Oxidative stress in Staphylococcus aureus as a mechanism of action of silver nanoparticles phytosynthesized with Bothriochloa laguroides.

TORANZO, ARACELI; LUCERO ESTRADA, CECILIA; PAEZ, PAULINA

Mendoza

Jornada; IV Reunión Conjunta de las Sociedades de Biología de la Republica Argentina.; 2020

Sociedades de Biología de la Republica Argentina

The large increase in bacterial strains resistant to currently used antibiotics emphasizes the need for new approaches to treating infections. Because silver nanoparticles (AgNPs) have demonstrated antimicrobial activity, the development of new applications in this field makes them an attractive alternative to antimicrobials. The AgNPs could generate a condition of oxidative stress in bacterial cells due to an increase in reactive oxygen species (ROS), these species are capable of causing damage at the level of bacterial macromolecules which would lead to their death. In previous works, we saw that phytosynthesized AgNPs with aqueous extract of Bothriochloa laguroides had activity against Staphylococcus aureus in both planktonic and sessile cells. The objective of this work was to determine if AgNPs phytosynthesized from the aqueous extract of B. laguroides produce oxidative stress with the consequent oxidation of macromolecules in two strains of S. aureus. The ROS were determined by using the probe 6-carboxy-2 ', 7'-dichlorodihydrofluorescein diacetate-diacetoxymethyl ester (H2-DCFDA), the oxidation of lipids was determined by a colorimetric technique that uses thiobarbituric acid which reacts with aldehydes that are produced by lipid peroxidation, protein oxidation was quantified by a colorimetric technique that involves the use of potassium iodide which reacts with oxidized proteins. All these determinations were carried out at different times (0, 1, 2 and 3 h) both for the untreated strains (control) and for those treated with different concentrations of AgNPs. For the S. aureus strain 43300 (methicillin-resistant) the increase in ROS with respect to the control was seen since 1 h incubation with concentrationsof AgNPs equivalent to the MIC and the supraMIC. Regarding the S. aureus strain 29213 (methicillin- sensitive), the increase at MIC and supraMIC concentrations was also seen at the time of incubation, reaching a maximum at 3 h. Strain 43300 treated with MIC and supraMIC of AgNPs showed an increase in protein oxidation from the hour of incubation, this increase was greater at supraMIC concentrations, the increase was maintained until 3 h of incubation. In strain 29213, the same behavior was observed as in strain 43300. The highest oxidation of lipids in both strains was observed at 3h of incubation with a concentration of AgNPs higher than the MIC. In this work, it was shown that AgNPs are capable of producing oxidation of bacterial macromolecules, which could be the cause of their antibacterial activity.