospitals and communities has spurred significant concern. S. aureus produces a yellowish-orange pigment, named staphyloxanthin (STX), which is the product of carotenoid biosynthesis pathway. Because of the molecular structure of the pigment, STX could act as an endogen photosensitizer in photoinactivation with visible light treatment. However, STX could protect to S. aureus from the photoinactivation due to its antioxidant properties. To study the response of S. aureus mediated by STX against photoinactivation in the presence or absence of the photosensitizer toluidine blue. The Abs450 of STX extracts were as follows: SH1000 (0.4680.045), RN6390 (0.1640.096), RN6011 (0.0940.02), Sa14 (0.2050.033) and Sa14P (0.4500.123). The pigment production was similar up to 14 days of TSA plate growth. Absorption spectra of the methanolic extracts were similar between SH1000 and Sa14P strains and also between Sa14 and RN6390 respectively. For SH1000, RN6390 and Sa14, the photoinactivation mediated by toluidine blue reduced the number of viable bacteria by 4, 5 and 6 orders of magnitude respectively, as compared to non- irradiated controls. For Sa14P, the same treatment reduced 6 orders of magnitude the amount of viable bacteria. The addition of exogenous STX reduced the photoinactivation degree of RN6911 (white colonies) or SH1000 (orange colonies) to 1 order of magnitude in both strains. After photoinactivation treatment, all viable bacterial cells incubated with exogenous STX resisted the oxidative stress of H2O2, exhibiting similar number of CFU/ml as compared to the non- H2O2 treated control. In contrast, exposure to H2O2 killed the few viable bacterial cells detected after photoinactivation treatment in the absence of exogenous STX addition. The pigment STX either endogenously or exogenously protects S. aureus against photoinactivation mediated by toluidine blue. Antioxidant properties of STX could be responsible of its protective role.