Cuantificación de la actividad antibacteriana de aceites esenciales frente a Escherichia coli ATCCC 25922 y Escherichia coli portadora de betalactamasas de espectro extendido

Abstract

Antibiotic resistance due to the production of the extended-spectrum β-lactamases (ESBL) by Escherichia coli has become a threat to public health. For this reason, the use of essential oils (EOs) is considered a new therapeutic alternative to counteract this problem. The most widely used method to determine the antimicrobial activity of EOs is the plate microdilution technique, which allows to determinate the inhibitory concentration (IC) at 50 % and 90 %, from the measurement of turbidity in a microplate reader. However, this generates a high margin of error in bacterial quantification, which is why it is recommended to use cell viability indicators such as 3- (4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and resazurin. In the present study, the antibacterial activity (IC 50 % and IC 90 %) of nine EOs against E. coli ATCC 25922 and ESBL-producing E. coli was evaluated with the microdilution technique using indicators such as MTT and resazurin in order to analyzewhich indicator is ideal for the quantification of the activity. Commercial EOs from Cinnamon cassia, Citrus limonum, Mentha spicata, Pogostemon cablin, Cymbopogonflexuosos and EOs obtained from the hydrodistillation of Clinopodium nubigenum, Aloysia citriodora, Pimpinella anisum and Zingiber officinale were used. Essential oils from A. citriodora, M. spicata, C. cassia, Z. officinale, C. flexuosos and C. nubigenum were estimated to have antibacterial activity against E. coli ATCC 25922and ESBL-producing E. coli, different to C. limonum, P. cablin and P. anisum. In addition, it was determined that the technique using MTT at a wavelength of 450 nm presents a lower percentage of coefficient of variation than resazurin at a wavelength of 560 to 590 nm.