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

BORDON, ANAHI; RODRIGUEZ, SA; TAPIA MATTAR, V; CUTRO AC; HOLLMANN, A

Rosario

Congreso; L Reunión Anual SAB; 2022

Sociedad Argentina de Biofisica

The presence of resistant bacteria to traditional antibiotics is a serious health problemworldwide. In this sense, essential oils (EOs) have received increasing attention for theirantimicrobial activity. The objective of this work was the microbiological and biophysicalcharacterization of the antibacterial action of the EO extracted from Aloysia polystachya(Burrito) against gram-positive (S. aureus) and gram-negative (E. coli) bacteria. First, theminimum 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 E. coli CBM value was found (80μL/mL). In addition, growth and deathcurves were performed. In both bacteria tested, a significant reduction in microbialgrowth was observed at the different sub-MIC concentrations. In the death curves, it wasobserved that 2 x CIM of EO can eliminate 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 thecase of E. coli by microscopy and spectroscopy experiments, the permeabilization of bothinner and outer membranes was shown. In S. aureus EO was also able to inducepermeabilization of the plasmatic membrane. However, in the case of E. coli, less amountof EO was needed to achieve the same level of permeabilization evaluated by SYTO-9 andpropidium iodide stain. Finally, when the effects of EO were evaluated on bacterialbiofilms, the EO was able to inhibit the biofilm formation as well as eradicate preformedbiofilms in both bacteria tested but with some differences among each bacteria. It can beconcluded that EO has antibacterial activity against planktonic bacteria and biofilms ofboth bacteria studied. Regarding the mechanism of action, further experiments should bemade, however, bacterial membrane seems to be one of the targets of this EO.