Antibacterial Activity of the Pyrogallol against Staphylococcus aureus Evaluated by Optical Image

Abstract

The minimum inhibitory concentration (MIC) is used to define the lowest concentration at which a substance can inhibit bacterial growth. This study aimed to evaluate the MIC of pyrogallol against Staphylococcus aureus and to propose a method for building growth inhibition curves of bacterial strains from MIC assays. S. aureus strains 1199B (NorA) and 1199 (wild type) were used for the assays. Pyrogallol MIC tests were performed by the broth microdilution method. The proposed method uses RGB images of the microdilution plate using the R (Red), G (Green), and B (Blue) channels to extract information for the construction of the bacterial growth inhibition curve (GIC). Pyrogallol demonstrated a MIC of 512 µg/mL against the two S. aureus strains tested. The GIC was calculated and the MIC point of pyrogallol was identified against the tested strains. The proposed method suggested the same MIC point for pyrogallol when using microplate images before and after the addition of resazurin. Through this methodology, the subjectivity of visual analysis in MIC tests can be eliminated.