Microbiological and biophysical characterization of the antibacterial action of the essential oil (EO) of Aloysia polystachya against gram-positive and gram-negative model bacteria.

ANAHÍ BORDÓN; RODRIGUEZ, SERGIO A.; VALERIA MATTAR TAPIA; ANDREA C. CUTRÓ; HOLLMANN, AXEL

Rosario

Congreso; L Reunión Anual Sociedad Argentina de Biofisica 2022; 2022

Sociedad Argentina de Biofísica

he presence of resistant bacteria to traditional antibiotics is a serious health problem worldwide. In this sense, the EOs have received increasing attention for their antimicrobial activity. The objective of this work was the microbiological and biophysical characterization of the antibacterial action of the EO extracted of Aloysia polystachya (Burrito) against gram-positive (S. aureus) and gram-negative (E. coli) bacteria. First, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (CBM) of the EO were determined. Although both bacteria showed the same MIC value (40µL/mL), only for E. coli CBM value was found (80µL/mL). In addition, growth and death curves were performed. In both bacteria tested, a significant reduction in microbial growth was observed at the different sub-MIC concentrations. In the death curves, it was observed that 2 x CIM of EO is able to eliminating 100% of bacteria for E. coli and 90% for S. aureus, after only 1 hour of incubation. To characterize the possible mechanisms of action, the effect of EO on the bacterial membrane in both model bacteria was evaluated. In the case of E. coli by microscopy and spectroscopy experiments, the permeabilization of both inner and outer membranes was shown. In S. aureus EO was also able to induce permeabilization of the plasmatic membrane. However, in the case of E. coli, less amount of EO was needed to achieve the same level of permeabilization evaluated by SYTO-9 and propidium iodide stain. Finally, when the effects of EO were evaluated on bacterial biofoms, the EO was able to inhibit the biofilm formation as well as to eradicate preformed biofilms in both bacteria tested but with some differences among each bacteria. It can be concluded that EO has antibacterial activity against planktonic bacteria and biofilm of both bacteria studied. Regarding the mechanism of action, besides further experiments should be made, bacterial membrane seems to be one of the targets of this EO.