Estandarización del método de bioautografía directa como estrategia para la evaluación de extractos naturales como antimicrobianos frente a Escherichia coli y Staphylococcus aureus

Abstract

Direct bioautography is a fast and simple method that has the advantage of detecting antimicrobial activity on chromatographic plates, allowing us to directly observe the fractions showing such activity. The present work consisted of the standardization of the direct bioautography method, by using both, polar and nonpolar plant extracts, with antimicrobial activity against Escherichia coli and Staphylococcus aureus. In addition, for thin layer chromatography (TLC), eluents were used according to the polarity of the plant extracts, which in turn were also compatible with the antibiotics gentamicin and ampicillin, used as positive controls. By means of this technique, it was possible to observe the growth of S. aureus in the TLC plates, however, after several tests, it was not possible to visualize the E. coli growth, therefore, it was decided to implement the bioautography method by immersion or coating, obtaining as a result the growth of both, bacteria and the visualization of the inhibition zones for the antibiotics and certain extracts by means of the use of MTT and resazurin. However, due to the instability of this method because of the different variables that must be controlled, the objective of standardizing bioautography as a tool for evaluating the antibacterial potential of natural extracts was not achieved.