ANTIBACTERIAL ACTIVITY OF PENTA-O-GALLOYL-Β-D-GLUCOSE IN IN VITRO TESTS

INTRODUCTION: Antibiotics have innovated the treatment of bacterial infections, reducing morbidity and mortality rates. However, their indiscriminate use has led to the development of resistance mechanisms. According to the World Health Organization's Global Report on Antimicrobial Resistance and Antimicrobial Use Surveillance System, antimicrobial resistance is a public health problem and one of the top ten global health threats, with the bacteria Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus standing out. Faced with intrinsic or acquired resistance to antimicrobials, the treatment of bacterial infections has required the search for new therapies, with plants and their phytochemicals being considered as alternative agents, including Penta-O-galloyl-β-D-glucose (PGG). The aim of this study was to investigate the antibacterial activity of PGG among bacteria that cause infections in humans. METHODS: Strains of Klebsiella pneumoniae (ATCC 70063), Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923) were used, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PGG (Sigma-Aldrich®) were determined. To determine the MIC, a 96-well plate was used, with suspensions of microorganisms at 1.5 x 10⁸ CFU/mL, testing the compound in serial dilutions, starting with a concentration of 2000µg/mL. In addition to the serial dilutions, the growth and sterility control of the PGG was carried out. The plates were incubated for 24 hours in an oven at 37°C, then stained with 10 µl of resazurin, incubated in an oven at 37°C, and read after two hours. To determine the CBM, each concentration from the previous test that showed no growth was inoculated onto a 7H11 agar plate, and after 24 hours of incubation, the CBM readings were taken based on the growth of the controls, with the lowest concentration of the PGG compound that prevented bacterial growth (≥ 99.9% cell death) being considered the CBM.  RESULTS: The compound analyzed showed no antibacterial activity towards Klebsiella pneumoniae and Escherichia coli. With regard to Staphylococcus aureus, a CIM of 250µg/mL and CBM of 1000µg/mL were observed, indicating that the compound has bactericidal action. CONCLUSION: PGG shows antibacterial activity and has the potential to be used as an alternative in the treatment of bacterial infections caused by Staphylococcus aureus.