Protective role of the staphyloxanthin pigment against photoinactivation of Staphylococcus aureus

DIAZ R; SULIGOY M; SAENZ D; CALVO G; QUIROGA E; SORDELLI D; BUZZOLA F; CASAS A

Barcelona

Congreso; 17th International Congress on Photobiology & 18th Congress of the European Society for Photobiology:; 2019

European Society for Photobiology and International Union of Photobiology

PROTECTIVE ROLE OF THE STAPHYLOXANTHIN PIGMENT AGAINST PHOTOINACTIVATION OFSTAPHYLOCOCCUS AUREUSAuthors: Rocío Díaz2, Mauricio Suligoy2, Daniel Sáenz1, Gustavo Calvo1, Ezequiel Quiroga1, Daniel Sordelli2, FernandaBuzzola2, Adriana Casas1Presenting Author: Rocío Díaz1) Centro de Investigaciones sobre Porfirinas y Porfirias (CIPYP) CONICET-Htal de Clínicas José de San Martín - Universityof Buenos Aires, Argentina 2) Instituto de Investigaciones en Microbiología y Parasitología Médica, University of BuenosAires-CONICET, ArgentinaBackgroundStaphylococcus aureus is the causative agent of a diverse array of acute and chronic infections. This pathogen hasacquired resistance to virtually all of the antimicrobial agents available, and in recent years, the worldwide emergenceof multiresistant clones in hospitals and communities has spurred significant concern. S. aureus produces a yellowishorangepigment, named staphyloxanthin (STX), which is the product of carotenoid biosynthesis pathway. Because ofthe molecular structure of the pigment, STX could act as an endogen photosensitizer in photoinactivation with visiblelight treatment. However, STX could protect to S. aureus from the photoinactivation due to its antioxidant properties.ObjectiveTo study the response of S. aureus to photoinactivation treatment mediated by toluidine blue in the presence orabsence of STX.MethodsS. aureus laboratory strains SH1000, RN6390 and RN6911 and the clinical isolates Sa14 and Sa14P were employed.Methanolic extracts of the pigment from bacterial suspensions with equal optical density (OD) were quantifiedspectrophotometrically at 450 nm. To photoinactivate S. aureus, the bacterial suspensions were illuminated in thepresence of toluidine blue (50 μM) employing a non-coherent light source in the presence or absence of STX addedexogenously. Then, the viable cells were quantified by plating an aliquot of serial dilutions on trypticase soy agar(TSA). The response to oxidative stress with H2O2 was determined immediately after photoinactivation treatment.ResultsThe 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 betweenSa14 and RN6390 respectively. For SH1000, RN6390 and Sa14, the photoinactivation mediated by toluidine bluereduced the number of viable bacteria by 4, 5 and 6 orders of magnitude respectively, as compared to non- irradiatedcontrols. For Sa14P, the same treatment reduced 6 orders of magnitude the amount of viable bacteria. The additionof 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 withexogenous 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 photoinactivationtreatment in the absence of exogenous STX addition.ConclusionsThe pigment STX either endogenously or exogenously protects S. aureus against photoinactivation mediated bytoluidine blue. Antioxidant properties of STX could be responsible of its protective role.